Carbohydrate Metabolism Glucose Regulation and Formation

Question 1

Anabolism

Answer 1

energy-requiring synthesis of more complex products

Question 2

Catabolism

Answer 2

energy-yielding degradation of complex precursors

Question 3

Pancrease

Answer 3

cell: islet cells

metabolic function: releases insulin, glucagon, and numerous hormones

Question 4

Liver

Answer 4

Cell: hepatocyte
Metabolic function: maintains metabolic homeostasis by normalizing blood glucose and synthesizing and degrading glycogen, glucose, FAs and NAs, proteins, and ketone bodies

Question 5

Muscle

Answer 5

Cell: skeletal, smooth, and cardiac muscles

Metabolic function: utilizes glucose, FAs and AAs to fuel muscular activity

Question 6

Adipose Tissue

Answer 6

Cell: adipocyte

Metabolic function: stores energy via lipids very static

Question 7

Key regulators

Answer 7

insulin
glucagon
epinephrine (adrena medulla) 
glucose
ATP/AMP

Question 8

Major fates of glucose, four of them ***

Answer 8

source of ATP (pyruvate)
energy storage (glycogen)
molecular precursor (ECM and cell wall polysacchs.
structural backbone (ribose 5-phosphate)

Question 9

Major pathways of Carbohydrate metabolism

Answer 9

1. respiration –> forms ATP
2. Storage –> forms glycogen, glucose
3. Regenerative–> forms glucose (in liver)
4. Synthetic–> forms NAs, lipids and AAs

Question 10

Some metabolic pathways are exclusive which ones are they?

Answer 10

glycolysis and gluconeogenesis (liver)
glycogenesis and glycogenolysis
if one is occurring then the other cannot happen at the same time

Question 11

Aerobic catabolic pathways

Answer 11

Citric acid cycle, and ETC(oxidative phosphorylation)

also glycolysis

Question 12

anaerobic pathways

Answer 12

glycolysis

Question 13

Glycogen stores intracellular glucose

structures and where they are found

Answer 13

branched glucose homopolysaccharide
primary mechanism for intracellular energy storage
primarily found in the liver(10% dry weight) and muscle(2%)
necessary to maintain cellular osmolarity
forms large molecular complexes stored in granule organelles

Question 14

What starts the formation of glycogen and how many glucose molecules per chain in glycogen?

Answer 14

glycogenin

12 to 14 glucose residues

Question 15

Glycogen pathway

Answer 15

1.glucose-> glucose 6-phosphate
2.glucose 6-phosphate -> glucose 1- phosphate
3.glucose 1-phosphate -> uracil diphosphate glucose
4.uracil diphosphate glucose -> glycogen chain
5.glycogen chain -> glycogen particle
enzymes
1. hexokinase
2. phophoglucomutase
3. UDP-glucose pryphosphorylase
4. glycogen synthase (point of regulation)
5. glycogen branching enzyme

Question 16

Glycogenolysis

Answer 16

• Glycogen is broken down via glycogen phosphorylase and releases glucose-1-phosphate molecules
• once about 4 residues are left a transferase activity of debranching enzyme takes 3 of the four glucose molecules and puts them on the end of the chain.
• the one remaining glucose is cut via (alpha 1-6 glucosidase activity of debranching enzyme) and a free glucose is released.

Question 17

What are the two fates of the glucose 1-phosphate molecules from the glycogen?

Answer 17

1. phosphoglucomutase converts it to glucose 6-phosphate and off the glycolysis
2. ONLY in LIVER!! the Glucose 6-phosphate can enter the liver and go to the ER of the liver where the enzyme Glucose 6-phosphatase removes the phosphate and releases the free glucose to the blood.

Question 18

Glycogen regulation at glycogen synthase

Answer 18

-regulated by GSK3
-When glycogen synthase is phosphorylated it is inactive and is in the glycogen synthase b form
-When insulin is present is inactivates GSK3 and activates PP1 where glycogen synthase is activated.
–it is also activated by glucose-6-phosphate and glucose
inactivated by glucagon and epinephrine

Question 19

Glycogen phoshorylase regulation

Answer 19

phosphorylase b is inactivated and is not phosphorylated but glucagon and epinephrine activate phosphorylase and lead to it being phosphorylated and activated.

kind of the opposite of glycogen synthase regulation with being phosphorylated or not

Question 20

insulin signaling

Answer 20

activates glycogenesis via
IRS-1 which activates PI3K to activate PIP2 to activate PIP3 which in turn activates PKB which activates GSK3 to activate glycogen synthase
insulin activates GLUTs, hexokinase, and glycogen synthase

Question 21

Epinephrine and glucagon in the liver

Answer 21

increase glycogenolysis and gluconeogensis to increase blood glucose
glycolysis is decativated
**goal is to create more glucose 6-phosphate for the blood

Question 22

epinephrine in the muscles

Answer 22

increases glycogenolysis and glycolysis so that the liver can get more glucose to the blood

Question 23

phosphorylase allosteric regulators

Answer 23

glucose (slows glycogenolysis)

insulin ( increases glycogenolysis)

Question 24

gluconeogensis where is occurs and the process

Answer 24

occurs in all cells but mostly in the liver
lactate or pyruvate is converted to glucose
**energetically costly 4 ATP 2 GTP 2 NADH + H

Question 25

what is the cori cycle

Answer 25

Glycogen is broken down into lactate in muscle
lactate is released to blood and goes to liver
in the liver lactate is made into glucose via gluconeogensis (uses ATP). The glucose is then released into blood.

Question 26

What is the point of regulation for gluconeogenesis

Answer 26

the fructose 1,6-bisphosphatase -1 (FBPase-1) enzyme which converts fructose 1,6-bisphosphate to fructose 6-phosphate

Question 27

What energy substrates regulate the FBPase-1 and PFK-1 (glycolysis)

Answer 27

AMP inhibits it FBP-1 (poor energy substrates)
AMP and ADP activate PFK-1 (poor energy substrates)
citrate and ATP inactivate PFK-1 (energy rich substrates present)

Question 28

AMP kinase (AMPK) detects intracellular AMP
how?

Answer 28

regulating different organ systems by measuring the amount AMP present. This will change metabolic states in the body.
inhibits pancreas from releasing insulin, liver from FA synthesis and cholesterol synthesis, adipose tissue from FA synthesis and lipolysis.
basically tells the body hey we need energy get going.

Question 29

State of feeding, what happens in the pancreas, liver, adipose, and muscle?

Answer 29

pancreas: insulin release
liver: glycogen and FA production
adipose: lipid storage, glycolysis, and lipid production
muscle: glycolysis and glycogen production

Question 30

State of fasting, what happens in the pancreas, liver, adipose, and muscle?

Answer 30

pancreas: glucagon
liver: gluconeogenesis, glycogenolysis, ketone and glucose release
adipose: FA and glycerol release
Muscle: ketone metabolism, reduced glycolysis