(Dr. McLachlin) (Unit B) Topic Note 9 Flashcards
What is the phosphorylated form of glucose?
Glucose-6-phosphate (G6P)
How does glucose provide energy to the cell?
Oxidized in glycolysis
Where is glycogen stored?
Liver and striated muscle
How is glucose converted to glycogen?
- G6P converted to G1P
- G1P added to glycogen chain
Step 2 is a two step process, involves:
1. Net hydrolysis of UTP to UDP and Pi
2. Second step catalyzed by glycogen synthase
How are glucose monomers removed from glycogen when glucose is required?
Removed as G1P
* By glycogen phosphorylase
* Phosphate comes from inorganic phosphate dissolved in the cytosol
How does phosphorylation affect glycogen synthase?
- Phosphorylated = Less active
- Dephosphorylated = More active
How does phosphorylation affect glycogen phosphorylase?
- Phosphorylated = More active
- Dephosphorylated = Less active
How is the phosphorylated vs. dephosphorylated form concentrations of glycogen synthase/phosphorylase determined?
Hormone signals
* Insulin
* Glucagon
How does insulin work?
Released by pancreas into the bloodstream when blood glucose levels are high
How does glucagon work?
Stimulates glycogen breakdown in liver but not skeletal muscles
* Maintains blood glucose level
What controls glucose levels in skeletal muscles?
Norepinephrine
What is glycogen synthase allosterically activated by?
G6P
What is glycogen phosphorylase allosterically regulated by in:
1. Skeletal muscles
2. Liver
- Activated by AMP, Inhibited by ATP and G6P
- Inhibited by glucose
What is glycolysis?
Oxidative process that occurs in the cytoplasm
What is the net reaction of glycolysis and how many steps are there?
10 Steps
Glucose + 2 ADP + 2 Pi + 2 NAD+
–>
2 pyruvate + 2 NADH + 2 ATP
How many electrons are transferred from glucose to NAD+ molecules in glycolysis?
4 electron to 2 NAD+
Which steps of glycolysis are considered irreversible? Why?
Steps 1, 3, 10
* Large, negative value for ΔG
What are the enzymes are will control flux through glycolysis?
- Hexokinase
- Phosphofructokinase (PFK)
- Pyruvate kinase
Why does fermentation occur even though glycolysis doesn’t use oxygen?
Glycolysis produces NADH, which in the end gives its electrons to oxygen to become NAD+ (regenerating NAD+)
Without oxygen, we cannot regenerate NAD+
So we need another process to regenerate NAD+ in the absence of oxygen
Where does Lactate Fermentation occur?
In many microorganisms, in higher organisms when little oxygen in available
Formation of Lactate
Pyruvate + NADH
–>
Lactate + NAD+
Fermentation of glucose to lactate
Glucose + 2 ADP + 2 PI
–>
2 lactate + 2 ATP
Where does Ethanol Fermentation occur?
Yeast, and several other microorganisms
Formation of ethanol
2 step process:
Step 1
Pyruvate + H+
–>
CO2 + Acetaldehyde
Step 2
Acetaldehyde + NADH
–>
Ethanol + NAD+
