Energy I: Metabolism, ATP and Glycolysis Flashcards
(25 cards)
List the processes included in the term ‘metabolism’.
- Synthesis of new molecules
- Establishing ion gradients
- Mechanical Work
- Keeping warm
Where do we derive all our energy from?
The food we eat
What is catabolism?
The breakdown of complex molecules to release energy or carry out mechanical work.
What is anabolism?
Synthesis of new molecules from less complex components.
Why must we know about Metabolism?
To know the metabolic basis of diseases like diabetes, atherosclerosis and gall stones. Diseased sate changes the way the body uses food - to understand disease we need to know hoe the body normally deals with nutrients. Can use changes in metabolites to aid diagnostics and to follow treatment.
What processes in metabolism do you need to know about?
Glycolysis, gluconeogenesis, TCA and Urea Cycle.
Discuss the importance of ATP.
ATP is central to a cell and therefore a bodies energy provision.
Can act as both an acceptor and donator of energy. It acts as a short term reservoir of energy.
How much energy is available from the hydrolysis of ATP?
65kj/mole
How much energy is used at rest?
40Kg/24hr
How much energy is used during exercise?
0.5Kg/minute
How much ATP does the body have?
Only 100g - to meet the demands of the body it must re-synthesise ATP from ADP, this is largely done through oxidative phosphorylation and this takes place in the mitochondria
List the major oxidative pathways.
- Glycolysis -Citric acid cycle -Electron Transport coupled to oxidative phosphorylation
- Fatty acid oxidation
Recite the reactants and products for glycolysis.
Reactants Products 1 Glucose 1 Pyruvate 2NAD+ 2NADH 2ADP 2ATP 2Pi
What regulates glycolysis?
Enzymes catalysing irreversible reactions are potential sites for regualtion.
Activity of such enzymes can be regulated by - reversible binding of allosteric effectors -covalent modification -transcription
What can glycolysis rate be measured in?
Milliseconds, seconds and hours
What Enzyme catalyses the first part of glycolysis?
Hexokinase is the initial enzyme of glycolysis, catalyzing the phosphorylation of glucose by ATP to glucose-6-P. It is one of the rate-limiting enzymes of glycolysis. Its activity declines rapidly as normal red cells age. Helps to store glucose, is inhibited by its product G-6-P.
What enzyme cataylses the second part of glycolysis? Stimulators/inhibitors?
Phosphofrucktikinase - catalyses the ATP dependent phosphorylation to convert fructose-6-phosphate into fructose 1,6 Phosphate and ADP, it’s one of the key regulating and rate limiting steps of glycolyis.
- inhibited by ATP, citrate and H+
- Stimulated by AMP
Final enzyme used in glycolysis?
Pyruvate kinase - catalyses the transfer of a phosphate group from phosphoenol pyruvate to pyruvate and ATP. Inhibited by ATP (product)
What happens in muscle s in terms of glycolysis?
Glycolysis is regulated to meet the need for ATP.
ADP+ADP—>ATP+AMP (catalysed by Adenylate kinase)
PFK id the most important control point - high concentrations of ATP inhibit PFK by lowering the affinity for fructose 6 phosphate. Also inhibited by low pH.
Inhibition of PFK leads to…
Inhibition of hexokinase
AMP is a signal for…
Low energy state
Discuss the regulation of glycolysis in the liver?
-Regulation is more complex-
-High concentrations of ATP inhibit PFK
-PFK is inhibited by citrate
-PFK is stmulated by a build up of F6P
-Hexokinase is inhibited by G6P
-But the liver also had gluckinase which is not inhibited by G6P
REFER TO DIAGRAM
Tumours and exercising muscles…
Use a common metabolic pathway - their energy needs are met through anaerobic respiration
Explain how ow oxygen stimulates the expression of many glycolytic enzymes, in tumours?
When tumours outgrown their blood supply, oxygen delivery is reduced, tumour cell metabolism reverts to glycolysis. Reduction in oxygen leads to the acivation of transcription factor HIF-1alpha - this regulates the expression of a number of enzymes in the glycolytic pathway.
