What is glycolysis?
The converson of glucose to yeild 2 pyruvate molecules, 2 NADH and 4 ATP
What are the three areas of Carbohydrate Fuel Metabolism?
- 1) Users
- 2) Storage
- 3) Regulatory
What are the users in carbohydrate fuel metabolism?
- Brain: A carbohydrate driven organ, which only under dire conditions use lipids for energy
- Uses glycolysis and the TCA cycle to obtain energy.
Muscle: Capable of using carbohydrate, fatty acid and amino acids as a energy source. It an also at as a storage center for glycogen and fatty acid break down
What are the storage structures of fuel metabolism?
Adapose tissue: Tryglyceride storage
Liver: Glycogen storage. Is capable of storing more per/unit than the muscle, but there is a lot more muscle tissues. Not just for storage, can also perform gluconeogenisis if energy levels are low, and fatty acid synthesis.
What are the regulatory structures of Fuel Metabolism?
- Islets of langerhans : located just above the pancreus, 1% part of the endocrin system, composed of different type of cells.
- Beta cells - inculin producer, where insulin targets the liver, muscles and adapose tissues.
- - in the liver, insulin triggers glycolysis and fatty acid synth (with can be sent to the adapose tissues to store metabolites.)
- - insulin triggers the release of metabolites and inhibit fatty acid release.
What are the 2/3 phases of the glycolytic pathway
Prepatory: 2 ATP used, glucose is phosphorilated to yeild Fructose 1,6-bisphosphate which is then cleaved in half by aldose to yeild dihydroxyacelone and glyceraldehdye 3-phosphate.
Payoff : Everything happens twice, one for each molecuel proced in the prepratory phase. Only 1 set of enzymes is used. Gain 2 ATP per molecule, net gain of 2 ATP
In prepatory stage 1, how is glucose converted?
Glucose + Hexokinase (glucokinase)+ 1 ATP = Glucose 6-phosphate
Glucose 6-phosphate + phosphoglucose isomerace + 1 ATP = Fructose 6-phosphate
Fructose 6-phosphate + phosphofrutokinase (PFK1) = Fructose 1,6-phosphate
What are the major glucose carrier protiens and their functons?
Glut1 - A common transport in all mammalian cells, basal glucose uptake. Efficiant transport and capable of working all the time.
Glut2 - Specialized glucose transport in the pancreas and the liver. In the islets of longerhans, beta cells need a glucose sensor. The liver is mainly a fatty acid metabolizer, doesn't take up much glucose but after a meal some glucose may enter.
Glut3 - found in all mammalian tissues, basal glucose uptake
Glut4 - found in muscle and fat cells, it is not an efficiant transporter. Spends most of its time in the cell. When glucose is needed, insulin triggers Glut4 to the cell surface, allowing a large amount of tranport in a short period
Glut5 - found in the intestines
What happens in prepatory stage 2?
Fructose 1,6- phosphate is cleaved by aldose to yeild glyceraldehyde 3-phosphate and dihydroxyacetone phosphate. Triose phosphate can initiate a shift in products depending upon product equalibrium concentrations.
What happens in the payoff phase (stage 3) of glycolysis?
Phase occurs twice, once for each glucose molecule yeilding 2 pyruvate molecules, 2 NADH and 4 ATP
- Glyceraldehyde 3-phosphate + de-electronace + NAD+ = 1,3-bisphosphoglycerate + NADH
- 1,3-Bisphosphoglycerate + phosphoglycerate kinase + ADP = 3-Bisphosphoglycerate + ATP
- 3-Bisphosphoglycerate + phosphoglycerate mutase = 2-phosphoglycerate
- 2- phosphoglycerate + enolase = Phospheonolpyruvate + H20
- Phospheonolpyruvate + pyruvate kinase + ADP = Pyruvate + ATP
How is glycolysis regulate?
Glycolysis is stimulated by insuling and inhibited by glucogon.
Key Allosteric regulatory steps:
Hexokinase is inhibited by G-3-P
PFK-1 is inhibited by ATP, low pH(muscle) and Citrate(liver). It is stimulated by AMP and F-2,6-BP(liver)
Pyruvate kinase is inhibited by ATP and alanine and stimulated by Fructose-1,6-BP
Describe the allosteric regulation of Hexokinase.
- There are 4 variations, Hexokinase 1-3 are located in muscle cells and are inhibited by G-6-P. Hexokinase 2 is the major form of the enzyme. Hexokinase 1-3 are active at low glucose concentrations.
- Hexokinase 5 is found in the liver and requires high levels of glucose to be present for activation, it does not experience product inhibition like 1-3.
What is glucokinase's role in liver cells?
It is also known as Hexokinase 5 and is only active when glucose levels are high in the body.
Describe the allosteric regulation of PFK-1 by ATP
PFK-1 activity is dependent upon ATP concentration. Idealy, at high concentrations of ATP PFK-1 is inhibited and demonstrates a low rxn activity and in low ATP concentrations PFK-1 is active and displays a greater rxn velocity. However, in reality, the rxn rate of PFK-1 is variable ance can be anywhere, and reflects how the biological system is operating at many points.
Describe the role of fructose-2,6-bisphosphate.
PFK-1 is activated by F-2,6-BP, where the greater the concentration of F-2,6-BP the greater the rxn rate of PFK-1 will be. Some ATP is required for the rxn to occur, where ATP acts as a signaler. If there is an abundant amout of energy present, ATP production stops and ATP acts as an inhibitor.
What and why is NAD+ regneration needed in hypoxic conditons?
- NAD+ is regenerated by lactate dehydrogenace (de-electronase) by reducing a pyruvate molecule into lactate. This requires 1 NADH, and H+. The this provides 2e-, with which pyruvate is reduced.
- This allows the cell to continue glycolysis, by reusing NAD+ to generate NADH and allow for ATP synth.
What organs are critically dependent on glycolysis for energy?
The Brain runs nearlly only glucose, therefore it gains its energy via glycolysis.