Carbohydrates- glycolysis (Part 1) Flashcards
How are enzyme reactions in cells organized?
What is metabolism and what does it include? Pathways that regenrate one of the components are called?
- Enzymatic reactions in cells – organized into multi-step sequences called pathways
- Product of one reaction serves as substrate for the next reaction
- Different pathways intersect; forming an integrated network of chemical reactions
- Metabolism is the sum of all chemical changes occurring in a cell, tissue or body
- Metabolism includes catabolic (degradative) and anabolic (synthetic) reactions
- Pathways that regenerate one of the components are called cycles
What can sythesize glucose and how can glucose be used to make products?
What is glycolysis ?In what conditions does it take place? What is the end product? It is the predominant type of energy in which type of cells?
- Cellular pathway that breaks down glucose to pyruvate or lactate with the release of energy
- Universal pathway, occurs in all cells
- Takes place in both aerobic and anaerobic conditions
- End product- pyruvate (aerobic conditions) or lactate (anaerobic conditions)
- Exclusive source of energy in those cells that do not contain mitochondria (rbc)
- Major source of energy under anaerobic condition
Where are the glycolytic enzymes located? How many reactions are there in aerobic and anaerobic conditions? How many irreversible reactions are there and what are they catalyzed by? How are are reactions divided?
- All the glycolytic enzymes are located in cytosol
- 10 (aerobic conditions) or 11 (anaerobic conditions) reactions•There are 3 irreversible reactions
- They are catalyzed by 3 different Kinases
- These 3 reactions are also regulatory (key) reactions of glycolysis
- Reactions can be divided into energy investment or priming phase and energy generation phase
Draw the reactions of glycolysis and label where there energy is invested and where the energy is spent and how many ATP does NADH yield? Which are the key reactions? Where are the substrate- level phosphorylation occurring? Where is energy generated? How many molecules of pyruvate does it result in?
How many ATP is invested and how many ATP & NADH are generated in the energy generation phase?
2 ATPs are consumed in the energy investment phase
4 ATPs and 2 NADH are generated in the energy generation phase
What does phosphorylation of glucose by heokinase/glucokinase do?
Initially when glucose is in the cytoplasm it can easily cross the membrane into the extracellular fluid, so in order to trap it, glucose is kept inthe cell by phosphorylation to G6P which cannot easily cross the plasma membrane. Note: charged molecules do not cross the membrnae easily
Describe the distribution , km for glucose, Vmax, inhibition by glucose-6-phosphate and if it is inducible for:
Hexokinase and Glucokinase
Compare Hexokinase and glucokinase and what is the clinial correlation of glucokinase
Hexokinase
- Phosphorylates glucose even at low glucose levels
- Acts at a constant rate to provide glucose 6-phosphate for the cell’s need
Glucokinase
- Is not saturated even at high glucose levels, is able to remove glucose from blood following a meal
- Acts as a glucose sensor in b-cells of pancreas
- Glucokinase acts as glucose sensor in b-cells of pancreas
- Mutations that decrease activity of glucokinase cause maturity onset diabetes of the young type 2 (MODY 2)
- In MODY 2, b-cells secrete insulin only at very high glucose levels
What happens during glycolysis under aerobic and anaerobic conditions? What is the role of LDH? Does the ETC in the absence of oxygen?
During Glycolysis:
Under aerobic condition:
- 1 molecule of glucose is converted into 2 molecules of Pyruvate
- NADH oxidized in the electron transport chain (ETC) to NAD which goes back to glyceraldehyde 3-P DH reaction
Under anaerobic condition:
•1 molecule of glucose is converted to 2 molecules Lactate
1 Glucose -> 2 Pyruvate -> 2 Lactate
Pyruvate -> Lactate
LDH
•LDH regenerates the NAD+ needed for the glyceraldehyde 3-P DH reaction; ETC does not function in absence of oxygen
Explain substrate level phosphorylation and oxidative phosphorylation
Substrate level phosphorylation
Synthesis of ATP coupled to the conversion of a substrate into product
Eg: phosphoglycerate kinase & pyruvate kinase reactions
Oxidative phosphorylation
Synthesis of ATP coupled to transport of electrons in the electron transport chain in mitochondria
Eg: From oxidation of each NADH – 2.5 ATPs
During Aerobin glycolysis , how much ATP is produced by substrate level phosphorylation and oxidative level phosphorylation? How muchh ATP is utulized for activation? and what is the NET ATP produced?
During anaerobic glycolysis, How much ATP is produced by substrate level phosphorylation and how much ATP is produced by oxidative level phosphorylation? How much is utilized for activation and what is the NET ATP?
Compare aerobic and anaerobic glycoylsis
lactate formation and utilization: What happens when lactate is produced in exercising skeletal muscle and when it is produced in the liver and the heart
1.In exercising skeletal muscle
•lactate production increases
•Causes drop in intracellular pH (may cause cramps)
•Eventually diffuses into bloodstream
2. In liver and heart
- Liver oxidizes lactate from blood to pyruvate and then converts it to glucose or oxidizes it through TCA cycle
- Heart muscle oxidizes lactate from blood to pyruvate and then oxidizes it through TCA cycle
