BIO 181: Chapter 5

Transport that requires a cell to expend some of its own energy, typically from ___, is called ____ transport.

1. ATP 2. active

Choose all functions typically carried out by membrane proteins.

1. Attach the membrane to the cytoskeleton. 2. Connect adjacent cells and hold them together. 3. Receive external chemical messages.

All. Cell membranes contain a phospholipid ____ which provides a flexible matrix and a barrier to ___.

1. Bilayer 2. Permeability

The following substances all move across the plasma membrane of red blood cells by diffusion. Which ones move by facilitated diffusion?

1. Glucose 2. Bicarbonate ions 3. Chloride ions

Choose the 3 groups of lipids found in eukaryotic cells.

1. Glycerol phospholipids 2. Sphingolipids 3. Sterols

Which of the following is true of cations?

1. Have a positive electric charge. 2. Have an unequal number of protons and electrons

Identify the 4 main components of all eukaryotic membranes.

1. Lipid bilayer 2. Transmembrane proteins 3. Interior protein network 4. Cell-surface markers

The two solutions shown in this diagram are separated by a selectively permeable membrane that allows water to pass through freely but prevents the passage of urea. Before equilibrium is reached, which of the following statements are true?

1. Net movement of water across the membrane is toward the left. 2. The water level will rise on the left side of the U-tube 3. The solution on the left is hypertonic.

Which of the following will occur if a cell is placed in a hypotonic solution?

1. Net movement of water into the cell 2. The cell will tend to swell

Which region of the phospholipid molecule is hydrophilic?

1. Phosphate group 2. Polar of charged molecule attached to the phosphate group

Water is attracted to which kinds of solutes, forming hydration shells around them?

1. Polar 2. Charged

How does lipid composition affect membrane fluidity?

1. Sphingolipids tend to make the membrane less fluid. 2. Saturated fatty acids tend to make the membrane less fluid because they pack together well.

If a cell is placed in a hypertonic solution what occurs?

1. The cell will tend to shrink. 2. Net movement of water is out of the cell.

Some membrane proteins are attached to the surface of the membrane by special molecules that associate strongly with phospholipids. Which of the following describes the anchoring molecules?

1. They are modified lipids. 2. They have chemical bonding domains that link them directly to the membrane proteins.

Select the statements that are true about ions and how they interact with membranes and their components.

1. They are repelled by the hydrophobic interior of the lipid bilayer. 2. They interact well with polar molecules.

Which of the following statements about ion channels are true?

1. They are used to transport ions across the membrane. 2. Some can be opened or closed in response to a specific stimulus.

Which of the following are key functions carried out by membrane proteins?

1. Transport specific ions and molecules across the membrane 2. Function as cell-surface identity markers 3. Receive external chemical messages. 4. Catalyze specific chemical reactions on the surface of the membrane.

Select the accurate statements concerning membrane fluidity.

1. Unanchored proteins are relatively free to move laterally w/in the membrane. 2. Phospholipids are relatively free to move laterally w/in the membrane.

The ____ transport of sodium and potassium ions from areas of ____ concentration to areas of ____ concentration requires more than 1/3 of all energy expended by a non-dividing animal cell.

1. active 2. lower 3. higher

Of the 2 types of transport proteins that mediate facilitated diffusion, _____ proteins actually bind with the substance being transported, while ____ proteins simply provide a hydrophilic space for the substance to move through.

1. carrier 2. channel

Ions that carry an overall positive charge are called ____ while those that carry an overall negative charge are called ____.

1. cations 2. anions

Many substances that are repelled by the hydrophobic interior of the lipid bilayer can readily diffuse across the plasma membrane with the help of specific ______ proteins or _______ proteins. These transporter proteins are typically transmembrane proteins.

1. channel 2. carrier

The lack of double bonds in phospholipids with saturated fatty acids allow them to pack together tightly, and therefore the membrane is ___ fluid. Kinks introduced by double bonds in lipids with unsaturated fatty acids prevent them from packing together tightly, and therefore the membrane is ___ fluid.

1. less 2. more

cellular _____ are said to be selectively _____ because they allow some substances to pass through easily while other substances pass through very slowly or not at all.

1. membrane 2. permeable

The combined concentration of all solutes in a solution determines the ____ ____ of the solution.

1. osmotic 2. concentration

Although a eukaryotic cell membrane can contain many different lipids, they can be classified in three groups: glycerol phospholipids, ___ and ___.

1. sphingolipids 2. sterols

Compared to the ER membrane, the plasma membrane contains more ______.

1. sphingomyelin 2. cholesterol 3. phosphatidylcholine

When phospholipids are placed in water, they spontaneously form which of the following?

A bilayer

Oxygen diffuses across the plasma membrane due to which of the following?

All oxygen molecules are in constant random motion.

The movement of water across the plasma membrane is facilitated by specialized water channels called _____.

Aquaporins

Which of the following best describes the relationship between solute concentration and rate of diffusion during facilitated diffusion by carrier proteins?

As solute concentration increases, the rate of diffusion increases but eventually it remains constant once it reaches a maximum rate.

Why are bacterial cells less likely than animal cells to burst in a hypotonic solution?

Bacterial cells have strong cell walls.

Why do ions need membrane transport proteins to help them cross the plasma membrane?

Because they are charged.

Net movement of a substance from a region where it has a higher concentration to a region where it has a lower concentration is called which of the following?

Diffusion

What type of microscope can be used to see the 2 phospholipid layers in a plasma membrane?

Electron

Which of the following is not 1 of 4 main components of all plasma membranes?

Extracellular matrix

When a channel protein or carrier protein assists in diffusion, which of the following is observed?

Facilitated diffusion.

Which region of a phospholipid molecule is hydrophobic?

Fatty acid hydrocarbon chains

Cells continually exchange materials and information with their environment. This exchange is crucial____.

For all the processes occurring in a cell.

Which method of microscopy, commonly used to study lipid bilayers, was used to produce this image?

Freeze-facture microscopy

Which of the following describes passive transport?

It does not require an expenditure of energy by the cell itself.

Which of the following accurately describes the hydrostatic pressure inside a cell if it is transferred from a hypertonic environment to a hypotonic environment?

It will increase.

How do carrier proteins differ from channel proteins?

Only carrier proteins actually bind to the substance being transported.

The lipid bilayer that forms the core of all cell membranes is composed of _____.

Phospholipids

Which of the following makes up the bilayer of every cell membrane?

Phospholipids

Which of the following can relatively easily move laterally within the plasma membrane?

Phospholipids and unanchored proteins

The top part of a phospholipid bilayer, is...

Polar or charged. Hydrophilic

Which component of the plasma membrane is responsible for the transport of materials and communication across the membrane?

Proteins

Which of the following transmembrane proteins are likely to be found in membranes that form tubular structures?

Reticulons

Plasma membranes allow some substances to pass through easily while other substances only pass through very slowly or not at all. For that reason, plasma membranes are said to be ______.

Selectively permeable

Substances that cannot easily cross the lipid bilayer can still diffuse across the plasma membrane with the help of which of the following?

Specific channel proteins or carrier proteins.

The ER membrane is typically thinner and more fluid than the plasma membrane and it contains more curvature. Why?

The ER membrane contains mainly unsaturated phospholipids.

Diffusion is caused by which of the following?

The constant motion of all atoms and molecules.

When phospholipids are placed in water, they spontaneously form a bilayer. Why?

The polar heads on the surface of the bilayer interact with water, while the nonpolar tails in the interior of the bilayer do not come into contact with water.

Which of the following is a defining feature of biological membranes?

The presence of two phospholipid sheets

This diagram shows two solutions separated by a membrane that allows water to pass through freely but prevents the passage of urea. Before equilibrium is reached, which statement is true?

The solution on the right has a higher concentration of free water molecules.

If two solutions have unequal concentrations of solutes, which one will be considered hypertonic?

The solution with lower solute concentration

During facilitated diffusion, how do carrier proteins transport solutes across the membrane?

They bind specifically to the solute being transported.

What is the function of transmembrane proteins called reticulons?

They can cause a membrane to bend or even form a tube.

Which of the following accurately describes the functions of transmembrane proteins?

They can transport molecules across the membrane. They transmit information into the cell.

Which of the following is true of channel proteins?

They have a hydrophilic interior through which polar molecules can pass.

How do red blood cells promote the movement of glucose into the cell?

They phosphorylate glucose after it enters the cell in order to maintain a steep concentration gradient for unphosphorylated glucose.

Which of the following is one of the main functions of the membrane's phospholipid bilayer?

To impose a barrier to permeability

Select the statement that is true of transmembrane domains.

Transmembrane domains are composed of hydrophobic amino acids.

What is the name of carrier proteins that transport a single type of molecule or ion?

Uniporters

Which of the following best describes the ability of water to move across a lipid bilayer membrane, such as the plasma membrane?

Water can move across the lipid bilayer, but the flow is limited.

If you compare two aqueous solutions which differ in the amount of solutes dissolved, the aqueous solution with a higher concentration of solutes will have ______.

a lower concentration of free water molecules

Transport proteins that actually bind to the specific substance being transported across the membrane are called _____ proteins.

carrier

Transport proteins that have a hydrophilic interior space with an aqueous environment through which specific substances can move across the membrane in either direction are called _____ proteins.

channel

Ion _____ have a hydrated interior that spans the membrane and allows ions to diffuse through.

channels

The red blood cell carrier that transports bicarbonate ions in one direction transports ______ ions in the opposite direction.

chloride

If a cell is transferred from a hypotonic environment to a hypertonic environment, the hydrostatic pressure inside the cell will ______.

decrease

Due to the constant random motion of its atoms and molecules, a substance will exhibit net movement from a region where it has a higher concentration to a region where it has a lower concentration. This net movement is called _____.

diffusion

Each membrane-spanning region of a transmembrane protein is called a transmembrane _____

domain

Diffusion that is assisted by a channel protein or a carrier protein is called _____ diffusion.

facilitated

An aqueous solution with a lower concentration of solutes will have a _____ concentration of free water molecules.

higher

Water is attracted to charged or polar solutes, forming _____ shells around them.

hydration

If two solutions have the same concentration of solutes (all solutes), they are ____ solutions.

isotonic

Membrane proteins can be anchored to the surface of the membrane by attachment to molecules that associate strongly with phospholipids and insert into the lipid bilayer. These molecules are ______.

modified lipids

The lower part of this molecule, which contains two very long chains of carbon atoms (18 C atoms in each), is ______.

nonpolar hydrophobic

The diffusion of water across a selectively permeable membrane is called _____.

osmosis

Transport that occurs without a cell expending any of its own energy is called ____ transport.

passive

Red blood cells add a(n) ____ group to any entering glucose molecule, which prevents the glucose from passing back across the membrane.

phosphate

Which of the following are typical components of biological membranes?

proteins and lipids

During facilitated diffusion by carrier proteins, when solute concentrations are low, increasing the solute concentration causes a linear increase in the rate of diffusion. However, at high solute concentrations, further increases in the solute concentration no longer increase the rate of diffusion. This means that carrier proteins exhibit ______.

saturation

The osmotic concentration of a solution is determined by the combined concentration of all _____ in the concentration.

solutes

In an aqueous solution the solvent is _____.

water

Osmosis occurs when there is a selectively permeable membrane and it refers to the diffusion of ______.

water

The most abundant molecule in the cytoplasm is the ____ molecule.

water