BSI Lecture 34 Glycogen Metabolism/Gluconeogenesis Flashcards
______ is the storage form of glucose.
Glycogen
T or F? Glycogen is a monosaccharide.
False, it’s a polysaccharide
Where is glycogen primarily stored?
Liver and muscle cells
Stores are limited; once stores are maximized, no more glucose can be stored as glycogen. Which process is this in?
Glycogenesis
T or F? Glycogenesis only occurs in the liver.
False, it occurs in both the liver and the muscle cells
What is the rate-limiting enzyme for Glycogenesis?
Glycogen synthase
What is the purpose of Glycogenesis?
To store glycogen in the liver and muscle
In _____, glucose is added to the glycogen tree.
Glycogenesis
Glucose-1-phosphate → uridine diphosphate glucose. What enzyme does this?
Glycogen synthase
What is the purpose of glycogenolysis?
To break down glycogen stores.
What happens to glucose-6-phosphate when there is enough energy in the cell?
It will be converted to glucose-1-phosphate then to uridine diphosphate glucose then it is added to glycogen tree.
What enzyme does this? Glycogen → glucose-1-phosphate
Glycogen phosphorylase (cleaves glucose from the glycogen tree)
Glycogenolysis: Glucose-1-phosphate → glucose-6-phosphate. What happens in skeletal muscle?
There no phosphatase enzyme so glucose-6-phosphate cannot leave the cell; therefore, glucose-6-phosphate enters glycolytic pathway.
T or F? The muscle cell breaks down glycogen to use for itself.
True
Glycogenolysis: Glucose-1-phosphate → glucose-6-phosphate. What happens in the liver?
Glucose-6-phosphate → glucose (glucose-6-phosphatase)
The glucose is released into the blood for use by other tissues (primarily the brain).
T or F? The liver breaks down glycogen to use for itself.
False
Glucose is formed from non-carbohydrate sources in which process?
Gluconeogenesis
Glucose is formed from non-carbohydrate sources, what are they?
- Certain Amino Acids
- Lactate
- Glycerol
- Krebs Cycle intermediates
T or F? Gluconeogenesis occurs in the liver and muscles.
False, liver and kidneys
Lactate and certain amino acids can be converted into _____, which is then converted into glucose via “reverse” glycolysis.
Pyruvate
_______ can be converted into glyceraldehydes-3-phosphate, which then can be converted into glucose via “reverse” glycolysis.
Glycerol
What enzyme regulates glycogenolysis?
Glycogen phosphorylase
T or F? (+) AMP, glucagon (stimulates glycogenolysis in the liver, but not in muscle), epinephrine. This regulates glycogenolysis.
True
(-) ATP, insulin regulates which process?
Glycogenolysis
What regulates glycogenesis?
- Rate limiting enzyme:
a. Glycogen synthase - (+) insulin
- (-) glucagon, epinephrine
(+)Glucagon and (-)insulin are regulators of ________
Gluconeogenesis
T or F? Insulin is required for the brain to take up glucose and use it for energy
False, it is not required
________ does not inhibit glycolysis in the brain
Glucagon
in times of high concentration of glucagon and low concentration of insulin (such as during a state of starvation), the brain is able to take up and utilize the glucose that is being dumped out into the blood by the liver via ________ and ________.
Gluconeogenesis; glycogenolysis
What is the rate-limiting enzyme for Glycogenesis?
Glycogen synthase
Why is it important for the liver to “dump” glucose into the bloodstream?
It is for the brain to use because it is primarily what the brain use for energy.
One of the roles of the liver is to _____ blood ________ levels for the brain.
maintain; glucose
What happens to insulin and glucagon levels at 4 am?
Insulin drops and glucagon rises
What is taking place in the body to maintain the blood/glucose level?
Glycogenolysis maintains blood/sugar
Glyconeogenesis maintains stores
What does glucagon do to glycolysis?
Inhibits
What tissue is Glucose-6-phosphatase expressed in?
Liver
“Reverse glycolysis” is _______________
Gluconeogenesis
_______ is a Krebs Cycle intermediate that can be used for Gluconeogenesis.
Oxaloacetate (OAA)
What two parts of the body can use Gluconeogenesis?
Liver and kidneys
In times of starvation, the liver will produce glucose for the _______ and _____ _______ _____.
Brain; red blood cells
Low energy status would ______ glycogenolysis while high energy status would ______ it.
Stimulate; inhibit
Glycogenolysis: In general, Glucagon will stimulate _____ pathways.
Catabolic
Glycogenolysis: Insulin will stimulate ______ pathways.
Anabolic
T or F? Glycogenesis is an anabolic type reaction.
True
T or F? Glucagon works in muscle tissue only.
False, liver
