ESSENTIAL CELL BIOLOGY - EXAM #2
QUESTIONS WITH COMPLETE
SOLUTIONS
What is passive transport? - ANSWER-Flowing down the concentration gradient
What is active transport? - ANSWER-Acting against a concentration gradient, requiring
energy
How do transport proteins discriminate? - ANSWER-Transporters are very specific due
to the binding site, whereas channels discriminate on size and charge and can open
and close based on stimuli (passive transport only)
Where does energy for transporters come from? - ANSWER-ATP or another molecule
moving down its concentration gradient (coupled)
Facilitated diffusion - ANSWER-Diffusing across a membrane through the use of a
transport protein
How do membrane transporters affect diffusion? - ANSWER-They increase the rate of
diffusion
How are transport proteins similar to enzymes? - ANSWER-Active transporters reach a
"max rate" and have binding sites
How is the direction of transport for uncharged molecules determined? - ANSWER-
Dependent solely on concentration gradient
What two forces affect charged molecules?
What is this net force called? - ANSWER-a. Concentration gradient and membrane
potential
b. Electrochemical gradient
How is a cell charged (membrane potential)? - ANSWER-Positive charge outside and
negative charge inside along the membrane
What charge molecules does the membrane potential favor? - ANSWER-Diffusion of
positively charged molecules
Membrane potential (E or E_M) - ANSWER-Voltage across a membrane that exerts a
force on charged molecules
,How is the ΔG equation altered for the addition of an electrochemical gradient? -
ANSWER-DeltaG = RT ln [solute]_inside / [solute]_outside + FE_M
What are the three basic mechanisms of active transport? - ANSWER-- Coupled
transporter
- ATP-driven pump
- Light-driven pump
Coupled transporter - ANSWER-Uses a different molecule's concentration gradient to
power the pump for a different molecule against its gradient
Symport - ANSWER-Molecule in a coupled transporter going against its gradient moves
in the same direction as the co-transported ion
Antiport - ANSWER-A membrane transport process that carries one substance in one
direction and another in the opposite direction.
Molecule in a coupled transporter going against its gradient moves in the opposite
direction of the co-transported ion
Uniport - ANSWER-Facilitated diffusion without a co-transported ion
ATP-driven pump - ANSWER-Uses the energy from ATP to power the pump
How much ATP does a cell use for its sodium-potassium pumps? - ANSWER-30% of all
ATP (only used in animal cells)
What is an example of the important functions that sodium potassium pumps serve? -
ANSWER-The sodium gradient created from the pump can move back down its
concentration gradient into a sodium-glucose symporter, coupling to get glucose into the
cell
Where is a sodium-glucose symporter found? - ANSWER-In the stomach lining within
the microvilli
What is an example of a cell using passive and active transport on the same molecule?
- ANSWER-Glucose symporters to bring them in, and glucose transporters to move
them out down its gradient
Why are ion channels important? - ANSWER-They control many types of behavior and
movement in plants and animals
What is an example of an ion channel controlling movement? - ANSWER-Venus flytrap
, Are nerve cells polar or non polar? - ANSWER-Nerve cells are polar
What is the basic function of a neuron? - ANSWER-- The cell body receives signals
through dendrites
- Signal travels down the axon to the terminus
- Terminus transmits messages to outside sources using neurotransmitters
How big are axons? How many axons do you have? - ANSWER-• They're huge! Some
cross great lengths from your brain all the way down to your feet, but don't worry- you
have myelin sheath surrounding it for support and to make the action potential signal
conduct faster.
• You have one axon per neuron.
How big are axons? - ANSWER-Either very tiny (1 mm) up to huge (1 m) in length
What composes ion channels? - ANSWER-Integral membrane proteins with several
transmembrane alpha helices
All channels.... (3) - ANSWER-1. Are selective
2. Gated (activated)
3. Passive transport
What types of disorders come from ion channel malfunctions (name along with the type
of channel)? - ANSWER-- Migraines ( calcium channel)
- Myasthenia gravis (acetylcholine (sodium) receptors)
- Cystic fibrosis (Cl transporter (CFTR))
What does perturbed water balance in a cell cause? - ANSWER-Increases susceptibility
to bacterial infections
What are the four mechanisms to opening and closing channels? - ANSWER--
Volatage-gated
- Ligand-gated (extracellular)
- Ligand-gated (intracellular)
- Stress-gated
QUESTIONS WITH COMPLETE
SOLUTIONS
What is passive transport? - ANSWER-Flowing down the concentration gradient
What is active transport? - ANSWER-Acting against a concentration gradient, requiring
energy
How do transport proteins discriminate? - ANSWER-Transporters are very specific due
to the binding site, whereas channels discriminate on size and charge and can open
and close based on stimuli (passive transport only)
Where does energy for transporters come from? - ANSWER-ATP or another molecule
moving down its concentration gradient (coupled)
Facilitated diffusion - ANSWER-Diffusing across a membrane through the use of a
transport protein
How do membrane transporters affect diffusion? - ANSWER-They increase the rate of
diffusion
How are transport proteins similar to enzymes? - ANSWER-Active transporters reach a
"max rate" and have binding sites
How is the direction of transport for uncharged molecules determined? - ANSWER-
Dependent solely on concentration gradient
What two forces affect charged molecules?
What is this net force called? - ANSWER-a. Concentration gradient and membrane
potential
b. Electrochemical gradient
How is a cell charged (membrane potential)? - ANSWER-Positive charge outside and
negative charge inside along the membrane
What charge molecules does the membrane potential favor? - ANSWER-Diffusion of
positively charged molecules
Membrane potential (E or E_M) - ANSWER-Voltage across a membrane that exerts a
force on charged molecules
,How is the ΔG equation altered for the addition of an electrochemical gradient? -
ANSWER-DeltaG = RT ln [solute]_inside / [solute]_outside + FE_M
What are the three basic mechanisms of active transport? - ANSWER-- Coupled
transporter
- ATP-driven pump
- Light-driven pump
Coupled transporter - ANSWER-Uses a different molecule's concentration gradient to
power the pump for a different molecule against its gradient
Symport - ANSWER-Molecule in a coupled transporter going against its gradient moves
in the same direction as the co-transported ion
Antiport - ANSWER-A membrane transport process that carries one substance in one
direction and another in the opposite direction.
Molecule in a coupled transporter going against its gradient moves in the opposite
direction of the co-transported ion
Uniport - ANSWER-Facilitated diffusion without a co-transported ion
ATP-driven pump - ANSWER-Uses the energy from ATP to power the pump
How much ATP does a cell use for its sodium-potassium pumps? - ANSWER-30% of all
ATP (only used in animal cells)
What is an example of the important functions that sodium potassium pumps serve? -
ANSWER-The sodium gradient created from the pump can move back down its
concentration gradient into a sodium-glucose symporter, coupling to get glucose into the
cell
Where is a sodium-glucose symporter found? - ANSWER-In the stomach lining within
the microvilli
What is an example of a cell using passive and active transport on the same molecule?
- ANSWER-Glucose symporters to bring them in, and glucose transporters to move
them out down its gradient
Why are ion channels important? - ANSWER-They control many types of behavior and
movement in plants and animals
What is an example of an ion channel controlling movement? - ANSWER-Venus flytrap
, Are nerve cells polar or non polar? - ANSWER-Nerve cells are polar
What is the basic function of a neuron? - ANSWER-- The cell body receives signals
through dendrites
- Signal travels down the axon to the terminus
- Terminus transmits messages to outside sources using neurotransmitters
How big are axons? How many axons do you have? - ANSWER-• They're huge! Some
cross great lengths from your brain all the way down to your feet, but don't worry- you
have myelin sheath surrounding it for support and to make the action potential signal
conduct faster.
• You have one axon per neuron.
How big are axons? - ANSWER-Either very tiny (1 mm) up to huge (1 m) in length
What composes ion channels? - ANSWER-Integral membrane proteins with several
transmembrane alpha helices
All channels.... (3) - ANSWER-1. Are selective
2. Gated (activated)
3. Passive transport
What types of disorders come from ion channel malfunctions (name along with the type
of channel)? - ANSWER-- Migraines ( calcium channel)
- Myasthenia gravis (acetylcholine (sodium) receptors)
- Cystic fibrosis (Cl transporter (CFTR))
What does perturbed water balance in a cell cause? - ANSWER-Increases susceptibility
to bacterial infections
What are the four mechanisms to opening and closing channels? - ANSWER--
Volatage-gated
- Ligand-gated (extracellular)
- Ligand-gated (intracellular)
- Stress-gated
