BIOL 2021 Lecture Notes - Lecture 9: Electrochemical Gradient, Passive Transport, Conformational Change

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lavendershark790

19 Jan 2018

School

York University

Department

Biology

Course

BIOL 2021

Professor

Patricia Lakin- Thomas

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Document Summary

Active transport: directional transport that is coupled to another energy source: ion gradient or atp can be used as an energy source, work must be put in to push something against its gradient, less entropy. They are very specific for certain molecules (like enzymes) They can be inhibited by small molecule inhibitors competitive or uncompetitive ones (like enzymes) 3 states of conformational change: outward open, occluded, inward open. Transporters can flip between the states randomly and does not depend on solute binding. A: the solute is more likely to bind to the transporter on the side of the membrane with higher concentration, and less likely to bind on the low concentration side. So there is a net movement of solute from high to low concentration. At equilibrium, there is still movement back and forth but the concentrations are equal to the net movement is 0.

Related Questions

1. What biochemical feature of a phospholipid molecule allows phospholipids to spontaneously form closed compartments when placed in an aqueous solution?

a) they are amphipathic

b) they are charged

c) they are spherical

d) they have a single fatty acid tail

2. Other than phospholipids, what molecule do cells use to alter the fluidity of biological membranes?

3. What distinguishes active transport from passive transport?

a) active transport can utilize channel proteins

b) passive transport does not utilize carrier/transporter proteins

c) active transport requires the input of energy

d) active transport only occurs at the plasma membrane

4. In the case of active transport, the Na+/K+ pump undergoes a sequence of conformational changes that allows the movement of Na+ and K+ across a membrane against their electrochemical gradients, while in the case of ER protein import SRP undergoes a sequence of conformational changes to allow the signal sequence to interact with the translocation pore. What drives these conformational changes?

a) hydrolysis of a high energy phosphate bond

b) binding of a solute or protein

c) both

d) neither

5. Is protein import into the ER co-transcriptional, or co-translational?

burgundyhyena124

1. The plasma membrane of liver cells contains a glucose uniportthat transports glucose by facilitated diffusion. When the[glucose] is higher inside the liver cell than the [glucose]outside the liver cell, the glucose uniport will

A. couple the transport of glucose out of the cell to thehydrolysis of ATP

B. couple the transport of glucose into the cell to thehydrolysis of ATP

C. switch to a closed conformation, allowing no transport ofglucose

D. transport glucose out of the cell by passive transport

E. transport glucose in of the cell by passive transport

2. Unlike the positive charged ion shown in the middle diagramof figure 11-4B, K+ is higher in concentration inside the cell. Howwill the membrane potential of a cell at rest (shown in both themiddle and right-hand diagrams of Figure 11-4B) affect theelectrochemical gradient for K+?

A. The membrane potential will increase the electrochemicalgradient

B. The membrane potential will decrease the electrochemicalgradient

C. The membrane potential will have no effect on theelectrochemical gradient

3. Which of the following proteins carries out activetransport?

A. gluclose symport

B. Bacteriorhodopsin

C. ABC transporter

D. NA K pump

E. All of the above

4. Aquaporin will not transport Na+ ions because

A. Two asparagine residues in the channel prevent the passage ofNa+ ions by binding the oxygen of each water molecule as it passesby

B. Na+ ions are repelled by the positive charges at the entranceto the channel

C. Na+ ions cannot make contact with the carbonyl (C=O) groupson all four sides of the channel

D. The passage of Na+ ions is energetically unfavorable becauseone side of the channel is hydrophobic in nature

5. The acetylcholine receptor is different from other channelproteins we have discussed, such as the K+ leak channel,because

A. The acetylcholine channel is composed of a single polypeptiderather than multiple subunits

B. The acetylcholine channel transports Na+ ions against theconcentration gradient for sodium

C. The acetylcholine channel has a much smaller diameter thanother channel proteins

D. The acetylcholine channel transports ions with theirassociated shell of water molecules

E. The acetylcholine channel is always open, and never switchesto a closed conformation

6. After opening briefly along the axon of a neuron,voltage-gated ion channels switch to an inactivated conformationthat slowly returns to the original closed conformation of theprotein. This slow change in conformation, requiring about amillisecond, is important because

A. all of the ions that were transported across the membranewhen the ion channels were open must be actively transported backto the other side of the membrane, restoring the originalconcentration gradient, before the ion channels can open again

B. ATP hydrolysis is necessary to drive this energeticallyunfavorable change in conformation

C. it prevents the action potential from reversing direction andtraveling back toward the cell body of the neuron

D. the channel protein must be dephosphorylated in order tocomplete the transport process and return to the originalnonphosphorylated conformation

limeelephant476

Question 1

Plasma membranes are selectively permeable. This means that

	A.	glucose cannot enter the cell.
	B.	the plasma membrane allows some substances to enter or leave a cell more easily than others.
	C.	plasma membranes must be very thick.

Question 2

Oxygen molecules O₂ crosse a plasma membrane by

	A.	passive transport
	B.	osmosis
	C.	active transport

Question 3

Facilitated diffusion across a biological membrane requires ________ and moves a substance ________ its concentration gradient.

		A. energy and channel proteins; against (up)
		B. transport proteins that make channels ; down
		C. energy ; down

Question 4

When two aqueous solutions that differ in solute concentration are placed on either side of a semipermeable membrane and osmosis is allowed to take place, the water will

		A. move to the side with lower water concentration
	B.	move to the side with higher water concentration
	C.	move to the side with lower solute concentration

Question 5

Kinetic energy differs from chemical energy in that

	A.	chemical energy is a particular form of kinetic energy.
	B.	kinetic energy is the energy of a moving object, whereas chemical energy is the potential energy of molecules.
	C.	kinetic energy is stored energy that has the potential to do work, and chemical energy is the energy of movement.

Question 6

When a cell uses chemical energy to perform work, it uses the energy released from a(n) ________ reaction to drive a(n) ________ reaction.

	A.	exergonic; endergonic
	B.	endergonic; exergonic
	C.	spontaneous; exergonic

Question 7

When an enzyme catalyzes a reaction

		A. it raises the activation energy of the reaction.
		B. it lowers the activation energy of the reaction.
		C. it is used once and discarded.

Question 8

Which of the following statements regarding enzyme function is false?

		A. An enzyme's function depends on its three-dimensional shape.
		B. Enzymes are very specific for their substrates.
		C. Enzymes are used up when they catalyze a chemical reaction so must be synthesized for each new chemical reaction

BIOL 2021 Lecture Notes - Lecture 9: Electrochemical Gradient, Passive Transport, Conformational Change

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