week 6 al

Where does pyruvate go in eukaryotes if O2 is present?

Into the mitochondrion to finish glucose oxidation

Pyruvate oxidation products per pyruvate?

1 acetyl CoA, 1 CO2, 1 NADH

The citric acid cycle completes the breakdown of pyruvate to…

CO2

Each turn of the citric acid cycle oxidizes molecules from…

one pyruvate

Citric acid cycle yield per glucose (2 turns)?

2 ATP, 6 NADH, 2 FADH2

How many steps are in the citric acid cycle?

Eight, each with a specific enzyme

Acetyl CoA's acetyl group combines with ____ to form ____

oxaloacetate; citrate

Why is it called a cycle?

The next 7 steps break citrate back down to oxaloacetate, which is reused

NADH and FADH2 from the citric acid cycle carry electrons to the…

electron transport chain

How many ATP do glycolysis and the citric acid cycle make by substrate-level phosphorylation?

Only 4 total

What accounts for most of the energy extracted from glucose?

NADH and FADH2

Role of NADH and FADH2?

Carry electrons to the ETC, linking glycolysis/citric acid cycle to oxidative phosphorylation

Where is the ETC in eukaryotes vs prokaryotes?

Eukaryotes = inner mitochondrial membrane. Prokaryotes = plasma membrane

The ETC is mostly made of…

protein complexes (I to IV) with electron carriers

Most ETC proteins are ____ with attached ____ groups

cytochromes; heme

ETC electron carriers alternate between…

reduced and oxidized states

"Electron flow down the chain" means…

electrons drop in free energy with each transfer between carriers until they reach O2

Why break the energy drop into small steps?

To release energy in manageable amounts

Which molecule donates electrons to the ETC at the highest energy level?

NADH

Why does NADH donate at a higher energy level than FADH2?

NADH enters at Complex I (top of the chain); FADH2 enters lower, at Complex II

Role of oxygen in the ETC?

Final (terminal) electron acceptor; combines with electrons and H+ to form water

Primary path electrons travel "downhill" in aerobic respiration?

Glucose → NADH → electron transport chain → oxygen

What captures energy from the redox reactions in glycolysis and the citric acid cycle?

NADH and FADH2 (plus a little ATP)

The ETC uses energy from electron transfer to pump ____ into the ____

H+; intermembrane space

The H+ gradient across the inner mitochondrial membrane is called the…

proton-motive force (PMF)

Can H+ cross the inner mitochondrial membrane on its own?

No, the membrane is impermeable to H+

H+ can only cross back into the matrix through…

ATP synthase

ATP synthase uses the ____ flow of H+ to make ATP

exergonic (downhill)

Chemiosmosis is…

using the energy in an H+ gradient to drive cellular work (making ATP)

Immediate source of energy for ATP synthesis by oxidative phosphorylation?

The proton-motive force across the inner mitochondrial membrane

Why isn't "flow of electrons from NADH" the immediate energy source for ATP synthase?

Electron flow builds the H+ gradient; the H+ gradient (PMF) is what directly powers ATP synthase

Role of ATP synthase?

Lets H+ flow back into the matrix and uses that energy to make ATP from ADP + phosphate

2 parts of oxidative phosphorylation?

Electron transport chain and chemiosmosis

Most ATP from cellular respiration comes from…

oxidative phosphorylation

What happens without O2 (or another terminal electron acceptor)?

The ETC stops and oxidative phosphorylation stops

2 ways to make ATP without O2?

Anaerobic respiration and fermentation

Both anaerobic respiration and fermentation begin with…

glycolysis

Which uses an ETC: anaerobic respiration or fermentation?

Anaerobic respiration (fermentation doesn't)

Anaerobic respiration vs fermentation: type of phosphorylation?

Anaerobic respiration = substrate-level + oxidative. Fermentation = substrate-level only

Final electron acceptor in anaerobic respiration?

A non-O2 molecule like sulfate or nitrate

Final electron acceptor in fermentation?

An organic molecule (pyruvate or acetaldehyde)

Are anaerobic terminal acceptors more or less electronegative than O2?

Less

How does a less electronegative acceptor affect ATP yield?

Less energy is released, so less ATP is made than in aerobic respiration

Fermentation keeps making ATP by…

substrate-level phosphorylation in glycolysis

2 common types of fermentation?

Alcohol fermentation and lactic acid fermentation