MCAT biology test

1Principal classes of membrane proteins include all of the following except

				receptors
				cell surface markers
				spectrins
				transport proteins
2		Which of the following are not components of the cell membrane?
				cell surface markers
				transmembrane proteins
				interior protein network
				plasmodesmata
3		To cross the cell membrane, water must
			A)	squeeze between phospholipid molecules
			B)	pass through aquaporins
			C)	be transported at the expense of ATP
			D)	be moved by a cotransport system
4		If a cell's contents are greatly hypoosmotic to the surrounding environment, the cell will probably
			A)	expand
			B)	become isotonic
			C)	burst
			D)	shrivel
5		The sodium-potassium pump passes
			A)	more Na+ out than K+ in
			B)	K+ out and Na+ in on a one-for-one basis
			C)	Na+ out and K+ in on a one-for-one basis
			D)	K+ and Na+ in the same direction
6		Exocytosis is a process by which cells
			A)	pass substances out of the cell in vesicles
			B)	pass substances out of the cell through the membrane by osmosis
			C)	release substances directly into the extracellular fluid through a pore
			D)	release substances directly into the extracellular fluid through a pit
			E)	identify substances in the environment
7		A phospholipid has
			A)	a phosphate group in place of one fatty acid
			B)	phosphate groups in place of two fatty acids
			C)	phosphate groups in place of three fatty acids
			D)	a phosphate group in place of a carbon in glycerol
			E)	none of the above
8		Clathrin-coated pits are used to
			A)	extrude bulk fluids from the cell
			B)	allow desired molecules directly into the cytoplasm
			C)	pass wastes in vesicles to the outside.
			D)	pass information into adjacent cells
			E)	bring desired substances from the environment into the cell in vesicles
9		A lipid bilayer
			A)	permits water soluble molecules to pass through it
			B)	facilitates the passage of water soluble molecules through it
			C)	inhibits the passage of water soluble substances through it
			D)	actively transports water soluble molecules through it
			E)	is indifferent to the passage of water molecules through it
10		A cell is recognized by other tissue members as "self" by its surface
			A)	glycolipids
			B)	phosphate groups
			C)	glycoproteins
			D)	ketoglutaric acids
			E)	glycocarbohydrates
11		A net gain of water tends to occur
			A)	in a hypoosmotic solution from an isosmotic solution
			B)	in an isosmotic solution from a hyperosmotic solution
			C)	in a hyperosmotic solution from a hypoosmotic solution
			D)	in a hypoosmotic solution from a hyperosmotic solution
			E)	in one isosmotic solution from another isosmotic solution of the same composition
12		Red blood cells have a characteristic concave shape because of
			A)	spectrin
			B)	dextrin
			C)	hemoglobin
			D)	hemocyanin
			E)	iron
13		By a mechanism called cotransport
			A)	sugar moves down its concentration gradient while sodium moves up its concentration gradient
			B)	sodium moves outward against is concentration gradient while sugar moves inward down its concentration gradient
			C)	sugar and sodium move inward down their concentration gradient
			D)	sodium moves inward down its concentration gradient while sugar moves inward up its concentration gradient
			E)	sodium and sugar move outward against their concentration gradient
14		Many surface proteins are anchored by
			A)	polar amino acids
			B)	hydrogen bonding amino acids
			C)	nonpolar fatty acids
			D)	nonpolar amino acids
			E)	polar fatty acids
15		Transmembrane proteins are
			A)	always fixed in position
			B)	always abundant
			C)	often not fixed in position
			D)	never abundant
			E)	none of the above
16		Cystic fibrosis results from defective ion channels for
			A)	Na+
			B)	Cl-
			C)	Ca++
			D)	ClO3-
			E)	H+
17		Fluidity of phospholipid bilayer is increased by
			A)	double bonds between carbon atoms in the fatty acid tails
			B)	steroid lipids at certain temperatures
			C)	poor alignment of the fatty acids tails
			D)	cholesterol at certain temperatures
			E)	all of the above
18		A cell engaged in phagocytosis must be
			A)	engulfing a live organism
			B)	acquiring a liquid
			C)	engulfing a dead organism
			D)	transporting bulk dissolved nutrients
			E)	transporting bulk solid material
19		A, B, and O blood groups are marked by surface
			A)	glycoproteins
			B)	glycolipids
			C)	glycocarbohydrates
			D)	glycerol
			E)	gluterates
20		In each cycle the sodium-potassium pumps transfer
			A)	two potassium ions in and two sodium ions out
			B)	one sodium ion out and one potassium ion in
			C)	three sodium ions out and two potassium ions in
			D)	one potassium ion out and two sodium ions in
			E)	three sodium ions in and two potassium ions out
21		____________________ are transported by a particular carrier or pass through a particular channel.
			A)	All water soluble ions or molecules
			B)	Certain water soluble molecules or ions
			C)	All insoluble molecules or ions
			D)	Certain insoluble ions or molecules
			E)	Only the smallest molecules or ions
22		Equilibrium is reached in an aqueous solution when
			A)	random motion stops
			B)	water molecules and dissolved molecules are moving at the same rate
			C)	the dissolved molecules or ions are equally distributed throughout the solution
			D)	molecular motion stops
			E)	there are the same number of water molecules as dissolved molecules
23		Substances transported by facilitated diffusion
			A)	move passively through specific channels from an area of greater concentration to one of lower concentration
			B)	are limited to solvents
			C)	must have movements coupled to those of other substances
			D)	may flow to a region of higher concentration by the expenditure of energy
			E)	are restricted to only one direction through the membrane
24		In a lipid bilayer the lipids have
			A)	their water repelling heads facing inward
			B)	their water repelling tails facing inward
			C)	their hydrogen bond forming heads facing inward
			D)	their hydrogen bond forming tails facing inward
			E)	no relationship to water
25		A lipid bilayer is held together by
			A)	surface tension
			B)	double bonds in their fatty acid tails
			C)	the attraction of the phospholipid heads to each other
			D)	hydrogen bonding with water
			E)	the electrostatic attraction of phosphate groups for each other
26		The glycocalyx is a "sugar coating" on the surface of a cell resulting from the presence of polysaccharides on glycolipids and glycoproteins embedded in the outer layer of the plasma membrane.
			A)	True
			B)	False
27		Threonine, an amino acid, and arabinose, a monosaccharide, cross the cell membrane down their concentration gradients by:
			A)	diffusion.
			B)	endocytosis.
			C)	phosphorylation.
			D)	facilitated diffusion.
			E)	osmosis.
28		A contractile vacuole is an organelle that pumps excess water out of many freshwater protozoan cells. A freshwater protozoan was placed in solution A and observed to form contractile vacuoles at a rate of 11 per minute. The same protozoan was then placed in solution B and observed to form contractile vacuoles at a rate of 4 per minute. Based on this information, which of the following statements is correct?
			A)	Solution A is hyperosmotic to solution B.
			B)	Solutions A and B are isosmotic.
			C)	Solution B is hyperosmotic to solution A.
			D)	Solutions A and B are isosmotic to the protozoan cell.
			E)	Both a and b.
29		The net movement of uncharged, polar molecules across a semipermeable membrane from a low concentration to a high concentration occurs by facilitated diffusion.
			A)	True
			B)	False
30		The membrane transport mechanism used when an amoeba engulfs a bacterial cell is called:
			A)	exocytosis
			B)	pinocytosis
			C)	facilitated diffusion
			D)	active transport
			E)	phagocytosis
31		Continuing from the previous question, once the bacterial cell has been digested, the amoeba will dispose of indigestible materials by which of the following processes?
			A)	facilitated diffusion
			B)	through gated channels in membrane proteins
			C)	exocytosis
			D)	active transport
			E)	by any of the above processes
32		ATP is required in the transport of
			A)	water molecules
			B)	all molecules across a membrane
			C)	molecules to areas of lower concentrations
			D)	molecules to areas of higher concentrations
			E)	molecules through a protein channel
33		The sodium-potassium pump establishes concentration gradients
			A)	of higher sodium concentrations inside the cell and higher potassium concentrations outside the cell
			B)	of sodium and potassium but the area of their concentrations (inside or outside) depends on the needs of the cell
			C)	of higher potassium concentrations inside the cell and higher sodium concentrations outside the cell
			D)	of ATP inside the cell where it is needed
			E)	by pumping sodium outside the cell and potassium is cotransported out as well
34		In cotransport processes, sugars can be brought into the cell against their concentrations gradients
			A)	because ATP powers the pump that brings them in
			B)	because they follow sodium ions into the cell which are traveling down their concentration gradients
			C)	because they follow potassium in through the sodium-potassium pump
			D)	through endocytosis
			E)	sugar enters the cell by all of the processes listed above
35		The methods of membrane transport that don't require protein channels or carriers are
			A)	osmosis
			B)	diffusion
			C)	phagocytosis
			D)	exocytosis
			E)	all of the above  Chapter 6 (p. 122) 1. A phospholipid is similar to a triglycerol, but has a phosphorylated alcohol in the place of the fatty acid on the third carbon of the glycerol molecule. Increasing the number of double bonds between carbons in phospholipid fatty acid chains would increase the fluidity of the membrane. 2. Proteins typically span cell membranes as multi-pass helices, which form protein channels, or as beta-barrels, creating pores in the membrane. 3. A cell hyperosmotic to its environment would have a higher concentration of solutes in its cytoplasm than the surrounding environment. 4. Both are forms of endocytosis, or taking extracellular materials into the cell. Phagocytosis employs the extension of pseudopods to take in comparatively large particulate material (such as a pathogen by a white blood cell); pinocytosis occurs when the cell invaginates to take in a volume of fluid containing desired microparticulate or molecular material. 5. In receptor-mediated endocytosis, a coated pit in the membrane contains a protein receptor. When triggered by the presence of a specific molecule, the pit closes over and traps the molecule within a vesicle. 6. Facilitated diffusion differs from simple diffusion in that specific carrier molecules are employed for movement across a membrane, and a saturation limit can be reached when no further diffusion can occur because all carrier molecules are in use. 7. Active transport is different from facilitated diffusion in that it is an energy-requiring (ATP-using) process capable of moving molecules against their concentration gradients, but similar in that it involves the use of carrier proteins.