Gluconeogenesis

Question 1

What are 2 reasons glucose homeostasis is importent in the blood

Answer 1

Glucose is only energy source for RBCs

Needed for supply to cns and the brain (use glucose in neurones)

Question 2

What are the sources of glucose

Answer 2

Fluids
Food
Glycogen storage of glucose 6 phosphate

Question 3

When can someone become hypoglycaemic

Answer 3

Due to insulin overdose Eg injections

Starvation

After exercise

Question 4

When can someone become hyperglycaemic

Answer 4

After food intake
Insulin lacking injections
(Insulin resistance)

Question 5

Name 5 things needed to produce own glucose from body

Answer 5

Pyruvate 
Lactate 
Citric acid intermediates (oxaloacetate) 
Amino acids 
Glycerol - from lipid catabolism

Question 6

What is the cycle called which converts lactate into pyruvate then into glucose

Answer 6

Cori cycle

Question 7

Where is lactate in the muscle converted into pyruvate to start gluconeogenesis

Answer 7

In the liver (travel from muscle to liver in blood)

Question 8

What amino acid is needed in the cori cycle and why

Answer 8

Alanine

It is needed to be a way of transporting pyruvate instead of lactate to stop blood fill with lactate

Question 9

How is alanine shuttles used to produce pyruvate and release in liver

Answer 9

Lactate dehydrogenase first in the muscle converted into pyruvate

NH3 is added to then produce alanine

Alanine transported into liver from muscle via blood

NH3 is then removed to form pyruvate

Question 10

Is pyruvate conversion back into glucose favoured ?

Answer 10

No, uses a lot of energy (Endergonic)

Question 11

Which 3 parts of gluconeogenesis differ from glycolysis of glucose into pyruvate

Answer 11

Pyruvate to phosphoenolpyruvate

Fructose 16 bisphosphate into fructose 6 bisphosphate

Glucose 6 phosphate into glucose

Question 12

What is pyruvate (3c) first converted to gluconeogenesis and how (which enzyme)

Answer 12

Oxaloacetate (4c)

Pyruvate carboxylase adds co2 to pyruvate
USING ATP HYDROLYSIS

Forms oxaloacetate (4c)

Question 13

Why does pyruvate need to be converted to oxaloacetate inside the mitochondria

Answer 13

Because pyruvate carboxylase only present in mitochondria

Question 14

What happens to oxaloacetate next

Answer 14

Converted into malate
via malate dehydrogenase

Malate then transports into the cytoplasm where malate dehydrogenase converts it back into oxaloacetate

(Via nad reduction)

Question 15

What happens to oxaloacetate when back in the cytoplasm

Answer 15

Needs to release 1 co2 to form phosphoenolpyruvate

Also needs to be phosphorylated
Via GTP HYDROLYSIS

enzyme phosphoenolpyruvate carboxykinase catalyses this

Question 16

What happens once phosphoenolpyruvate is produced up to fructose 16 bisphosphate

Answer 16

PEP converts to 2 phosphoglycerate via addition of h20 by enolase

2 phosphoglycerate converted to 3 phosphoglycerate by phosphoglycerate mutase

3 phosphoglycerate converted to 13 bos phosphoglycerate by phosphoglycerate kinase ATP HYDROLYSIS

1 phosphate is then released and also NADH converts back to NAD via glyceraldahyde 3 phosphate dehydrogenase

Produces G3p which is converted back to 16 bisphosphate (6C)

Question 17

How is fructose 1,6 bisphosphate converted back into fructose 6 phosphate

Answer 17

1 6 bisphosphatase

Adds h20 which cleaves phosphate from 16 bisphosphate into fructose 6 bisphosphate

Question 18

How is glucose 6 phosphate converted into glucose

Answer 18

Glucose 6 phosphatase adds H2O cleaving 1 pi from g6p into glucose

Question 19

Where does the 4 ATP and 2 GTP needed for gluconeogenesis come from

Answer 19

Lipid oxidation - glycerol used

Amino acid catabolism (back into intermediates)

Question 20

Which enzyme uses 2 GTP for hydrolysis

Answer 20

Phosphoenol carboxykinase

Removes co2 from oxaloacetate and then phosphorylates it

Question 21

Which 2 reactions use ATP hydrolysis

Answer 21

Conversion of pyruvate into oxaloacetate via pyruvate carboxylase (addition of co2)

Conversion of 3 phosphoglycerate into 13 bus phosphoglycerate

Question 22

What 2 things are positive modulators for gluconeogenesis (opposite to glycolysis)and why are they positive

Answer 22

Citrate and acetyl coA presence

Shows high energy status (high amount of ATP being generated via glycolysis)

Acetyl coa activated pyruvate kinase

Citrate activates 16 bisphosphatase

Question 23

What does citrate and coA activate

Answer 23

1 6 bisphosphatase

Inhibits phosphofructokinase

Question 24

What things are negative modulators of gluconeogenesis and why

Answer 24

AMP and adp

Amp produced by adenylate cyclase enzyme activated pKa which allosterically inhibits F16 bisphosphatase

ADP presence shows the low energy status so not enough ATP present for gluconeogenesis
(Inactivated pyruvate carboxylase)

Question 25

Does presence of fructose 2 6 bisphosphate inactivate or activate 1 6 bisphosphatase in gluconeogenesis

Answer 25

Inactivates it

It activates phosphofructo kinase in glycolysis instead

Question 26

How does lipid oxidation and amino acid catabolism acctually form energy source

Answer 26

Lipid oxidation coverted into acetyl coa for the citric cycle then generating ATP

Amino acids also when broken down reproduce things like oxaloacetate, pyruvate, a keto glutarate
Eg from aspartate, alanine ,glutamate

Question 27

What also inhibits gluconeogenesis

Answer 27

Build up of NADH eg in alcohol metabolism