Cell Biology Exam Two - Transport Energetics

A =

presynaptic neuron

calcium rushes in

B =

postsynaptic neuron

either Na+ or Cl- channel fires or inhibits neuron

Who does simple diffusion?

Eukaryotes and Prokaryotes

Who does facilitated diffusion?

Eukaryotes and Prokaryotes

Who does active transport?

Eukaryotes and Prokaryotes

Who does endocytosis?

Eukaryotic ONLY

Who does exocytosis?

Eukaryotic ONLY

When referring to the energetics of transport. One of two things happen:

energy is released as transport occurs

energy is required to drive transport

Moving up the gradient?

endergonic (+)

active transport

Moving down the gradient?

exergonic (-)

facilitated and simple diffusion

What happens when [S]inside > [S]outside?

Endergonic, +DeltaG, active transport

What happens when [S]inside < [S]outside?

Exergonic, -DeltaG, facilitated or simple diffusion

charged solutes have both a

concentration gradient

electrical potential

Vm =

both concentration gradient and the membrane potential

charges solutes favor the _____ movement of cations

inward

Vm is typically _____ (charge)

negative

zFVm will be _____ for a cation

negative

as the membrane potential of the cell becomes more negative ions

are easier to move in

As the membrane potential of the cell becomes more negative what happens to the anions

they don’t move since the cell is already negative

Calculate ∆Ginward.

The Uptake of Chloride Ions

o   50 mM inside and 100 mM outside

o   Membrane potential is -60 mV

o   F is the Faraday constant 23,062 cal/mol.V

o   R = 1.987 cal/mol.K

o   T is 25 degrees Celsius (298K)

+974 cal/mol

Calculate ∆Ginward

Uptake of Lactose

o   Internal [lactose] 10 mM

o   External [lactose] 0.20 mM

o   25 Celsius and R = 1.987 cal/mol.K

∆Ginward = + RTln [S]inside / [S]outside

+2316 cal/mol

Calculate the ∆Goutward

The Export of Lactose

o   Internal [lactose] 10 mM

o   External [lactose] 0.20 mM

o   25 Celsius and R = 1.987 cal/mol.K

∆Goutward = + RTln [S]outside / [S]inside

-2316 cal/mol

True of False. Transport down the gradient is always exergonic when dealing with uncharged solutes.

True

By what method(s) does exergonic transport occur?

facilitated diffusion

simple diffusion

For a given cell, the concentration of sucrose is 10mM on the inside and 0.5mM on the outside, whereas the concentration of Na+ is 0.5mM on the inside and 10mM on the outside. The membrane potential is -150mV, and the temperature is 25°C. Constants: R = 1.987 cal/mol degree; F = 23,062 cal/mol volt. What is the ∆G for the inward transport of sucrose?

+1.774 kcal/mol; an endergonic reaction

For a given cell, the concentration of sucrose is 10 mM on the inside and 0.5 mM on the outside, whereas the concentration of Na⁺ is 0.5 mM on the inside and 10 mM on the outside. The membrane potential is -150 mV, and the temperature is 25°C.   Constants:  R = 1.987 cal/mol degree; F = 23,062 cal/mole volt. What is the ∆G for the inward transport of sodium ions?  

-5.233 kcal/mol; an exergonic reaction