B4: Mitochondria

What are mitochondria?

Small organelles in all eukaryotic cells that convert energy.

How are mitochondria inherited?

Maternally, through the cytoplasm of the egg.

Is mitochondrial inheritance Mendelian?

No, it is non-Mendelian.

What does the term 'mitochondrion' mean?

From Greek 'mitos' (thread) and 'chondrion' (granule).

Why are mitochondria called the 'powerhouse of the cell'?

They are energy-converting organelles that produce ATP.

Are mitochondria autonomous organelles?

They are semi-autonomous.

What type of DNA do mitochondria contain?

Circular mitochondrial DNA (mtDNA).

What proportion of mitochondrial proteins are encoded by mtDNA?

About 2.5%.

What theory explains the origin of mitochondria?

Endosymbiont theory.

What organism are mitochondria thought to have originated from?

An ancestral α-proteobacterium.

How many membranes do mitochondria have?

Two: an outer and an inner membrane.

What are cristae?

Invaginations of the inner mitochondrial membrane.

What process occurs on the inner mitochondrial membrane?

Oxidative phosphorylation.

What is found in the mitochondrial matrix?

Enzymes of the TCA cycle and mitochondrial DNA.

Where does ATP synthesis occur in mitochondria?

At ATP synthase on the inner mitochondrial membrane.

What drives ATP synthase?

A proton (H⁺) electrochemical gradient.

What generates the proton gradient?

The electron transport chain.

What provides electrons to the electron transport chain?

NADH and FADH₂.

Where are NADH and FADH₂ produced?

In the TCA cycle.

What is the final electron acceptor in the electron transport chain?

Oxygen (O₂).

What happens if oxygen is unavailable?

The electron transport chain backs up and ATP production ceases.

What is chemiosmosis?

ATP synthesis driven by the flow of protons through ATP synthase.

What is the proton-motive force?

The combined charge and concentration gradient of protons.

How many major protein complexes form the electron transport chain?

Four complexes (I-IV), plus cytochrome c and coenzyme Q.

What does complex IV of the electron transport chain do?

Transfers electrons to oxygen to form water.

How does cyanide affect mitochondria?

It inhibits complex IV and stops aerobic ATP production.

What is meant by mitochondrial plasticity?

Mitochondria can change in structure and distribution in cells.

What is the overall role of mitochondria in metabolism?

To generate ATP using energy from NADH and FADH₂ via oxidative phosphorylation.