Draw neat labelled diagram of cell. Explain in detail transport of substances across plasma membrane?

The diagram of a cell is as follows:

```
_______________________
| |
| Nucleus |
|_______________________|
| |
| Cytoplasm |
|_______________________|
| |
| Cell Membrane |
|_______________________|
```

Transport of substances across the plasma membrane can occur through two main processes: passive transport and active transport.

1. Passive transport:
- Diffusion: Small, non-polar molecules such as oxygen and carbon dioxide can passively diffuse across the plasma membrane from an area of high concentration to an area of low concentration. This process does not require energy.
- Facilitated diffusion: Larger or polar molecules such as glucose or ions can pass through the plasma membrane with the help of transport proteins. This process also does not require energy.

2. Active transport:
- Active transport involves the movement of molecules against their concentration gradient, from an area of low concentration to an area of high concentration. This process requires energy in the form of ATP.
- Examples of active transport include the sodium-potassium pump, which pumps sodium ions out of the cell and potassium ions into the cell, and the proton pump, which pumps protons across the membrane.

Overall, the plasma membrane regulates the movement of substances into and out of the cell, maintaining the cell's internal environment and allowing for proper cellular function.

Diagram of a Cell:

[Image of a cell with labeled components]

Components:

- Plasma membrane: Selectively permeable boundary
- Cytoplasm: Gel-like fluid inside the cell
- Nucleus: Control center of the cell
- Mitochondria: Energy generators of the cell
- Ribosomes: Protein synthesis factories
- Endoplasmic reticulum (ER): Protein and lipid synthesis
- Golgi apparatus: Packaging and distribution center
- Vacuoles: Storage compartments
- Lysosomes: Waste disposal units

Transport of Substances Across Plasma Membrane:

The plasma membrane is a selectively permeable barrier, meaning it allows certain substances to pass through while blocking others. There are several mechanisms by which substances can cross the plasma membrane:

1. Passive Transport:

- Diffusion: Movement of particles from an area of high concentration to an area of low concentration.
- Osmosis: Diffusion of water across a selectively permeable membrane.
- Facilitated diffusion: Diffusion aided by transmembrane proteins or channels.

2. Active Transport:

- Movement of particles against their concentration gradient, requiring energy from ATP.
- Primary active transport: Direct use of ATP to pump substances across the membrane.
- Secondary active transport: Combined use of ATP and the concentration gradient of another substance to transport substances.

3. Vesicular Transport:

- Endocytosis: Substances enter the cell by engulfing them in membrane vesicles.
- Phagocytosis: Engulfing solid particles or cells.
- Pinocytosis: Engulfing small droplets of liquid.
- Exocytosis: Substances are released from the cell by fusing vesicles with the plasma membrane.

Specific Transport Proteins:

The plasma membrane contains various transport proteins that facilitate the movement of specific substances:

- Carrier proteins: Bind to substances and transport them across the membrane.
- Channel proteins: Form pores through the membrane, allowing substances to passively diffuse.
- Pumps: Primary active transport proteins that move substances against their concentration gradient.

Regulation of Transport:

The rate of transport across the plasma membrane is tightly regulated to maintain cellular homeostasis. Factors affecting transport include:

- Concentration gradients
- Availability of energy
- Number and activity of transport proteins
- Hormonal and environmental signals