Chapter 7 Mastering Biology

If the concentration of phosphate in the cytosol is 2.0 mM and the concentration of phosphate in the surrounding fluid is 0.1 mM, how could the cell increase the concentration of phosphate in the cytosol?

Active Transport

What property of dishwashing liquid (detergent) makes it useful to wash grease from pans?

Amphipathic nature

In what way do the membranes of a eukaryotic cell vary?

Certain proteins are unique to each membrane.

Phospholipids vary in the small molecules attached to the phosphate group. The phospholipid shown in the figure has a _______________ attached to phosphate.

Choline Group

According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly

Embedded in a lipid bilayer

4. A phospholipid also has two "tails" made up of two ______________ molecules, which consist of a carboxyl group with a long hydrocarbon chain attached.

Fatty Acid

During osmosis, water diffuses across a selectively permeable membrane from the region of higher ____________ concentration and lower _________ concentration to the side with lower __________ concentration and higher ___________ concentration.

Free water Solute Free water soulte

Because the phosphate group and its attachments are either charged or polar, the phospholipid head is _______________, which means it has an affinity for water.

Hydrophilic

Ions

Hydrophilic Has difficulty crossing the hydrophobic part Transport protein required to cross efficiently

Polar Molecules

Hydrophilic Has difficulty crossing the hydrophobic part Transport protein required to cross efficiently

Because the C-H bonds in the fatty acid tails are relatively nonpolar, the phospholipid tails are _______________, which means they are excluded from water.

Hydrophobic

Nonpolar Molecules

Hydrophobic Can cross easily No transport protein required

If a red blood cell is placed in a salt solution and bursts, what is the tonicity of the solution relative to the interior of the cell?

Hypotonic

Describe a characteristic feature of a carrier protein in a plasma membrane?

It exhibits specificity for a particular type of molecule.

How can a lipid be distinguished from a sugar?

Lipids are mostly nonpolar.

When molecules move down their concentration gradient, they move from where they are _______________ to where they are ____________________.

More concentrated Less concentrated

Which of the following is a major difference between prokaryotic and eukaryotic cells?

Most prokaryotic cells have no internal membranes; eukaryotic cells do.

Which of the following particles could diffuse easily through a cell membrane?

Oxygen

Diffusion across a biological membrane is called ___________________.

Passive Transport

Facilitated diffusion is a type of _______.

Passive Transport

A phospholipid bilayer with equal amounts of saturated and unsaturated fatty acids displays a specific permeability to glucose. What effect will increasing the proportion of unsaturated fatty acids in the bilayer have on the membrane's permeability to glucose?

Permeability to glucose will increase.

A phospholipid has a "head" made up of a glycerol molecule attached to a single______________, which is attached to another small molecule.

Phosphate Group

What kinds of molecules pass through a cell membrane most easily?

Small and hydrophobic

What are least likely to diffuse through the phospholipid bilayer of a cell membrane?

Small ions

What is an explanation for why unsaturated fatty acids help keep a membrane more fluid at lower temperatures?

The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.

How do membrane phospholipids interact with water?

The polar heads interact with water; the nonpolar tails do not.

What factor does not affect membrane permeability?

The polarity of membrane phospholipids

In facilitated diffusion, what is the role of the transport protein?

Transport proteins provide a hydrophilic route for the solute to cross the membrane.

True or false? Osmosis is a type of diffusion.

True

True or false? The water-soluble portion of a phospholipid is the polar head, which generally consists of a glycerol molecule linked to a phosphate group.

True

What happens when two solutions separated by a selectively permeable membrane reach osmotic equilibrium?

Water molecules move between the two solutions, but there is no net movement of water across the membrane.

What cannot rapidly pass directly through the phospholipids of the plasma membrane?

Water, Glucose, hydrogen ion

What tends to increase membrane fluidity?

a greater proportion of unsaturated phospholipids

What molecule dramatically increases the rate of diffusion of water across cell membranes?

aquaporins

The movement of glucose into a cell against a concentration gradient is most likely to be accomplished by which of the following?

cotransport of the glucose with a proton or sodium ion that was pumped across the membrane using the energy of ATP hydrolysis

What is least likely to be important in holding the components of a biological membrane together?

covalent interactions between the phospholipid and protein components of the membrane

The membranes of winter wheat are able to remain fluid when it is extremely cold by ________.

increasing the proportion of unsaturated phospholipids in the membrane

What membrane activities requires energy from ATP hydrolysis?

movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid

A sodium-potassium pump ________.

moves three sodium ions out of a cell and two potassium ions into a cell using energy from ATP hydrolysis

Hydrophobic substances like salad oil are

nonpolar molecules that repel water molecules.

Passive transport includes

osmosis, facilitated diffusion and transport of an ion down its electrochemical gradient

The permeability of a biological membrane to a specific polar solute depends primarily on which of the following?

the types of transport proteins in the membrane

The permeability of a biological membrane to a specific polar solute may depend on?

the types of transport proteins in the membrane

Describe the structure of a biological membrane?

two layers of phospholipids with proteins either crossing the layers or on the surface of the layers