Bio: Ch. 7

Drag the terms on the left to the appropriate blanks on the right to complete the sentences.

1. A phospholipid has a "head" made up of a glycerol molecule attached to a single phosphate group, which is attached to another small molecule. 2. Phospholipids vary in the small molecules attached to the phosphate group. The phospholipid shown in the figure has a choline group attached to phosphate. 3. Because the phosphate group and its attachments are either charged or polar, the phospholipid head is hydrophilic, which means it has an affinity for water. 4. A phospholipid also has two "tails" made up of two fatty acidmolecules, which consist of a carboxyl group with a long hydrocarbon chain attached. 5. Because the C-H bonds in the fatty acid tails are relatively nonpolar, the phospholipid tails are hydrophobic, which means they are excluded from water.

Structure A (red triangle) is a _____. The figure shows a cell membrane with integral molecule, which consists of two similar parts with specific recess. There are many particles in the extracellular fluid. One of these particles is labeled A.

solute

Part complete If the pores in the selectively permeable membrane became larger, but still not large enough to let the sugar pass through, what would happen during osmosis in the U-shaped tube compared to what is shown in the figure?

the final water levels would be the same as shown in the figure, but the solutions would reach near equal concentrations faster

An animal cell lacking carbohydrates on the external surface of its plasma membrane would likely be impaired in which function?

cell-cell recognition

Endocytosis moves materials _____ a cell via _____.

into ... membranous vesicles

Facilitated diffusion is a type of _______.

passive transport

Which of the following statements about the conditions shown in the U-shaped tube are true?

-water is tightly clustered around the hydrophilic solute molecules on both sides of the membrane -there is less free water in the right arm of the tube than in the left arm of the tube

You are working on a team that is designing a new drug. For this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule selectively enters the target cells?

the similarity of the drug molecule to other molecules that are transported into the target cells

If more sugar were added to the solution on the left side of the tube, what would happen to the water level on the right side of the tube?

the water level would go down

Structure B is a _____. The figure shows a cell membrane with integral molecule marked B, which consists of two similar parts with specific recess. There are many particles in the extracellular fluid.

transport protein

1. Extracellular Fluid 2. Plasma Membrane 3. Cytoplasm

1. a. hydrophilic e. hydrophilic c. hydrophilic 2. f. hydrophobic 3. b. hydrophilic d. hydrophilic g. hydrophilic

Which of the following statements correctly describes osmosis?

In osmosis, water moves across a membrane from areas of lower solute concentration to areas of higher solute concentration.

Which of the following statements describes a characteristic feature of a carrier protein in a plasma membrane?

It exhibits specificity for a particular type of molecule.

Why are lipids and proteins free to move laterally in membranes?

There are only weak hydrophobic interactions in the interior of the membrane.

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

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

In this diagram of the plasma membranes of two adjoining cells, identify the protein indicated by the white arrow, including its function.

a receptor protein that binds with a signaling molecule and relays the message into the cell by activating other molecules inside the cell

In many animal cells, the uptake of glucose into the cell occurs by a cotransport mechanism, in which glucose is cotransported with Na+ ions.

a. glucose low b. decrease in glucose and Na+ -Na+ moves down its electrochemical gradient -Glucose moves against its concentration gradient c. glucose high

According to the fluid mosaic model of cell membranes, phospholipids _____.

can move laterally along the plane of the membrane

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

Drag the terms on the left to the appropriate blanks on the right to complete the sentence. Terms may be used more than once.

during osmosis, water diffuses across a selectively permeable membrane from the region of higher free water concentration and lower solute concentration to the side with lower free water concentration and higher solute concentration

This cell is in a(n) _____ solution

hypertonic

You know that this cell is in a(n) _____ solution because it _____.

hypertonic solution ... lost water

The majority of solutes that diffuse across the plasma membrane cannot move directly through the lipid bilayer. The passive movement of such solutes (down their concentration gradients without the input of cellular energy) requires the presence of specific transport proteins, either channels or carrier proteins. Diffusion through a transport protein in the plasma membrane is called facilitated diffusion. Sort the phrases into the appropriate bins depending on whether they are true only for channels, true only for carrier proteins, or true for both channels and carriers.

only channels: -provide a continuous path across the membrane -allow water molecules and small ions to flow quickly across the membrane only carriers: -undergo a change in shape to transport solutes across the membrane -transport primarily small polar organic molecules both: -transport solutes down a concentration or electrochemical gradient -are integral membrane proteins -provide a hydrophilic path across the membrane

What name is given to the process by which water crosses a selectively permeable membrane?

osmosis

Which of the following processes includes all of the others?

passive transport

Which of the following types of molecules are hydrophilic and therefore excluded from the hydrophobic portion of the phospholipid bilayer?

peripheral membrane proteins

1. Non-polar 2. Polar 3. Ions

1. a. hydrophobic b. crosses lipid bilayer easily c. no transport protein required 2. a. hydrophilic b. has difficulty crossing the lipid bilayer, the hydrophobic part c. transport protein required to cross efficiently 3. a. hydrophilic b. has difficulty crossing the lipid bilayer, the hydrophobic part c. transport protein required to cross efficiently

Drag the labels onto the table to indicate when each statement is true. Labels can be used once, more than once, or not at all. 1. Orange dye moves independently or purple dye. 2. Concentration gradients exist that drive diffusion of both dyes. 3. There is a net movement of orange dye from side A to side B. 4. Purple dye moves only from side B to side A. 5. There is no net movement of purple dye.

1. always 2. only before equilibrium is reached 3. only before equilibrium is reached 4. never 5. only at equilibrium

Which of the following statements is TRUE with regard to this animation?

Both sodium and potassium ions are transported against their concentration gradients.

Sort the phrases into the appropriate bins depending on whether they describe exocytosis, endocytosis, or both.

exocytosis: -increases the surface area of the plasma membrane -requires fusion of vesicles with the plasma membrane -secretes large molecules out of the cell endocytosis: -decreases the surface area of the plasma membrane -forms vesicles from inward folding of the plasma membrane both: -requires cellular energy -transported substances never physically cross the plasma membrane

You know that this cell is in a(n) _____ solution because the cell _____.

hypotonic ... swelled

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

Some solutes are able to pass directly through the lipid bilayer of a plasma membrane, whereas other solutes require a transport protein or other mechanism to cross between the inside and the outside of a cell. The fact that the plasma membrane is permeable to some solutes but not others is what is referred to as selective permeability. Which of the following molecules can cross the lipid bilayer of a membrane directly, without a transport protein or other mechanism? Select all that apply.

oxygen lipids water carbon dioxide

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 white blood cell engulfing a bacterium is an example of _____.

phagocytosis

White blood cells engulf bacteria using _____.

phagocytosis

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

small and hydrophobic

You can recognize the process of pinocytosis when _____.

the cell is engulfing extracellular fluid

Which of the following statements correctly describe(s) the driving forces for diffusion of Na+ and K+ ions through their respective channels? Select all that apply

-The diffusion of K+ ions out of the cell is impeded by the electrical gradient across the plasma membrane. -The electrochemical gradient is larger for Na+ than for K+. -The diffusion of Na+ ions into the cell is facilitated by the Na+ concentration gradient across the plasma membrane.

Which statements about the fluid mosaic structure of a membrane are correct? Select the three correct statements.

-because membranes are fluid, membrane proteins and phospholipids can drift about in the membrane -the framework of a membrane is a bilayer of phospholipids with their hydrophilic heads facing the aqueous environment inside and outside of the cell and their hydrophobic tails clustered in the center -the diverse proteins found in and attached to membranes perform many important functions

All cells contain ion pumps that use the energy of ATP hydrolysis to pump ions across the plasma membrane. These pumps create an electrochemical gradient across the plasma membrane that is used to power other processes at the plasma membrane, including some transport processes. In animal cells, the main ion pump is the sodium-potassium pump.

Active transport by the sodium-potassium pump follows this cycle. 1. Three Na+ ions from the cytosol bind to the pump. 2. The binding of Na+ stimulates the phosphorylation of the pump protein by ATP. 3. Phosphorylation causes a conformational change in the pump that moves the three Na+ ions against their concentration gradient and releases them outside the cell. 4. The release of the Na+ ions permits two K+ ions from outside the cell to bind to the pump, and the phosphate group is released. 5. Release of the phosphate group causes another conformational change in the pump. 6. The conformational change in the pump moves the two K+ ions against their concentration gradient and releases them into the cytosol.