Module 4 Cell Membrane Bilayer

Which of the following statements about cholesterol molecules are false? A. They help hold a membrane together. B. They alter the fluidity of the membrane. C. They attach to carbohydrates. D. They transport ions across membranes. E. They disrupt membrane function. F. All of these are true of cholesterol molecules.

A, C, D and E

How are temperature and fluidity of the cell membrane related?

Across a broad temperature range, fluidity of the cell membrane decreases as temperature decreases.

Complete the following sentence: In biological membranes, the phospholipids are ...

Arranged in a bilayer, with the fatty acids pointing toward each other.

Complete the following sentence: The hydrophilic regions of a membrane protein are most likely...

Exposed on the surface of the membrane.

Closing protein channels makes the plasma membranes of winter wheat extremely cold so they are able to remain fluid.

False

Lipids are the compounds in biological membranes that form a barrier to the movement of hydrophilic materials across the membrane.

False

True or False: Closing protein channels makes the plasma membranes of winter wheat extremely cold so they are able to remain fluid.

False

True or False: During the winter, there are no changes in lipid composition in hibernating animals.

False

Which of the following is the primary element of biological membranes?

Lipids

Which of the following changes would make a cell membrane more fluid?

Lower the cholesterol content in the cell membrane.

Complete the following sentence: The plasma membranes of winter wheat are able to remain fluid when it is extremely cold by...

Replacing saturated fatty acids with unsaturated fatty acids.

A species of fish spends part of its life cycle under conditions of moderate temperatures and part of its life cycle under extremely cold conditions. What change in the cell membranes of this fish might be expected to occur as conditions shift from moderate to extremely cold temperatures?

The fish's cells would slow production of cholesterol and increase production of unsaturated, short chain fatty acids.

Why does the cell membrane's fluidity change with its composition?

The noncovalent interactions between the molecules that make up the cell membrane change.

Complete the following sentence: Plasma membranes are relatively impermeable to water-soluble molecules because...

Their bilayer is comprised of phospholipids.

Which of the following is the reason why plasma membranes are impermeable to water-soluble molecules

Their bilayer is comprised of phospholipids.

Which of the following statements about hydrophilic regions of a membrane is true?

They are exposed on the surface of the membrane.

Houseplants adapted to indoor temperatures may die if they are left outdoors, because in a cold environment their membranes lack adequate fluidity.

True

Which statement is true about the change of cell membranes of a hibernating animal change in colder temperatures?

Unsaturated fatty acids make up more of the lipid composition.

Fill in the blank: ___________ are the compounds in biological membranes that form a barrier to the movement of hydrophilic materials across the membrane

lipids

Phospholipids are important components of ________.

the plasma membrane of animal cells

True or False: The hydrophilic regions of a membrane protein are most likely exposed on the surface of the membrane.

true