PH1123 - Energy and metabolism Flashcards
what is the universal energy molecule?
- ATP
what is the structure of ATP?
- adenine
- ribose
- 3 phosphate groups
what bonding is present in ATP? (2)
- phosphate ester bonds
- phosphoanhydride bonds
what releases energy in ATP?
- hydrolysis of the phosphoanhydride bonds
what are the factors that result in the high energy release during the hydrolysis of phosphoanhydride bonds? (3)
- decrease repulsion between phosphate groups helps drive hydrolysis
- increased resonance in product
- electrostatic repulsion between negative charges in ATP
what are the different stages of energy production? (3)
- stage 1; no useful energy generated
- stage 2; small amounts of ATP generated (anaerobic no oxygen)
- stage 3; majority of ATP production aerobic with oxygen)
what is the energy supply for most organisms?
- metabolism of glucose and other sugars
why is the metabolism of fats and proteins important?
- important energy production when the supply of glucose and other sugars are limited
what is the initial stage of the metabolism of glucose (respiration) called?
- glycolysis
where does glycolysis take place ?
cytoplasm
what are the different reaction types in glycolysis? (6)
- type 1; phosphoryl transfer
- type 2; phosphoryl shift
- type 3; isomerisation
- type 4; dehydration
- type 5; aldol cleavage
- type 6; oxidation
what are the two parts that glycolysis is divided into? (2)
- the first reactions with 6 carbon units which requires energy (hexose stage)
- the reaction on the 3 carbon units which provides energy (triose stage)
what is the net output of ATP in glycolysis?
- 2 molecules of ATP
what does glycolysis produce?
- pyruvate x2
what are the fates of pyruvate? (3)
- conversion to acetyl coenzyme A
- conversion to lactate
- conversion to ethanol
what is acetate coenzyme A?
- compound used in the citric acid cycle and electron transport chain
where does formation of acetyl coenzyme A occur?
- mitochondira matrix
what enzymes is required for the conversion of pyruvate to acetyl CoA?
- pyruvate dehydrogenase
what enzymes is required for the conversion of pyruvate to lactate?
- lactate dehydrogenase
What are the bonds the hold the phosphates together called and what is special about them?
Phosphoanhydride bonds. They are unstable so are easily hydrolysed which generates a lot of energy.
When do organisms start to metabolise fats and proteins?
When the supply of glucose and other sugars is limited.
What are some important points about glycolysis?
Takes place inside of the cytoplasm, requires no oxygen and generates two molecules of NADPH and a NET of 2 ATP
What are the energy requiring steps in glycolysis?
Glucose to glucose 6 phosphate and
fructose 6 phosphate to fructose 1,6 bisphosphate.
What is the role of hexokinase?
Phosphorylates glucose to glucose 6 phosphate
In part one of glycolysis what are the 3 steps?
Glucose to glucose 6 phosphate.
Glucose 6 phosphate to fructose 6 phosphate.
Fructose 6 phosphate to Fructose 1,6-bisphosphate.
What is the enzyme that converts Glucose 6 phosphate into fructose 6 phosphate?
Phosphoglucose isomerase which causes isomerisation.
How does fructose 1,6-bisphosphate spilt into 3 carbon units?
The enzyme aldolase cleaves the molecule, this is called aldol cleavage.
What are the 2 3 carbon structures called formed from the aldol cleavage of fructose 1,6-bisphosphate?
Dihydroxyacetone and glyceraldehyde 3 phosphate.
What happens to Dihydroxyacetone once its been cleaved and why?
It is converted into glyceraldehyde 3 phosphate by triose phosphate isomerase because it has a high entropy so is very reactive and unstable.
What are the 5 conversions that happen in the second part of glycolysis?
Glyceraldehyde 3-Phospahte to 1,3 Bisphosphoglycerate.
1,3-bisphosphoglycerate to 3 phosphoglycerate.
3-phosphoglycerate to 2 phosphoglycerate.
2-phosphoglyceraye to phosphoenolpyruvate.
Phosphoenolpyruvate to pyruvate.
What are the 3 fates of pyruvate?
Conversion to ethanol, lactate, acetyl-CoA
How is acetyl CoA formed?
Pyruvate reacts with coenzyme a, carbon dioxide is generated as well as NADH catalysed by pyruvate dehydrogenase.
When does the conversion of pyruvate to lactate happen?
Occurs when the supply of oxygen is limited.
How is pyruvate converted into lactate?
By lactate dehydrogenase NADH is formed which can be used in glycolysis.
What is the overall reaction of glucose to lactate?
Glucose + 2Pi +2ADP = 2Lactate +2ATP +2H20
How is pyruvate converted to ethanol?
In a 2 step procedure pyruvate decarboxylase converts pyruvate to acetaldehyde. The acetaldehyde is converted to ethanol by alcohol dehydrogenase and NAD+ is formed.
How does ATP/AMP control phosphofructokinase?
High levels inhibit the enzyme, glycolysis is stimulated when the energy levels fall. AMP reverses the effect of ATP.
Describe the citric acid cycle
The citric acid cycle starts with acetyl CoA entering the cycle and being converted to citrate, this is then converted to cis-aconitate which is then converted to iso-citrate. Isocitrate is converted to a-ketoglutarate and then to succinyl CoA. Succinyl CoA is then converted to succinate the fumarate then to malate before malate being converted to oxaloacetate which starts again at the beginning of the cycle.
What molecules and how many of them are produced by the citric acid cycle?
3NADH, 2CO2, 1GTP, 1FADH2.
How many ATP molecules are generated during oxidative phosphorylation?
32
How many molecules of ATP does NADH and FADH generate?
NADH=3
FADH2= 2
Where is each part of the respiration process located?
Glycolysis is located in the cytosol.
The citric acid cycle is located in the mitochondria as well as oxidative phosphorylation.
