metabolism and cellular respiration Flashcards
1
Q
what are examples of biochemical pathways
A
- metabolism: all chemical reactions carried out by an organism
- catabolism: degradation reactions harvest energy and are exergonic
- anabolism: synthesis reactions expend energy to make chemical bonds and are endergonic
2
Q
what is ATP
A
- ‘currency’ of cell, loaded string, temporary storage of energy
- 5 carbon sugar, adenine, triphosphate (energy storage)
- ‘high energy’ phosphate bonds (phospho-anhydride), weak, unstable, ideal for short term energy source
3
Q
what is the coupling of ATP hydrolysis to endergonic reactions
A
- cost of work = regeneration of ATP
- transferral of a phosphate group permits anabolic reactions (ATP to ADP + P)
- phosphorylated intermediate is primed (less stable) to undergo work (attachment of ATP), splitting of ATP
- example = NaK pump
4
Q
how do we regenerate ATP via exergonic reactions
A
- energy from catabolism supports regeneration of ATP
- breakdown of carbs during respiration releases energy (exergonic), in turn is used to drive ATP production (endergonic)
- ATP - ADP + P = exergonic
- building proteins by cell (endergonic)
5
Q
what is cellular respiration
A
- break down organic molecules and release energy
- anaerobic: no O2, cytoplasm (strenuous exercise)
- aerobic: O2, mitochondria
- equation: C6H12O6 + 6O2 —> 6 CO2 + 6 H2O + ATP (energy) + heat
6
Q
what is oxidation / reduction of covalent bonds
A
- paired donor / acceptor of electrons, complete / partial
- oxidation: loss of electrons
- reduction: gain of electrons
- partial transfer: degree of electrons sharing charges, e- = facilitators of ATP
- glycolysis: C6H12O6 + 6O2 —> 6 CO2 + 6 H2O + ATP (energy) + heat
- C of glucose = oxidised: e-‘s associated with C-H = evenly shared, drawn towards O (away from C) in CO2
- O of O2 is reduced: e-‘s associated with O=O = evenly shared, drawn closer to O in H2O (less energy, more stable), energy = transferred to ATP
7
Q
what is aerobic respiration
A
- cells catabolise glucose and make ATP in two stages
- substrate level phosphorylation: energy derived directly from organic substrate, catalysed by cytosolic enzymes
- oxidative phosphorylation: energy derived from proton gradient, reduction of O2, make ATP from ADP
8
Q
what is glycolysis
A
- ubiquitous, substrate level phosphorylation (SLP)
- conversion of glucose (6C) to form 2 pyruvate (3C), 2 ATP and 2 NADH
- occurs in cytoplasm
- 10 step reaction, divided into two phases (priming / SLP)
9
Q
what are the steps of glycolysis
A
priming: energy investment
1. manipulation / phosphorylation of glucose (6C) to form glyceraldehyde-3-phosphate (3C), uses 2 units of ATP
SLP: energy payoff
2. oxidation of glyceraldehyde-3-phosphate (3C), 2 e- transferred to NAD+ (reduced to NADH), energy released adds P to each sugar (phosphorylation
3. P transferred to ADP = ATP (x2), molecule rearranged to phosphoenolpyruvate (PEP), P transfered to ADP = ATP (x2), pyruvate formed (x2)
10
Q
what is the pre citric acid cycle
A
- occurs in cytoplasm / mitochondria
1. oxidation of pyruvate (3C) creates acetate (2C) binds with coenzyme A = acetyl CoA (x2) and CO2 (x2)
2. e- ‘harvested’ and reduces NAD+ to NADH (x2)
11
Q
what is the citric acid cycle
A
- combine AcetylCoA (2C) + oxaloacetic acid (4C) = citrate / citric acid (6C)
- e- harvested (ETC, drive ATP synthesis)
- regeneration of oxaloacetate (cycle)
- 6x NADH, 2x ATP, 2x FADH2
12
Q
what are the steps of the citric acid cycle
A
- entry: acetate (2C) combines with oxaloacetate (4C) to produce citrate (6C), CoA is removed (CoA is added originally for entry into matrix)
- isomerisation: citrate is rearranged to isocitrate (6C)
- first oxidation: isocitrate (6C) is oxidised to ketaloglutaric acid (5C), producing CO2 and converting NAD+ to NADH
- second oxidation: ketalglutaric acid oxidised to succinyl-CoA (4C), producing CO2 and converting NAD+ to NADH
- phosphorylation: PO4- displaces CoA (energy produced), energy = coupled to synthesis of ATP, conversion of succinyl-CoA to succinic acid (4C)
- third oxidation: succinic acid (4C) oxidised to fumaric acid (4C) reduce FAD to FADH2
- rearrangement: H2O added to fumaric acid (4C) rearrange bonds = malic acid (4C)
- malic acid (4C) oxidised to form oxaloacetate (4C) and convert NAD+ to NADH
13
Q
what are electron transport chain proteins
A
- multi-protein complexes and electron carriers integrated into inner membrane of mitochondria
- pump H from matrix to inter-membrane space
- high affinity for e-
- 3 large complexes linked by 2 mobile carriers (MC)
- production of a gradient, increased affinity for next protein complex, energy from e- to pump H across
- decrease in pH = increase H
14
Q
what is the sequence of electron flow
A
- NADH transfer electrons to first protein complex
- ubiquinone (CoQ - carrier) passes the e- to second complex
- FADH2 transfers (lowers energy) electrons to CoQ
- location of CoQ = mobile, in membrane, non-polar
- cytochrome c (carrier) transfers e- to third complex
- third complex (oxygen, high electronegativity, ultimate acceptor, interacts with e-) transfers e- to O2
- O2 (+ 4H + 4e-) becomes 2H2O (metabolic water)
15
Q
how is a proton gradient created
A
- energy retrieved from electron flow is used to pump H across membrane
- exergonic interaction of electrons with each complex causes conformational change
