2.4.1 enzymes - biological catalysts

Question 1

active site

Answer 1

indented area on the surface of an ezyme molecule, with a shape that’s complementary to the shape of the substrate molecule

Question 2

catalyst

Answer 2

chemical that speeds up the rate of reaction & remains unchanged/reusable at the end of the reaction

Question 3

extracellular

Answer 3

outside the cell

Question 4

intracellular

Answer 4

inside the cell

Question 5

metabolic/metabolism

Answer 5

the chemical reactions that take place inside living cells/organisms

Question 6

product

Answer 6

molecule produced from substrate molecules, by an enzyme-catalysed reaction

Question 7

substrate

Answer 7

molecule that’s altered by an enzyme-catalysed reaction

Question 8

why are enzymes called biological catalysts

Answer 8

speed up metabolic reactions in living organisms & their actions affect both structure/function within cells, tissues & organs

Question 9

how effective is a small amount of catalyst

Answer 9

can catalyse the conversion of a large number of substrate molecules into product molecules

Question 10

turnover number

Answer 10

the number of reactions an enzyme molecule can catalyse per second

Question 11

why are biological catalysts better than chemical catalysts - conditions

Answer 11

• chemical catalysts require very high temperatures, increased pressures & extremes in pH
• enzymes speed up metabolic reactions by up to 10x12 at lower temperatures, often at neutral pH & normal pressures

Question 12

why are biological catalysts better than chemical catalysts - specificity

Answer 12

• enzymes are more specific —> do not produce unwanted by-products & rarely make mistakes
• the cells where they’re made &/or act can also regulate their production & activity to fit the needs of the cell/organism at the time

Question 13

how enzyme structure determines function

Answer 13

• for catalysing some reactions, may need help of cofactors
• instructions for production are encoded in genes —> if the gene has a mutation which alters the amino acid sequence in the protein, this may alter the enzymes tertiary structure & prevent it from functioning
• if an enzyme that catalyses a metabolic reaction is deficient then a metabolic disorder results
• catalyse formation of organisms structural components (eg. collagen in bone, cartilage) —> some genetic disorders cause malformations of connective tissue & can be harmful (eg. ‘stone man syndrome’)

Question 14

how many amino acids consist in the active site

Answer 14

about 6-10

Question 15

why is the tertiary structure of the active site crucial

Answer 15

it’s shape is complementary to the shape of the substrate molecule

Question 16

each type of enzyme is highly specific in it’s function - how does this impact the active site?

Answer 16

the enzyme can only catalyse a reaction involving the particular substrate molecule that fits into it’s active site

Question 17

how can the shape of the active site be altered

Answer 17

by changes in temp. & pH which affect the bonds that hold the proteins in their tertiary structure

Question 18

what do enzymes catalyse

Answer 18

wide range of intracellular & extracellular reactions

Question 19

properties of intracellular enzymes

Answer 19

• each metabolic pathway in a living cell is 1 of a series if consecutive reactions & every steps catalysed by a specific enzyme that produces a specific product
• various reactants & intermediates act as substrates for specific enzymes
• respiration & photosynthesis are examples of complex metabolic pathways, with many enzymes involved

Question 20

what are the reactions, intermediates & products known as (intracellular)

Answer 20

metabolites

Question 21

what are described as catabolic (intracellular)

Answer 21

some metabolic pathways where metabolites are broken down to smaller molecules & release energy

Question 22

what are described as anabolic (intracellular)

Answer 22

other metabolic pathways where energy is used to synthesise larger molecules from smaller ones

Question 23

what’s catalase

Answer 23

• found in nearly all living organisms that are exposed to oxygen
• very important enzyme
  —> protects cells from damage by reactive oxygen by quickly breaking down hydrogen peroxide to water and oxygen

Question 24

what’s hydrogen peroxide

Answer 24

a potentially harmful by-product of many metabolic reactions

Question 25

what does catalase consist of

Answer 25

4 polypeptide chains & contains a haem group with iron

Question 26

is it a fast acting enzyme - whats its turnover number

Answer 26

• fastest-acting enzyme
• highest turnover number known of about 6 million per second

Question 27

where is catalase found in eukaryotic cells

Answer 27

found inside small vesicles called peroxisomes

Question 28

how do white blood cells use catalse

Answer 28

when they ingest pathogens they use it to help kill the invading microbe

Question 29

what’s the optimum pH/temp for catalase in different environments

Answer 29

• human catalse: around pH 7 & 45 degrees
• other species it varies between pH 4 & 11
• for some thermophilic archaea it’s 90 degrees

Question 30

describe extracellular enzymes - use example of fungi

Answer 30

• some enzymes are secreted from the cells once made & act on their substrates outside
• fungi (eg. bread mould ‘mucor’) release hydrolytic enzymes from their thread-like hyphae —> enzymes digest carbohydrates, proteins & lipids in the bread & the products of digestion - glucose, amino acids, glycerol & fatty acids - are absorbed into the fungal hyphae for use in respiration & growth

Question 31

how do extracellular enzymes work in our digestive system

Answer 31

• many are secreted from cells lining the alimentary canal, into the gut lumen
• they extracellulay digest large molecules (eg. proteins, lipids, carbohydrates & nucleic acids) found in food
• products of digestion are absorbed (via epithelial cells of the gut wall) into the bloodstream to be used for respiration, growth & tissue repair

Question 32

where is amylase produced & what does it do

Answer 32

• salivary glands in the mouth & in pancreas
• mouth: digests polysaccharide starch into disaccharide maltose
• pancreas: catalyses same reaction^ in lumen of small intestine

Question 33

where is trypsin made & what does it do
- what’s its optimum pH

Answer 33

• pancreas
• acts in lumen of small intestine to digest smaller peptides by hydrolysing peptide bonds
• optimum pH = between 7.5 & 8.5