Chapter 7 Membrane Structure and Function

integral protein

Typically transmembrane proteins with hydrophobic regions that completely span the hydrophobic interior of the membrane.

exocytosis

process by which a cell releases large amounts of material

pinocytosis

process by which a cell takes in liquid from the surrounding environment

endocytosis

process by which a cell takes material into the cell by infolding of the cell membrane

ligand

A molecule that binds specifically to a receptor site of another molecule.

selective permeability

A property of biological membranes that allows them to regulate the passage of substances.

transport protein

A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane.

12. Mammalian blood contains the equivalent of 0.15 M NaCl. Seawater contains the equivalent of 0.45 M NaCl. What will happen if red blood cells are transferred to seawater? Hint: hypertonic- lower to higher A) Water will leave the cells, causing them to shrivel and collapse. B) NaCl will be exported from the red blood cells by facilitated diffusion. C) The blood cells will take up water, swell, and eventually burst. D) NaCl will passively diffuse into the red blood cells. E) The blood cells will expend ATP for active transport of NaCl into the cytoplasm.

A) Water will leave the cells, causing them to shrivel and collapse.

16. In most cells, there are electrochemical gradients of many ions across the plasma membrane even though there are usually only one or two electrogenic pumps present in the membrane. The gradients of the other ions are most likely accounted for by? Refer to 7.4 A) cotransport proteins. B) ion channels. C) carrier proteins. D) passive diffusion across the plasma membrane. E) cellular metabolic reactions that create or destroy ions.

A) cotransport proteins.

Which of the following factors will decrease membrane fluidity & movement? A) membranes rich in unsaturated fats B) warm temperatures and membranes rich in cholesterol C) cool temperatures and membranes rich in saturated fats D) cool temperatures and membranes rich in choloestoral

A) membranes rich in unsaturated fats

22) Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a 0.15 M salt solution become limp and soft. From this we can deduce that the cells of the celery stalks are A) the fresh water is hypotonic and the salt solution is hypertonic to the cells of the celery stalks. B) the fresh water and the salt solution are both hypotonic to the cells of the celery stalks. C) the fresh water is hypertonic and the salt solution is hypotonic to the cells of the celery stalks. D) the fresh water and the salt solution are both hypertonic to the cells of the celery stalks. E) the fresh water is isotonic and the salt solution is hypertonic to the cells of the celery stalks.

A) the fresh water is hypotonic and the salt solution is hypertonic to the cells of the celery stalks.

sodium potassium Pump

Active transporter that moves three Na+ out of a cell and two K+ into the cell against their respective concentration gradients.

proton pump

An active transport mechanism in cell membranes that uses ATP to force hydrogen ions out of a cell, generating a membrane potential in the process

electrogenic pump

An ion transport protein that generates voltage across a membrane

23) The sodium-potassium pump in animal cells requires cytoplasmic ATP to pump ions across the plasma membrane. When the proteins of the pump are first synthesised in the rough ER, what side of the ER membrane will the ATP binding site be on? A) It could be facing in either direction because proteins are properly reoriented in the Golgi apparatus. B) It will be on the cytoplasmic side of the ER. C) It doesn't matter, because the pump is not active in the ER. D) It will be on the side facing the interior of the ER.

B) It will be on the cytoplasmic side of the ER.

3. Which of the following factors would tend to increase membrane fluidity? Hint: remember saturated & unsaturated fats fluid/solidifys A) a greater proportion of unsaturated phospholipids B) a greater proportion of saturated phospholipids C) a lower temperature D) a relatively high protein content in the membrane

B) a greater proportion of saturated phospholipids

1. In what way do membranes of the Eukaryotic cell vary? A) Phospholipids are found only in certain membranes B) certain proteins are unique to each membrane C) only certain membranes of the cell are selectively permeable D) Only certain membranes are constructed of amphipathic molecules

B) certain proteins are unique to each membrane

19. White blood cells engulf bacteria through what process? A) exocytosis B) phagocytosis C) pinocytosis D) osmosis E) receptor-mediated exocytosis

B) phagocytosis

24) An organism with a cell wall would most likely be unable to take in materials through A) facilitated diffusion. B) phagocytosis. C) osmosis. D) diffusion. E) active transport.

B) phagocytosis.

10. What kinds of molecules pass through a cell membrane most easily? A) large and hydrophobic B) small and hydrophobic C) large polar D) ionic E) monosaccharides such as glucose

B) small and hydrophobic

11. Which of the following statements is correct about diffusion? Hint: spread out evenly into available space A) It is very rapid over long distances. B) It requires an expenditure of energy by the cell. C) It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration. D) It is an active process in which molecules move from a region of lower concentration to one of higher concentration. E) It requires integral proteins in the cell membrane.

C) It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.

14. Which of the following membrane activities require energy from ATP hydrolysis? A) facilitated diffusion of chloride ions across the membrane through a chloride channel B) movement of water into a cell C) Na⁺ ions moving out of a mammalian cell bathed in physiological saline D) movement of glucose molecules into a bacterial cell from a medium containing a higher concentration of glucose than inside the cell E) movement of carbon dioxide out of a paramecium

C) Na⁺ ions moving out of a mammalian cell bathed in physiological saline

5.. Which of the following is not a major function in the membrane? Hint: remember the 6 main functions A) Transport B) Cell-cell recognition C) Production of proteins D) Signal transduction

C) Production of proteins

18. Which of the following would increase the electrochemical potential across a membrane? A) a chloride channel B) a sucrose-proton cotransporter C) a proton pump D) a potassium channel E) both a proton pump and a potassium channel

C) a proton pump

8. In order for a protein to be an integral membrane protein it would have to be remember: it penetrates through membrane so it apart of both cytoplasmic & ECM side A) hydrophilic. B) hydrophobic. C) amphipathic, with at least one hydrophobic region. D) completely covered with phospholipids. E) exposed on only one surface of the membrane.

C) amphipathic, with at least one hydrophobic region.

17. The movement of potassium into an animal cell requires A) low cellular concentrations of sodium. B) high cellular concentrations of potassium. C) an energy source such as ATP. D) a cotransport protein. E) a potassium channel protein.

C) an energy source such as ATP.

2. According to the fluid mosaic model of cell membrane structure, proteins of the membrane are mostly Hint: membrane is a fluid structure with a 'mosaic' of various proteins embedded in it A) spread in a continuous layer over thinner and out surfaces of the membrane B) confined to the hydrophobic interior of the membrane C) embedded in the lipid bilayer D) randomly orientated in the membrane with no fixed outside polarity

C) embedded in the lipid bilayer

25) Biological evolution of life on Earth, from simple prokaryote-like cells to large, multicellular eukaryotic organisms, A) has occurred in accordance with the laws of thermodynamics, by expending Earth's energy resources and causing an increase in the entropy of the planet. B) has been made possible by expending Earth's energy resources. C) has occurred in accordance with the laws of thermodynamics. D) has caused an increase in the entropy of the planet. E) violates the laws of thermodynamics because Earth is a closed system.

C) has occurred in accordance with the laws of thermodynamics.

15. What is the voltage across a membrane called? A) water potential B) chemical gradient C) membrane potential D) osmotic potential E) electrochemical gradient

C) membrane potential

13. which of the following processes includes all the others? A) Osmosis B) diffusion of a solute across membrane C) passive transport D) transport of an ion down its gradient

C) passive transport

7. Which of the following types of molecules are the major structural components of the cell membrane? A) phospholipids and cellulose B) nucleic acids and proteins C) phospholipids and proteins D) proteins and cellulose E) glycoproteins and cholesterol

C) phospholipids and proteins

20. The difference between pinocytosis and receptor-mediated endocytosis is that? Refer to 7.5 A) pinocytosis brings only water molecules into the cell, but receptor-mediated endocytosis brings in other molecules as well. B) pinocytosis increases the surface area of the plasma membrane whereas receptor-mediated endocytosis decreases the plasma membrane surface area. C) pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity. D) pinocytosis requires cellular energy, but receptor-mediated endocytosis does not. E) pinocytosis can concentrate substances from the extracellular fluid, but receptor-mediated endocytosis cannot.

C) pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity.

9. The primary function of polysaccharides attached to the glycoproteins and glycolipids of animal cell membranes is A) to facilitate diffusion of molecules down their concentration gradients. B) to actively transport molecules against their concentration gradients. C) to maintain the integrity of a fluid mosaic membrane. D) to maintain membrane fluidity at low temperatures. E) to mediate cell-to-cell recognition.

E) to mediate cell-to-cell recognition.

glycolipid

membrane carbohydrates that are covalently bonded to lipids

tonicity

The ability of a solution to cause a cell within it to gain or lose water

membrane potential

The charge difference between a cell's cytoplasm and the extracellular fluid, due to the differential distribution of ions. Membrane potential affects the activity of excitable cells and the transmembrane movement of all charged substances.

osmoregulation

The control of water balance in organisms living in hypertonic, hypotonic, or terrestrial environments.

electrochemical gradient

The diffusion gradient of an ion, representing a type of potential energy that accounts for both the concentration difference of the ion across a membrane and its tendency to move relative to the membrane potential.

passive transport

The movement of materials through a cell membrane without using energy

concentration gradient

a difference in the concentration of a substance across a distance

glycoprotein

a protein with one or more carbohydrates covalently attached to it.

cotransport

a single ATP powered pump that transports one solute can indirectly drive the active transport of several other solutes in this mechanism as the solute that has been actively transported diffuses back passively through a transport protein its movement can be coupled with the active transport of another substance against its concentration gradient

ion channel

a transmembrane protein channel that allows a specific ion to flow across the membrane down its concentration gradient

gated channel

a transmembrane protein channel that opens or closes in response to a particular stimulus

aquaporin

a transport protein that facilitates the diffusion of water across the membrane

Receptor mediated endocytosis

allows the cell to acquire bulk quantities of specific substrates by receptors to which substrates attach which are then engulfed by the cell

plasmolysis

collapse of a walled cell's cytoplasm due to a lack of water

osmosis

diffusion of water through a selectively permeable membrane

active transport

energy-requiring process that moves material across a cell membrane against a concentration difference

hypotonic

having a lower concentration of solute than another solution

amphipathic

molecule that has both a hydrophilic region and a hydrophobic region such as a phosopholipid

facilitated diffusion

movement of specific molecules across cell membranes through protein channels

diffusion

process by which molecules tend to move from an area where they are more concentrated to an area where they are less concentrated

peripheral proteins

protein appendages loosely bound to the surface of the membrane and not embedded in the lipid bilayer.

hypertonic

solution that has a higher concentration of dissolved particles compared with another solution

fluid mosaic model

structural model of the plasma membrane where molecules are free to move sideways within a lipid bilayer

phagocytosis

the process by which a cell engulfs substances or other cells

isotonic

when the concentration of two solutions is the same (NEUTRAL)