Biology IB Chapter 1.4

Higher concentration gradient difference, bigger surface area, higher temperature means faster passive transport

• Movement along concentration gradient
• 1.chemical diffusion
• 2. facilitated diffusion
• 3. osmosis

Non-Polar molecules travel through the phospholipid bilayer naturally.

Polar molecules or ions travel through specific channel proteins. Cells can control which type of channel protein to produce, so they can facilitate the diffusion of specific molecules. They can be voltage gated (like potassium channels in nerve cells) Carrier proteins can also change shape to accomplish the task. Simply put: proteins make diffusion easier.

Is the passive movement of water. Occurs because of a difference between solute concentrations on either side of a partially permeable membrane.

deplasmosis (less solute environment, gets larger)

plasmosis (more solute environment, gets smaller)

A nerve impulse involves rapid movements of sodium and then potassium ions across the axon membrane.

Potassium ions bond to a shell of water molecules when dissolved so they can’t pass through pores.

The potassium briefly bonds with a series of amino acids to lose its shell, passes through and gets its shell again.

The gate opens when there are more positively charged ions inside.

Is not only against the concentration gradient, but is also against the electronegativity gradient.

3 Na+ attach themselves to the pump. 1 P out of the ATP causes the pump to change its shape.

 

3 Na+ are released, 2 K+ attach themselves, causing the P to leave. The pump reverts back to its original shape

active transport


Portion of the plasma membrane is pinched off to enclose macromolecules or particles.

excretion and secretion of macromolecules

Entry of macromolecules