Integration

Question 1

name 3 possible pathways for glucose 6-phosphate

Answer 1

it can become glucose 1-phosphate for glycogen, fructose 6-phosphate for pyruvate, or 6-phosphogluconate for ribose 5-phosphate

Question 2

name two origins of glycerol 3-phosphate

Answer 2

glycerol can come from adipocytes (only in liver), and glucose can come from all organs via glycolysis (DHAP)

Question 3

name 3 pathways where glycerol 3-phosphate can go

Answer 3

only in the liver it can go onto gluconeogenesis. In all organs via glycolysis (DHAP) it can be used in G3P shuttle that gives electrons to the ETC. and in the liver and adipocytes it can be used in triglycerides and phospholipids

Question 4

name 3 sources for pyruvate

Answer 4

it can come from alanine mainly in the liver. it can come from glucose in all organs via glycolysis. or it can come from other amino acids

Question 5

name 4 pathways pyruvate might go

Answer 5

it can be converted to alanine in muscle. it can go on to gluconeogenesis mostly in the liver during fasting. It can go onto the krebs cycle and ETC. or it can go into fatty acids in the liver and adipocytes

Question 6

name 3 sources of acetyl CoA

Answer 6

glycolysis/beta oxidation of fatty acids (in liver, muscle, heart, and adipose tissues). it can come from ketogenic amino acids (both fed and fasting conditions). and ketone bodies (all organs except the liver)

Question 7

name 3 pathways acetyl CoA might go

Answer 7

it can form ketone bodies only in the liver during fasting. it can go on to the krebs cycle and ETC. and it can form fatty acids in the liver and adipocytes in the fed state.

Question 8

name activators and inhibitors of PFK

Answer 8

activated by Fructose 2,6-BP, activated by AMP. It is inhibited by ATP and citrate

Question 9

name activators and inhibitors of fructose 1,6-biphosphatase

Answer 9

activated by citrate. it is inhibited by AMP and fructose 2,6-BP

Question 10

name activators and inhibitors of acetyl CoA carboxylase

Answer 10

activated by citrate, inhibited by palmitoyl CoA

Question 11

name inhibitor of carnitine acyltransferase I

Answer 11

inhibited by malonyl CoA

Question 12

name the biochemical actions of insulin

Answer 12

+cell permeability to glucose (in muscle and adipose). +glycolysis. +glycogen synthesis. +triacyglycerol synthesis. -gluconeogenesis. -lipolysis. -protein degradation. +protein, DNA, and RNA synthesis.

Question 13

name the physiological actions of insulin

Answer 13

signals fed state. -blood glucose level. +fuel storage. +cell growth and differentiation.

Question 14

name the biochemical actions of glucagon

Answer 14

+cAMP level in liver and adipose. +glycogenolysis. -Glycogen synthesis. +triacyglycerol hydrolysis. +Gluconeogenesis. -Glycolysis

Question 15

name the physiological actions of glucagon

Answer 15

+glucose released from liver. +blood glucose level

Question 16

name the biochemical actions of epinephrine

Answer 16

+cAMP level in muscle. +triacyglycerol mobilization. +glycogenolysis. -glycogen synthesis

Question 17

name the physiological actions of epinephrine

Answer 17

+glucose release from liver. +glucose use by muscle. +blood glucose level.

Question 18

describe PFK-2 in liver

Answer 18

this enzyme makes F-2,6-BP. the main allosteric activator of PFK-1 (glycolysis). and the main inhibitor of fructose 1,6-biphosphatase (gluconeogenesis). PFK-2 is inhibited by protein kinase A (glucagon and epinephrine) and converted into fructose 2,6bisphosphatase. the result is a destruction of F-2,6-BP, activating gluconeogenesis and inhibiting glycolysis.

Question 19

name the enzymes in the liver necessary for gluconeogenesis

Answer 19

(pyruvate carboxylase, PEP carboxykinase and fructose 1,6-bisphosphatase.

Question 20

describe glucose-6-phosphatase in the liver

Answer 20

this enzyme is responsible for releasing glucose into circulation. glucose 6-phosphate is produced by glycogen degradation or gluconeogenesis. glucose-6-phosphate also blocks hexokinase

Question 21

describe pyruvate kinase in the liver

Answer 21

this isozyme is inhibited by protein kinase A (glucagon and epinephrine). when gluconeogenesis is operating, the inhibition of pyruvate kinase prevents PEP utilization. pushing gluconeogenesis

Question 22

describe glycerol kinase in the liver

Answer 22

this enzyme is required to convert glycerol produced during lipolysis in adipose into glycerol-phosphate. glycerol phosphate is then converted to DHAP and used in gluconeogenesis

Question 23

describe GLUT 2 in the liver

Answer 23

this glucose carrier transports glucose at a rate proportional to its concentration in circulation. it provides glucose for storage as glycogen for future use or for fatty acid synthesis

Question 24

describe glucokinase (hexokinase IV) in the liver

Answer 24

the Km of this enzyme for glucose is about 50-fold higher than that of other hexokinases. furthermore, the enzyme is not blocked by its product

Question 25

describe ketone bodies in the liver

Answer 25

the combination of gluconeogenesis (depleting OA) and fatty acid oxidation causes acetyl CoA to accumulate. In order to continue oxidizing fatty acids to provide energy for gluconeogenesis, acetyl CoA is converted into ketone bodies which are exported to other tissues

Question 26

describe the urea cycle in the liver

Answer 26

the liver is the only organ capable of converting free ammonia into urea

Question 27

describe GLUT4 in muscle

Answer 27

this glucose carrier stimulates glucose uptake from circulation only when insulin is released. it provides glucose for storage as glycogen for future use but prevents muscle from competing with brain for glucose during fasting

Question 28

describe absence of glucose-6-phosphatase in muscle

Answer 28

this enzyme is absent in muscle and its absence prevents glucose from being released back in circulation. thus, under stress, the muscle maintains a constant supply of glucose

Question 29

describe pyruvate kinase in muscle

Answer 29

contrary to what happens in the liver, this isozyme is insensitive to phosphorylation by protein kinase A (epinephrine). in contrast with the liver, PKA triggers glycogen degradation and inhibits glycogen synthesis but does not affect glycolysis

Question 30

describe GLUT4 in adipose tissue

Answer 30

this glucose carrier stimulates glucose uptake from circulation only when insulin is released. it provides glucose needed to make glycerol-P for storage of fatty acids. glycolysis is the only source of glycerol-P

Question 31

describe absence of glycerol kinase in adipose tissue

Answer 31

this enzyme is absent in adipose tissue. since primary function of this organ is to store fat, it needs a continuous supply of glycerol-P during the fed state. the only source of glycerol phosphate is DHAP from glycolysis. GLUT4 provides all the glucose needed for fat storage

Question 32

describe hormone-sensitive lipase in adipose tissue

Answer 32

in the absence of insulin, cAMP increases and protein kinase A phosphorylates this hormone, releasing fatty acids into circulation (albumin)

Question 33

what do sulfonylureas do

Answer 33

they treat type II diabetes by increasing insulin

Question 34

describe how asprosin works to treat diabetes

Answer 34

discovered as a fasting-induced glucogenic protein hormone. asprosin induces hepatic glucose production by using cAMP as a second messenger. Asprosin is pathalogically elevated with human and mouse insulin resistance. reduction of asprosin protects against metabolic syndrome associated hyperinsulinism