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A-level Biology > 1 - Biological Molecules > Flashcards

1 - Biological Molecules Flashcards

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1
Q

What are biological molecules

A

Groups of chemicals found within living organisms

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2
Q

Where do essential biological molecules come from to build our own cells

A

Our diet

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3
Q

What are the 4 main types of organic biomolecules

A

Carbohydrates
Proteins
Lipids
Nuclei acid l

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4
Q

How many bonds do carbon atoms form

A

4

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5
Q

What atoms are present in carbohydrates

A

Carbon
Hydrogen
Oxygen

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6
Q

What atoms are present in lipids

A

Carbon
Hydrogen
Oxygen

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7
Q

What atoms are present in proteins

A

Carbon
Hydrogen
Oxygen
Nitrogen
Sulphur (sometimes)

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8
Q

What atoms are present in phospholipids

A

Carbon
Hydrogen
Oxygen
Phosphorus

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9
Q

What are macromolecules

A

Large

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10
Q

What is the name for the individual building blocks within a larger macromolecule

A

Monomers

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11
Q

What is the name for the longer chain-like molecule made up of the smaller units

A

Polymers

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12
Q

What process joins monomers into bigger chains

A

Condensation

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13
Q

What is the monomer unit in DNA

A

Nucleotides

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14
Q

What are the monomer units in carbohydrates

A

Monosaccharide

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15
Q

What are the monomer units in protein

A

Amino acids

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16
Q

Why are lipids not described as a polymer

A

Lipids are made of one glycerol and 3 fatty acids, not repeating monomers

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17
Q

What 3 groups can carbohydrates be divided into

A

Monosaccharides
Disaccharides
Polysaccharides

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18
Q

Examples of monosaccharides

A

Glucose
Fructose
Galactose

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19
Q

Examples of disaccharides

A

Sucrose
Maltose
Lactose

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20
Q

Examples of polysaccharides

A

Starch
Cellulose
Glycogen

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21
Q

Are monosaccharides soluble

A

Yes

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22
Q

What is the general formula for monosaccharides

A

(CH2O)n

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23
Q

How many carbons can be in a monosaccharide

A

3-7

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24
Q

Name of a 3 carbon monosaccharide

A

Triose

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25
Q

Name of a 4 carbon monosaccharide

A

Tetrose

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26
Q

Name of a 5 carbon monosaccharide

A

Pentose

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27
Q

Name of a 6 carbon monosaccharide

A

Hexose

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28
Q

What is the molecular formula of glucose

A

C6H12O6

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29
Q

Is glucose a monosaccharide, disaccharide or polysaccharide

A

Monosaccharide

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30
Q

What is the bond between 2 glucose units called

A

(Alpha 1,4) glycosidic bond

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31
Q

What type of reaction involved the loss of water during the formation of a bond

A

Condensation reaction

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32
Q

Word equation of the formation of maltose

A

Glucose + glucose = maltose + water

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33
Q

Symbol equation for the formation of maltose

A

C6H12O6 + C6H12O6 = C12H22O11 + H2O

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34
Q

What monosaccharides do you need to make maltose

A

Glucose + glucose

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35
Q

What monosaccharides do you need to make sucrose

A

Glucose + fructose

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36
Q

What monosaccharides do you need to make lactose

A

Galactose + glucose

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37
Q

Fructose formula

A

C12H22O11

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38
Q

How many water molecules are relaxed when 47 monosaccharides joined together and what is the general rule

A

46
(Always one less than the number being joined together)

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39
Q

Definition of hydrolysis

A

A larger molecule is broken down into smaller molecules (bond broken) using water

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40
Q

Definition of condensation

A

Smaller molecules join together to make bigger molecules, a new bond is formed and water is released

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41
Q

T or f
All monosaccharides and some disaccharides are said to be reducing sugars

A

T

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42
Q

What is ment by reducing sugar

A

They are able to donate eLectrons to another substance, thereby reducing the substance

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43
Q

How can we test for the presence of reducing sugars

A

Benedict’s reagent

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44
Q

What is Benedict’s reagent

A

Alkaline solution of copper (ll) sulfate

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45
Q

What is forms when a reducing sugar is heated with Benedict’s reagent

A

Insoluble red precipitate of copper (l) oxide

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46
Q

Describe the Benedict test

A

Add an equal volume of Benedict’s reagent to the liquid ample being tested and heat in a gently boiling water bath for 5 minuets. If a reducing sugar is present, a brink red precipitation will from

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47
Q

What is the difference between a qualitative and a quantitative test

A

Qualitative shows if something is present
Quantitative shows how much

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48
Q

How can u tell the conc of reducing sugar present in the Benedict’s test

A

It’s colour
None - blue
Very low - green
Low - yellow
Medium - orange
High - red

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49
Q

Explain why the Benedict’s test is said to be semi- quantitative

A

It shows something is present but doesn’t give an exact numerical value - yet it shows roughly how much (you can distinguish between low / medium / high)

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50
Q

What are the 2 types of glucose

A

Alpha
Beta

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51
Q

What is beta glucose known as

A

An isomer

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52
Q

Non reducing sugar test

A

1) add 2cm3 of the sample being tested to 2cm3 of Benedict’s reagent in a test tube and heat in a gently boiling water bath for 5 mins
2)if Benedict’s reagent does not change colour form blue then a reducing sugar is not present
3) take a clean test tube and add another 2cm3 of the sample being tested from to 2cm3 of dilute hcl acidn
4) boil for 5 mins in a gently boiling water bath
5) neutralise by adding repeated spatulas of sodium hydrogen carbonate (check with PH paper)
6) now preform the Benedict’s test again: add 2cm3 of Benedict’s reagent to your resulting solution and heat for 5mmins in a gently boiling water bath
7) is a non-reducing sugar was present in the original sample, an orange/red precipitate Will form

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53
Q

Why is the sample boiled with hcl acid in the non reducing sugar testing practical

A

To break any (to hydrolyse) any glycosidic bonds

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54
Q

Why is the acidic solution neutralised using sodium hydrogen carbonate in the non-reducing sugar practical

A

Benedict’s test won’t work in acidic conditions

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55
Q

Describe a test for starch

A

Add iodine solution dissolved in potassium iodide solution to your sample - if Starch is present it will change form an orange to blue/black

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56
Q

Suggest a simple test that could be used to distinguish between a monosaccharide and a polysaccharide

A

Add monosaccharide + polysaccharide to separate test tubes and add water . Monosaccharides are soluble so will dissolve but polysaccharides are insoluble so won’t dissolve

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57
Q

Polysaccharides are polymers - from which monomers are they formed

A

Monosaccharides

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58
Q

What type of reaction is involved when monosaccharides units are joined togetehr

A

Condensation

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59
Q

What are the 3 main polysaccharides

A

Starch
Cellulose
Glycogen

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60
Q

What type of cell contains starch and if what form is it present

A

Plant cell
Starch grains

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61
Q

Is Starch a polymer of a or b glucose

A

a

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62
Q

Starch use in plants

A

For short term storage overnight when photosynthesis cannot occur
And in long term storage such a over winter

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63
Q

Where can large amounts of starch be found in plant s

A

Seeds and storage organs such as bulbs and potato tubers

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64
Q

What does starch from an important component fro

A

Diet and is the major energy source in most diets

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65
Q

Amylose or amylopectin?
A polymer of glucose

A

Both

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66
Q

Amylose or amylopectin?
Single unbranched chain

A

Amylose

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67
Q

Amylose or amylopectin?
Has side branches

A

Amylopectin

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68
Q

Amylose or amylopectin?
1,4 and 1,6 glycosidic bonds

A

Amylosepectin

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69
Q

Amylose or amylopectin?
Tightly compacted molecule

A

Amylose

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70
Q

Amylose or amylopectin
Only 1,4 glycosidic bonds

A

Amylose

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71
Q

Amylose or amylopectin?
Chain coiled into spirals, led by hydrogen bonds

A

Amylose

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72
Q

Example of monomers

A

Monosaccharides
Amino acids
Nucleotides

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73
Q

Example of monosaccharides

A

Glucose
Fructose
galactose

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74
Q

What is an isomer

A

Molecules with the same molecular formula as each other but with the atoms connected a differnt way

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75
Q

What reaction breaks down polyMyers into monomers

A

Hydrolysis

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76
Q

What 2 things can sugar be classified as

A

Reducing
Non-reducing

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77
Q

What is the general term for monosaccharides and disaccharides

A

Sugar

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78
Q

What is a more accurate way to compare the amount of reducing sugars in differnt solutions rather than observing colour change

A

Filter and way the precipitate

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79
Q

What do plants do when they needs more glucose for energy

A

Is breaks down starch to release glucose

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80
Q

What is starch a mixture of

A

2 polysaccharides of alpha glucose
Amylose and amylopectin

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81
Q

Describe amylose

A

A long, unbranches chain of alpha glucose, the angles of glycosidic bonds give it a coiled structure almost like a cylinder. This makes it more compact, so it’s really good for storage because you can fit more into a small space

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82
Q

Describe amylopectin

A

A long, branched chain of alpha glucose. It’s side branches allow enzymes that break from the molecule to get at the glycosidic bonds easily. This means that glucose can be released quickly.

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83
Q

Why do plants store glucose as starch

A

Starch is insoluble in water and doesn’t effect the water potential so it doesn’t cause water to enter cells by osmosis, which would make then swell.. this makes them good for storage

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84
Q

How do animals store excess glucose

A

As glycogen

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85
Q

What is glycogen similar to in structure

A

Amylopectin
Except it has loads more side branches

It is also very compact - so good for storage

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86
Q

What is cellulose made of

A

Long, unbranched chains of beta-glucose

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87
Q

What is formed when beta-glucose molecules bond together

A

Straight cellulose chains

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88
Q

What bond links cellulose chains

A

Hydrogen bond

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89
Q

The cellulose chains are liked together by hydrogen bonds to form ?

A

Strong fibres called microfibrils .
The strong fibres mean cellulose provides structural support for the cell

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90
Q

Why is starch well suited for it role in energy storage? - 5 reasons

A
  • insoluble + therefore doesn’t affect water potential so water is not drawn into cells by osmosis
  • large+ insoluble - it doesn’t diffuse out of cells
  • compact - lots can be stored in a small space
  • when hydrolysed it forms alpha glucose - both easily transported + readily used in respiration
  • branches form has many ends, each of which can be acted on by enzymes simultaneously meaning that glucose monomers are released very rapidly
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91
Q

Is starch found in animal cells

A

Never

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92
Q

In what type of organisms is glycogen found

A

Animals + bacteria but never in plant cells

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93
Q

Describe two ways in which glycogen is differnt from starch

A

Glycogen has shorter chains and is more highly branched

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94
Q

Where is glycogen stored within animals

A

As small granolas mainly in the muscles and the liver and

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95
Q

Describe and explain 4 ways in which the structure of glycogen suits its function

A

Insoluble so doesn’t tend to draw water into cells by osmosis

Insoluble - doesn’t diffuse out of cells

Compact - a lot can be stored in a small space

More highly branches than starch so has more ends that can be acted in simultaneously by enzymes so more rapidly Borden down to form glucose monomers (which is used in respiratuon)

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96
Q

Which monomers join to form the polysaccharide cellulose

A

Beta - glucose

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97
Q

Which structure of a plant cell contains large amounts of cellulose

A

Cell wall

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98
Q

Describe 2 functions of a cell wall

A

Prevents cell from bursting as water enter by osmosis (does it by exerting an inward pressure to stop any further influx of water

Strengthens the cell wall + provides rigidity to the plant cell

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99
Q

How is the structure of cellulose suited to its function of providing support and rigidity

A
  • cellulose molecules are made up of b-glucose and so form long straight , unbranched chains
  • there cellulose molecular chains run parallel to each other and are crossed linked by hydrogen bonds which add collective strength

-These molecules are grouped to from microfibrils which in turn are grouped to form fibres all of which provide more strength

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100
Q

What is known as animal starch

A

Glycogen

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101
Q

Describe simply how you might identify the concentration of glucose in a solution of unknown concentration, less than one mol

A

1) dilute the stock solution
2) aim to make 5 to 6 different glucose solutions
3) preform the Benedicts test on each one
4) filter precipitate dry constant mass and weight
5) graph.
6) Find unknown mass + use graph to find glucose conc.

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102
Q

What is a colourimeter

A

An instrument that beams a specific wavelength (colour) of light through a sample and measure how much light is absorbed

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103
Q

What are the 3 main classes of lipids

A

Triglycerides
Phospholipids
Waxes

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104
Q

What are the 4 main roles of lipids In living organisms

A

Source of energy

Waterproofing

Insulation

Protection

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105
Q

What are lipids main roles in living organisms - source of energy

A

When oxidise lipids provide more than twice, the energy of the same mass of carbohydrates and release valuable water

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106
Q

What are lipids main roles in living organisms - waterproofing

A

Lipids are insoluble in water, and therefore useful as a waterproofing. Both plants and insects have waxy lipid cuticles that conserve water.
mammals produce only secretion from glands in the skin.

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107
Q

What are lipids main roles in living organisms -insulation

A

Fats are slow Conductors of heat, and when stored beneath the body surface, they help to retain body heat. They also act as electrical insulator in the myelin sheath around the nerve cell

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108
Q

What are lipids main roles in living organisms - protection

A

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

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109
Q

What are the major components of triglycerides

A

Glycerol
3x fatty acids

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110
Q

Formula of glycerol

A

C3H8O3

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111
Q

Formula of fatty acid

A

R- COOH

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112
Q

What is a hydrocarbon chain

A

A chain of only hydrogen and carbon

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113
Q

What letter is used to represent a hydrogen chain in fatty acids

A

R

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114
Q

What does saturated mean

A

No C=C double bond in the hydrocarbon chain

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115
Q

What does unsaturated mean

A

1 or more C=C double bonds in hydrocarbon chain

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116
Q

What does a double bond in fatty acid cause the molecule to do

A

Bend
They cannot pack together as closely so the triglyceride would be liquid at room temp (eg oil)

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117
Q

Fats that are solid at room temp (eg, butter) have more what bonds

A

Saturated fatty acids

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118
Q

Liquids at room temp have more what bonds

A

Unsaturated fatty acids

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119
Q

What type of reaction is involved in triglycerides formation

A

Condensation

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120
Q

What type of bond is in triglyceride

A

Ester bond

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121
Q

Are triglycerides polymers

A

No as they arnt made of repeating polymer units

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122
Q

Describe how a phospholipid differnt in structure compared to a triglyceride

A

Phospholipid and triglyceride both have a glycerol, but in phospholipid one of the 3 fatty acid has been replaced by a phosphate group

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123
Q

The phosphate head in phospholipids is …. (In terms of water)

A

Hydrophilic - attracted to / interacts with water

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124
Q

The fatty acid tails in phospholipids is …. (In terms of water)

A

Hydrophobic - repels water but mixes readily with fat

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125
Q

Due to having hydrophilic heads and hydrophobic tails, the phospholipid molecule is…?

A

Polar

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126
Q

When a phospholipid molecule is placed on the surface of water - what is formed

A

Monolayer

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127
Q

What is formed when a phospholipids is mixed into the water

A

Micelle

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128
Q

What is formed when there is water on both sides of a phospholipids.
Eg,

A

Forms a phospholipid bilayer with a hydrophobic core

Eg. In cell membranes

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129
Q

What is the test for lipids

A

1) take a dry and grease free test tube
2) to 2cm3 of the sample being tested add 5cm3 of ethanol
3) shake the tube thoroughly to dissolve any lipid in the sample
4) add 5cm3 of water and shake gently
5)a cloudy white coloured (white emulsion) indicates the presence of a lipid

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130
Q

Where are inorganic ions found

A

Cytoplasm of cells and in the body fluids of organisms

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131
Q

Define ion

A

Charged particle due to loss or gain of electrons

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132
Q

Distinguish between cations and anions

A

Cations have a positive change and anions have a negative charge

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133
Q

Formula of phosphate ion

A

PO4 3-

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134
Q

Function of a phosphate ion

A
  • a component of DNA and ATP and ATP
  • major constituent of bone and teeth
  • a component of cell membranes, on the form of phospholipids
  • it’s the bonds between phosphate groups that store energy in ATP
  • the phosphate groups in DNA and RNA z allow nucleotides to join to form the polynucleotides
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135
Q

Formula of a sodium ion

A

Na +

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136
Q

Function of a sodium ion

A
  • involved in the co-transport of glucose and amino acids across cell- surface membranes
  • helps to maintain electrical, osmotic and anion/cation balence across cell membranes
  • a molecule of glucose or an amino acid can be transported into a cell alongside sodium ions. This is known as co-transportation
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137
Q

Formula od iron ion

A

Fe 2+
Fe. 3+

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138
Q

Function of an iron ion

A

Forms part of haemoglobin (within the haem group)

Found in electron carriers used in respiration and photosynthesis

It’s made up of 4 differnt polypeptide chains, each with an iron ion in the centre

When oxygen is bound, the fe 2+ ion temporary becomes a fe 3+ ion until oxygen is released

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139
Q

Formula of hydrogen

A

H+

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140
Q

Function of hydrogen

A

PH is a measure of the conc. of this ion; the more of this ion , the lower the PH

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141
Q

Function of magnesium ion

A

Found within the chlorophyll molecule

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142
Q

What is an Organic molecule

A

Molecules that contain carbon and gap hydrogen and can include other elements

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143
Q

What is ATP

A

Adenosine TriPhosphate

  • a nucleotide
  • an energy carrier/ chemical used in living organisms to transfer energy
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144
Q

What makes up ATP

A

Adenine (base)
Ribose (5 sugar carbon)
3x phosphate

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145
Q

ADP + Pi
What does Pi stand for

A

Inorganic phosphate

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146
Q

How does ATP store energy

A

In the bonds

The bonds between the phosphate groups are unstable and so have a low activation energy - so are easily broken - when this happens energy is released.
Usually only the terminal phosphate is removed

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147
Q

What type of reaction is ATP synthesis

A

Condensation
Needs and input of energy

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148
Q

What is ATP synthesIs catalysed by

A

Enzyme ATP synthase

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149
Q

What is ATP hydrolysis catalysed

A

Enzyme ATP hydrolase / ATPase

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150
Q

what does ATP hydrolysis release

A

Energy

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151
Q

T or f
The conversion of ATP to ADP is reversible

A

T

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152
Q

What is the name for an addition of a phosphate group

A

Phosphorylation

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153
Q

Energy is needed for phosphorylation
What 3 reactions can give the energy needed

A

Photophosphorylation (light - photosynthesis)

Oxidative phosphorylation
Substrate-level phosphorylation
( respiration reactions)

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154
Q

ATP synthesis reaction

A

ADP + Pi —> ATP + H2O

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155
Q

ATP hydrolysis reaction

A

ATP + H20 —> ADP + Pi + (energy)

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156
Q

Why is ATP not a good long term energy store

A

Due to its instability of its phosphate bonds

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157
Q

Why is ATP better than glucose for immediate energy

A
  • hydrolysis of 1 ATP molecule releases less energy than each glucose molecule. The energy for reactions is therefor being released in smaller and more manageable quantities than that released by glucose
  • ATP is broken (hydrolysed) in a single step reaction and so energy is release is quicker (ATP is readily hydrolysed), the breakdown of glucose is a long series of reactions such that energy release takes much longer.
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158
Q

What are the lipids found in cell membranes called

A

Phospholipids

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159
Q

Why are triglycerides insoluble in water

A

The tails are hydrophobic

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160
Q

Why are triglycerides mainly used as energy storage molecules
+ why don’t they affect water potential in a cell

A

1) the long hydrocarbon tails of the fatty acids contain lots of chemical energy - a load of energy is released when there broken down . Because of these tails, lipids contain about twice as much energy pre gram as carbohydrates

2)they’re insoluble, so they don’t affect the water potential of the cell amd cause water to enter the cells by osmosis (which would make them swell) the triglycerides clump together as insoluble droplets in cells becuase the fatty acid tails are hydrophobic - the tails face inward shielding themselves with th water from there glycerol heads

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161
Q

Why can’t water-soluble substances easily pass though the cell membrane

A

The centre of the bilayer is hydrophobic
The membrane acts as a barrier to those substances

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162
Q

Plant and animal cells release energy from glucose via

A

Respiration

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163
Q

A cell can’t get its energy directly from glucose
So..

A

In respiration the energy released from glucose is used to make ATP

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164
Q

What is ATP known as and why

A

Nucleotide derivative because its a modified form of a nucleotide

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165
Q

Once ATP is made - where does it go

A

ATP diffuses to the part of the cell that needs energy

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166
Q

Where is the energy stored in ATP

A

In high energy bonds between the phosphate groups.
It’s released via hydrolysis reactions

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167
Q

When energy is needed by a cell ATP is broken down into “

A

ADP and Pi

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168
Q

ATP hydrolysis can be ‘coupled’ to other energy requiring reactions in the cell
- what does this mean

A

The energy released can be used directly to make the coupled reaction happen, rather than lost as heat

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169
Q

From ATP broken down , what can the Pi be used for

A

Added to another compound (called phosphorylation) which oftern makes the compound more reactive

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170
Q

What does ADP stand for

A

Adenosine diphosphate

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171
Q

What is an ion

A

An atom or group of atoms that have an eletrical charge

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172
Q

What are the 5 uses of ATP

A

Metabolic processes
Movement
Active transport
Secretion
Activation of molecules

173
Q

ATPs use in metabolic processes

A

Energy For building up macromolecules from their basic units
Eg. Starch from glucose

174
Q

Use of ATP In movement

A

Energy for muscle contraction, in muscle contraction, ATP provides energy for the filament of muscle to slide past each other + therfore shorten the actual length of the muscle fibre

175
Q

Use of ATP in active transport

A

Energy to change the shape of carrier proteins in plasma membranes- allows molecules or ions to move against the concentration gradient

176
Q

Uses of ATP in secretion

A

ATP is needed to from the lysosomes necessary for the secretion of cell products

177
Q

Use of ATP in activation of molecules

A

Inorganic phosphate released during the hydrolysis of ATP can be used to phosphorylate other compounds in order to make them more reactive , thus lowering activation energy in enzyme - catalysed reactions
Eg. Addition of phosphate to glucose molecules at the start of glycolysis

178
Q

Why is ATP continuously produced

A

ATP can’t be stored so it Is continuously produced to be used as an immediate energy source. Also ATP can’t diffuse in + out of cells

179
Q

Waters chemical formula

A

H2O

180
Q

What are water molecules described as being

A

Polar

181
Q

Why are water molecules described as being polar

A

The hydrogen atoms have a slight positive change and the oxygen has a slight negative change .

182
Q

Why are water molecules polar

A

It’s due to the uneven distribution of electrons

183
Q

Why do hydrogen bonds form between adjacent water molecules

A

Opposite changes attract so attractive forces called hydrogen bonds form

184
Q

Why is cohesion

A

The tendency of molecules to ‘stick’ together

185
Q

Does water have a strong or weak cohesion

A

Strong

186
Q

What does water having a strong cohesion explain in plants

A

Explains why long columns of water can be pulled upward through the xylem vessels of tall trees in the process of transpiration

It also explains surface tension which allows small animals to walk on water

187
Q

What does it mean that water has a relatively high heat capacity

A

It doesn’t change temperature easily

188
Q

How is water having a high heat capacity usefull

A

It minimises fluctuations in temperature, aquatic organisms such as fish can live in very stable environments, it also helps larger organisms which are mainly composed of water maintain a stable temp.

189
Q

What does it mean that water has a relatively large latent heat of vaporisation

A

Water requires a lot of energy to change state from a liquid to a gas.

190
Q

What is water having a large latent heat of vaporisation due to

A

The hydrogen bonding between water molecules making them more difficult to separate

191
Q

Why is water having a large latent heat of vaporisation usefull

A

Ensures that sweating in animals and transpiration in plant are effective cooling mechanisms - as water evaporates it extracts heat from around it, cooling the organism

192
Q

T or f
Water is a very good solvent

A

T

193
Q

Water is not easily compressed so it can be used to provide an internal ……..

A

Support

194
Q

What % of our cells content is water

A

80%

195
Q

Functions of water

A

A metabolite
Solvent
Temperature contr9
Cohesive

196
Q

Examples of what water is a metabolite in

A

Condensation and hydrolysis reactions

197
Q

What is a metabolic reaction

A

Chemical reaction that happens in a living organism to keep the organism alive. a metabolite is a substance involved in a metabolic reaction

198
Q

What is the name of the bonding between the negatively charges oxygen and positive hydrogen on other water molecules

A

Hydrogen bonding

199
Q

How is water an important metabolite

A

Many metabolic reactions involve condensation or hydrolysis
Hydrolysis requires a molecule of water to break a bond and condensation released a molecules of water when a new bond is formed

200
Q

Why can water buffer changes in temp

A

Hydrogen bonds between water molecules can absorb a lot of energy
So water has a high specific heat capacity - it takes a lot of energy to heat it up

201
Q

Why is water being able to buffer temperature useful

A

Means that water doesn’t experience rapid temp change.
Makes water a good habitat because the temp under water is likely to be more stable than on land. The water inside organisms also remain at a fairly stable temp,- helping them maintain a constant internal body temp

202
Q

What makes water a usefull solveny

A

Polarity

203
Q

What is cohesion

A

The attraction between molecules of the same type
Water molecules are very cohesive as they are polar

204
Q

What does strong cohesion make water do

A

Flow
Great for transporting substances
+ has a high surface tension when it comes into contact with air

205
Q

Are proteins polymer

A

Yes

206
Q

From which monomer units are they formed

A

Amino acids

207
Q

Which four elements are found in all proteins

A

Carbon
Hydrogen
Oxygen
Nitrogen

208
Q

When element is found in some proteins

A

Sulphur

209
Q

Are proteins organic or inorganic molecules

A

Organic

210
Q

Name 6 functions of proteins

A

Structural
Catalytic
Regulatory
Transport
Immunological
Cell transport + recognition

211
Q

Function of proteins as cell transport + recognition

A

Some proteins act as membrane pumps, channels and receptors

212
Q

Function of proteins are transport examples

A

Carrier molecules such as haemoglobin

213
Q

Examples of proteins are immunological function

A

Antibodies

214
Q

Examples of proteins as regulatory

A

Hormones such as insulin, glucagon and Adrenalin

215
Q

Examples of proteins as structural proteins

A

Collagen and keratin

216
Q

Examples of proteins as catalytic

A

Enzymes
Eg. Amylase, lipase

217
Q

How many naturally occurring amino acids are there

A

20

218
Q

What does an amino acid general structure consists of

A

Central carbon atom
Amino group
R group
Carboxyl group

219
Q

Which group in an amino acid is chemically basic

A

Amino group

220
Q

Which group in an amino acid is acidic

A

Carboxyl

221
Q

What letter in an amino acid represents the variable group

A

R

222
Q

What is the smallest amino acid

A

Glycine

223
Q

What reaction joins 2 amino acids together

A

Condensation

224
Q

What are the products formed when 2 amino acids join together

A

Water
Dipeptide

225
Q

What is the bond formed in between 2 amino acids

A

Peptide bond

226
Q

Many amino acids can join up in a series of condensation reactions to form an unbranched chain called.
And through what process?

A

Polypeptide
Polymerisation

227
Q

What is always at the end of a polypeptide

A

The N-terminus (amino group)
The C terminus (Carboxylic acid group)

228
Q

Can proteins consist of one or more polypeptides

A

Yes

229
Q

How do u test for a protein

A

Add burnet
Changes from blue to purple

230
Q

What are the 4 levels of organisation of protein structure

A

Primary
Secondary
Tertiary
Quaternary

231
Q

Describe the primary structure of the organisation of a protein

A

The specific order of amino acid in a protein

232
Q

Describe the secondary structure of the organisation of a protein

A

The rotation or twisting of a polypeptide chain into a repeating pattern such as an a-helix or b-pleated sheet

233
Q

Describe the tertiary structure of the organisation of a protein

A

The overall 3D structure of a polypeptide as the result of interachain interactions between R groups

234
Q

Describe the quaternary structure of the organisation of a protein

A

The linking together of more than one polypeptide chain

235
Q

What bonds are involved in the primary structure of proteins

A

Peptide

236
Q

What bonds are involved in the secondary structure of proteins

A

Hydrogen bonds between the peptide bonds

237
Q

What are the bonds in the tertiary structure of a protein

A

Hydrogen bonds,
Ionic bonds
Disulphide bridges

238
Q

What are the bonds in the quaternary structure of a proteins

A

Peptide
Hydrogen
Ionic
Disulphide

239
Q

Is the primary structure present in all proteins

A

Yes

240
Q

Is the secondary structure present in all proteins

A

Yes

241
Q

Is the tertiary structure present in all proteins

A

Yes

242
Q

Is the quaternary structure present in all proteins

A

No

243
Q

When is a polypeptide formed

A

When 2 or more amino acids join together

244
Q

What are proteins made from

A

One or more polypeptides

245
Q

When do disulphide bridges form

A

Whenever 2 molecules of the amino acid cysteine come close together
The sulfur atom in one cystesine bound to the sulfur atom in the other.

246
Q

For what proteins is tertiary the final structure

A

Proteins made from a single polypeptide chain

247
Q

Examples of when the quaternary structure is the final 3D structure

A

haemoglobin
Insulin
Collagen

248
Q

Shape of enzymes + why

A

They’re usually roughly spherical in shape due to the tight folding of the polypeptide chains

249
Q

Are enzymes soluble

A

Yes

250
Q

Enzymes examples of roles

A

In metabolism
Synthesis large molecules

251
Q

What are antibodies made up of

A

2 light polypeptide chains and 2 heavy polypeptide chains bonded together
They have variable regions
The amino acid sequence in these regions vary greatly

252
Q

Explain transport proteins

A

Channel proteins are present in cell membranes. Channel proteins contain hydrophobic and hydrophilic amino acids which cause the protein to fold up and form a channel.
These proteins transport molecules and ions across membranes

253
Q

What do structural proteins consist of

A

Long polypeptide chains lying parallel to each other with cross links between them
Eg, keratin and collagen

254
Q

What is the test for portion

A

1) the test solution needs to be alkaline, so first you add a few drops of sodium hydroxide solution
2) then add some copper (ll) sulfate solution
- if the protein is present it will turn purple
- if there are no proteins it will stay blue

255
Q

Definition of the secondary structure of proteins

A

The secondary structure refers to the folding of a polypeptide chain as a result of hydrogen bonds forming between peptide bonds within the chain, resulting in regions called alpha-helices or beta-pleated sheets

256
Q

Define disulphide bonds

A

Form between two amino acids that contain thiol (SH) groups. The two SH groups can be oxidised and join together to form a disulphide bond, its a strong covalent bond

257
Q

Explain ionic bonds in the tertiary structure

A

Formed between amino acids with negatively charged R-groups and Those with positively charged R-groups, these are stronger than hydrogen bonds but weaker than disulphide bridges

258
Q

Definition of tertiary structure

A

The tertiary structure is the 3rd shape of a polypeptide caused as a result of intrachain bonds between Rgroups of differnt amino acids. The bonds involved in the tertiary structure inculde: ionic bonds, hydrogen bonds and disulphide bridges

259
Q

How many polypeptide chains link to form the quaternary structure

A

Two or more

260
Q

When are bonds said to be interchain

A

The R- grounds of amino acids within differnt polypeptide chains can form bonds with one another two form the overall proteins.
Said to be interchain binds because they are between differnt polypeptide chains

261
Q

Explain the structure of haemoglobin

A

4- protein chains
- 2 alpha and 2 beta each with a ring like heme group containing an iron atom

262
Q

Describe the structure of insulin

A

2 long amino acid chains or polypeptide chains

263
Q

Describe the structure of collagen

A

3 chains
-wound together in a triple helix

264
Q

Explain how a change in the sequence of bases in DNA a may prevent an enzyme from carrying out its normal function

A

1-

265
Q

From which biological molecules are all enzymes made

A

Proteins

266
Q

What monomer units are joined together to build a enzyme

A

Amino acids

267
Q

What is a biological catalyst

A

They give an alternate reaction pathway with a lower activation energy to increase rate of reaction in living organisms
They are not used up

268
Q

Are enzymes vital for life

A

Yes
Body reactions would be too slow to sustain life

269
Q

What does intracellularly working enzymes mean

A

enzymes use the inside of cell

270
Q

What are extracellularly working enzymes

A

Released from other cells

271
Q

Explain the lock and key model

A

The enzyme acts as a lock and substrate as a key
As keys are specific to locks substrates are specific (complementary) to enzymes

272
Q

Can enzymes by used again

A

Yes
It’s active sight stays almost the same so remeians complementary

273
Q

Explain how enzymes can be involved in anabolic and catabolic reactions.

A

Catabolic breaks the substrate up (big molecules to small)
Anabolic builds up molecules

274
Q

What determines an enzymes function

A

There 3D shape
(Tertiary structure)

275
Q

What is enzymes tertiary structure determine by

A

The position of hydrogen, ionic and disulphide bonds that forms between the r-groups of amino acids. These bonds cause the polypeptides to fold up into a specific overall 3D structure

276
Q

When the substrate binds to the active site what is it called

A

Enzyme-substrate complex

277
Q

Why are products released from the active sight

A

As they are no longer complementary to the active site

278
Q

Explain how a change in primary structure of a protein may prevent an enzyme from carrying out its normal function
(Exam Q)

A

1) a change in the primary structure means a differnt sequence of amino acids
2) this means that the type and or order of the R group has changed
3) this changed the type and the position of hydrogen, ionic and disulphide bonds that form between the R groups
4) eg. If additional cysteine amino acid appears in the polypeptide, extra disulphide bonds may be formed in new locations
5) the protein folds into differnt overall tertiary structure
6) the active site of the enzyme may have a new shape
7) the substrate is no longer able to bind to the active site
8) the enzyme can or carry out its normal function

279
Q

What is the activation energy

A

The minimum amount of energy required for a reaction to start

280
Q

What do enzymes do to activation energy

A

Lower it

281
Q

Describe two ways in which energetics of with/without catalysts are the same

A
  • reactants and products have the same energy at the start and end
  • releasing same amount of energy overall in both reactions
282
Q

How do enzymes lower activation energy

A

They split up the reaction into several stages, each which has a smaller activation energy.
Eg, the substrate first binds to the enzymes to form an enzymes substrate complexm then the products are formed, then the products are released.
Each of these smaller steps require less energy. Without an enzyme the substrate is converted directly into products

283
Q

What do enzymes allow for reactions

A

To take place at lower temperatures.
More molecules will have the necessary lower energy to allow the reaction to proceed
Product is formed more quickly -
The rate of reaction has increased
This allows some metabolic processes to occur rapidly at human temps.

284
Q

Except form breaking up into several stages how else do enzymes lower activation enru

A
  • the formation of an enzyme substrate complex might bring the substrate molecules close together and in the correct orientation, making it easier and more probable that a reaction will occur
  • the enzyme may put the substrate molecules under stress so that bonds are weakened and therefore bonds may break easier
285
Q

Who proposed the lock and key model + when

A

German chemist
Emil Fischer in 1894

286
Q

What does the lock and key model propose

A

That emzymes work in the same way as a key operates a lock; each key has a specific shape that will only fit into and therfore open a particularly shapes, single lock. In this way , the tow fit together a bit like rigid puzzle pieces

287
Q

How long did lock and key stay the accepted theory

A

60 years

288
Q

Why was the lock and key model repelac3s

A

New experimental techniques allowed researchers to probe enzyme action more closely,
A number of observations began to emerge that did not fit with the lock and key model

289
Q

When and who replaced the lock and key theory

A

1950s
Daniel Koshland

290
Q

What did new techniques reveal about enzymes

A

Proteins are not rigid structure
Other molecules were showed to bind to enzymes away from the active site and actually alter the shape of the enzyme. This shows that enzymes are flexible and able to change shape rather than being fixed, rigid structures.

291
Q

What is a limitation of lock and key model

A

It could not explain non-competitive inhibiation

292
Q

What theory did Koshland propose

A

Induced fit model

293
Q

What is rhe induced Fit model

A

Enzyme is not a rigid lock but it actually changes shape slightly to fit the profile of the substrate.
Before the substrate Bind to the enzyme, the substrate and the active site are not precisely complimentary in shape as the substrate binds, the active site, changes, shape and moulds more closely around the substrate to form the functional active site.
The proximity of the substrate therefore induces the active site to adopt a perfect fit as the active site changes, shape, substrate molecule are put under tension

Once the product leaves rhe active sire relaxes back to the original position

294
Q

When did Koshland induced fit theory become accepted

A

Had to wait for the development of a technique known as x-ray crystallography, which allowed scientists to measure very small movements of chemical groups in the active site. With research becoming more technical, involving specialist knowledge

295
Q

Suggest why the induced fit model can be likened to a hand in a glove

A

The glove is complementary to the hand alike the active site to the enzymes is not rigid and slightly changed shape to give the perfect fit for the hand (like the perfect fit for substrates)

296
Q

What is the multi-disciplinary approach

A

Lots of differnt researchers Woking together

297
Q

What must happen for enzymes or work

A

Come into physical contact with its substrate
Have an active site which fits the substrate

298
Q

What factors influence rate of enzyme catalysed reactions

A

Temperature
PH
Enzyme concentration
Substrate conc

299
Q

How can you track progress of an enzyme controlled reaction

A

Formation of prodcuts over time
Substrate disappearing

300
Q

Describe the graph wich shows product forming over time

A

-at first, there is a lot of substrate, but no product
-It is easy for the plentiful substrate molecule to come into contact with empty active site on enzyme molecules
- at any given moment all of the enzymes, active sites are filled The substrate is rapidly broken down into products
-the reactions proceed and the substrate is converted into products, the substrate concentration decreases while the products concentration increases
-is difficult for substrate molecules to interact with enzyme molecules as there are fewer substrate, molecules and product molecules may get in the way
-It therefore takes longer for substrate molecules to be broken down, and so the rate of substrate disappearance/product formation slows
-The rate of reaction slows until there is so little substrate left that any further substrate disappearance/product formation cannot be measured
-The graph flatten out because all the substrate has been used up and so no product can be formed

301
Q

How to estimate rate of reaction at a specific point

A

A tangent
Find gradient

302
Q

What do enzymes do

A

Catalyse metabolic reactions at a cellular level and for organisms as a whole

303
Q

If two substrate molecules needed or be joined up how does an enzyme reduce activation energy

A

The enzyme holds them close together, reducing any repulsion between the molecules so they can bind easier

304
Q

Rate of enzyme controlled reaction …….. when the temp increases

A

Increases

305
Q

Why does temp increase rate of reactiom

A

More kinetic energy so molecules move faster.
Makes enzymes more likely to collide with the substrate molecule.
The energy of the collisions also increases, which means each collision is more likely to result in a reaction
But if the temp gets Too high the reactions tops

306
Q

Describe the temp and rate of reaction graph look

A

1) the rise in temp makes enzyme molecules vibrate more
2) if the temp goes above a certain level thus Vibration breaks some of the bonds that hold the enzyme in shape
3) the active sire changes shape and the enzyme and substrate no longer fit together
4) at this point the enzyme is denatures - it no longer functions as a catalyst

307
Q

What is human enzymes optimum temp

A

37°c

308
Q

What is rhe optimum PH for human enzymes

A

7
Some exceptions such as pepsin that works best at 2 (this is usefull as it’s found in the stomach)

309
Q

What happens to enzymes when the ph is above or below the optimum

A

The H+ and OH- ion found in acids and alkalis can mess up the ionic and hydrogen bonds that hold the enzymes tertiary structure in place. This makes the active site change shape, so the enzyme is denatured.

310
Q

How does enzyme concentration affect enzyme rate of reaction

A

The more enzyme molecules there are in a solution, the more likely a substrate molecule is to collide with one and form an enzyme substrate complex. So increasing the concentration of the enzyme increases rate of reaction.

311
Q

Why can the top of a rate of reaction to conc of enzymes level of

A

If the amount of substrate is limited, there come a point where there’s more than enough enzyme molecules to deal with all the available substrate so adding more enzymes has no further effect

312
Q

How does substrate conc effect rate of reaction up to a point

A

The higher the substrate conc, the faster the reaction- more substrate molecules means collision between substrate and enzyme is more likely and so more active sites will be used

This is only true up to saturation point. (All active sites full) adding more makes not differnce.

Substrate conc decrease with thin during a reaction so if no other variables are changed the rate of reactaiom will decreases over time too

313
Q

How can you measure the rate of an enzyme- controlled reaction due to temperatures
By collecting a gas

A

Catalase catalyses the breakdown of hydrogen peroxide into water and oxygen
1) set up boiling tubes containing the same volume and concentration of hydrogen peroxide. To keep the ph constant, add equal volumes of a suitable buffer solution, add equal volumes of a suitable buffer solution to each tube. (Buffer added to resist changes to ph when smau amounts of acne or alkali are added
2) set up the apparatus, either with a gas, syringe, or an upsidedown measuring cylinder in a trough of water
3) put each boiling tube in a water bath to a different temperature along with another tube containing catalase and wait five minutes
4) use a puppet to add the same volume and concentration of catalase to each boiling tube, then quickly attach the bung and delivered tube (at school. We use potatoes)
5) record how much oxygen is produced every 30 seconds using a stopwatch. Repeat each temperature three times.
6) calculate the average rate of reaction each temperature

314
Q

How to measure rate of enzyme controlled reactions by measuring how just the substrate is broken down.

A

The enzyme amylase catalyses the breakdown of starch to maltose
you can set up the experiment with a spotting tile with drops of iodine in potassium iodide .
A drop of iodine in potassium iodide is put into each well on a spotting tile a known concentration and relays and starch, and then mixed together in a test tube
A dropping pippett is used to put a drop of this mixture into one of the wells containing the iodienevsolution on the spotting tile, a regular intervals, and the resulting colour is observed

The iodine solution goes dark, blue black when starchis present, but remains its normal orange colour when no starch is present
you can see how fast amylase is working by recording how long it takes for the iodine solution to turn blue black when starch /amylase is added,

Repeate the experiment using different concentration of amylase (. repeat the experiment, three times for each amylase concentration.

315
Q

How to complete the practical:
The effect of temperature on the rate of an enzyme reaction

A

1) using a marker pen, write an x on the glass halfway down 3 test tubes
2) add 10cm3 of the solution of milk powder to each of these tree test tubes
3) add 2cm3 of trypsin solution to 2cm3 of PH7 buffer in another set of three test tubes
4) stand the three test tubes containing the solution of milk powder and the three test tubes containg trypsin and buffer in a water bath at 20°c
5) leave all 6 tubes in a water bath for 10 mins
6) mix one of each textures togerth
7) put back in water bath
8) repeate for the next 2 and then the next 2
9 time how long it takes for the milk to go clear ( when u can see the x)
10) record the time
11) repeate at temps, 30, 40, 50, 60

316
Q

2 types of inhibitors?

A

Competitive
Non-competitive

317
Q

What is a competitive inhibitor

A

Molecules that have a similar shape to that of the substrate molecule
They compete with the substrate to bind to the active site (but no reaction takes place)
They block the active site - sono substrate can fit in

318
Q

What does how much enzyme is inhibited depend on

A

The relative concentrations o the in inhibitor and the substrate

319
Q

If there is a high concentration a the competitive inhibitor how will it effect rate

A

It will take up all the active sites and hardly any of the substrates will get to the enzyme
So a lower rate of reaction

320
Q

What will happen if there is a higher concentration of substrate than competitive inhibitor

A

The substrate chances of getting to an active site before rhe inhibitor increase. So increasing the concentration of subsrate will increase rate of reaction ( up to a point)

321
Q

What is a non competitive inhibitor + how does it work

A

Bind to the enzyme away form its active site
Causes active site to change shape so the substrate molecule can no longer bind to it

322
Q

Why don’t non competitive inhibitors compete with substrate

A

Inhibitors don’t bind to the active site becuase they are a differnt shape

323
Q

How does increasing concentration of substrate effect rate of reaction with non competitive inhibitors

A

Inc, conc, of substrate won’t make any differnce to the reaction rate

324
Q

What does DNA carry

A

The genetic code

325
Q

What are both DNA. And RNA known as

A

Nucleic acids

326
Q

Why are DNA and RNA known as nucleic acids

A

They are weak acids

327
Q

What is the monomer nucleic acids are made from

A

Nucleotides

328
Q

Are nucleic acids polymers

A

Yes

329
Q

What elements does a nucleotide contain

A

Carbon
Hydrogen
Oxygen
Nitrogen
Phosphate

330
Q

What 3 components make up a nucleotide

A

1) a 5 carbon sugar called pentose
2) a phosphate group
3) a organic, nitrogenous base

331
Q

What is the formula for the phosphate group of nucleic acids

A

PO4 2-

332
Q

In DNA what is the sugar called

A

Deoxyribose

333
Q

What charge does the phosphate group in DNA have and what does it make DNA

A

Negative charge
Makes DNA a highlt charged molecule

334
Q

What properties does the negatively charges phosphate group give DNA

A

It’s acidic properties

335
Q

How many bases does DNA contain

A

R

336
Q

What elements does the 4 bases in DNA contain

A

Carbon
Hydrogen
Oxygen
Nitrogen

337
Q

What are the 4 bases of DNA known as

A

Adenine (A)
Thymine (T)

Cytosine (C)
Guanine (G)

338
Q

Which pairs bases have similar structures

A

C and T ( smaller)
And A G ( larger)

339
Q

What structure do thymine and cytosine have

A

A single ring structure called pyrimidines

340
Q

What is rhe structure of adenine and guanine

A

Double ring
Called purines

341
Q

Via what reaction are the deoxyribose sugar, phosphate and base assembles

A

Through condensation

342
Q

Deoxyribose sugar , phosphate and base are assembled through condensation reaction to form a ………….

A

Mononucleotide

343
Q

What is DNA made of

A

4 differnt types of nucleotides

344
Q

How do 2 nucleotide units combine together

A

Through condensation reaction between sugar and phosphate group

345
Q

What is the bind formed between sugar and phosphate in DNA called

A

Phosphodiester bond

346
Q

What is a phosphodiester bond

A

Strong covalent bonds between sugar and phosphate group in DNA

347
Q

When many nucleotides join up, what is it called?

A

Polynucleotide strand

348
Q

The 2 strands of DNA are joined by what?

A

Weak hydrogen bonds

349
Q

What form between the bases in DNA

A

Weak hydrogen bonds

350
Q

How many hydrogen bonds form between A and T

A

2

351
Q

How many hydrogen bonds form between C and G

A

3

352
Q

When and by who did Chargaffs rule of base pairing arise

A

1951
Edwin chargaff

353
Q

What did Edwin chargaff do

A

Analysed DNA from differnt species, he separated the 4 bases from DNA and measured them quantitatively.
He discovered that amount of A and T where very similar and C and G.
Later reasearch showed these bases must pair up

354
Q

Why does A or G have to pair whir C or T

A

Because the distance between rhe 2 polynucleotide strands must be constant. As A , G are double ringed (larger) if they paired it would be long ‘rung’ ( if C and T joined it would be short’ rung’)

The distance between the 3 sugar phosphate backbones can only be maintained by ATand CG bonding

355
Q

When and by who found the exact overall structure of DNA

A

1953
Crick and Watson

356
Q

If you had 21% of Adenine how much thymine should you have

A

21%
They pair together

357
Q

Why in virus DNA is there not the same amount of T and A bases

A

It’s single stranded

358
Q

What 2 strands are DNA made up form

A

Polynucleotide strands

359
Q

What are the 2 polynucleotide strands in DNA describes as

A

Anti parrallel
They run in opposite directions

360
Q

DNA has a ……………….. backbone

A

Sugar phosphate

361
Q

What is a sugar phosphate backbone

A

The alternating sugar and phosphate groups are joined together by strong covalent bonds called phophodiester bonds

362
Q

What is the structure of DNA

A

Double helix

363
Q

What do hydrogen bonds offer during DNA replication

A

Natural line of cleavage

364
Q

Describe DNA replication

A

1) DNA double helix is nicked and the hydrogen bonds between the complementary base pairs are broken
2) this occurs due to the action of hot enzyme helicase and results in the unwinding and separation of the two polynucleotides
3) bases are now exposed, the separate polynucleotides act as templets for the addition of free activated nucelotides
4) these pair with complement Barry vases that have been exposed on unwound DNA
5) once in position the enzyme DNA polymerase catalysed the linking together of the activated nucelousided through covalent phosphodiester bonds. Two new polynucleotides strands are formed
6) there are now 2 daughter DNA molecules each of which contains one of the orgiiinal stands of DNA and one new one
7) this is called semi conservative replication

365
Q

What enzyme nicks the hydrogen bonds in DNA and results in the unwinding and separation of the 2 polynucleotides

A

Helicase

366
Q

Is DNA replication active or passive

A

Active
Energy is needed for the process of activation of nucleotides

367
Q

Which enzymes catalysises the linking of the activated nucleotides through covalent phospdiester bonds

A

DNA polymerase

368
Q

What is the process of DNA replication called

A

Semi- conservative replication

369
Q

How does an increase in temperature effect rate of reaction

A
  • inc kinetic energy of enzyme and substrate molecules
  • moves more rapidly and collide more frequently with active site
  • more forceful collision so greater proportion release enough energy to overcome the activation energy - more enzyme-substrate complexes form
  • inc in rate
    -optimum temp = greatest rate of reaction
  • further inc, in temp over the optimum decreases the rates
  • because atoms within the enzymes vibrate so vigorously that it causes her hydrogen bonds (and some ionic ) to break rate of the reaction/This is because the atoms within the enzyme vibrate so vigorously that it causes the ….
    ..Tertiary structure of the enzyme changes, including the shape of the active site.
    At first this causes a small change in the shape of the active site such that the substrate fits less easily, decreasing the formation of …enzyme… - substrate complexes and decreasing the rate of the reaction. However, as the temperature continues to increase, the enzyme’s tertiary structure is so disrupted that the enzyme stops working altogether; we say that the enzyme is … denatured
    and enzyme-substrate complexes cannot form. This is a
    ..permanent change that cannot be reversed by cooling. Eventually a temperature is reached where, All of the enzyme molecules have been denatured; the rate of reaction falls to 0
370
Q

What is PH of a solution a measure of?

A

Concentration of hydrogen ions (H+) in a solution
More acidic is more hydrogen bonds

371
Q

What is rhe formula to calculate PH of a solution

A

-log 10(H+)
Negative logarithm of the hydrogen ion concentration

372
Q

What is the key feature of the PH graph on rate of reaction

A

It’s symmetrical

373
Q

How does PH effect rate of reaction

A

Denaturation occurs because changes in pH affect the charges. on the enzyme (including charges on amino acid side chains of the enzyme’s active site) and the substrate.

This could cause regions of the enzyme and substrate to adopt the Same electrical charge, thus causing electrostatic /repulsion.

Changes in pH could also cause ionic bonds and hydrogen bonds that maintain the enzyme’s tertiary structure to break.. The active site would therefore change ..Shape… and enzyme-substrate complexes would not from

374
Q

Describe rate of reaction in a low concentration of enzymes

A

There are too few enzyme molecules to allow all substrate molecules to find an active site at one time. The rate of reaction is therefore only half the maximum possible for the number of substrate molecules available

375
Q

Describe rate of reaction at optimum enzyme concentration

A

with twice as many enzyme molecules available, all the substrate molecules can occupy an active site at the same time.
The rate of reaction has doubled to its maximum because all active site are filled.

376
Q

Describe rate of reaction when enzyme concentrations has gone beyond the optimum

A

The addition of further enzyme molecules has no effect as there are already enough active sites to accomodate all the available substrate molecules. There is no increase in rate of reaction

377
Q

Describe rate of reaction with a low substrate concetnration on enzyme action

A

There are too few substrate molecules to occupy all the available active sites. The rate of reaction is therefore only half the maximum possible for the number of enzyme molecules available.

378
Q

Describe rate of reaction when substrate conc is at its optimum

A

With twice as many substrate molecules available, all the active sites are occupied at one time. The rate of reaction has doubled to its maximum because all the active sites are filled.

379
Q

Describe the rate of Reaction of substrate concentration past the optimum

A

The addition of further substrate molecules has no effect as all active sites are already occupied at one time. There is no increase in the rate of reaction

380
Q

What is an enzyme inhibitor

A

Directly or indirectly interfere with the functioning of the active site of an enzyme and in doing so reduce enzyme activity

381
Q

Are inhibitors permanent of not

A

Some bind permanently to the enzyme and are non reversible
But most only attach temporarily to the enzyme and so are known as reversible inhibitors

382
Q

What is the shape of competative inhibitors

A

3D molecular shapes that are very similar to the enzymes normal substrate

383
Q

How do competative inhibitors work

A

Competitive inhibitors have 3D molecular shapes that are very _Similar to that of an enzyme’s normal substrate. They can therefore compete with the substrate for an available actine
When the inhibitor molecule is bound to the active site, it prevents the normal Substrare from binding and so no enzume Substrate complex is formed. It therefore temporarily inhibits this enzyme molecule from catalysing its reaction - the rate of the reaction is therefore slowed down.

384
Q

What does the overall effect on enzyme activity depend on with competative inhibitors

A

The overall effect on enzyme activity (the rate of the reaction) depends on the relative amount of substrate and inhibiter molecules.

For example, if there were 99 substrate molecules for every inhibitor molecule, then 99% of collisions would be between enzyme and substrate and only 1% between enzyme and inhibitor. Consequently, at any one time, only 1% of the enzyme molecules would be inhibited and the reaction would proceed at_99% of the maximum rate. If the ratio was 75% substrate: 25% inhibitor, the rate would fall to 75% of its maximum.
For a fixed amount of inhibitor, an increase in substrate concentration reduces the effect of the inhibitor

Given that the inhibitors only bind temporarily to the enzyme, eventually a point will be reached when all substrate molecules will occupy an active site. However, the greater the concentration of inhibitor, the longer this will take.

385
Q

Where do non competative inhibitors bind

A

Allosteric site

386
Q

How do non competative inhibitors work

A

, non-competitive inhibitors do not compete with substrate molecules for the active site. Instead they bind to another area of the enzyme that is known as the ALLOSTERIC SITE! The binding of this inhibitor causes a change in Shape (conformational change) of the enzyme’s active site such that substrate molecules can no longer bind - the enzyme cannot lunchen The effectiveness of a non-competitive inhibitor is not affected by the concentration of the substrate -

387
Q

What is a metabolic pathway

A

A series of reactions in which each step is catalysed by a specific enzyme

388
Q

In any one cell how many different structured metabolic pathways are there

A

Hundreds of

389
Q

Where are the enzymes that control structures metabolic pathways

A

Attached to the inner membrane of the cell organelle in a very precise sequence

390
Q

Describe the loook of the rate of reaction graph of enzymes for the vol of o2 on time

A

• At first there is a lot of substrate (hydrogen peroxide or starch),
but no product (water and oxygen or maltose)

  • is is easy for the plentiful substrate molecules to come into contact with empty active sites on enzyme molecules

At any given moment all the enzyme active sites are filled the substrate is rapidly broken down into productions

As the reaction proceeas,and substrate is converted into product, The substrate concentration decreases untill The produce concentration increases

It Is more difficult for substrate molecue to come into contact with enzyme molecules as there are fewer substrate molecules may ‘get in The way’

It therefore takes longer for substrate molecules to be broken down, and so the rate of substrate disappearance slows

The rate of reaction slows until there is so little substrate left, but any further substrate disappearance cannot be measured

The graph. Flatterns out because all the subject has been used up and so no new product can be formed

391
Q

How can we track a enzyme controlled reaction

A

Formation of product over time
Substrate disappearing

392
Q

For an enzyme to work it must ….

A

Come into physical contact with its substrate

Have an active site which fits the substrate

393
Q

The level of chemicals in a cell can be maintained at relatively constant levels through a process called …..

A

End product inhibition

394
Q

How does end product inhibition work

A

If the level of end product increases in a cell above normal levels then this product can inhibit the action of an enzyme within the metabolic pathway, this prevents the substrate being converted into the next intermediate that needed the inhibited enzyme,
So ultimately less product will be produced
The levels will returned to Normal

395
Q

What type of inhibitors is end product inhibiation ususlalt

A

Non competative

396
Q

What is end product inhibition an example of

A

Negative feedback

397
Q

Why is end product inhibition important

A

It would be imifficeint to produce something that is in excess of what is required
High conc of some substances could be toxic and may damage the cell

398
Q

An enzyme controlled reaction is inhibited by substance x
Suggest a simple way in which you could tell whether substance x is acted as a competative or non competative I hibitor

A

Add lots more substare if the rate doesn’t increase its non competative
Is it does increase it is competative

399
Q

What were the only 2 possible mechanisms for DNA replication

A

Conservative model
Semi conservative model

400
Q

What is the conservative model

A

Suggested that the original DNA molecule remained inactive and that a separate daughter DNA copy was built up form new molecules of deoxyribose, phosphate and organic bases
Of the 2 molecules produced one would be made of entirely new materials while the other would be entirely origional material

401
Q

What is the semi conservative model

A

Proposes that the origional DNA molecule split into two separate strands each of which then replicated it mirror image

Each of the 2 new molecules would have one strand of new material and one origional strand

402
Q

Who found evidence for semi conservative replication

A

Meselsohn
Stahl

403
Q

What 3 facts where the semi conservative replication experiment based om

A

1) all the bases in DNA contain nitrogen
2) nitrogen has 2 forms : the lighter N14 and heavier N15
3) bacteria will incoporate nitrogen form their growing medium into any new DNA that they make

404
Q

Explain the semi conservative DNA replication experiment

A

They labelled the origional DNA of basketry by growing them on a medium of N 15
Then they transferred the bacteria to a medium of N14 for a single generation to allow it to replicate once

The mass of each new dna molecule would depend on which methord of replication has taken place

To separate out the differnt DNA types, they centrifuged the extracted DNA in a special solution
(Density gradient centrifugation )

The lighter the DNA the nearer he top of the centrifuge tube it collected

The heavier the DNA the n3arwr the bottom of the tube it collected

They also analysed the dna after 2,3 generation

405
Q

What part of DNA contains nitrogen

A

The bases

406
Q

Explain why after one generation all the DNA is made up of an equal mixture of N14 and N 15

A

DNA replication is semi conservative
This means the daughter dna has one new strand on each

407
Q

What does RNA stand for

A

Ribonucleic acid

408
Q

Describe the structure of RNA

A

Made of nucleotides (ribosesuga attached to nitrogenous bases and phosphate groups)
Mainly single strand
Bases (ACUG)

409
Q

What does mRNA stand ofr messenger ribosnucelic acid

A

To carry protein nformarion form DNA in a cell nucleus to the cells cytoplasm where ribosomes read the mRNA sequence and translated each 3 bases into its corresponding amino acid

410
Q

What does tRNA stand for

A

Transfer ribosnucleic acid

411
Q

What does tRNA do

A

Helps decode messenger RNA sequence into a protein
Function at specific sites in the ribosomes during translation

412
Q

What does rRNA stand for

A

Ribosomal ribonucleic acid

413
Q

What is rRNAs function

A

Part of the ribosomes
Responsible for reading the order of amino acids and linking amino acids together

414
Q

Why is DNA. Stable molecule

A

The phosphodiester backbone protects the more chemically reactive organic bases inside the double helix

Hydrogen bond link, organic, base pairs, forming bridges (rungs) between the phosphodiester upright. As there are three hydrogen bonds between cystine and guanine the higher proportion of
C and G , pairings, the most stable, the DNA molecule.

There are other interactive forces between the base pairs that hold the molecule together

415
Q

How has DNA adapted to carry out its function

A

1). It is a very stable structure which normally passes from generation to generation without change. Only rarely does it mutate

2) It’s two separate strands adjoined only with hydrogen bonds which allow them to separate during DNA replication and protein synthesis

3( it is an extremely large molecule and therefore carries an amount of genetic informatio

4) by having the base pairs within the helical cylinder of the deoxyribose phosphate backbone. The genetic information is to some extent, protected from being corrupted by outside, chemicals and physical forces.

5) base pairing leads to DNA, being able to replicate, and to transfer information as mRNA

416
Q

What does the function of DNA depend on?

A

Sequence of base pairs

417
Q

Function of rna

A

Transfer genetic information form dna to the ribosomes
Ribosomes read the rna to. Make polypeptides in translation

418
Q

What are ribosomes made from

A

RNA
Protein

419
Q

When was DNA first observed and what was the criticisms
What did some people believe

A

1800s
Lots of scientists doubted that it could carry the genetic code because it has a relatively simple chemical composition
Some belived that genetic info must be carried by proteins (which are more chemicaly varied)

420
Q

WhenDNA showed to carry the genetic code and what else was discovered in this year

A

1953
Double helix structure also discovered by crick and Watson

421
Q

What is shorter DNA or RNA

A

RNA

422
Q

What does a phosphodiester bond consist of

A

The phosphate group and 2 ester bonds in dna

423
Q

What is the bond between phosphate group and deoxyribose sugar

A

Ester bond

424
Q

How are the ends of DNA stands differnt

A

one end is called 3’ (three prime) end and one end called 5’

425
Q

How does the 3’ and 5’ end run in dna

A

In opposite directions
Antiparallell

426
Q

The active site of DNA polymerase is only complementary to what

A

The 3’ end of the Newley forming dna stand

427
Q

What end can DNA polymerase only add nucleotides too

A

New 3’ end

428
Q

What is the new strand of DNA made in in terms of 5’ Nad 3’

A

5’ to 3’ direction and that DNA polymerase moves down the template strand in a 3’ to 5’ direction
Because the strands int he double helix are anti parallel the dna polymerase working on one of the strands moves into the opposite direction to the DNA polymerase working on the other template strand

429
Q

Why did they use bacteria for the evidence of semi conservative replication

A

It’s divides quickly

A-level Biology (8 decks)

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