BIO181 chapter 3

How does the fluid-mosaic model describe bilayers?

• Polar heads of phospholipids face inward and nonpolar tails face outward

• molecules are in constant movement

• A rigid double-layer of phospholipids

• proteins carbohydrates, and other lipids interact with the bilayer

What molecule is circled within the bilayer?

• phospholipid

• carbohydrate

• cholesterol

• protein

In what ways can individual phospholipids move within a bilayer?

• diffusion across bilayer

• lateral movement

• rotation in place

• Exchange of phospholipids between the two membranes

Ability of molecules and ions to cross the membrane

• diffusion

• permeability

• fluidity

• lateral movement

Membranes with higher fluidity are more permeable

• True

• False

A lipid bilayer with made of unsaturated fatty acids is less permeable

• True

• False

Factors that increase fluidity and permeability

• short fatty acid tails

• compact fatty acids within a membrane

• low temperature

• unsaturated fatty acids

Is cholesterol polar or nonpolar?

• polar

• nonpolar

Long fatty acid tails decrease permeability

• True

• False

How does temperature affect permeability of a membrane?

• High temperatures increases length of fatty acid tails

• Phospholipids become more fluid with energy from heat

• High temperature increases unsaturated fatty acids which leads to higher permeability

• Phospholipids have less energy from low temperatures and experience less movement