biological molecules and the whole of cells

Question 1

Cytochrome c is a protein used in the reactions of respiration and is found across species of animals, plants and unicellular organisms

Suggest why the widespread occurrence of cytochrome c is considered to be evidence for evolution?

Answer 1

Cytochrome c is a protein used in the reactions of respiration and is found across species of animals, plants and unicellular organisms

Suggest why the widespread occurrence of cytochrome c is considered to be evidence for evolution?

Cytochrome c is present in the cells of a wide variety of organisms, suggesting that they could all have descended from a common ancestor

Question 2

a) . What is a polymer

b) . What is a monomer

Answer 2

a). What is a polymer

A large, complex molecule composed of many monomers joined together

b). What is a monomer

A small, basic molecular unit that can form a polymer

Question 3

Give two examples of monomers

Answer 3

Give two examples of monomers

Monosaccharides, nucleotides and amino acids

Question 4

Explain what happens in a condensation reaction between two monomers

Answer 4

Explain what happens in a condensation reaction between two monomers

A chemical bond is formed between the monomers and a molecule of water is released

Question 5

Describe how you would test a piece of food for the presence of lipid

Answer 5

Describe how you would test a piece of food for the presence of lipid

1. Dissolve in alcohol, then add water;
2. White emulsion shows presence of lipid.

Question 6

Suggest one advantage of the different percentage of cholesterol in red blood cells compared with cells lining the ileum

Answer 6

Suggest one advantage of the different percentage of cholesterol in red blood cells compared with cells lining the ileum

Red blood cells free in blood

Question 7

E. coli has no cholesterol in its cell-surface membrane. Despite this, the cell maintains a constant shape. Explain why.

Answer 7

E. coli has no cholesterol in its cell-surface membrane. Despite this, the cell maintains a constant shape. Explain why.

Cell unable to change shape Because cell has a cell wall and the Wall is rigid

Question 8

Explain the difference in the structure of the starch molecule and the cellulose molecule

Answer 8

Explain the difference in the structure of the starch molecule and the cellulose molecule

Starch formed from α-glucose but cellulose formed from β-glucose;

Question 9

Starch molecules and cellulose molecules have different functions in plant cells.
Each molecule is adapted for its function.
Explain one way in which starch molecules are adapted for their function in plant cells.

Answer 9

Starch molecules and cellulose molecules have different functions in plant cells.
Each molecule is adapted for its function.
Explain one way in which starch molecules are adapted for their function in plant cells.

Insoluble so doesn’t affect water potential

Compact

Large molecule; Cannot leave cell.

Question 10

Explain how cellulose molecules are adapted for their function in plant cell

Answer 10

Explain how cellulose molecules are adapted for their function in plant cell

Long and straight chains become linked together by many hydrogen bonds to form fibrils which Provides strength (to cell wall).

Question 11

Messenger RNA (mRNA) is used during translation to form polypeptides. Describe how mRNA is produced in the nucleus

Answer 11

Messenger RNA (mRNA) is used during translation to form polypeptides. Describe how mRNA is produced in the nucleus

Helicase; breaks down hydrogen bonds
Only one DNA strand acts as template;
RNA nucleotides attracted to exposed bases; Attraction according to base pairing rule;
RNA polymerase joins (RNA) nucleotides together;
Pre-mRNA spliced to remove introns

Question 12

Describe the structure of proteins.

Answer 12

Describe the structure of proteins.

Polymer of amino acids
Joined by peptide bonds;
Formed by condensation;
Primary structure is order of amino acids;
Secondary structure is folding of polypeptide chain due to hydrogen
bonding;
Tertiary structure is 3-D folding due to hydrogen bonding and ionic / disulfide bonds;
Quaternary structure is two or more polypeptide chains

Question 13

Describe how proteins are digested in the human gut

Answer 13

Describe how proteins are digested in the human gut

hydrolysis of peptide bonds;
Endopeptidases break polypeptides into smaller peptide chains; Exopeptidases remove terminal amino acids;
Dipeptidases hydrolyse / break down dipeptides into amino acids

Question 14

A student investigated the effect of chewing on the digestion of starch in cooked wheat.
He devised a laboratory model of starch digestion in the human gut.

1. Volunteers chewed cooked wheat for a set time. The wheat had been cooked in boiling water.
2. This chewed wheat was mixed with water, hydrochloric acid and a protein-digesting enzyme and left at 37 °C for 30 minutes.
3. A buffer was then added to bring the pH to 6.0 and pancreatic amylase was added. This mixture was then left at 37 °C for 120 minutes.
4. Samples of the mixture were removed at 0, 10, 20, 40, 60 and 120 minutes, and the concentration of reducing sugar in each sample was measured.
5. Control experiments were carried out using cooked wheat that had been chopped up in a blender, not chewed.

(a) What reducing sugar, or sugars, would you expect to be produced during chewing? Give a reason for your answer.
(b) In this model of digestion in the human gut, what other enzyme is required for the complete digestion of starch
(c) What was the purpose of step 2, in which samples were mixed with water, hydrochloric acid and pepsin?

(d) in the control experiments, cooked wheat was chopped up to copy the effect of chewing.
Suggest a more appropriate control experiment. Explain your suggestion

Answer 14

A student investigated the effect of chewing on the digestion of starch in cooked wheat.
He devised a laboratory model of starch digestion in the human gut.

1. Volunteers chewed cooked wheat for a set time. The wheat had been cooked in boiling water.
2. This chewed wheat was mixed with water, hydrochloric acid and a protein-digesting enzyme and left at 37 °C for 30 minutes.
3. A buffer was then added to bring the pH to 6.0 and pancreatic amylase was added. This mixture was then left at 37 °C for 120 minutes.
4. Samples of the mixture were removed at 0, 10, 20, 40, 60 and 120 minutes, and the concentration of reducing sugar in each sample was measured.
5. Control experiments were carried out using cooked wheat that had been chopped up in a blender, not chewed.

(a) What reducing sugar, or sugars, would you expect to be produced during chewing? Give a reason for your answer.

• Maltose
• Salivary amylase breaks down starch.

(b) In this model of digestion in the human gut, what other enzyme is required for the complete digestion of starch

Maltase

(c) What was the purpose of step 2, in which samples were mixed with water, hydrochloric acid and pepsin?

Mimics effect of stomach

(d) in the control experiments, cooked wheat was chopped up to copy the effect of chewing.
Suggest a more appropriate control experiment. Explain your suggestion

• Add boiled saliva
• Everything the sameAs the experiment but salivary amylase denatures

Question 15

C is a protein with a carbohydrate attached to it. This carbohydrate is formed by joining monosaccharides together. Name the type of reaction that joins monosaccharides together.

Answer 15

Condensation

Question 16

Some cells lining the bronchi of the lungs secrete large amounts of mucus. Mucus contains protein.
Name one organelle that you would expect to find in large numbers in a mucus-secreting cell and describe its role in the production of mucus.

Organelle …

Description of role …

Answer 16

Some cells lining the bronchi of the lungs secrete large amounts of mucus. Mucus contains protein.
Name one organelle that you would expect to find in large numbers in a mucus-secreting cell and describe its role in the production of mucus.

Organelle

Golgi (apparatus)

Description of role

2. Package / process proteins;

Question 17

Draw the disaccharide that would be formed from a condensation reaction between:

a) . alpha glucose and galactose
b) . alpha glucose and fructose

Answer 17

Draw the disaccharide that would be formed from a condensation reaction between:

a) . alpha glucose and galactose
b) . alpha glucose and fructose

Question 18

Draw the structure of the beta glucose

Answer 18

Draw the structure of the beta glucose

Question 19

a) What is the name of the bond that forms between two monosaccharides
b) what molecule is released during a condensation reaction between two monosaccharides

Answer 19

a) What is the name of the bond that forms between two monosaccharides

Glycosidic

b) what molecule is released during a condensation reaction between two monosaccharides

Water

Question 20

Which monosaccharides make up the disaccharides:

maltose sucrose and lactose

Answer 20

Which monosaccharides make up the disaccharides:

maltose sucrose and lactose

a-glucose + fructose —> sucrose

a-glucose + galactose —> lactose

a-glucose + a-glucose —> maltose

Question 21

Describe how to test for reducing sugars and say what a positive and negative result would look like

Answer 21

Describe how to test for reducing sugars and say what a positive and negative result would look like

Add Benedicks reagent to a test sample and heat it in a water bath that’s been brought to the boil.
look at the colour of the sample for the result.
a positive result would be a coloured precipitate (green, orange, yellow or brick red, depending on the concentration of the reducing sugar) and a negative result would be blue.

Question 22

Why is starch good for storage

Answer 22

Why is starch good for storage

It doesn’t affect water potential so it doesn’t cause water to enter cells by osmosis which would make them swell

Question 23

Explain an advantage of amylopectin that makes it suitable for energy storage

Answer 23

Explain an advantage of amylopectin that makes it suitable for energy storage

It has lots of side branches which means the enzymes that break amylopectin down can get to the Glycosidic bonds easily which means that glucose can be released quickly when it is needed

Question 24

Which polysaccharide in starch is the major component of plant cell walls

Answer 24

Which polysaccharide in starch is the major component of plant cell walls

Cellulose

Question 25

Describe the structure of the polysaccharide cellulose and explain how it structure makes it suited to its function in cell walls

Answer 25

Describe the structure of the polysaccharide cellulose and explain how it structure makes it suited to its function in cell walls

Celulose is made from long unbranched chains of beta glucose these are joined by hydrogen bonds to form microfibrils
microfibrils are very strong which means they provide support/strength/rigidity in a cell wall

Question 26

Sketch and label a diagram of a microfibril

Answer 26

Sketch and label a diagram of a microfibril

Question 27

Describe the method you would use to test for the presence of starch and see what a positive and negative result would look like

Answer 27

Describe the method you would use to test for the presence of starch and see what a positive and negative result would look like

Use the iodine test – add iodine dissolved in potassium iodide solution into a test sample.
look at the colour of the sample for the result.
a positive result would be dark blue-black and a negative result would be a browny-orange colour

Question 28

Cow’s milk contains the sugar lactose. Many cats are unable to digest cow’s milk because they are lactose intolerant.
Cow’s milk can be made suitable for these cats by treating it with the enzyme lactase to hydrolyse lactose.
This makes the cow’s milk lactose-free.
Beads are coated with lactase and placed in a tube, as shown in the diagram below. Cow’s milk flows over the beads and the lactose is hydrolysed.

(a) Attaching lactase to the beads is a more efficient use of lactase than adding the lactase directly to cow’s milk.
Suggest three reasons why it is more efficient to attach lactase to the beads.

(b) Monosaccharides and disaccharides taste sweet.
The lactose-free milk made after hydrolysis with lactase tastes sweeter than the cow’s milk containing lactose.
Suggest why.

Answer 28

Cow’s milk contains the sugar lactose. Many cats are unable to digest cow’s milk because they are lactose intolerant.
Cow’s milk can be made suitable for these cats by treating it with the enzyme lactase to hydrolyse lactose.
This makes the cow’s milk lactose-free.
Beads are coated with lactase and placed in a tube, as shown in the diagram below. Cow’s milk flows over the beads and the lactose is hydrolysed.

(a) Attaching lactase to the beads is a more efficient use of lactase than adding the lactase directly to cow’s milk.
Suggest three reasons why it is more efficient to attach lactase to the beads.

(Lactase / beads) can be reused

No need to remove from milk

Allows continuous process

The enzyme is more stable

Avoid end-product inhibition.

(b) Monosaccharides and disaccharides taste sweet.
The lactose-free milk made after hydrolysis with lactase tastes sweeter than the cow’s milk containing lactose.
Suggest why.

Lactose hydrolysed to galactose and glucose, So more sugar molecules
So more sugars produced are sweeter than lactose

Question 29

Give two ways in which the structure of starch is similar to cellulose.

Answer 29

Give two ways in which the structure of starch is similar to cellulose.

Are polymers and contain glycosidic bonds

Question 30

Give two ways in which the structure of starch is different from cellulose.

Answer 30

Give two ways in which the structure of starch is different from cellulose.

Starch contains alpha glucose, branched and not straight

Question 31

In plants, mass transport of sugars takes place through columns of sieve cells in the phloem. Other cells, called companion cells, transport sugars into, and out of, the sieve cells.

(i) Using the diagram, suggest and explain one other way in which sieve cells are
adapted for mass transport.

No organelles / very little cytoplasm / cytoplasm at edge / more room / hollow / large vacuole / large space / thick walls

(So) easier flow / (thick / strong walls) resist pressure

Answer 31

In plants, mass transport of sugars takes place through columns of sieve cells in the phloem. Other cells, called companion cells, transport sugars into, and out of, the sieve cells.

(i) Using the diagram, suggest and explain one other way in which sieve cells are
adapted for mass transport.

No organelles / very little cytoplasm / cytoplasm at edge / more room / hollow / large vacuole / large space / thick walls

(So) easier flow / (thick / strong walls) resist pressure

Question 32

Using the diagram, suggest and explain one other way in which companion cells are adapted for the transport of sugars between cells.

Answer 32

Using the diagram, suggest and explain one other way in which companion cells are adapted for the transport of sugars between cells.

Mitochondria release energy / ATP / site of respiration;

For active transport / uptake against concentration gradient.

Question 33

Starch molecules and cellulose molecules have different functions in plant cells. Each molecule is adapted for its function.
Explain one way in which starch molecules are adapted for their function in plant cells.

Answer 33

Starch molecules and cellulose molecules have different functions in plant cells. Each molecule is adapted for its function.
Explain one way in which starch molecules are adapted for their function in plant cells.

Insoluble so doesn’t affect water potential

Question 34

Explain how cellulose molecules are adapted for their function in plant cells.

Answer 34

Explain how cellulose molecules are adapted for their function in plant cells.

Long and straight chains become linked together by many hydrogen bonds to form fibrils that provide strength (to cell wall).

Question 35

A student investigated the effect of chewing on the digestion of starch in cooked wheat.
He devised a laboratory model of starch digestion in the human gut. This is the method he
used.
1. Volunteers chewed cooked wheat for a set time. The wheat had been cooked in boiling water.
2. This chewed wheat was mixed with water, hydrochloric acid and a protein-digesting enzyme and left at 37 °C for 30 minutes.
3. A buffer was then added to bring the pH to 6.0 and pancreatic amylase was added. This mixture was then left at 37 °C for 120 minutes.
4. Samples of the mixture were removed at 0, 10, 20, 40, 60 and 120 minutes, and the concentration of reducing sugar in each sample was measured.
5. Control experiments were carried out using cooked wheat that had been chopped up in a blender, not chewed.

(a) What reducing sugar, or sugars, would you expect to be produced during chewing? Give a reason for your answer
(b) In this model of digestion in the human gut, what other enzyme is required for the complete digestion of starch
(c) What was the purpose of step 2, in which samples were mixed with water, hydrochloric acid and pepsin

(d) in the control experiments, cooked wheat was chopped up to copy the effect of chewing.
Suggest a more appropriate control experiment. Explain your suggestion

Answer 35

A student investigated the effect of chewing on the digestion of starch in cooked wheat.
He devised a laboratory model of starch digestion in the human gut. This is the method he
used.
1. Volunteers chewed cooked wheat for a set time. The wheat had been cooked in boiling water.
2. This chewed wheat was mixed with water, hydrochloric acid and a protein-digesting enzyme and left at 37 °C for 30 minutes.
3. A buffer was then added to bring the pH to 6.0 and pancreatic amylase was added. This mixture was then left at 37 °C for 120 minutes.
4. Samples of the mixture were removed at 0, 10, 20, 40, 60 and 120 minutes, and the concentration of reducing sugar in each sample was measured.
5. Control experiments were carried out using cooked wheat that had been chopped up in a blender, not chewed.

(a) What reducing sugar, or sugars, would you expect to be produced during chewing? Give a reason for your answer

Maltose;
Salivary amylase breaks down starch

(b) In this model of digestion in the human gut, what other enzyme is required for the complete digestion of starch

Maltase

(c) What was the purpose of step 2, in which samples were mixed with water, hydrochloric acid and pepsin?

Mimics effect of stomach

(d) in the control experiments, cooked wheat was chopped up to copy the effect of chewing.
Suggest a more appropriate control experiment. Explain your suggestion

Add boiled saliva;
Everything same as experiment but salivary amylase denatured.

Question 36

In humans, the enzyme maltase breaks down maltose to glucose. This takes place at normal body temperature.

Explain why maltase:
• only breaks down maltose
• allows this reaction to take place at normal body temperature (5)

Answer 36

In humans, the enzyme maltase breaks down maltose to glucose. This takes place at normal body temperature.

Explain why maltase:
• only breaks down maltose
• allows this reaction to take place at normal body temperature (5)

Question 37

Scientists have investigated the effects of competitive and non-competitive inhibitors of the enzyme maltase.
Describe competitive and non-competitive inhibition of an enzyme.

Answer 37

Scientists have investigated the effects of competitive and non-competitive inhibitors of the enzyme maltase.
Describe competitive and non-competitive inhibition of an enzyme.

Tertiary structure of enzyme means active site is complimentary to maltose/substrate
Enzyme is a catalyst which lowers the activation energy required by forming enzyme substrate complex

Question 38

Explain how a sports drink could provide an energy boost when running.

Answer 38

Explain how a sports drink could provide an energy boost when running.

Drink contains carbohydrates / sugars so raises blood glucose concentration quickly;

Contains salt so glucose more rapidly absorbed;

Increases glucose to muscles for respiration;

faster respiration so faster energy release

Question 39

Nutritionists investigated the relationship between eating oily and non-oily fish and the incidence of asthma. They analysed the diets of children with asthma and the diets of children without asthma.

Children with asthma

Children who eat no fish: 28%
Children who ate only oily fish: 16%
Children who ate non-oily fish: 56%

children without asthma

Children who eat no fish: 16%
Children who ate only oily fish: 30%
Children who ate non-oily fish: 54%

(a) What conclusions can you make from the data?
(b) Describe how you could use the emulsion test to show the presence of oil in a sample of fish.

Answer 39

Nutritionists investigated the relationship between eating oily and non-oily fish and the incidence of asthma. They analysed the diets of children with asthma and the diets of children without asthma.

Children with asthma

Children who eat no fish: 28%
Children who ate only oily fish: 16%
Children who ate non-oily fish: 56%

children without asthma

Children who eat no fish: 16%
Children who ate only oily fish: 30%
Children who ate non-oily fish: 54%

What conclusions can you make from the data?

Fewer children with asthma eat fish;
Fewer children with asthma eat oily fish;
only 2% difference in children with or without asthma who eat non-oily fish.

Describe how you could use the emulsion test to show the presence of oil in a sample of fish.

Shake with ethanol
Then add water;
White / milky / cloudy layer indicates oil

Question 40

Describe how you test a piece of food for the presence of lipid

Answer 40

Describe how you test a piece of food for the presence of lipid

Dissolve in alcohol, then add water; White emulsion shows presence of lipid.

Question 41

Newborn babies can be fed with breast milk or with formula milk. Both types of milk contain carbohydrates, lipids and proteins.

• Human breast milk also contains a bile-activated lipase. This enzyme is thought to be inactive in milk but activated by bile in the small intestine of the newborn baby.
• Formula milk does not contain a bile-activated lipase.

Scientists investigated the benefits of breast milk compared with formula milk.
(a)
The scientists used kittens as model organisms in their laboratory investigation.

(a) Other than ethical reasons, suggest two reasons why they chose to use cats as model organisms.

mammals likely to have same physiology / reactions as humans;
Small enough to keep in laboratory / produce enough milk to extract;
(Can use a) large number.

(b) Before starting their experiments, the scientists confirmed that, like human breast milk, cat’s milk also contained bile-activated lipase.
To do this, they added bile to cat’s milk and monitored the pH of the mixture.
Explain why monitoring the pH of the mixture could show whether the cat’s milk contained lipase.

Hydrolysis of lipids produces fatty acids;
Which lower pH of mixture.

Answer 41

Newborn babies can be fed with breast milk or with formula milk. Both types of milk contain carbohydrates, lipids and proteins.

• Human breast milk also contains a bile-activated lipase. This enzyme is thought to be inactive in milk but activated by bile in the small intestine of the newborn baby.
• Formula milk does not contain a bile-activated lipase.

Scientists investigated the benefits of breast milk compared with formula milk.
(a)
The scientists used kittens as model organisms in their laboratory investigation.

Other than ethical reasons, suggest two reasons why they chose to use cats as model organisms.

mammals likely to have same physiology / reactions as humans;
Small enough to keep in laboratory / produce enough milk to extract;
(Can use a) large number.

Question 42

Structure of the phospholipid is different from triglyceride describe the phospholipid

Answer 42

Structure of the phospholipid is different from triglyceride describe the phospholipid

Has a phosphate group instead of one of the fatty acids in the triglyceride

Question 43

What is meant by an unsaturated fatty acid

Answer 43

What is meant by an unsaturated fatty acid

Double bonds present between carbons in a fatty acid

Question 44

Does starch only contain the elements carbon oxygen and hydrogen

Does glycogen only contain the elements carbon oxygen and hydrogen

Does deoxyribose only contain the elements carbon oxygen and hydrogen

Does DNA Helicase only contain the elements carbon oxygen and hydrogen

Is starch made from amino acid monomers

Is glycogen made from amino acid monomers

Is deoxyribose made from amino acid monomers

Is DNA helicase made from amino acid monomers

Is starch found in both animal cells and plant cells

Is glycogen found in both animal cells and plant cells

Is deoxyribose found in both animal cells and plant cells

Is DNA helicase found in both animal cells and plant cells

Answer 44

Does starch only contain the elements carbon oxygen and hydrogen

No

Does glycogen only contain the elements carbon oxygen and hydrogen

Yes

Does deoxyribose only contain the elements carbon oxygen and hydrogen

Yes

Does DNA Helicase only contain the elements carbon oxygen and hydrogen

Yes

Is starch made from amino acid monomers

No

Is glycogen made from amino acid monomers

No

Is deoxyribose made from amino acid monomers

No

Is DNA helicase made from amino acid monomers

Yes

Is starch found in both animal cells and plant cells

No

Is glycogen found in both animal cells and plant cells

No

Is deoxyribose found in both animal cells and plant cells

Yes

Is DNA helicase found in both animal cells and plant cells

Yes

Question 45

Hydrogen bonds are important in cellulose molecules. Explain why.

Answer 45

Hydrogen bonds are important in cellulose molecules. Explain why.

Holds cellulose molecules together
cellulose molecules form microfibrils, providing strength
H bonds are strong in large numbers

Question 46

A starch molecule has a spiral shape. Explain why this shape is important to its function in cells.

Answer 46

A starch molecule has a spiral shape. Explain why this shape is important to its function in cells.

Compact and tightly packed

Question 47

Triglycerides are taken into the body as part of a balanced diet. These triglycerides contain fatty acids including omega-3 fatty acids.
It has been discovered that omega-3 fatty acids are associated with health benefits.
The benefits include faster development of nerve cells and clearer vision.
Omega-3 fatty acids are also associated with protection from heart disease, arthritis and cancer.

Triglycerides in food —> Digestion and release of fatty acids In the small intestine —> fatty acids are transported to tissue by blood —> Fatty acids are taken up by cells —> Used to make plasma membranes, Required for energy, and Converted to other fatty acids

Use the information in the figure to explain two ways in which fatty acids are important in the formation of new cells.

Answer 47

Triglycerides are taken into the body as part of a balanced diet. These triglycerides contain fatty acids including omega-3 fatty acids.
It has been discovered that omega-3 fatty acids are associated with health benefits.
The benefits include faster development of nerve cells and clearer vision.
Omega-3 fatty acids are also associated with protection from heart disease, arthritis and cancer.

Triglycerides in food —> Digestion and release of fatty acids In the small intestine —> fatty acids are transported to tissue by blood —> Fatty acids are taken up by cells —> Used to make plasma membranes, Required for energy, and Converted to other fatty acids

Use the information in the figure to explain two ways in which fatty acids are important in the formation of new cells.

Fatty acids used to make phospholipids; Phospholipids in membranes;
More phospholipids more membranes made;

Fatty acids respired to release energy;
More triglycerides more energy released;
Energy used for cell production

Question 48

Draw the triglyceride that would be formed from condensation reactions between a molecule of glycerol and three molecules of propanoic acid

Answer 48

Draw the triglyceride that would be formed from condensation reactions between a molecule of glycerol and three molecules of propanoic acid

Question 49

Explain how the structure of phospholipids make them able to form the bilayer of cell membranes

Answer 49

Explain how the structure of phospholipids make them able to form the bilayer of cell membranes

Phospholipid heads are hydrophilic and their tails are hydrophobic, so they form a double layer with their heads facing out towards the water on either side this makes the centre of the membrane bilayer hydrophobic, so water-soluble substances can’t easily pass through it

Question 50

What is the primary, Secondary tertiary and Quaternary structure of a protein

Answer 50

What is the primary, Secondary tertiary and Quaternary structure of a protein

Primary structure is the sequence of amino acid in the polypeptide chain

Secondary structure is when hydrogen bonds formed between the amino acid’s which make it coil into an alpha helix or folded into a beater pleated sheet

Tertiary structure is when the chain of amino acid is coiled and folded further hydrogen bonds and ionic bonds form between different parts of the polypeptide chain and disulfied bridges also form whenever two molecules of the amino acid cysteine come close together

Quaternary structure is the way these polypeptide chains are assembled together which is the proteins final 3-D structure

Question 51

The biuret test for proteins And what precipitate presents a positive result

Answer 51

The biuret test for proteins

The test solution needs to be alkaline so first you add a few drops of sodium hydroxide solution then you add some copper sulphate solution

Purple colour indicates protein

Question 52

What organ produces amylase

What organ produces maltase

Answer 52

What organ produces amylase

Pancreas

What organ produces maltase

Small intestine

Question 53

Maltose is hydrolysed by the enzyme maltase.

Explain why maltase catalyses only this reaction

Answer 53

Maltose is hydrolysed by the enzyme maltase.
Explain why maltase catalyses only this reaction

active site is complementary to substrate/maltose;
(Only) maltose can fit;
To form enzyme substrate complex.

Question 54

Give one function of lysosomes

Answer 54

Give one function of lysosomes

Breakdown toxins

Question 55

Describe and explain how centrifuging the culture allowed the scientists to obtain a cell-free liquid

Answer 55

Describe and explain how centrifuging the culture allowed the scientists to obtain a cell-free liquid.

heavy cells;
move to bottom of tube (when centrifuged); supernatant can be removed.

Question 56

H. pylori cells produce an enzyme that neutralises acid.

Suggest one advantage to the H. pylori of producing this enzyme.

Answer 56

H. pylori cells produce an enzyme that neutralises acid.
Suggest one advantage to the H. pylori of producing this enzyme.

Break down toxins

Question 57

A principle of homeostasis is the maintenance of a constant internal environment. An increase in the concentration of carbon dioxide would change the internal environment and blood pH.
Explain the importance of maintaining a constant blood pH.

Answer 57

A principle of homeostasis is the maintenance of a constant internal environment. An increase in the concentration of carbon dioxide would change the internal environment and blood pH.
Explain the importance of maintaining a constant blood pH.

enzyme (in blood) affected by change in pH;
eg haemoglobin, carrier protein in plasma membrane
(Resultant) change of charge/shape/tertiary structure;
less oxygen binds with haemoglobin / less transport across membranes / fewer substrates can fit active site / fewer enzyme-substrate complexes.

Question 58

Suggest how the antidote can reduce poisoning by cyanide.

Answer 58

Suggest how the antidote can reduce poisoning by cyanide.

(Antidote reacts with / binds to cyanide) so cyanide cannot bind to enzyme / cytochrome oxidase

Question 59

technician investigated the effect of temperature on the rate of an enzyme-controlled reaction. At each temperature, he started the reaction using the same volume of substrate solution and the same volume of enzyme solution

Give one other factor the technician would have controlled

Answer 59

technician investigated the effect of temperature on the rate of an enzyme-controlled reaction. At each temperature, he started the reaction using the same volume of substrate solution and the same volume of enzyme solution

Give one other factor the technician would have controlled

Concentration of substrate solution

Question 60

Rate of reaction =

Answer 60

Rate of reaction = change in y /change in x

Question 61

Scientists determined that a sample of DNA contained 18% adenine.
What were the percentages of thymine and guanine in this sample of DNA?

Answer 61

Scientists determined that a sample of DNA contained 18% adenine.
What were the percentages of thymine and guanine in this sample of DNA?

Thymine 18 (%)
Guanine 32 (%).

Question 62

Directions in which each new DNA strand is being produced.

explain why the arrows point in opposite directions

DNA has antiparallel strands

2. (Figure 1 shows) shape of the nucleotides is different
3. Enzymes have active sites with specific shape;
4. Only substrates with complementary shape

Answer 62

Directions in which each new DNA strand is being produced.

explain why the arrows point in opposite directions

DNA has antiparallel strands

2. (Figure 1 shows) shape of the nucleotides is different
3. Enzymes have active sites with specific shape;
4. Only substrates with complementary shape

Question 63

Draw the dipeptides and polypeptide that would be formed from a condensation reaction between:

glycine and valine

Alanine and glycine

Glycine alanine and valine

Answer 63

Draw the dipeptides and polypeptide that would be formed from a condensation reaction between:

glycine and valine

Alanine and glycine

Glycine alanine and valine

Question 64

What term is used to describe an enzyme acts outside cells

Answer 64

What term is used to describe an enzyme acts outside cells

Extra cellular

Question 65

Explain in terms of activation energy Why an enzyme enables reactions to happen at lower temperatures than without an enzyme

Answer 65

Explain in terms of activation energy Why an enzyme enables reactions to happen at lower temperatures than without an enzyme

Activation energy is needed to start a chemical reaction
the activation energy is often provided as heat
with the presence of an enzyme the activation energy required to start a reaction is lowered
therefore not as much Heat is needed so the reaction that can take place will be at a lower temperature than it could do without an enzyme

Question 66

What is the main difference between the lock and key model and the induced fit model

Answer 66

What is the main difference between the lock and key model and the induced fit model

In the lock and key model the active site has a fixed shape that is complimentary to the substrate but in the induced fit model of the active site has to change shape slightly to allow the substrate to bind tightly

Question 67

Methanol is broken down in the body into formaldehyde
The buildup of formaldehyde can cause death the enzyme that hydrolyses
The reaction is alcohol dehydrogenase

Someone had been poisoned with methanol they could be helped by being given ethanol as soon as possible explain why

Answer 67

Methanol is broken down in the body into formaldehyde
The buildup of formaldehyde can cause death the enzyme that hydrolyses
The reaction is alcohol dehydrogenase

Someone had been poisoned with methanol they could be helped by being given ethanol as soon as possible explain why

Ethanol has a similar shape to methanol this means it will act as a competitive inhibitor binding to the active site of alcohol dehydrogenase and blocking methanol molecules this means lower levels of methanol will be hydrolysed so the toxic products formaldehyde won’t build up to fatal levels

Question 68

Explain how non-competitive inhibition prevents enzyme activity

Answer 68

Explain how non-competitive inhibition prevents enzyme activity

A non-competitive inhibitor molecule binds to the enzyme away from the active site its presence alters the shape of the active site meaning that substrate molecules can no longer bind here this prevents enzyme activity

Question 69

Describe the structure of sucrose and explain how it is formed

Answer 69

Describe the structure of sucrose and explain how it is formed

Sucrose is made from a fructose molecule and a glucose molecule which are joined by a Glycosidic bond formed during a condensation reaction

Question 70

Draw two monosaccharides that join together to form sucrose

Answer 70

Draw two monosaccharides that join together to form sucrose

Question 71

Describe a biochemical test you could use to identify the presence of a non-reducing sugar

Answer 71

Describe a biochemical test you could use to identify the presence of a non-reducing sugar

Initially the sample is heated in a water bath that’s been brought to the boil with Benedict Regent to rule out the presence of reducing sugars a new test sample is then heated in a water bath that’s been brought to the boil with dilute hydrochloric acid and then neutralised with sodium hydrocarbonate next the sample is heated with Benedicts regent
the test sample would form a coloured green yellow orange brick red precipitate if a non-reducing sugar was present

Question 72

Glycogen is a polysaccharide describe the structure of glycogen and explain how it structure makes it suited to its function

Answer 72

Glycogen is a polysaccharide describe the structure of glycogen and explain how it structure makes it suited to its function

Glycogen is a long branched chain of alpha glucose
animals use it to store excess glucose
many branches means that the glucose can be released quickly for energy
it is also compact shape so it is easy to store

Question 73

The biuret test can be used to test for the presence of protein in a sample describe how this test would be carried out including what observations would indicate positive and negative results

Answer 73

The biuret test can be used to test for the presence of protein in a sample describe how this test would be carried out including what observations would indicate positive and negative results

Add a few drops of sodium hydroxide solution to the test sample then add some copper sulphate solution if protein is present the solution will turn purple if there is no protein present the solution will stay blue

Question 74

Draw the structure of an amino acid

Answer 74

Draw the structure of an amino acid

Question 75

Describe the process by which pepsin breaks down a protein

Answer 75

Describe the process by which pepsin breaks down protein

The protein binds to pepsin is active site to form an enzyme substrate complex this lowers the activation energy for the breakdown of the protein by putting strain on the peptide bonds making them easier to break
the reaction is catalysed and the products are released

Question 76

Describe the enzymes tertiary structure and how it relates to its properties

Answer 76

Describe the enzymes tertiary structure and how it relates to its properties

The tertiary structure is the 3-D structure of the polypeptide chain formed by hydrogen bonding and ionic bonding between different parts of the chain disulphide bridges can also be formed between cystiene R groups
the tertiary structure determines the shape of the active site of an enzyme
the shape of the active site makes the enzyme specific to its substrate

Question 77

Explain what happens when an enzyme is denatured

Answer 77

Explain what happens when an enzyme is denatured

The shape of the active site has changed so it’s no longer complimentary in shape to the substrate and will not find to it to catalyse the reaction

Question 78

Suggest two variables you would control if you investigating the activity of gastric lipase a different pH values

Answer 78

Suggest two variables you would control if you investigating the activity of gastric lipase a different pH values

Temperature and substrate concentration

Question 79

Scientist analysed a section of double-stranded DNA there were 68 bases in total (34 base pairs) and 22 of the bases were adenine how many of the bases were:

(a) cytosine
(b) thymine
(c) guanine

Answer 79

Scientist analysed a section of double-stranded DNA there were68 bases in total (34 base pairs) and 22 of the bases were adenine how many of the bases were:

(a) cytosine 12
(b) thymine 22
(c) guanine 12

Question 80

What is the function of DNA

What are ribosome is made up of

Name the monomer of DNA and RNA

Describe the structure of the DNA nucleotide

Name the four possible bases in DNA

What type of bond, present in a new poly nucleotide chain, consists of two ester bonds and a phosphate group

Answer 80

What is the function of DNA
It’s stores genetic information

What are ribosome is made up of
RNA and proteins

Describe the structure of the DNA nucleotide
A DNA nucleotide contains a phosphate group, the pentose sugar deoxyribose and a nitrogen-containing organic base

Name the four possible bases in DNA
Adenine thymine cytosine and thymine

What type of bond, present in a new poly nucleotide chain, consists of two ester bonds and a phosphate group
Phosphodiester bonds

Question 81

Describe how a DNA double helix is formed from two polynucleotide strands

Name of the sugar in RNA

Name the four possible bases in RNA

Describe three differences between DNA and RNA

What caused many scientists to doubt that

Answer 81

Describe how a DNA double helix is formed from two polynucleotide strands
Two DNA polynucleotide strands join together by hydrogen bonding between complimentary base pairs – A with T and G with C.
2 hydrogen bonds form between A and T, and three hydrogen bonds formed between C and G. the antiparallel strands then twist round each other to form the DNA double helix

Name of the sugar in RNA
Ribose

Name the four possible bases in RNA
Adenine, thymine, cytosine and uracil

Describe three differences between DNA and RNA
DNA is double-stranded whereas RNA is single standard
The pentose sugar in DNA is deoxyribose but its ribose in RNA
DNA contains the base thymine whereas RNA doesn’t it contains uracil instead

What caused many scientists to doubt that DNA carried the genetic code
DNA has a relatively simple chemical composition

Question 82

DNA is copied by semiconservative replication of DNA what is meant by this

Answer 82

DNA is copied by semiconservative replication of DNA what is meant by this

It is where half of the new strands of DNA are from the original molecule of DNA

Question 83

Name the two enzymes involved in DNA replication

describe the first stage of DNA replication in which two strands of DNA are separated

describe the second stage of DNA replication where the single strands of DNA act as templates

Answer 83

Name the two enzymes involved in DNA replication
DNA helicase and DNA polymerase

describe the first stage of DNA replication in which two strands of DNA are separated
DNA helicase breaks the hydrogen bonds between the bases on the two polynucleotide DNA strands this makes the helix unwind to form two single strands

describe the second stage of DNA replication where the single strands of DNA act as templates
Free-floating DNA nucleotides are attached to their complimentary exposed bases on each original template strand – A with T and C with G

Question 84

In addition to ADP and ATP cells can also contain a molecule called AMP adenosine monophosphate

suggest what the structure of this molecule is

Answer 84

In addition to ADP and ATP cells can also contain a molecule called AMP adenosine monophosphate

suggest what the structure of this molecule is

AMP is made from a molecule of adenine and a molecule of ribose and one phosphate group

Question 85

The movement of calcium irons across a cell membrane can occur via the energy requiring process of active transport
This movement of calcium ions is coupled to the breakdown of ATP. suggest why.

Answer 85

The movement of calcium irons across a cell membrane can occur via the energy requiring process of active transport
This movement of calcium ions is coupled to the breakdown of ATP. suggest why.

The breakdown/hydrolysis of ATP releases energy, so when this reaction is coupled to the process of active transport it provides the energy for this process directly

Question 86

Describe the structure of a molecule of ATP

what is ATP broken down into

by what type of reaction is ATP broken down

what enzyme catalyses the breakdown of ATP

how can inorganic phosphate released by the breakdown of ATP be used

Answer 86

Describe the structure of a molecule of ATP
A molecule of ATP is made from a molecule of adenine, a molecule of ribose and three phosphate groups

what is ATP broken down into
ADP and Pi

by what type of reaction is ATP broken down
Hydrolysis

what enzyme catalyses the breakdown of ATP
ATP hydrolase

how can inorganic phosphate released by the breakdown of ATP be used
It can be used to phosphorylate another compound/added to another compound, which often makes the compound more reactive

Question 87

ATP can be re-formed by the addition of an inorganic phosphate to ADP

what type of reaction is this and give an example of a process during which this reaction takes place

Answer 87

ATP can be re-formed by the addition of an inorganic phosphate to ADP

what type of reaction is this and give an example of a process during which this reaction takes place

Condensation reaction
this reaction takes place in photosynthesis and respiration

Question 88

Name two reactions that water is involved in

why is water classed as a polar molecule

what is a hydrogen bond

what is a metabolite

Answer 88

Name two reactions that water is involved in
Condensation and hydrolysis

why is water classed as a polar molecule
Because it has a slight negative charge on one side and a slight positive charge on the other

what is a hydrogen bond
A weak bond between a slightly positively charged hydrogen atom in one molecule and a slightly negatively charged atom in another molecule

what is a metabolite
A substance involved in a metabolic reaction

Question 89

What makes water useful as a solvent

water has a high latent heat of vaporisation what does this mean

explain why water has a high specific heat capacity

what is cohesion

why is cohesion between water molecules important in plants

Answer 89

What makes water useful as a solvent
Its polarity

water has a high latent heat of vaporisation what does this mean
Lots of heat is used to change it from a liquid to a gas

explain why water has a high specific heat capacity
Because when water is heated, a lot of the heat energy is used to break the hydrogen bonds between water molecules.
this means there is less heat energy available to actually increase the temperature of the water

what is cohesion
The attraction between molecules of the same type, for example two water molecules

why is cohesion between water molecules important in plants
Strong cohesion between water molecules allows water to travel in columns in the xylem tissue inside plants. substances are transported around plants in this way

Question 90

What is an inorganic ion
An ion that doesn’t contain carbon

where do you inorganic ions occur
They are present in solution in the cytoplasm of cells and in the body fluids of organisms

What determines an ions specific role
It’s specific properties

What ions are part of haemoglobin molecules
Iron ions

what is the role of these ions in haemoglobin
They bind to oxygen

name the ion that is linked to pH
Hydrogen ions/H+ ions

which type of ion is involved in moving glucose and amino acids across cell membranes
Sodium ions/Na+

what is the name of this process
Co-transport

Answer 90

What is an inorganic ion

where do you inorganic ions occur

What determines an ions specific role

What ions are part of haemoglobin molecules

what is the role of these ions in haemoglobin

name the ion that is linked to pH

which type of ion is involved in moving glucose and amino acids across cell membranes

what is the name of this process

Question 91

ATP hydrolysis is coupled to the action of DNA Helicases in unwinding a DNA molecule during DNA replication

describe the reaction of ATP hydrolysis

Suggest why ATP hydrolysis is coupled to the action of DNA helicase

Answer 91

name one of the molecule that contains a phosphate ion

ATP hydrolysis is coupled to the action of DNA Helicases in unwinding a DNA molecule during DNA replication

describe the reaction of ATP hydrolysis
During ATP hydrolysis, ATP is broken down into a molecule of ADP and a phosphate group a phosphate bond is broken and this releases energy this reaction is catalysed by ATP hydrolase

Suggest why ATP hydrolysis is coupled to the action of DNA helicase
ATP hydrolysis can be coupled to reactions that require energy so that energy can be supplied directly to the reaction and allow it to take place
DNA Helicase must therefore require energy in order to unwind DNA molecules by breaking hydrogen bonds

Question 92

When humans exercise vigourously they lose water from their bodies in sweat

name the property of water that enables sweating to have a cooling effect on the body during exercise. explain how it has this affect

sweat contains ions such as sodium ions, dissolved in water, describe how sodium ions dissolve in water

give one use of sodium ions in the body

Answer 92

When humans exercise vigourously they lose water from their bodies in sweat

name the property of water that enables sweating to have a cooling effect on the body during exercise. explain how it has this affect
Water has a high latent heat of vaporisation which means it carries away a lot of heat energy when it evaporates from the surface so when sweat evaporates from the body it carries away heat energy which cools the surface in it helps to lower the temperature of the body

sweat contains ions such as sodium ions, dissolved in water, describe how sodium ions dissolve in water
Water is a polar molecule/has a slightly positively charged and in a slightly negative charged and the slightly negative charged end of a water molecule will be attracted towards these positively charged sodium ions
the ions will become totally surrounded by water molecules and this means they are dissolved in water

give one use of sodium ions in the body
A molecule of glucose can be cold transported into the cell alongside sodium ions

Question 93

Name all the parts you could find in the mitochondrion

Answer 93

Name all the parts you could find in the mitochondrion

The matrix the outer membrane and the Cristae

Question 94

Give two functions of the cell surface membrane

Describe the function of the nucleus

Describe the appearance of the Golgi apparatus

Give one function of the lysosome

What is the function of the smooth endoplasmic reticulum

Explain the difference between a tissue and an organ

What is an organ system?

Answer 94

Give two functions of the cell surface membrane
To regulate movement of substances into and out of the cell and to respond to chemicals like hormones

Describe the function of the nucleus
The nucleus controls the cells activities by controlling the transcription of DNA

Describe the appearance of the Golgi apparatus
It is a group of fluid filled membrane-bound flattened sacks

Give one function of the lysosome
To digest invading cells and to break down worn out components of the cell

What is the function of the smooth endoplasmic reticulum
It’s synthesisers and processes lipids

Explain the difference between a tissue and an organ
Are tissues by similar cells are grouped together, whereas an organ is by different tissues are grouped together to perform a particular function

What is an organ system?
And organ systems is where different organs work together to carry out a particular function

Question 95

Suggest why the capsule and the flagellin make prokaryotic cells well adapted to living in the gut

Answer 95

Suggest why the capsule and the flagellin make prokaryotic cells well adapted to living in the gut

The capsule is a layer of slime can help protect the bacterium from attack by the hosts immune system the flagellin allows the bacteria to move through the gut

Question 96

Where is murein used in prokaryotic cells

Name and describe the process by which prokaryotic cells reproduce

What is a capsid

What is the role of viral attachment proteins

Answer 96

Where is murein used in prokaryotic cells
In the cell wall

Name and describe the process by which prokaryotic cells reproduce
Binary fission.
the circular DNA and plasmids replicate, the main DNA loop is only replicated once but the plasmids can be replicated several times the cell gets bigger and the DNA loops move to opposite poles of the cell. The cytoplasm begins to divide and new cell walls begin to form. the cytoplasm divides and two two daughter cells are produced. each daughter cell has one copy of the circular DNA but a variable number of copies of the plasmids

What is a capsid
The protein coat that surrounds the core of genetic material in a virus

What is the role of viral attachment proteins
They allow a virus to attach to specific host cells which have the complimentary receptor proteins

Question 97

Convert:

millimetre to micro meter

micro meter to nanometre

Answer 97

Convert:

millimetre to micro meter x1000

micro meter to nanometre x1000

Question 98

Order of organelles separated in cell fractionation is Nuclei Chloroplasts Mitochondria Lysosomes ER and Ribosomes

Good way of remembering:

Answer 98

Order of organelles separated in cell fractionation is Nuclei Chloroplasts Mitochondria Lysosomes ER and Ribosomes

Naughty Clever Monkeys Like Eating Red Raspberries

Question 99

Suggest what type of microscope you would use in each of the following scenarios and give a reason for each answer.

studying how E. coli bacteria replicate

Studying the 3-D structure of red blood cells

studying virus particles that are 0.1 micro meter in diameter

Answer 99

Suggest what type of microscope you would use in each of the following scenarios and give a reason for each answer.

studying how E. coli bacteria replicate
An optical microscope, as electron microscopes can only be used on dead specimens

Studying the 3-D structure of red blood cells
SEN, as they can give 3-D images

studying virus particles that are 0.1 micro meter in diameter
Electron microscope (TEM/SEM) as the virus particles are smaller than the maximum resolution of optical microscopes

Question 100

What is the maximum resolution for an optical microscope and an electron microscope

What type of microscope would you use to study lysosomes

How do you transmission electron microscope’s work

how do you scanning electron microscope’s work

give one advantage and one disadvantage of TEMs

Answer 100

What is the maximum resolution for an optical microscope and an electron microscope
OP- 0.2 micro metres
EM- 0.0002 micro metres

What type of microscope would you use to study lysosomes
EM

How do you transmission electron microscope’s work
TEMs use electromagnets to focus a beam of electrons, which is then transmitted through the specimen. denser parts of the specimen absorb more electrons, which makes them look darker on the image you end up with

how do you scanning electron microscope’s work
SEM’s scan a beam of electrons across the specimen. this knocks off electrons from the specimen, which are gathered in a cathode ray tube to form an image

give one advantage and one disadvantage of TEMs
Advantage: gives high resolution images so can be used to look at small objects and the internal structure of organelles
disadvantage: can only be used on thin specimens and can only be used on non-living specimens

Question 101

Give one advantage of SEMs over TEMs

What is the temporary mount microscope slide

What is a microscope artefact

How did the first scientists to use electron microscopes distinguish between artefacts and organelles

Give two ways homogenisation for cell fractionation is done

describe what happens at the filtration step of cell fractionation and explain why it is carried out

Answer 101

Give one advantage of SEMs over TEMs
Can be used on thick specimens, whereas TE and can’t

What is the temporary mount microscope slide
I prepared microscope slide in which the specimen has been suspended in a drop of liquid

What is a microscope artefact
Something that you can see down the microscope that isn’t part of the cell

How did the first scientists to use electron microscopes distinguish between artefacts and organelles
They repeatedly prepared specimens in different ways if an object could be seen with one preparation technique but not another, it was more likely to be an artefact in it than an organelle.

Give two ways homogenisation for cell fractionation is done
By vibrating the cells, or by grinding the cells up in a blender

describe what happens at the filtration step of cell fractionation and explain why it is carried out
The homogenised cell solution is filtered through a gauze to separate any large cell debris or tissue debris, like connective tissue, from the organelles

Question 102

What happens in anaphase

Answer 102

What happens in anaphase

Centromeres have divided, separating each pair of sister chromatids and the spindle fibres have contracted, pulling the chromatids to opposite poles of the spindle by their centromeres

Question 103

What happens in metaphase

Answer 103

What happens in metaphase

Chromosomes line up down the middle of the cell and are attached to spindle fibres

Question 104

The scientist is looking at tissue sample under a microscope she counts 150 cells undergoing mitosis, of those, 12 cells are in prophase. 1 complete cell cycle of the tissue lasts 0.70 days how long do the cells spend in prophase give your answer in hours

Answer 104

The scientist is looking at tissue sample under a microscope she counts 150 cells undergoing mitosis, of those, 12 cells are in prophase. 1 complete cell cycle of the tissue lasts 0.70 days how long do the cells spend in prophase give your answer in hours

(12/150) x 16.8 = 1.3 hours in prophase

Question 105

Methotrexate and vincristine Are drugs to use to treat cancer methotrexate blocks the formation of nucleotides within cells and vincristine prevent the formation of spindle fibres within the nucleus of cells

which stage of the cell cycle is distributed by:

(a) methotrexate
(b) vincristine

Answer 105

Methotrexate and vincristine Are drugs to use to treat cancer methotrexate blocks the formation of nucleotides within cells and vincristine prevent the formation of spindle fibres within the nucleus of cells

which stage of the cell cycle is distributed by:

(a) methotrexate
(b) vincristine

Question 106

What is the cell cycle

why is mitosis needed

what stage of the cell cycle does all the DNA unravel

Answer 106

What is the cell cycle
The process that all body cells from multi cellular organisms used to grow and divide

why is mitosis needed
For growth and for repairing damaged tissues

what stage of the cell cycle does all the DNA unravel
Interphase

Question 107

describe what happens during prophase

describe what happens during telophase

what is cytokinesis

what is cancer

Answer 107

describe what happens during prophase
During prophase the chromosomes condense, getting shorter and fatter.
the Centrioles start moving to opposite ends of the cell, forming the spindle.
the nuclear envelope breaks down and chromosomes lie free in the cytoplasm

describe what happens during telophase
During telophase the chromatids reach the opposite poles on the spindle
they uncoil and become long and thin again there now called chromosomes again
a nuclear envelope forms around each group of chromosomes so there are now two nuclei
the cytoplasm divides and there are now two daughter cells that are genetically identical to the original cell and to each other

what is cytokinesis
Division of the cell cytoplasm

what is cancer
It’s a tumour that invades surrounding tissues

Question 108

Mitotic index =

Answer 108

Mitotic index = number of cells with visible chromosomes/total number of cells observed

Question 109

If you observed 30 cells and four of them had visible chromosomes what is the mitotic index

Answer 109

If you observed 30 cells and four of them had visible chromosomes what is the mitotic index

4/30 = 0.13

Question 110

A student prepared a stained squash slide of cells from a hyacinth root tip, in order to investigate mitosis

Why is it necessary for the student to add a stain in order to investigate mitosis

Name one suitable stain that he could’ve used

Describe how the student should have squashed the tissue on the slide to avoid damaging the chromosomes

would you expect the mitotic index of these root tip cells to be higher or lower than the mitotic index of your cells taken from a mature hyacinth leaf explain your answer

Answer 110

A student prepared a stained squash slide of cells from a hyacinth root tip, in order to investigate mitosis

Why is it necessary for the student to add a stain in order to investigate mitosis
To make the chromosomes easier to see under the microscope

Name one suitable stain that he could’ve used
Toluidine blue O

Describe how the student should have squashed the tissue on the slide to avoid damaging the chromosomes
The student should have put a cover slip on top of the specimen and pushed on firmly making sure that he didn’t smear the coverslip sideways

would you expect the mitotic index of these root tip cells to be higher or lower than the mitotic index of your cells taken from a mature hyacinth leaf explain your answer
The mitotic index for the root tip cells would be higher because they are part of a tissue that is undergoing a lot of growth – unlike the mature leaf

Question 111

Describe how to focus an optical microscope on a specimen

what is an eyepiece graticule

what is the purpose of a stage micro meter

Answer 111

Describe how to focus an optical microscope on a specimen
The slide containing the specimen should first be clipped onto the slide then an objective lens should be selected and the course adjustment knob used to position the objective lens just above the slide finally, while looking down the eyepiece, the fine adjustment knob should be used to adjust the focus until a clear image of the specimen can be seen

what is an eyepiece graticule
And eyepiece graticule is fitted onto the eyepiece it’s like a transparent ruler with the numbers, but no units

what is the purpose of a stage micro meter
A stage micro meter is used to work out the value of the divisions on the eyepiece graticule at a particular magnification

Question 112

A scientist is the studying secretary epithelial cells from the stomach under an optical microscope the microscope has a magnification of x 100 and the resolution of 0.2 micro metres the ribosomes in the epithelial cells are 25 micro metre in diameter will the scientist be able to see them using the light microscope explain your answer

Answer 112

A scientist is the studying secretary epithelial cells from the stomach under an optical microscope the microscope has a magnification of x 100 and the resolution of 0.2 micro metres the ribosomes in the epithelial cells are 25 micro metre in diameter will the scientist be able to see them using the light microscope explain your answer

Know the microscope has a resolution of 0.2 micro metres which means it can’t distinguish between objects that are smaller than 0.2 micro metres such as the ribosomes

Question 113

The scientist sees an image of an epithelial cell that is 4 mm in diameter calculate the actual diameter of the cell

Answer 113

The scientist sees an image of an epithelial cell that is 4 mm in diameter calculate the actual diameter of the cell

Size of real object = size of image/magnification

4÷100 = 0 .04 mm

Question 114

One of the main functions of secretary epithelial cells in the stomach is to produce and secrete digestive enzymes suggest one organelle that is likely to present in large numbers in the epithelial cells to aid this function explain your choice

Answer 114

One of the main functions of secretary epithelial cells in the stomach is to produce and secrete digestive enzymes suggest one organelle that is likely to present in large numbers in the epithelial cells to aid this function explain your choice

Ribosomes as these are the site of protein synthesis

Question 115

The scientist also separated the organelles by cell fractionation in order to study each one individually describe and explain the process of cell fractionation

Answer 115

The scientist also separated the organelles by cell fractionation in order to study each one individually describe and explain the process of cell fractionation

First the cell membranes are broken down by homogenisation to release the organelles into solution
the solution is kept ice cold to prevent enzymes breaking down the organelles
an isotonic solution is used to prevent damage to organelles by osmosis
a buffer solution is added to maintain the pH the homogenised to sell solution is then filtered through a gauze to separate any large-cell debris or tissue debris from the organelles ultracentrifugation is then carried out to separate each organelle from the others the cell fragments are poured into a tube and spun in a centrifuge to separate out the heaviest organelles, which remains in the palate at the bottom of the tube, leaving the others Suspended in the supernatant this process is then repeated at higher and higher speeds to separate out all the organelles

Question 116

Penicillins are a group of antibiotics that are only effective against prokaryotic cells they work by inhibiting cell wall synthesis, leading to sell lysis (bursting) explain why penicillin antibiotics can clear bacterial infections in humans without harming the infected individuals cells

Answer 116

Penicillins are a group of antibiotics that are only effective against prokaryotic cells they work by inhibiting cell wall synthesis, leading to sell lysis (bursting) explain why penicillin antibiotics can clear bacterial infections in humans without harming the infected individuals cells

Bacteria are prokaryotic cells, so the penicillin inhibits the synthesis of the cell walls, eventually leading to cell lysis and death human cells are eukaryotic animal cells and so have no cell wall so penicillin antibiotics leave the cells unaffected

Question 117

Antibiotics can be used to target other features of prokaryotic cells give an example of a feature that could be targeted and explain what it would be appropriate

Answer 117

Antibiotics can be used to target other features of prokaryotic cells give an example of a feature that could be targeted and explain what it would be appropriate

Antibiotic to target the capsule of prokaryotic cells which human cells don’t have.this would leave the prokaryotics more open to attack from the cells of the hosts immune system

Question 118

Suggest a function of each of the following membranes:

(a) The membrane surrounding a chloroplast
(b) the membrane surrounding a bacterial cell

Answer 118

Suggest a function of each of the following membranes:

(a) The membrane surrounding a chloroplast
To keep the enzymes needed for photosynthesis all in one place

(b) the membrane surrounding a bacterial cell
To control what substances enter and leave the cell

Question 119

Chloride ions need to pass through the cell surface membrane to get inside the cell how might they move across the membrane

Answer 119

Chloride ions need to pass through the cell surface membrane to get inside the cell how might they move across the membrane

Using carrier proteins/channel proteins in the membrane

Question 120

The protein content of a typical cell membrane is around 50% in energy releasing organelles such as mitochondria demand rises to around 75% suggest a reason for this difference

Answer 120

The protein content of a typical cell membrane is around 50% in energy releasing organelles such as mitochondria demand rises to around 75% suggest a reason for this difference

Energy releasing organelles require lots of substances such as nutrients enzymes and ATP to travel across the membrane so some of these substances will require help from proteins to get across the membrane so these membranes will have a higher protein content

Question 121

A person removes some raspberries from the freezer and that have frozen solid and leaves them on a plate to defrost when he returns there is a red puddle on the plate around the fruit use your knowledge of cell membranes to explain what has happened

Answer 121

A person removes some raspberries from the freezer and that have frozen solid and leaves them on a plate to defrost when he returns there is a red puddle on the plate around the fruit use your knowledge of cell membranes to explain what has happened

Freezing the raspberries will have caused ice crystals to form and pierce the cell surface membranes, making the membrane highly permeable when they thawed this will have caused the red pigment to leak out of the raspberry cells as they defrosted

Question 122

An experiment was carried out to investigate the effect of increasing methanol concentration on the permeability of beetroot cell membranes
beetroot cubes were soaked in varying concentrations of methanol for a set amount of time then a colorimeter was used to read the absorbance of the liquid once the beetroot cubes had been removed the results of the experiment where are used to produce a graph

give four variables that should have been controlled in this experiment

Give two things that should be done with the colorimeter before its used to measure the absorbance of the liquid samples

Answer 122

An experiment was carried out to investigate the effect of increasing methanol concentration on the permeability of beetroot cell membranes
beetroot cubes were soaked in varying concentrations of methanol for a set amount of time then a colorimeter was used to read the absorbance of the liquid once the beetroot cubes had been removed the results of the experiment where are used to produce a graph

give four variables that should have been controlled in this experiment
The size of the beetroot cubes the beetroot the cubes came from the volume of methanol solution the cubes were soaked in and the temperature of the equipment and surroundings

Give two things that should be done with the colorimeter before its used to measure the absorbance of the liquid samples
It should be turned on and left for five minutes to stabilise and it should be Calibrated to 0 using a cuvette containing distilled water

Question 123

Why is the phospholipid bilayer described as fluid

Describe the movement of proteins within the bilayer

What is the glycoprotein

Explain the meaning of the term is hydrophilic and hydrophobic

Explain why a cell membrane is an affective barrier against water-soluble substances

Answer 123

Why is the phospholipid bilayer described as fluid
Because the phospholipids are constantly moving

Describe the movement of proteins within the bilayer
Some of the proteins are fixed in position, others may move sideways

What is the glycoprotein
A protein with a carbohydrate attached

Explain the meaning of the term is hydrophilic and hydrophobic
Hydrophilic means attracts water hydrophobic means repels water

Explain why a cell membrane is an affective barrier against water-soluble substances
The centre of the phospholipid bilayer is hydrophobic so the membrane doesn’t allow water-soluble substances through it

Question 124

How does the cell-surface membrane controls what enters and leaves the cell

Describe the role of cholesterol in a cell membrane

Answer 124

How does the cell-surface membrane controls what enters and leaves the cell
Some proteins in the membrane allow the passage of large or charged particles that would otherwise find it difficult to cross the membrane

Describe the role of cholesterol in a cell membrane
Cholesterol helps make the membrane less fluid and more stable it maintains shape of animal cells and creates a barrier to polar substances

Question 125

Briefly describe how you could investigate the effect of temperature on the permeability of the cell membranes

Answer 125

Briefly describe how you could investigate the effect of temperature on the permeability of the cell membranes

Cut equal sized beetroot cubes and place each cube in a test tube
add the same volume of water to each test tube 5 cm³ then place each test tube in a water bath set at different temperature (10, 20,30,40,50 degrees Celsius) and leave them for the same length of time
remove the beetroot cubes from each test tube and then use a colorimeter to measure the absorbance of the remaining liquid
this will indicate how much a pigment has been released by each beetroot cube and therefore how permeable the membrane is at each temperature tested

Question 126

The photograph shows Ink diffusing through a beaker of water explain what is happening to the ink molecules

Answer 126

The photograph shows Ink diffusing through a beaker of water explain what is happening to the ink molecules

The ink molecules are moving from an area of high concentration to an area of low concentration

Question 127

Carbon dioxide as a waste product of respiration and must be removed from cells how will each of the following affect the rate of diffusion of carbon dioxide across a cell surface membrane explain your answer in each case

(a) Increasing the thickness of the cell membrane
(b) Increasing the number of faults in the cell membrane
(c) Reducing the concentration of carbon dioxide outside of the cell

Answer 127

Carbon dioxide as a waste product of respiration and must be removed from cells how will each of the following affect the rate of diffusion of carbon dioxide across a cell surface membrane explain your answer in each case

(a) Increasing the thickness of the cell membrane
The distance the particles have to travel is further so the rate of diffusion will decrease

(b) Increasing the number of faults in the cell membrane
The surface area of the cell will increase so the rate of diffusion will increase

(c) Reducing the concentration of carbon dioxide outside of the cell
The concentration gradient will increase so the rate of diffusion will increase

Question 128

Simple diffusion and facilitated diffusion both move particles down the concentration gradient across the cell membrane suggest how you could determine whether a particle is being transported by simple or facilitated diffusion in an experimental setting explain your answer

Answer 128

Simple diffusion and facilitated diffusion both move particles down the concentration gradient across the cell membrane suggest how you could determine whether a particle is being transported by simple or facilitated diffusion in an experimental setting explain your answer

You could increase the concentration gradient of the particle and monitor the rate of diffusion facilitated diffusion requires proteins to transport particles across the cell membrane there are a fixed number of proteins in the membrane once all the proteins are in use increasing the concentration gradient won’t increase the rate of facilitated diffusion any further whereas increasing the concentration gradient will continue to increase the rate of simple diffusion

Question 129

Give three factors that affect the rate of simple diffusion

Briefly describe power carrier protein transports molecules across a cell membrane

What is the channel protein

Describe the role of channel proteins in the transport of particles across a cell membrane

Answer 129

Give three factors that affect the rate of simple diffusion
Concentration gradient, surface area, thickness of the exchange surface

Briefly describe power carrier protein transports molecules across a cell membrane
First, a large molecule attaches to a carrier protein in the membrane.then, the protein changes shape.this releases the molecule on the opposite side of the membrane

What is the channel protein
Channel proteins are proteins within the cell membrane that form pores

Describe the role of channel proteins in the transport of particles across a cell membrane
Channel proteins allow charged particles to pass through cell membrane via facilitated diffusion

Question 130

Explain how increasing the number of carrier and channel proteins in the membrane would affect the rate of facilitated diffusion

Answer 130

Explain how increasing the number of carrier and channel proteins in the membrane would affect the rate of facilitated diffusion

It would increase the rate of facilitated diffusion as it would allow more particles to be transported across the membrane at the same time

Question 131

Describe the net movement of water molecules in each of the following situations:

Human cheek cells with the water potential of -300 kPa are placed in a salt solution with the water potential of -325 kPa

Apple slices with the water potential of -750 kPa are placed in a beaker of pure water

Orange squash with the water potential of -450 kPa is sealed in a length of visking tubing and suspended in a solution of equal water potential

Answer 131

Describe the net movement of water molecules in each of the following situations:

Human cheek cells with the water potential of -300 kPa are placed in a salt solution with the water potential of -325 kPa
What are molecules will move from the cheek cells into the salt solution

Apple slices with the water potential of -750 kPa are placed in a beaker of pure water
Water molecules will move into the apple slices out of the beaker of water

Orange squash with the water potential of -450 kPa is sealed in a length of visking tubing and suspended in a solution of equal water potential
There will be no net movement of water molecules as the water potential in both solutions is the same so the solutions are isotonic

Question 132

Defined three factors that affect the rate of osmosis

Answer 132

Defined three factors that affect the rate of osmosis

The water potential gradient the thickness of the exchange surface and the surface area of the exchange surface (the larger the surface area of the faster the rate of osmosis)

Question 133

Describe an investigation that you could do to find the water potential of potato cells

Answer 133

Describe an investigation that you could do to find the water potential of potato cells

Cut equal size chips from a potato divide the chips into groups of three and measure the mass of each group
make up several different sucrose concentrations place each group of chips into a different sucrose solution and leave all the chips for the same length of time
remove the chips and measure the mass of each group again
record each groups percentage change in mass then make a calibration curve by plotting the percentage change in mass against the concentration of sucrose solution the group was in and read off the concentrationwhere the curve crosses the X axes
look up the water potential for that concentration of solution in for example a textbook to give you the water potential of the potato cells

Question 134

The thyroid gland needs iodide ions to make hormones so there is a higher concentration of iodide ions inside the thyroid cells than in the blood plasma the sodium iodide co-transporter is involved in transporting iodide ions into the thyroid gland
the concentration of sodium ions is higher in the blood plasma than in the thyroid gland

Which ion needs to be actively transported by the sodium iodide co-transporter explain your answer

Using your knowledge of transporters, describe and explain how active transport is carried out by the sodium iodide co-transporter

Answer 134

The thyroid gland needs iodide ions to make hormones so there is a higher concentration of iodide ions inside the thyroid cells than in the blood plasma the sodium iodide co-transporter is involved in transporting iodide ions into the thyroid gland
the concentration of sodium ions is higher in the blood plasma than in the thyroid gland

Which ion needs to be actively transported by the sodium iodide co-transporter explain your answer
The iodide ions because it needs to move from an area of low concentration to an area of higher concentration

Using your knowledge of transporters, describe and explain how active transport is carried out by the sodium iodide co-transporter
The co transporter binds to an iodide ion and the sodium ion
the sodium ion moves across the membrane into the thyroid gland down its concentration gradient
this moves Idoide ions across the membrane into the cell against its concentration gradient

Question 135

Describe the chemical reaction that occurs to release energy from ATP

Answer 135

Describe the chemical reaction that occurs to release energy from ATP

Hydrolysis reaction occurs which splits ATP into ADP and inorganic phosphate

Question 136

Describe how the following are used to transport substances across the cell membrane during active transport:

Carrier proteins and co-transporters

Answer 136

Describe how the following are used to transport substances across the cell membrane during active transport:

Carrier proteins and co-transporters

Carrier protein
A molecule attaches to a carrier protein in the membrane
the protein then changes shape and releases the molecule on the opposite side of the membrane
the process requires energy

Co-transporters
Call transporters bind twi molecules at a time the concentration gradient of one of the molecules is used to move the other molecule against its own concentration gradient

Question 137

Why are sodium ions important in the transport of glucose from the Ileum into the blood

Answer 137

Why are sodium ions important in the transport of glucose from the Ileum into the blood

Because sodium ions diffuse from the lumen of the Ileum into the intestinal epithelium cells down the concentration gradient, through a sodium-glucose co-transporter protein
at the same time the co-transporter carries glucose into the epithelium cell against a concentration gradient glucose is then able to diffuse into blood from the epithelial cell

Question 138

Will the rate of active transport increase or decrease with an increasing number of carrier proteins

Answer 138

Will the rate of active transport increase or decrease with an increasing number of carrier proteins

Increase

Question 139

What are antigens

Why do some antigens generate an immune response

Answer 139

What are antigens
The molecule found on the surface of cells that can generate an immune response when detected by the body

Why do some antigens generate an immune response
The immune system identifies them as foreign

Question 140

What is the function of helper T cells

Answer 140

What is the function of helper T cells

When activated by antigens presented by phagocytes helper T cells release chemical signals to activate phagocytes, cytotoxic T cells and B cells

Question 141

What is the function of plasma cells

Answer 141

What is the function of plasma cells

Function of plasma cells is to produce antibodies

Question 142

What is the difference between a cellular immune response and the humoral immune response

Answer 142

What is the difference between a cellular immune response and the humeral immune response

The cellular immune response involves the T cells and other immune cells they interact with for example phagocytes the humoural response involves B-cells, clonal selection and the production of monoclonal antibody

Question 143

Give three differences other than speed between primary and secondary immune response

Answer 143

Give three differences other than speed between primary and secondary immune response

The Primary response happens the first time a pathogen invades, the secondary response happens the second time a pathogen invades the primary response involves b and T cells the secondary response also involve memory cells there are symptoms with the primary response but not with the secondary response

Question 144

Define the term active and passive immunity

how do you vaccines give people immunity

what is heard immunity

described two issues surrounding the use of vaccinations

Answer 144

Define the term is active and passive immunity
Active immunity is the type of immunity you get when your immune system makes its own antibodies after being stimulated by an antigen
passive immunity is the type of immunity you get from being given antibodies made by a different organism your immune system doesn’t produce any antibodies of its own

how do you vaccines give people immunity
Vaccines contain antigens that cause your body to produce memory cells against a particular pathogen this makes you immune

what is heard immunity
Heard immunity is when un-vaccinated people are protected because the occurrence of the disease is reduced by the number of people who are vaccinated
described two issues surrounding the use of vaccinations

Question 145

What is antigenic variation and explain why you can become ill with the flu even if you’ve been infected by the influenza virus before

Answer 145

What is antigenic variation and explain why you can become ill with the flu even if you’ve been infected by the influenza virus before

Antigenic variation is when the antigens on the surface of the pathogen change
if the influenza virus undergoes antigenic variation
the memory cells produced from the first infection will not recognise the different antigens
the immune system has to carry out a primary response to the new antigens this takes time to get rid of the infection which is why you get ill again

Question 146

The scientist is using the indirect ELISA to test its patient for an allergy to gluten.
1st she coats a well plate with gluten protein.
she then adds the patient serum samples of three of the Wells.
she then washes the well plate and adds a secondary antibody that has an attached enzyme
the scientist washes the well plate again then adds a substrate solution

(A) Why is the well plate washed out after the secondary antibody is added

(B) The substrate will change colour if it reacts with the enzyme bound to the secondary antibody what would you expect the scientist to observe if the patient is allergic to the gluten protein explain your answer

(C) suggest why the scientist adds patients serum sample to more than one well

(D) Two control wells are used in this test
in one well antibodies specific to the gluten proteins are used instead of patient serum
in the other well a salt solution is used instead of patients serum
suggest what each of these controls are designed to show
state what would you expect the results of the test to be in each case

Answer 146

The scientist is using the indirect ELISA to test its patient for an allergy to gluten.
1st she coats a well plate with gluten protein.
she then adds the patient serum samples of three of the Wells.
she then washes the well plate and adds a secondary antibody that has an attached enzyme
the scientist washes the well plate again then adds a substrate solution

(A) Why is the wallplate washed out after the secondary antibody is added
To remove any unbound secondary antibodies so there won’t be a false positive result if there are no primary antibodies present

(B) The substrate will change colour if it reacts with the enzyme bound to the secondary antibody what would you expect the scientist to observe if the patient is allergic to the gluten protein explain your answer
The substrate will change colour, because there will have been primary antibodies to the gluten protein in the patient serum these will have bound to the gluten protein in the well and then the secondary antibody will have bound to them this means the enzyme that the substrate reacts with will be present in the well

(C) suggest why the scientist adds the patient serum sample to more than one well
To reduce the likelihood of getting a false result

(D) To control wells are used in this test
in one well antibodies specific to the gluten proteins are used instead of patient serum
in the other well a salt solution is used instead of patients serum
suggest what each of these controls are designed to show
state what would you expect the results of the test to be in each case
The control using antibodies shows a positive result it shows that the secondary antibody will bind to the gluten protein so the result will be a colour change the control using salt solution should show a negative result it shows that all unbound secondary antibody is removed by washing the wall plate so the results will be no colour change

Question 147

Describe how HIV replicates

Why can’t antibiotics be used against viruses

Answer 147

Describe how HIV replicates
The viral attachment protein attaches to a receptor molecule on the cell membrane of the host T helper cellThe capsid is then released into the cell where it uncoats and releases RNA into the cell cytoplasm in the cell reversed transcriptase is used to make up complimentary strand of DNA from the viral RNA
double-stranded DNA is made from this which is inserted into the human DNA
enzymes in the cell are used to make viral proteins from the inserted viral DNA
the viral proteins are assembled into new viruses which bud from the cell and go on to infect other cells

Why can’t antibiotics be used against viruses
Antibiotics are used to target bacterial enzymes and ribosomes, which are different to those in humans viruses do not have their own enzymes and ribosomes they use those found in the host so cannot be targeted in this way

Question 148

Describe the process of phagocytosis

Outline the main stages of the immune response after phagocytosis

Answer 148

Describe the process of phagocytosis
When a phagocyte recognises the antigens on the pathogen the cytoplasm of the phagocyte moves around the pathogen engulfing it the pathogen is now contained in a phagocytic vacuole inside the phagocyte a lysosome fuses with the phagocytic vacuole and the lysozymes inside the lysosome break down the pathogen

Outline the main stages of the immune response after phagocytosis
The phagocytes present foreign antigens from engulfed pathogens on their surface
receptor proteins on the surface of helper T cells bind to the antigens activating the T cells activated helper T cells release chemical signals that activate phagocytes cytotoxic T cells and B cells
when B cells which are covered in antibodies meet an antigen with a complimentary shape they bind to itThis along with chemical signals released from helper T cells activates the B cells this is clonal selection
the B cells then divide into plasma cells
the plasma cells then produce antibodies specific to the antigens

Question 149

Describe the structure of an antibody

Answer 149

Describe the structure of an Antibody
An Antibody has variable regions where the antigen binds
Each antigen has a different shaped variable region with a different tertiary structure
they also have a constant region that is the same in all antibodies
An antibody consists of light chains and heavy chains that are joined together by disulphide bridges

Question 150

Describe on ethical issues surrounding the use of monoclonal antibodies

Answer 150

Describe on ethical issues surrounding the use of monoclonal antibodies
Monoclonal antibodyies are made using animal cells and some people disagree with using animals this way

Question 151

The sense strand:

The antisense strand:

We read DNA through the .. because …

Answer 151

The sense strand: 5’ to 3’

The antisense strand: 3’ to 5’

We read DNA through the sense strand because it’s the template