Session 6-Enzymes Flashcards Preview

Semester 1-MCBG > Session 6-Enzymes > Flashcards

Flashcards in Session 6-Enzymes Deck (19):
1

Complete the sentence:
The phosphorylation of glucose is ___________ but it needs activation energy because negatively charged ______ atoms repel each other and the reaction is catalysed by the enzyme __________.

Spontaneous
Oxygen
Hexokinase

2

How is the phosphorylation of glucose catalysed?

By providing positive charges from the side chains on the AA of hexokinase

3

In which three ways can you increase the rate of reaction?

1. Increasing the temperature-increases the number of molecules with the activation energy
2. Increasing the concentration-increases the chance of molecular collisions
3. Enzymes-biological catalysts that increase rate by lowering activation energy and facilitating the formation of the transition state

4

What is the transition state?

The high energy intermediate that lies between the substrate and product

5

What are some features of enzymes? (4)

Highly specific
Unchanged after reaction
Do not affect reaction equilibrium
Increase rate of reaction

6

True or false: most of the enzyme acts as a scaffold to create the active site

TRUE

7

Complete the sentence:

Substrate molecules are bound in the _____ or _______ that usually excludes water

Cleft
Crevice

8

What shape is the graph of reaction velocity against substrate concentration?

Rectangular hyperbola

9

Define Vmax

Maximal rate when all enzyme active sites are saturated with substrate

10

Define Km

Substrate concentration that gives half maximal velocity

11

Complete the sentence:

Km values give a measure of the ________ of an enzyme for its substrate

Affinity

12

What does a low Km value mean?

Enzyme has a high affinity for its substrate

13

What does a high Km value mean?

Enzyme has a low affinity for its substrate

14

What is 1 unit equal to?

The amount of enzyme that converts 1 micromol of product per minute under standard conditions

15

True or false: the rate of enzyme catalysed reaction is proportional to the concentration of the enzyme

TRUE

16

What is the name for the model that predicts that a plot of velocity against substrate concentration will be a rectangular hyperbola?

Michaelis-Menten model

17

What is the name given to the linear plot when the Michaelis-Menten equation is rearranged?

Lineweaver-Burk plot

18

Give an example of an irreversible enzyme inhibitor

Nerve gas, such as sarin

19

What is the difference between competitive and non-competitive inhibitors, in terms of Vmax and Km?

Competitive-affects Km (increases) but not Vmax
Non-competitive-affects Vmax (decreases) but not Km