MB ch 7 Bio 1107

Identify Structure A.

- (Structure A is composed of both a carbohydrate and a protein.)

Biologists use the fluid mosaic model to describe membrane structure.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. -The kinky tails of some proteins help keep the membrane fluid by preventing the component molecules from packing solidly together. -Membranes include a mosaic, or mix, of carbohydrates embedded in a phospholipid bilayer.

-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.

Which statement is correct? A. The contents of a red blood cell are hypertonic to distilled water. B. A solution of distilled water is hypotonic .C. A solution of seawater is hypertonic.

-The contents of a red blood cell are hyperosmotic to distilled water. (The red blood cell has a greater solute concentration than distilled water, which means that its contents are hypertonic to distilled water.)

Which of these can RAPIDLY pass directly through the phospholipids of the plasma membrane, without the help of a transport protein?

-lipid soluble molecule -(Small, nonpolar, lipid-soluble molecules can pass rapidly through the phospholipids of the plasma membrane. Ions, such as hydrogen ions, and hydrophilic molecules, such as water and glucose, cannot rapidly pass directly through the phospholipids of the membrane. To move rapidly through the membrane, they must pass through membrane transport proteins.)

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 -co2 -lipids -water

Identify Structure D.

-phospholipid bilayer of membrane (Phospholipids can be recognized by the presence of a head and two tails.)

cell membrane permeability

-selectively permeable -fluid mosaic model-- phospholipid bilayer with proteins embedded throughout -hydrophilic heads facing out, hydrophobic fatty acid tails facing inwards -lipid bilayer permeable to small, nonpolar (O2) and polar molecules (H2O) -small charged particles can cross through protein channels -larger, charged molecules need carrier proteins

What is the function of Structure E?

-stabilization of the phospholipids (Cholesterol helps to stabilize the structure of the plasma membrane.)

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 the target cells have transport proteins that specifically bind to certain molecules, they may bind with and transport a drug that is similar in structure.)

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. Orange dye moves independently or purple dye Always 2. Concentration gradients exist that drive diffusion of both dyes only before equilibrium is reached 3. There is a net movement of orange dye from side A to side B only before equilibrium is reached 4. Purple dye moves only from side B to side A Only at equilibrium

hypotonic solution

A solution in which the concentration of solutes is less than that of the cell that resides in the solution

______________ transport requires energy, usually in the form of ATP hydrolysis, to move substances against their concentration gradient

Active

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 (For the cell to accumulate phosphate, it must move calcium against the concentration gradient. This process requires energy.)

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

Amphipathic nature

__________ facilitate the diffusion of water

Aquaporins

________________ facilitate water movement across membranes and thus speed up the process of osmosis.

Aquaporins

Select the correct statement about osmosis. A. If a dead cell is placed in a solution hypotonic to the cell contents, osmosis will not occur. B. Osmotic equilibrium cannot be reached unless solute concentrations equalize across the membrane. C. Osmosis is the diffusion of water molecules across a selectively permeable membrane.

C. Osmosis is the diffusion of water molecules across a selectively permeable membrane. (Osmosis and diffusion are fundamentally similar processes.)

All proteins involved in active transport are __________ proteins

Carrier

In what way do membranes vary among eukaryotic cells?

Certain proteins are unique to each membrane.

_______________ proteins provide corridors that allow a specific molecule or ion to cross the membrane

Channel

Because the membrane serves different functions on the cytoplasmic and exterior surfaces, the structure and composition of the surfaces must be __________.

Different

Osmosis

Diffusion of water through a selectively permeable membrane

In ____________ the cell takes in macromolecules by forming vesicles from the plasma membrane

Endocytosis

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 (The salt concentration in the solution is lower than it is in the cell, so water enters the cell, causing it to burst.)

_____________ consist of diverse proteins suspended in and attached to a phospholipid bilayer. Kinks in the unsaturated fatty acid tails of some phospholipids keep the membrane fluid, and a mosaic of proteins perform a variety of functions.

Membranes

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

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

Water molecules are constantly in motion and will continually move across the membrane. However, when the solutions are in equilibrium, there is _____ net movement across the membrane.

NOT

Hydrophobic substances like salad oil are

Nonpolar molecules that repel the water molecules

__________ is the control of solute concentrations and water balance, is a necessary adaptation for life in such environments

Osmoregulation

____________ is the diffusion of water across a selectively permeable membrane

Osmosis

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

Oxygen (Small nonpolar molecules such as oxygen can diffuse across cell membranes.)

____________ transport occurs without the input of cellular energy. Some solutes are transported into the cell while others are transported out of the cell.

Passive Transport

_______________ occurs when a cell engulfs a large particle.

Phagocytosis

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

Phagocytosis (Phagocytosis occurs when a cell engulfs a large particle.)

The relative concentrations of solutes and free water on either side of the membrane determines the amount of osmosis, but the size of the _______ determines how fast osmosis occurs.

Pores

Which of the following statements is true regarding potential energy?

Potential energy is the energy possessed by matter due to its location or structure.

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

Receptor protein

hypertonic solution

Solute concentration is greater than that inside the cell; cell loses water

How do membrane phospholipids interact with water?

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

Which of the following statements about osmosis is correct?

The presence of aquaporins (proteins that form water channels in the membrane) should speed up the process of osmosis. (Aquaporins facilitate water movement across membranes and thus speed up the process of osmosis.) In facilitated diffusion, what is

-Phagocytosis ("cellular eating") -Pinocytosis ("cellular drinking") -Receptor-mediated endocytosis all relate to ?

The three types of endocytosis

the _________ _______ ___ __________ Depends on its concentration of solutes that cannot cross the plasma membrane relative to the concentration of solutes inside the cell

Tonicity of a solution

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

Transport

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

True (The hydrophilic, or water-loving, portion of a phospholipid is the polar head, whereas the hydrophobic portion is the nonpolar tail.)

True or false? Osmosis is a type of diffusion.

True (Osmosis is the diffusion of water across a selectively permeable membrane.)

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.

Which of the following molecular movements is due to diffusion or osmosis?

When a plant cell is placed in concentrated salt water, water moves out of the cell. (if the salt water is hypertonic to the plant cell's contents, water moves out of the cell by osmosis, a form of diffusion.)

Which of the following factors would tend to increase membrane fluidity?

a greater proportion of unsaturated phospholipids

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

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

____________ ___________ attach to the extracellular matrix and cytoskeleton, help support the membrane, can coordinate external and internal changes

attachment proteins

Active and passive transport of solutes across a membrane typically differ in which of the following ways?

b) Active transport always involves the utilization of cellular energy, whereas passive transport does not require cellular energy.

carriers and channels

both: -transport solutes down a concentration or electrochemical gradient -are integral membrane proteins -provide a hydrophilic path across the membrane

Large molecules such as proteins ___________ pass through the lipid bilayer.

cannot

Transport proteins include channel proteins and __________ proteins

carrier

Which of the following is least likely to be important in holding the components of a biological membrane together? A. hydrophobic interactions among the fatty acid tails of phospholipids on the same side of the membrane B. hydrophobic interactions between the phospholipid tails and the surface of integral membrane proteins buried in the membrane C. polar interactions among the phospholipid head groups on the same surface of the membrane D. hydrophobic interactions among the fatty acid tails of phospholipids on opposite sides of the membrane E. covalent interactions between the phospholipid and protein components of the membrane

covalent interactions between the phospholipid and protein components of the membrane (This is not an important interaction because there are rarely covalent bonds between the phospholipids and integral membrane proteins.)

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

embedded in a lipid bilayer.

Exocytosis and _____________ temporarily change the surface area of the plasma membrane. (The fusion or budding of transport vesicles at the plasma membrane either adds or removes proteins and phospholipids, thus changing the surface area.)

endocytosis

Active and passive transport can be distinguished by whether or not they use cellular ______________.

energy

If a plant cell and its surroundings are isotonic, there is no net movement of water into the cell; the cell becomes _____________

flaccid (limp)

Endocytosis moves materials _____ a cell via _____.

into ... membranous vesicles (The prefix "endo-" means "inward.")

The ____________ proteins can be found either embedded in or attached to the surface of the phospholipid bilayer.

membrane

When molecules move down their concentration gradient, they move from where they are __________ to where they are ____________ .

more concentrated to less concentrated

The cytoplasmic side of the membrane is ________ in charge relative to the extracellular side

negative

Carriers

only carriers: -undergo a change in shape to transport solutes across the membrane -transport primarily small polar organic molecules

channels

only channels:-provide a continuous path across the membrane-allow water molecules and small ions to flow quickly across the membrane

during __________, 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

osmosis

Facilitated diffusion is still ____________ because the solute moves down its concentration gradient, and the transport requires no energy

passive

Diffusion across a biological membrane is called ________ __________

passive transport

Which of the following processes includes all others? A)diffusion of a solute across a membrane B)diffusion of a solute across a membrane C)facilitated diffusion D)transport of an ion down its electrochemical gradient E) osmosis

passive transport

Facilitated diffusion is a type of _______.

passive transport (During facilitated diffusion, the cell is not expending energy to move the particles across the membrane; therefore, facilitated diffusion is a form of passive transport.)

In _______________ , a cell engulfs a particle in a vacuole. The vacuole fuses with a lysosome to digest the particle

phagocytosis

In _______ , molecules dissolved in droplets are taken up when extracellular fluid is "gulped" into tiny vesicles

pinocytosis

in a hypertonic environment, plant cells lose water. The membrane pulls away from the cell wall, causing the plant to wilt, a potentially lethal effect called ________________

plasmolysis

Structure A is _____.

solute (A solute is crossing the plasma membrane.)

isotonic solution

solutes outside or cell are equal to the inside of cell

You can recognize the process of pinocytosis when _____.

the cell is engulfing extracellular fluid (Pinocytosis is "cell drinking.")

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

Which of the following statements about a typical plasma membrane is correct?

the two sides of the plasma membrane have different lipid and protein composition

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 lipid bilayer will be impermeable or very poorly permeable to polar or charged solutes. The presence of the correct transport protein will determine the permeability.)

The _________ protein facilitates the movement of solute across the plasma membrane..

transport

Structure A in the figure is a(n) _____. *look at picture*

transport protein (The protein is allowing solute molecules to enter the cell.)

A plant cell in a hypotonic solution swells until the wall opposes uptake; the cell is now _____________

turgid (firm)

Which of the following best describes the structure of a biological membrane?

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

Large molecules, such as polysaccharides and proteins, cross the membrane in bulk via ___________. Which requires energy

vesicles