B2 Part B

Question 1

What are enzymes and what are they made of?

Answer 1

Enzymes are substances that are produced naturally and act as a biological catalysts. They are made up of proteins.

Question 2

Define the term ‘catalyst’

Answer 2

A catalyst is a subctance which increases the speed of a reaction without being changed or used up

Question 3

Fill in the gaps:

Enzymes have a unique …….. that locks onto the substance involved in the reaction and usually they will only be able to catalyse ……… reaction.

Answer 3

Enzymes have a unique shape that locks onto the substance involved a reaction and usually they will only be able to catalyse one reaction.

Question 4

Which two factors will effect whether enzymes are working at their optimum? Draw the rate of reaction graph for each of these if it helps

Answer 4

• Temperature
• pH

Question 5

At what temperature do enzymes in the human body usually work best?

Answer 5

37°C

Question 6

If temperature is too high or pH is too high or low, what will happen to enzymes?

Answer 6

The bonds holding them together will break, destroying their unique shape and causing them to ‘denature’.

Question 7

What do digestive enzymes do to starch, proteins and fats?

Answer 7

Digestive enzymes break down big molecules of starch, proteins and fats into sugars, amino acids, glycerol and fatty acids because they are smaller and can therefore move into the body more easily.

Question 8

What does amylase do and where is it produced?

Answer 8

Amylase converts starch into sugars like maltose and dextrin.

It is made in the salivary glands, the pancreas and the small intestine.

Question 9

How does protease aid the digestive system and where is it created?

Answer 9

Protease breaks down proteins into amino acids and is made in the stomach (where it is better known as pepsin), the pancreas and the small intestine.

Question 10

What does lipase do to lipids and where in the body is it in effect?

Answer 10

Lipase converts lipids into glycerol and fatty acids, it is made in the pancreas and the small intestine.

Question 11

What are the two main purposes of bile?

Answer 11

1. To neutralise stomach acid
2. Emulsify fats (gives a bigger surface area for lipase to work on)

Question 12

List the 9 main parts of the digestive system

Answer 12

1. Salivary glands
2. Gullet (oesophagus)
3. Liver
4. Stomach
5. Gall bladder
6. Pancreas
7. Large intestine
8. Small intestine
9. Rectum

Question 13

What is the purpose of the salivary glands?

Answer 13

They produce amylase enzyme in the saliva to help break down food.

Question 14

List the three main functions of the stomach

Answer 14

1. It pummels the food with it’s muscular walls
2. Produces the protease enzyme, pepsin
3. Produces hydrochloric acid to kill bacteria and create the right pH for the protease enzyme to work

Question 15

What is produced in the liver, stored in the gall bladder and released into the small intestine?

Answer 15

Bile

Question 16

What does the pancreas do?

Answer 16

Produces protease, amylase and lipase enzymes. It releases these into the small intestine.

Question 17

What happens in the large intestine?

Answer 17

Excess water is absorbed from the food

Question 18

List the two functions of the small intestine

Answer 18

1. To make protease, amylase and lipase enzymes to complete digestion
2. To absorb digested food into the blood

Question 19

What is stored in the rectum?

Answer 19

Faeces (waste)

Question 20

Define the term ‘respiration’

Answer 20

Respiration is the process of releasing energy from glucose (which occurs in every cell)

Question 21

What is aerobic respiration and where (in cells) does it most often occur?

Answer 21

Respiration that needs oxygen and is the most efficent way to release energy from glucose, it usually happens in mitochondria.

Question 22

Give the word equation for aerobic respiration

Answer 22

Glucose + Oxygen ⇒ carbon dioxide + water + energy

Question 23

List the four main examples of how energy released by aerobic respiration is used in various life forms

Answer 23

1. To build up larger molecules from smaller ones (eg. proteins from amino acids)
2. To allow the muscles of animals to contract and enable movement
3. To maintain body temperature in mammals and bird
4. To build sugars, nitrates and other nutrients into amino acids and then into proteins in plants

Question 24

Why does excersise increase heart and breathing rate?

Answer 24

An increase in muscle activity requires more glucose and oxygen to be supplied, meaning extra CO₂ must be removed from the muscle cells and for this to happen blood has to flow at a faster rate.

Question 25

What is glucose sometimes stored as and where in the body? What can happen to this store during excersise?

Answer 25

Some glucose may be stored as glycogen, in each muscle’s individual store or the liver. During vigorous excersise stored glycogen can be converted back to glucose to provide more energy.

Question 26

What happens when a person excersises but their body can’t supply enough oxygen to their muscles?

Answer 26

Muscles will begin to perform anaerobic respiration (without oxygen) rather than aerobic.

Question 27

Give the word equation for anaerobic respiration

Answer 27

glucose ⇒ energy + lactic acid

Question 28

List three disadvantages of anaerobic respiration

Answer 28

• Lactic acid builds up in muscle, which creates a painful sensation
• It causes muscle fatigue so they stop contracting effectively.
• It releases less energy than aerobic respiration

Question 29

Anaerobic respiration leads to an ………………. debt.

Answer 29

Anaerobic respiration leads to an oxygen debt

Question 30

Why do you continue breathing hard for a while after you have stopped excersising?

Answer 30

Because the lungs, heart and blood couldn’t supply oxygen to muscles fast enough during excerise, a person will breathe hard even after they stop excersising to make up for it. Blood will flow through your muscles to remove lactic acid by oxidising it. While high levels of CO2 and lactic acid are detected in the blood by the brain, the pulse and breathing rate remain high.

Question 31

What type of enzymes are most commonly used in biological detergents and why?

Answer 31

Mainly protein and fat digesting enzymes (proteases and lipases) because they break down animal and plant matter, they’re ideal for removing stains like food or blood.

Question 32

Fill in the gaps: Biological detergents are more effective at working at …….. ………….. than other types of detergent (eg…….)

Answer 32

Biological detergents are more effective at working at low temperatures than other types of detergent (eg. 30°C)

Question 33

List three ways enzymes are used to change foods

Answer 33

1. Proteins in some baby foods are ‘pre-digested’ by proteases
2. Carbohydrases can turn starch syrup into sugar syrup
3. Glucose syrup can be turned into fructose syrup using isomerase enzyme - fructose is sweeter so less of it is needed, good for sliming foods and drinks.

Question 34

Give four advantages of using enzymes in industry

Answer 34

1. They are specific, so will only catalyse the reaction you want them to
2. They require lower temperatures, which saves energy and money
3. They work for a long time, so after the initial cost of buying them, they can be used continually.
4. They are biodegradable

Question 35

List four disadvantages of using enzymes in industry

Answer 35

1. Some people can develop allergies to them
2. They can be denatured even by a small increase in temperature
3. They are expensive to produce
4. Contamination of the enzyme with other substances can affect the reaction

Question 36

What does DNA stand for?

Answer 36

deoxyribonucleic acid

Question 37

Where is DNA found?

Answer 37

DNA can be found in the nucleus of animal and plant cells, in long molecules called chromosome.

Question 38

Fill in the gaps:

A gene is a …….. … ………… A gene will contain the instructions to make a specific protein. Cells make proteins by stringing ………… ……….. together in a particular order. Only 20 ……….. ……….. are used but they make up thousands of different proteins.

Answer 38

A gene is a section of DNA. A gene will contain the instructions to make a specific protein. Cells make proteins by stringing amino acids together in a particular order. Only 20 amino acids are used but they make up thousands of different proteins.

Question 39

DNA determines what proteins a cell produces, which in turn determines what?

Answer 39

DNA determines what proteins a cell produces, which in turn determines what type of cell it is.

Question 40

Describe the process of DNA (or genetic) fingerprinting in 4 steps

Answer 40

1. Isolation - separate the DNA from other tissues
2. Fragmentation - use an enzyme to break the DNA into short lengths
3. Separation - pass an electric current across a layer of gel which has the DNA fragments at one end. The fragments will move different distances across the gel. This is called gel electrophoresis
4. Comparison - match the pattern of fragments on the gel with other samples of DNA (eg. those collectes at a crime scene)

Question 41

Some people want there to be a national genetic database of everyone in the country so DNA found at a crime scene can be checked against the whole population. Give three reasons why someone might oppose this idea

Answer 41

1. It’s an invasion of privacy
2. It would be difficult to totally secure the data
3. Scientific problems - false positives can occue is errors are made or if the data is misinterpreted

Question 42

What is mitosis and when does it occur?

Answer 42

When a cell reproduces itself by splitting to form two identical offspring. This happens when plants and animals want to grow or to replace cells that have been damaged.

Question 43

How many copies do humans have of each chromosome?

Answer 43

2 (one from the mother, one from the father)

Question 44

Describe the process of mitosis in 4 steps

Answer 44

1. The DNA is copied and forms X-shaped chromosomes. Each ‘arm’ of the chromosome is an exact duplicate of the other.
2. The chromosomes line up at the centre of the cell and cell fibres pull them apart, two arms of each chromosome go to opposite sides of the cell.
3. Membranes form around each of the sets of chromosomes so that they become the nuclei of the new cell.
4. Lastly, the cytoplasm divides.

Question 45

What does meiosis produce?

Answer 45

Meiosis produces cells which have half the normal number of chromosomes.

Question 46

What are gametes?

Answer 46

Cells used in sexual reproduction that only have one copy of each chromosome (23 in total). Male and female gametes will fuse together to form the whole 46 chromosomes.

Question 47

Describe meiosis in 5 stages

Answer 47

1. The cell divides, duplicating its DNA so that one arm is an exact copy of the other.
2. In the first division, the chromosome pairs line up in the centre of the cell.
3. The pairs are then pulled apart, so that each new cell only has one copy of each chromosome. Some of the father’s and some of the mother’s chromosomes go into each new cell.
4. In the second division, the chromosomes line up and their arms are pulled apart.
5. At the end, you get four gametes with only a single set of chromosomes in it.

Question 48

What is so special about embryonic stem cells?

Answer 48

They can become any type of cell by differentiation.

Question 49

In most animal cells, the ability to …………….. is lost at an early stage, but lots of …….. cells don’t ever lose this ability

Answer 49

In most animal cells, the ability to differentiate is lost at an early stage, but lots of plant cells don’t ever lose this ability

Question 50

Name two places where stem cells can be found

Answer 50

• In early human embryos
• In adult bone marrow (although these stem cells aren’t so versatile)

Question 51

List a few ways stem cells can be used for medical purposes

Answer 51

• Bone marrow transplants can be used to treat blood diseases (eg. sickle cell anaemia)
• To replace faulty cells - eg. beating heart muscles (heart disease), insulin producing cells (diabetes), nerve cell (spinal chord injuries)

Question 52

How do doctors create cultures of one specific type of cell?

Answer 52

By changing the environment stem cells are grown in and therefore manipulating the differentiation. So far, this has been successful on occasion but lots more research is needed.

Question 53

Why might somebody oppose embryonic stem cell research?

Answer 53

They feel human embryos shouldn’t be used for experiments because each one is a potential human life.

Question 54

Give two arguments in favour of stem cell research

Answer 54

• Curing patients who already exist and are suffering is more important than the rights of embryos
• Embryos used in research are the unwanted ones anyway, who would otherwise be destroyed

Question 55

The 23rd pair of chromosomes in every human body cell is labelled either XX or XY - what does this control?

Answer 55

Gender

XY = Male

XX = Female

Question 56

How do the X and Y chromosomes enter sperm/egg cells?

Answer 56

When making sperm, the X and Y chromosomes are drawn apart in the first division in meiosis. There’s a 50% chance that each sperm gets either X or Y.

When making eggs, the original cell has two X chromosomes so all eggs have one X.

Question 57

Who was Gregor Mendel and of which area of biology did he provide the foundation?

Answer 57

An Austrian monk who trained in mathematics and natural history. On his garden plot at the monastery, he noted how chracteristics of plants were passed on from one generation to the next. He lived from 1822 - 1884 and the results of his work published in 1866 became the foundation of modern genetics.

Question 58

Which 3 important conclusions did Mendel reach?

Answer 58

1. Characteristics in plants are determined by “hereditary units”.
2. Hereditary units are passed on from both parents, one unit from each parent.
3. Hereditary units can be dominant or recessive - if an individual has both a dominant and recessive unit for a characteristic, the dominant will be expressed.

Note: We now know hereditary units to be genes byt in Mendel’s time, nobody knew anything about DNA or genes.

Question 59

What are ‘alleles’?

Answer 59

Alleles are different versions of the same gene.

Question 60

If an organism has two alleles for a particular gene that are the same, then it’s ……………. If it’s two alleles for a particular genes are different, then it’s …………………..

Answer 60

If an organism has two alleles for a particular gene that are the same, then it’s homozygous. If it’s two alleles for a particular genes are different, then it’s heterozygous.

Question 61

If two alleles in an organism are different then only one can determine what characteristic is present, this is called the …………….. gene, whereas the other is known as the ……………

How is a dominant gene indicated on a genetic diagram?

Answer 61

If two alleles in an organism are different then only one can determine what characteristic is present, this is called the dominant gene, whereas the other is known as the recessive.

A dominant gene is recognisable on a gentic diagram because it is symbolised by a capital letter.

Question 62

Draw a genetic diagramin which the mother has a dwarf gene and the fatehr has a tall gene

Question 63

What is cystic fibrosis caused by and why doesn’t everyone who carries the gene have the disorder?

Answer 63

A recessive allele, ‘f’, carried by about 1 person in 25.

Because it’s recessive, people with only one copy of the allele won’t have the disorder - they’re known as carriers. For a child to have cystic fibrosis, both parents must either be carriers or sufferers.

Question 64

What is Cystic Fibrosis?

Answer 64

Cystic Fibrosis is a genetic order of cell membranes, which resultes in the body producing a lot of sticky thick mucus in the air passaged and pancreas.

Question 65

What is Polydactyl?

Answer 65

Polydactyl is a genetic disorder where a baby is born with extra fingers or toes.

Question 66

What is Polydactyl caused by?

Answer 66

The disorder is caused by a dominant allele, ‘D’, and can therefore be inherited if just one parent carries the disease.

Question 67

How can genetic disorders be identified/prevented in IVF babies?

Answer 67

Before the embryos are implanted into a mothers womb it’s possible to remove a cell from each embryo and analyse it’s genes. Genetic disorders can be detected in this way and embryos with ‘good’ alleles can be implanted, and the ones with ‘bad’ alleles may be destroyed.

Question 68

Why might somebody disagree with embryonic screening? (4)

Answer 68

1. People might want to screen their embryos to pick the most ‘desirable’ ones
2. The rejected embryos (precious potential human lives) are destroyed
3. It implies people with genetic problems are ‘undesirable’ and could create prejudice.
4. Screening is expensive

Question 69

List 4 arguments for embryonic screening

Answer 69

1. It will reduce suffering
2. There are laws in place to stop it going so far
3. During IVF most embryos are destroyed anyway
4. Treating disorders costs the government a lot of money

Question 70

What are fossils?

Answer 70

Fossils are the remains of organisms (plants or animals) that are found preserved in rocks.

Question 71

Describe how fossils are created from gradual replacement

Answer 71

1. Things like teeth, shells and bones dont decay easily and therefore last for a long time when they’re buried
2. They’re eventually replaced by minerals as they decay, forming a rock like substance shaped like the original hard body part
3. Surrounding sediment also turns to rock, but the fossil stays distinct

Question 72

How is a fossil formed from a cast/impression?

Answer 72

When an organism is buried in a soft material like clay, the clay hardens around it and the organism decays, leaving a cast of itself. Similarly, footprints can be pressed into these materials when soft, leaving an impression when it hardens.

Question 73

List 3 examples of where fossil preservation can occur where no decay happens

Answer 73

1. In amber (a clear yellow ‘stone’ made from fossilised resin) and tar pits there’s no oxygen or moisture so decay microbes can’t survive and dead organisms may be preserved.
2. In glaciers, it’s too cold for decay microbes to work.
3. Peat bogs are too acidic for decay microbes.

Question 74

Give 6 reasons why a species might go extinct

Answer 74

1. If the organisms environment changes quickly eg. destruction of habitat
2. If a new predator kills them all
3. If a new disease takes hold
4. If they can no longer compete with another species for food
5. If a catastrophic event occurs (eg. a volcanic eruption or collision with an asteroid)
6. If a new species develops (speciation)

Question 75

What is speciation and when does it occur?

Answer 75

Speciation is the development of a new species, it occurs when populations of the same species become so different that they can no longer breed together to produce fertile offspring.

Question 76

What is isolation?

Answer 76

Isolation is when popualtions of a species are separated.

Question 77

When does isolation of species occur? Try and explain it in 3 main steps

Answer 77

1. Isolation between two populations of the same species will happen predominantly due to there being a physical barrier (eg. floods, earthquakes, mountain ranges) between the two.
2. Conditions on eitherside of the barrier will be slightly different and therefore each population will develop different characteristics, due to natural selection.
3. Eventually individuals from a popualtion will have changed so much that they won’t be able to breed with the other and it is then that the two groups will have become separate species.