Enzymes & Proteins

Question 1

what are enzymes

Answer 1

biological catalysts, globular proteins that interact with substrates and cause them to react much faster

Question 2

anabolic and catabolic

Answer 2

ana= builiding up cata=breaking down

Question 3

metabolism

Answer 3

sum of all the different reaction pathways in a cell or organism

Question 4

mechanism of enzymes

Answer 4

molecules randomly collide but need right orientation and speed in order for it to be successful.
enzymes help the substrate molecules collide successfully to form products and therefore lower the activation energy

Question 5

what is Vmax

Answer 5

maximum initial velocity or rate of an enzyme catalysed reaction(highest capacity of enzyme activity0

Question 6

lock and key theory

Answer 6

active site is specific shaped area on enzymes in which only the right substrate bind
forms enzyme substrate complex , substrates react and form enzyme product complex then the products are released
substrate and R groups of enzyme can react forming temporary bonds holding it together and when products formed bonds break

Question 7

induced fit hypothesis

Answer 7

Active site changes shape slightly as substrate enters, interaction between substrate & enzyme weak but interactions induce changes in enzymes tertiary structure that strengthen binding and put strain on the substrate. weakens bonds in substrate(lowers activation energy)

Question 8

intercellular enzymes

Answer 8

enzymes that act inside the cell

Question 9

extracellular enzymes

Answer 9

nutrients taken from our food cannot directly enter cell plasma membrane so need to be broken down by enzymes into smaller molecules for digestion
single cellular organisms like bacteria/ yeast release extracellular enzymes to their immediate environment to break down larger molecules that can be digested

Question 10

digestion of starch

Answer 10

1starch broken down into disaccharide maltose by the enzyme amylase which is found in the salivary gland and pancreas
2maltose brown down into monosaccharide glucose by maltase found in the small intestine
glucose can be absorbed by cell lining of digestive system then is absorbed into the bloodstream

Question 11

digestion of proteins

Answer 11

trypsin is a protease that breaks proteins into smaller peptides which can then be broken down into smaller amino acids. Made in the pancreas and released into the small intestine where it acts on proteins which is then absorbed into cell lining then the bloodstream

Question 12

how does temperature affect proteins

Answer 12

increase particles Ke
particles move faster and more
collisions
in enzymes more enzyme substrate complex formed

Question 13

temperature co-efficient q10

Answer 13

measure how much the Ror increases with a 10*c increase in temperature
for enzyme controlled reactions usually taken as 2

Question 14

denaturing enzymes

Answer 14

at high temps the bonds holding the proteins together vibrate and break causing the tertiary structure to irreversibly change making it lose its complementary function(denatured)

active site changes shape and can no longer for ES complexes so no longer function as a catalyst

Question 15

what is optimum temperature

Answer 15

the temperature in which enzymes have the highest rate of activity for humans its usually 40*c once enzymes have denatured above optimum temperature the rate of reaction decreases rapidly
q10 no longer efficent

Question 16

temperature extremes

Answer 16

enzymes adapted for colder temperatures are more flexible mostly at active site (less stable than enzymes at higher temperatures) smaller temp changes denature them
for warmer temperatures enzymes have increased H bonds and disulphide bridges to withstand temperature increase

Question 17

Ph

Answer 17

acidic conditions have many H+ ions in which react with polar R groups causing their current bonds to break rather than bonding with each other , within a range if the ph returns to normal the enzyme renatures
at extreme changes enzyme irreversibly changed no longer complementary and can no longer act as a catalyst

Question 18

substrate & enzyme concentration

Answer 18

increasing substrate concentration increases the number of collisions with the active site more ES complexes so higher rate of reaction same with enzymes more active sites available
up until V max where the maximum rate of reaction occurs until another factor is increased

Question 19

competitive inhibition

Answer 19

similar shape molecule
blocks substrate from active site
cannot carry out function
they compete with each other for the enzyme, this reduces the number of substrate molecules that can bind so slows down the rat of reaction mostly reversible

Question 20

competitive examples

Answer 20

statins used in the synthesis of cholesterol, prescribed to reduce blood cholesterol concentration( can cause heart disease if too high)

Question 21

Non competitive inhibition

Answer 21

binds to allosteric site
permanently changes shape of active site
no longer complementary so cannot bind to enzyme

Question 22

effects of non como

Answer 22

increasing enzyme concentration doesn’t effect the rate of reaction but increasing non competitive inhibitors concentration causes slower rate of reaction less active sites available

Question 23

examples of irreversible non competitive inhibitors

Answer 23

proton pump inhibitons used to treat long term indigestion( irreversibly block enzyme that secretes H+ ions into the stomach. PPIs vert effective in reduce excessive stomach acid

Question 24

end product inhibition

Answer 24

product of an enzyme catalysed reaction acts as an inhibitor to the enzyme that made it to maintain concentration levels

Question 25

what is a cofactor

Answer 25

an inorganic molecule that helps carry out the function of a biological catalyst, may transfer atoms from one reaction to another

Question 26

What are co enzymes

Answer 26

organic molecules that form a part of the active site on an enzyme

Question 27

common cofactors

Answer 27

obtained by our diet iron, calcium, chloride ions, zinc ions. Amylase breaks down starch chloride ions needed for the correct formation of the active site

Question 28

common co enzymes

Answer 28

derived from vitamins class of organic molecule found in the diet. Vitamin B3 used to synthesise NAD, a coenzyme responsible for transfer of H atoms between molecules in respiration

Question 29

prosthetic groups

Answer 29

Cofactors that are required by enzymes to carry out catalytic function, some cofactors are loosely/ temporarily bound to the enzyme, prosthetic groups are a permanent feature of proteins

Question 30

precursor activation

Answer 30

most enzymes are produced as inactive precursor enzymes, mainly for enzymes that can cause damage to cells that produce them or the tissues they are released too.
need to undergo a change in tertiary shape to be activated by a cofactor
apoenzyme to holoenzyme

Question 31

activation of enzymes

Answer 31

sometimes done by action of another enzyme that cleaves certain bonds in a molecule , or changes in conditions that permanently alter the tertiary structure
Eg when stomach acid activates pepsinogen with the H+ (digestive enzyme)