BI110 Lecture Notes - Lecture 7: Osmosis, Cytosol, Hydrophile

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turquoisewasp140

4 Nov 2020

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Passive transport of molecules across a membrane through aid of a transporter. Becomes saturated at high concentrations of transported substance. Depends on membrane proteins and is specific for certain substances: channel proteins. Form hydrophilic channels in the membrane through which water and ions can move. Most proteins that carry out facilitated diffusions of ions are controlled by gates that open or close their transport channels: aquaporin. Water molecules move through the channel by being handed off to a succession of hydrogen-bonding sites on the channel. Outside cell cytosol: k+ voltage-gated channel. With normal voltage, the activation gate is closed, and k+ cannot move across the membrane. In response to a voltage change, the activation gate opens, and. Cytoplasm outside cell: carrier proteins. Bind a specific single solute and transport it across the lipid bilayer (uniport transport) Undergo conformational changes that move the solute-binding site from one side of the membrane to the other.

Related Questions

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

1. Which of the following pairings are/is correct?

Cholesterol: has a hydrophilic and hydrophobic end
Cholesterol: does not have a hydrophilic end since it is a lipid
Cholesterol: is often times wedged in between the phospholipids
1st and 2nd choices only
1st and 3rd choices only
2nd and 3rd choices only
All of the above
None of the above

2. Which of the following pairing/s is/are correct?

Cholesterol: helps maintain the integrity of the cell membrane
Cholesterol: the rigid four carbon rings prevent lipid tails from packing too closely
Cholesterol: the rigid four carbon rings also prevent the membrane from being too fluid
1st and 2nd choices only
1st and 3rd choices only
2nd and 3rd choices only
All of the above
None of the above

3. Which of the following pairing/s is/are correct?

Membrane proteins: help maintain concentration gradients
Concentration gradient: the difference of amounts of solutes on two sides of a solution
Solutes: are the substances dissolved in a solution
1st and 2nd choices only
1st and 3rd choices only
2nd and 3rd choices only
All of the above
None of the above

4. Which of the following pairing/s is/are correct?

Molecules: move around randomly on their own
Molecules: when concentrated create an unstable environment due to increased collisions of molecules
Diffusion: is the movement of molecules from a region of low concentration to a region of high concentration
1st and 2nd choices only
1st and 3rd choices only
2nd and 3rd choices only
All of the above
None of the above

5. Which of the following pairing/s is/are correct?

Passive movement: movement of molecules that is energetically favorable b/c free energy is released in the process
Passive movement: requires energy from outside of the system
Passive movement: occurs as molecules move up their concentration gradients
1st and 2nd choices only
1st and 3rd choices only
2nd and 3rd choices only
All of the above
None of the above

6. Which of the following pairings/s is/are correct?

Active movement: is a passive process
Active movement: is an energetically unfavorable process
Active movement: releases free energy
1st and 2nd choices only
1st and 3rd choices only
2nd and 3rd choices only
All of the above
None of the above

7. Which of the following pairing/s is/are correct?

Transport channels: allow movement of all ions through
Transport carriers: allow movement of all ions through
Channels : passive movement
Carriers: active movement
1st and 2nd choices only
1st and 3rd choices only
1st, 2nd, and 3rd choices only
2nd and 3rd choices only
All of the above
None of the above

8. Which of the following paring/s is/are correct?

Active transporters: movement of molecules up their concentration gradients
Active transporters: require energy
Active transporters: ATP dependent pumps, antiporters, symporters
1st and 2nd choices only
1st and 3rd choices only
2nd and 3rd choices only
All of the above
None of the above

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BI110 Lecture Notes - Lecture 7: Osmosis, Cytosol, Hydrophile

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