Biochemistry Flashcards
What is glycogenesis?
Synthesis of glycogen from glucose
What is glycogenolysis?
The breakdown of glycogen to form glucose
What is gluconeogenesis?
De novo synthesis of glucose from metabolic precursors
What is glycogen?
The main storage form of glucose in liver and muscle cells
What are the 2 forms of glycogen?
Liver glycogen
Muscle glycogen
What is the function of liver glycogen?
To maintain blood glucose levels for red blood cells and the brain in-between meals
What is the function of muscle glycogen?
To provide energy via glycolysis and the TCA during bursts of physical activity
What is the structure of glycogen?
Joined by a-1,4 glycosidic links and branched are created with a-1,6 glycosidic links
What is the first step of glycogenesis?
Glucose -> glucose-6-phosphate
Enzyme - hexokinase
What is the second step of glycogenesis?
Glucose-6-phosphate -> glucose-1-phosphate
Enzyme - phosphoglucomutase
What is the third step of glycogenesis?
Glucose-1-phosphate -> UDP-glucose
Enzyme - UDP-glucose pyrophosphorylase
What is the fourth step of glycogenesis?
UDP-glucose -> {glucose}n+1 + UDP
Enzyme - glycogen synthase
Which is the rate-limiting enzyme in glycogenesis?
Glycogen synthase
It can only add one molecule of glucose at a time to an existing chain of glycogen
Which is the first step in glycogenolysis?
Glycogen -> glucose-1-phosphate
Enzyme - glycogen phosphorylase
Which is the second step in glycogenolysis?
Glucose-1-phosphate -> glucose-6-phosphate
Which is the third step in glycogenolysis?
Glucose-6-phosphate -> glucose
Enzyme - glucose-6-phosphatase
Which is the rate-limiting step in glycogenolysis?
The first step
Glycogen -> glucose-1-phosphate
What are some of the metabolic precursors used in gluconeogenesis?
Lactate
Amino acids
Glycerol
Where does gluconeogenesis take place?
Main in the liver and small amounts in the kidneys
What is the stoichiometry of gluconeogenesis?
2 pyruvate + 4ATP + 2GTP + 2NADH + 4H+ + 6H20
–>
Glucose + 4ADT + 2GDP + 6Pi + 2NAD+ + 2H+
Where are ketone bodies formed?
Liver mitochondria
How are ketone bodies formed?
From Acetyl-CoA from beta oxidation
In starvation
What is ketosis?
Severe acidosis due to accumulation of ketone bodies (which are acidic) in the blood
What does ketosis result in?
Loss of tissue function, particularly the central nervous system
How can ketosis be detected?
Smell of acetone in the breath of the patient
