Definition
A cell is the basic structural and functional unit of all living organisms. Cells contain specialized structures called organelles, each performing specific functions necessary for the cell's survival and operation.
Main Parts of a Cell and Their Functions
- Cell Membrane:
- Controls the movement of substances in and out of the cell.
- Provides protection and structural support.
- Cytoplasm:
- Jelly-like fluid where organelles are suspended.
- Site of many metabolic reactions.
- Nucleus:
- Contains genetic material (DNA).
- Controls cell activities by regulating gene expression.
- Mitochondria:
- Site of cellular respiration.
- Produces energy in the form of ATP.
- Ribosomes:
- Synthesize proteins from amino acids.
- Endoplasmic Reticulum (ER):
- Rough ER: Studded with ribosomes; synthesizes and transports proteins.
- Smooth ER: Synthesizes lipids and detoxifies chemicals.
- Golgi Apparatus:
- Modifies, sorts, and packages proteins and lipids for secretion or use within the cell.
- Lysosomes (mainly in animal cells):
- Contain digestive enzymes to break down waste and cellular debris.
- Chloroplasts (in plant cells):
- Site of photosynthesis, converting light energy into chemical energy.
- Cell Wall (in plant cells, fungi, and some bacteria):
Worked Example
Question:
Which organelle is responsible for producing most of the cell's energy, and what is the main process called?
Solution:
The mitochondria are responsible for producing most of the cell's energy. The main process is called cellular respiration, represented by the equation:
$$ \text{C}_6\text{H}_{12}\text{O}_6 + 6 \text{O}_2 \rightarrow 6 \text{CO}_2 + 6 \text{H}_2\text{O} + \text{ATP} $$