Term
| What are the three general ways that glycolysis is regulated? |
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Definition
1) Glucose uptake by cells (glut transporters)
2) Hormonal Regulation (insulin/glucagon and fed/fasting state)
short term (via insulin and glucagon regulation on pyruvate kinase) and long-term (gene expression of Glucokinase, PFK-1 and pyruvate kinase)
3) Allosteric regulation ( glucokinase, hexokinase and PFK-1)
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Term
| How do GLUT2 transporters work? |
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Definition
GLUT 2 transporters are in the liver, beta-cells and kidney. They are highly regulated based on blood glucose levels and insulin independent. They are on the cell membrane. |
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Term
| How do GLUT4 transporters work? |
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Definition
| GLUT4 transporters are insulin dependent. When insulin is high they move to the plasma membrane so they can transport blood glucose into the cell. GLUT4 receptors are on cardiac myocytes, skeletal myocytes and adipocytes. |
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Term
| Why is pyruvate converted to lactate under anaerobic conditions? |
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Definition
- During anaerobic conditions, pyruvate is converted to lactate and in the process NADH is converted back to NAD+
- The NAD+ is used to go through glycolysis again and produce aditional energy by producing NADHs
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Term
| What is glucokinase and how is it regulated? |
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Definition
- Glucokinase is in the liver
- Glucokinase converts glucose to glucose-6-phosphate
- Has high Km and low Vmax
- It's low affinity for glucose is necessary so that other cells can get the glucose first when they need it. Glycolosis in liver only occurs when there are high levels of blood glucose
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Term
| What is hexokinase and how is it regulated? |
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Definition
- Hexokinase is in most tissues that need glucose
- Hexokinase has a low Km and low vmax
- The high affinity for glucose means cells can take it quickly eg: brain cells
- Allosterically inhibited by G6P (b/c at this point cells have all the glucose they need)
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Term
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Definition
- Activated by: AMP, Fructose-2,6-bisphosphate
- Inhibited by: ATP (from ETC) and citrate (from TCA)
- This is the most regualted step and it is very important. High ATP levels will signal that there is already a high level of energy and this will slow down glycolysis.
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Term
| Explain the PFK-2 mechanism |
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Definition
| When the insulin/glucagon ratio is high, cAMP is low and this causes acitve PKA to be low. This favors dephosphorylation of PFK-2/FBP-2 complex which activates PFK-2 and favors the formation of Fructose2,6 bisphosphate. This activates PFK-1 and increases the rate of glycolysis. |
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Term
| What is pyruvate kinase? What does it do? How is it regulated? |
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Definition
- Pyruvate kinase converts phosphoenol pyruvate to pyruvate and produces 2 ATPs from 2ADPs
- Activated: PFK1 via feed forward regulation, insulin via dephosphorylation
- Inhibited: glucagon via phosphorylation
- When insulin is present, protein phosphatase dephosphorylates pyrvate kinase which activates it.
- When glucagon is present, PKA is high which phosphorylates pyruavte kianse and inactivates it
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Term
| What are the products of glycolysis? |
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Definition
(2) 3 carbon pyruvates, (2) NADH, (2) ATP
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