Bio exam Ch 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? -1.0 M -Distilled water -150 mM. -0.8 M -0.4 M

1.0 M This solution is hypertonic to the plant cell. Water will leave the cell, and eventually the plasma membrane will pull away from the cell wall, resulting in plasmolysis.

The concentration of solutes in a red blood cell is about 2%, but red blood cells contain almost no sucrose or urea. Sucrose cannot pass through the membrane, but water and urea can. Osmosis would cause red blood cells to shrink the most when immersed in which of the following solutions? -Pure water -A hypertonic sucrose solution -A hypertonic urea solution -A hypotonic urea solution -A hypotonic sucrose solution

A hypertonic sucrose solution when a cell is placed in a hypertonic environment, water will leave the cell, causing it to shrink.

Which statement about the sidedness of the plasma membrane is correct? -Every integral membrane protein has a specific orientation in the plasma membrane. -The two lipid layers may differ in specific lipid composition. -Parts of proteins that are exposed on the cytoplasmic side of the endoplasmic reticulum are also exposed on the cytoplasmic side of the plasma membrane. -The asymmetrical distribution of membrane proteins, lipids, and carbohydrates across the plasma membrane is determined as the membrane is being constructed. -All of the listed responses are correct.

All of the listed responses are correct.

Cells A and B are the same size, shape, and temperature, but cell A is metabolically less active than cell B, and cell B is actively converting oxygen to water in cellular respiration. Oxygen will diffuse more rapidly into cell _________ because ______________...

B because the diffusion gradient in cell B is steeper As long as a metabolically active cell converts oxygen to water during cellular respiration shortly after it enters, diffusion into the cell will continue because the concentration gradient favors movement in that direction.

Seawater is hypertonic to cytoplasm in vertebrate cells and in plant cells. If red blood cell and a plant cell were placed in seawater, what would happen to the 2 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.

Which of the following molecules is most likely to passively diffuse across the plasma membrane? -DNA -CO2 -Glucose -Sodium ion -Hemoglobin

CO2 Hydrophobic molecules, such as hydrocarbons, carbon dioxide, and oxygen, can dissolve in the membrane and cross it with ease.

Which of the following statements concerning carbohydrates associated with the plasma membrane is correct? -Carbohydrates on the plasma membrane are typically long, complex chains of several dozen monosaccharides. -Carbohydrates are found associated with the membranes of prokaryotic cells only. -Membrane carbohydrates function primarily in cell-cell recognition. -The carbohydrate composition of most eukaryotic plasma membranes is quite similar. -Carbohydrates associated with the plasma membrane are located on both surfaces of the membrane.

Membrane carbohydrates function primarily in cell-cell recognition variations in carbohydrate structure distinguish one species from another, one individual from another, and even one cell type from another.

A selectively permeable membrane separates 2 solutions. Water is able to pass through this membrane; however, sucrose (a disaccharide) and glucose (a monosaccharide) cannot pass. The membrane separates a 0.2-molar sucrose solution from a 0.2-molar glucose solution. With time, how will the solution change?

Nothing will happen because the 2 solutions are isotonic. Osmotic pressure is produced by the concentration of dissolved substances and is not influenced by the relative sizes of the solutes.

Which of the following statements about the role of phospholipids in the structure and function of biological membranes is correct? -phospholipids form a single sheet in water -phospholipids are completely unable to interact with water -they are triacylglycerols, which are commonly available in foods. -phospholipids form a selectively permeable structure

Phospholipids form a selectively permeable structure. Their structure allows some substances to penetrate easily and blocks others.

Which of the following pairs correctly matches a membrane transport process to its primary function? -Exocytosis: the movement of water and solutes out of the cell by passage through the plasma membrane -Pinocytosis: the uptake of water and small solutes into the cell by formation of vesicles at the plasma membrane -Osmosis: passive diffusion of water and small solutes across a membrane -Phagocytosis: secretion of large particles from the cell by fusion of vesicles with the plasma membrane -None of the listed responses is correct.

Pinocytosis: the uptake of water and small solutes into the cell by formation of vesicles at the plasma membrane pinocytosis is the uptake of liquid and the solutes dissolved in the liquid.

Consider the transport of protons and sucrose into a plant cell by the sucrose-proton cotransport protein. Plant cells continuously produce a proton gradient by using the energy of ATP hydrolysis to pump protons out of the cell. Why, in the absence of sucrose, do protons not move back into the cell through the sucrose-proton cotransport protein? -Protons cannot move through membrane transport proteins. -Protons are freely permeable through the phospholipid bilayer, so no transport protein is needed for protons. -Protons, unlike other substances, do not diffuse down their electrochemical gradient. -In the absence of sucrose, the ATP-powered proton pump does not function, so there is no proton gradient. -The movement of protons through the cotransport protein cannot occur unless sucrose moves at the same time.

The movement of protons through the cotransport protein cannot occur unless sucrose moves at the same time. the obligate coupling of proton movement to sucrose movement prevents the energy of the proton gradient from being lost if sucrose is not present.

A single plant cell is placed in an isotonic solution. Salt is then added to the solution. Which of the following would occur as a result of the salt addition? -The added salt makes the solution hypotonic compared to the cell. Water will enter the cell by osmosis. -The added salt would enter the cell, causing the cell to take up water and swell. -There would be no osmotic movement of water in response to the added salt. -Water would enter the cell by osmosis, and the cell would swell. -Water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease.

Water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease. the added salt makes the solution hypertonic compared to the cell. Water will leave the cell by osmosis.

Green olives may be preserved in brine, which is a 30% salt solution. How does this method of preservation prevent microorganisms from growing in the olives?

a 30% salt solution is hypertonic to the bacteria, so they lose too much water and undergo plasmolysis. if a cell is placed in a hypertonic solution, it will lose water to its environment, shrivel, and probably die.

If you hydrogenated the fatty acid chains in the phospholipid bilayer, this will result in:

a higher melting temperature, higher viscosity, decreased fluidity

Which of the following would be least likely to diffuse through a plasma membrane without the help of a transport protein? -A large, nonpolar molecule -A small, nonpolar molecule -Dissolved gases such as oxygen or carbon dioxide -A large, polar molecule -Any of the listed molecules would easily diffuse through the membrane.

a large, polar molecule the combination of being polar and large means that this molecule will be the slowest one from the choices to move across the membrane.

What is glycoprotein?

a protein attached to sugar

Which of the following is a correct difference between active transport and facilitated diffusion? -Facilitated diffusion involves transport proteins, and active transport does not. -Active transport requires an input of energy, and facilitated diffusion does not. -Facilitated diffusion can move solutes against a concentration gradient, and active transport cannot. -Facilitated diffusion requires carrier proteins, but active transport requires channel proteins. -Active transport involves transport proteins, and facilitated diffusion does not.

active transport requires an input of energy, and facilitated diffusion does not. active transport can move substances against the concentration gradient, but it requires energy in the form of ATP.

to increase the fluidity of a membrane:

add some phospholipids containing unsaturated fatty acids

Which is the most difficult to get across a lipid bilayer by itself? a. testosterone b. a chloride ion c. a fatty acid d. all of the choices are equally difficult to get across a lipid bilayer e. glucose

b. a chloride ion

Which of the following statements about cotransport of solutes across a membrane is correct? -Cotransport involves the hydrolysis of ATP by the transporting protein. -The sodium-potassium pump is an example of a cotransport protein. -In cotransport, both solutes that are being transported are moving down their chemical gradients. -Cotransport proteins allow a single ATP-powered pump to drive the active transport of many different solutes. -A cotransport protein is most commonly an ion channel.

cotransport proteins allow a single ATP-powered pump to drive the active transport of many different solutes the electrochemical gradient created by a single ATP-dependent pump can drive the transport of many different solutes using cotransport proteins.

Which of the following is a specific characteristic of active transport? a. transport of charged molecules b. use of a carrier protein c. use of a channel protein d. use of ATP e. transport from the outside to the inside of a cell

d. the use of ATP

Which of the following correctly describes a general property of all electrogenic pumps? -Electrogenic pumps can pump a large variety of solutes across a membrane against their concentration gradient. -Electrogenic pumps result in a cell with an interior that is positively charged relative to the outside the cell. -Electrogenic pumps result in a cell with a high internal concentration of protons. -Electrogenic pumps create a voltage difference across the membrane. -Electrogenic pumps pump sodium out of the cell and potassium into the cell.

electrogenic pumps create a voltage difference across the membrane an electrogenic pump creates a net charge difference across a membrane (a membrane potential)

A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mothers milk. these molecules probably enter the cells lining the baby's digestive tract via which process?

endocytosis endocytosis is the procedure that cells use to import large molecules across their plasma membrane

Which of the following is NOT a function of membrane proteins? -cell-cell recognition -transport -enzymatic activity -energy, carbon, and nitrogen storage -intercellular joining

energy, carbon, and nitrogen storage proteins are not present in biological membranes to act as stores of energy, carbon, and nitrogen.

Which of the following processes and organelles account for the replacement of lipids and proteins lost from the plasma membrane? -Endocytosis and Golgi -Exocytosis and smooth ER and rough ER -Active transport and the rough ER -Flip-flop of phospholipids from one side of the plasma membrane to the other and the Golgi -Receptor-mediated endocytosis and smooth ER and Golgi

exocytosis and smooth ER and rough ER in exocytosis, vesicles derived from then endomembrane system fuse with the plasma membrane, thus increasing the # of phospholipids in the plasma membrane and increasing its surface area. The smooth ER is largely responsible for production of lipids destines for the membrane, and the rough ER produces proteins destined for the plasma membrane.

A cell has a membrane potential of -100mV (more negative inside than outside) and has 1,000 times more calcium ions outside the cell than inside. Which of the following best describes a mechanism by which Ca^(2+) enters the cell? -Movement of Ca2+ into the cell through a carrier protein down its electrical gradient -Cotransport of Ca2+ into the cell with Cl- -Facilitated diffusion of Ca2+ into the cell down its electrochemical gradient -Passive diffusion of Ca2+ into the cell down its electrochemical gradient -Movement of Ca2+ into the cell through an ion channel down its concentration gradient

facilitated diffusion of Ca^(2+) into the cell down its electrochemical gradient both the electrical and chemical (concentration) gradients contribute the energy to move Ca(2+) into the cells by facilitated diffusion as long as there is a channel or carrier that is specific for Ca^(2+)

Which of these statements describes some aspect of facilitated diffusion? -Facilitated diffusion is another name for osmosis. -Facilitated diffusion of solutes occurs through phospholipid pores in the membrane. -Facilitated diffusion of solutes may occur through channel or transport proteins in the membrane. -There is only one kind of protein pore for facilitated diffusion. -Facilitated diffusion requires energy to drive a concentration gradient.

facilitated diffusion of solutes may occur through channel or transport proteins in the membrane. The passageways for facilitated diffusion may be either protein pores or carrier proteins.

Which of the following is FALSE in regard to facilitated diffusion? -Facilitated diffusion can occur by means of transport proteins. -Facilitated diffusion can occur through protein channels. -Facilitated diffusion requires the hydrolysis of ATP. -Facilitated diffusion requires a concentration gradient. -Facilitated diffusion can move ions across membranes.

facilitated diffusion requires the hydrolysis of ATP. this statement is false. Facilitated diffusion, like simple diffusion, needs only a concentration gradient- no energy input is required.

Phagocytosis: Pinocytosis: Receptor Mediated Endocytosis -- correspond in the same order to: -water: food: cell surface proteins -food: water: cell surface proteins -food: cell surface proteins: water -water: cell surface proteins: food -none of these are in the right order

food: water: cell surface proteins

Lipid bilayers:

form spontaneously

osmosis means water moves toward:

higher solute concentration

you put a liver cell in a solution in a beaker. the cell swells up and bursts. this is because the solution was:

hypertonic

Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the plasma membrane would cholesterol most likely be found?

in the interior of the membrane the steroid cholesterol, wedged between phospholipid molecules in the plasma membranes of animals, helps stabilize the membrane.

A protein that goes all the way from one side of the membrane to the other is a:

integral protein

Which of the following statements about diffusion is true? -It occurs when molecules move from a region of lower concentration to a region of higher concentration. -It always requires integral proteins of the cell membrane. -It involves only the movement of water molecules. -It requires expenditure of energy by the cell. -It is a passive process.

it is a passive process diffusion is the tendency of molecules to spread out in the available space. A substance will diffuse from an area of higher concentration to an area of lower concentration without energy input.

When cell A recognizes cell B in the body, what is cell A actually recognizing?

it is recognizing carbohydrates on the membrane proteins on the surface of cell B

Which of the following functions of membrane proteins is important in tissue formation during embryonic development in animals? -Membrane proteins form channels, which move substances across the membrane. -Membrane proteins possess enzymatic activity. -Membrane proteins with short sugar chains form identification tags that are recognized by other cells. -Membrane proteins attach the membrane to the cytoskeleton. -All of the listed responses are correct.

membrane proteins with short sugar chains form identification tags that are recognized by other cells. Cell-cell recognition is an important function of membrane proteins, and this cell-cell recognition is important in tissue formation during embryogenesis.

Consider the currently accepted fluid mosaic model of the plasma membrane where in the membrane would carbohydrates most likely be found?

on the outside (external) surface of the membrane membrane carbohydrates are covalently bonded to lipids or proteins and extend out from the external side of the plasma membrane as a means of cell identification

Diffusion through an ion channel and down a concentration gradient is known as:

passive transport

Which of the following statements about passive transport is correct? -Passive transport operates independently of diffusion. -In passive transport, solute movement stops when the solute concentration is the same on both sides of the membrane. -Passive transport permits the solute to move in either direction, but the net movement of solute molecules occurs down the concentration gradient of the molecule. -Passive transport does not occur in the human body. -Passive transport operates independently of the concentrations of the moving solute.

passive transport permits the solute to move in either direction, but the net movement of solute molecules occurs down the concentration gradient of the molecule.

Which of the following does NOT change membrane fluidity? -temperature -unsaturation -cholesterol -saturation -phospholipid charge

phospholipid charge

cell membranes are made of:

phospholipids

The Singer-Nicholson Fluid Mosaic model of a membrane is incorrect because:

proteins are anchored inside and outside the cell

What kind of membrane protein do you need to make a membrane gradient?

pump protein

Which of the following enables a cell to pick up and concentrate a specific kind of molecule? -Facilitated diffusion -Passive transport -Receptor-mediated endocytosis -Osmosis -Channel proteins

receptor-mediated endocytosis in receptor-mediated endocytosis, only a specific molecule, called a ligand, can bind to the receptor. Without receptor binding occurring 1st, endocytosis does not proceed.

Which of the following should go through a membrane on its own, without help from a protein? -sodium ions -protons (H+) -ATP -free amino acids -steroids

steroids

the plasma membrane is referred to as a "fluid mosaic" structure. Which of the following statements about that model is true? -only phospholipids are capable of moving in the membrane -the fluid aspect of the membrane is due to the behavior of phospholipids, and the mosaic aspect is due to the presence of carbohydrates. -the fluid aspect of the membrane describes its structure at normal temperatures, and the mosaic aspect describes the behavior of the membrane as the temperature is lowered. -the mosaic aspect of the membrane is due to the glycosylation of phospholipids on the cytoplasmic side of the membrane. -the fluid aspect of the membrane is due to the mobility of phospholipids, and embedded proteins account for the mosaic aspect.

the fluid aspect of the membrane is due to the mobility of phospholipids, and embedded proteins account for the mosaic aspect.

Which moves more ions across the membrane faster? -the sodium channel -the sodium-potassium pump -the sucrose carrier -aquaporins -all of the above work equally fast

the sodium channel

Active transport requires an input of energy and can also generate voltages across membranes. Based on this information, which of the following statements is true? -Active transport moves solutes down their concentration gradients and always uses ATP as the source of energy to do this. -The source of energy for active transport of a solute up its gradient can be ATP or a concentration gradient of a second solute. This second gradient of solutes maintains no net difference in voltage across the membrane. -Active transport uses channel proteins and ensures that the interior of the cell is always positive compared to the exterior of the cell. -The sodium-potassium pump hydrolyzes ATP and results in a net positive change outside the cell membrane. -Active transport can use ATP as its energy source and ensures that there is no voltage across the cell membrane.

the sodium-potassium pump hydrolyzes ATP and results in a net positive charge outside the cell membrane. this is how the sodium-potassium pump generates voltage across the cell membrane

Glucose can be moved into cells via an active transport mechanism when the concentration of glucose inside the cell is higher than the concentration of glucose outside the cell. this active transport mechanism moves glucose and sodium into the cell at the same time. the glucose moves up its gradient and the sodium moves down its gradient. Which of the following statements about this mechanism is accurate? -To pump glucose up its concentration gradient, sodium moves down its concentration gradient, and the distribution of sodium ions across the membrane forms an electrochemical gradient that drives this mechanism. -Sodium and glucose move together into the cell via facilitated diffusion. -Sodium and glucose move together into the cell via facilitated diffusion, and to pump glucose up its concentration gradient, sodium moves down its concentration gradient. -The distribution of sodium ions across the membrane forms an electrochemical gradient that drives this mechanism. -To pump glucose up its concentration gradient, sodium moves down its concentration gradient.

to pump glucose up its concentration gradient, sodium moves down its concentration gradient, and the distribution of sodium ions across the membrane forms an electrochemical gradient that drives this mechanism. the movement of sodium down its gradient drives glucose up its gradient, and because sodium is at different concentrations on either side of the membrane and as sodium has a +1 charge, an electrochemical gradient also exists.