Download Bio102 Problems

Bio102 Problems
Transport Across Membranes
1. Antiport is one type of
A. facilitated transport.
B. active transport.
C. endocytosis.
D. channel protein.
E. carrier protein.
2. Pinocytosis is one type of
A. exocytosis.
B. phagocytosis.
C. facilitated transport.
D. endocytosis.
E. diffusion.
3A. Consider a bacterial cell that is hypertonic in comparison to its environment. Will water move into
the cell or out of the cell?
in
3B. We now add a large amount of either O2, N2, or Pyruvate to the fluid surrounding the cell. Which
one will have the biggest effect on the movement of water? Will its addition increase or
decrease the movement of water? Please explain your answer.
Pyruvate will have the biggest effect, decreasing the movement of water because the cell is less
hypertonic (and may even be hypotonic). Oxygen and nitrogen both move through the
membrane and thus don’t affect osmosis.
4.
Imagine a bacterial cell living in a test tube under the following conditions:
inside the cell
outside the cell
K+
Mg2+
Na+
50 mM
10 mM
0.1 mM
3 mM
10 mM
150 mM
4A. Is the G value for Mg2+ movement into the cell positive, negative or zero?
negative
4B. Under these conditions, is the solution hypotonic, hypertonic or isotonic relative to the cell?
hypertonic
4C. Under these conditions, will the net movement of water be into the cell or out of the cell?
Why?
out of
4D. If we added a large concentration (say, 1M) of CO2 to the outside of the cell, it would have
no effect on the net movement of water. Why not?
CO2 can cross the membrane
4E. If the fatty acid tails in the phospholipids that make up this cell’s membranes were more
saturated, would that increase or decrease the rate at which water moves? Or would it have
no effect? Please explain.
decrease. More saturations mean that it is less fluid and thus less permeable to
everything, including water
5. Which one molecule might move across a membrane by simple diffusion?
A. CO2
B. Glutamate (an amino acid)
C. Insulin (a peptide hormone)
D. K+
E. Maltose (a simple carbohydrate)
6. Which one statement does not accurately describe simple active transport?
A. It requires a protein.
B. Simple active transport is a type of endocytosis.
C. Any type of substrate may be moved by simple active transport.
D. ATP provides the energy for the movement.
E. Simple active transport may be used to move a molecule against its concentration gradient.
7. A human liver cell is living in a a dish under the following conditions:
Na+
SO42-
Cl-
K+
outside the cell
100 mM
0.1 mM
15 mM
15 mM
inside the cell
10 mM
100 mM
15 mM
150 mM
-
+
0
+
Gin value:
7A. For each ion, indicate in the table whether the G value for the movement of that ion into the
cell is positive (+), negative (-) or zero (0).
7B. These cells use an antiporter protein to drive the uptake of SO42- into the cell. What other ion
might be co-transported along with SO42-? Briefly describe how you arrived at your answer.
Sodium would work. The movement of the second ion needs to release energy (G<0) to
power the uptake of the sulfate.
7C. Under these conditions, is the cell hypotonic, hypertonic or isotonic relative to the solution?
Hypertonic
7D. Under these conditions, will the net movement of water be into the cell or out of the cell?
into
7E. If we added more cholesterol to this membrane, how would that affect the G values you
described above? How would it affect whether the cell is hypertonic or hypotonic? How would it
affect the rate at which the water moves? Or would it affect any of these? Please briefly explain
your answer.
It would have no effect on the G values above or the hyper/hypotonicity of the cell. Rather, it
would affect the rate at which water (or anything else) moves by simple diffusion.
8. For each statement about membrane transport listed below, circle the type(s) of transport being
described. Circle all that apply.
Can be used to transport amino acids.
Simple
Diffusion
Facilitated
Transport
Simple Active
Transport
Coupled Active
Transport
A sodium-magnesium symporter is an
example of this type of transport.
This type of transport always requires a
protein.
The transported molecule always follows
its concentration gradient.
Simple
Diffusion
Facilitated
Transport
Simple Active
Transport
Coupled Active
Transport
Simple
Diffusion
Facilitated
Transport
Simple Active
Transport
Coupled Active
Transport
Simple
Diffusion
Facilitated
Transport
Simple Active
Transport
Coupled Active
Transport
Uses energy in ATP to move a molecule.
Simple
Diffusion
Facilitated
Transport
Simple Active
Transport
Coupled Active
Transport
Osmosis is one example of this type of
transport.
CO2 waste is removed from the cell by
this type of transport
Simple
Diffusion
Facilitated
Transport
Simple Active
Transport
Coupled Active
Transport
Simple
Diffusion
Facilitated
Transport
Simple Active
Transport
Coupled Active
Transport
9. Match each statement to the type of transport being described. Notice that some statements may
describe more than one type of transport; in those cases, list all that apply.
Manganese ions could be moved by this type (or types)
_FA____ of transport.
The waste product of aerobic cell respiration is typically
__P___ removed from the cell by this one type of transport.
Some cells contain many copies of a Na+/Mn2+
__A____ antiporter. What type (or types) of transport is this?
Increasing the number of unsaturations in the
phospholipid tails would increase the rate of which one
__P____ type of transport?
A channel protein may be used for this type (or types) of
__FA___ transport.
P Passive Transport
F Facilitated Diffusion
A Active Transport
N None of the above
10. It’s not surprising that meat spoils quickly if left at room temperature for just a few days, due to the
growth of a large number of bacteria. However, if that meat is first treated with large amounts of
salt (making beef jerky), it can be left at room temperature indefinitely without spoiling. Why?
The high concentrations of salt draws nearly all of the water out of the meat cells by
osmosis. With so little water left in the meat, it is impossible for it to spoil.
11. Which process is an example of endocytosis?
A. Mitochondrial fission
B. Antiport
C. Oxidative phosphorylation
D. Osmosis
E. Pinocytosis
12. Imagine that we collect some white blood cells from a human donor and resuspend them in
Phosphate-Buffered Saline (PBS). Under these conditions, the cells can live and be fully
functional for several days. PBS consists of 10 mM sodium phosphate buffer at pH 7.4, 140 mM
NaCl and 1M glucose and is isotonic to the cells.
12A. If we forgot to add any NaCl when preparing the PBS, what would happen to the white
blood cells? Why?
The PBS is no longer isotonic but is now hypotonic. Water will rush into the cells, leading to their
lysis.
12B. If we accidentally added 280mM NaCl while preparing the PBS, what would happen to the
white blood cells? Why?
The PBS is no longer isotonic but is now hypertonic. Water will leave the cells, leading to their
shrivelling.
12C. After they have lived in the test tube for several hours, we are able to detect increasing
concentrations of lactic acid in solutions surrounding these cells. What can you conclude
about the metabolic state of these cells? Do you also expect these cells to be producing
CO2? Please briefly explain your answers.
They are principally undergoing anaerobic metabolism. Very little CO2 will be produced, since
the Kreb’s cycle is not extensively being used.
12D. What type of transport could be used by these cells to excrete the lactic acid? Please briefly
explain your answer.
Since this is a three-carbon acid, it can’t leave by simple diffusion. It must be leaving by
facilitated or active transport.
13. For each statement about membrane transport listed below, circle the type (or types) of transport
being described. Circle all that apply.
Molecular oxygen enters a cell by this
type(s) of transport.
Antiport
Endocytosis
Exocytosis
Facilitated Transport
Osmosis
Simple Active Transport
Simple Diffusion
Symport
Cotransport includes this type(s) of
transport.
Antiport
Endocytosis
Exocytosis
Facilitated Transport
Osmosis
Simple Active Transport
Simple Diffusion
Symport
Antiport
Endocytosis
Exocytosis
Facilitated Transport
Osmosis
Simple Active Transport
Simple Diffusion
Symport
Antiport
Endocytosis
Exocytosis
Facilitated Transport
Osmosis
Simple Active Transport
Simple Diffusion
Symport
Antiport
Endocytosis
Exocytosis
Facilitated Transport
Osmosis
Simple Active Transport
Simple Diffusion
Symport
Proteins made on the Rough ER are
secreted by this mechanism(s).
A carrier protein can be used for this
type(s) of transport.
ATP is cut in this type(s) of transport.