Cell metabolism 1 Flashcards
What are the stages of cell metabolism?
- glycolysis
- TCA cycle
- Oxidative phosphorylation
Where does glycolysis occur?
Cytoplasm
Is glycolysis aerobic or anaerobic?
Anaerobic
What is the net gain of ATP and NADH in glycolysis?
2x ATP
2X NADH
What is the first step of glycolysis?
Glucose -> Glucose-6-phosphate
Enzyme: Hexokinase
ATP to ADP
Group transfer
Irreversible
What is the second step of glycolysis? (after glucose-6-phosphate)
glucose-6-phosphate -> fructose-6-phosphate
Enzyme: phosphoglucose isomerase
Isomerisation
What is the third step of glycolysis? (After fructose-6-phosphate)
fructose-6-phosphate -> fructose-1,6-bisphosphate
Enzyme: Phosphofructokinase
ATP to ADP
Group transfer
What is the fourth step of glycolysis? (After fructose-1,6-bisphosphate)
fructose-1,6-bisphosphate -> glyceraldehyde 3-phosphate + dehydroxyacetone phosphate
Enzyme: aldolase
Hydrolytic
Whats the 5th step of glycolysis? (After glyceraldehyde 3-phosphate + dehydroxyacetone phosphate)
dehydroxyacetone phosphate -> glyceraldehyde 3-phosphate
Enzyme: Triose phosphate isomerase
Isomerisation
Whats the 6th step of glycolysis? (after glyceraldehyde 3-phosphate)
glyceraldehyde 3-phosphate -> 1,3- bisphosphoglycerate
Enzyme: glyceraldehye 3-phosphate dehydrogenase
Nad+ + Pi to NADH
Redox and group transfer
Whats the 7th step of glycolysis? ( 1,3- bisphosphoglycerate)
1,3- bisphosphoglycerate -> 3-phosphoglycerate
Enzyme: phosphoglycerate kinase
Group transfer
ADP to ATP
Whats the 8th step of glycolysis? (after 3-phosphoglycerate)
3-phosphoglycerate -> 2-phosphoglycerate
Enzyme: phosphoglycerate mutase
Isomerisation
Whats the 9th step of glycolysis? (after 2-phosphoglycerate)
2-phosphoglycerate -> phosphoenolpyruvate (+H2O)
Enzyme: enolase
Dehydration reaction
Group removal
Whats the 10th step of glycolysis? (After phosphoenolpyruvate)
phosphoenolpyruvate -> pyruvate
Enzyme: pyruvate kinase
ADP to ATP
Group transfer
In what steps of glycolysis does ATP go to ADP?
Step 1
Step 3
In what steps of glycolysis does ADP go to ATP?
Step 7 (x2) Step 10 (x2)
What are the 3 fates of pyruvate?
- Alcohol fermentation
- Lactate production
- Acetyl CoA production
What happens in alcohol fermentation?
`Pyruvate -> Acetaldehyde -> Ethanol
1st enzyme: pyruvate decarboxylase H+ to CO2
2nd enzyme: alcohol dehydrogenase NADH + H+ -> NAD+
Characteristic of yeast
Anaerobic
REDUCTION
What happens in lactate production?
Pyruvate -> lactate
Enzyme: lactate dehydrogenase NADH + H+ -> NAD+ Reversible Anaerobic Characteristic of mammalian muscle REDUCTION
What happens in Acetyl CoA Production?
Pyruvate + HS-CoA -> Acetyl CoA + CO2
Enzyme: Pyruvate dehydrogenase complex
NAD+ -> NADH
Occurs in mitochondria
OXIDATION
How is lactate dehydrogenase used as a diagnostic tool?
LDH is present in many body tissues
Elevated serum levels can be used to diagnose stoke and myocardial infarction
LDH can also be used to see which patients undergoing chemotherapy for follicular lymphoma will likely undergo relapse
What is the outcome of the TCA/Krebs cycle?
Each cycle produces: 2x CO2 3x NADH 1x GTP 1x FADH2 One cycle for each pyruvate
What kind of reaction does protein metabolism require?
Transaminase reactions: amine group transferred from one amino acid to ketoacid forming new amino acid and ketoacid
Its a group transfer reaction
What are the 7 molecules that all 20 amino acids can degrade into?
Pyruvate Acetyl CoA Acetoacetyl CoA Alpha-ketogluterate Succinyl CoA Oxaloactate Fumarate
What happens to an amino acid once its entered the TCA cycle?
Amino group is removed (Excreted in urea) whilst C skeleton is funnelled into glucose production or Krebs cycle
How does glucose metabolism differ in cancer?
Cells can use increased expression of glucose transporters to propel tumour growth e.g. GLUT-1
We can target GLUT-1 in treatment
Give patient radio labelled 18F glucose- this will accumulate in tissues with high expression of glucose transporters and can be used to locate tumour through imaging
What are 2 ways in which electrons from NADH are transported to the mitochondrial matrix?
- Glycerol-phosphate shuttle
2. Malate- Aspartate Shuttle
How does the glycerol-phosphate shuttle work?
For skeletal muscle and brain
Cytosolic glycerol-3-phosphate dehydrogenase transfers electrons from NADH to dihydroxyacetone phosphate to generate glycerol 3-phosphate
Membrane bound form of same enzyme transfers electrons to FAH, these then pass on to Co-enzyme Q
How does the maltate-aspartate shuttle work?
For liver, kidney and heart
Also relies on cytosolic and membrane bound forms of these enzymes:
Aspartate transaminase
Malate dehydrogenase
Transamination reaction as well as redox reaction (NAD+ to NADH)
What is beri beri?
A thiamine deficiency
Thiamine is a cofactor of pyruvate dehydrogenase complex
Deficiency of thiamine means difficulty to make acetyl CoA
Brain particularly vulnerable
What are symptoms of beri beri?
damage to PNS
weakness of musculature
decreased cardiac output
