Gluconeogenesis

Question 1

What is the synthesis of glucose de novo from non carbohydrate precursors?

Answer 1

Gluconeogenesis

Question 2

Where does gluconeogenesis occur?

Answer 2

Liver and kidney

Question 3

When is gluconeogenesis particularly important?

Answer 3

During times of fasting

Question 4

What is the bypass reaction 1a (1) of GNG?

Answer 4

Pyruvate to oxaloacetate
Enzyme- pyruvate carboxylase
Coenzyme-biotin (helps add CO2)
ATP—>ADP

Question 5

What is bypass reaction 1b (2) in GNG?

Answer 5

Oxaloacetate to phosphoenolpyruvate
Enzyme: phosphoenolpyruvate carboxykinase
GTP—>GDP
Removed CO2 from oxaloacetate

Question 6

What happens in reactions 3 to 8 of GNG?

Answer 6

Phosphoenolpyruvate is a glycolytic intermediate and can continue through the reversible reactions of glycolysis.

Question 7

What do we reach at step 9 GNG?

Answer 7

Another irreversible reaction is reached. We reach fructose 1,6-bisphosphate

Question 8

What is the GNG bypass reaction 3?

Answer 8

Fructose 1,6-bisphosphate to fructose 6-phosphate
Enzyme: Fructose 1,6-bisphosphatase hydrolyzes
No ATP generated,

Question 9

What is bypass reaction 4 of GNG?

Answer 9

Glucose 6-phosphate to glucose
Enzyme: glucose-6 phosphatase hydrolyzes
No ATP generated

Question 10

What are the GNG precursors?

Answer 10

Lactate, glycerol, glucogenic AA (alanine)

Question 11

_____________,produced as a byproduct of anaerobic metabolism in muscles, can be converted into pyruvate and then used for gluconeogenesis

Answer 11

Lactate (Cori cycle)

Question 12

Certain ____________can be converted into pyruvate or intermediates in the citric acid cycle and enter gluconeogenesis.

Answer 12

Amino acids, such as alanine and glutamine

Question 13

____________released from triglycerides during fat breakdown (lipolysis), can be converted into dihydroxyacetone phosphate (DHAP), an intermediate in glycolysis and gluconeogenesis.

Answer 13

Glycerol

Question 14

_________________is
a glycolytic intermediate and can continue through the
reversible reactions of glycolysis

Answer 14

Phosphoenolpyruvate (PEP)

Question 15

In the absence of sufficient oxygen (as in intense exercise), pyruvate is converted into lactate in what cells? What is the cycle involving lactate?

Answer 15

Muscle cells, then the lactate continues to the liver. The Cori cycle

Question 16

What does pyruvate being converted into lactate in muscle cells help produce?

Answer 16

NAD+, which allows glycolysis to continue anaerobically, and produce more ATP.

Question 17

Where does glycerol from triacylglycerol catabolism enter GNG?

Answer 17

Step 7 after its conversion into dihydroxyacetone phosphate (DHAP)

Question 18

Where do both glycolysis and gluconeogenesis take place?

Answer 18

In the cytoplasm of the liver cell

Question 19

Which enzyme catalyzes the conversion of glycerol to DHAP?

Answer 19

glycerol kinase

Question 20

Amino acids that can serve as a substrate for
gluconeogenesis are called _______________.

Answer 20

glucogenic amino acids

Question 21

All amino acids except what 2 can be glucogenic?

Answer 21

Leucine and lysine

Question 22

What are the 2 fates of these glucogenic AAs?

Answer 22

Either be converted directly into pyruvate or into a citric acid cycle
intermediate

Question 23

Glucogenic amino acids that are particularly important are _____________ and ________________.

Answer 23

Alanine and glutamine

Question 24

Alanine can be converted to _____________, using what enzyme? And what coenzyme is required?

Answer 24

Pyruvate
Enzyme: Alanine transaminase (ALT)
Co-enzyme: pyridoxal phosphate (PLP) (derived from B6)
Transamination reaction (transfer of an amino group)

Question 25

Transamination involves transferring an _______ group from an amino acid to an alpha __________

Answer 25

amine, ketoacid

Question 26

Where does gluconeogenesis begin?

Answer 26

The mitochondria

Question 27

Alanine is converted to pyruvate inside the _____________

Answer 27

Mitochondria

Question 28

Lactate is converted to pyruvate in the _______________. Pyruvate is immediately shuttled into the _______________

Answer 28

cytosol/mitochondra

Question 29

__________________cannot cross the inner mitochondrial membrane to get back into the cytosol to feed into gluconeogenesis

Answer 29

oxaloacetate

Question 30

The malate shuttle is used when the starting substrate is ______________.

Answer 30

Alanine (or any other glucogenic AA)

Question 31

What is converted into malate in the malate shuttle?

Answer 31

Oxaloacetate

Question 32

Once oxaloacetate is converted to malate, malate crosses the inner ____________ _____________. Then once in the ______________ malate is converted back into oxaloacetate. Oxaloacetate is then converted to ________________ and continues on to what pathway?

Answer 32

mitochondrial membrane/ cytosol / phosophoenolpyruvate (PEP) gluconeogenesis

Question 33

Lactate is converted to pyruvate in the ______________. Pyruvate enters the ______________ & is converted to ________________. Oxaloacetate is converted to _________________ and is then shuttled out to continue with gluconeogenesis.

Answer 33

cytosol / mitochondria / oxaloacetate / phosphoenolpyruvate (PEP)