Pyruvate, gluconeogenesis, AA metabolism

Question 1

What is the Cori cycle?

Answer 1

Anaerobic respiration in animals

Question 2

Describe the Cori cycle

Answer 2

Glucose to pyruvate through glycolysis in the muscles
Pyruvate to lactate using lactate dehydrogenase (NADH–>NAD+)
Lactate transporter in the bloodstream to the liver
Lactate to pyruvate using lactate dehydrogenase
Pyruvate to glucose through gluconeogenesis

Question 3

Where does the link reaction occur?

Answer 3

In the mitochondrial matrix

Question 4

Describe link reaction

Answer 4

Pyruvate + CoA –> acetyl CoA + CO2 (NAD –> NADH)
Uses pyruvate dehydrogenase
Acetyl CoA enters Krebs cycle

Question 5

What inhibits pyruvate dehydrogenase complex?

Answer 5

Acetyl CoA and NADH allosterically

Acetyl CoA, NADH, ATP by phosphorylation

Question 6

What activates pyruvate dehydrogenase complex?

Answer 6

Pyruvate and insulin by de-phosphorylation

Question 7

Where does the tricarboxylic acid cycle occur?

Answer 7

Mitochondrial matrix

Question 8

Describe the Krebs cycle

Answer 8

Oxaloacetate + acetyl CoA –> citrate (citrate synthase)
Citrate –> isocitrate
Isocitrate –> alpha ketoglutarate + CO2 (isocitrate dehydrogenase) (NAD+–>NADH)
Alpha ketoglutarate –> succinyl CoA + CO2 (alpha ketoglutarate dehydrogenase) (NAD+–>NADH)
Succinyl CoA –> Succinate (GDP–>GTP–>ATP)
Succinate –> fumarate (FAD–>FADH2)
Fumarate –> Malate
Malate –> Oxaloacetate (NAD+–>NADH)

Question 9

How is citrate synthase activated?

Answer 9

AMP

Question 10

How is citrate synthase inhibited?

Answer 10

ATP

Question 11

How are isocitrate dehydrogenase and alpha ketoglutarate dehydrogenase activated?

Answer 11

Ca2+

Question 12

How are isocitrate dehydrogenase and alpha ketoglutarate dehydrogenase inhibited?

Answer 12

ATP and NADH

Question 13

Where does the electron transport chain take place?

Answer 13

Across the inner membrane of the mitochondria (between the matrix and the inter membrane space)

Question 14

Describe the electron transport chain

Answer 14

NADH and FADH2 donate electrons and protons.
Electrons donated to the ETC, they move down the ETC by a series of REDOX reactions.
The energy is used to pump protons against the concentration gradient across the membrane into the inter-membrane space.
Protons move down the electrochemical gradient by chemiosmosis through ATP synthase forming ATP.
Protons and electrons react with oxygen to form water to maintain the electrochemical gradient

Question 15

What is the phosphate pentose pathway?

Answer 15

Pathway that forms NADH

Question 16

What is the product of phosphate pentose pathway used for?

Answer 16

NADH is used in reductive biosynthetic pathways e.g. fatty acid synthesis

Question 17

Where does the phosphate pentose pathway occur?

Answer 17

In the cytosol

Question 18

What enzyme is used in the 1st step of the phosphate pentose pathway?

Answer 18

Glucose-6-phosphatase dehydrogenase

Question 19

What is gluconeogenesis?

Answer 19

The formation of glucose in the liver from non-carbohydrate substrates

Question 20

What are the substrates for gluconeogenesis?

Answer 20

Pyruvate (from alanine or lactate) or dihydroxyacetone-p from glycerol

Question 21

How is pyruvate formed from alanine or lactate?

Answer 21

Alanine is transaminated by alanine aminotransferase to pyruvate.
Lactate converted to pyruvate using lactate dehydrogenase

Question 22

Describe gluconeogenesis?

Answer 22

They enter as pyruvate.
Pyruvate is converted into phosphenolpyruvate in 2 steps catalysed by pyruvate carboxylase and PEP carboxykinase.
Glycolysis is then reversed to form glucose

Question 23

What enzymes are used in the irreversible steps of gluconeogenesis?

Answer 23

Pyruvate carboxylase and PEP carboxykinase used to convert pyruvate into phosphenolpyruvate
Fructose-1,6-bisphosphatase used to convert fructose-1,6-bisp to fructose-6p.
Glucose-6-phosphatase used to convert glucose-6-p into glucose

Question 24

How is gluconeogenesis activated?

Answer 24

Glucagon

Question 25

What activates pyruvate carboxylase?

Answer 25

Acetyl CoA

Question 26

What are essential amino acids?

Answer 26

Amino acids essential for survival that our bodies cannot make

Question 27

What are non-essential amino acids?

Answer 27

Needed for survival but our bodies can make them

Question 28

What is a keto-acid?

Answer 28

AA without amino group

Question 29

What is transamination?

Answer 29

The formation of an AA from a ketoacid by another AA donating the amino group

Question 30

What enzymes are used in transamination?

Answer 30

Aminotransferase

Question 31

What is phenylketonuria?

Answer 31

Lack of phenylalanine hydrolase.
Phenylalanine cannot be converted to tyrosine.
Phenylalanine saturates the blood brain barrier so other molecules cannot cross

Question 32

Describe the process of AA catabolism

Answer 32

AA donates amino group to convert alpha-ketoglutarate into glutamate.
Glutamate can be deaminated.
The ketoacids can enter TCA cycle

Question 33

What are glycolic ketoacids?

Answer 33

Enter TCA cycle

Question 34

What are ketogenic ketoacids?

Answer 34

Enter ketone synthesis

Question 35

What is the fate of serine after AA catabolism?

Answer 35

Transaminated to form the veto from of 3-phosphoglycerate which can enter glycolysis to prom pyruvate.

Question 36

What is the fate of glutamate after AA catabolism?

Answer 36

Transaminated into alpha-ketoglutarate which can enter TCA cycle