Exam 1 Flashcards
The three components that comprise any given care are the:
Cytoplasm, cell membrane, and nucleus
Incorrect: cytosol, organelles, intracellular space, cell membrane, and extracellular space
The Extraceullar space contains:
Water, carbohydrates, and proteins
_________ can enter the cell through simple diffusion through the cell membrane.
A. Calcium
B. Glucose
C. Ethanol
D. ATP
E. DNA
C. Ethanol
Ethanol can undergo simple diffusion because it is a small, uncharged, polar molecule. Therefore ethanol is permeable through a cell membrane and thus can undergo simple diffusion.
Incorrect answers:
A. Calcium – calcium is an ion thus it is impermeable and would need a carrier mediated transporter.
B. Glucose – glucose is a large, uncharged polar molecule thus it is impermeable to the cell membrane and requires a carrier-mediated protein in order to enter the cell.
D. ATP – cannot undergo simple diffusion because ATP is a charged polar molecule that is impermeable to the cell membrane. Thus, ATP can only enter the cell through Carrier-mediated transport.
For Questions #4 & #5, consider a tank with two different aqueous solutions (of equal total volume) separated by a movable partition. Initial conditions: the left-hand compartment contains a 1.0 molal CaCl2 solution; the right-hand compartment contains a 0.5 molal CaCl2 solution.
- Initially:
A. the left-hand compartment exerts a greater osmotic pressure than the right-hand compartment.
B. the right-hand compartment exerts a greater osmotic pressure than the left-hand compartment.
C. the concentration of water is equal on both sides of the partition.
D. the osmolality of the right-hand compartment is twice that of the left-hand compartment.
E. the solutions on either side of the partition are isotonic. - If the partition were permeable only to water, then following osmosis (and once equilibrium is reached):
A. the partition will have shifted to the left.
B. there will be an equal concentration of CaCl2 in each compartment.
C. the osmotic pressure of the left-hand compartment will be greater than the osmotic pressure of the right-hand compartment.
D. both (A) and (B)
E. all of the above
- A. the left-hand compartment exerts a greater osmotic pressure than the right-hand compartment.
- A. there will be an equal concentration of CaCl2 in each compartment.
- KCl has a molecular weight of 75 g/mol. Suppose you wanted to create 500 milliliters of a 0.15 M KCl solution. How much KCl would you weigh out?
A. 1.0 grams
B. 5.6 grams
C. 22.5 grams
D. 250 grams
E. 1,000 grams
5.6 grams
- What is the osmolarity of the solution you created in Question #6?
A. 0.075 OsM
B. 0.15 OsM
C. 0.30 OsM
D. 0.45 OsM
E. 0.60 OsM
Hint the Molarity was 0.15 M KCl
The osmolarity of the solution is C. 30 Osm.
Found this by multiplying the molarity by the number of ions that form in solution.
(0.15 M * 2 ions) = 0.30 Osm
- All types of membrane transport proteins are similar in that:
A. they are active transporters.
B. they are passive transporters.
C. they hydrolyze ATP.
D. at least one solute particle is moved thermodynamically downhill.
E. they have a maximal rate at which they can move solute particles across the membrane.
A. they are NOT ALL active transporters.
B. they are NOT ALL passive transporters.
C. they hydrolyze ATP. (only for primary active transporters–only pumps do this)
D. at least one solute particle is moved thermodynamically downhill. (not true for pumps-they move everything uphill)
E. they have a maximal rate at which they can move solute particles across the membrane. (CORRECT ANSWER)
Membrane transport proteins that engage in secondary active transport:
A. require an input of free energy.
B move all solute particles downhill.
C. rely on the concentration gradients established by channels.
D. include uniporters.
E. include pumps.
Correct Answer: A. Membrane transport proteins that engage in secondary active transport require an input of free energy.
Active transport is the movement of solute in a energetically uphill direction. Requires work and energy.
With cotransport and antitransport at least one solute is being moved uphill.
C. Relys on the concentration gradients estabilished by PUMPS
There are two kinds of active transporters:
1. Primary active transporters – these include all pumps. They are able to move solute against its concentration gradient by the direct burning of ATP.
2. Secondary active transporters –this includes some carriers such as symporters and antiporters. Secondary active transport is a way to move a solute uphill without the direct ATP source. Instead there is an indirect way that these transporters get the energy needed to move something uphill and that is by moving a different solute downhill to release free energy.
Symporters are moving two solutes in the same direction, but one going uphill and one going downhill. The solute that goes downhill releases free energy that can then be harnessed to move the other solute against its concentration gradient.
C. rely on the concentration gradients established by channels. (NO, they never estabilish a concentration gradient) D. include uniporters. (No. Uniporters are passive transporters that move a solute downhill.) E. include pumps. (NO, pumps are primary active transporters)
Because the sodium pump moves one net ________ charge out of the cell with each catalytic cycle, the activity of the pump has a slight ________ effect on the plasma membrane.
Positive; hyperpolarizing
The sodium pump moves 3 Na+ ions out of the cell and 2 K+ ions into the cell. Thus, in each cycle we are losing 1 net positive charge resulting in a hyperpolarizing effect.
Driving Forces
The PUSH that a solute feels to move in a certain direction accross a cell membrane.
- Chemical driving force– if there is difference in concentration across that membrane for a particle. If there is a concentration gradient, there is a chemical driving force.
- Electrochemical driving force— only true for particles that carry a charge (ions) aka a net plus or minus charge
Electrochemical Gradient
Takes into account both the chemical gradient and the electrical driving force acting on that particle.
This is shown by NERST POTENTIAL.
The larger the difference between the nerst potential and the existing membrane potential corresponds to a larger electrochemical driving force.
