Mitochondria Structure and Function Quiz

Study Notes

Mitochondria are organelles responsible for cellular respiration and ATP production.
They have a double membrane structure:
- Outer membrane: Contains porins that allow small molecules to pass through.
- Inner membrane: Contains proteins for oxidative phosphorylation, including ATP synthase, electron transport proteins, and transport proteins.
- Intermembrane space: The space between the inner and outer membrane, continuous with the lumen of the cristae.
- Matrix: The central compartment inside the inner membrane, contains mitochondrial DNA (mtDNA).

Inner membrane: Highly folded into cristae, which increase its surface area for ATP production.
- Cristae: Folding and tube-like invaginations of the inner membrane.
- Cristae junction: Sharp bends connecting the cristae with the boundary membrane.
Outer membrane: Contains porins that allow small molecules to pass through when open.

Located in the matrix.
Circular DNA, similar to bacterial DNA.
Codes for essential proteins for mitochondrial function, ribosomes, and transfer RNAs (tRNAs).
Most mitochondrial proteins are encoded by nuclear DNA, synthesized in the cytosol, and transported to the mitochondria.

Mitochondria are dynamic organelles, constantly changing shape, fusing, and dividing.
Fusion: The merging of two mitochondria to form a larger one.
- Ensures homogeneity within the cell.
Fission: The fragmentation of damaged or mutated mitochondrial parts.
- Facilitates cell division and allows for efficient transport to areas of high energy demand.

ATP (adenosine triphosphate): The primary energy currency of the cell.
Mitochondria are the main site of ATP production from glucose through aerobic respiration.
Glucose oxidation: The breakdown of glucose into ATP occurs in four stages:

Glycolysis: Occurs in the cytosol, produces a small amount of ATP and NADH.
Citric Acid Cycle (Krebs Cycle): Occurs in the mitochondrial matrix, produces NADH, FADH2, and some ATP.
Electron Transport Chain: Located in the inner mitochondrial membrane, uses NADH and FADH2 to generate the proton-motive force (H+ gradient across the inner mitochondrial membrane).
ATP Synthesis: Uses the proton-motive force to phosphorylate ADP into ATP via ATP synthase.

Glucose: A six-carbon sugar, central to ATP production and cellular metabolism.
Catabolic pathways: Break down molecules, such as glucose into smaller units.
Anabolic pathways: Build larger molecules from smaller units.
Glycolysis: The breakdown of glucose into two pyruvate molecules.
Pyruvate: A three-carbon sugar that enters the citric acid cycle.
Acetyl CoA: Derived from pyruvate, feeds into the citric acid cycle.
Glucose can be:
- Broken down into sugars, fats, and phospholipids.
- Synthesized into glycogen (storage protein in animals).
- Used in nucleotide synthesis.
- Used to synthesize fatty acids, phospholipids, and fats.
- Used to synthesize amino acids.

Glycolysis: 2 ATP, 2 NADH
Citric Acid Cycle: 2 ATP, 6 NADH, 2 FADH2 (plus 2 NADH from pyruvate to Acetyl CoA conversion)
Total: 4 ATP, 10 NADH, 2 FADH2
Electron Transport Chain: Uses NADH and FADH2 to generate a proton gradient across the inner mitochondrial membrane.
ATP Synthase: Utilizes the proton gradient to phosphorylate ADP into ATP, producing a large amount of ATP.