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Biology ALevel AQA 2023-2024-2025 > Topic 1 - Biological Molecules > Flashcards

Topic 1 - Biological Molecules Flashcards

1
Q

What are biological molecules?

A

Particular groups of chemicals that are found in living organisms.

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2
Q

What are all molecules made up of?

A

Atoms

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3
Q

what is Covalent bonding?

A

Atoms share a pair of electrons in their outer shells. As a result the outer shell of both atoms is filled and a more stable compound, called a molecule, is formed.

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4
Q

What is Ionic bonding?

A

Ions with opposite charges attract one another. This electrostatic attraction is known as an ionic bond. For example, the positively charged sodium ion Na+ and negatively charged chloride ion CI- form an ionic bond ro make sodium chloride. Ionic bonds are weaker than covalent bonds.

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5
Q

What is Hydrogen bonding?

A

The electrons within a molecule arc not evenly distributed but tend to spend more time at one position.
This region is more negatively charged than the rest of the molecule.
A molecule with an uneven distribution of charge is said to be polarised, in other words it is a polar molecule. The negative region of one polarised molecule and the positively charged region of another attract each other.
A weak electrostatic bond is formed between the two. Although each bond is individually weak, they can collectively form important forces that alter the physical properties of molecules.
This is especially true for water.

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6
Q

What are monomers?

A

Monomers are the smaller units from which larger molecules are made. These can be linked together to form long chains.

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7
Q

Name 3 examples of monomers :

A

Monosaccharides, Amino acids, Nucleotides.

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8
Q

What are Monomers of a polymer usually based on?

A

Carbon

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9
Q

What are polymers?

A

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

These are formed by polymerisation

Monosaccharides, amino acids and nucleotides are examples of monomers.

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10
Q

What are polynucleotides formed from?

A

From mononucleotide sub-units.

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11
Q

What are polypeptides formed by?

A

Polypeptides are formed by linking together peptides that have amino acids as their basic sub-unit.

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12
Q

What are Condensation reactions?

A

Reactions that produce water.
(Each time a new sub-unit is attached a molecule of water is formed).

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13
Q

How can polymers be broken down?

A

Through the addition of water.

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14
Q

What is a Hydrolysis reaction?

A

When water molecules are used when breaking the bonds that link the sub-units of a polymer (splitting the molecule into its constituent parts).

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15
Q

2 examples of a hydrolysis reaction :

A

Polypeptides can be hydrolysed into amino acids

Starch can be hydrolysed into glucose

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16
Q

What is metabolism?

A

All the chemical processes that take place in living organisms.

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17
Q

What is a molar solution?

A

A solution that contains one mole of solute in each litre of solution. A mole is the molecular mass (molecular weight) expressed as grams (=one gram molecular mass).

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18
Q

What are Carbohydrates?

A

Carbohydrates are carbon molecules (carbo) combined with water (hydrate). Some carbohydrate molecules are small while others are large.

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19
Q

What are carbon-containing molecules know as?

A

Organic molecules.

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20
Q

What is the chemical formula glucose?

A

C6H12O6

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21
Q

What is Alpha Glucose?

A

Alpha glucose is a cyclic hemiacetal form of glucose where at anomeric carbon, the position of hydroxyl group is in downward direction.

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22
Q

What is Beta Glucose?

A

Beta glucose is a cyclic hemiacetal form of glucose where at anomeric carbon the position of hydroxyl group is in upward direction.

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23
Q

In carbohydrates. the basic monomer unit is a sugar, otherwise known as a …

A

… saccharide.

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24
Q

What is a single monomer called?

A

A monosaccharide.

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25
Q

What is a pair of monosaccharides that are combined called?

A

A disaccharide.

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26
Q

Monosaccharides can also be combined in much larger numbers to form …

A

… polysaccharides.

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27
Q

What are monosaccharides?

A

Sweet-tasting, soluble substances.

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28
Q

What are some examples of monosaccharides?

A

Glucose, galactose and fructose.
Glucose is a hexose (6-carbon) sugar and has the formula C6H120 6. However, the acorns of carbon, hydrogen and oxygen can be arranged in many different ways. For example, glucose has two isomers ­ a-glucose and J3-glucose.

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29
Q

What sugars are reducing sugars?

A

All monosaccharides and all disaccharides except SUCROSE are reducing sugars.

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30
Q

What is reduction?

A

Reduction is a chemical reaction involving the gain of electrons or hydrogen.

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31
Q

What is a reducing sugar?

A

A reducing sugar is a sugar that can donate electrons to (or reduce) another chemical.

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32
Q

What is the test for a reducing sugar?

A

The test for a reducing sugar is known as the Benedict’s test.

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33
Q

What is Benedict’s reagent?

A

Benedict’s reagent is an alkaline solution of copper(D) sulfate.

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34
Q

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

A

When a reducing sugar is heated with Benedict’s reagent it forms an insoluble red precipitate of copper(I) oxide.

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35
Q

What two monosaccharides are combined together to form maltose?

A

Glucose & glucose

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36
Q

What two monosaccharides are combined together to form sucrose?

A

Glucose & fructose

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37
Q

What two monosaccharides are combined together to form lactose?

A

Glucose & Galactose

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38
Q

What bonds are formed during a Condensation reaction to form disaccharides?

A

Glycosidic bonds are formed when the monosaccharides join, a molecule of water is removed and the reaction is therefore called a condensation reaction.

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39
Q

When are glycosidic bonds broken?

A

When water is added to a disaccharide under suitable conditions, it breaks the glycosidic bond releasing the constirnenr monosaccharides. This is called hydrolysis (addition or water that causes breakdown).

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40
Q

What is a Hydrolysis reaction?

A

When water is added to a disaccharide under the suitable conditions, the glycosidic bond is broken and the monosaccharides are released. It is a Hydrolysis reaction because water is added in order to break down the disaccharide.

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41
Q

Before testing a non-reducing sugar, what must be done?

A

In order to detect a non-reducing sugar it must first be hydrolysed into its monosaccharide components by hydrolysis.

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42
Q

What is process of testing for NON-REDUCING SUGARS?

A
  1. Test the Sucrose with the Benedict’s solution to ensure that it is negative.
  2. Using a clean syringe, add 1cm° of Sucrose in a boiling tube.
  3. Add 1cm° of the 1M Hydrochloric Acid into the tube and swirl to mix.
  4. Place the tube into the water bath to heat up for 5 minutes and remove the tube using tongs. Allow to cool.
  5. Apply to spatulas of the Sodium Hydrogen Carbonate to the tube and wait until the fizzing stops.
  6. Add 1cm? of the Benedict’s solution and heat it in the water bath for 5 minutes.
  7. Check for any colour change and record the results and observations.
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43
Q

What are Polysaccharides? How are they formed?

A

Polysaccharides are polymers, formed by the condensation of many glucose units.

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44
Q

What are Glycogen, Starch and Cellulose formed by?

A

Glycogen & Starch - the condensation of alpha glucose.

Cellulose - the condensation of beta glucose.

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45
Q

Are polysaccharides insoluble?

A

Yes as they are very large molecules.

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46
Q

If polysaccharides are insoluble, why is it good?

A

This feature makes them suitable for storage.

When they are hydrolysed, polysaccharides break down into disaccharides or monosaccharides. Some polysaccharides, such as cellulose, are not used for storage but give structural support tO plant cells.

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47
Q

Starch is a polysaccharide found in plants, what is it in the form of?

A

Small granules or grains.

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48
Q

What is the test for STARCH?

A

Starch is easily detected by its ability to change the colour of the iodine in potassium iodide solution from yellow to blue-black.

  • Place 2 cm3 of tbe sample being tested into a test tube (or add two drops of the sample into a depression on a spotting tile).
  • Add two drops of iodine solution and shake or stir.
  • The presence of starch is indicated by a blue-black coloration.
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49
Q

What are 3 important Polysaccharides?

A

Starch, Glycogen, Cellulose

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50
Q

What is Starch?

A

A polysaccharide that is found in many parts of a plant in the form of small grains.

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51
Q

What is the main function of Starch?

A

Major energy source in most diets & stores glucose for respiration.

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52
Q

What monomer is Starch made from?

A

ALPHA GLUCOSE monosaccharides linked by glycosidic bonds that are formed by condensation reactions.

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53
Q

How is the structure of Starch related to its function?

A

– Large molecules SO insoluble SO does not affect water potential. Also water is not drawn into cells by osmosis.

– It is branched SO lots of ‘ends’ SO glucose is easily released for respiration.

– Coiled SO compact SO more can be stored in a small space.

– When hydrolysed it forms a-glucose, which is both easily transported and readily used in respiration.

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54
Q

Where is Glycogen found?

A

Animals and bacteria (never in plants).

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55
Q

Does Glycogen have shorter chains than Starch and is highly branched?

A

Yes.

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56
Q

What is Glycogen?

A

It is the major carbohydrate storage product of animals.

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57
Q

What is Glycogen stored as?

A

In animals it is stored as small granules mainly in the muscles and the Liver for respiration. The mass of carbohydrate that is stored is relatively small because fat is the main storage molecule in animals.

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58
Q

How is the structure of Glycogen related to its function?

A

– Highly branched meaning more ‘ends’ SO glucose can be released quickly for respiration.

– Compact SO a lot can be stored in a small space.

– Large SO insoluble SO does not affect water potential. Also does not tend to draw water into the cells by osmosis.

– It is more highly branched than starch and so has more ends that can be acted on simultaneously by enzymes. It is rherefore more rapidly broken down to form glucose monomers, which are used in respiration. This is important to an ima ls which have a higher metabolic rate and therefore respiratory rate than plants because they are more active.

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59
Q

What monomers is Cellulose made of?

A

Beta glucose.

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60
Q

What is the function of Cellulose?

A

Strengthens the plant cell wall.

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61
Q

Structure of Cellulose:

A

Cellulose has straight, unbranched chains.
These run parallel to one another, allowing hydrogen bonds to form cross-linkages between adjacent chains.
While each individual hydrogen bond adds very little to the strength of the molecule, the sheer overall number of them makes a considerable contribution to strengthening cellulose, making it the valuable structural material that it is.

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62
Q

What are Microfibrils?

A

Bundles of long chains of cellulose molecules. These are arranged in parcel groups called fibres.

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63
Q

Cellulose information :

A

Cellulose is a major component of plant cell walls and provides
rigidity to the plant cell.
The cellulose cell wall also prevents the cell from bursting as water enters it by osmosis.
It does this by exerting an inward pressure that stops any further influx of water.
As a result, living plant cells are turgid and push against one another, making non-woody parts of the plant semi-rigid.
This is especially important in maintaining stems and leaves in a turgid state so that they can provide the maximum surface area for photosynthesis.

64
Q

How is the structure of Cellulose related to its function?

A

– Cellulose molecules are held by Lotts of hydrogen bonds so gives strength to wall.

– Coiled SO compact

– Cellulose molecules arc made up of beta glucose and so form long straight, unbranched chains.
These cellulose molecular chains run parallel to each other and are crossed linked by hydrogen bonds which add collective strength. These molecules are grouped to form microfibrils which in turn are grouped to form fibres all of which provides yet more strength.

65
Q

What are 2 groups of lipid?

A

Triglycerides & Phospholipids (contribute to the flexibility of membranes and the transfer of lipid-soluble substances across them).

66
Q

What do lipids contain?

A

carbon, hydrogen and oxygen

67
Q

Are lipids insoluble or soluble in water?

A

insoluble

68
Q

What are the roles of lipids?

A
  • source of energy (when oxidised)
  • waterproofing (insoluble)
  • insulation (slow conductors of heat, help retain body heat when stored beneath the surface)
    -protection (stored around delicate organs e.g kidney)
69
Q

How are triglycerides formed?

A

By the condensation of 1 molecule of glycerol and 3 molecules of fatty acid.

70
Q

What bond is formed between glycerol and a fatty acid during a condensation reaction?

A

Ester bond

71
Q

What does hydrolysis of a triglyceride produce?

A

Glycerol and 3 fatty acids

72
Q

How can you recognise from diagrams if a fatty acid is saturated?

A

No carbon-carbon double bonds

73
Q

How can you recognise from diagrams if a fatty acid is unsaturated?

A

Is carbon-carbon double bonds

74
Q

What state are fats at room temp and what are oils at room temp?

A

Fats are solid at room temp, oils are liquid at room temp.

75
Q

The structure of TRIGLYCERIDES related to their properties :

A
  • Triglycerides have a high ratio of energy-storing carbon-hydrogen bonds to carbon atoms and are therefore an excellent source of energy.
  • Triglycerides have low mass to energy ratio, making them good
    storage molecules because much energy can be stored in a small volume. This is especially beneficial to animals as it reduces the mass they have to carry as they move around.
  • Being large, non-polar molecules, triglycerides are insoluble in water. As a result their storage does not affect osmosis in cells or the water potential of them.
  • As they have a high ratio of hydrogen to oxygen atoms, triglycerides release water when oxidised and therefore provide an important source of water, especially for organisms living in dry deserts.
76
Q

What makes phospholipids different from lipids?

A

One of the fatly acid molecules is replaced by a phosphate molecule.

Fatty acid molecules repel water (are hydrophobic), phosphate molecules attract water (are hydrophilic).

77
Q

Phospholipids are made of 2 parts :
Hydrophilic ‘head’ & Hydrophobic ‘tail’

A

Hydrophilic ‘head’ - interacts with water (is attracted to it) but not with fat.

Hydrophobic ‘tail’ - orients itself away from water but
mixes readily with fat.

78
Q

What does it means if molecules are said to be polar?

A

Molecules that have two ends (poles) that behave differently – This means that when these polar phospholipid molecules are placed in water they position themselves so that the hydrophilic heads are as close to the water as possible and the hydrophobic tails are as far away from the water as
possible.

79
Q

The structure of PHOSPHOLIPIDS related to their properties :

A

+ As phospholipids are polar molecules = in an aqueous environment, phospholipid molecules form a bilayer within the cell-surface membranes = hydrophobic barrier is formed between the inside and outside of the cell.

+ The hydrophilic phosphate ‘heads’ of phospholipid molecules help to hold at the surface of the cell-surface membrane.

+ The phospholipid structure allows them to form glycolipids by combining with carbohydrates within the cell-surface membrane. These glycolipids are important in cell recognition.

80
Q

What is the test for lipids?

A

The emulsion test -

  1. Take a completely dry and grease-free test 1ube.
  2. To 2 cm3 of the sample being tested, add 5 cm3 of ethanol.
  3. Shake the tube thoroughly to dissolve any lipid in the sample.
  4. Add 5 cm3 of water and shake gently.
  5. A cloudy-white colour indicates the presence of a lipid.
  6. As a control, repeat the procedures using water instead of the sample; the final solution should remain clear.

The cloudy colour is due to any lipid in the sample being finely dispersed in the water to form an emulsion. Light passing through this emulsion is refracted as it passes from oil droplets to water droplets,
making it appear cloudy.

81
Q

What does ATP stand for?

A

Adenosine Triphosphate

82
Q

What is a single molecule of ATP?

A

A nucleotide derivative and is formed from a molecule of ribose, a molecule of adenine and 3 phosphate groups.

83
Q

What is adenine?

A

A nitrogen-containing organic base

84
Q

What is ribose?

A

A pentose sugar that acts as the backbone to which the other parts are attached.

85
Q

What are the 3 phosphate groups a key to?

A

how ATP stores energy

86
Q

Why does the body need lots of ATP?

A

It needs lots of ATP for each hydrolysis reaction as only a small amount is made.

87
Q

Why do the bonds between these phosphate groups have a low activation energy?

A

Because they are unstable. The low activation energy means they are easily broken.

88
Q

What happens when ATP is hydrolysed?

A

When ATP is hydrolysed a considerable amount of energy is released. ATP is hydrolysed into ADP (Adenosine Diphosphate) and an inorganic phosphate group (Pi).

  • Releases small packets of energy - perfect for chemical reactions within cells –> don’t waste energy
89
Q

What enzymes catalyses the Hydrolysis of ATP?

A

ATP Hydrolase

90
Q

Is ATP hydrolysis a 1 step reaction?

A

Yes, meaning energy is released quickly.

91
Q

What can the inorganic phosphate which is released during the hydrolysis of ATP be used to?

A

Phosphorylate other compounds - making them more reactive.

92
Q

What enzyme catalyses the Resynthesis of ATP?

A

ATP Synthase - energy can be used to add an inorganic phosphate to ADP to re-form.
ATP - condensation reaction (water is removed).

93
Q

Is ATP the intermediate energy source of a cell?

A

YES because of the instability of its phosphate bonds.

94
Q

Can ATP be made?

A

ATP cannot be stored and so has to be continuously made within the mitochondria of cells that need it.

95
Q

WHEN IS ATP MADE?

A

ATP is made in respiration (mitochondria) to release energy.

&

ATP is made in photosynthesis (chloroplasts), is use din photosynthesis.

96
Q

Why can ATP not leave cells?

A
  • small enough to travel throughout the cell, to large to travel out the cell.
  • always there when the cell needs it.
  • if cell can not make it = can not get it from anywhere else = it will die.
97
Q

ATP is used in energy-requiring processes in cells. Name 5 :

A
  • metabolic processes
  • movement
  • active transport
  • secretion
  • activation of molecules
98
Q

What 2 atoms is water made from and how many?

A

2 atoms of hydrogen & 1 atom of oxygen

99
Q

Why is water a polar molecule?

A

Has both + & - poles

100
Q

How does water have hydrogen bonds?

A

Different poles attract, + pole of one water molecule will be attracted to the - pole of another water molecule.

The attraction force between these opposite charges is called a hydrogen bond.

Each bond is fairly weak —- together they form important forces which cause the water molecules to stick together – gives strength e.g cellulose — gives water its unusual properties.

101
Q

Water is a METABOLITE – takes part in chemical reactions

A

Water is used to break down many complex molecules by hydrolysis - addition of water to break bonds .

Water is produced during condensation reactions.

Enzymes, whose reactions take place in solution.

102
Q

Water as a SOLVENT – reactions can dissolve in it, therefore, collisions more likely e.g cytoplasm and tissue fluid

A

Water dissolves gasses e.g oxygen and carbon dioxide.

Wastes e.g ammonia and urea.

Inorganic ions and small hydrophilic molecules e.g ATP, monosaccharides and amino acids.

103
Q

COHESION (tendency of molecules to stick together) & SURFACE TENSION in Water

A

Cohesion between water molecules supports a column of water.

Supports the transpiration stream of water in plants.

104
Q

HIGH SPECIFIC HEAT CAPACITY

A

Buffers internal and external temperature change.
- makes aquatic environment a temperature stable one
- buffers organisms from sudden temperature change as mostly made from water
- enzymes don’t denature

105
Q

LARGE LATENT HEAT OF VAPORISATION

A

Relatively large amount of energy is needed for water to evaporate.
- provides a cooling affect (sweat, transpiration).

106
Q

As ice is solid, it means its less dense than water, so therefore, what does it do?

A

Floats – so aquatic environment underneath is maintained.

107
Q

Why is it good that water is transparent?

A

Aquatic plants can photosynthesise

108
Q

Why is it good that water is not easily compressed?

A

Provides support

109
Q

What does evaporation help organisms to do?

A

Helps them cool down and control their body temperature.

110
Q

Where are inorganic ions found?

A

Inorganic ions are found in organisms where they occur in solution in the cytoplasm of cells and in body fluids and as well as part of larger molecules. They may be in concentrations that range from very high to very low.

111
Q

Do inorganic ions contain carbon?

A

No

112
Q

Name 4 of the INORGANIC IONS?

A

HYDROGEN IONS
PHOSPHATE IONS
IRON IONS
SODIUM IONS

113
Q

What do hydrogen ions do?

A

Determine pH - pH is calculated based on the concentration of hydrogen ions in the environment.

More present = Lower pH and the more acidic the environment.

114
Q

What receptors do we have in our blood vessels which detect changes to the pH?

A

Chemo receptors

115
Q

What is a phosphate group?

A

When a phosphate group is attached to another molecule.

116
Q

What do DNA, RNA, ATP all contain?

A

Phosphate groups

117
Q

What do the bonds between phosphate groups store?

A

Energy in ATP

118
Q

What do the phosphate groups in DNA, RNA allow nucleotides to do?

A

Join up to form the poly nucleotides

119
Q

What is the function of haemoglobin?

A

A large protein which carries oxygen around the body in red blood cells.

120
Q

What does the iron bind to in haemoglobin?

A

Oxygen

121
Q

What is haemoglobin made from?

A

4 polypeptide chains and 4 heat groups - each bind to the oxygen

122
Q

Glucose and amino acids need help crossing …

A

… membranes

123
Q

A molecule of glucose or an amino acid can be transported into a cell (across the cell-surface membrane) along side sodium ions by …

A

… co-transport

124
Q

What are the monomers of proteins?

A

Amino acids.

125
Q

How many different amino acids are there?

A

20.

126
Q

What does a condensation reaction between two amino acids form?

A

Dipeptides.

127
Q

What does a condensation reaction between many amino acids form?

A

Polypeptides.

128
Q

What is the name of the bonds which form between amino acids?

A

Peptide bonds.

129
Q

What protein may contain one or more polypeptides?

A

A functional protein.

130
Q

What is the test for proteins?

A

The biuret test.

131
Q

How do you carry out the biuret test?

A

Add biuret solution to the test solution, shake well, observe colour change, if there is a colour change from blue to purple, protein is present.

132
Q

What has to be present for the biuret test to turn positive?

A

When amino acids are present.

133
Q

How many structural layers do proteins have?

A

4.

134
Q

What are the 4 structural layers proteins have?

A

Primary structure, Secondary structure, Tertiary structure, Quaternary structure.

135
Q

What is the PRIMARY structure and what bonds are present in the PRIMARY structure?

A

The sequence of amino acids in a polypeptide chain (the sequence determines its properties and shape), peptide bonds are present.

136
Q

What is the SECONDARY structure and what bonds are present in the SECONDARY structure?

A

Polypeptide chain does not remain flat and straight, hydrogen bonds form between the amino acids in the chain, this makes the chain either coil into alpha helix or fold into a beta pleated sheet.

137
Q

What is the TERTIARY structure and what bonds are present in the TERTIARY structure?

A

Due to the bending and twisting of the polypeptide chain, it is coiled and further folded into a compact structure, more bonds form including hydrogen and ionic bonds, disulfide bridges also form where two amino acids of cysteine come close together. All 3 of these bonds contribute to the maintenance of the tertiary structure.
For proteins made from one polypeptide chain, the tertiary structure forms its final structure.

138
Q

What is the QUATERNARY structure and what bonds are present in the QUATERNARY structure?

A

Proteins made of several different polypeptide chain held together by hydrogen, ionic and disulfide bridges. It is the way these polypeptide chains are assembled together.
A large and complex protein molecule e.g. haemoglobin.

139
Q

What are 4 functions of proteins?

A
  1. Enzymes - Spherical in shape due to the tight folding of the polypeptide chains. Soluble and often have roles in metabolism and others help to synthesise large molecules.
  2. Antibodies - Immune response. Made up of 2 tight polypeptide chains and 2 heavy polypeptide chains bonded together.
  3. Structural Proteins - Physically strong. Consists of long polypeptide chains lying parallel to each other with cross-links between them.
  4. Transport Proteins - e.g. channel proteins. Contain hydrophobic and hydrophilic amino acids, cause protein to fold up and form a channel.
140
Q

What are enzymes?

A

Enzymes are biological catalysts which speed up the rate of reaction by lowering the activation energy of a reaction.

141
Q

What is the activation energy?

A

The minimum amount of energy needed to be supplied to the chemicals before a reaction starts in order for it to start.

142
Q

Why does the “Lock & Key Theory” not give the full story?

A

It does not give the full story because the enzyme and substrate do have to fit together in the first place, but the enzyme substrate complex changes shape slightly to complete the fit.

It stated that the substrate fits into the enzyme in the same way a key fits into a lock.

143
Q

Why is the “Induced Fit” model more accurate?

A

It states that as the substrate binds to the active site of an enzyme, the active site slightly changes shape.

144
Q

What are 6 ways in which enzyme properties relate to their tertiary structure?

A
  1. Enzymes are very specific which means they only catalyse one reaction.This is because only one complementary substrate will fit into the active site.
  2. The enzymes active sites shape is determined by the enzymes tertiary structure (determined by primary structure).
  3. Different enzymes have a different tertiary structure meaning they have a different shaped active site?
  4. If an enzymes tertiary structure is altered, the shape of the active site will change. This means the substrate won’t fit and an enzyme-substrate complex won’t be formed. Therefore, the enzyme cannot carry out its function.
  5. The tertiary structure of an enzyme may be altered by a change in pH or temperature.
  6. The primary structure (amino acid sequence) of a protein is determined by a gene. If mutation occurs in that gene, it can change the tertiary structure of the enzyme produced.
145
Q

What are the 6 key factors which affect the rate of enzyme-controlled reactions?

A

Enzyme concentration, Substrate concentration, Concentration of competitive inhibitors, Concentration of non-competitive inhibitors, pH, Temperature.

146
Q

How does ENZYME CONCENTRATION effect the rate of enzyme-controlled reactions?

A

More enzyme molecules = more likely a substrate molecule is to collide with an active site and form an enzyme-substrate complex. ⬆️ concentration of the enzyme, ⬆️ the rate of reaction.

  • If substrate amount is limited, there comes a point where there’s more than enough enzyme molecules to deal with all the available substrate. This means adding more enzyme molecules, has no further effect.
147
Q

How does SUBSTRATE CONCENTRATION effect the rate of enzyme-controlled reactions?

A

More substrate molecules = faster rate of reaction as more collisions are likely between substrate and enzyme molecules, so more active sites used until “saturation”. As active sites are used up, increasing the substrate concentration has no further effect.

Substrate concentration ⬇️ with time during a reaction (unless more substrate added), so if no other variables changed, the rate will ⬇️ over time too. Makes initial rate of reaction the highest rate of reaction.

148
Q

How does pH effect the rate of enzyme-controlled reactions?

A

Above and below the optimum pH, the hydrogen and hydroxide ions found in acids and alkalis can mess up the ionic and hydrogen bonds that hold the enzymes tertiary structure in place = active site changes shape = enzyme is denatured.

149
Q

How does TEMPERATURE effect the rate of enzyme-controlled reactions?

A

More heat = more kinetic energy so molecules move faster and makes molecules vibrate more = make enzymes more likely to collide with the substrate molecules. The energy of these collisions also ⬆️, which means each collision is more likely to result in a reaction.
If the temperature gets too high, the reaction stops. This is because, if the temp goes above a certain level, the vibration breaks some of the bonds that hold the enzyme in shape = active site changes shape = enzyme and substrate no longer fit together = enzyme is denatured = no longer function as a catalyst.

150
Q

Enzymes are highly specific due to …

A

… their tertiary structure.

151
Q

How do enzymes lower the activation energy? (2 reasons why)

A

1) If 2 substrate molecules need to be joined, being attached to the enzyme holds them close together, reducing any repulsion between the molecules so they can bond more easily.

2) If the enzyme is catalysing a break-down reaction, fitting into the active site puts a strain on the bonds in the substrate, so the substrate molecule breaks up easier.

152
Q

What are COMPETITIVE INHIBITORS? + How does the CONCENTRATION OF COMPETITIVE INHIBITORS effect the rate of enzyme-controlled reactions?

A
  • inhibitor molecule has a similar (not same) shape as the substrate.
  • competes with the substrate molecules to bind to the active site.
  • they block the active site so no substrate molecules can fit in = less successful enzyme-substrate complexes being formed = no reaction takes place.

⬆️concentration of substrate = ⬆️ chance in getting to the active site before the inhibitor. So rate of reaction ⬆️.

⬆️concentration of inhibitor = take up nearly all of the active sites = ⬇️ substrate will get to active sites.

153
Q

What are NON-COMPETITIVE INHIBITORS? + How does the CONCENTRATION OF NON-COMPETITIVE INHIBITORS effect the rate of enzyme-controlled reactions?

A
  • non-competitive inhibitor molecules bind away from the active site (allosteric site).
  • active site changes shape.
  • don’t compete with the substrate molecules to bind the the active sites because they are a different shape.

⬆️substrate concentration = no difference to the rate of reaction - enzyme action will still be inhibited.

154
Q

Enzymes can be deactivated by molecules called …

A

… inhibitors.

155
Q

What do inhibitors do?

A

Reduce/stop a reaction.

Biology ALevel AQA 2023-2024-2025 (10 decks)

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