Carbohydrates 2

Question 1

What is glycolysis?

Answer 1

The process of glucose converting into 2 pyruvate molecules

Question 2

What happens to glucose when it enters a cell?

Answer 2

It is phosphorylated by kinase using ATP

Question 3

Where is glucokinase found and when is it active?

Answer 3

Liver and pancreas. In the prescience of insulin only

Question 4

Can G6P be converted back into glucose?

Answer 4

In glycolysis, the reaction is irreversible. It IS possible but requires a lot of energy

Question 5

What happens after G6P is created?

Answer 5

It is converted to F6P (fructose 6 phosphate)

Question 6

What happens once G6P has been converted to F6P? Can this next step be reversed?

Answer 6

F6P is phosphorylated again to form Fructose 1-6 bis phosphate. This step is not reversible.

Question 7

What is the rate limiting step of glycolysis and why?

Answer 7

Rate of conversion of F6P to F1-6BP. It’s the slowest step.

Question 8

When do our bodies produce the enzymes required to undergo glycolysis?

Answer 8

When we need energy

Question 9

What are the net products of glycolysis?

Answer 9

2 Pyruvate, 2 ATP and 2 NADH molecules

Question 10

What are the three irreversible reactions in glycolysis?

Answer 10

Glucose to G6P (phosphorylation), F6P to fructose 1-6 bisphosphate (phosphorylation), and PEP (phosphoenolpyruate) to Pyruvte (dephosphorylation)

Question 11

What are three products that pyruvate can produce?

Answer 11

Ethanol, Lactate, Acetyl CoA then co2

Question 12

How is ethanol formed from pyruvate?

Answer 12

Converted to acetaldehyde, then to ethanol, using H+ from NADH

Question 13

How is lactate produced from pyruvate?

Answer 13

Lactate dehydrogenase catalysed reaction, using H+ from NADH

Question 14

What is the fate of blood lactate?

Answer 14

It’s released into the blood and taken to the liver where gluconeogenesis occurs. Eventually converted back into glucose

Question 15

What is the function of pyruvate dehydrogenase?

Answer 15

Converts pyruvate into Acetyl CoA. Removed H+ from pyruvate, generating NADH, hence dehydrogenase

Question 16

Where does the conversion of pyruvate to acetyl coA occur?

Answer 16

Mitochondria

Question 17

Why are there 3 irreversable steps in glycolysis?

Answer 17

The delta G values of those reactions are too low, so it would take too much energy to reverse

Question 18

What is the function of gluconeogenesis and where does it occur?

Answer 18

To convert pyruvate back into glucose, to be released in the blood. Occurs in the liver

Question 19

What is the 1st step in process of gluconeogenesis?

Answer 19

Pyruvate is converted to oxaloacetate, then PEP. Occurs partly in mitochondria

Question 20

What is the second step of gluconeogenesis and the product?

Answer 20

Fructose 1-6 bisphosphate is converted into fructose 6 phosphate. Phosphate is released as a free ion and not converted back to ATP as it requires too much energy

Question 21

What is the third step of gluconeogenesis and its product?

Answer 21

G6P to Glucose. Produces phosphate, released as a free ion

Question 22

What is the fate of absorbed galactose?

Answer 22

It is converted into G6P in the liver

Question 23

What is the fate of absorbed fructose?

Answer 23

It’s converted into other molecules later on in the glycolysis cycle

Question 24

What is the effect of drinking alcohol on gluconeogenesis?

Answer 24

It converts NAD+ to NADH, inhibiting gluconeogenesis. Too much alcohol can kill, as glucose cannot be made.

Question 25

What is the cori cycle?

Answer 25

Muscles producing lactate through substrate-level phosphorylation which can then be converted to glucose through gluconeogenesis. Allows muscle to continue contracting

Question 26

What are bypass reactions and where are the found?

Answer 26

Found in gluconeogenesis to make the process energetically feasible

Question 27

Is glycogen osmotically active?

Answer 27

No - its osmotically inactive because it can’t leave the cell membrane and doesn’t affect osmolarity. This is a benefit of storing glucose as glycogen