lecture 13 - carbohydrate metabolism

Question 1

What are the two main features of ATP?

Answer 1

• thermodynamically unstable

- kinetically stable

Question 2

What is thermodynamic stability?

Answer 2

concerned with the direction/ feasibility of the process

Question 3

What is kinetic stability?

Answer 3

concerned with the rate

Question 4

What happens under cellular conditions to ATP hydrolysis

Answer 4

Get doubles the amount of energy

Question 5

What is intermediary metabolism?

Answer 5

• chemistry achieved in small steps

- Each step catalysed by enzymes

Question 6

What are the two mechanisms by which glucose can enter cells?

Answer 6

• Facilitated diffusion transporters ( the GLUT family)

- Sodium linked active transporters ( The SGLT family)

Question 7

What does GLUT 4 do?

Answer 7

Translocates through multiple intracellular compartments

Question 8

What does insulin do to GLUT 4?

Answer 8

insulin receptors signalling stimulated GLUT 4 exocytosis

Question 9

An overview of the first half of Glycolysis

Answer 9

(reactions 1-5)The hexose glucose is phosphorylated and cleaved to yield 2 molecules of triose glyceraldehyde - 3- phosphate

Question 10

The second half of glycolysis

Answer 10

The two molecules go glyceraldehyde -3-phosphate are converted in to pyruvate.

Question 11

What does glucose turn into in the first step of glycolysis?

Answer 11

Glucose- 6 - phosphate

Question 12

What is the name of the enzyme in the first reaction of glycolysis ?

Answer 12

hexokinase

Question 13

what occurs in the first reaction glycolysis?

Answer 13

A phosphate group is added to the C6

Question 14

Why are magnesium ions needed in the first step of glycolysis?

Answer 14

Complexing with the phosphate oxygen atoms, shield the negative charge

Question 15

why does hexokinase perform an induced fit, enclosing ATP and glucose?

Answer 15

must be shielded from water , to make suer phosphate isn’t simply cleaved off by ATP

Question 16

what are the two parts of human hexokinase?

Answer 16

• Regulatory domain

- kinase domain

Question 17

Where are hexokinases found?

Answer 17

Most tissues in the body

Question 18

where is glucokinase found?

Answer 18

in the liver

Question 19

`How are Hexokinases 1-3 regulated?

Answer 19

build up of G6P , enzyme inhibited . This occurs when there is too much ATP . If the cell does not need ATP , then it also does not take up glucose

Question 20

what does Glucose - 6 - phosphate turn into in the second reaction of glycolysis?

Answer 20

Fructose - 6 - phosphate . From aldose to ketose

Question 21

What is the enzyme for reaction 2 of glycolysis?

Answer 21

Phosphoglucose isomerase

Question 22

Reaction mechanism for phosphoglucose isomerase?

Answer 22

Ring opening , followed by isomerization and ring closure. The active site residues are thought to be lys and His -Glu .

Question 23

what is Fructose - 6-phosphate converted into in the third reaction of glycolysis?

Answer 23

Fructose 1, 6 - bisphosphate

Question 24

What is the enzyme in the third reaction of glycolysis?

Answer 24

phosphofructokinase (PFK)

Question 25

Which of the first three reactions in glycolysis need ATP inout?

Answer 25

the first and the third

Question 26

What happens in the first step?

Answer 26

• Irreversible and proceeds with a large decrease in free energy.