H2 Biology 24 - Respiration

1. NAD acts as a coenzyme(for dehydrogenase) & as a H atom/proton/electron carrier

2. NAD is reduced to NADH in Krebs Cycle

3. NADH carries H atom/protons & electrons to ETC(inner mitochondrial membrane) to be used in oxidative phosphorylation(OP).

an energy coupling mechanism that uses energy stored in the form of electrochemical & proton gradient across biological membrane to synthesise ATP

1. regeneration of NAD & FAD(only Kreb's Cycle) to be reused for glycolysis, link reaction & Krebs cycle, allowing aerobic respiration to continue

2. produce large amounts of ATP(chemiosmosis) for organism's use

site of aerobic respiration for ATP synthesis > ATP is synthesised from the [O] of organic materials such as glucose in presence of O₂ > ATP channeled to other parts of cell

1. inner membrane provides large SA which holds ATP synthases, enzymes & e- carriers in ETC needed for AR

2. membranes are impermeable to H⁺ > H⁺ accumulates in

intermembrane space > forms electrochemical & proton gradient across inner membrane

3. site of ATP synthesis by chemiosmosis when H+ diffuse from intermembrane space down electrochemical gradient through ATP synthase back to matrix

4. compartmentalisation > specialised metabolic pathways can take place

cystosol

mitochondria

takes place in cytosol(both AeR, AnR)

G phosphorylated by 1 ATP to G6P > G6P isomerised to F6P > F6P phosphorylated by 1 ATP to F1,6P > F1,6P split to 2 TP > 2 TP phosphorylated by 2 P_i & [O] by 2 NAD to 2 GB > 2 GB converted to 2GP, 2 ATP formed by SLP > 2 GP converted to 2 pyruvate, 2 ATP formed by SLP

takes place in matrix, only AeR

2 pyruvate translocated into matrix from cytosol via transport protein, undergoes OD to form 2 a(CoA)

takes place in matrix, only AeR

a(CoA) + OA condensed to C > C undergoes OD to a-KG, CO₂ released & NAD->NADH > a-KG undergoes OD to S, CO₂ released, NAD->NADH, ATP formed(SLP) > S [O] to F, FAD->FADH₂ > F converted to M > M undergoes [O] to OA, NAD->NADH, OA ready to accept 2C fragment from a(CoA)

takes place in inner membrane, only during AeR

e^- flow down ETC

H atoms dissociate from NADH, FADH₂ & split to H⁺, e^- > inner membrane impermeable, H⁺ remains in matrix > NAD, FAD regenerated for reuse > e^- transferred down ETC of series of progressively lower energy levels via redox to final e^- acceptor, O₂

Chemiosmosis

e^- passed down carriers in ETC > energy released, used to pump H⁺ via active transport from matrix across inner membrane into intermembrane space > H⁺ accumulates, electrochemical/proton gradient set up for ATP synthesis > H⁺ diffuse through ATP synthase into matrix, flow of H⁺ releases energy driving phosphorylation of ADP>ATP

1. oxygen is the final electron acceptor @ the end of ETC, combines w/ e- & protons to form water, catalysed by cytochrome oxidase

2. e^- accepted by O₂, thus NADH, FADH₂ & e^- carriers along ETC are oxidised, regenerating NAD & FAD

3. this maintains e^- flow along ETC & built up proton gradient across inner membrane for ATP synthesis by chemiosmosis

Glycolysis: 2 ATP, 2 NADH, 2 pyruvate

Link reaction: 2 ATP, 2 NADH, 2 acetyl CoA

Krebs cycle: 2 ATP, 2 CO₂, 2 NADH, 2 FADH₂

Oxidative phosphorylation: 34 ATP

1. phosphorylate ADP to ATP

2.allow H⁺ to pass through membrane

NAD acts as coenzyme for dehydrogenase, H atom & e^- carrier >

carries H e^- & protons to ETC in IMM, used in OP >

where NADH [R] to NAD⁺, regenerating NAD⁺ for subsequent glycolysis, LR & KC

glycolysis occurs, 2x ATP gain >

pyruvate [R] by NADH, form lactic acid/lactate >

NAD⁺ regenerated, lactic acid converted to pyruvate for aerobic respiration

glycolysis occurs, 2x ATP gain >

pyruvate undergoes OD form acetaldehyde & CO₂(bubbling) >

acetaldehyde [R] by NADPH, form ethanol >

NADP⁺ regenerated