ap biology - chapter 7 mastering biology

Which of the following allows water to move much faster across cell membranes?

Aquaporins -A channel protein in a cellular membrane that specifically facilitates osmosis, the diffusion of free water across the membrane.

Which component is a glycolipid?

B

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

Choline group

Which component is a peripheral protein?

D

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

Hypotonic ... swelled -A cell will gain water when placed in a hypotonic solution.

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

Increasing the percentage of unsaturated phospholipids in the membrane

Endocytosis moves materials _____ a cell via _____.

Into ... membranous vesicles -The prefix "endo-" means "inward."

Cell membranes are asymmetrical. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature?

The two sides of a cell membrane face different environments and carry out different functions.

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

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

Which line in the graph represents the bag with the highest initial concentration of sucrose?

A

Refer to the figure. If you examine side A after three days, you should find _____.

A decrease in the concentration of NaCl and a decrease in the water level. -Water moves from high water potential to low water potential, meaning, water will move toward the more negative value. -Solute exerts a "pull" on water, so the water is going to move toward the higher concentration of glucose; both of the NaCls are going to try to reach a state of equilibrium, so Side A will lose a small amount of NaCl while Side B will gain a small amount of NaCl.

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

A only (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.

Nonpolar molecules (examples: hydrocarbons, O2, CO2) How does phospholipid structure relate to the selective permeability of the plasma membrane?

A. hydrophobic B. can cross easily C. no transport protein required

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

Amphipathic nature -Detergents form micelles around the grease, which are then washed away because the polar head groups facing outward on the micelle are water-soluble.

For a protein to be an integral membrane protein, it would have to be _____.

Amphipathic, with at least one hydrophobic region -Integral membrane proteins are transmembrane proteins that have at least one hydrophobic region that anchors them to the hydrophobic core of the phospholipid bilayer. Some stick only partway into the membrane, while others stretch from one side of the membrane to the other and are exposed on either side. The portions of an integral membrane protein found inside the membrane are hydrophobic, while those that are exposed to the cytoplasm or extracellular fluid tend to be hydrophilic.

Which line or lines in the graph represent(s) bags that contain a solution that is hypertonic at 50 minutes?

B -A hypertonic solution is a solution with a high amount of solute present in a region; refers to a solution that, when surrounding a cell, will cause the cell to lose water.

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

Both sodium and potassium ions are transported against their concentration gradients. -Both ions are transported from where their concentration is low to where their concentration is high, and the cell expends energy in the form of ATP to do it.

Which line in the graph represents the bag that contained a solution isotonic to the 0.6 M solution at the beginning of the experiment?

C -Isotonic solution means the same amount of solute present as the other region (looking for the bag that had no mass change because there was no net movement of water).

Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?

CO2

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

Can move laterally along the plane of the membrane -The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids.

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

Cell-cell recognition -Some glycoproteins serve as identification tags that are specifically recognized by membrane proteins of other cells. -Glycoproteins contain oligosaccharide chains (glycans) covalently attached to amino acid side-chains. The carbohydrate is attached to the protein.

Singer and Nicolson's fluid mosaic model of the membrane proposed that membranes_____.

Consist of protein molecules embedded in a fluid bilayer of phospholipids -Fluid mosaic model envisions membrane of protein molecules drifting laterally in a fluid bilayer of phospholipids.

The sodium-potassium pump is called an electrogenic pump because it _____.

Contributes to the membrane potential

Which of the following 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 -This is not an important interaction because there are rarely covalent bonds between the phospholipids and integral membrane proteins.

Polar molecules (examples: water, sugars) How does phospholipid structure relate to the selective permeability of the plasma membrane?

D. hydrophilic E. have difficulty crossing the hydrophobic part F. transport protein required to cross efficiently

Which component is cholesterol?

E

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

Fatty acid

Ions (examples: Na+, K+, Ca2+, Cl-) How does phospholipid structure relate to the selective permeability of the plasma membrane?

G. hydrophilic H. have difficulty crossing the hydrophobic part I. transport protein required to cross efficiently

Identify Structure A.

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

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

Hydrophilic

The plasma membrane figure.

Hydrophilic: a, b, e, and g Hydrophobic: f -Phospholipids make up the main fabric of the plasma membrane. In the plasma membrane, the phospholipids are found in a bilayer. The hydrophilic heads are exposed to the aqueous environments of the cytoplasm and extracellular fluid, and the hydrophobic tails are sandwiched within, sheltered from these aqueous environments.

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

Hydrophobic

This cell is in a(n) _____ solution.

Hypertonic -There is a greater concentration of solute outside the cell.

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

Hypertonic solution ... lost water -A cell will lose water when placed in a hypertonic solution.

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.

Celery stalks that are immersed in fresh water for several hours become stiff. Similar stalks left in a 0.15 M salt solution become limp. From this we can deduce that the fresh water_____.

Is hypotonic and the salt solution is hypertonic to the cells of the celery stalks. -Plant cells want a hypotonic environment so the cell is able to become turgid (very firm). As water moves into the cell and the large central vacuole fills up with water, the cell wall and vacuole push against each other and create turgor pressure. This pressure helps the plant stand upright, while also helping with stability and rigidity.

Refer to the figure. Initially, in terms of tonicity, the solution in side A with respect to the solution in side B is _____.

Isotonic -An isotonic solution is a solution with the same amount of solute present as another region; causes no net movement of water into or out of the cell.

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 membrane activities requires energy from ATP?

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

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

Osmosis -Osmosis is the passive transport of water.

From the data given, which statement most accurately describes what is occurring in response to a particular unknown solution?

Osmosis of water molecules from unknown solution A likely caused the increase in mass observed.

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

Oxygen (O2) -Small nonpolar molecules such as oxygen can diffuse across cell membranes.

Diffusion across a biological membrane is called _____________.

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.

Which of these are NOT embedded in the hydrophobic portion of the lipid bilayer at all?

Peripheral proteins -Found on the outside and inside surfaces of membranes, attached either to integral proteins or to phospholipids. Peripheral membrane proteins do NOT stick into the hydrophobic core of the membrane, and they tend to be more loosely attached.

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

Phagocytosis -Phagocytosis occurs when a cell engulfs a large particle.

A phospholipid has a "head" made up of a glycerol molecule attached to a single ________________, which is attached to another small molecule. Reviewing phospholipid structure

Phosphate group

Structure of a phospholipid.

Phospholipid -Phospholipids have a hydrophilic head and hydrophobic tails. -The hydrophilic head includes a glycerol molecule attached to a single phosphate group, which is then attached to another small molecule. The phosphate group and its attachments are either polar or charged. Water molecules are polar and therefore are attracted to these charged regions of the phospholipid head. -The hydrophobic tails are two fatty acids attached to the glycerol molecule of the head. Water molecules are not attracted to the tails because C-H bonds are relatively nonpolar and therefore do not result in charged regions in the tails.

Identify Structure D.

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

Structure of the plasma membrane.

Plasma membrane -Phospholipids form the main fabric of the plasma membrane. One feature of phospholipids is that when they are placed in an aqueous solution, they will self-assemble into a double layer (bilayer) that resembles the bilayer of the plasma membrane. This self-assembly occurs because phospholipids are hydrophilic at one end (the phospholipid head) and hydrophobic at the other end (the phospholipid tails).

Proton pumps are used in various ways by members of every domain of organisms: Bacteria, Archaea, and Eukarya. What does this most probably mean?

Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life.

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

Small and hydrophobic

Structure A is a _____.

Solute -A solute is crossing the plasma membrane.

What is the function of Structure E?

Stabilization of the phospholipids -Cholesterol helps to stabilize the structure of the plasma membrane.

You can recognize the process of pinocytosis when _____.

The cell is engulfing extracellular fluid. -Pinocytosis is "cell drinking."

A patient was involved in a serious accident and lost a large quantity of blood. In an attempt to replenish body fluids, distilled water equal to the volume of blood lost is added to the blood directly via one of his veins. What will be the most probable result of this transfusion?

The patient's red blood cells will swell and possibly burst because the blood has become hypotonic compared to the cells. -A hypotonic solution is a solution with a low solute amount in a region; refers to a solution that, when surrounding a cell, will cause the cell to take up water.

How does phospholipid structure prevent certain molecules from crossing the plasma membrane freely?

The structure of the plasma membrane makes it selectively permeable, enabling it to regulate the transport of substances into and out of the cell. -Small, nonpolar molecules are hydrophobic, so they can easily cross the phospholipid bilayer of the plasma membrane. -Polar molecules and ions are hydrophilic, so they cannot very easily cross the hydrophobic portion of the plasma membrane (formed by the phospholipid tails). Water is an unusual molecule because, despite the fact that it is polar, it is small enough to pass directly through the hydrophobic interior of the lipid bilayer, albeit slowly. -Polar molecules and ions generally cross the plasma membrane with the help of transport proteins. For example, water crosses the bilayer rapidly via transport proteins called aquaporins.

The permeability of a biological membrane to a specific polar solute may depend 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. -Binding site fits a particular substrate.

When a cell is in equilibrium with its environment, which of the following occurs for substances that can diffuse through the cell?

There is random movement of substances into and out of the cell.

Structure A in the figure is a(n) _____.

Transport protein -The protein is allowing solute molecules to enter the cell.

Structure B is a _____.

Transport protein -The transport protein facilitates the movement of solute across the plasma 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. -This is the most general description of facilitated diffusion by membrane transport proteins.

True or false? Osmosis is a type of diffusion.

True -Osmosis is the diffusion of water across a selectively permeable 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.

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

Three lab groups carried out an experiment to identify the correct molarities for five solutions. Each unknown contained one of the following sucrose concentrations: 0.0 M, 0.2 M, 0.4 M, 0.6 M, 0.8 M, and 1.0 M. Each data entry represents the average of 3 sample replications of 1 cm3 sweet potato cubes expressed as percent change in mass after an overnight (24 hr) soak in the unknown solutions.

experiment data

Five dialysis bags constructed of membrane, which is permeable to water and impermeable to sucrose, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed) and the percent change in mass of each bag was graphed

percent change in mass graph