Overview of Metabolism and Glycolysis

Question 1

What is metabolism?

Answer 1

Metabolism refers a series of chemical reactions in which the product of one reaction is the substrate for the next reaction.

Question 2

What is catabolism?

Answer 2

Catabolism refers to chemical reactions that result in the breakdown of more complex organic molecules into simpler substances, release energy (ATP) that is used to drive chemical reactions.

Question 3

What is anabolism?

Answer 3

Anabolism refers to chemical reactions in which simpler substances are combined to form more complex, new, molecules, usually require energy (ATP).

Question 4

What are NAD+ and NADP+?

Answer 4

Oxidizing agents

Question 5

What are NADH and NADPH?

Answer 5

Reducing agents

Question 6

What is the end product of glycolysis?

Answer 6

Pyruvate

Question 7

What is the importance of ketone bodies?

Answer 7

They are important in starvation as they allow for the operation of neurons

Question 8

What is glucose stored as in the body?

Answer 8

Glycogen

Question 9

What is fat stored as in the body?

Answer 9

Triacylglycerol

Question 10

What is the main molecule fed into the TCA cycle?

Answer 10

Acetyl Coenzyme A (AcCoA)

Question 11

What is the common cause of lactose intolerance?

Answer 11

Lactose intolerance occurs in most adults as a result of decreased lactase enzyme production

Question 12

In the fed state, what glucose pathways are occurring?

Answer 12

• Glycogenesis
• Pentose Phosphate Pathway
• Citric Acid Cycle
• Glycolysis

Question 13

What hormone is important in balancing the glucose level in the fed state?

Answer 13

Insulin

Question 14

In the fasting state, what glucose pathways are occurring?

Answer 14

• Glycogenolysis

- Gluconeogenesis

Question 15

What hormones are important for the glucose balance in the fasting state?

Answer 15

Glucagon and Epinephrine

Question 16

What is the main product of anaerobic respiration?

Answer 16

Lactate

Question 17

What is the main product of aerobic respiration?

Answer 17

Pyruvate

Question 18

What is glycogenesis?

Answer 18

Glycogenesis is the formation of glycogen from glucose (hyperglycemia – Insulin increased)

Question 19

What is glycogenolysis?

Answer 19

Glycogenolysis is the break down of glycogen to glucose-1- phosphate and glucose in the liver and in the muscles by the enzyme glycogen phosphorylase (hypoglycemia – glucagon increased)

Question 20

What is gluconeogenesis?

Answer 20

Gluconeogenesis results in the generation of glucose from non- carbohydrate carbon substrates such as pyruvate, lactate, glycerol, and glucogenic amino acids (hypoglycemia – glucagon increased)

Question 21

What is glycolysis?

Answer 21

Glycolysis (means “splitting sugars

Question 22

What is the sole form of metabolism in RBCs?

Answer 22

Glycolysis

Question 23

What metabolism is found in neurons?

Answer 23

Citric Acid Cycle

Question 24

What metabolism is found in adipose tissue?

Answer 24

Glycolysis but no TCA cycle

Question 25

What glucose receptor is found in liver cells?

Answer 25

GLUT 2

Question 26

What glucose receptor is found in skeletal muscle?

Answer 26

GLUT 4

Question 27

In the fed state in the liver cell what is the process on glucose?

Answer 27

Insulin binds -> Glucose transport into cell via GLUT2 -> Glucokinase converts glucose into G6P

Question 28

In the fasting state in the liver cell what is the process on glucose?

Answer 28

Glucagon binds -> G6Pase converts G6P into glucose -> Glucose transport out of cell via GLUT2

Question 29

In the contracting state of a muscle cell what is the process on glucose?

Answer 29

Glucose transported into the cell via GLUT4 -> Hexokinase converts it into G6P -> G6P is turned into ATP via glycolysis

Question 30

In the resting state of a muscle cell what is the process on glucose?

Answer 30

Glucose transported into the cell via GLUT4 -> Hexokinase converts it into G6P -> G6P is turned into glycogen

Question 31

What are the main 3 enzymes in glycolysis that have irreversible reactions?

Answer 31

Hexokinase/Glucokinase Phosphofructokinase Pyruvate Kinase

Question 32

What is allosteric regulation and what are the types?

Answer 32

Allosteric activation of inhibition of enzyme activity and it can be negative or positive

Question 33

What are the types of enzyme regulation?

Answer 33

- Allosteric - Phosphorylation - Induction/Suppression of enzyme synthesis

Question 34

What is the first step of glycolysis?

Answer 34

Conversion of glucose to G6P via hexokinase/glucokinase

Question 35

What is the importance of the glucose -> G6P reaction?

Answer 35

G6P cannot leave the cell and the reaction is irreversible as G6P is impermeable to the membrane as it is too polar

Question 36

Where is hexokinase found?

Answer 36

All cells

Question 37

Where is glucokinase found?

Answer 37

Liver and pancreas cells

Question 38

What regulates hexokinase?

Answer 38

It is allosterically inhibited by its product G6P.

Question 39

Where is glucokinase in its active form and inactive form?

Answer 39

Active: Cytosol Inactive: Nucleus

Question 40

What will promote glucokinase activity?

Answer 40

Glucose does so by promoting glucokinase translocation into the cytosol

Question 41

What will inhibit glucokinase activity?

Answer 41

Fructose-6-P will decrease glucokinase activity by promoting translocation into the nucleus

Question 42

What will increase glucokinase synthesis?

Answer 42

Insulin

Question 43

What has the higher glucose affinity, hexokinase or glucokinase?

Answer 43

Hexokinase

Question 44

What converts Fructose-6-Phosphate to Fructose-2,6-Bisphosphate?

Answer 44

PFK-2

Question 45

What converts Fructose-6-Phosphate to Fructose-1,6-Bisphosphate?

Answer 45

PFK-1

Question 46

What regulates the activity of PFK-1?

Answer 46

The activity of PFK-1 is regulated by Fructose-2,6-Bisphosphate, the product of PFK-2

Question 47

In the liver what is the effect of E and glucagon on PFK-2 and hepatic glycolysis?

Answer 47

Inhibitory

Question 48

How does glucagon inhibit PFK-2?

Answer 48

Glucagon stimulates the formation of cAMP. cAMP activates protein kinase A. Protein kinase A phosphorylates PFK-2 and inhibits the production of fructose 2,6-bisP.

Question 49

What is the effect of epinephrine and glucagon on hepatic glycolysis?

Answer 49

Inhibits

Question 50

What is the effect of epinephrine and glucagon on muscular and cardiac glycolysis?

Answer 50

Stimulates. Epinephrine (but not glucagon) activates heart and skeletal muscle PFK-2 by inhibiting the phosphatase activity

Question 51

What are some of the effects of glucagon and epinephrine?

Answer 51

- Inhibits PFK-2 which leads to decreased fructose-2,6-bisphosphate and decreases the activity of PFK-1 - Inhibits pyruvate kinase

Question 52

How is NAD+ regenerated?

Answer 52

- Lactate dehydrogenase (Cytosolic reaction) - Malate-aspartate shuttle (Cytosol and mitochondria) - Glycerol-phosphate shuttle (Cytosol and mitochondria)

Question 53

What is the function of lactate dehydrogenase?

Answer 53

LDH regulates pyruvate concentration by converting pyruvate to lactate and vice versa

Question 54

What is the reaction of LDH in skeletal muscle?

Answer 54

In skeletal muscle, the LDH5 M4 ISOZYME prefers to catalyze the conversion of pyruvate to lactate; this allows for high bursts of energy.

Question 55

What is the reaction of LDH in the cardiac muscle?

Answer 55

In heart muscle, the H4 ISOZYME prefers to catalyze the conversion of lactate to pyruvate; this allows for a sustained production of energy.

Question 56

What is the function of pyruvate dehydrogenase?

Answer 56

Pyruvate dehydrogenase is a enzyme complex that converts pyruvate and coenzyme A to acetyl-CoA

Question 57

How is pyruvate dehydrogenase regulated?

Answer 57

NADH and Ac-CoA, end-products of PDH reaction promote the phosphorylation and inhibition of this enzyme.

Question 58

What do anaerobic conditions favor?

Answer 58

Anaerobic conditions favor the formation of lactate

Question 59

What is the problem in Lactate Dehydrogenase Deficiency?

Answer 59

When lactate dehydrogenase levels are insufficient, the level of NAD+ becomes limiting during exercise and flux through the glyceraldehyde-3-P dehydrogenase reaction is inhibited.

Question 60

What is the problem in galactosemia?

Answer 60

Deficiency in: - galactokinase OR - galactose 1-phosphate uridyltransferase

Question 61

What enzyme is implicated in fructose intolerance?

Answer 61

Aldolase B