B2.1: Membranes and membrane transport

Are the heads of phospholipids polar or non-polar?

Polar

Are the tails of phospolipids polar or non-polar?

Non-polar

Amphipathic molecule

Has both a polar and a non-polar region

What is the barrier between the hydrophilic and hydrophobic molecules in a phospholipid?

Glycerol

Types of protein usually present in a cell membrane

• Hormone binding

• Enzymatic

• Cell adhesion

• Cell-to-cell recognition

• Channel proteins

• Pumps for active transport

Which type of transport achieves equilibrium?

Passive

Hypertonic solution

Higher concentration of solutes

Hypotonic solution

Lower concentration of solutes

Isotonic solution

Solutions are in equilibrium

Aquaporins

Protein channels that allow water to pass through during osmosis

Proteins needed for facilitated diffusion

Carrier proteins and channel proteins

Carrier proteins

Change shape to carry a specific substance (usually ions) either against or down the concentration gradient

Channel proteins

Open and close their channels to allow a specific water soluble substance (usually an ion) to pass through the membrane.

Why do cells need active transport?

To maintain a different concentration of a certain molecule inside the cell vs outside

In which cells is the sodium-potassium pump extra important?

Neurons

Amphipathic molecules exp.

• Phospholipids

• Cholesterol

How do active transport pumps work?

The pump accepts a molecule from one side of the membrane, and 2 ATP are used to change to conformation of the pump so it opens on the other side, releasing the molecule to the other side of the membrane. The pump then reverts spontaneously to its original conformation.

What do glycoproteins and glycolipids facilitate?

Ecll adhesion and cell-to-cell recognition

What element of active transport pumps makes them good for their function?

Their asymmetrical structure