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Biology Module 2 > Enzymes > Flashcards

Enzymes Flashcards

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1
Q

What are enzymes

A

they are biological catalysts because they speed up metabolic reactions in living organisms, there actions effect structure and functions in cells

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2
Q

What is the turnover number

A

the number of reactions that an enzymes molecule can catalyse per second

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3
Q

How do enzymes work

A
  • they are catalysts so speed up the rate of reaction without themselves being used up in the first place so they can be used again
  • a small amount of catalyst can be used to catalyse teh conversion of a large number of substrate molecules into product molecules
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4
Q

why are enzymes better than normal chemical catalysts

A
  • they are more specific than chemical catalysts
  • do not produce unwanted products and do not make mistakes
  • cells in which they are made in regulate their production and activity to fit the needs of the cell or organism at that time
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5
Q

for some enzymes to catalyse reactions they may need help from….

A

cofactors

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6
Q

what would prevent the enzyme from working

A
  • if the instruction which code for the gene has a mutation this could alter the sequence of amino acids in the protein which will alter the enzymes tertiary structure and prevent it from functioning
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7
Q

What happens when an enzyme that catalyses a metabolic reaction is deficient

A
  • a metabolic disorder results
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8
Q

What do enzymes also catalyse the reaction off

A
  • the formation of the organisms structural components such as collagen in bone, cartilage, joints, connective tissue, if the enzyme does not function while this happens then it can be harmful and cause diseases such as stone man syndrome
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9
Q

What is the active site

A

The indented area on the surface of an enzyme molecule with a shape that is complementary to the shape of the substrate molecule

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10
Q

Describe the active site

A
  • made from the tertiary structure
  • the shape is complementary to the shape of the substrate molecule therefore its shape is very important
  • therefore each type of enzyme is specific in its function as it can only catalyse reactions of substrate molecules which fit into the active site and produce product molecules
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11
Q

What changes the active site of an enzyme

A
  • temperature
  • pH
    These both effects the bonds that hold proteins in there tertiary structure
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12
Q

What is an intracellular enzyme

A

inside the cell

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13
Q

What is an extracellular enzyme

A

outside the cell

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14
Q

Describe a metabolic pathway (Intracellular enzymes)

A
  • each metabolic pathway in a living cell is one of a series of consecutive reactions and every step is catalysed by an enzyme
  • various reactants and intermediates act as substrates for the enzyme
  • reactants, intermediates and products act as metabolites
  • e.g. respiration and photosynthesis
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15
Q

Describe anabolic and catabolic pathways (metabolic pathways for intracellular enzymes)

A
  • in catabolic pathways - metabolites are broken down to smaller molecules and release energy
  • in anabolic pathways - energy is used to synthesis larger molecules from smaller ones
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16
Q

Describe the catalase example for intracellular enzymes

A
  • catalase protects cells from damage by reactive oxygen by breaking down hydrogen peroxide to form water and oxygen
  • catalase consists of four polypeptide chains and contains a haem group with iron, it is the fastest acting enzyme and has the largest turnover
  • found in eukaryotic cells in vesicles called peroxisomes
  • when white blood cells ingest pathogens catalase is used to help kill the invading microbe
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17
Q

What type of enzyme is catalase

A

Intracellular

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18
Q

What type of enzyme is amylase, trypsin, and mucor

A

Extracellular

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19
Q

Describe the Mucor example for extracellular enzymes

A
  • fungi such as the bread mucor release hydrolytic enzymes from their hyphae, the enzymes digest carbohydrates, proteins and lipids in the bread and the products of digestion - glucose, amino acids, glycerol and fatty acids are absorbed into the fungal hyphae for respiration and growth
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20
Q

Describe the amylase example for extracellular enzymes

A
  • amylase is produced in the salivary glands, it acts in the mouth and digests the polysaccharide starch to the disaccharide maltose, it is also made in the pancreas and acts to catalyse the same reaction in the lumen of the small intestine
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21
Q

Describe the typsin example for extracellular enzymes

A
  • made in the pancreas, and acts in the lumen of the small intestine to digest proteins into smaller peptides by hydrolysing peptide bonds
  • Optimum pH between 7.5 - 8.5
22
Q

What are cofactors

A

these are substances that have to be present to ensure that an enzyme catalysed reaction takes place at the appropriate rate

  • prosthetic groups are part of the enzyme structure
  • mineral ion co-factors and organic coenzymes form temporary associations with the enzyme
23
Q

What type of enzymes-catalysed reactions especially need help from cofactors

A
  • oxidation-reduction reactions
24
Q

What is a prosthetic group

A
  • a cofactor that is permanently bound by covalent bonds to an enzyme molecule
25
Q

Give an example of an prosthetic group catalysed reaction

A
  • carbonic anhydrase which contains a zinc ion permanently bound to its active site
  • found in the erythrocytes and catalyses the intercoversion of carbon dioxide to water and carbonic acid, this then breaks down to a hydrogen ion and hydrogencarbonate ions
  • important as it enables carbon dioxide to be carried from the respiring tissues to the lungs
26
Q

During an enzyme-catalysed reaction the enzyme and substrate molecules temporarily bind together to form

A

an enzyme-substrate complex

27
Q

What happens when certain ions that temporarily bind to the substrate or enzyme molecule

A
  • this may ease the formation of enzyme-substrate complexes and increase the rate of the enzyme catalysed reaction
28
Q

What do cofactors do when they bind to an enzyme

A
  • some act as co-substrates, they and the substrate together form the correct shape to bind to the active site of the enzyme
  • some change the shape of distribution on the surface of the substrate molecule or on the surface of the enzymes active site to make the temporary bonds in the enzyme-substrate complex easier to form
29
Q

What are coenzymes

A

these are small organic non-protein molecules that bind temporarily to the active site of enzyme molecules either before or at the same time that the substrate binds
- they are chemically changed during the reaction and need to be recycled to there original state sometimes by a different enzyme

30
Q

What coenzymes are derived from what vitamins

A 
B12 - cobalamin coenzymes 
Folic acid - tetrahydrofolate 
Nicotinamide B3 - NAD, NADP
Pantothenate B6 - Coenzyme A
Thiamine B1 - Thiamine Pyrophosphate
31
Q

What deficiency disease is caused by lack of B12

A
  • lack of B12 means there is lack of coenzyme cobalamin coenzymes
  • pernicious anaemia this is progressive and fatal anaemia
32
Q

What deficiency disease is caused by lack of Folic acid

A
  • lack of folic acid means there is a lack of tetrahydrofolate
  • megablastic anaemia - these are larger irregularly shaped erythrocytes
33
Q

What deficiency disease is caused by lack of Nicotinamide B3

A
  • Lack of B3 means lack of NAD and NADP

- pellagra - diarrhoea, dermatitis and dementia

34
Q

What deficiency disease is caused by lack of Pantothenate B6

A
  • Lack of B6 means lack of coenzyme A

- elevated blood-plasma triglyceride levels

35
Q

What deficiency disease is caused by lack of Thiamine B1

A
  • Lack of B1, this means lack of thiamine pyrophosphate

- Beriberi - mental confusion, irregular heart beat, muscular weakness, paralysis and heart failure

36
Q

What is an enzyme-product complex

A

enzyme molecules with product molecules in its active site, the two are joined temporarily by non-covalent forces

37
Q

What is an enzyme-substrate complex

A
  • enzyme molecules with substrate molecules in its active site, the two are joined temporarily by non-covalent forces
38
Q

Describe the lock and key hypothesis

A
  1. the enzymes tertiary structure of the enzymes active site gives it a shape that is complementary to that of the substrate molecule that it needs to catalyse the reaction for
  2. the substrate molecule fits into the enzymes active site and temporary hydrogen bonds hold the two together forming an enzyme-substrate complex (ES complex)
  3. the substrate molecule is broken into smaller product molecules that leave the active site
    or. ..
  4. the substrate molecules fit into the active site forming a enzyme - substrate complex
  5. bond forms between the substrate molecules
  6. the larger product molecule leaves the active site
39
Q

Describe in depth the lock and key hypothesis

A
  1. the substrate molecules and enzyme molecules both have kinetic energy and are constantly moving randomly
  2. if a substrate molecule successfully collides with an enzyme molecule then an enzyme substrate complex forms this is because the substrate molecule fits into the complementary shaped active site on the enzyme molecule
  3. the substrate molecules are either broken down or built up into the product molecule and form an enzyme -product complex while still in the active site
  4. product molecules now leave the active site
  5. the enzyme is now able to form another enzyme-substrate complex
  6. a small number of enzyme molecules can therefore convert a large number of substrate molecules into product molecules
40
Q

Describe the induced fit hypothesis

A
  1. when the substrate molecules fit into the enzymes active site the active site changes shape to mould around the substrate molecule
  2. the active site still has a shape which is complementary to the substrate molecule but while binding the changes of the side chains of the amino acid give a more precise conformation that fits the substrate molecule exactly
  3. binds more effectively
  4. enzyme substrate complex is formed and non-covalent forces such as hydrogen bonds, ionic attractions, hydrophobic interactions bund the substrate to the enzymes active site
  5. substrate molecules have been converted to the product molecules and these are still in the active site they form an enzyme-product complex
  6. the product molecules have a slightly different shape from the substrate molecule so they detach from the active site
  7. the enzyme is now free to catalyse another reaction with another substrate molecule of the same type
41
Q

How do the enzymes lower the activation energy

A
  • enzymes have an active site specific to only the substrate molecules they bring the substrate molecules close enough together to react without the need for excessive heat therefore they lower the activation energy as the molecules do not need to overcome the activation energy as they need less energy to do so
42
Q

What happens when a substance is heated

A
  • the extra energy in the form of heat causes the molecules to move faster
  • this increases the rate of collisions between molecules
  • it increases the force with which they collide as they are moving faster
43
Q

What happens when the reactant mixture is heated

A

both types of molecules gain kinetic energy and move faster, this increases the rate and number per seconds of successful collisions, therefore the rate of formation of ES complexes increases and the rate of reaction increases this increases the number of enzyme-product complexes per second up to a point
at a particular temperature called the enzymes optimum temperature the rate of reaction is at its maximum

44
Q

What happens when the temperature increases above the optimum

A

as the temperature increases this may break some of the weak bonds such as the hydrogen and ionic bonds that hold the tertiary structure of the enzymes together
as the molecules active site changes the substrate molecules do not fit into it therefore the reaction cannot be catalysed and the rate of reaction decreases
- when more heat is applied the enzymes active site is completely changed and can not be reversed this is when the reaction has been denatured

45
Q

What is the optimum temperature

A

this is the temperature the enzyme works best at and at which the enzyme has reached its maximum rate of reaction
- this can be hot or cold

46
Q

describe the thermophilic bacteria hot spring high temperatures example

A
  • can survive in hot temperatures
  • the enzymes are heat stable this means that they have more disulphide bonds that do not break with heat and keep the shape of the protein molecules stable therefore there enzymes have high optimum temperatures
47
Q

How do you work out the rate of reaction

A

1/ time taken to reach end point

48
Q

What is the temperature coefficient

A

this refers to the increase in the rate of a process when the temperature is increased by 10degrees

49
Q

what is the equation of temperature coefficient

A

Q10= rate of reaction at (T+10) degrees/ rate of reaction at T degrees

50
Q

what happens to the temperature coefficient when temperatures are above the optimum

A

the temperature coefficient value drops, because higher temperatures alter the structure of the active sites of the enzyme molecule so that they are no longer complementary to the shape of substrate molecules

Biology Module 2 (17 decks)

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