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Biology - Year 12 > BIOLOGICAL MOLECULES SECTION 1 (CHAPTER 1) > Flashcards

BIOLOGICAL MOLECULES SECTION 1 (CHAPTER 1) Flashcards

1
Q

What is a Molecule ?

A

Two or more atoms held together by chemical bonds

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2
Q

What is a Biological molecules

A

Molecules are produced inside living things (organisms)

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3
Q

What does Polarised mean?

A

A molecule, within an uneven distribution of charge

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4
Q

What can polar molecules form

A

Hydrogen bonds - the negative part of one molecule is attached to the positive part of another

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5
Q

Examples of biological molecules

A

Carbohydrates : Starch (stored in plants), cellulose (strengths cell walls in plants), glycogen (in animals) - energy source structure

Proteins : enzymes, haemoglobin, collagen - structural catalysing reaction

Nucleic acids: DNA, RNA - genetic material/production for storage + transfer

Lipids : Triglycerides, phospholipids - energy source , structural

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6
Q

What is a monomer and polymer? And examples ?

A

Monomer - the smallest units from which large molecules are made. E.g A-glucose Polymer - many molecules E.g Starch/glycogen

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7
Q

What is polymerisation

A

Monomers can be linked together to form long chains (polymer) during process called polymerisation

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8
Q

What are Macromolecules ?

A

Large polymers

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9
Q

CARBOHYDRATES - MONOSACCHARIDES

A
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10
Q

What are carbohydrates?

A

They are carbon molecules combined with water (hydrate). Can be large or small.

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11
Q

What are organic molecules ?

A

carbon - containing molecules

Each carbon atom will bond with other elements with 4 bonds

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12
Q

What is a monosaccharide?

A

A single monomer

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13
Q

What is a disaccharide ?

A

A pair of monosaccharides combine to make a disaccharide

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14
Q

What is a polysaccharide ?

A

Many monosaccharides together would make a polysaccharide

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15
Q

What are the 4 main monosaccharides?

A

1) Galactose
2) Glucose
3) Fructose
4) Ribose

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16
Q

What is glucose?

A

A hexose sugar (6 carbons) , sweet tasting monosaccharides
Two isomers:
A -glucose, B-glucose

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17
Q

What is a property of a monosaccharide ?

A
  • they are soluble in water
    Monosaccharides have a large number of OH groups :hydroxyl groups. Hydroxyl groups form hydrogen bonds with water molecules. And because of this, monosaccharides are soluble in water. Scientists call molecules like these hydrophilic.
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18
Q

Test for reducing sugars

A

1) Add 2cm^3 of food sample to the test tube
2) Add 2cm^3 of Benedict’s solution to the test tube
3) Heat the mixture in a gently boiling water bath for 5 minutes
( When heated in the presence of a reducing sugar e.g. glucose, the CU 2+ ions are reduced to Cu+ ions in the form of copper (1) oxide, which forms a brick red precipitate.
4) The colours of the precipitate indicates the relative concentration of reducing sugar.
5) Precipitant will turn bright red from blue , showing high concentration of reducing sugar

Brick red - high
Orange - medium
Green - low
Blue - zero

A clear blue colours is a negative result, but a non -reducing sugar may be present.

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19
Q

Test for Non - reducing sugars ?

A
  1. Do the test for reducing sugars (steps 1-3)
  2. If the colour indicates blue, a non reducing sugar is present.
  3. (Sucrose is a non-reducing sugar and can be hydrolysed into glucose + fructose)
    Add dilute hydrochloric acid to the test tube containing sucrose
  4. The solution must be boiled and then neutralised with sodium hydrogen carbonate (and add it to the test tube containing sucrose +dilute hydrochloric acid) before the Benedict’s test can be performed
  5. Then, add 2cm^3 of Benedict’s solution to the test tube and heat the mixture in a gently boiling water bath for 5 minutes
  6. The sample will change colour when heated, indicating that it now contains reducing sugar (From blue to brick-red shows reducing sugar concentrating
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20
Q

Need to know how to draw the two isomers

A
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21
Q

What are the 3 main disaccharides ?

A
  1. Maltose
  2. Sucrose
  3. Lactose
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22
Q

What is a disaccharide?

A

A pair of monosaccharides can combine to make a disaccharide

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23
Q

How is maltose formed ?

A

Glucose + glucose =/ forms maltose

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24
Q

How is sucrose formed ?

A

Glucose + fructose =/forms sucrose

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25
Q

How is lactose formed ?

A

Glucose + galactose =/forms lactose

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26
Q

What is a condensation reaction ?

A

When the monosaccharides join, a molecule of water is removed and the reaction is therefore called a condensation reaction

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27
Q

What bond is formed in a condensation reaction ?

A

A glycosidic bond ( a covalent bond formed between two monosaccharides)

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28
Q

What is the chemical formula of maltose ?

A

C12H22O11 (glucose + glucose = maltose. And the chemical formula for glucose is C6H12O6).
Maltose is a condensation reaction, so water (H20) is removed, so there are less H and O elements, therefore there are 22H not 24H and it is O11, not O12 in C12H22O11.

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29
Q

What is a hydrolysis reaction ?

A

Water is added to a disaccharide , which breaks the glycosidic bond. This releases constituent monosaccharides. This addition of water to cause breakdown is called hydrolysis

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30
Q

What is the word equation for the hydrolysis of lactose ?

A

Lactose + water ~~~> glucose + galactose

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31
Q

What are polysaccharides?

A

They are polymers, formed by combining together many monosaccharide molecules.
(The monosaccharides are joined by glycosidic bonds that were formed by condensation reactions)

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32
Q

Other polysaccharide key points:

A
  • are very large molecules, so are insoluble ~~~> this feature makes them good 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 plants cells
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33
Q

What is the test for starch?

A
  1. Place 2cm^3 of the sample being tested into a test tube
  2. Add two drops of iodine solution and shake/stir
  3. The presence of starch is indicated by a blue -black coloration
    (Colour changes from yellow to blue-black)
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34
Q

What does the colour change to in the test for starch if starch is present ?

A

From yellow to blue-black

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35
Q

STARCH, GLYCOGEN, CELLULOSE (Polysaccharides)

A
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36
Q

Starch general points:

A
  • Main role of starch is energy storage
  • found in plants
    -is an energy source in most animal diets
  • made up of chains of alpha glucose monosaccharides linked by glycosidic bonds that are formed by condensation reactions
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37
Q

Structure of starch molecule:

A

-it is insoluble, doesn’t affect water potential, so water is not drawn into the cells by osmosis
- being large and insoluble,does not diffuse out of cells
- it is compact, so a lot of it can be stored in a small place
- when starch is hydrolysed, it forms
a-glucose, which is both easily transported and readily used in respiration
- the branched 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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38
Q

Types of starch :
Unbranched - Amylose

A

Monomer: alpha glucose
Found in : plants
Advantage of coiling : The unbranched chain is wound into tight coils that make the molecule compact
(The OH groups are pointing inwards + these form hydrogen bonds)

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39
Q

Types of starch:
Branched - Amylopectin

A

Monomer : alpha-glucose
Found in : plants
Advantage of branching : it has many ends which can be acted on by enzymes simultaneously, of which glucose molecules are released rapidly

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40
Q

Glycogen key points:

A

Monomer : alpha glucose
Found in : animals and bacteria, but never plants
- in animals, it is stored as small granules mainly in the liver and muscles
-Fat is the main storage molecule in animals

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41
Q

Why is glycogen used for storage ?

A
  • insoluble, so does not affect osmosis
    -it does not diffuse out of cells
    -can be compact so a lot can be stored in a small space
  • highly branched so it can acted on simultaneously by enzymes for a quick release of glucose (important for respiration)
  • Very similar structure to starch but has shorter chains with more branches
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42
Q

Cellulose key points:

A

Monomer : beta glucose
Found in : plants
Function : strengthens the cell
Structure: rather than coiling like starch, cellulose has straight unbranched chains that run parallel to one another allowing hydrogen bonds to form cross- linkages between them.

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43
Q

How is cellulose adapted to its function!

A
  • Each hydrogen bond is weak, but in large numbers, they are collectively strong. This makes it a great structural material
  • cellulose molecules group together to form micro fibrils, which in turn are arranged in parallel groups called fibrils
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44
Q

LIPIDS

A
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45
Q

What are some characteristics of lipids?

A
  • insoluble in water
  • soluble in organic solvents such as alcohols and acetone
  • Main groups of lipids are triglycerides (fats and oils) and phospholipids
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46
Q

What are the main groups of lipids?

A

-Triglycerides (fats and oils) and phospholipids

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47
Q

What is the difference between fats and oils?

A

Fats are solid at room temperature (in animals)
Oils are liquid at room temperature (in plants)

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48
Q

What are the roles of lipids?

A
  • In the cell membranes
  • source of energy
  • waterproofing
  • insulation
  • protection
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49
Q

Why is ‘in the cell membranes’ a role in lipids ?

A

Phospholipids contribute to the flexibility of membranes ( cholesterol regulates the fluidity of the cell membrane ) and transfer of lipid - soluble substances across them

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50
Q

Why is ‘source of energy’ a role in lipids ?

A

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

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51
Q

Why is ‘waterproofing’ a role in lipids?

A
  • lipids are insoluble on water, therefore useful as water proofing
  • both plants +insects have waxy, lipid cuticles that conserve water, while mammals produce an oily secretion from the sebaceous glands in the skin
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52
Q

Why is ‘insulation ‘ are role in lipids ?

A
  • fats are slow conductors of heat and when stored beneath the body surface help to retain body heat
  • They all act as electrical insulator in the myelin sheath around nerve cells
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53
Q

Why is ‘protection’ a role in lipids ?

A
  • fat is often stored around delicate organs, like the kidney
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54
Q

What is a triglyceride?

A
  • three (tri) fatty acids combined with glycerol (glyceride)
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55
Q

What is the formation of a triglyceride?

A

Each of the three fatty acid forms an ester bond with one glycerol in a condensation reaction. There is a removal of three molecules of water.
Hydrolysis of a triglyceride therefore produces glycerol and three fatty acids

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56
Q

What is a saturated fatty acid ?

A

No double bonds between carbon atoms

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57
Q

What is an unsaturated/mono-unsaturated fatty acid ?

A

A single double bond between carbon atoms
(Double bonds cause the molecule to bend. They therefore cannot pack together so closely making them liquid at room temperature)

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58
Q

What is a polyunsaturated fatty acid ?

A

More than one double bond between carbon atoms

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59
Q

The structure of triglycerides related to their properties ?

A
  • they have a high ratio of energy-storing carbon-hydrogen bonds to carbon atoms and are therefore an excellent source of energy
  • they have a low mass to energy ratio, so they can store lots of energy in a small volume (benefits animals as it reduces the mass they have to carry as they move around)
  • non-polar molecules, so insoluble in water, so their storage does not affect water potential /osmosis in cells
  • they have a high ratio of hydrogen to oxygen atoms, so they release water when oxidised. This is why animals in desserts can use fat as a source of water
60
Q

What are phospholipids?

A
  • similar to lipids except they have one less fatty acid, which is replaced with a phosphate molecule
61
Q

What is the structure of phospholipids? (What are the two parts it is made up of - head +tail)

A

Whereas fatty acid molecules repel water(hydrophobic), phosphate molecules attract water (hydrophilic). So phospholipid made up of two parts:

  1. A hydrophilic ‘head’, which interacts with water (attracted to it) but not with fat
  2. A hydrophobic ‘tail’, which orients itself away from water but mixes readily with fat
62
Q

The structure of phospholipids related to their properties?

A
  • they are polar molecules (hydrophilic head, hydrophobic tail) , means that in an aqueous environment, phospholipid molecules form a bilayer within cell surface membranes - hydrophobic barrier formed
  • 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. (Glycolipids important in cell recognition)
63
Q

What is the test for lipids?

A
  1. Take a completely dry and grease -free test tube
  2. To 2cm^3 of the sample being tested, add 5cm^3 of ethanol
  3. Shake the tube thoroughly to dissolve any lipid in the sample
  4. Add 5cm^3 of water and shake gently
  5. A milky - white emulsion 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
64
Q

What colour shows the presence of lipid in the emulsion test for lipids?

A

Milky-white colour

65
Q

PROTEINS

A
66
Q

What are the two types of amino acids?

A

Essential:are obtained from protein -rich foods

Non-essential - they are synthesised naturally in your body

67
Q

What are the 4 types of proteins?

A
  1. Enzymes
  2. Antibodies
  3. Transport proteins - located on the surface of cell membranes
  4. Structural proteins
68
Q

What is the structure of an amino acid?

A

R
R
|
H2N —————- C —————— COOH
|
H

Amine group (H2N) - a basic group from which the amino part of the name amino acid is derived

Carboxyl group (COOH) - an acidic group which gives the amino acid the acid part of its name

Hydrogen atom (H)

R - is the R group. It is a variety of different chemical groups. Each amino acid has a different R group. These 20 naturally occurring amino acids differ only in their R (side) group

69
Q

What is a peptide bond ?

A

A chemical bond that is formed by joining the carboxyl group of one amino acid to the amino group of another

70
Q

What type of reaction breaks down peptide bonds?

A

Hydrolysis reaction

71
Q

How is a dipeptide formed ?

A

Two amino acid monomers bond to form a dipeptide bond via a peptide bond.

72
Q

What reaction forms a peptide bond ?

A

A condensation reaction - the removal of a water molecule.

(The water is made by combining an OH from the carboxyl group of one amino acid with an H from the amino group of another amino acid.
The two amino acids then become linked by a new peptide bond between the carbon atom of one amino acid and the nitrogen atom of the other)

73
Q

What is polymerisation, and what is formed during the process?

A

Polymerisation - joining of many amino acids through condensation reactions

A polypeptide is formed (the resulting chain of many hundreds of amino acids)

74
Q

What is the primary structure of proteins?

A
  • sequence of amino acids joined by peptide bonds
  • bonds created via condensation reactions between the carboxyl and amino groups of adjacent amino acids
  • In the polypeptide chain, the sequence of amino acids is determined by the sequence of bases in DNA
75
Q

What is the secondary structure of proteins?

A

-Hydrogen bonds form between the amino acids in the chain, and the polypeptide is no longer a straight chain. It starts to change the shape of the polypeptide as the chain folds.
- Alpha helices and beta sheets are created by the folds

76
Q

What is the tertiary structure of proteins?

A

-The coiled or folded chain that we saw in the secondary structure is then folded and coiled even further
- For proteins that are formed from just one polypeptide chain, this can be the final 3D protein structure. (e.g. enzymes)
- In addition to hydrogen bonds, we start to see:
Ionic bonds
Disulfide bonds
Hydrogen bonds

77
Q

What are ionic bonds?

A
  • formed between any carboxyl and amino groups that are not involved in forming peptide bonds.
  • They are weaker than disulfide bond and are easily broken by changes in pH

[Attractions between negative and positive charges on different parts of the molecule ]

78
Q

What are disulfide bonds?

A
  • these bonds form when two cysteine amino acids come together. Cysteine contains a sulfur atom which will bind to the sulfur atom of the other cysteine molecule

[Disulfide bridges - are fairly strong and therefore not easily broken ]

79
Q

What is the quaternary structure of proteins?

A
  • This is the final 3D structure for proteins made of more than one polypeptide chain, held together by hydrogen bonds
  • The chains come together and are folded to perform their special function.
  • E.g insulin, haemoglobin, collagen
80
Q

What is the test for proteins?

A
  • place a sample of the solution to be tested in a test tube and add an equal volume of sodium hydroxide solution at room temperature (as the test solution needs to be alkaline)
  • Add a few drops of very dilute copper (II) sulfate solution (Biuret solution ) and mix gently
  • A purple coloration indicates the presence of peptide bonds and hence a protein. If no protein is present, the solution remains blue
81
Q

What colour shows proteins are present ?

A

Changes from blue to purple

82
Q

ENZYME ACTION

A
83
Q

What are enzymes?

A

They are biological catalysts of metabolic reactions

84
Q

What is activation energy?

A

The minimum amount of energy needed to activate the reaction (as many reactions require an initial amount of energy to start)

85
Q

How can enzymes allow reactions to take place at lower temperatures than normal ?

A

Enzymes work by lowering the activation energy level. [In this way enzymes allow reactions to take place at a lower temperature than normal. ]
This enables some metabolic processes to occur rapidly at the human body temperature of 37°C

86
Q

How does the active site have a specific shape?

A

Due to the tertiary structure of the protein

87
Q

What is the active site?

A

-A specific region of the enzyme is functional - active site
-it is made up of relatively small number of amino acids
- It forms a small depression within the much larger enzyme molecule

88
Q

What is the substrate , and what does it form?

A

The molecule on which the enzyme acts. This fits neatly into this depression and forms an enzyme-substrate complex.

[The substrate molecule is held within the active site by bonds that temporarily form between certain amino acids of the active site and groups on the substrate molecule]

89
Q

What is the difference between the lock+key model and the induced fit model?

A

-The lock and key theory suggested that the enzyme shape is a rigid structure
- The induced fit model shows enzyme is flexible so not a rigid structure

90
Q

What is the lock and key hypothesis ?

A
  1. The enzyme+ substrate enters the active site
  2. The substrate binds to the active site, and the active site is complementary to the substrate, which suggests the enzyme has a rigid structure [enzyme/substrate complex]
  3. Enzyme/product complex
  4. Enzyme + product leaving the active site
91
Q

What is the limitation of the lock and key model ?

A
  • it is considered to be a rigid structure. However, scientists had observed that other molecules could bind to enzymes at sites other than the active site, so structure was not rigid but flexible.
92
Q

What does the induced fit model show?

A
  • the active site forms as the enzyme and substrate interact.
  • A change in the environment of the enzyme leads to a change in the enzyme that forms the functional active site
93
Q

What does the induced model show (detailed version ) ?

A
  • The enzyme is flexible and can mould itself around the substrate (like glove moulds itself to the shape of a hand)
  • The enzyme has a certain general shape, and alters in the presence of the substrate
    -As it changes it’s shape,the enzyme puts a strain on the substrate molecule
  • The strain distorts a particular bond/bonds in the substrate and consequently lowers the activation energy needed to break the bond
  • Any change in an enzyme’s environment is likely to change its shape ~~~> functional active site
94
Q

Describe the induced-fit model of enzyme action .

A

Active site is not complementary to substrate.
Shape of active site changes as substrate binds / enzyme- substrate complexes are formed

95
Q

Measuring the rate of enzyme activity

A
96
Q

The rate of enzyme activity can be measured in what two different ways?

A
  1. By measuring the release/presence of a product over time
  2. By measuring the disappearance of a substrate over time
97
Q

What is the explanation for graphs that show the rate of enzyme activity?

A
  • At first there is a lot of substrate but no product
  • All enzyme active sites are filled at any given moment and the substrate is rapidly broken down into its products
  • The amount of substrate decreases as it is broken down, resulting in an increase in the amount of product
    -Becomes more difficult for the substrate molecules to come into contact with the enzyme molecules due to fewer substrate molecules
  • so takes longer for substrate molecules to be broken down by the enzyme , its rate of disappearance slows
  • The rate of reaction continues to slow until there is so little substrate that any further decrease in its concentration cannot be measured
  • The graphs flatten out because all the substrate has been used up ( so no new product can be produced)
98
Q

Why does the graph flatten out in a graph that shows enzyme activity ?

A

Because all the substrate has been used up (no new product can be produced)

99
Q

How do you measure the rate of change?

A

Gradient = change in y/ change in x

100
Q

The effect of temperature on enzyme action

A
101
Q

What happens to the molecules when there is a rise in temperature?

A

A rise in temperature increases the kinetic energy of molecules. As a result, the molecules move around more rapidly and collide with each other more often.

102
Q

What does a rise on a graph show on the effect of temperature on enzyme action

A

The increase in kinetic energy

103
Q

What happens to the enzymes if temperatures rise too high?

A

-causes the hydrogen and other bonds in the enzyme, including its active site to change shape.
-At first, the substrate fits less easily into this changed active site, slowing the rate of reaction

104
Q

Why does the graph ( the graph about the effect of temperature on enzyme activity )show a falling curve ?

A

The shape of the enzyme changes too much (it is so disrupted) and is no longer complementary to the substrate. This is called denaturation.
[ denaturation is a permanent change and once it has occurred, the enzyme does not function again]

105
Q

What are reasons why our body temperature may be evolved to be lower ?

A
  • other proteins start to denature at 40°C
    -Need to produce more energy to heat ourselves up by another 3°C ~~> consuming more food
  • If you become ill, your temperature increases so there is a buffer to allow for this
  • Although higher body temperatures would increase the metabolic rate slightly, the advantages are offset by the additional energy (food) that would be needed to maintain the higher temperature
106
Q

Effect of pH on enzyme action

A
107
Q

What is the pH of a solution ?

A

A measure of the concentration of H+ ions

108
Q

How can we calculate the pH of a solution ?

A

pH= -log10 [H+]

109
Q

What happens to the H+ ions when we decrease the pH by 1?

A

H+ ions increase 10x

110
Q

What happens to the OH- ions when increasing the pH by 1?

A

The OH- ions increase 10x

111
Q

How can we control the pH?

A

Use a buffer, a buffer withstands changes to pH

112
Q

How does the pH affect how an enzyme works?

A
  • A change in pH alters the charges on the amino acids that make up the active site of an enzyme. As a result, the substrate can no longer become attached to the active site and so the enzyme-substrate complex cannot be found
  • Depending on how significant the change in pH is,it may cause the bonds maintaining the enzyme’s tertiary structure to break. The active site therefore changes shape
113
Q

What is the arrangement of the active site partly determined by ?

A

The hydrogen and ionic bonds between -NH2 and -COOH groups of the polypeptides that make up the enzyme.
[The change in H+ ions affects this bonding, causing the active site to change shape]

114
Q

What does it mean by the pH fluctuations inside organisms are usually small?

A

They are far more likely to reduce an enzyme’s activity than to denature it

115
Q

Effect of enzyme concentration on the rate of reaction

A
116
Q

What happens if you have a higher concentration of enzymes in your closed system ?

A

You will achieve a higher likelihood of collision and the formation of enzyme- substrate complexes.
[so, you only need a small concentration of enzymes for the reaction to happen.
One enzyme can act upon millions of substrate molecules]

117
Q

What does 1:1 ratio of enzyme to substrate mean ?

A

Adding more enzymes will not increase activity

118
Q

What does it mean when the substrate is limiting (there is no sufficient to supply all the enzyme’s active sites at one time) ?

A

An increase in enzyme concentration will have no effect on the rate of reaction. The rate of reaction will therefore stabilise at a constant level, meaning the graph will level off.

119
Q

[The graph has enzyme concentration on the x axis, and rate of reaction on the y-axis. ]

What does the graph show when the rate of reaction increases as the enzyme concentration increases ?

(Look at kerboodle page 29 for graph explaining what happens at each stage)

A

Low enzyme concentration:
-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.

120
Q

[The graph has enzyme concentration on the x axis, and rate of reaction on the y-axis. ]

What does the graph show when the rate of reaction increases as the enzyme concentration increases, it is at its highest peak ?

(Look at kerboodle page 29 for graph explaining what happens at each stage)

A

Intermediate enzyme concentration :
- 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 sites are filled

121
Q

[The graph has enzyme concentration on the x axis, and rate of reaction on the y-axis. ]

What does the graph show when the rate of reaction plateaus as the concentration increases ?

(Look at kerboodle page 29 for graph explaining what happens at each stage)

A

High enzyme concentration :
- the addition of further enzyme molecules has no effect as there are already enough active sites to accommodate all the available substrate molecules.
- There is no increase in the rate of reaction

122
Q

Effects of substrate concentration on the rate of enzyme action

A
123
Q

What happens to the rate of reaction if the concentration of enzyme is fixed and substrate concentration is slowly increased ?

A

The rate of reaction increases in proportion to the concentration of substrate

124
Q

Why does the rate of reaction increase in proportion to the concentration of substrate ?

A

This is because at low substrate concentrations, the enzyme molecules have only a limited number of substrate molecules to collide with, and therefore the active sites of the enzymes are not working to full capacity

125
Q

What happens when more substrate is added?

A

The active sites gradually become filled, until the point where all of them are working as fast as they can

126
Q

What happens when you add the addition of more substrate when the rate of reaction is at its maximum ?

A

Addition of more substrate will have no effect on the rate of reaction (there aren’t enough active sites available).
- When there is an excess of substrate, the rate of reaction levels off

127
Q

[The graph has substrate concentration on the x axis, and rate of reaction on the y-axis. ]

What does the graph show when the rate of reaction increases as the enzyme concentration increases ?

(Look at kerboodle page 30 for graph explaining what happens at each stage)

A

Low substrate concentration :
- 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

128
Q

[The graph has substrate concentration on the x axis, and rate of reaction on the y-axis. ]

What does the graph show when the rate of reaction increases as the enzyme concentration increases, it is at its highest peak ?

(Look at kerboodle page 30 for graph explaining what happens at each stage)

A

Intermediate substrate concentration:
- With twice as many substrate molecules avail, 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

129
Q

[The graph has substrate concentration on the x axis, and rate of reaction on the y-axis. ]

What does the graph show when the rate of reaction plateaus as the concentration increases ?

(Look at kerboodle page 30 for graph explaining what happens at each stage)

A

High substrate concentration :
-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

130
Q

What is the difference between lactose and lactase ?

A

Lactose = a type of sugar
Lactase = an enzyme

Lactose is a type of sugar found in milk and milk products.
Our bodies produce an enzyme called lactase, which helps us digest lactose properly.

131
Q

ENZYME INHIBITION

A
132
Q

What is an inhibitor?

A

A molecule which reduces the rate of an enzyme controlled reaction

133
Q

What is a competitive inhibitor ?

A

An inhibitor which binds to the active site of the enzyme, not the substrate. ( So substrate molecule unable to occupy the active site)

134
Q

What is a non-competitive inhibitor?

A

An inhibitor which binds to the enzyme at another site (allosteric site ) other than the active site

135
Q

What is an example of a competitive inhibitor ?

A

Penicillin

136
Q

What is an example of a non-competitive inhibitor ?

A

Mercury

137
Q

Competitive inhibitors

A
138
Q

What must the substrate and the inhibitor have so they can occupy the active site?

A

They must have a very similar structure

139
Q

What happens when the inhibitor accommodates the active site?

A

Less enzyme-substrate complexes can be formed, slowing the rate of enzymatic activity

140
Q

What happens to the effect of the inhibitor if the substrate concentration is increased ?

A

The effect of the inhibitor is reduced

141
Q

How can the effect of competitive inhibition be remedied ?

A

By adding extra substrate to increase the chance of enzyme-substrate collisions and therefore complexes

142
Q

Non-competitive inhibitors

A
143
Q

What happens to the shape of the enzyme and its active site when non competitive inhibitors attach to the enzyme ?

A

The inhibitor alters the shape of the enzyme and thus its active site in such a way that substrate molecules can no longer occupy it, and so the enzyme cannot function.

144
Q

Why does an increase in substrate concentration does not decrease the effect of the inhibitor ?

A

The substrate and the inhibitor are not competing at the same site

145
Q

What does adding more substrate do when the active site is no longer complementary to the substrate?

A

It will make no difference

146
Q

Describe how the scientist would have produced the calibration curve and used it to obtain the results in the graph ?

A
  • make maltose solutions of known/different concentrations (and carry out quantitive Benedict’s test on each)
  • use colorimeter to measure colour value of each solution and plot calibration curve
  • find concentration of sample from calibration curve

Biology - Year 12 (10 decks)

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