Transport Across cell Membranes

Simple diffusion

The net movement of molecules from a region of high concentration to a region of low concentration

Simple Diffusion: Active or Passive

passive process

Equilibrium

A state where concentration is the same in both regions.

Rate of diffusion

How long to reach equilibrium

Factors influencing diffusion rate (3)

Surface area (Increased surface area will increase the rate of diffusion)
Concentration gradient (Increased Concentration gradient will increase the rate)

Distance (increased distance will decrease the rate of diffusion)

Molecules moved by simple diffusion (3)

Oxygen, carbon dioxide, and lipids can move across the membrane by simple diffusion.

Facilitated diffusion

The process using integral membrane proteins as channels to transport materials from high to low concentration.

facilitated diffusion: active or passive?

passive process

Molecules transported by facilitated diffusion (3)

Monosaccharides, amino acids, and ions (K+, Na+, Cl-) are transported via facilitated diffusion.

Active transport

The process of moving molecules from a region of low concentration to a region of high concentration using energy.

Requirements in active transport (2)

Active transport requires

• energy in the form of ATP.

• membrane pumps (integral proteins)

Membrane pumps in active transport

Integral proteins, such as Na+/K+ pumps and Cl- pumps, are used in active transport.

Transported molecules in active transport

Monosaccharides, amino acids, and ions (K+, Na+, Cl-) can be moved by active transport.

Osmosis

The diffusion of water molecules across a semipermeable barrier from high to low concentration.

osmosis: active or passive

passive process

Endocytosis

The process of moving bulk material into the cell, which includes phagocytosis and pinocytosis.

Phagocytosis

A type of endocytosis known as 'cell eating'.

Pinocytosis

A type of endocytosis known as 'cell drinking'.

Exocytosis

The process of moving bulk material out of the cell.