Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

A-Level Biology (Paper 1) > 1.1 Biological Molecules > Flashcards

1.1 Biological Molecules Flashcards

1
Q

What are Monomers?

A

Monomers are the smaller units from which larger molecules are made

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are Polymers?

A

Polymers are molecules made from a large number of monomers joined together in a chain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are Organic Compounds?

A

Compounds containing Carbon and Hydrogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How are Carbon Atoms are key to the organic compounds?

A
  • Each carbon atom can form four covalent bonds – this makes the compounds very stable (as covalent bonds are so strong they require a large input of energy to break them)
  • Carbon atoms can form covalent bonds with oxygen, nitrogen and sulfur
  • Carbon atoms can bond to form straight chains, branched chains or rings
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Define Polymerisation

A

This is the process by which Monomers join together to form a long chain of molecules called a Polymer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Whar are Carbohydrates?

A
  • Carbohydrates are one of the main carbon-based compounds in living organisms
  • All molecules in this group contain C, H and O
  • As H and O atoms are always present in the ratio of 2:1 (eg. water H2O, which is where ‘hydrate’ comes from) they can be represented by the formula Cx (H2O)y
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the Three types of Carbohydrates?

A
  • Monosaccharides
  • Disaccharides
  • Polysaccharides
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Define a Covalent Bond

A

The sharing of two or more electrons between two atoms

  • The electrons can be shared equally forming a nonpolar covalent bond or unequally (where an atom can be more electronegative δ-) to form a *polar covalent bond*
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Define a Condensation Reaction

A

A condensation reaction occurs when monomers combine together by covalent bonds to form polymers (polymerisation) or macromolecules (lipids) and water is removed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Define a Hydrolysis Reaction

A
  • Hydrolysis means ‘lyse’ (to break) and ‘hydro’ (with water)
  • 2 molecules separated
  • Breaking a chemical bond
  • Using a water molecule
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What defines wether a sugar is Reducing or Non-Reducing?

A

This classification is dependent on their ability to donate electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are Reducing Sugars?

A
  • Reducing sugars can donate electrons (the carbonyl group becomes oxidised), the sugars become the reducing agent

Carbonyl : C = O

Thus reducing sugars can be detected using Benedict’s test as they reduce the soluble copper sulphate to insoluble brick-red copper oxide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Give examples of Reducing Sugars:

A
  • Glucose
  • Fructose
  • Galactose

Fructose and galactose have the same molecular formula as glucose however they have a different structural formula

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Can non-reducing sugars donate electrons?

A

No, therefore they cannot be oxidised

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Give an example of a non-reducing sugar:

A

Sucrose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How can a non-reducing sugar be detected?

A

To be detected non-reducing sugars must first be hydrolysed to break the disaccharide into its two monosaccharides before a Benedict’s test can be carried out

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Define ATP

A
  • A nucleotide deriverative
  • Which is produced during respiration / photosynthesis and acts as an energy carrier
  • The hydrolysis of ATP leads to the formation of adenosine diphosphate (ADP) and inorganic phosphate
  • With the release of energy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is a Monosaccharide?

A
  • This is a carbohydrate monomer, or simple sugar that cannot be hydrolysed further (eg glucose)
  • Monosaccharides can join to produce dissaccharides (eg maltose and polysaccharides - eg starch)

Single sugar Molecules

Mono - One Saccharide - Sugar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Which only elements to Carbohydrates contain?

A

Carbon, Hydrogen and Oxygen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are Hexose Sugars?

A

Sugars with 6 Carbon atoms

Pentose - 5 (eg Ribose)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the formula of Glucose?

A

C6H12O6

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the properties of Monosaccharides?

A
  • They are soluble in water - OH Group can form hydrogen bonds with water molecules (Hydrophilic)

Hydrophilic - Means Water Loving - these type of molecules all dissolve in water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are the two structural forms that Glucose exists in?

A
  • Alpha (α) glucose
  • Beta (β) glucose

It is therefore known as an Isomer

Isomer - Organic Molecules that have the same molecular formula, but different structural formulas which results in different properties

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Straight chain and ring structural formula of alpha & beta glucose:

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Isomer | Alpha (α) glucose Diagram

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Isomer | Beta (β) glucose

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Define a Polysaccharide

A
  • Made from many sugar units that are formed by a condensation reaction
  • Monosaccharides are joined by a glycosidic bond
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Is Starch formed from (α) |(β) Glucose?

A

(α)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Is Glycogen formed from (α) |(β) Glucose?

A

(α)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Is Cellulose formed from (α) |(β) Glucose?

A

(β)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Simplified Structure of Glucose Diagram:

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Define Osmolarity

A
  • This is the total number of solute particles per litre
  • It is a measure of the concentration of a solution
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

How are Disaccharides and Polysaccharides formed?

A
  • Disaccharides and polysaccharides are formed when two hydroxyl (-OH) groups (on different saccharides) interact to form a strong covalent bond called the glycosidic bond (the oxygen link that holds the two molecules together)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

How are glycosidic bonds formed and what is lost as a result?

A
  • Glycosidic bonds are formed by condensation reactions
  • Every glycosidic bond results in one water molecule being lost
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Types of Glycosidic Bonds Table:

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Give Examples of hydrolytic reactions

A
  • Digestion of food in the alimentary tract
  • The breakdown of stored carbohydrates in muscle and liver cells for use in cellular respiration
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

How is the Glycosidic Bond broken?

A

When water is added in a hydrolysis (meaning ‘hydro’ - with water and ‘lyse’ - to break) reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What do we produce when we react together two Alpha Glucose molecules?

A
  • Maltose
  • And Water
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What is Sucrose formed from?

A
  • Glucose
  • Fructose
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What is Lactose formed from?

A
  • Glucose
  • Galactose
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

How do you calculate the chemical formula of a Disaccharide?

A

To calculate the chemical formula of a disaccharide, you add all the carbons, hydrogens and oxygens in both monomers then subtract 2x H and 1x O (for the water molecule lost)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Give 3 Examples of Disaccharides

A
  • Maltose
  • Sucrose
  • Lactose

All three of the common examples above have the formula C12H22O11

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

What are the Monosaccharide components of Maltose?

A

Alpha (α) glucose | Alpha (α) glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

What are the Monosaccharide components of Sucrose?

A

Alpha (α) glucose | Fructose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

What are the Monosaccharide components of Lactose?

A

Alpha (α) glucose | Galactose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

What are Polysaccharides?

A

Polysaccharides are macromolecules that are polymers formed by many monosaccharides joined by glycosidic bonds in a condensation reaction to form chains

These chains may be:
* Branched or unbranched
* Folded (making the molecule compact which is ideal for storage e.g. starch and glycogen)
* Straight (making the molecules suitable to construct cellular structures e.g. cellulose) or coiled

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

Why are Starch and Glycogen good storage polysaccharides?

A
  • They are Compact (so large quantities can be stored)
  • Insoluble (so will have no osmotic effect, unlike glucose which would lower the water potential of a cell causing water to move into cells, plant cells would then have to have thicker cell walls, and animal cells would burst under the increased pressure)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

Describe the chemical reactions involved in the conversion of polymers to
monomers and monomers to polymers. (5)

Give two named examples of polymers and their associated monomers to
illustrate your answer.

A
  • A condensation reaction joins monomers together and forms a (chemical) bond and releases water
  • A hydrolysis reaction breaks a (chemical) bond between monomers and uses water

suitable examples include amino acid and polypeptide, protein, enzyme,
antibody or specific example
* nucleotide and polynucleotide, DNA or RNA
* Alpha glucose and starch/glycogen
* Beta glucose and cellulose.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

What is a monomer? (1)

A

(a monomer is a smaller / repeating) unit / molecule from which larger molecules / polymers are made

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

What are the two different polysaccharides of starch?

A
  • Amylopectin (70 - 90% of starch)
  • Amylose (10 - 30% of starch)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

What is the structure of Amylose?

A
  • Unbranched helix-shaped chain with 1,4 glycosidic bonds between α-glucose molecules (Amylose is a polymer of Alpha (α) glucose molecules)
  • The helix shape enables it to be more compact and thus it is more resistant to digestion - Hydrogen bonds form along the glucose molecules along the chain
  • Each bond forms in a condesation reaction, producing water as a by-product
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

How is Glucose extremely soluble in water?

A
  • It contains a large number of Hydroxyl (OH) Groups
  • Hydroxyl groups are polar due to the small negative charge on the oxygen atom and the small positive charge on the hydrogen atom
  • This means that hydroxyl groups can form Hydrogen bonds with water molecules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

Why does starch take longer to digest than Glucose?

A

Due to the many monomers in a starch molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

What is the structure of Amylopectin?

A

*1,4 glycosidic bonds between α-glucose molecules but also 1,6 glycosidic bonds form between glucose molecules creating a branched molecule (Every 25-30 Glucose Molecules)
* The branches result in many terminal glucose molecules that can be easily hydrolysed for use during cellular respiration or added to for storage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

How is the structure of Starch related to its function?

A
  • Amylose forms a tight helix - This makes starch compact
  • Starch is also insoluble in water - starch does not cause water to enter the cell via osmosis
  • When cells need glucose, enzymes are used to break the glycosidic bonds within starch (hydrolysis - requires water)
  • The enzymes that break down starch act at the end of the molecules - because amylopectin has a large number of branches, this means it has a large number of ends - because of this, the enzymes can break down starch rapidly
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

What is glycogen?

A

Glycogen is the storage polysaccharide of animals and fungi, it is highly branched and not coiled

The major stores of Glycogen are found in the liver and muscle cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

What is the structure and function of Glycogen?

A
  • Glycogen is the storage polysaccharide of animals and fungi, it is highly branched and not coiled
  • Liver and muscles cells have a high concentration of glycogen, present as visible granules, as the cellular respiration rate is high in these cells (due to animals being mobile)
  • Glycogen is more branched than amylopectin making it more compact which helps animals store more
  • The branching enables more free ends where glucose molecules can either be added or removed allowing for condensation and hydrolysis reactions to occur more rapidly – thus the storage or release of glucose can suit the demands of the cell
  • Glycogen is also insoluble in water - does not draw water into cells via osmosis
  • Being a large molecule, glycogen cannot diffuse out of a cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

Summary of Storage Polysaccharides Table:

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

Describe the structure of α-glucose:

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

Describe the difference between the structure of α-glucose and β-glucose:

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

What are disaccharides and how are they formed?

A
  • Two monosaccharides joined together with a glycosidic bond
  • Formed by a condensation reaction, releasing a water molecule
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

Draw a diagram to show how two monosaccharides are joined together

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

What are polysaccharides and how are they formed?

A
  • Many monosaccharides joined together with glycosidic bonds
  • Formed by many condensation reactions, releasing water molecules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

Describe the basic function and structure of starch and glycogen:

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

Explain how the structures of starch and glycogen relate to their functions

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

Describe the basic function and structure of cellulose:

A
  • It is a polymer consisting of long chains of β-glucose joined together by 1,4 glycosidic bonds
  • As β-glucose is an isomer of α-glucose to form the 1,4 glycosidic bonds consecutive β-glucose molecules must be rotated 180° to each other

Due to the inversion of the β-glucose molecules many hydrogen bonds form between the long chains giving cellulose it’s strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

Explain how the structure of cellulose relates to its function:

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

Reducing & non-reducing sugars table:

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

Why do we need to add an acid when testing for non-reducing sugars?

A
  • The addition of acid will hydrolyse any glycosidic bonds present in any carbohydrate molecules
  • The resulting monosaccharides left will have an aldehyde or ketone functional group that can donate electrons to copper (II) sulfate (reducing the copper), allowing a precipitate to form
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

Describe the biochemical test for starch:

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

Suggest another method to measure the quantity of sugar in a solution:

A

A colourimeter is used to obtain quantitative data that can be plotted to create a calibration curve to be used to find unknown concentrations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

What is a Colorimeter?

A

A colorimeter is an instrument that beams a specific wavelength (colour) of light through a sample and measures how much of this light is absorbed by the sample

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

Define a Qualitative test:

A

Indicates if a substance is present or absent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

Define a Quantitative test:

A

Allows for the concentration of a substance present to be determined

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

A biochemical test for reducing sugar produces a negative result with raffinose solution. Describe a biochemical test to show that raffinose solution contains a non-reducing sugar (3)

A
  • Heat with acid and neutralise
  • Heat with Benedict’s (solution)
  • Red precipitate/colour
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

A student carried out the Benedict’s test. Suggest a method, other than
using a colorimeter, that this student could use to measure the quantity of reducing sugar in a solution.

A
  • Filter and dry (the precipitate)
  • Find mass/weight
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

Glycogen and cellulose are both carbohydrates.
Describe two differences between the structure of a cellulose molecule and a glycogen molecule (2)

A
  • Cellulose is made up of β-glucose (monomers) and glycogen is made up of α-glucose (monomers);
  • Cellulose molecule has straight chain and glycogen is branched;
  • glycogen has 1,4- and 1,6- glycosidic bonds and cellulose has only 1,4- glycosidic bonds
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
78
Q

Describe the structure of glycogen (2)

A
  • Polysaccharide of α-glucose
  • (Joined by) glycosidic bonds
  • Branched structure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
79
Q

Suggest how glycogen acts as a source of energy (2)

A
  • Hydrolysed (to glucose)
  • Glucose used in respiration
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
80
Q

Explain one way in which starch molecules are adapted for their function in plant cells (2)

A
  • Insoluble - Doesn’t affect water potential
  • Helical - Compact
  • Large molecule - Cannot leave cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
81
Q

Explain how cellulose molecules are adapted for their function in plant cells (3)

A
  • Long and straight chains
  • Become linked together by many hydrogen bonds to form fibrils
  • Provide strength (to cell wall)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
82
Q

Give two ways in which the structure of starch is similar to cellulose (2)

A
  • Are polymers / polysaccharides / are made of monomers / of monosaccharides
  • Contain glucose / carbon, hydrogen and oxygen
  • Contain glycosidic bonds
  • Have 1−4 links
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
83
Q

Give two ways in which the structure of starch is different from cellulose (2)

A
  • Starch Contains α / alpha glucose
  • Starch is Helical / coiled / compact / branched / not straight
  • Starch has no (micro / macro) fibres / fibrils.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
84
Q

Describe how you would test a piece of food for the presence of lipid (2)

A
  • Dissolve in alcohol, then add water;
  • White emulsion shows presence of lipid.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
85
Q

Name the type of reaction that joins monosaccharides together (1)

A

Condensation (reaction)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
86
Q

Name two groups of lipid

A
  • Triglycerides
  • Phospholipids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
87
Q

Describe the structure of a fatty acid (RCOOH)

A
  • Variable R-group - hydrocarbon chain (saturated or unsaturated)
  • -COOH = carboxyl group
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
88
Q

Describe the difference between saturated and unsaturated fatty acids

A
  • Saturated: no C=C double bonds in hydrocarbon chain; all carbons fully saturated with hydrogen
  • Unsaturated: one or more C=C double bond in hydrocarbon chain (creating bend / kink)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
89
Q

What are the properties of Lipids?

A
  • Macromolecules which contain carbon, hydrogen and oxygen atoms.
  • However, unlike carbohydrates lipids contain a lower proportion of oxygen
  • Non-polar and hydrophobic (insoluble in water)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
90
Q

What are the monomers of Triglycerides?

A
  • Glycerol
  • Fatty Acids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
91
Q

What is the shorthand chemical formula for a fatty acid?

A

RCOOH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
92
Q

In what two ways can fatty acids vary?

A
  • Length of the hydrocarbon chain (R group)
  • The fatty acid chain (R group) may be saturated or unsaturated
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
93
Q

Define a Mono-Unsaturated Fatty Acid:

A

This is a fatty acid which possesses a carbon chain with a single double bond between fatty acids

  • If H atoms are on the same side of the double bond they are cis-fatty acids and are metabolised by enzymes
  • If H atoms are on opposite sides of the double bond they are trans-fatty acids and cannot form enzyme-substrate complexes, therefore, are not metabolised. They are linked with coronary heart disease
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
94
Q

Define a Poly-Unsaturated Fatty Acid:

A

These are fatty acids which possess a carbon chain with many double bonds between carbon atoms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
95
Q

Describe how triglycerides form

A
  • 1 glycerol molecule and 3 fatty acids
  • Condensation reaction
  • Removing 3 water molecules
  • Forming 3 ester bonds
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
96
Q

Explain how the properties of triglycerides are related to their structure:

Function: energy storage

A
  • High ratio of C-H bonds to carbon atoms in hydrocarbon chain - So used in respiration to release more energy than same mass of carbohydrates
  • Hydrophobic / non-polar fatty acids so insoluble in water (clump together as droplets)- So no effect on water potential of cell (or can be used for waterproofing)

They store more energy per gram due to their hydrocarbon chains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
97
Q

Describe the difference between the structure of triglycerides and phospholipids:

A

One of the fatty acids of a triglyceride is substituted by a phosphate-containing group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
98
Q

What are Phospholipids?

A
  • Phospholipids are the major components of cell surface membranes. They have fatty acid tails that are hydrophobic and a phosphate head, that is hydrophilic, attached to a glycerol molecule.
  • They form a bilayer in cell membrane, allowing diffusion of lipid-soluble (non polar) or very small substances and restricting movement of water-soluble (polar) or larger substances
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
99
Q

Why are Phospholipids described as amphipathic?

A

they have both hydrophobic and hydrophilic parts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
100
Q

Describe how the properties of phospholipids relate to their structure

Function: form a bilayer in cell membrane, allowing diffusion of lipid-soluble (non-polar) or very small substances and restricting movement of water-soluble (polar) or larger substances

A
  • Phosphate heads are hydrophilic
  • Attracted to water so point to water (aqueous environment) either side of membrane
  • Fatty acid tails are hydrophobic
  • Repelled by water so point away from water / to interior of membrane
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
101
Q

Describe the test for lipids

A
  • Add ethanol, shake (to dissolve lipids), then add water
  • Positive = milky white emulsion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
102
Q

Name the group represented by COOH (1)

A

Carboxyl

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
103
Q

Describe how you would test for the presence of a lipid in a liquid sample of food (2)

A
  • Add ethanol/alcohol then add water and shake/mix
  • White/milky (emulsion)

NOT Cloudy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
104
Q

Describe how a triglyceride molecule is formed (3)

A
  • One glycerol and three fatty acids
  • Condensation (reactions) and removal of three molecules of water
  • Ester bond(s) (formed)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
105
Q

Describe how an ester bond is formed in a phospholipid molecule (2)

A
  • Condensation (reaction)
  • Between of glycerol and fatty acid
  • Loss of water
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
106
Q

Describe / draw the general structure of an amino acid

A
  • COOH = carboxyl group
  • R = variable side chain / group
  • H2N = amine group
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
107
Q

What are the monomers of protiens?

A

Amino Acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
108
Q

How many amino acids are common in all organisms? How do they vary?

A

The 20 amino acids that are common in all organisms differ only in their side group (R)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
109
Q

Describe how amino acids join together

A
  • Condensation reaction
  • Removing a water molecule
  • Between carboxyl / COOH group of one
  • and amine / NH2 group of another
  • Forming a peptide bond
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
110
Q

What is a Dipeptide?

A

2 amino acids joined together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
111
Q

What is a Polypeptide?

A

Many amino acids joined together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
112
Q

How can we use chromatography to spearate a mixture of amino acids and identify their components? (Diagram)

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
113
Q

Describe the primary structure of a protein

A

Sequence of amino acids in a polypeptide chain, joined by peptide bonds

The specific order of amino acids in a polypeptide

  • Helps determine the final 3D structure of the protien molecule
  • The shape of a protien is critical for its function
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
114
Q

Describe the secondary structure of a protein

A
  • Folding (repeating patterns) of polypeptide chain eg. alpha helix / beta pleated sheets
  • Due to hydrogen bonding between amino acids
  • Between NH (group of one amino acid) and C=O (group)

  • C = O (Oxygen atoms have a small negative charge)
  • N - H (Hydrogen atoms have a small positive charge)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
115
Q

Describe the tertiary structure of a protein

A
  • 3D folding of polypeptide chain
  • Due to interactions between amino acid R groups (dependent on sequence of amino acids)
  • Forming hydrogen bonds, ionic bonds and disulfide bridges

The active site on an enzyme depends on the protien forming a very specific teritary structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
116
Q

Describe the quaternary structure of a protein

A
  • More than one polypeptide chain (subunits), working together as a large molecules
  • Formed by interactions between polypeptides
  • (hydrogen bonds, ionic bonds, disulfide bridges)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
117
Q

Describe the test for proteins

A
  • Add biuret reagent (sodium hydroxide + copper (II) sulphate)
  • Positive result = purple / lilac colour (negative stays blue) → indicates presence of peptide bonds
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
118
Q

Within tertiary structured proteins are the following bonds:

A
  • Strong covalent disulfide
  • Weak hydrophobic interactions
  • Weak hydrogen
  • Ionic
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
119
Q

What are Disulfide bonds?

A
  • Disulfide bonds are strong covalent bonds that form between two cysteine R groups (as this is the only amino acid with an available sulfur atom in its R group)
  • These bonds are the strongest within a protein, but occur less frequently, and help stabilise the proteins
  • These are also known as disulfide bridges
  • Can be broken by reduction

Disulfide bonds are common in proteins secreted from cells eg. insulin

120
Q

How do Ionic bonds form within tertiary structures of proteins?

A
  • Ionic bonds form between positively charged (amine group -NH3+) and negatively charged (carboxylic acid -COO-) R groups
  • Ionic bonds are stronger than hydrogen bonds but they are not common
  • These bonds are broken by pH changes
121
Q

How do Hydrogen bonds form within tertiary structures of proteins?

A

Hydrogen bonds form between strongly polar R groups. These are the weakest bonds that form but the most common as they form between a wide variety of R groups

122
Q

How do enzymes act as
biological catalysts?

A
  • Each enzyme lowers activation energy of reaction it catalyses
  • To speed up rate of reaction

Enzymes catalyse a wide range of intracellular and extracellular reactions that determine structures and functions from cellular to whole-organism level.

123
Q

Describe the induced-fit model of enzyme action

A
  • Substrate binds to (not completely complementary) active site of enzyme
  • Causing active site to change shape (slightly) so it is complementary to substrate
  • So enzyme-substrate complex forms
  • Causing bonds in substrate to bend / distort, lowering activation energy
124
Q

Describe how models of enzyme action have changed over time

A
  • Initially lock and key model (now outdated)
  • Active site a fixed shape, complementary to one substrate
  • Now induced-fit model
125
Q

Explain the specificity of enzymes

A
  • Specific tertiary structure determines shape of active site
    Dependent on sequence of amino acids (primary structure)
    Active site is complementary to a specific substrate
  • Only this substrate can bind to active site, inducing fit and forming an enzyme-substrate complex
126
Q

Describe and explain the effect of enzyme concentration on the rate of enzyme-controlled reactions

A
  • As enzyme conc. increases, rate of reaction increases
  • Enzyme conc. = limiting factor (excess substrate)
  • More enzymes so more available active sites
  • So more enzyme-substrate (E-S) complexes form
  • Substrate conc. = limiting factor (all substrates in use)
127
Q

Describe and explain the effect of substrate concentration on the rate of enzyme-controlled reactions

A
  • As substrate conc. increases, rate of reaction increases
  • Substrate conc. = limiting factor (too few enzyme molecules to occupy all active sites)
  • More E-S complexes form
  • At a certain point, rate of reaction stops increasing / levels off
  • Enzyme conc. = limiting factor
  • As all active sites saturated / occupied (at a given time)
128
Q

Describe and explain the effect of temperature on the rate of enzyme-controlled reactions

A
  • As temp. increases up to optimum, rate of reaction increases
  • More kinetic energy
  • So more E-S complexes form
  • As temp. increases above optimum, rate of reaction decreases
    Enzymes denature - tertiary structure and active site change shape
  • As hydrogen / ionic bonds break
  • So active site no longer complementary
  • So fewer E-S complexes form
129
Q

Describe and explain the effect of pH on
the rate of enzyme-controlled reactions

A
  • As pH increases / decreases above / below an optimum, rate of reaction decreases
    Enzymes denature - tertiary structure and active site change shape
  • As hydrogen / ionic bonds break
  • So active site no longer complementary
  • So fewer E-S complexes form
130
Q

Describe and explain the effect of concentration of competitive inhibitors on the rate of enzyme-controlled reactions

A
  • As concentration of competitive inhibitor increases, rate of reaction decreases
  • Similar shape to substrate
  • Competes for / binds to / blocks active site
  • So substrates can’t bind and fewer E-S complexes form
  • Increasing substrate conc. reduces effect of inhibitors
  • (dependent on relative concentrations of substrate and inhibitor)
131
Q

Describe and explain the effect of concentration of
non-competitive inhibitors on the rate of enzyme-controlled reactions

A
  • As concentration of non-competitive inhibitor increases, rate of reaction decreases
  • Binds to site other than the active site (allosteric site)
  • Changes enzyme tertiary structure / active site shape
    So active site no longer complementary to substrate
    So substrates can’t bind so fewer E-S complexes form
    Increasing substrate conc. has no effect on rate of reaction as change to active site is permanent
132
Q

What are Intracellular Enzymes?

A

Produced and function inside the cell

133
Q

What are Extracellular enzymes?

A

Secreted by cells and catalyse reactions outside cells (eg. digestive enzymes in the gut)

134
Q

Define a catabolic enzyme reaction

A
  • Catabolic reactions involve the breakdown of complex molecules into simpler products, which happens when a single substrate is drawn into the active site and broken apart into two or more distinct molecules
  • Examples of catabolic reactions include cellular respiration and hydrolysis reactions
135
Q

Define an anabolic enzyme reaction

A
  • Anabolic reactions involve the building of more complex molecules from simpler ones by drawing two or more substrates into the active site, forming bonds between them and releasing a single product
  • Examples of anabolic reactions include protein synthesis and photosynthesis
136
Q

How can we find the pH If the hydrogen ion (H+) concentration of a solution is known?

137
Q

Describe the basic functions of DNA in all living cells

A

Holds genetic information which codes for polypeptides (proteins)

138
Q

Describe the basic functions of RNA in all living cells

A

Transfers genetic information from DNA to ribosomes

139
Q

Describe the induced-fit model of enzyme action and how an enzyme acts as a catalyst (3)

A
  • Substrate binds to the active site/enzyme
  • Active site changes shape (slightly) so it is complementary to substrate
  • Reduces activation energy;
140
Q

A competitive inhibitor decreases the rate of an enzyme-controlled reaction. Explain how. (3)

A
  • Inhibitor similar shape to substrate
  • Fits/binds to active site
  • Prevents/reduces enzyme-substrate complex forming
141
Q

Describe how the structure of a protein depends on the amino acids it
contains (5)

A
  • Structure is determined by (relative) position of amino acid/R group/interactions;
  • Primary structure is sequence/order of amino acids;
  • Secondary structure formed by hydrogen bonding (between amino acids)
  • Tertiary structure formed by interactions (between R groups)
  • Creates active site in enzymes
  • Quaternary structure contains >1 polypeptide chain
142
Q

Explain how the active site of an enzyme causes a high rate of reaction. (3)

A
  • Lowers activation energy
  • Induced fit causes active site (of enzyme) to change shape
  • (So) enzyme-substrate complex causes bonds to form/break
143
Q

Describe a biochemical test to confirm the presence of protein in a solution. (2)

A
  • Add biuret (reagent)
  • (Positive result) purple/lilac
144
Q

Describe two other ways in which all dipeptides are similar and one way in which they might differ (3)

A

Similarities
* Amine/NH2 (group at end)
* Carboxyl/COOH (group at end)
* Two R groups
* All contain C and H and N and O
Differences
* Variable/different R group

145
Q

Describe how a non-competitive inhibitor can reduce the rate of an enzyme-controlled reaction. (3)

A
  • Attaches to the enzyme at a site other than the active site (Accept attaches to allosteric/inhibitor site)
  • Changes (shape of) the active site
  • (So active site and substrate) no longer complementary so less/no substrate can fit/bind
146
Q

Describe how a peptide bond is formed between two amino acids to form a dipeptide (2)

A
  • Condensation (reaction) / loss of water
  • Between amine / NH2 and carboxyl / COOH
147
Q

The secondary structure of a polypeptide is produced by bonds between amino acids. Describe how. (2)

A
  • Hydrogen bonds
  • Between NH (group of one amino acid) and C=O (group)
148
Q

Two proteins have the same number and type of amino acids but different tertiary structures. Explain why. (2)

A
  • Different sequence of amino acids
  • Different primary structure
  • Forms ionic / hydrogen / disulfide bonds in different places
149
Q

Formation of an enzyme-substrate complex increases the rate of reaction. Explain how (2)

A
  • Reduces activation energy
  • Due to bending bonds
150
Q

Draw the general structure of an amino acid. (1)

151
Q

Maltose is hydrolysed by the enzyme maltase.
Explain why maltase catalyses only this reaction. (3)

A
  • Active site (of enzyme) has (specific) shape / tertiary structure / active site complementary to substrate / maltose;
  • (Only) maltose can bind / fit
  • To form enzyme substrate complex
152
Q

Give one function of lysosomes (1)

A

Break down cells / cell parts

153
Q

Name the two types of molecule from which a ribosome is made

A

RNA and proteins

154
Q

Draw and label a DNA nucleotide

155
Q

Draw and label a RNA nucleotide

156
Q

Describe the differences between a DNA nucleotide and an RNA nucleotide

157
Q

Describe how nucleotides join together to form polynucleotides

A
  • Condensation reactions, removing water molecules
  • Between phosphate group of one nucleotide and deoxyribose/ribose of another
  • Forming phosphodiester bonds
158
Q

Why did many scientists initially doubt that DNA carried the genetic code?

A

The relative simplicity of DNA - chemically simple molecule with few components

159
Q

Describe the structure of DNA

A
  • Polymer of nucleotides (polynucleotide)
  • Each nucleotide formed from deoxyribose, a phosphate group and a nitrogen-containing organic base
  • Phosphodiester bonds join adjacent nucleotides
  • 2 polynucleotide chains held together by hydrogen bonds Between specific complementary base pairs - adenine / thymine and cytosine / guanine
  • Double helix
160
Q

Describe the structure of (messenger) RNA

A
  • Polymer of nucleotides (polynucleotide)
  • Each nucleotide formed from ribose, a phosphate group and a nitrogen-containing organic base
  • Bases - uracil, adenine, cytosine, guanine
  • Phosphodiester bonds join adjacent nucleotides
  • Single helix

Each DNA polynucleotide strand is made up of alternating deoxyribose sugars and phosphate groups bonded together to form the sugar-phosphate backbone. These bonds are covalent bonds known as phosphodiester bonds

161
Q

Compare and contrast the structure of DNA and (messenger) RNA

162
Q

Suggest how the structure of DNA relates to its functions

A
  • Two strands → both can act as templates for semi-conservative replication
  • Hydrogen bonds between bases are weak → strands can be separated for replication
  • Complementary base pairing → accurate replication
  • Many hydrogen bonds between bases → stable / strong molecule
  • Double helix with sugar phosphate backbone → protects bases / hydrogen bonds
  • Long molecule → store lots of genetic information (that codes for polypeptides)
  • Double helix (coiled) → compact
163
Q

Suggest how you can use incomplete information about the frequency of bases on DNA strands to find the frequency of other bases

A
  • % of adenine in strand 1 = % of thymine in strand 2 (and vice versa)
  • % of guanine in strand 1 = % of cytosine in strand 2 (and vice versa)
  • Because of specific complementary base pairing between 2 strands
164
Q

What is the fuction of DNA?

A
  • The function of DNA is to hold or store genetic information
  • DNA is the molecule that contains the instructions for the growth and development of all organisms
165
Q

What is the fuction of mRNA?

A
  • The function of mRNA is to transfer the genetic code found in DNA out of the nucleus and carry it to the ribosomes in the cytoplasm
  • Ribosomes are where proteins are produced - they ‘read’ the mRNA to make polypeptides (proteins) in a process known as translation
166
Q

What are the four nitrogenous bases of DNA?

A

adenine (A), cytosine(C), guanine(G) or thymine(T)

167
Q

How are the two antiparallel DNA polynucleotide strands that make up the DNA molecule held together?

A

Hydrogen bonds between the nitrogenous bases

168
Q

Why is the nucleic acid DNA decsribed as a polynucleotide?

A

It is made up of many nucleotides bonded together in a long chain

169
Q

What are Ribosomes?

A
  • Ribosomes are the site of protein synthesis (where proteins are made)
  • They ‘read’ RNA to make polypeptides (proteins) in a process known as translation
170
Q

What are ribosomes formed from?

A
  • RNA and proteins
  • The RNA that forms part of the structure of ribosomes is a specific type of RNA known as ribosomal RNA (rRNA)
  • The rRNA in ribosomes has enzymatic properties that catalyse the formation of peptide bonds between amino acids
171
Q

Where are 80S ribosomes (composed of 60S and 40S subunits) mostly found?

A

Eukaryotic cells

Ribosomes in eukaryotic cells are larger than those in prokaryotic cells

172
Q

Where are 70S ribosomes (composed of 50S and 30S subunits) mostly found?

A

They are mostly found in prokaryotic cells, as well as in the mitochondria and chloroplasts of eukaryotic cells

173
Q

Are ribosomes membrane bound?

174
Q

What is each nucleotide formed from?

A

Each nucleotide is formed from a pentose, a nitrogen-containing organic base and a phosphate group

175
Q

What are the components of a DNA nucleotide?

A
  • Deoxyribose
  • Phosphate group
  • One of the organic bases adenine, cytosine, guanine or thymine
176
Q

What are the components of a RNA nucleotide?

A
  • Ribose
  • Phosphate group
  • One of the organic bases adenine, cytosine, guanine or uracil
177
Q

What does a condensation reaction between two nucleotides form?

A

A phosphodiester bond

178
Q

Why is semi-conservative replication important?

A

Ensures genetic continuity between generations of cells.

179
Q

Describe the process of semi-conservative DNA replication (6)

A
  • DNA helicase breaks hydrogen bonds between complementary bases, unwinding the double helix
  • Both strands act as templates
  • Free DNA nucleotides attracted to exposed bases and join by specific complementary base pairing
  • Hydrogen bonds form between adenine-thymine and guanine-cytosine
  • DNA polymerase joins adjacent nucleotides on new strand by condensation reactions
  • Forming phosphodiester bonds

Semi-conservative - each new DNA molecule consists of one original / template strand and one new strand

180
Q

Use your knowledge of enzyme action to suggest why DNA polymerase moves in opposite directions along DNA strands

A
  • DNA has antiparallel strands
  • So shapes / arrangements of nucleotides on two ends are different
  • DNA polymerase is an enzyme with a specific shaped active site
  • So can only bind to substrate with complementary shape (phosphate end of developing strand)
181
Q

Name the two scientists who proposed models of the chemical structure of DNA and of DNA replication

A

Watson and Crick

182
Q

Describe the work of Meselson and Stahl in validating the Watson-Crick model of semi-conservative DNA replication

A
  • Bacteria grown in medium containing heavy nitrogen (15N) and nitrogen is incorporated into DNA bases
  • DNA extracted & centrifuged → settles near bottom, as all DNA molecules contain 2 ‘heavy’ strands
  • Bacteria transferred to medium containing light nitrogen (14N) and allowed to divide once
  • DNA extracted & centrifuged → settles in middle, as all DNA molecules contain 1 original ‘heavy’ and 1 new ‘light’ strand
  • Bacteria in light nitrogen (14N) allowed to divide again
  • DNA extracted & centrifuged → half settles in middle, as contains 1 original ‘heavy’ and 1 new ‘light’ strand; half settles near top, as contains 2 ‘light’ strands
183
Q

Name the type of bond between complementary base pairs (1)

A

Hydrogen Bonds

184
Q

Name the type of bond between adjacent nucleotides in a DNA strand (1)

A

Phosphodiester (bonds)

185
Q

Describe the structure of DNA (5)

A
  • Polymer of nucleotides
  • Each nucleotide formed from deoxyribose, a phosphate (group) and an organic/nitrogenous base
  • Phosphodiester bonds (between nucleotides)
  • Double helix/2 strands held by hydrogen bonds
  • (Hydrogen bonds/pairing) between adenine, thymine and cytosine, guanine
186
Q

Describe how a phosphodiester bond is formed between two nucleotides within a DNA molecule (2)

A
  • Condensation reaction / loss of water
  • between phosphate and deoxyribose
187
Q

Describe how the separation of strands occurs during the process of semi-conservative DNA replication (2)

A
  • DNA helicase
  • Breaks hydrogen bonds between base pairs/ AT and GC/complementary bases
188
Q

Describe the role of DNA polymerase in the semi-conservative replication of DNA (2)

A
  • Joins (adjacent DNA) nucleotides
  • (Catalyses) condensation (reactions)
  • Catalyses formation of) phosphodiester bonds (between adjacent nucleotides)
189
Q

Give two features of DNA and explain how each one is important in the semi-conservative replication of DNA (2)

A
  • Weak / easily broken hydrogen bonds between bases allow two strands to separate / unzip
  • Two strands, so both can act as templates
  • Complementary base pairing allows accurate replication
190
Q

Describe the role of two named enzymes in the process of semi- conservative replication of DNA (3)

A
  • (DNA) helicase causes breaking of hydrogen/H bonds (between DNA strands)
  • DNA polymerase joins the adjacent (DNA) nucleotides on new strand
191
Q

What is the function of DNA helicase (1)

A
  • (unwinding DNA and) breaking hydrogen bonds / bonds between chains / bases / strands
192
Q

What is the function of DNA polymerase (1)

A
  • joins (adjacent) nucleotides OR forms phosphodiester bond / sugar-phosphate backbone
193
Q

Explain what is meant by a polymer (1)

A
  • A molecule made up of many identical molecules / monomers
194
Q

Give one example of a biologically important polymer other than starch or protien (1)

A
  • Cellulose
  • Glycogen
  • Nucleic acid
  • DNA / RNA
195
Q

What are polysaccharides?

A
  • Polysaccharides are polymers, formed by combining together many monosaccharide molecules
  • The monosaccharides are joined together by glycosidic bonds that are formed by condensation reactions
196
Q

what is mRNA?

A
  • Messenger RNA is a copy of a gene from DNA
  • mRNA is created in the nucleus and it then leaves the nucleus to carry the copy of the genetic code of one gene to a ribosome in the cyoplasm
197
Q

Why is mRNA needed?

A
  • DNA is too large to leave the nucleus - damaged by enzymes - mRNA is shorter
  • mRNA is short lived
  • mRNA is single stranded
198
Q

what is transfer RNA (tRNA) ?

A
  • tRNA is only found in the cytoplasm
  • It is single stranded
  • Its function is to attatch to one of the 20 amino acids and transfer this amino acid to the ribosome to create the polypeptide chain.
  • Specific amino acids attatch to specific tRNA molecules and this is determined by 3 bases found on the tRNA which are complementary to the 3 bases on mRNA
  • these are called the anticodon because they are complementary to the codon on mRNA
199
Q

Give four structural differences between a DNA molecule and an mRNA molecule (4)

A
  • DNA has deoxyribose, mRNA has ribose
  • DNA has thymine, mRNA has uracil
  • DNA is long, mRNA is short
  • DNA is double stranded, mRNA is single stranded
  • DNA has hydrogen bonds, mRNA does not
  • DNA has complementary base pairings, mRNA does not
200
Q

Describe the process of DNA replication (5)

A
  • semi-conservative replication
  • DNA strands unwind
  • nucleotides line up along both strands
  • complementary pairing between bases
  • hydrogen bonds formed between bases
  • formation of phosphodiester bonds
  • condensation reaction
  • reference to polymerase + helicase
201
Q

Define the term enzyme (2)

A
  • A biological catalyst that speeds up the rate of reaction
  • It is a protien / specific / has an active site
202
Q

Explain how an enzyme-substrate complex increases the rate of reaction (2)

A
  • Lowers activation energy
  • Due to weakening bonds
203
Q

Describe the induced fit hypothesis for enzyme action (2)

A
  • Active site not complementary to substrate
  • Active site flexible / moulds to substrate
  • Change in shape of active site allows ES complex to form
204
Q

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

A
  • Tertiary structure / 3D shape of enzyme (means)
  • Active site complementary to maltose / substrate
  • Description of induced fit
  • Enzyme is a catalyst / lowers activation energy
  • by forming ES complex
  • Breaking down / forming bonds
205
Q

Explain why changing certain amino acids that are not part of the active site also prevent the enzyme from functioning

A
  • The changed amino acid may be one that forms hydrogen bonds with other amino acids
  • If the new amino acid does not form hydrogen bonds the tertiary structure of the enzyme will change
  • so the substrate may no longer fit
206
Q

Describe a biochemical test to show that a solution contains a non-reducing sugar (3)

A
  • Heat with acid and neutralise
  • Heat with Benedict’s (solution)
  • Red precipitate/colour
207
Q

Describe and explain two features of starch that make it a good storage molecule (2)

A
  • Insoluble (in water), so doesn’t affect water potential
  • Branched / coiled / (α-)helix, so makes molecule compact
  • Branched / coiled / (α-)helix so can fit many (molecules) in small area
  • Polymer of (α-)glucose so provides glucose for respiration
  • Branched / more ends for fast breakdown / enzyme action
  • Large (molecule), so can’t cross the cell membrane
208
Q

Describe the structure of glycogen (2)

A
  • Polysaccharide of α-glucose
  • (Joined by) glycosidic bonds
  • Branched structure
209
Q

Explain how cellulose molecules are adapted for their function in plant cells (3)

A
  • Long and straight chains
  • Become linked together by many hydrogen bonds to form fibrils
  • Provide strength (to cell wall)
210
Q

What is ATP?

A

Adenosine Triphosphate

211
Q

Describe how ATP is broken down

A
  • ATP (+ water) → ADP (adenosine diphosphate) + Pi (inorganic phosphate)
  • Hydrolysis reaction, using a water molecule
  • Catalysed by ATP hydrolase (enzyme)
212
Q

Give two ways in which the hydrolysis of ATP is used in cells

A
  • Coupled to energy requiring reactions within cells (releases / provides energy)
  • Eg. active transport, protein synthesis
  • Inorganic phosphate released can be used to phosphorylate (add phosphate to) other compounds, making them more reactive
213
Q

Describe how ATP is resynthesised in cells

A
  • ADP + Pi → ATP (+ water)
  • Condensation reaction, removing a water molecule
  • Catalysed by ATP synthase (enzyme)
  • During respiration and photosynthesis
214
Q

Suggest how the properties of ATP make it a suitable immediate source of energy for cells

A
  • Releases energy in (relatively) small amounts / little energy lost as heat
  • Single reaction / one bond hydrolysed to release energy (so immediate release)
  • Cannot pass out of cell
215
Q

Describe how an ATP molecule is formed from its component molecules (4)

A
  • adenine, ribose/pentose, three phosphates
  • Condensation (reaction)
  • ATP synthase
216
Q

Name the two products of ATP hydrolysis.
(1)

A
  • Adenosine diphosphate and (inorganic) phosphate
217
Q

ATP is an energy source used in many cell processes. Give two ways in which ATP is a suitable energy source for cells to use (2)

A
  • Releases relatively small amount of energy / little energy lost as heat;
  • Releases energy instantaneously
  • Phosphorylates other compounds, making them more reactive
  • Can be rapidly re-synthesised
  • Is not lost from / does not leave cells
218
Q

Describe how ATP is resynthesised in cells (2)

A
  • From ADP and phosphate
  • By ATP synthase
  • During respiration/photosynthesis
219
Q

Give two ways in which the hydrolysis of ATP is used in cells (2)

A
  • To provide energy for other reactions/named process
  • To add phosphate (phosphorylate) to other substances / compounds making them more reactive
220
Q

How does ATP act as an energy carrying molecule? (3)

A
  • Energy from respiration is stored in the bonds between phosphate groups of ATP
  • And can be released when these bonds are hydrolysed
  • The greatest amount of energy in the bond between the second and third phosphate groups
221
Q

Explain how hydrogen bonds occur between water molecules

A
  • Water is polar molecule
  • Slightly negatively charged oxygen atoms attract slightly positively charged hydrogen atoms of other water molecules
222
Q

Explain 5 properties of water that are important in biology

223
Q

Where are inorganic ions found in the body?

A

In solution in cytoplasm and body fluid, some in high concentrations and others in very low concentrations.

224
Q

Describe the role of Hydrogen (H+) ions

A
  • Maintain pH levels in the body → high conc. = acidic / low pH
  • Affects enzyme rate of reaction as can cause enzymes to denature
225
Q

Describe the role of Iron ions (Fe2+)

A
  • Component of haem group of haemoglobin
  • Allowing oxygen to bind/associate for transport as oxyhaemoglobin
226
Q

Describe the role of sodium ions (Na+)

A
  • Involved in co-transport of glucose / amino acids into cells
  • Involved in action potentials in neurons
  • Affects water potential of cells / osmosis
227
Q

Describe the role of phosphate ions (PO43-)

A
  • Component of nucleotides, allowing phosphodiester bonds to form in DNA / RNA
  • Component of ATP, allowing energy release
  • Phosphorylates other compounds making them more reactive
  • Hydrophilic part of phospholipids, allowing a bilayer to form
228
Q

Describe how the structure of a phospholipid is different from that of a tryglyceride (1)

A

Contains a phosphate instead of one of the three fatty acids

229
Q

Why is ATP such a good energy carrying moleucle (6)

A
  • Releases energy in small manageable amounts - less waste energy -heat energy loss
  • Broken down in a one step reaction - only one bond must be hydrolysed to release energy
  • Small, soluble and easily diffuses from the mitochondria to the part of the cell where it is needed
  • It can be used to phosphorylate and make other molecules more reactive
  • ATP cannot pass out of the cell so the cell always has an immediate supply of energy
  • It can be quickly reformed
230
Q

Contrast the structure of ATP and the monomers of DNA (3)

A
  • ATP has ribose and DNA monomers have deoxyribose
  • ATP has 3 phosphate groups and DNA monomers have 1 phosphate group
  • ATP - Base is always adenine and in DNA monomer it can be adenine, thymine, cytosine or guanine
231
Q

Write a simple equation to show how ATP is synthesised from ADP (1)

A

ADP + Pi → ATP (+ H2O)

232
Q

Write a simple equation to show how energy is released from ATP (1)

A

ATP + H2O > ADP + Pi

233
Q

Explain five properties that make water important for organisms (5)

A
  • A metabolite in condensation/hydrolysis/ photosynthesis/respiration
  • A solvent so (metabolic) reactions can occur /A solvent so allowing transport of substances
  • High (specific) heat capacity so buffers changes in temperature
  • Large latent heat of vaporisation so provides a cooling effect (through evaporation)
  • Cohesion (between water molecules) so supports columns of water (in plants) / Cohesion (between water molecules) so produces surface tension supporting (small) organisms
234
Q

State and explain the property of water that helps to prevent temperature increase in a cell (2)

A
  • High (specific) heat capacity
  • Buffers changes in temperature

Accept ideas such as a lot of energy needed/gained to change temperature

235
Q

State and explain the property of water that can help to buffer changes in temperature (2)

A
  • (water has a relatively) high (specific) heat capacity
  • Can gain / lose a lot of heat / energy without changing temperature
236
Q

Describe the induced-fit model of enzyme action and how an enzme acts as a catalyst (3)

A
  • Substrate binds to the active site/enzyme
  • Enzyme-substrate complex forms
  • Active site changes shape (slightly) so it is complementary to substrate
  • so distorting/breaking/forming bonds in the substrate
  • Reduces activation energy
237
Q

Explain how a competitive inhibitor decreases the rate of an enzyme-controlled reaction (3)

A
  • Inhibitor similar shape to substrate
  • Fits/binds to active site
  • Prevents/reduces enzyme-substrate complex forming
238
Q

Explain how the active site of an enzyme causes a high rate of reaction (3)

A
  • Lowers activation energy
  • Induced fit causes active site (of enzyme) to change shape
  • (So) enzyme-substrate complex causes bonds to form/break
239
Q

Explain how a decrease in temperature decreases the rate of an enzyme-controlled reaction (2)

A
  • molecules moving less / slower; reduces chance of collision | of enzyme-substrate complexes being formed
240
Q

Urea breaks hydrogen bonds

Explain how the addition of urea would affect the rate of an enzyme-controlled reaction (3)

A
  • these bonds hold / maintain tertiary / globular structure (of enzyme)
  • enzyme denatured / tertiary structures destroyed; (shape of) active site distorted / changes
  • substrate no longer fits / enzyme-substrate complex not formed
241
Q

Describe two differences between the structure of a tRNA molecule and the structure of an mRNA molecule (2)

A
  • tRNA is ‘clover leaf shape’, mRNA is linear
  • tRNA has hydrogen bonds, mRNA does not
  • mRNA fewer nucleotides
242
Q

Describe how a phosphodiester bond is formed between two nucleotides within a DNA molecule (2)

A
  • Condensation reaction
  • Between phosphate and dexoyribose
  • Catalysed by DNA polymerase
243
Q

What is the role of single stranded DNA fragments in DNA replication (1)

A
  • Template
  • Determines order of nucleotides/bases
244
Q

What is the role of DNA Nucleotides in DNA replication (1)

A
  •   Forms complementary pairs / A – T, G - C
  •   Forms complementary (DNA) strand
245
Q

Contrast the structure of ATP and a nucleotide found in DNA (2)

A
  • ATP has ribose and DNA nucleotide has deoxyribose
  • ATP has 3 phosphate (groups) and DNA nucleotide has 1 phosphate (group)
  • ATP – base always adenine and in DNA nucleotide base can be different / varies;
246
Q

Give two wats in which prokaryotic DNA is different from eukaryotic DNA (2)

A
  • Smaller
  • Circular / non-linear (DNA)
  • Not (associated) with proteins
247
Q

Outline the role of iron ions, sodium ions and phosphate ions in cells and organisms (6 marks)

A
  • Iron ions
  • Haemoglobin binds / associates with oxygen / transports loads of oxygen
  • Sodium ions
  • Co transport of glucose / amino acids into cells
  • Because sodium is moved out by active transport
  • Creates a sodium concentration / diffusion gradient
  • Affects osmosis / water potential
  • Phosphate ions
  • Affects osmosis / water potential
  • Joins nucleotides in phosphodiester bonds in the backbone of DNA
  • Used in / to produce ATP
  • Phosphorylates other compounds making them more reactive
  • Hydrophilic / water soluble part of phospholipids belayer / membrane
248
Q

What property of iron ions enables then to carry out its role in haemoglobin (2)

A
  • Charged / polar
  • So binds to oxygen / forms oxyhemoglobin / transports oxygen
249
Q

Compare triglycerides and phospholipids (3)

A
  • One of the fatty acids in phospholipids are replaced by a phosphate group
  • Both has glycerol
  • Both have ester bonds
  • Only phospholipids have a phosphate
250
Q

What are monomers (1)

A
  • Smaller / repeating molecules from which larger molecules / polymers are made
251
Q

What are polymers (1)

A

Molecule made up of many identical / similar molecules / monomers

252
Q

What happens in condensation reactions?

A
  • 2 molecules join together
  • Forming a chemical bond
  • Releasing a water molecule
253
Q

What happens in hydrolysis reactions?

A
  • 2 Molecules are separated
  • Breaking a chemical bond
  • Using a water molecule
254
Q

What are disaccharides and how are they formed?

A
  • Two monosaccharides joined together with a glycosidic bond
  • Formed by a condensation reaction, releasing a water molecule
255
Q

List three common disaccharides and the monosaccharides from which they are made:

A
  • Maltose : Glucose + Glucose
  • Sucrose : Glucose + Fructose
  • Lactose : Glucose + Galactose
256
Q

What are polysaccharides and how are they formed?

A
  • Many monosaccharides joined together with glycosidic bonds
  • Formed by condensation reactions, releasing water molecules
257
Q

What is the function of Tryglicerides?

A
  • Energy storage
258
Q

Which part of the DNA molecule contains nitrogen?

259
Q

Explain why the DNA from Generation (1) is found in the position shown (2)

A
  • It has been produced by semi-conservative repliaction / one old strand and one new
  • One strand has 15N base and the other 14N
260
Q

Give two ways in which the properties of ATP make it a suitable source of energy in biological processes (1)

A
  • Energy released in small amounts
  • One step reaction
261
Q

An enzyme catalyses only one reaction. Explain why (2)

A
  • Enzyme has an active site
  • Only substrate fits
262
Q
A
  • Allopurinol has a similar shape to Xanthine
  • It enters active site / acts as a competetive inhibitor
  • Less xanthine binds / fewer e-s formed
263
Q

Biological washing powders often contain a number of different enzymes

Explain why a number of enzymes are required to remove a wider range of stains (3)

A
  • Stains are caused by different substances
  • Enzymes are specific
  • Active site specific to substrate
264
Q

E. coli has no cholesterol in its cell-surface membrane. Despite this, the cell
maintains a constant shape. Explain why (2)

A
  • Cell unable to change shape
  • (Because) cell has a cell wall
  • (Wall is) rigid / made of murein
265
Q
A
  • Starch formed from α-glucose but cellulose formed from β-glucose
  • Position of hydrogen and hydroxyl groups on carbon atom 1 inverted
266
Q
A
  • Insoluble; Don’t affect water potential
  • Helical - compact
  • Large molecule - cannot leave cell
267
Q

Explain how cellulose molecules are adapted for their function in plant cells (3)

A
  • Long and straight chains
  • Become linked together by many hydrogen bonds to form fibrils
  • Provide strength (to cell wall)
268
Q

Describe the structure of proteins (5)

A
  • Polymer of amino acids
  • Joined by peptide bonds
  • Formed by condensation reactions involving the loss of a water molecule
  • 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
269
Q

Describe how proteins are digested in the human gut (4)

A
  • Hydrolysis of peptide bonds
  • Endopeptidases break polypeptides into smaller peptide chains
  • Exopeptidases remove terminal amino acids
  • Dipeptidases hydrolyse / break down dipeptides into amino acids
270
Q

Name A and B (2)

A
  • phospholipid (layer)
  • Intrincis protien
272
Q

Describe the structure of a cellulose molecule and explain how cellulose is adapted for its function in cells (6)

273
Q

Describe the structure of glycogen (2)

A
  • Polysaccharide of α-glucose
  • (Joined by) glycosidic bonds
  • Branched structure
274
Q

During early pregnancy, the glycogen in the cells lining the uterus is an important energy source for the embryo.
Suggest how glycogen acts as a source of energy.
Do not include transport across membranes in your answer (2)

A
  • Hydrolysed (to glucose);
  • Glucose used in respiration;
275
Q

Suggest and explain two ways the cell-surface membranes of the cells lining the uterus may be adapted to allow rapid transport of nutrients (2)

A
  • Membrane folded so increased / large surface area
  • Large number of protein channels / carriers (in membrane) for facilitated diffusion
  • Large number of protein carriers (in membrane) for active transport
  • Large number of protein (channels / carriers in membrane) for co-transport
276
Q

What term is used to describe the different structures of α-glucose and β-glucose? (1)

A

Isomer(ism)

277
Q

The student controlled variables in the test using Benedict’s solution.
Give two variables the student controlled (2)

A
  • Benedict’s (solution) volume
  • Benedict’s (solution) concentration
  • Water bath/water temperature
278
Q

Iodine solution stains fresh apple tissue black. When iodine solution is added to apples
stored for a week, the stain is less black.
The water potential of apple juice decreases when apples are stored.
Suggest why the water potential of apple juice decreases when apples are stored (2)

A
  • Starch hydrolysis (to maltose)
  • Maltose is soluble, but starch is insoluble; 2 (2 x AO2)
279
Q

Describe how you would test for the presence of a lipid in a liquid sample of food (2)

A
  • Add ethanol/alcohol then add water and shake/mix
  • White/milky (emulsion)
280
Q

Describe one way that the lock and key model is different from the induced fit model (1)

A

Active site does not change (shape)

281
Q
A
  • Similar structure / shape (to PABA) / both complementary
  • Competes for / binds to active site / competitive inhibitor
  • Less PABA binds / less E-S complexes
282
Q

Describe the role of DNA polymerase in DNA replication (1)

A

Joins nucleotides (to form new strand)

283
Q

Other than being smaller, give two ways in which prokaryotic DNA is different from eukaryotic DNA (2)

A
  • Circular / non-linear (DNA)
  • Not (associated) with proteins
284
Q
A
  • Have different genes
  • (Sobases / triplets) are in a different sequence / order
  • (So) different amino acid (sequence / coded for) / different protein /
    different polypeptide / different enzyme
285
Q

The events that take place during interphase and mitosis lead to the production of two genetically identical cells. Explain how (4)

A
  • DNA replicated
  • (Involving) specific / accurate / complementary base-pairing
  • (Ref to) two identical / sister chromatids
  • Each chromatid / moves / is separated to (opposite) poles / ends of cell
286
Q
A

Deoxyribose

287
Q
A
  • c) DNA polymerase
  • d) (Figure 1 shows) DNA has antiparallel strands
  • (Figure 1 shows) shape of the nucleotides is different / nucleotides aligned differently
  • Enzymes have active sites with specific shape
  • Only substrates with complementary shape / only the 3’ end can bind with active site of enzyme / active site of DNA polymerase
288
Q
A

Repeating units / nucleotides / monomer / molecules

289
Q

ATP is an energy source used in many cell processes. Give two ways in which ATP is a suitable energy source for cells to use (2)

A
  • Releases relatively small amount of energy / little energy lost as heat
  • Releases energy instantaneously - only one bond hydrolysed at a time - one step reaction
291
Q

The scientists concluded that an increase in phosphate in the embryo was linked to growth of the embryo. Suggest two reasons why an increase in phosphate can be linked to growth of the embryo (2)

A
  • (Phosphate required) to make DNA
  • (Phosphate required) to make ATP/ADP
  • (Phosphate required) to make membranes
  • (Phosphates required) for phosphorylation
292
Q

Scientists determined the mean FEV1 value of 25-year-olds in the population.
Suggest two precautions that should have been taken to ensure that this mean FEV1 value was reliable (2)

A
  • Large sample size
  • Individuals chosen at random
  • Are healthy
  • Equal number of males and females
  • Same gender
293
Q
A
  • . (Lactulose) lowers the water potential of faeces / intestine / contents of the intestine
  • Water retained / enters (due to osmosis) and softens the faeces
294
Q

Draw and and label a single DNA nucleotide (2)

295
Q

A student used a dilution series box to investigate the number of cells present in a liquid culture of bacteria.
Describe how he made a 1 in 10 dilution and then used this to make a 1 in 1000 dilution of the original liquid culture of bacteria (3)

A-Level Biology (Paper 1) (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions