Biology Chapter 7.3

Functions of the cell membrane?

- Selectively permeable (controls what enters/exits the cell).
- Maintains homeostasis.
- Provides protection.

Structure of the cell membrane?

Phospholipid bilayer (has 2 layers of phospholipids).

Components of the phospholipid bilayer?

- Hydrophilic heads that face out towards the water.
- Hydrophobic tails that cluster inside away from water.
- Proteins.

Types of cellular transport?

- Passive transport.
- Active transport.

Define passive transport.

- Movement of molecules from one side of the membrane to the other without energy usage.
- Maintains balance in the cell (homeostasis).

Examples of passive transport?

- Diffusion.
- Facilitated diffusion.
- Osmosis.

Define diffusion (passive transport).

High concentration of solute to low concentration of solute.

Define facilitated diffusion (passive transport).

Applies to molecules that cannot directly diffuse across the membrane; protein on the cell membrane used as channels.

Define osmosis (passive transport).

- Facilitated diffusion of water specifically.
- Movement of water through cell membranes using aquaporins (water channel proteins).

Define isotonic (osmosis).

When the concentration of water is the same both inside and outside of the cell and therefore, the water particles do not need to move.

Define hypertonic (osmosis).

When the cell has more water and the outside of the cell has more solute, so the cell releases water particles to achieve balance.

Define hypotonic (osmosis).

When the cell has less water and the outside of the cell has more water than solute, so the water particles outside of the cell move into the cell.

Define osmotic pressure.

Movement of water out of or into a cell exerting a force.

For organisms to survive, what do they need to have a way to?

For organisms to survive, they must have a way to balance the intake and loss of water.

What are examples of organisms surviving by balancing their intake and loss of water?

- Plasma surrounds red blood cells.
- Water and nutrients enter plant cells through osmosis.
- When a wilted plant is watered, osmosis makes the plant firm again.

Define active transport.

The movement of particles from a low concentration to a high concentration using energy.

Examples of active transport?

- Endocytosis.
- Exocytosis.

Explain the role of protein pumps in active transport.

Protein pumps help move material across the cell membrane.

Define endocytosis (active transport).

Taking in bulky material; the word literally means "within the cells".

Define exocytosis (active transport).

Cells releasing large amounts of material from the cell; the word literally means "outside the cell".

How does endocytosis work?

- The cell comes in contact with a particle.
- The cell membrane wraps around the particle.
- Once the particle is 100% surrounded, a vesicle is formed.

How does exocytosis work?

- Large particles that must leave the cell are packaged in vesicles.
- The vesicle travels through the cell membrane and fuses with it.
- The cell releases the particle to the outside of the cell.