LECTURE 12 Flashcards
What is the source of ATP for almost all eukaryotic organisms?
Cellular respiration
Do almost all organism metabolize glucose ?
YES
Where does glycolysis occur ?
Cytosol
Where does the kerbs cycle ?
Mitochondria
Where does fermentation occur ?
Cytosol
Glycolysis
1 glucose —-> 2 pyruvate + 2 NADH
The 2 ways for further metabolism of pyruvate
1) kerbs cycle and electron transport chain
2) fermentation
Kerbs cycle / citric acid cycle
Uses O2 as a final electron acceptor
- called aerobic respiration (needs O2)
Fermentation
- converts pyruvate to waste products (ethanol or lactic acid)
- different pathways in different organisms
- does NOT use O2 or an electron transport chain.
What accounts for most of ATP synthesis
Oxidative phosphorylation (OXPHOS)
Where does OXPHOS occur?
Mitochondria
2 phases of glycolysis
1) investment phase
2) energy payoff phase
Steps for energy investment (5) in glycolysis
1) hex Okinawa enzyme transfers phosphate to ATP. Makes glucose more reactive
2) glucose-6-phosphate is converted to its isomer fructose-6-phosphate.
3) phosphofructokinase transfers a phosphate to ATP to the opposite end of the sugar (requires a second ATP)
4) adolescences cleaves the 6-carbon sugar into these two 3-C sugars
5) isomerase causes a flip between these two isoforms, the direction on the concentration of reactants.
Glyceralhyde 3-phosphate is rapidly used up, so the equilibrium shifts to favour conversion in that direction.
Steps for energy payoff (5) in glycolysis
1) this enzyme catalyzes two couples reactions
A) each G3P is oxidized by transferring 2 e- to NAD+ (exergonic)
B) a phosphate bond is a made, producing a product with very high potential E (endergonic)
2) phosphate added in step 1 is transfers to ADP (exergonic) = substrate level phosphorylation
3) this enzyme changes the location of the phosphate
4) enolase creates a double bond and removes H2O
- PEP contains very high potential E.
5) pyruvate kinase creates ATP via substrate level phosphorylation
The two reactions couples in step one of energy payoff in glycolysis
A) each G3P is oxidized by transferring 2 e- to NAD+ (exergonic)
B) a phosphate bond is a made, producing a product with very high potential E (endergonic)
4 mains points of glycolysis
- 10 reactions
- occurs in cytoplasm
- anaerobic (No oxygen required)
- occurs in all domains of life
NET products of glycolysis
2 molecules of ATP
2 molecules of pyruvate
(3-C =0.5 of glucose)
2 molecules of NADH
In eukaryotic cells in the presence of O2 …
Pyruvate enters the mitochondrion where oxidation of glucose is completed
Before krebs can begin, pyruvate must be
Converted to acetyl coenzyme (acetyl CoA)
This links glycolysis to Krebs cycle
What is the acetyl CoA made of ?
Acetyl group
Ribose
Adenine
What is CoA a derivative of and what’s its role ?
Vitamin B
It’s troll if in transferring one molecules (or party of one molecule) to another
Oxidation of acetyl CoA
Pyruvate enters into mitochondria
A multi-enzyme complex (pyruvate dehydrogenase complex) then catalyzes these 3 reactions :
1) pyruvate’s carboxyl group already oxidized and contains little E - its removed
2) the remaining 2-C molecules is oxidized; the electrons are transferred to NAD+
3) coenzyme A is attached via its sulfur atom to acetyl group, forming acetyl CoA (has high potential E)
In oxidation fo pyruvate to acetyl CoA, Pyruvates entry into the mitochondria requires
Active transport
