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40 Cards in this Set
- Front
- Back
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What is the end product of glycolysis?
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pyruvate
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Where is anaerobic glycosis most significant and why?
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RBCs, no mitochondria
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Mechanisms by which glucose enters a cell
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1) Na independent facillitated diffusion (Glut1,3,2 and insulin dependent $)
2) Na+ monosccharide cotransporter (2ndary active transport) |
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Glut 1 and 3
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- neurons and brain
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Glut 2
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- hepatocytes and pancreas
- only bidirectional transport of glucose both in and out of cell |
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Glut 4
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- only in skeletal muscle and adipose
- only one that is insulin dependent |
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which glut transporter is bidirectional?
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Glut 2 in hepatocytes and pancreas
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which glut transporter is insulin dependent?
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- Glut 4 in skeletal muscle and adipose tissue
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Where does cotransport of glucose take place and what is necessary?
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1) epithelial cells of intestine
2) renal tubes 3) choroid plexus ATP and Na+ |
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what is the first step that is necessary for glycolysis?
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- phosphorylation by hexokinase or glucokinase
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What are characteristics of glucokinase?
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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 |
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What are characteristics of hexokinase?
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1) high affinity, low vmax
2) efficient phosphorylation even when [glucose] low 3) inhibited by glucose-6-phosphate 4) broad specificity |
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In well fed state, what does hexokinase and glucokinase do?
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hexokinase: active because it is not inhibitied by higher glucose levels
glucokinase: would be inhibited by glu6P |
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The most important cotnrol point of Glycolysis
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- step 3:
Fructose6P --> F1,6BP by PFK1 +ATP |
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Name the allosteric regulators of PFK1
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Inhibitors: ATP, citrate, PFK-2phosphatase, Glucagon
Activators: F2,6BP, AMP, ADP, PFK2kinase, insulin |
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Insulins effect on PFK2
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- insulin deP --> activation of PFK2, phosphatase inactive so F26BP formed with insulin
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Most potent activator of PFK1
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-F2,6BP
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What does PFK2 do?
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- convertsF6p ==> F26BP (activates PFK1) -->
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PFK with glucagon
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- phosphorylation of kinase --> inactivation, phosphorylation of phosphatase part--> active --> breaks down F26BP (activator of PFK1) to F6P --> gluconeogenesis
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1st redox reaction in glycolysis and enzyme used?
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- Glyceraldehyde-3-P to 1,3 bisphosphoglycerate by G3P dehydrogenase
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why is the G3Pdehyrogenase reaction important?
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- generates NADH
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what does 2,3 BPG do and where does it do it?
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- lower O2 affinity shifting curve to the right
- in RBC |
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what converts phosphoenopyruvate (PEP) to pyruvate?
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pyruvate kinase
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when is pyruvate kinase more active?
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Fed state
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which type of Hb has a higher affinity for O2?
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Hb F --> 2α 2γ
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what is substrate level phosphorylation and what two reactions use this
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- the formation of ATP
- 1,3BPG --> 3-phosphoglycerate - PEP --> pyruvate |
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What is pyruvate kinase activated by?
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- F16BP
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what inhibits pyruvate kinase?
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- alanine
- phosphorylation in liver during fasting with high glucagon (via cAMP -->PKA) - |
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When is pyruvate kinase activated?
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- fed state
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How are PFK1 and PK linked?
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- PK1--> F16BP --> PK
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Why does lactate accumulate in skeletal muscle?
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- insufficient O2 so ETC is at full speed, so too much NADH
- Pyruvate + NADH --> lactate |
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Fates of Pyruvate
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1) Acetyl CoA --> FA synthesis
2) Alanine by amino transferase 3) Lactate by LDH 4) OAA by Pyruvate Carboxylase |
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When would TCA not take place and why?
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- EtOH
- increase in [NADH] --> lactate production --> lactic acidosis - EtOH --> acetylaldehyde --> acetic acid --> NADH |
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Overall energy yield of anaerobic glycolysis?
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2 ATP
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Overall energy yield of Aerobic glycolysis
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8 ATP
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Most common enzyme deficiency in glycolysis
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pyruvate kinase --> decrease in activity of cell, hemolytic anemia
- lower ATP changes the structure of the RBC |
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type of regulation most important for long term activity of the body
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negative feedback
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which potent activator is increased in a fed state?
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Insulin
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PFK 2 in the fed state
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- dephosphorylated --> active kinase
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PFK 2 in fasting state
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- phosphorylated --> phosphatase active
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