Chapter 4(Passive transport) Flashcards Preview

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Flashcards in Chapter 4(Passive transport) Deck (29)
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1
Q

What is passive transport? Energy required?

A

When molecules move across the membrane down their chemical or electrochemical gradients. No energy is required.

2
Q

Three types of passive transport.

A

Simple diffusion, facilitated diffusion and diffusion through ion channels.

3
Q

What is simple diffusion based on?

A

Random thermal motion

4
Q

A population of molecules always does what?

A

Moves down its’ concentration gradient.

5
Q

Rate of simple diffusion depends on what?

A

magnitude of the driving force, membrane surface area, permeability of the membrane.

6
Q

What influences the permeability of a cell? Which is the strongest?

A

Lipid solubility of the diffusing substance, size and shape of diffusing molecules, temperature, membrane thickness. Lipid solubility.

7
Q

What are most substances in the body? Name some.

A

Hydrophillic, do not penetrate lipid layers easily. Fatty acids, steroid hormones, thyroid hormones, oxygen, carbon dioxide, and fat soluble vitamins.

8
Q

What is facilitated diffusion?

A

When molecules cross by way of transport proteins in the membrane.

9
Q

What is a carrier in facilitated diffusion?

A

A transmembrane protein that binds molecules on one side of a membrane and transports them to the other side.

10
Q

Net flux of facilitated diffusion depends on what?

A

The frequency of the solute binding to the carrier molecule on the two sides of the membrane, so net transport occurs from the side with a greater frequency of binding.

11
Q

Two factors affecting the binding of a solute to a carrier.

A
  1. the affinity of the binding site on the carrier. 2. the concentration gradient of the solute across the membrane.
12
Q

Rate of facilitated diffusion is determined by what?

A

transport rate of individual carriers, the number of carriers in the membrane, and the magnitude of the concentration.

13
Q

What is a channel?

A

A transmembrane protein that transports molecules via a passageway or pore that extends from one side of the membrane to the other.

14
Q

How does most water cross the membranes? How else can it happen?

A

Through aquaporins. They only permit water and not solutes. Through ion channels

15
Q

What are the three principles of diffusion?

A

Electrochemical gradient, osmosis and diffusion across membrane

16
Q

What is active transport?

A

Movement of molecules up their concentration gradient.

17
Q

What is primary active transport?

A

Uses ATP or some other chemical energy directly to transport substances.

18
Q

What is secondary active transport?

A

Powered by a concentration gradient or an electrochemical gradient that was previously created by primary active transport.

19
Q

What are pumps?

A

Transport proteins that carry out active transport. Ability to harness energy to drive transport of molecules in preferred direction.

20
Q

What is the difference between pumps and carriers?

A

Pumps have greater affinity for molecules on one side of the membrane.

21
Q

What results from active transport?

A

One side of the membrane becoming more concentrated.

22
Q

What is ATPase

A

membrane proteins that primarily perform active transport function as transport protein and as an enzyme.

23
Q

Why is the sodium potassium pump important?

A

Electrical signalling in neurons and absorption of glucose by intestinal epithelial cells.

24
Q

For each Na, K pump cyclce, how many molecules move out and in. Can they move in either direction?

A

Three Na are transported out and two K are transported in. No, they are unidirectional.

25
Q

Where is the energy stored for secondary transport?

A

In a Na+ or H+ concentration gradient

26
Q

How does Secondary use ATP?

A

Indirectly uses ATP because Na+/K+ pumps are driven by ATP

27
Q

What affects the rates of active transport?

A

Rate of transport by individual pump proteins and the number of pumps that are present in the membrane.

28
Q

Flow of water across a membrane is always what?

A

Passive, unaffected by membrane potentials and is always driven by its own concentration gradient

29
Q

What is osmosis?

A

The flow of water across a membrane down its concentration gradient