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BIOLOGY A LEVEL > TOPIC 1A - BIOLOGICAL MOLECULES > Flashcards

TOPIC 1A - BIOLOGICAL MOLECULES Flashcards

-Carbohydrates -Lipids -Proteins -Enzyme action -Factors affecting enzyme activity

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1
Q

What is a polymer?

A

A polymer is a large, complex molecule composed of long chains of monomers joined together.

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2
Q

What is a monomer?

A

Monomers are small, basic molecular units. (e.g. monosaccharides, amino acids and nucleotides)

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3
Q

What are carbohydrates?

A

Carbohydrates are made from monosaccharides (e.g. glucose, fructose and galactose). All carbohydrates contain the elements Carbon, Hydrogen and Oxygen.

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4
Q

What is glucose?

A

Glucose is a hexose sugar - a monosaccharide with six carbon atoms in each molecule.

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5
Q

What are the two types of glucose?

A

Alpha (α) and Beta (β) - These are isomers.

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6
Q

What are isomers?

A

Isomers are molecules with the same molecular formula as each other, but with the atoms connected in a different way.

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7
Q

Draw the structure of an Alpha glucose molecule.

A

See page 2 in the revision guide.

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8
Q

Draw the structure of a Beta glucose molecule.

A

See page 2 in the revision guide.

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9
Q

What is a condensation reaction?

A

A condensation reaction is when two molecules join together with the formation of a new chemical bond and a water molecule is released when the bond is formed.

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10
Q

What bond is formed when two monosaccharides join by a condensation reaction?

A

Glycosidic bond.

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11
Q

What is a disaccharide?

A

Two monosaccharides joined together.

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12
Q

Give an example of a condensation reaction between two monosaccharides to form a glycosidic bond.

A

Two alpha glucose molecules react to form maltose. See page 2 in the revision guide for the diagram.

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13
Q

What two monosaccharides is sucrose made out of?

A

Glucose and fructose.

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14
Q

What two monosaccharides is lactose made out of?

A

Glucose and galactose.

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15
Q

What two monosaccharides is maltose made out of?

A

Two alpha glucose molecules.

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16
Q

What is a hydrolysis reaction?

A

A hydrolysis reaction breaks the bond between the monomers using a water molecule.

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17
Q

How do you test for a reducing sugar?

A
  • Reducing sugars include all monosaccharides (e.g. glucose) and some disaccharides (e.g. maltose and lactose)
    1) Add Benedict’s reagent (which is blue) to a sample and heat it in a water bath that’s been brought to the boil.
    2) If the test is positive it will form a coloured precipitate.
    -The colour of the precipitate goes from:
    BLUE > GREEN > YELLOW > ORANGE > RED
    The higher the concentration of reducing sugar, the further the colour change. (More accurate way to determine this is to filter the solution and weigh the precipitate).
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18
Q

How do you test for a non-reducing sugar?

A
  • If the result of the reducing sugars test is negative:
    2) Get a new sample of the test solution and add hydrochloric acid and carefully heat it in a water bath that’s been brought to the boil. (This breaks the non-reducing sugar down into monosaccharides).
    3) Neutralise it with sodium hydrogencarbonate
    4) Carry out the Benedict’s test as you would for a reducing sugar.
    5) If the test’s positive it will form a coloured precipitate like the reducing sugars test. If the test is negative the solution will remain blue - this means there is neither a reducing and non-reducing sugar in the solution.
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19
Q

What is a polysaccharide?

A

A polysaccharide is formed when more than two monosaccharides are joined together by condensation reactions.

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20
Q

Give an example of a polysaccharide.

A

Lots of alpha-glucose molecules are joined together by glycosidic bonds to form amylose.

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21
Q

What is starch?

A

Starch is the main energy storage material in plants. Plants store excess glucose as starch and break it down to release the glucose when they need more energy.
Starch is a mixture of two polysaccharides - AMYLOSE and AMYLOPECTIN
Starch is insoluble in water and doesn’t affect water potential - so it doesn’t cause water to enter cells by osmosis which would make them swell making it good for storage.

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22
Q

Why is amylose good for storage?

A

Amylose is a long, unbranched chain of alpha-glucose. The angles of the glycosidic bonds give it a coiled structure. This makes it compact, so it’s really good for storage because you can fit more into small space.
See page 4 in the revision guide for a diagram.

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23
Q

Why is amylopectin good for fast energy release?

A

Amylopectin is a long, branched chain of alpha-glucose. Its side branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily. This means that the glucose can be released quickly.
See page 4 in the revision guide for a diagram.

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24
Q

How do you test for starch?

A

Add iodine dissolved in potassium iodide solution to the test sample. If there is starch present, the sample changes from browny-orange to a dark, blue-black colour.

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25
Q

What is glycogen?

A

Glycogen is the main energy storage material in animals. Glycogen is another polysaccharide of alpha-glucose.

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26
Q

What is glycogen’s structure? And how does that help its functions?

A

Glycogen has a similar structure to amylopectin it is just more branched. This means that the stored glucose can be released quickly which is important for energy release in animals.
Glycogen is also a very compact molecule meaning it is good for storage.

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27
Q

What is cellulose made out of?

A

Cellulose is made out of long, unbranched chains of beta-glucose. This forms straight cellulose chains which are linked together by hydrogen bonds to form strong fibres called microfibrils.
These strong fibres mean cellulose provides structural support for cells (e.g. in plant cell walls)

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28
Q

What are triglycerides?

A

Tryglycerides are a type of lipid. They have one molecule of glycerol with three fatty acids attached to it.

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29
Q

Why are lipids insoluble in water?

A

The fatty acid tails are hydrophobic.

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30
Q

What reaction are triglycerides formed by?

A

Triglycerides are formed by condensation reactions.

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31
Q

What is the bond formed from a condensation reaction in triglycerides between the glycerol and fatty acid?

A

The bond between glycerol and a fatty acid is an ester bond. (see page 6 in the revision guide for a diagram)

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32
Q

What is a saturated fatty acid?

A

Saturated fatty acids don’t have any double carbon bonds. The fatty acid is ‘saturated’ with hydrogen. (see page 6 in the revision guide for a diagram)

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33
Q

What is an unsaturated fatty acid?

A

Unsaturated fatty acids have at least one double carbon bond, this causes the chain to kink. (see page 6 in the revision guide for a diagram)

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34
Q

Draw the structure of a phospholipid.

A

See page 6 in the revision guide for a diagram.

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35
Q

Which part of a phospholipid is hydrophobic and hydrophilic?

A

The phosphate group is hydrophilic and the fatty acid tails are hydrophobic.

36
Q

How does the structure of a triglyceride relate to its function?

A
  • Triglycerides are mainly used as energy storage molecules.
    1) The long hydrocarbon tails of the fatty acids contain lots of chemical energy, meaning a lot of energy is released when they are broken down. Because of these tails, lipids contain about twice as much energy as carbohydrates.
    2) They are insoluble, so they don’t affect water potential of the cell and cause water to enter the cells by osmosis. The triglycerides clump together as insoluble droplets in cells because the fatty acid tails are hydrophobic. (see page 7 in the revision guide for a diagram)
37
Q

How does the structure of a phospholipid relate to its function?

A
  • Phospholipids make up the bilayer of cell membranes which controls what enters and leaves the cell.
    1) Their heads are hydrophilic and their tails are hydrophobic, so they form a layer of they’re heads facing outwards and their tails facing inwards. (see page 7 in the revision guide for a diagram)
    2) The centre of the bilayer is hydrophobic, so water-soluble substances can’t easily pass through it - the membrane acts as a barrier to those substances.
38
Q

How do you test for lipids?

A
  • The emulsion test:
    1) Shake the test substance (crush with a mortar and pester into a fine powder) with ethanol for about a minute so that it dissolves.
    2) Then pour the solution into water.
  • Any lipid will show up as a cloudy white emulsion.
  • The more lipid there is, the more noticeable the milky colour will be.
39
Q

What are the monomers of proteins?

A

The monomers of proteins are amino acids.

40
Q

What is formed when two amino acids join together?

A

A dipeptide is formed when two amino acids join together.

41
Q

What is formed when more than two amino acids join together?

A

A polypeptide is formed when more than two amino acids join together.

42
Q

What are proteins made up of?

A

Proteins are made up of one or more polypeptides.

43
Q

Draw the structure of an amino acid.

A

See page 8 in the revision guide for a diagram.

44
Q

What reaction are polypeptides formed by?

A

Polypeptides are formed by condensation reactions.

45
Q

What bond is formed by a condensation reaction between amino acids?

A

A peptide bond.

46
Q

Describe the primary structure 1º of a protein.

A

The sequence of amino acids in the polypeptide chain. (see page 8 in the revision guide for a diagram)

47
Q

Describe the secondary structure of a protein.

A

Hydrogen bonds form between the amino acids in the chain. This makes it automatically coil into an alpha helix or fold into a beta pleated sheet. (see page 8 in the revision guide for a diagram)

When you heat it, the H bonds change and the structure changes, irreversible reaction.

48
Q

Describe the tertiary structure of a protein.

A

More bonds form between different parts of the polypeptide chain, including more hydrogen bonds and ionic bonds. Disulphide bridges also form whenever two molecules of the amino acid cysteine come close together - the sulphur atom in one cysteine bonds to the sulphur atom in the other.
- For proteins made from a single polypeptide chain, the tertiary structure forms their final 3D structure.

3D structure forms due to further folding of the secondary structure.

The ionic bonds form between +ve and -ve charged amino acids (affected by pH).

(see page 8 in the revision guide for a diagram)

49
Q

Describe the quaternary structure of a protein.

A

Some proteins are made of several different polypeptide chains held together by bonds. The quaternary structure is the final 3D structure for these polypeptides. (see page 8 in the revision guide for a diagram)

50
Q

How do you test for proteins?

A
  • Use the Biuret test
    1) Add a few drops of dilute sodium hydroxide solution (NaOH) to make the solution alkaline.
    2) Add some dilute copper (II) sulphate solution (CuSO4).
  • If protein is present the solution will turn purple.
  • If there is no protein present the solution will remain blue.
51
Q

How do enzymes speed up the rate of reaction?

A
  • Enzymes lower the activation energy needed for a certain reaction, often making reactions happen at a lower temperature than they could do without and enzyme. This speeds up the rate of reaction.
  • (see page 10 in the revision guide for why the enzyme substrate complex increases the rate of reaction.)
52
Q

Describe the ‘Lock and Key’ model.

A

(see page 10 in the revision guide for a diagram and description)

53
Q

Describe the ‘Induced Fit’ model.

A

(see page 11 in the revision guide for a diagram and description)

54
Q

How do enzyme properties relate to their tertiary structure?

A 
(see page 11 in the revision guide for a description)
- Remember in class when we made a long protein out of a foam stick and different amino acids clipped onto it and we shaped them depending on the amino acids properties. (the hydrophobic acids would face inwards and vice-versa, then the cysteines would face each other and the charged acids would have to be next to the oppositely charged one etc.) This will help in your answer.
55
Q

What factors affect enzyme activity?

A
  • Temperature
  • pH
  • Enzyme concentration
  • Substrate concentration
56
Q

How does temperature affect enzyme activity?

A

More heat means more kinetic energy, therefore the molecules move faster. So this makes the enzymes more likely to collide with the substrate, leading to more enzyme substrate complexes. The energy of these collisions also increases, which means each collision is more likely to result in a reaction. However, if the temperature gets too high, the reaction stops.
(see page 12 in the revision guide for a diagram)

57
Q

How does pH affect enzyme activity?

A

All enzymes have an optimum pH value. Above and below the pH, the H+ and OH- ions found in acids and alkalis can mess up the ionic bonds and hydrogen bonds that hold the enzymes tertiary structure In place. This makes the active site change shape, so the enzyme is denatured. (see page 12 in the revision guide for a diagram)

58
Q

How does enzyme concentration affect the rate of reaction?

A

The more enzymes there are in a solution, the more likely a substrate is to collide with an enzyme to form an enzyme substrate complex. Therefore, increasing the concentration of enzymes increases the rate of reaction.
(see page 12 in the revision guide to see how the amount of substrate can become a limiting factor.)

59
Q

How does substrate concentration affect the rate of reaction?

A

The higher to substrate concentration, the faster the reaction - more substrate means a more likely collision between the enzyme and substrate and so more active sites will be used. This is only true up to the ‘saturation’ point, though - adding more substrate won’t matter as the enzyme concentration soon becomes a limiting factor.
(see page 12 in there revision guide for a diagram)

60
Q

Describe a competitive inhibitor.

A

(see page 13 in the revision guide)

61
Q

Describe a non-competitive inhibitor.

A

(see page 13 in the revision guide)

62
Q

Describe an experiment to measure how fast the product of an enzyme-controlled reaction is made.

A

(see page 14 in the revision guide)

63
Q

Describe an experiment to measure how fast the substrate of an enzyme-controlled reaction is being broken down.

A

(see page 14 in the revision guide)

64
Q

Read page 15.

A

Do you know and understand page 15?

65
Q

Where is sucrose found in which organism?

A

Sucrose is found in plants in the phloem.

66
Q

Where is maltose found in which organism?

A

Maltose is an intermediate of starch breakdown.

Start is found in plants in the roots (starch grains)

67
Q

Where is lactose found?

A

Lactose is found in milk.

68
Q

What is starch a polymer of?

Where is starch found in which organism?

A

Starch is a polymer of alpha-glucose.

Starch is found in plants in the roots (starch grains)

69
Q

What is glycogen a polymer of?

Where is glycogen found?

A

Glycogen is a polymer of alpha-glucose.

Glycogen is found in the muscles, liver and the brain.

70
Q

What is cellulose a polymer of?

Where is cellulose found in which organism?

A

Cellulose is a polymer of beta-glucose.

Cellulose is found in the cell wall of plant cells.

71
Q

How does cellulose’s structure relate to its function?

A
  • Has a large no. of H-bonds between chains, so it is strong.
  • Forms microfibrils - structural factor/cell wall
  • Long, straight, unbranched chains - so form microfibrils
72
Q

Is sucrose a non-reducing or reducing sugar?

A

non-reducing

73
Q

Is maltose a non-reducing or reducing sugar?

A

reducing

74
Q

Is lactose a non-reducing or reducing sugar?

A

reducing

75
Q

What test would you use to test for starch?

A

iodine test

76
Q

Draw the displayed formula for glycerol.

A

propane-1,2,3-triol

77
Q

Draw the displayed formula for a fatty acid.

A

R-COOH

78
Q

Why do unsaturated molecules tend to be a liquid at room temperature?

A

If it has a C=C bond it is kinked so the molecules cannot pack closely together, so it tends to be liquid with a low boiling point.

(I think)

79
Q

Draw the displayed formula for a triglyceride.

Where is the ester bond?

A

(glycerol + 3 fatty acids)

Look it up?

80
Q

Draw two amino acids joined together with a peptide bond to form a dipeptide.

A

The N from one joins to the C on the other, losing the OH from the carboxyl group and the H from the amine group forming water as a byproduct.

81
Q

In digestion, what is the change in proteins (end and exopeptidases)?

A

Protein -> large polypeptide -> small polypeptide -> dipeptide (exopeptidases) -> amino acids

endopeptidases at start until dipeptide

82
Q

In biology, are H bonds strong?

A

H bonds are weak bonds, but collectively are strong.

83
Q

What is the order of strength in the bonds:

H-bonds
Disulphide bridges
Ionic bonds

A

Fromt strongest:

Disulphide bridges
Ionic bonds
H-bonds

84
Q

In a proteins tertiary structure, what is on the outside of the structure?

A

Hydrophilic R groups

85
Q

Tack polymerase is a bacteria that live in extreme temperatures, what bonds will they have a lot of in their proteins?

A

Disulphide bridges because they are strongest.

86
Q

In a protein where do the H bonds form between?

A

Between the H and O or N.

BIOLOGY A LEVEL (19 decks)

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