Diffusion & Facilitated Diffusion Flashcards Preview

AP Biology 2014 > Diffusion & Facilitated Diffusion > Flashcards

Flashcards in Diffusion & Facilitated Diffusion Deck (18)
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1
Q

What is passive transport?

A

the diffusion of a substance across a biological membrane and does not require energy (down a concentration gradient)

2
Q

What are the 5 different passive transport processes?

A
  1. diffusion
  2. osmosis
  3. plasmolysis
  4. facilitated diffusion
  5. countercurrent exchange
3
Q

How can the rates of passive transport increase?

A
  • higher concentration gradients
  • higher temperatures
  • smaller particle size
4
Q

What is a concentration gradient?

A

The region along which the density of a substance increases or decreases, and doesn’t require any work to happen. Each substance diffuses independently down its own concentration gradient and isn’t affected by other substances’ concentration gradients.

5
Q

What is diffusion?

A

The net movement of substances from an area of higher concentration to an area of lower concentration. It results from random movement of molecules, but the diffusion of a population may be directional.

6
Q

Is diffusion spontaneous or nonspontaneous?

A

spontaneous, because it doesn’t require any energy

7
Q

What is the difference between diffusion and osmosis?

A

osmosis is a type of diffusion where water diffuses across a semi-permeable membrane

8
Q

What is facilitated diffusion?

A

the diffusion of solutes or water through channel proteins or carrier proteins in the plasma membrane (the lipid bilayer does not allow polar molecules and ions to go through)

9
Q

Why is facilitated diffusion considered passive transport?

A

Because the solute is moving down its concentration gradient, a process requiring no energy. (Also, it speeds the transport of a solute by providing passage through the membrane without altering the direction of transport.)

10
Q

What are transport proteins?

A

a transmembrane protein that helps a specific substance to cross the membrane

11
Q

What are the two types of transport proteins?

A
  1. channel: provides a hydrophilic tunnel to allow specific molecules to pass the membrane
  2. carrier: binds to molecule and changes shape as it moves a solute across the membrane

Both proteins can transport the solute in either direction, but the net movement is down the concentration gradient of the solute.

12
Q

What are the channel proteins that transport ions called?

A

ion channels, which function as gated channels that open or close in response to a chemical or electrical stimulus (some ions include: Na+, K+, Ca2+, or Cl-)

13
Q

What specialized type of channel protein facilitates the movement of water across the plasma membrane?

A

aquaporins

14
Q

What do carrier proteins facilitate the movement of?

A

the movement of ions AND some larger organic molecules, such as amino acids and glucose

15
Q

What happens when the concentration gradient is greater?

A

The initial rate of diffusion is faster. However, equilibrium is reached sooner when the concentration gradient is smaller due to the fewer number of solutes necessary to establish equilibrium.

16
Q

What happens when the temperature of solutions are greater?

A

The rate of diffusion is faster. Molecules at higher temperatures have more kinetic energy and move faster.

17
Q

What happens when the solute weight is greater?

A

The rate of diffusion is slower. All molecules at the same temperature have the same average kinetic energy. But remember: kinetic energy = 1/2 x mass x velocity2. Thus, lighter molecules move faster.

18
Q

Do small, noncharged particles, primarily gases (like carbon dioxide and oxygen), need facilitated diffusion?

A

no, they can diffuse through the plasma membrane without any help