Bio E109 Midterm 1 Study Guide Questions With Complete
Solutions
L1 - describe the general process of signal transduction. Correct
Answers S - perception of Stimulus
R - signal transmitted to cell via Receptor
T - signal is Transduced by protein transducers
E - changes in product/activity of the cell Effectors
R - Response via the effectors
L1 - Give examples of primary and secondary active transport.
Correct Answers Primary active transport ex: the sodium-
potassium pump uses ATP to pump Na+ and K+ AGAINST
their respective gradients
Secondary active transport ex: the sodium-glucose symporter
uses the high extracellular concentration gradient of SODIUM to
pump 1 glc out along with 1 sodium molecule. ATP is not
directly used but is needed to set up the high sodium
concentration to allow glc transport
L1 - how can a cell be hypotonic to the solution BUT be
ISOSMOTIC or HYPEROSMOTIC to the solution? Correct
Answers if the nonpenetrating solute conc of that soln is
LOWER than that of the cell, then those NP solutes are
TRAPPED outside the cell in the solution and water from the
cell FLOWS OUT as now the solute conc in the solution is
iso/hyper-osmotic compared to the cell
L1 - How do GPCRs operate? Correct Answers ligand binds to
a GPCR and that opens an ion channels or alters enzyme activity
,L1 - How do receptor channels operate? Correct Answers
binding of a ligand opens/closes a signal
L1 - how do receptor enzymes operate? Correct Answers ligand
binds to a receptor enzyme and that actives an intracellular
enzyme
L1 - how does an integrin receptor operate? Correct Answers
Ligand binds to it and it alters enzymes or the cytoskeleton of
the cell
L1 - how does colligative property affect osmotic pressure?
Correct Answers b/c osmotic pressure is a colligative property,
osmotic pressure isn't dependent on size/bulk of the molecules.
diffusion however IS affected by molecule size (so it's NOT a
colligative property)
L1 - How does lipid solubility (the composition of the lipid
layer) affect the rate of diffusion? Correct Answers increased
lipid solubility would increase the rate of diffusion as it's easier
for molecules to diffuse to the other side of the membrane
L1 - how does lipid solubility affect the membrane
permeability? Correct Answers increased lipid solubility would
make the membrane MORE permeable
L1 - how does lipid solubility affect the rate of diffusion?
Correct Answers increase lipid solubility, increase rate of
diffusion
,L1 - how does membrane surface area affect the rate of
diffusion? Correct Answers increase surface area would
increase the rate of diffusion (because more space for the
molecules to diffuse across the membrane)
L1 - how does molecule size affect membrane permeability?
Correct Answers increased molecule size decreases membrane
permeability
L1 - how does molecule size affect the rate of diffusion Correct
Answers increase molecule size, decrease rate of diffusion
(inverse)
L1 - how does the concentration gradient affect the rate of
diffusion? Correct Answers increase concentration gradient on
one side, increase rate of diffusion to the other side
L1 - How is homeostasis different from equilibrium? Correct
Answers Homeostasis does NOT mean that concentrations of
ALL molecules are the same intracellular AND extracellularly,
it just means things are balanced the way the body wants it.
Equilibrium does mean that concentrations are equal on both
sides.
If the body achieves EQUILIBRIUM for all concentrations, the
organism would be DEAD.
L1 - Name the factors that influence the rate of diffusion Correct
Answers surface area, concentration gradient, membrane
permeability (lipid solubility and molecule size)
, L1 - the GLUT transporter moves glc from outside to inside of
membrane for glycolysis. This facilitated diffusion continues
until equilibrium is reached. But why is equilibrium never
reached? Correct Answers Because when glc is moved inside
the cell, it is converted to glucose-6-phosphate, which is another
molecule and is no longer considered as glucose to contribute to
the concentration gradient
L1 - what are the 2 types of cotransporters? Correct Answers
symporters and antiporters
L1 - what are the 4 categories of membrane receptors? Correct
Answers receptor channels
G-protein-coupled receptors
catalytic receptors: receptor enzyme and integrin receptor
L1 - what are the 5 rules for osmolarity and tonicity? Correct
Answers 1. Assume that all intracellular solutes are
NONPENETRATING
2. Compare osmolarities before cell is exposed to the solution
(at EQ, cell and soln are always isosmotic)
3. Tonicity of a solution describes the CHANGE IN VOLUME
of a cell AT EQUILIBRIUM
4. Tonicity's determined by compoaring NP solute
concentrations IN THE CELL and the SOLUTION. Net water
movement is INTO the compartment with the higher
concentration of NP solute
5. Hyposmotic solutions are ALWAYS HYPOTONIC
Solutions
L1 - describe the general process of signal transduction. Correct
Answers S - perception of Stimulus
R - signal transmitted to cell via Receptor
T - signal is Transduced by protein transducers
E - changes in product/activity of the cell Effectors
R - Response via the effectors
L1 - Give examples of primary and secondary active transport.
Correct Answers Primary active transport ex: the sodium-
potassium pump uses ATP to pump Na+ and K+ AGAINST
their respective gradients
Secondary active transport ex: the sodium-glucose symporter
uses the high extracellular concentration gradient of SODIUM to
pump 1 glc out along with 1 sodium molecule. ATP is not
directly used but is needed to set up the high sodium
concentration to allow glc transport
L1 - how can a cell be hypotonic to the solution BUT be
ISOSMOTIC or HYPEROSMOTIC to the solution? Correct
Answers if the nonpenetrating solute conc of that soln is
LOWER than that of the cell, then those NP solutes are
TRAPPED outside the cell in the solution and water from the
cell FLOWS OUT as now the solute conc in the solution is
iso/hyper-osmotic compared to the cell
L1 - How do GPCRs operate? Correct Answers ligand binds to
a GPCR and that opens an ion channels or alters enzyme activity
,L1 - How do receptor channels operate? Correct Answers
binding of a ligand opens/closes a signal
L1 - how do receptor enzymes operate? Correct Answers ligand
binds to a receptor enzyme and that actives an intracellular
enzyme
L1 - how does an integrin receptor operate? Correct Answers
Ligand binds to it and it alters enzymes or the cytoskeleton of
the cell
L1 - how does colligative property affect osmotic pressure?
Correct Answers b/c osmotic pressure is a colligative property,
osmotic pressure isn't dependent on size/bulk of the molecules.
diffusion however IS affected by molecule size (so it's NOT a
colligative property)
L1 - How does lipid solubility (the composition of the lipid
layer) affect the rate of diffusion? Correct Answers increased
lipid solubility would increase the rate of diffusion as it's easier
for molecules to diffuse to the other side of the membrane
L1 - how does lipid solubility affect the membrane
permeability? Correct Answers increased lipid solubility would
make the membrane MORE permeable
L1 - how does lipid solubility affect the rate of diffusion?
Correct Answers increase lipid solubility, increase rate of
diffusion
,L1 - how does membrane surface area affect the rate of
diffusion? Correct Answers increase surface area would
increase the rate of diffusion (because more space for the
molecules to diffuse across the membrane)
L1 - how does molecule size affect membrane permeability?
Correct Answers increased molecule size decreases membrane
permeability
L1 - how does molecule size affect the rate of diffusion Correct
Answers increase molecule size, decrease rate of diffusion
(inverse)
L1 - how does the concentration gradient affect the rate of
diffusion? Correct Answers increase concentration gradient on
one side, increase rate of diffusion to the other side
L1 - How is homeostasis different from equilibrium? Correct
Answers Homeostasis does NOT mean that concentrations of
ALL molecules are the same intracellular AND extracellularly,
it just means things are balanced the way the body wants it.
Equilibrium does mean that concentrations are equal on both
sides.
If the body achieves EQUILIBRIUM for all concentrations, the
organism would be DEAD.
L1 - Name the factors that influence the rate of diffusion Correct
Answers surface area, concentration gradient, membrane
permeability (lipid solubility and molecule size)
, L1 - the GLUT transporter moves glc from outside to inside of
membrane for glycolysis. This facilitated diffusion continues
until equilibrium is reached. But why is equilibrium never
reached? Correct Answers Because when glc is moved inside
the cell, it is converted to glucose-6-phosphate, which is another
molecule and is no longer considered as glucose to contribute to
the concentration gradient
L1 - what are the 2 types of cotransporters? Correct Answers
symporters and antiporters
L1 - what are the 4 categories of membrane receptors? Correct
Answers receptor channels
G-protein-coupled receptors
catalytic receptors: receptor enzyme and integrin receptor
L1 - what are the 5 rules for osmolarity and tonicity? Correct
Answers 1. Assume that all intracellular solutes are
NONPENETRATING
2. Compare osmolarities before cell is exposed to the solution
(at EQ, cell and soln are always isosmotic)
3. Tonicity of a solution describes the CHANGE IN VOLUME
of a cell AT EQUILIBRIUM
4. Tonicity's determined by compoaring NP solute
concentrations IN THE CELL and the SOLUTION. Net water
movement is INTO the compartment with the higher
concentration of NP solute
5. Hyposmotic solutions are ALWAYS HYPOTONIC
