Transport Through

Membranes

I. Plasma membrane

A. Flexible boundary between cell and its environment.

B. Selective Permeability – allows certain molecules to pass through while keeping others out.

C. Phospholipid Bilayer

1. Glycerol backbone.

2. Two fatty acid chains.

3. Phosphate group.

4. Two phospholipid layers.

II. Types of transport

A. Passive transport.

1. Requires no energy, as in

a.Simple diffusion

b.Facilitated diffusion

c.Osmosis

2. Moves materials

a.From higher concentrations

b.To lower concentrations

3. Solutions.

a.Hypertonic

1)Has higher concentration of salt, sugar, etc.

2)Causes cells to release water (lose mass).

b.Hypotonic

1)Has lower concentration of salt, sugar, etc.

2)Causes cells to absorb water (gain mass).

c. Isotonic

1)Has same concentration of salt, sugar, etc.

2)Cells balance absorbing and releasing water (same mass).

Hypotonic Hypertonic Isotonic

or or or

Hypertonic or Hypotonic or Isotonic?

Hypertonic or Hypotonic or Isotonic?

Hypertonic or Hypotonic or Isotonic?

Hypertonic or Hypotonic or Isotonic?

III. Active transport.

A. Requires

1. Energy

2. Transport Proteins

B. Moves materials

1. From lower concentrations

2. To higher concentrations

IV.Proteins - involved in both passive diffusion and active diffusion.

A.Protein channels create “tunnels” that don’t require energy. (left picture)

B.Carrier proteins require energy. (right picture)

V. Endocytosis – large materials into cell

VI. Exocytosis – wastes expelled