Enzymes (minus poisons and medicinal drugs)

Question 1

Turnover number

Answer 1

number of reactions an enzyme can catalyse per second

Question 2

Why are enzymes better than chemical catalysts?

Answer 2

10¹² x faster at low temp, neutral pH, normal pressure
more specific
no unwanted by-products
rarely mistakes

Question 3

metabolites

Answer 3

reactants, intermediates, products

Question 4

catabolic

Answer 4

broken down to smaller molecules

release energy

Question 5

anabolic

Answer 5

synthesis large molecules

Question 6

Catalase

Answer 6

enzyme
pH7 optimum
protects cells from damage from reactive oxygen by breaking down hydrogen peroxide (by-product of metabolic reactions)
4 polypeptide chains
iron haem group
inside peroxisomes (vesicles)
when WBC ingest pathogens, kill with catalase

Question 7

Amylase

Answer 7

in salivary gland to digest polysaccharide starch

made in pancreas to do same thing in lumen of small intestine

Question 8

Trypsin

Answer 8

made in pancreas, acts in lumen of small intestine
digest proteins
pH 7.5, 8.5

Question 9

Cofactors ensures…

Answer 9

enzyme-catalysed reaction takes place at appropriate rate

Question 10

Prosthetic groups

Answer 10

a cofactor that is permanently bound by covalent bonds to an enzyme

Question 11

Which enzyme has a zinc ion as a prosthetic group?

and explain it

Answer 11

carbonic anhydrase in RBC
catalyses CO₂ and H₂O to carbonic acid then to protons and hydrogencarbonate ions
it enables CO₂ to be carried in blood from respiring tissues to lungs

Question 12

co-substrates

Answer 12

cofactor with substrate form correct shape for active site

Question 13

some _________ change the ______ ____________ on substrates/enzymes so _________ _____ are easier to form in enzyme-substrate complex

Answer 13

cofactors
charge distributions
temporary bonds

Question 14

Amylase turns ______ to _______ and the enzyme’s prosthetic group is a ________ ___.

Answer 14

starch
maltose
chloride ion

Question 15

Coenzymes

Answer 15

organic, non-protein, bind temporarily to the active site and are chemically changed during reactions

Question 16

The induced-fit hypothesis is how the ______-_________ complex is __________.

Answer 16

enzyme-substrate

stabilised

Question 17

What causes the slight change in the active site in the induced-fit hypothesis?
What causes the product to leave the active site?

Answer 17

subtle changes of shape of side chains (R groups) of amino acids
product is slightly different shape so detaches from active site

Question 18

Why do enzymes lower the activation energy?

Answer 18

they have a specific site shape so bring substrate molecules together without the need for heat

Question 19

Why does temperature affect an enzyme’s active site but not it’s shape completely?

Answer 19

Weak hydrogen/ionic bonds hold the active site’s tertiary structure while stronger peptide bonds are between amino acids so the primary structure isn’t affected.

Question 20

psychrophilic bacteria live in…

thermophilic can live at…because…

Answer 20

cold conditions

high temperatures…have more disulfide bonds which don’t break with heat

Question 21

buffer

Answer 21

resists change in pH by accepting or donating H⁺ ions because H⁺ interferes with hydrogen bonds/ionic forces holding tertiary structure of active site.

Question 22

if normal pH is restored…

Answer 22

H bonds re-form and active site is restored, except for if pH is extreme.

Question 23

amylase function + pH
pepsin (protease enzyme) function + pH
trypsin/enterokinase function + pH

Answer 23

starch to maltose, pH 6.8
large protein to small peptide molecules, pH 1-2
peptides to amino acids, pH 7.8 (salts in bile neutralise food)

Question 24

How does body change enzyme concentration?

Answer 24

depending on cell’s needs, genes for synthesising enzymes can be switched on or off

Question 25

Enzyme degradation

Answer 25

elimination of abnormal proteins that might harm cell, metabolism is regulated by eliminating unnecessary enzymes is there is too much.

Question 26

competitive enzyme inhibitor

Answer 26

similar shape to substrate so competes for active site, prevents ES complex. To reverse effects, add substrate. Inactivator is if the competitive inhibitor binds irreversibly to the enzyme.

Question 27

non-competitive enzyme inhibitor

Answer 27

attaches to part of enzyme that’s not the active site (allosteric site) but changes the shape of the active site. Adding substrate doesn’t increase rate again. Some bind reversibly, some irreversibly.

Question 28

End-product inhibition is when…

Answer 28

the product stays bound to the enzyme to stop it from forming more products then the cell needs. This is negative feedback.

Question 29

Types of cofactors

Answer 29

Coenzymes

Prosthetic groups