enzymes

Question 1

enzyme features

Answer 1

• globular proteins (have a tertiary structure)
• act as biological catalysts
• alter rate without bring permanently changed or used up
• able to be reused

Question 2

how are enzymes biological catalysts

Answer 2

they speed up many metabolic reactions in living organisms

Question 3

what is the turnover number

Answer 3

the number of reactions an enzyme can catalyse per second

Question 4

how are enzymes (biological catalysts) different to chemical catalysts

Answer 4

• chemical catalysts usually need high temps, increased pressures and an extreme ph
  —> however biological catalysts can speed reactions up to 10^12 times at lower temps, normal pressure and a neutral ph
• enzymes are more specific
• enzymes dont produce unwanted products

Question 5

how do enzymes help if 2 substrates need to be joined

Answer 5

being attached to the enzyme holds them close together and reduces any repulsion so they can bond easily

Question 6

how does an enzyme help break a stubstrate down

Answer 6

when the substrate fits into the active site, a strain is put onto the bonds in it, making it break down easier into smaller molecules

Question 7

how do enzymes get their structure

Answer 7

• they’re chains of AAs, therefore theyre coded for by the dna of the organism
• the instructions for making enzymes are encoded in genes

Question 8

what happens to the enzyme if a gene has a mutation on

Answer 8

• it will alter the sequence of AAs
• this may alter the enzymes tertiary structure and prevent it from functioning
• this can then lead to problems with metabolic functions from; digestion, or the formation of blood vessel walls, joints and connective tissues

Question 9

what is the active site

Answer 9

• a specific indentation or cleft on the surface of an enzyme, it consists of about 6-10 AA
• shape is complementary to the shape of the substrate
• shape can be altered by temp or ph changes

Question 10

where do enzymes work

Answer 10

they can catalyse both intracellular and extracellular reactions inside and outside of the cell

Question 11

what are intracellular enzymes

Answer 11

• work WITHIN cells and organelles
• often over 1000 reactions occur simultaneously, each being catalysed by a different enzyme
  —> some of these are part of a metabolic pathway

Question 12

what is a metabolic pathway

Answer 12

a series of connected chemical reactions that feed one another, each step catalysed by a different enzyme

Question 13

what are metabolites

Answer 13

the intermediate products of metabolic reactions

Question 14

what are the two types of metabolic pathways

Answer 14

anabolic - E is used to synthesise smaller molecules into larger ones
catabolic - large molecules are broken down into smaller ones, releasing E

Question 15

what is catalase

Answer 15

• a type of intracellular enzyme which identifies found in nearly all living organisms exposed to O
• fastest acting enzyme - turnover number is 6mil per second
• optimum pH in humans is ph7
• optimum temp in humans is 45 degrees
• found in vesicles - peroxisomes

Question 16

what does catalase do

Answer 16

• protects cells from damage by breaking down hydrogen peroxide into water and oxygen
• used by WBCs to kill invading microbes when WBCs try to ingest pathogens

Question 17

catalase structure

Answer 17

• 4 polypeptide chains and a haem group with iron

Question 18

what are extracellular enzymes

Answer 18

enzymes that have been secreted from cells and act on substrates outside of cells

Question 19

how is fungi use extracellular enzymes

Answer 19

it releases extracellular hydrolytic enzymes onto food (such as bread) which digest carbs, proteins and lipids, and then the products of digestion are absorbed into the fungal hyphae for growth and respiration

Question 20

what are cofactors

Answer 20

non -protein molecules that attach to enzymes and help them catalyse reactions, especially redox reactions

Question 21

what are prosthetic groups

Answer 21

they’re cofactors which are permanently bound, by covalent bonds, to an enzyme

Question 22

what is the prosthetic group on carbonic anhydrase

Answer 22

a zinc ion

Question 23

what is the equation for carbonic anhydrase and what does it do

Answer 23

carbon dioxide and water <—> carbonic acid <—> bicarbonate and H ion

• the reaction enables CO2 to be carried in the blood from respiring tissues to the lungs

Question 24

what is an enzyme substrate complex

Answer 24

it forms when the substrate and enzyme molecules temporarily bind together

Question 25

what do other cofactors do

Answer 25

• some aren’t permanently bound, and instead they temporary associate with either the substrate or the enzyme during reactions to increase rate
• some change the charge or distribution of charge on the surface of the substrate or enzyme to make the ESC easier to form
• some are cosubstrates and coenzymes

Question 26

what are cosubstrates

Answer 26

cosubstrates and the substrate together form the correct shape to bind to the active site

Question 27

what are coenzymes

Answer 27

small, organic non-protein molecules that temporarily bind to the active site just before, or at the same time as, the subtrate binds
—> they’re chemically changed during reactions and need to be recycled to their original state

Question 28

where are many coenzymes derived from

Answer 28

water -soluble vitamins