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40 Cards in this Set

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What is the end product of glycolysis?
pyruvate
Where is anaerobic glycosis most significant and why?
RBCs, no mitochondria
Mechanisms by which glucose enters a cell
1) Na independent facillitated diffusion (Glut1,3,2 and insulin dependent $)
2) Na+ monosccharide cotransporter (2ndary active transport)
Glut 1 and 3
- neurons and brain
Glut 2
- hepatocytes and pancreas
- only bidirectional transport of glucose both in and out of cell
Glut 4
- only in skeletal muscle and adipose
- only one that is insulin dependent
which glut transporter is bidirectional?
Glut 2 in hepatocytes and pancreas
which glut transporter is insulin dependent?
- Glut 4 in skeletal muscle and adipose tissue
Where does cotransport of glucose take place and what is necessary?
1) epithelial cells of intestine
2) renal tubes
3) choroid plexus
ATP and Na+
what is the first step that is necessary for glycolysis?
- phosphorylation by hexokinase or glucokinase
What are characteristics of glucokinase?
1) low affinity for glucose
2) high vmax, so can be more saturated with glucose
3) in liver and islet cells of pancreas
4) best after consumption of carb rich meal
5) minimizes hyperglycemia by trapping glucose inside hepatocytes
What are characteristics of hexokinase?
1) high affinity, low vmax
2) efficient phosphorylation even when [glucose] low
3) inhibited by glucose-6-phosphate
4) broad specificity
In well fed state, what does hexokinase and glucokinase do?
hexokinase: active because it is not inhibitied by higher glucose levels

glucokinase: would be inhibited by glu6P
The most important cotnrol point of Glycolysis
- step 3:

Fructose6P --> F1,6BP
by PFK1 +ATP
Name the allosteric regulators of PFK1
Inhibitors: ATP, citrate, PFK-2phosphatase, Glucagon

Activators: F2,6BP, AMP, ADP, PFK2kinase, insulin
Insulins effect on PFK2
- insulin deP --> activation of PFK2, phosphatase inactive so F26BP formed with insulin
Most potent activator of PFK1
-F2,6BP
What does PFK2 do?
- convertsF6p ==> F26BP (activates PFK1) -->
PFK with glucagon
- phosphorylation of kinase --> inactivation, phosphorylation of phosphatase part--> active --> breaks down F26BP (activator of PFK1) to F6P --> gluconeogenesis
1st redox reaction in glycolysis and enzyme used?
- Glyceraldehyde-3-P to 1,3 bisphosphoglycerate by G3P dehydrogenase
why is the G3Pdehyrogenase reaction important?
- generates NADH
what does 2,3 BPG do and where does it do it?
- lower O2 affinity shifting curve to the right
- in RBC
what converts phosphoenopyruvate (PEP) to pyruvate?
pyruvate kinase
when is pyruvate kinase more active?
Fed state
which type of Hb has a higher affinity for O2?
Hb F --> 2α 2γ
what is substrate level phosphorylation and what two reactions use this
- the formation of ATP
- 1,3BPG --> 3-phosphoglycerate
- PEP --> pyruvate
What is pyruvate kinase activated by?
- F16BP
what inhibits pyruvate kinase?
- alanine
- phosphorylation in liver during fasting with high glucagon (via cAMP -->PKA)
-
When is pyruvate kinase activated?
- fed state
How are PFK1 and PK linked?
- PK1--> F16BP --> PK
Why does lactate accumulate in skeletal muscle?
- insufficient O2 so ETC is at full speed, so too much NADH
- Pyruvate + NADH --> lactate
Fates of Pyruvate
1) Acetyl CoA --> FA synthesis
2) Alanine by amino transferase
3) Lactate by LDH
4) OAA by Pyruvate Carboxylase
When would TCA not take place and why?
- EtOH
- increase in [NADH] --> lactate production --> lactic acidosis
- EtOH --> acetylaldehyde --> acetic acid --> NADH
Overall energy yield of anaerobic glycolysis?
2 ATP
Overall energy yield of Aerobic glycolysis
8 ATP
Most common enzyme deficiency in glycolysis
pyruvate kinase --> decrease in activity of cell, hemolytic anemia
- lower ATP changes the structure of the RBC
type of regulation most important for long term activity of the body
negative feedback
which potent activator is increased in a fed state?
Insulin
PFK 2 in the fed state
- dephosphorylated --> active kinase
PFK 2 in fasting state
- phosphorylated --> phosphatase active