Question

what is cellular respiration which types of organisms use cellular respiration to

Answer 1

Cellular respiration is the set of metabolic processes cells use to break down organic molecules (usually glucose) and convert their chemical energy into ATP, the usable energy currency of the cell. Its overall purpose is to harvest energy from food so cells can do work (movement, biosynthesis, transport, etc.).

Basic summary
- General chemical equation (aerobic): C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy (ATP).
- Main stages: glycolysis (in the cytoplasm), pyruvate oxidation, the citric acid (Krebs) cycle, and the electron transport chain with oxidative phosphorylation (in mitochondria in eukaryotes; in the plasma membrane for many prokaryotes).
- ATP yield: aerobic respiration yields roughly 30–32 ATP per glucose (varies). Anaerobic pathways yield much less (fermentation gives 2 ATP per glucose).

Types of cellular respiration
1. Aerobic respiration
- Uses oxygen as the final electron acceptor in the electron transport chain.
- High ATP yield.
- Used by most animals, plants, fungi, protists and many bacteria (obligate and facultative aerobes when oxygen is available).

2. Anaerobic respiration
- Uses a terminal electron acceptor other than oxygen (e.g., nitrate, sulfate, or carbon dioxide).
- Carried out by many bacteria and archaea (for example, some soil bacteria and sulfate-reducing bacteria).
- ATP yield is generally less than aerobic respiration but more than fermentation.

3. Fermentation (a form of anaerobic metabolism)
- Occurs when organisms regenerate NAD+ without an electron transport chain, using organic molecules as electron acceptors.
- Produces much less ATP (2 ATP/glucose).
- Examples: lactic acid fermentation in animal muscle cells and some bacteria; alcoholic fermentation in yeast.

Which organisms use cellular respiration?
- Almost all living organisms use some form of cellular respiration to get energy from nutrients.
- Animals, plants, fungi, and many protists primarily rely on aerobic respiration when oxygen is available.
- Many bacteria and archaea can perform aerobic respiration, anaerobic respiration, or fermentation depending on their species and environmental conditions.
- Examples by category:
- Obligate aerobes (require O2): many animals, some bacteria.
- Obligate anaerobes (poisoned by O2): certain bacteria like Clostridium species — use anaerobic respiration or fermentation.
- Facultative anaerobes (can use O2 but can switch to fermentation or anaerobic respiration): E. coli, yeast.
- Aerotolerant organisms (do not use O2 but tolerate it): some bacteria that ferment.

Short takeaway
- Cellular respiration is how cells extract energy from food to make ATP.
- Nearly all organisms perform it, but the specific pathway (aerobic, anaerobic, or fermentation) depends on the organism and environmental conditions.