Cellular bio Flashcards
Which of the following is NOT a colligative property?
A. Freezing-point depression
B. Boiling-point elevation
C. Diffusion
D. Vapor pressure
C. Diffusion
Secreted and membrane-bound proteins must go through the secretory pathway, targeted there by a signal sequence. The signal sequence must be composed of:
A. hydrophilic amino acids.
B. hydrophobic amino acids.
C. basic amino acids.
D. acidic amino acids.
B. hydrophobic amino acids.
What type of cellular junction allows for exchange of cytosol between cells?
Gap junctions
At what juncture point is mitosis most heavily regulated?
Between G1 and S phases
What is the correct order in the steps of apoptosis?
Disassemble cytoskeleton,
break down nuclear membrane,
break down genome,
phagocytic digestion
All of the following are characteristics of G-protein mediated cell signaling EXCEPT:
A. they are the mechanism by which steroid hormones exert their effects.
B. they can result in increased intracellular calcium.
C. they are an example of signal amplification.
D. they are fast and temporary.
A. they are the mechanism by which steroid hormones exert their effects.
In Kartagener’s syndrome, defective dynein is produced causing a paralysis of microtubule-based movement of flagellae and cilia. One could expect to find all of the following outcomes EXCEPT:
A. failure to ovulate in women.
B. male infertility.
C. chronic lung infections.
D. ectopic pregnancy in women.
A. failure to ovulate in women.
- A male with Kartagener’s syndrome would be infertile due to immobile sperm, eliminating male infertility.
- Ova would not enter the Fallopian tubes normally, due to the lack of cilia, causing increased risk of ectopic pregnancy, eliminating ectopic pregnancy in women.
- The lungs also require cilia to remove bacteria and other particulates, eliminating chronic lung infections.
- Ovulation, however, is determined by levels of circulating hormones and will not be affected by the lack of dynein.
What organelle would be most closely associated with exocytosis of newly synthesized secretory protein?
A. Lysosomes
B. Golgi apparatus
C. Ribosomes
D. Peroxisomes
B. Golgi apparatus
Which types of protein are produced by the ribosomes of the rough endoplasmic reticulum?
I. Membrane-bound
II. Integral
III. Secreted
A. I and II only
B. II and III only
C. I, II, and III
D. I and III only
C. I, II, and III
Lysosomal proteins are integral proteins
Compound X binds specifically and irreversibly to the potassium-binding site of sodium-potassium ATPase pumps, inhibiting the activity of this protein. Which of the following would most likely result from poisoning cells with compound X?
A. ATP would still be produced and ion pumping would continue.
B. ATP production would cease.
C. ATP hydrolysis would increase.
D. Secondary active transport would be impaired.
D. Secondary active transport would be impaired.
The Na+/K+ ATPase uses the energy from ATP hydrolysis to pump Na+ out of the cell and K+ into the cell, creating concentration gradients for these two ions. The Na+ pumped out can then be used in secondary active transport, where the energy of the Na+ concentration gradient is used to move other molecules into or out of the cell.
If Compound X were to inhibit the activity of this pump, the Na+ concentration gradient would not be formed, and secondary active transport would not be possible. ATPases hydrolyze ATP, they do not synthesize it, and if the pump is inhibited, ATP hydrolysis would be inhibited.
Large proteins, most notably albumin, are dissolved in the plasma and serve an important role in regulation of plasma volume. Reducing the amount of albumin to below-normal levels would most likely have which of the following effects?
A. Movement of water from the tissues into the bloodstream with resulting dehydration, due to increased osmotic pressure.
B. Movement of water from the tissues into the bloodstream with resulting dehydration, due to reduced hydrostatic pressure.
C. Movement of water from the bloodstream into the tissues with resulting swelling, due to increased hydrostatic pressure.
D. Movement of water from the bloodstream into the tissues with resulting swelling, due to reduced osmotic pressure.
D. Movement of water from the bloodstream into the tissues with resulting swelling, due to reduced osmotic pressure
The reduced osmotic pressure of the blood will have the effect of allowing water to leave the bloodstream and enter the tissues, where it will cause the tissues to swell.
(You can also think of it as the tissues’ relative osmotic pressure increasing, thus they have a greater tendency to draw water out of the blood.)
Fluorescence recovery after photobleaching (FRAP) involves the bleaching (a non-reversible process) of a fluorescent compound and observation of the bleached spot for new fluorescent signal. If a circular spot is bleached in a cell membrane uniformly containing high levels of a fluorescent transmembrane protein, what best describes the change in fluorescence over time?
A. Recovery of fluorescence beginning at the periphery of the spot due to lateral diffusion of proteins in the membrane.
B. Recovery of fluorescence beginning at the center of the spot due to the action of flipases.
C. Recovery of fluorescence beginning at the center of the spot due to relaxation of excited electrons.
D. Recovery of fluorescence beginning at the periphery due to diffusion into the membrane of newly translated proteins in the cytoplasm.
A. Recovery of fluorescence beginning at the periphery of the spot due to lateral diffusion of proteins in the membrane.
Photobleaching involves the permanent quenching of fluorescence. Given this is an integral membrane protein, it is capable of lateral diffusion within the cell membrane and non-bleached protein will begin to encroach on the bleached spot shortly after bleaching.
Vertebrates have developed various renal structures for osmoregulation based on their habitats. Bony fish that live in seawater drink large amounts of seawater and use cells in gills to pump excess salt out of the body. This is in response to:
A. a need to maintain their tissues in a hypoosmotic state.
B. an influx of water by osmosis into their tissues.
C. a loss of water by active transport to their hypertonic surroundings.
D. a loss of salt to their surroundings.
A. a need to maintain their tissues in a hypoosmotic state.
Bony fish living in saltwater maintain hypoosmotic body fluids. The hyperosmotic water they live in tends to draw the water out of their body by osmosis. They can obtain water by ingesting ocean water, but this raises their internal osmolarity. They excrete salt, then, to lower their internal osmolarity.
Which of the following is an example of passive transport?
A. Movement of protons into the mitochondrial matrix in oxidative phosphorylation, with the proton influx driving ATP synthesis.
B. Transport of protons out of the mitochondrial matrix by the electron transport chain.
C. Movement of a bolus of food through the digestive tract.
D. Absorption of glucose from the digestive tract.
A. Movement of protons into the mitochondrial matrix in oxidative phosphorylation, with the proton influx driving ATP synthesis.
In oxidative phosphorylation, protons move down their gradient from the intermembrane space of the mitochondria into the mitochondrial matrix. Any time a substance moves across a membrane, down its gradient, the process is a form of passive transport.
Do not let the fact that the proton movement is driving ATP formation confuse you; even though the protons are moving through the ATP synthase, they are still moving down their gradient so the process is passive.
A physiologist observes a dark, dense subcellular structure via electron microscopy that spans the space between two adjacent cell membranes and extends to the underlying cytoskeleton. Upon further investigation, she discovers that two cells with this structure are electrically isolated but that a tracer dye can travel between the cells through the pericellular space. What is the identity of this structure?
A. Communicating junction
B. Tight junction
C. Gap junction
D. Desmosome
D. Desmosome
Desmosomes are a type of anchoring junction which connect adjacent cells and extend through the cell membrane to associate with components of the cytoskeleton.
How do deosomes differ from gap junctions and tight junctions?
Unlike gap junctions (also known as communicating junctions), desmosomes do not link the cytoplasms of the two cells (the cells are not electrically coupled). Tight junctions form connections with adjacent cells but prevent pericellular diffusion of molecules, such as any kind of dye, where as a deosome would allow a dye through.
If erythrocytes (RBCs) are placed into a hypertonic solution, they will:
A. hemolyze.
B. shrivel.
C. remain the same.
D. swell up.
B. shrivel.
Hypertonic = shriveling
hypotonic = swelling
In a hypertonic solution, the extracellular environment has a higher solute concentration. Osmotic pressure would draw water out of the cell, making solutes more concentrated inside the cell, and making the cell shrivel.
As the molality of a solution increases, how are its boiling point and vapor pressure affected?
A. Both boiling point and vapor pressure decrease.
B. Boiling point decreases and vapor pressure increases.
C. Both boiling point and vapor pressure increase.
D. Boiling point increases and vapor pressure decreases.
D. Boiling point increases and vapor pressure decreases.
Boiling point increases with an increasing concentration of solutes because more energy is required to separate the water from those solutes.
Vapor pressure decreases with an increasing concentration of solutes; since it takes more energy to trigger evaporation, there will be less solvent evaporating, and thus less pressure due to those evaporated solvent molecules.
A hypertonic solution creates a gradient that will draw fluid through a semi-permeable membrane. Which of the following is a true statement?
A. Osmotic pressure is the force used to allow more solutes to be dissolved in the hypertonic solution.
B. Osmotic pressure is the force exerted to push enough fluid into the solution to make it hypotonic.
C. Osmotic pressure is the force used to push solutes through the semi-permeable membrane to balance the concentrations.
D. Osmotic pressure is the force necessary to counterbalance the pull on fluid exerted by the hypertonic solution.
D. Osmotic pressure is the force necessary to counterbalance the pull on fluid exerted by the hypertonic solution.
A hypertonic solution creates a gradient that will draw fluid through a semi-permeable membrane. Osmotic pressure is the pressure used to counteract osmosis or the force needed to keep the solutes in the hypertonic solution from drawing on the available fluid is a true statement.
It does not move or alter solutes and will not change the tonicity of the solution.
How does freezing-point depression work to defy the thermodynamic principle of entropy?
A. During freezing, solvent first forms crystals before solutes are organized into an array; thus higher solute concentrations require lower temperatures to freeze.
B. During freezing, solvent first forms crystals before solutes are organized into an array; thus lower solute concentrations require lower temperatures to freeze.
C. During freezing, solutes are first organized into an array before the solvent forms crystals; thus higher solute concentrations require lower temperatures to freeze.
D. During freezing, solutes are first organized into an array before the solvent forms crystals; thus lower solute concentrations require lower temperatures to freeze.
C. During freezing, solutes are first organized into an array before the solvent forms crystals; thus higher solute concentrations require lower temperatures to freeze.
In the process of freezing, solutes are arrayed before the solvent freezes. The more solute present in the solution, the more energy must be removed from that system to organize those solutes into the requisite array. Thus, even more energy needs to be removed to then freeze the solvent.
Clathrin, a substance that aggregates on the cytoplasmic side of cell membranes, is responsible for the coordinated pinching off of membrane in receptor-mediated endocytosis. A lipid-soluble toxin that inactivates clathrin would be associated with:
A. increased protein production on the rough endoplasmic reticulum.
B. increased secretion of hormone into the extracellular fluid.
C. an increase in ATP consumption.
D. reduced delivery of polypeptide hormones to endosomes.
D. reduced delivery of polypeptide hormones to endosomes.
Endocytosis is the process by which the cell internalizes receptor–ligand complexes from the cell surface, such as polypeptide hormones bound to their receptor. At the cell surface, the receptor–ligand complexes cluster in clathrin-coated pits and pinch off the vesicles that join acidic compartments known as endosomes.
How does the van’t Hoff factor of NaCl compare to that of NH3?
A. The i of NaCl is 2 while the i of NH3 is 4.
B. The i of both NaCl and NH3 is 1.
C. The i of NaCl is 2 while the i of NH3 is 1.
D. The i of both NaCl and NH3 is 2.
C. The i of NaCl is 2 while the i of NH3 is 1.
Since NaCl is ionic, it breaks into Na+ and Cl– giving an i = 2.
Since NH3 is non-ionic, it does not break down and thus has an i = 1.
When it is time to breed, salmon travel from saltwater, in which they are hypotonic, to freshwater, in which they are hypertonic. They maintain solute balance by reversing their osmoregulatory machinery when moving between the two environments. Failure to reverse this machinery when moving to their breeding grounds would most likely result in:
A. improved metabolic activity, as enzyme concentrations increased.
B. no change, because movement from a hypertonic to a hypotonic medium does not present osmotic challenges.
C. death, as cells became too concentrated to carry out normal metabolism.
D. death, as cells underwent lysis due to water influx.
D. death, as cells underwent lysis due to water influx.
In a hypotonic environment (freshwater), the cells will have higher osmotic pressure than the surrounding environment. Water would tend to flow into the cells, causing them to swell and eventually burst.
The Na+/K+ ATPase, found in the membranes of all cells, establishes concentration gradients of Na+ and K+ across the cell membrane. Furthermore, K+ can cross the cell membrane though K+ leak channels; the overall effect of the two membrane proteins is to maintain osmotic balance for the cell and to establish an electrical potential across the cell membrane. The movement of K+ through the leak channels is best characterized as:
A. simple diffusion.
B. facilitated diffusion.
C. primary active transport.
D. secondary active transport.
B. facilitated diffusion.
if the molecule moves through a channel or a carrier protein, it is specifically called facilitated diffusion.
