LIFE I - exam 2
Which are present in any biological system? - Parts that are all linked in a linear fashion - Feedback regulation - Individual components that operate independently - A set of interdependent pieces
A set of interdependent pieces
Which statement about a signal transduction pathway is true? - A signal transduction pathway allows a single signal molecule to initiate a chain of events that amplify the signal at many steps inside the cell. - A signal transduction pathway is nonspecific, which allows the cell to use the same pathway for many different environmental signals. - A signal transduction pathway allows a cell to change its external environment to make it more suitable for its needs. - A signal transduction pathway provides a means for a signal molecule to pass through the cell membrane and initiate a chain of events inside the cell.
A signal transduction pathway allows a single signal molecule to initiate a chain of events that amplify the signal at many steps inside the cell.
Refer to the table showing three substances (A, B, C) transported across the cell membrane via passive transport. A: Facilitated diffusion through channel protein B: Simple diffusion C: Facilitated diffusion through carrier protein Identify the substances corresponding to their specific type of transport checked in the table.
A: K+ B: O2 C: galactose
A: moves outside to inside the cell B: moves inside to outside the cell Identify the processes shown in parts A and B of the figure.
A: endocytosis; B: exocytosis
Both primary and secondary active transport require energy in the form of ____________ to drive substances across a cell membrane.
ATP
Refer to the flowchart showing the steps involved in a G protein-linked signal transduction pathway. Signal molecule ⬇️ Receptor protein on cell surface ⬇️ Conformational change in receptor protein ⬇️ Self-phosphorylation of receptor protein ⬇️ G-protein activation and release of GDP ⬇️ Protein kinase cascade ⬇️ Cell response
All information is accurate
Refer to the table. A student created this table as a study guide referring to endocytosis. Phagocytosis: large particles; eat and destroy foreign particle; low specificity. Pinocytosis: fluid; increase fluid levels in cells; low specificity. Receptor mediated endocytosis: large particles; uptake of specific macromolecules from the environment; high specificity. Evaluate the accuracy of the information shown.
All information is accurate
Which scenario would best serve as an analogy to describe the difference between normal and mutated Ras protein?
An on-off light switch that has become permanently stuck in the "on" position
How do carrier proteins differ from channel proteins in their role as gatekeepers of the cell?
Carrier proteins bind to the substances they transport across the membrane via facilitated diffusion, whereas channel proteins provide a pore for substances to move across the membrane via facilitated diffusion.
What would you need in order to set up a simulation like this one to show what happens when you place a cell into a hypotonic sodium chloride solution?
Channel proteins and a membrane that is impermeable to sodium chloride
Which pair of actions is needed to establish the right balance of membrane fluidity in a marine animal that migrates from cold water to warm water?
Decrease unsaturated fatty acid content and increase fatty acid chain length.
How does changing the cholesterol content of a membrane affect its fluidity?
Decreasing the cholesterol content increases a membrane's fluidity.
Besides the proteins being processed for distribution, what other components could be expected to be found inside the Golgi apparatus?
Enzymes
What advantage is gained by having so many steps in one signal transduction pathway?
Greater amplification of the signal
The components of a metabolic pathway are followed over time. It is observed that the starting molecule of the pathway eventually becomes depleted and remains this way even though there is constant input of this molecule from another source. What is true about this pathway?
It could be regulated by a positive-feedback mechanism.
Which statement would be true of a membrane-bound protein that works in conjunction with a sodium-potassium pump during secondary active transport?
Its conformation will change when both an ion and a small molecule bind to it.
Which change would make a cell membrane more fluid?
Lower the cholesterol content in the cell membrane.
In the case of making the extracellular fluid hypertonic with respect to one of the molecules, which two features of the membrane were important to establish?
Membrane impermeability with respect to the molecule, and the presence of a uniporter directed outward from the cell
Suppose you have a metabolic pathway that involves the conversion of molecules A to B to C. Which condition would result in the greatest buildup over time of molecule A relative to molecules B and C?
Negative feedback and input of molecule A
Which type of transport enables you to establish isotonic conditions?
Passive transport
Another metabolic pathway involves the conversion of molecules X to Y to Z to Q. Enzyme 1 catalyzes the first reaction, enzyme 2 catalyzes the second, and enzyme 3 catalyzes the third. If enzyme 1 is activated by molecule Q and the gene for enzyme 1 is inhibited from being expressed, which set of simulation conditions will best model this system?
Positive feedback with no input
How could scientists use radioisotopes to study the function of the Golgi apparatus?
Radiolabeled sugars could be tracked as they are covalently attached to proteins within the Golgi apparatus.
Based on your experience with the simulation, how does changing the temperature affect the diffusion of molecules across a membrane?
Raising the temperature increases the rate of attainment of equilibrium concentrations of the diffusing molecule on either side of the membrane.
_______________ diffusion and _______________ diffusion are two types of passive transport.
Simple; facilitated
Some disease-causing microbes attack the body by turning on or off specific signal transduction pathways. In the disease cholera, the bacterium Vibrio cholerae causes massive diarrhea by interfering with such a pathway. A toxin from this bacterium enters intestinal cells and chemically modifies G proteins. Once modified, the G proteins can no longer cleave GTP into GDP. What would you expect to see within the intestinal cells of a person with cholera?
The G proteins remain activated and continually activate adenylyl cyclase.
A student discussing the role of the Golgi apparatus in cells makes the following three statements: - A variety of proteins enter the Golgi from vesicles that pinch off from the rough ER. - Within the Golgi apparatus, different proteins are modified by the activities of sugar molecules. - After modification, the proteins move within vesicles to specific locations in the cell.
The first and third statements are accurate; the second statement is not accurate.
A species of fish spends part of its life cycle under conditions of moderate temperatures and part of its life cycle under extremely cold conditions. What change in the cell membranes of this fish might be expected to occur as conditions shift from moderate to extremely cold temperatures?
The fish's cells would slow production of cholesterol and increase production of unsaturated, short chain fatty acids.
How do primary and secondary active transport mechanisms differ?
The goal of primary active transport is to move ions across the cell membrane against their concentration gradients; the goal of secondary active transport is to establish these same gradients to drive transport of another substance.
Refer to the table. A student created this table as a study guide. Primary active transport: ATP; ions only; 2 carrier proteins; Na+ K+ pump Secondary active transport: ATP and ion gradient; ions establish gradient and small molecules; 2 carrier proteins; glucose transport Evaluate the accuracy of the information shown.
The listed number of membrane proteins involved in primary active transport is not correct.
If you were to make a visual model of a receptor protein that is part of a signal transduction pathway, which key property should be included?
The model should show the receptor protein's cytoplasmic domain undergoing conformational change when the signal molecule binds to its extracellular domain.
What happens to matter incorporated into phagosomes?
The phagosome fuses with a lysosome, which contains enzymes that break down consumed material for use by the cell.
Which statement is true of coated pits?
They are regions of the cell membrane that are incorporated into vesicles as the cell takes up specific molecules from the environment.
Refer to the table. X: conc inside 0.10; cell conc outside cell 2.80. Y: conc inside cell 0.80; conc outside cell 0.05. Z: conc inside cell 1.90; conc outside cell 0.40. Which substance(s) are most likely to be moved across the membrane by passive transport if the typical external concentrations are those shown?
X only
__________________ is known as a second messenger in the signal transduction pathway involved in the "flight or fight" response.
cAMP
A key property of signal transduction pathways is that one signal molecule binding to a receptor protein in the cell membrane
can result in several thousand events at the end of the pathway.
The correct order of movement of proteins through the Golgi apparatus is
cis, medial, trans.
