Lecture 6 - Carbohydrates Continued

Question 1

What are the three fates of glucose in the cell

Answer 1

enters glycogenesis for energy storage
enters glycolysis for energy production
enters hexose monophosphate shunt to generate precursors for biogenesis

Question 1

What are the 6 steps in carbohydrate metabolism

Answer 1

glycogenesis, glycogenolysis, glycolysis, hexose mono sulphate shunt, Krebs cycle, gluconeogenesis

Question 2

Where does glycogenesis occur

Answer 2

liver and muscle

Question 3

What turns glucose from the blood into glucose-6-phosphate

Answer 3

phosphorylation of glucose

Question 4

What turns glucose-6-phosphate into glucose-1-phosphate

Answer 4

hexokinase

Question 5

What turns glucose-1-phosphate into glycogen

Answer 5

glycogen synthase

Question 6

What is glycogenin

Answer 6

an enzyme that serves as a scaffold on which to attach glucose molecules to build glycogen

Question 7

What occurs in glycogenolysis

Answer 7

glycogen is broken down back to glucose-1-phosphate, which is further broken back down to glucose-6-phosphate, broken down to fructose-6-phosphate, and sent to glycolysis

Question 8

What breaks glycogen down into glucose-1-phosohate

Answer 8

glycogen phosphorylase

Question 9

Where is glucose-6-phosphate broken back down to glucose (there is only one place it does this)

Answer 9

the liver

Question 10

What does insulin stimulate

Answer 10

glucose uptake from food to cells (lowers blood sugar)

Question 11

What does glucagon stimulate

Answer 11

glycogen breakdown back to glucose (increases blood sugar)

Question 12

What is the first conversion in glycolysis and what enzyme carries it out

Answer 12

fructose-6-phosphate into fructose-1,6-phosphate
- done via phosphofructokinase
*this is irreversible

Question 13

What is the net yield from glycolysis

Answer 13

2 NADH and 2 ATP

Question 14

What are the two anaerobic pathways of glucose breakdown

Answer 14

lactic acid production and ethanol

Question 15

What is lactic acid production

Answer 15

occurs in muscle during prolonged exercise and in RBCs
pyruvate is converted into lactate
regenerates NAD+, allowing cycling of glycolysis

Question 16

What is the net of ATP when converting glucose to lactic acid

Answer 16

2 ATP

Question 17

What is the ethanol production pathway

Answer 17

doesn’t happen in the body
basis of fermentation for making beer and wine
yeast breaks down pyruvate into CO2 and ethanol
regenerates NAD+, allowing cycling of glycolysis

Question 18

What is the Cori cycle

Answer 18

no oxygen is available during exercise, so lactate is produced, which is then transports back to the liver where gluconeogenesis allows for conversion of pyruvate back to glucose

Question 19

What is the net ATP in the Cori cycle

Answer 19

for every 2 glucose, 6 ATP are formed

Question 20

What is the function of the hexose monophosphate shunt

Answer 20

important for NADPH production and ribose synthesis

Question 21

Where does the hexose monophosphate shunt function

Answer 21

in the cytoplasm of the cell

Question 22

What is the role of glucose-6-phosphate dehydrogenase in the hexose monophosphate shunt

Answer 22

convert G6P into 6-PG

Question 23

What is the importance of the oxidative phase of hexose monophosphate shunt

Answer 23

biosynthesis of fatty acids and role in antioxidant production

Question 24

What is the importance of the non-oxidative phase of hexose monophosphate shunt

Answer 24

biosynthesis of RNA/DNA

Question 25

What vitamins make up the pyruvate dehydrogenase complex

Answer 25

thiamine, niacin, riboflavin, and pantothenic acid

Question 26

What is the net production in pyruvate dehydrogenase

Answer 26

~6 ATP (3 per 1 NADH)
2 x [1 NADH/pyruvate]

Question 27

What is the net production in the Krebs cycle per 1 acetyl CoA

Answer 27

3 NADH, 1 FADH2, 1 GTP (~12 ATP)

Question 28

What is the total net energy from the breakdown of glucose

Answer 28

38 ATP
(~10 from glycolysis)
(~6 from pyruvate dehydrogenation because 2 pyruvate)
(~24 from Krebs cycle because 2 acetyl CoA)

Question 29

What is gluconeogenesis

Answer 29

pathway that is active when glucose is needed by the body
very active in liver, but can also happen in kidneys

Question 30

Where can gluconeogenesis NOT occur

Answer 30

in the muscle and adipose tissue

Question 31

What is meant by the term integrated metabolism

Answer 31

thinking beyond just carbs, the collective metabolism of all nutrients