Glycolysis and Gluconeogenesis

Question 1

Where does glycolysis take place?

Answer 1

Outside the cell in the cytosol

Question 2

What is the end product of one cycle of glycolysis?

Answer 2

2 pyruvate molecules, 2 ATP

Question 3

What occurs in stage 1 of glycolysis?

Answer 3

Glucose is converted to fructose-1,6-bisphosphate and two ATP are used

Question 4

What occurs in stage 2 of glycolysis?

Answer 4

Two molecules consisting of three carbons each are created: Dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate (GAP)

Question 5

What occurs in stage 3 of glycolysis?

Answer 5

DHAP and GAP are each converted to one molecule of pyruvate, also producing two ATP and one NADH each

Question 6

How many times does each stage of glycolysis occur?

Answer 6

Stages 1 and 2 occur once, stage 3 occurs twice

Question 7

What is the net yield of one cycle of glycolysis?

Answer 7

2 ATP (Four are created in stage 3 but two were used in stage 1) + 2 NADH + 2 H+

Question 8

What enzyme performs first regulated step in glycolysis?

Answer 8

Hexokinase

Question 9

What enzyme commits the rest of glycolysis to occur?

Answer 9

Phosphofructokinase

Question 10

Which enzyme is the last regulated step in glycolysis and causes the formation of pyruvate?

Answer 10

Pyruvate kinase

Question 11

Which enzyme is NOT a part of glycolysis but modifies pyruvate for the TCA cycle?

Answer 11

Pyruvate dehydrogenase

Question 12

What does pyruvate create in the presence of oxygen?

Answer 12

Acetyl CoA, in mitochondria

Question 13

What does pyruvate create in the absence of oxygen?

Answer 13

Lactate, in cytoplasm

Question 14

What two things are needed for gluconeogenesis to occur?

Answer 14

An energy source from the metabolism of fat and a source of carbons

Question 15

Under what conditions is gluconeogenesis stimulated to occur?

Answer 15

Times of low carbohydrate, fasting or starvation

Question 16

Where does gluconeogenesis primarily occur and what enzyme allows the process to release glucose into the blood stream?

Answer 16

90% in the liver (10% in kidney), has glucose 6-phosphatase

Question 17

Where is glucose 6-phosphatase located?

Answer 17

Membrane of rough ER

Question 18

How does glucose 6-phosphate become glucose at target cells?

Answer 18

In the liver G6-P is transported into the lumen of the rough ER through G6-phosphatase (Which dephosphorylates G6-P into glucose). Then the glucose is enclosed in vesicles, released from the liver into the blood, and travels to energy-poor cells (BRAIN).

Question 19

Which 5 substrates can be used for gluconeogenesis?

Answer 19

Lactate (From anaerobic glycolysis such as in RBCs or muscle), glucogenic amino acids (From muscle in diet), glycerol (From triglycerides), proprionate (From ruminant VFAs), and TCA intermediates

Question 20

What type of pH would inhibit gluconeogenesis and the TCA cycle?

Answer 20

Very low pH

Question 21

What is NOT a substrate for gluconeogenesis?

Answer 21

Acetyl CoA

Question 22

What does glycerol form after it loses its fatty acid chains and is phosphorylated and undergone dehydrogenase activity?

Answer 22

DHAP (Dihydroxyacetone phosphate)

Question 23

How are fatty acids converted to Acetyl CoA?

Answer 23

Through beta oxidation

Question 24

What steps near the beginning of gluconeogenesis are not present in glycolysis?

Answer 24

Conversion of pyruvate to oxaloacetate (OAA) via pyruvate carboxylase and conversaion of OAA to PEP by PEP carboxykinase

Question 25

Where do lactate and some AAs enter gluconeogenesis?

Answer 25

At the level of pyruvate

Question 26

Where do other AAs enter gluconeogenesis?

Answer 26

At the level of oxaloacetate

Question 27

Where does glycerol enter gluconeogenesis?

Answer 27

At the level of DHAP (As DHAP)

Question 28

How are glycolysis and gluconeogensis different in terms of net energy?

Answer 28

Glycolysis produces energy whereas gluconeogenesis consumes energy

Question 29

How many molecules of energy are needed to perform gluconeogenesis?

Answer 29

6, 4 ATP and 2 GTP

Question 30

When SHOULDN’T glycolysis be occurring?

Answer 30

When energy stores are high

Question 31

What happens when energy stores are low?

Answer 31

Glucose should be rapidly degraded

Question 32

How does glucose 6-phosphate regulate glycolysis/gluconeogenesis?

Answer 32

Inhibits hexokinase, stimulate glucose 6-phosphatase

Question 33

How is phosphofructokinase bypassed through gluconeogenesis?

Answer 33

By fructose-2,6-bisphosphatase

Question 34

How is pyruvate kinase bypassed through gluconeogenesis?

Answer 34

Pyruvate carboxylase and PEP carboxykinase