Biology Chapter 7
The internal solute concentration of a plant cell is about 0.8M. To demonstrate plasmolysis, it would be necessary to suspend the cell in what solution?
1.0M
Which of the following substances would be most likely to pass through the plasma membrane without the help of a transport protein?
A nonpolar molecule, such as a hydrocarbon
Which of these can RAPIDLY pass directly through the phospholipids of the plasma membrane, without the help of a transport protein? https://session.masteringbiology.com/problemAsset/1100510/14/0705q.jpg
A only
Why is energy required for active transport?
Because it moves solutes against their concentration gradient
If a red blood cell and a plant cell were placed in seawater, what would happen to the two types of cells?
Both cells would lose water; the red blood cell would shrivel, and the plant plasma membrane would pull away from the cell wall.
You know that this cell is in a(n) _____ solution because it _____. https://session.masteringbiology.com/problemAsset/1100512/14/0711q.jpg
C) hypertonic solution ... lost water (A cell will lose water when placed in a hypertonic solution.)
Structure B is a _____. https://session.masteringbiology.com/problemAsset/1100513/12/0714q.jpg
C) transport protein (The transport protein facilitates the movement of solute across the plasma membrane..)
What function do carbohydrates fulfill in the plasma membrane?
Cell-to-cell recognition
For the following question, match the labeled component of the cell membrane in the figure with its description https://session.masteringbiology.com/problemAsset/1834514/1/0201.jpg
D
This cell is in a(n) _____ solution. https://session.masteringbiology.com/problemAsset/1100512/14/Picture1100512b.jpg
D) hypertonic (There is a greater concentration of solute outside the cell.)
Which of these statements describes some aspect of facilitated diffusion?
Facilitated diffusion of solutes may occur through channel or transport proteins in the membrane.
Which of the following statements about diffusion is true?
It is a passive process.
When a plant cell, such as one from a rose stem, is submerged in a very hypotonic solution, what is likely to occur?
The cell will become turgid.
Red blood cells contain approximately a 2% concentration of solutes. A red blood cell is placed into a solution that contains a 4% concentration of solutes to which the cell is not permeable. What will happen to the red blood cell?
The cell will decrease in size as water flows out of it.
Which of the following factors does not affect membrane permeability?
The polarity of membrane phospholipids
Which of the following is correct regarding peripheral proteins?
These proteins are found only on the surface of the plasma membrane.
Which of the following is correct regarding integral proteins?
These proteins exhibit both hydrophilic and hydrophobic properties.
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
True or false? Osmosis is a type of diffusion
True (Osmosis is the diffusion of water across a selectively permeable membrane.)
In the 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 IMAGE ON FILE (7.1)
According to the fluid mosaic model of cell membranes, phospholipids _____.
can move laterally along the plane of the membrane
Which of the following molecules is most likely to passively diffuse across the plasma membrane?
carbon dioxide
In facilitated diffusion, __________ proteins provide openings in the plasma membrane for substances to flow through without changing structure, and __________ proteins allow passage of substances through the plasma membrane after undergoing a subtle change in shape
channel; carrier
Identify Structure A. https://session.masteringbiology.com/problemAsset/1100509/8/0703q.jpg
glycoprotein
The voltage across a membrane is called the ____
membrane potential
Which of the following cell structures exhibits selective permeability between a cell and its external environment?
the plasma membrane
The plasma membrane exhibits selective permeability. This means that __________.
the plasma membrane allows some substances to flow through it more easily than others
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
Structure A in the figure is a(n) (?)
transport protein
The sodium-potassium pump __________.
transports sodium ions out of the cell and transports potassium ions into the cell
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.
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. always 2. only before equilibrium is reached 3. only before equilibrium is reached 4. never 5. only at equilibrium IMAGE ON FILE (7.2)
Which of the following plant cells would exhibit the most turgor pressure?
A cell placed in a hypotonic solution
Which of the following would be least likely to diffuse through a plasma membrane without the help of a transport protein?
A large polar molecule
What name is given to the process by which water crosses a selectively permeable membrane?
A) osmosis (Osmosis is the passive transport of water.)
Structure A is a _____. https://session.masteringbiology.com/problemAsset/1100513/12/0713q.jpg
A) solute (A solute is crossing the plasma membrane.)
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). v glucose v Na+ C). Glucose high D). 1.down 2.against IMAGE (7.4)
Which of the following is a correct difference between active transport and facilitated diffusion?
Active transport requires energy from ATP, and facilitated diffusion does not.
What property of dishwashing liquid (detergent) makes it useful to wash grease from pans?
Amphipathic nature
How does cholesterol affect membrane fluidity?
At body temperature, it makes the membrane less fluid.
You know that this cell is in a(n) _____ solution because the cell _____. https://session.masteringbiology.com/problemAsset/1100512/14/0709q.jpg
B) hypotonic ... swelled (A cell will gain water when placed in a hypotonic solution.)
Cells A and B are the same size, shape, and temperature, but cell A is metabolically less active than cell B; cell B is actively converting oxygen to water in cellular respiration. Oxygen will diffuse more rapidly into cell __________ because __________.
B; the diffusion gradient in cell B is steeper
A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. These molecules probably enter the cells lining the baby's digestive tract via which process?
Endocytosis
Which of the following processes and organelle(s) accounts for the replacement of lipids and proteins lost from the plasma membrane?
Exocytosis and smooth and rough ER
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
Sort the phrases into the appropriate bins depending on whether they describe exocytosis, endocytosis, or both.
IMAGE 7.6
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
IMAGE ON FILE (7.5)
Which of the following is true of osmosis?
In osmosis, water moves across a membrane from areas of lower solute concentration to areas of higher solute concentration
How can a lipid be distinguished from a sugar?
Lipids are mostly nonpolar.
Which of the following statements concerning carbohydrates associated with the plasma membrane is correct?
Membrane carbohydrates function primarily in cell-cell recognition.
Which of the following particles could diffuse easily through a cell membrane?
Oxygen (O2)
Which of the following statements about passive transport is correct?
Passive transport permits the solute to move in either direction, but the net movement of the population of solute molecules occurs down the concentration gradient of the molecule.
Which of the following molecules are most abundant in the plasma membrane?
Phospholipids
Which of the following statements about the role of phospholipids in the structure and function of biological membranes is correct?
Phospholipids for a selectively permeable structure.
Which of the following structural arrangements of the components in biological membranes facilitates the cell membrane's property of selective permeability?
Proteins embedded in two layers of phospholipids
How does the "fluid mosaic model" describe the structure of the plasma membrane?
Proteins in the membrane contribute to the mosaic quality of the membrane while the lateral and rotational movements of phospholipids contribute to its fluidity.
Because ions carry a charge (positive or negative), their transport across a membrane is governed not only by concentration gradients across the membrane but also by differences in charge across the membrane (also referred to as membrane potential). Together, the concentration (chemical) gradient and the charge difference (electrical gradient) across the plasma membrane make up the electrochemical gradient. Consider the plasma membrane of an animal cell that contains a sodium-potassium pump as well as two non-gated (always open) ion channels: a Na+ channel and a K+ channel. The effect of the sodium-potassium pump on the concentrations of Na+ and K+ as well as the distribution of charge across the plasma membrane is indicated in the figure below.
The diffusion of Na+ ions into the cell is facilitated by the Na+ concentration gradient across the plasma membrane 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+
https://session.masteringbiology.com/problemAsset/1834564/1/0205.jpg Human immunodeficiency virus (HIV) infects cells that have both CD4 and CCR5 cell surface molecules. The viral nucleic acid molecules are enclosed in a protein capsid, and the protein capsid is itself contained inside an envelope consisting of a lipid bilayer membrane and viral glycoproteins. One hypothesis for viral entry into cells is that binding of HIV membrane glycoproteins to CD4 and CCR5 initiates fusion of the HIV membrane with the plasma membrane, releasing the viral capsid into the cytoplasm. An alternative hypothesis is that HIV gains entry into the cell via receptor-mediated endocytosis, and membrane fusion occurs in the endocytotic vesicle. To test these alternative hypotheses for HIV entry, researchers labeled the lipids on the HIV membrane with a red fluorescent dye. What would be observed by live-cell fluorescence microscopy immediately after HIV entry if HIV is endocytosed first, and then later fuses with the endocytotic vesicle membrane?
The red fluorescent dye-labeled lipids will appear in the infected cell's interior.
A cell is placed into a solution and the cell shrinks. Which of the following is true regarding the solution?
The solution is hypertonic.
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
All cells have voltages across their membranes. This voltage is called a(n) __________ and is often maintained by __________.
membrane potential; electrogenic pumps
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.
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 IMAGE ON FILE (7.3)
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.
oxygen lipids water carbon dioxide
Facilitated diffusion is a type of (?)
passive transport
White blood cells engulf bacteria using _____.
phagocytosis
Identify Structure D. https://session.masteringbiology.com/problemAsset/1100509/8/0702q.jpg
phospholipid bilayer of membrane
What kinds of molecules pass through a cell membrane most easily?
small and hydrophobic
What is the function of Structure E? https://session.masteringbiology.com/problemAsset/1100509/8/0701q.jpg
stabilization of the phospholipids
