Week 3 FLO

Question 1

What are the 3 regulating steps of glycolysis?

Answer 1

1. Hexokinse 2. Phosphofructokinase 3. Pyruvate kinase

Question 2

What regulates Hexokinase?

Answer 2

its downstream product, glucose-6-phosphate (Note: this is NOT true of glucokinase in the liver which is regulated by an inhibitory enzyme, whose affinity is increased by fructose 6-phosphate and decreased by fructose 1-phosphate)

Question 3

What regulates PFK?

Answer 3

Activators: AMP and fructose-2,6-bisphosphate ; Inactivated by: ATP

Question 4

What regulates Pyruvate Kinase?

Answer 4

Activators: Fructose-1,6-Bisphosphate ; Inactivated by: ATP, alanine, and phosphorylation which occurs when there are high levels of glucagon

Question 5

What is the role of phsophorylation in the metabolism of glucose?

Answer 5

Traps glucose inside the cell in the case of Hexokinase, committting it to further metabolism inside the cell

Question 6

Compare Hexokinases I-III to IV ( or glucokinase)

Answer 6

Found in normal cells vs liver. Glucokinase is NOT inhibited by glucose-6-phosphate, but functions as a glucose sensor determining the threshold for insulin decretion

Question 7

Describe the 4 major enzymes of glycogen metabolism

Answer 7

1. Glycogen synthase makes glycogen 2. Glycogen phosphorylase breaks down glycogen to glucose 1-phosphate 3. Phosphoglucomutase converts Glucose 1 phosphate to Glucose 6 phosphate 4. UDP glucose phosphoylase yses 1 UTP and glucose 1-phosphate to form UDP glucose and PPi

Question 8

What does glycogen synthase do?

Answer 8

Converts UDP glucose to glycogen

Question 9

What does glycogen phosphorylase do?

Answer 9

Converts glycogen to Glucose-1-phosphate

Question 10

What does UDP-glucose phosphorylase do?

Answer 10

Converts glucose-1phosphate to UDP glucose

Question 11

What does phosphoglucomutase do?

Answer 11

Converts Glucose-1-phosphate to glucose-6-phosphate

Question 12

Glycogen phosphorylase must be activated by what?

Answer 12

glycogen phosphorylase kinase

Question 13

How is glycogen phosphorylase kinase activated?

Answer 13

When glucagon (liver) or epinephine (liver and muscle) binds to its corresponding GPCR, causing a signal cascade activating adenylyl cyclase, producing cAMP from ATP. cAMP then activates the regulatory units of cAMP-dependent PKA, which releases the 2 catalytic units which become active and phosphorylate glycogen phosphorylase kinase b, transforming it into its active form, glycogen phosphorylase b

Question 14

What is epinephrine’s action in muscle?

Answer 14

Binds beta-andrenergic receptors to stimulate glucose release

Question 15

Describe the role of fatty acids for exercising skeletal muscle

Answer 15

As exercise time increases, the percentage of FFAs used as source of ATP increases with respect to glucose and non-blood borne muscle glycogen and intracellular fats and proteins

Question 16

How are FFA levels increased during exercise?

Answer 16

Hormone sensitive lipase causes TAGs to be broken down into FFAs by adipocytes

Question 17

FFA are broken down by what process?

Answer 17

Beta-oxidation

Question 18

How is catabolism of FFA perfromed?

Answer 18

Beta-oxidation occurs in 4 steps which shortens the chains by 2 carbons- these 4 steps repeear n/2-1 times where n is the number of carbons

Question 19

Where is catabolism of FFA performed?

Answer 19

in the mitochondria

Question 20

Each cycle of 4 steps of FFA breakdown produces what?

Answer 20

FADH2, NADH, and acetyl CoA (last cycle produces 2 Acetly CoA)

Question 21

What is the net yield of palmitate FFA?

Answer 21

129 ATP (2 used as investment, 131 total)

Question 22

Where are BCAA broken down?

Answer 22

In skeletal muscle

Question 23

What types of BCAA are there?

Answer 23

1. glucogenic, 2. ketogenic 3. both

Question 24

What are the 3 BCAA?

Answer 24

1. Valine (glucogenic) 2. Leucine (ketogenic) 3. Isoleucine (both)

Question 25

What is the significance of the 3 types of BCAA?

Answer 25

glucogenic produce glycolysis intermediates vs ketone intermediates

Question 26

What is the role of epinephrine on regulation of biochemical pathways in skeletal muscle?

Answer 26

Signals the need for glycogen to be degraded to provide energy for exercising muscle

Question 27

What type of receptor foes E bind?

Answer 27

GPCR

Question 28

What is the mechanism of epinephine cascade?

Answer 28

Bind GPCR, activates adenylyl cyclase, binds PKA, synthesizes cAM which binds to PKA regulatory subunit dimer which releases individual active subunits, several enzymes of glycogen metabolism are then phosphorylated by PKA

Question 29

What is insulin’s mechanism in skeletal muscle?

Answer 29

Activates the phosphodiesterase that degrades cAMP, thus opposing effects of glucagon and E. Also stimulates protein phosphatase-1 action

Question 30

What is the role of Calcium in regulation of biochemical pathways in skeletal muscle?

Answer 30

Calsium is released from the sarcoplasmic reticulum. Calcium then binds calmodulin subunit of phosphorylase kinse and activates it without phosphorylation. Phosphorylase kinase can then activate glycogen phosphorylase, causing glycogen degradation and glucose release!