Cell membrane

What is the primary mechanism for ATP production in eukaryotic cells?

Oxidative phosphorylation in the mitochondria (yielding ~26-28 ATP out of ~30-32 total ATP per glucose)

Where is the ATP-generating machinery located in prokaryotic cells?

In the plasma membrane

What structural feature allows the outer mitochondrial membrane to pass ions and small molecules?

Porins

Which mitochondrial compartment is highly selective and contains the Electron Transport Chain (ETC) and ATP synthase?

The inner mitochondrial membrane

What accumulates in the intermembrane space during electron transport?

Hydrogen ions (H+ / protons)

Where are the enzymes for the Citric Acid Cycle (Krebs cycle), mtDNA, and mitochondrial ribosomes located?

The mitochondrial matrix

What functional advantage do cristae provide to mitochondria?

They increase the surface area of the inner membrane, allowing for more ETC complexes and ATP synthase, thereby increasing ATP production capacity

Why do cardiac muscle cells have approximately 3 times more cristae than liver cells?

Because cardiac muscle cells have a significantly higher energy/ATP demand

Who proposed the chemiosmotic coupling hypothesis in 1961?

Peter Mitchell

What is the direction of proton pumping performed by the Electron Transport Chain (I-IV)?

From the mitochondrial matrix into the intermembrane space

What powers ATP synthase (Complex V) to generate ATP from ADP and inorganic phosphate (Pi)?

The flow of protons (H+) down their electrochemical gradient back into the matrix

What are the two components of the proton motive force created across the inner mitochondrial membrane?

1. pH gradient (ΔpH) — matrix is basic (higher pH), intermembrane space is acidic (lower pH) | 2. Voltage gradient (ΔV) — matrix is relatively negative, intermembrane space is relatively positive

What is the final electron acceptor in the Electron Transport Chain, and at which complex does it act?

Oxygen (O2), at Complex IV (combining with H+ to form water)

What happens to mitochondrial respiration if oxygen is absent?

Electron transport halts -> proton pumping stops -> proton gradient dissipates -> oxidative ATP synthesis ceases

What is the net ATP yield per glucose molecule produced in Glycolysis, the Citric Acid Cycle, and Oxidative Phosphorylation?

Glycolysis: 2 net ATP | Citric Acid Cycle: 2 ATP (or GTP) | Oxidative Phosphorylation: 26-28 ATP (Total: ~30-32 ATP)

What event ~2 billion years ago is described by the Endosymbiotic Theory?

A primitive eukaryotic cell engulfed an aerobic bacterium, establishing a symbiotic relationship that evolved into the mitochondrion

What are four key pieces of evidence supporting the bacterial origin of mitochondria?

1. Own circular double-stranded mtDNA | 2. Bacterial-like 70S ribosomes | 3. Double membrane structure | 4. Independent replication by binary fission

How do mitochondria contribute to NADPH generation for biosynthetic pathways like lipid synthesis?

When nutrients are abundant, mitochondria export citrate to the cytosol, where it is converted into NADPH

What mitochondrial protein released from the intermembrane space triggers apoptosis (programmed cell death)?

Cytochrome c

How do mitochondria regulate cytosolic calcium (Ca2+) levels?

They buffer cytosolic Ca2+ to help regulate cellular signaling processes like muscle contraction and hormone secretion