proteins 1

Question 1

what is an anabolic reaction

Answer 1

requires energy to build up large molecules from small

Question 2

what is a catabolic reaction

Answer 2

releases energy when large molecules are broken down

Question 3

describe the lock and key model

Answer 3

• complementary 3D structures
• no major atomic rearrangements

Question 4

describe the induced fit model

Answer 4

• substrate induces a conformational change
• substrate fits well after reshape

Question 5

what is activation energy

Answer 5

• extra energy required to reach a transitional state for a reaction to proceed

Question 6

how is an enzyme used as a catalyst

Answer 6

• lower the activation energy of a reaction increasing the rate of reaction
• not consumed in the reaction

Question 7

how does temperature affect enzymes

Answer 7

• actively accelerated by increased temperature
• if too high the enzyme will denature

Question 8

how does pH affect enzymes

Answer 8

• affects side groups
• all have different optional pHs

Question 9

what are the conditions which affect enzymes

Answer 9

• temperature
• pH
• ionic strength
• substrate concentration

Question 10

what happens when an enzymes movement is restricted

Answer 10

• decreased activity

Question 11

what is acid-base catalysis

Answer 11

• enzyme acts as partial proton donor or acceptor

Question 12

what is covalent catalysis

Answer 12

• active site temporarily covalently modified

Question 13

what is metal ion catalysis

Answer 13

• electrophilic catalyst - stabilising a negative charge
• generate a nucleophile - increasing the acidity of a nearby molecule
• metal ion may bind to substrate

Question 14

what is approximation catalysis

Answer 14

• bringing two substrates together

Question 15

what are cofactors

Answer 15

molecules that aid enzymatic function

Question 16

what can be cofactors

Answer 16

• metal
• coenzymes - small organic cofactors
• prosthetic groups - tightly bound coenzymes
• cosubstrates - loosely associated coenzymes

Question 17

what are the units for the rate of reaction and what can they be measured by

Answer 17

• Ms-1
• decrease In substrate over time
• increase in product over time

Question 18

what is the rate constant

Answer 18

• relates chemical concentrations to rate

Question 19

what are the units for a first and second oder constant

Answer 19

• first - s-1
• second - M-1S-1

Question 20

what is maximal velocity (V max)

Answer 20

• reaction rate when enzyme is saturated and all active sites are filled

Question 21

what is the Michaelis constant (Km)

Answer 21

• substrate concentration at half V max

Question 22

what is the Michaelis menten equation

Answer 22

V0= V max x ( [S] / [S] + Km

Question 23

what does the substrate concentration tell you about the order

Answer 23

• low - first order - V0 is proportionate to substrate concentration
• high - zero order - V0 is approximately Vmax
• substrate concentration = Km - V0 = Vmax/2

Question 24

what occurs with the different shifts in the enzyme saturation curve

Answer 24

downwards - decrease Vmax
upwards - increase Vmax
right - increase Km - lower binding
left - decrease Km - higher binding

Question 25

what are the catalytic factors making glucokinase work

Answer 25

- high Vmax - high Km - respond to large glucose concentration

Question 26

what are the catalytic factors making hexokinase work

Answer 26

- lower Vmax - lower Km - not specific to glucose

Question 27

what is Vmax dependent on

Answer 27

- enzyme concentration - doubling enzyme concentration doubles the rate of reaction

Question 28

what is the rate limiting step

Answer 28

- slower step in pathway - high activation energy - limited substrate concentration

Question 29

what is the committed step

Answer 29

- first irreversible enzyme reaction in a pathway to a specific product

Question 30

what are the types of enzyme regulation

Answer 30

- allosteric - multiple forms of enzymes - reversible covalent modification - proteolytic activation - expression control - inhibition

Question 31

what is competitive inhibition

Answer 31

- competitive inhibitor binds to the active site

Question 32

what is an uncompetitive inhibitor

Answer 32

- binds to an allosteric site on the enzyme changing the active site shape

Question 33

what is a noncompetitive inhibitor

Answer 33

binds to the enzyme substrate complex and slows the rate of reaction

Question 34

what are irreversible/ suicide inhibitors

Answer 34

- inhibitor covalently binds enzymes - reacts with active site

Question 35

what is product inhibition

Answer 35

- product negative feedback

Question 36

what occurs with competitive inhibition to Vmax and Km

Answer 36

- Vmax same - Km increases - slope is steeper

Question 37

what occurs with uncompetitive inhibition to Vmax and Km

Answer 37

- Vmax lower - Km lower - no change in slope

Question 38

what occurs with non-competitive inhibition to Vmax and Km

Answer 38

- Vmax lower - Km same - slope steeper

Question 39

what is allosteric regulation

Answer 39

- activity at one functional site affects the activity at others

Question 40

what do the allosteric proteins contain

Answer 40

- distinct regulatory sites - multiple functional sites

Question 41

why are zymogens/proenzymes

Answer 41

- enzymes that need activating by another enzyme to function

Question 42

why is an enzyme saturation curve a sigmoidal curve

Answer 42

- velocity increases over a narrower range - allows for on and off switch