The difference between respiration and combustion is related to respiration being

Options

A. Multistep
B. Enzyme controlled
C. Intracellular
D. All the above

Answer

### Step-by-Step Solution:

1. **Definition of Respiration and Combustion**:
- Respiration is a biochemical process that occurs in all living cells. It is essential for energy production in organisms.
- Combustion is a physio-chemical process that can occur outside of living organisms and involves the burning of substances.

**Hint**: Remember that respiration is vital for life, while combustion is a chemical reaction that can happen in various environments.

2. **Rate of Reaction**:
- Respiration is a slow process where energy is released gradually.
- Combustion is a fast process where energy is released in a single, rapid step.

**Hint**: Think about how quickly you can feel the heat from a fire compared to the gradual energy release from food digestion.

3. **Energy Release**:
- In respiration, energy is released and stored as ATP (adenosine triphosphate).
- In combustion, most of the energy is released as heat.

**Hint**: ATP is like a battery for cells, while combustion produces immediate heat energy.

4. **Enzyme Activity**:
- Respiration involves various enzymes that facilitate the biochemical reactions.
- Combustion does not require enzymes and cannot be controlled by them.

**Hint**: Enzymes are like workers that help carry out tasks in cells, but combustion happens without any helpers.

5. **Oxygen Usage**:
- In respiration, oxygen acts as an oxidant in the final steps of the process.
- In combustion, oxygen is directly consumed as a reactant.

**Hint**: Consider how we breathe in oxygen for respiration versus how fire consumes oxygen to burn.

6. **Temperature Conditions**:
- Respiration occurs at normal body temperatures.
- Combustion requires high temperatures to initiate and sustain the reaction.

**Hint**: Think about how our bodies function at a stable temperature, while fire needs heat to exist.

7. **Conclusion**:
- The differences between respiration and combustion can be summarized as:
- Respiration is a multi-step process, enzyme-controlled, and intracellular.
- Combustion is a fast, non-enzyme controlled, and occurs at high temperatures.

**Final Answer**: All of the above differences highlight how respiration is distinct from combustion.