Exchange Across Cell Membranes - Diffusion Flashcards

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1
Q

What is diffusion

A

The net movement of particles from an area of higher concentration to an area of lower concentration

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2
Q

What ways will molecules diffuse

A

Molecules will diffuse both ways

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3
Q

When will diffusion stop occuring

A

When all particles are evenly distributed around the liquid or gas

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4
Q

What is the concentration gradient

A

The path from an area of higher concentration to an area of lower concentration.particles diffuse down a concentration gradient

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5
Q

What type of process is diffusion

A

A passive process,in which no energy is needed

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6
Q

Why can oxygen and carbon dioxide diffuse easily through the cell membranes

A

Due to them being so small meaning they can pass through the phospholipids

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7
Q

Oxygen and carbon dioxide are non-polar what does this mean

A

This makes them soluble in lipids,so they can dissolve in the hydrophobic layer

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8
Q

What is it known as when molecules diffuse directly through a cell membrane

A

Simple diffusion

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9
Q

What are some examples of larger molecules that diffuse slowly

A

Amino acids,glucose

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10
Q

Why would charged particles diffuse slowly

A

They are water soluble and the centre of the bilayer is hydrophobic

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11
Q

What are examples of charges particles

A

Ions and polar molecules

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12
Q

What is facilitated diffusion

A

A process to speed up diffusion in which large or charged particles diffuse through carrier protein or channel proteins

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13
Q

What type of process is facilitated diffusion

A

A passive process not requiring energy

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14
Q

What are the three steps of carrier proteins

A

1) a large molecule attaches to o a carrier protein in the membrane
2) then,the protein changes shape
3) this releases the molecule on the opposite side of the membrane

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15
Q

How does the concentration gradient affect rate of diffusion

A

Teh higher it is,the faster the rate of diffusion.As diffusion takes place,the difference in concentration between thee two sides of the membrane decreases until it reaches an equilibrium

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16
Q

How does the thickness of the exchange surface affect rate of diffusion

A

Teh thinner the exchange surface (i.e. the shorter the distance the particles have to travel) the faster the rate of diffusion.

17
Q

How does the surface area affect rate of diffusion

A

The larger the surface area (e.g. of the cell-surface membrane) the faster the rate of diffusion

18
Q

What does facilitated diffusion depend on

A

The concentration gradient

The no. Of channel or carrier proteins

19
Q

How does the concentration gradient affect facilitated diffusion

A

The higher the concentration gradient,the faster the rate of facilitated diffusion. As equilibrium is reached,the rate of diffusion will level off.

20
Q

Why does facilitated diffusion depend on the no. Of channel or carrier proteins

A

Once all the proteins in a membrane are in use, facilitated diffusion can’t happen any faster.so the greater the number of channel or carrier proteins the faster the rate.