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A Level Aqa Biology > Biological Molecules > Flashcards

Biological Molecules Flashcards

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1
Q

What is a polysaccharide?

A

A polymer from many monosaccharides, which are joined by glycosidic bonds that form in condensation reactions.

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2
Q

What are monosaccharides?

A

Sweet-tasting, soluble substances that have the general formula (CH2O) n
N - 3-7

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3
Q

Give examples of monosaccharides

A

Galactose, glucose and fructose

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4
Q

What is a disaccharide?

A

A Disaccharide is the condensation of two monosaccharides

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5
Q

Give examples of disaccharides

A

Sucrose, maltose and lactose

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6
Q

What is the formula for Glucose, Fructose and Galactose?

A

C6H12O6

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7
Q

What is the general formula for a disaccharide?

A

CnH2nOn

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8
Q

What makes maltose?

A

Joining of 2 glucoses

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9
Q

What makes sucrose?

A

Glucose and Fructose joined by an alpha 1,4 glycosidic bond

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10
Q

What makes lactose ?

A

Glucose and Galactose joined by a beta 1,4 glycosidic bond

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11
Q

Is sucrose reducing or non-reducing?

A

Non-reducing

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12
Q

Is maltose and lactose non-reducing or reducing?

A

Reducing

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13
Q

Where is sucrose found in living things?

A

Sugar cane

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14
Q

Where is maltose found in living things?

A

Germanated seeds

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15
Q

Where is lactose found in living things?

A

Milk

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16
Q

What is a condensation reaction?

A

When a molecule of water is removed

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17
Q

What is a hydrolysis reaction?

A

The addition of water that causes a breakdown

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18
Q

Are polysaccharides soluble or insoluble?

A

Insoluble as they are large molecules

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19
Q

What are polysaccharides suitable for?

A

Storage

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20
Q

Give examples of polysaccharides

A

Cellulose, starch and glycogen

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21
Q

What is starch?

A

It is a polysaccharide that’s found in small grains. It’s forms a component of food and is a major energy store in diets

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22
Q

What is starch made up of?

A

Chains of alpha glucose monosaccharides linked by glycosidic bonds that are formed by condensation reactions

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23
Q

What is the main role of starch?

A

It’s an energy store

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24
Q

Does starch affect water potential and why?

A

No it does not because it is insoluble and therefore does not draw water into the cells by osmosis.

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25
Q

Why is starch compact?

A

It has a helix shape, and so allot of it can be stored in a small space

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26
Q

What happens when starch is hydrolysed?

A

It’s forms Alpha glucose, which is easily transported and readily used in respiration

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27
Q

Why does starch have many ends?

A

So enzymes can act of the ends, and the glucose monomers can be released very rapidly.

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28
Q

What is the two forms of starch?

A

Amylose and amylopectin

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29
Q

Describe the synthesis of starch

A

Two alpha/beta glucose being arragated together through a condensation reaction

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30
Q

Amylose is tightly coiled, why is this feature important?

A

Can be a compact shape and allow more space in the cell, letting more molecules inside.

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31
Q

Where is glycogen found?

A

Animals and bacteria

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32
Q

What is the structure of glycogen?

A

Has short chains, highly branched.

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33
Q

What is glycogens role?

A

Store of energy for respiration and affects the rate of metabolism.

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34
Q

What is cellulose made of?

A

Monomers of beta glucose rather than alpha glucose

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35
Q

What chains do cellulose have?

A

They have Straight, unbranched chains. They run parallel to one another,. It allows hydrogen bonds to form cross-linkages between straight chains.

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36
Q

What do cellulose molecules form?

A

Microfibrill

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37
Q

What makes cellulose strong?

A

Individual hydrogen bonds add very little strength to a molecule: many make a huge contribution to strength

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38
Q

What is cellulose formed by?

A

Its bonded by OH (hydroxyl groups) every 2 cellulose molecules and become inverted for condensation reaction to occur

39
Q

What are the characteristics of lipids?

A

Organic molecules, insoluble in water, soluble in organic solvents

40
Q

What are the main groups of lipids?

A

Trygyclerides and phospholipids

41
Q

What do phospholipids contribute to?

A

The flexibility of membranes and the transfer of lipid-soluble substances across them

42
Q

Lipid is a source of energy enhance further

A

When oxidised, lipids provide twice the energy as the same mass of a carbohydrate and release valuable water.

43
Q

Waterproofing is a role of lipids, enhance further

A

Lipids are insoluble so it’s useful. Insects and plants have waxy, lipid cuticles.

44
Q

Insulation is a role of lipids, enhance further

A

Fats slow conductors of heat and when stored beneath the body surface help to retain body heat. Act as electrical insulators in the mylein sheath around nerve cells.

45
Q

Protection is a role of lipid, enhance further

A

Fat is often stored around delicate organs, such as the kidney.

46
Q

What are trygyclerides?

A

They have 3 fatty acids and 1 glycerol

47
Q

What do fatty acids form?

A

An ester bond with glyercol in a condensation reaction.

48
Q

What does a fatty acid contain?

A

Large hydrocarbon chain and a carboxylic group (COOH)

49
Q

How many ester bonds are there in a trygyclerides?

A

3 ester bonds

50
Q

Give the specific functions of proteins in living things

A

Acting as enzymes and hormones. Making antibodies,. Tissue regeneration. Providing nutrient transport

51
Q

What differs in the 20 essential amino acids?

A

The side-chain group/ R group

52
Q

What is the peptide bond between two amino acids?

A

C-N

53
Q

What is a polypeptide?

A

A chain of many hundreds of amino acids

54
Q

What is a fibrous protein?

A

Form long chains that are run parallel to one another, chains linked by cross-bridges and so form very stable molecules. And is insoluble in water

55
Q

What is a globular protein?

A

Form circular chains that are irregular and wide of R groups. And is soluble in water.

56
Q

Describe the primary structure of a protein and the bonds

A

A sequence of amino acids found in its polypeptide chains and the sequence determines it’s properties and shape. It has a covalent peptide bond

57
Q

Describe the secondary structure of a protein and the bonds

A

The shape which polypeptide chain forms as a result of hydrogen bonding. It’s known as an alpha helix. Hydrogen bonds are formed between atoms of the polypeptide backbone.

58
Q

Describe the tertiary structure of a protein and the bonds

A

Due to the bending and twisting of the polypeptide helix into a compact structure. It has disulfide, ionic and hydrogen bonds.

59
Q

Describe the quaterny structure of a protein and the bonds

A

Combination of a number of different polypeptide chains and associated non-protein groups into a large, complex protein molecule, e.g Haemoglobin

60
Q

Enzymes act as what?

A

Catalysts lowering activation energy

61
Q

What is activation energy?

A

The minimum amount of energy required to start of a reaction

62
Q

What does lowering the activation energy do?

A

Enzyme allow reactions to take place at lower temperatures than normal

63
Q

What is a substrate?

A

A molecule on which the enzyme acts

64
Q

What is an active site?

A

A specific region of the enzyme is functional.

65
Q

What is an enzyme substrate complex?

A

Where a substrate binds to an enzymes active site held by bonds that temporarly form between certain amino acids of the active site and groups on the substrate molecule

66
Q

What does the induced fit model propose?

A

That the active site forms as the enzyme and substrate interact

67
Q

In the induced fit model, the proximity of the substrate leads to what?

A

A change in the enzyme that forms the functional active site.

68
Q

As the active site changes shape, what does the enzyme do?

A

Puts a strain on the substrate molecule, distorting the bonds in the substrate which lowers the activation energy needed to break the bond

69
Q

What is the lock and key model?

A

Where the shape of the substrate exactly fits with the active site of the enzyme

70
Q

What is a limitation of lock and key model?

A

It’s seen be considered a rigid structure where actually it is flexible.

71
Q

When measuring a enzyme catalysed reaction, the formation of the products of the reaction is changed most frequently. True or false

A

True

72
Q

One of the changes most frequently measured in a enzyme catalysed reaction is the dissappearance of what+

A

The substrate

73
Q

At first there is a lot of substrate but no product so it is very easy for the what?

A

Substrate molecules to come into contact with the empty active sites on the enzyme molecules

74
Q

All enzyme active sites are filled at any given moment and the substrate is rapidly broken down into its products. What happens to the amount of substrate?

A

It decreases resulting in an increase in the amount of product

75
Q

As the reaction proceeds, there is what left of the substrate and left of the product?

A

Less of the substrate and more of the prodcuct

76
Q

As it becomes difficult for the substrate molecules to come in contact with the enzyme molecules, why?

A

There are fewer substrate molecules and also the product molecules may get in the way of substrate molecules and prevent them from reaching an active site

77
Q

Why does the graphs eventually flatten out in an enzyme catalysed reaction?

A

All the substrate has been used up and so now new product can be produced

78
Q

How do we measure the grate of a reaction?

A

By finding the gradient (a/b)

79
Q

A rise in tempature increases what?

A

The kinetic energy of molecules

80
Q

If there are more effective collisions, what does this result in?

A

More enzyme substrate complexes being formed and so rate of reaction increases.

81
Q

The temperature rise also begins, why?

A

To cause the hyrogen and other bonds in the enzyme molecule to break

82
Q

What is denaturation?

A

A permanent change to the enzymes active site and the enzyme does not function again.

83
Q

The optimum temperature differs from enzyme to enzyme. True or false

A

True

84
Q

Once an active site on an enzyme has acted on its substrate, it is free to do what?

A

Repeat the procedure on another substrate molecule

85
Q

A graph of a rate of reaction against enzyme concentration will initially show a proportionate increase, why?

A

there are more substrate than the enzyme’s active sites can cope with

86
Q

If the substrate is limiting, what does this mean if we increase enzyme concentration?

A

It will have no effect on rate of reaction.

87
Q

If the concentration of an enzyme is fixed and substrate concentration is slowly decreased, what does this mean for the rate of reaction?

A

It increases in proportion to the concentration of the substrate

88
Q

Why is there an increase in proportion to the concentration of a substrate when substrate concentration is slowly increased?

A

A low substrate concentrations, the enzyme molecules have only a limited number of substrate molecules to collide with, the active sites are not working to full capacity.

89
Q

What does a competitive inhibitor do?

A

They bind to the active site of an enzyme

90
Q

What does a non-competitive inhibitor do?

A

They bind to an enzyme at a position other than the active site called the allosteric site

91
Q

Competitive inhibitors have a molecular shape similar to that of the substrate, what does this allow?

A

It allows them to occupy the active site of an enzyme to compete with the substrate for the available active site.

92
Q

What happens to the competitive inhibitor if the substrate concentration is increased?

A

the effect of the competitive inhibitor is reduced

93
Q

is the inhibitor always bound to the active site?

A

No, eventually a substrate takes its place

94
Q

As the substrate and the non competitive inhibitor are not competing for the same site, an increase in substrate concentration does or does not decrease the effect of the inhibitor?

A

It does not

A Level Aqa Biology (10 decks)

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