Gluconeogenesis and glucose homeostasis

Question 1

When does gluconeogenesis occur

Answer 1

• exercise (lactate)
• short term fasting (alanine)
• Diabetes (insulin sensitivity)
• Trauma (peripheral insulin resistance)

Question 2

What noncarbohydrate precursors does gluconeogenesis use to make glucose

Answer 2

• lactate
• Amino acids (alanine)
• Glycerol (triacylglycerols)

Question 3

Where does gluconeogenesis occur

Answer 3

liver
kidney
small intestine

Question 4

Which part of the cell does gluconeogenesis occur

Answer 4

CYtosol

Question 5

How does gluconeogenesis occur

Answer 5

Same as glycolysis apart from 3 steps;

• pyruvate to PEP
• F1,6 BP to F6P
• G6P to glucose

Question 6

What does pyruvate get turned into and and what does this get turned into

Answer 6

Pyruvate —oxaloacetate—-PEP

Question 7

Why is the malate shuttle used

Answer 7

Used because oxaloacetate can’t get out of mitochondria to cytosol so needs to get converted to malate. Malate then leaves mitochondria via malate shuttle then gets converted to oxaloacetate again

Question 8

How many carbons is pyruvate and how many carbons is oxaloacetate

Answer 8

3

4

Question 9

What enzyme turns pyruvate to oxaloacetate

Answer 9

pyruvate carboxylase

Question 10

What is needed to turn pyruvate to oxaloacetate and what is the by-product

Answer 10

needs; Co2 and ATP

produces; ADP+ Pi

Question 11

Where is pyruvate carboxylase found

Answer 11

mitochondrion

Question 12

To turn oxaloacetate to malate and back to oxaloacetate, what is needed

Answer 12

-REDOX of NADH

Question 13

To turn oxaloacetate to PEP, what enzyme is needed

Answer 13

PEP carboxykinase

Question 14

What is needed to turn oxaloacetate to PEP and what are the by-products

Answer 14

needs; GTP

by products; GDP + Co2

Question 15

What does pyruvate carboxylase catalyse and where is it found

Answer 15

Glucose to pyruvate

-found in all tissues

Question 16

Why is pyruvate carboxylase found in all tissues

Answer 16

There’s a need to replenish oxaloacetate for example in the TCA cycle (as pyruvate produces oxaloacetate)

Question 17

What then happens to PEP?

Answer 17

gets converted to Fructose 1,6 bisphosphate

Question 18

What happens to fructose 1,6 bisphosphate and why is this an important reaction

Answer 18

Gets turned to fructose 6 phosphate by FRUCTASE 1,6 BISPHOSPHATASE

-tightly regulated

Question 19

What happens to fructose 6 phosphate

Answer 19

Gets turned to glucose 6 phosphate by phosphoglucose isomerase

Question 20

What happens to Glucose 6 phosphate

Answer 20

Gets turned to glucose by glucose 6 phosphatase (removes phosphate group so glucose can move out of cell)

Question 21

When does gluconeogenesis occur (i.e. glucose and ATP levels )

Answer 21

• glucose levels are low

- ATP levels are high

Question 22

How are reciprocal regulation of gluoneogeneis and glycolysis affected

Answer 22

Allosterically

Question 23

What is gluconeogenesis regulated by hormonally

Answer 23

Insulin

Glucagon

Question 24

Role of insulin in regulation

Answer 24

• promotes synthesis of glycolytic enzymes PFK, PK, PFK2

- inhibits synthesis of PEPCK

Question 25

Role of glucagon in regulation

Answer 25

-Increase expression of PEPCK and F1,6BPase

Question 26

What is the Cori Cycle

Answer 26

Glycolysis in muscle;

• glucose to pyruvate then lactate
• lactate goes into blood and then to liver

Gluconeogenesis in liver;

• lactate from muscle gets converted to pyruvate and then to glucose
• glucose goes to blood and then back to the muscle

Question 27

How are amino acids used as gluconeogenic precursors

Answer 27

• Remoce amino groups

- Carbon skeletons can be converted to glucose