Plasma Membrane and Membrane Permeability Study Guide

What are the structures of phospholipids?

A. Phosphate Group

B. Glycerol

C. Hydrophilic Head

D. Hydrophobic Tails

Why are the heads of phospholipids hydrophilic?

Because they contain a negatively charged phosphate group, which makes them polar (attracted to water)

What does a Plasma Membrane do?

Separates internal cell environment from external environment

What are Plasma Membranes comprised of?

Primarily phospholipids

Phospholipid Info:

1. Are Amphipathic

2. Have both hydrophilic & hydrophobic regions

3. Forms a bilayer

What are polar hydrophilic heads (phosphate regions) oriented towards?

Aqueous Environments

Where do nonpolar hydrophobic tails (fatty acid regions) face?

Away from aqueous environments

The hydrophobic interior causes the membrane to be?…

Selectively Permeable

What is a Fluid Mosaic Model?

A model to describe the structure of cell membranes

What happens in the fluid?

The membrane is held together by weak hydrophobic interactions and can therefore move & shift

What does temperature affect?

Fluidity

What temperature do unsaturated hydrocarbon tails help maintain fluidity at?

Low Temperatures

What does high temperature do?

Reduces Movement

What does low temperature do?

Reduces tight packing of phospholipids

What is a Mosaic comprised of?

Many Macromolecules

What are the two major categories of proteins?

1. Integral Proteins

2. Peripheral Proteins

What are integral proteins?

Proteins embedded into the lipid bilayer

Integral proteins can be:

1. Hydrophilic

2. Hydrophobic

3. Both

What are integral proteins determined by?

R groups (side chains)

What does hydrophilic mean?

Charged or Polar (side chains)

What do hydrophilic regions make up?

The interior of the channel or pore

What are hydrophilic regions exposed to?

Cytosol

What does hydrophobic mean?

Nonpolar (side chains)

What do hydrophobic regions make up?

The protein surface

What do hydrophobic regions interact with?

Fatty acids on the interior of the membrane

What are peripheral proteins?

Proteins that are hot embedded into the lipid bilayer

What are peripheral proteins loosely bonded to?

The Surface

What are membrane carbohydrates?

Important for cell-to-cell recognition (most abundant)

What are Glycolipids?

Carbohydrates bonded to lipids

What are Glycoproteins?

Carbohydrates bonded to proteins

What is Selective Permeability?

The ability of membranes to regulate the substances that enter and exit

What is the reason for Selective Permeability?

Due to hydrophobic interior (has nonpolar hydrophobic tails)

What allows a substance to easily cross the membrane?

Being small nonpolar + hydrophobic tails (Hydrocarbons, CO2, O2, N2)