Flashcards in Cells - Transport across cell membrane - 3.2.3.2 - Simple and Facilitated Diffusion Deck (23)
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1
Diffusion is an example of
passive transport - energy comes from natural, inbuilt motion of particles
2
In diffusion the motion of the particles is described as
random motion
3
In diffusion the direction of particle movement is
from an area of high concentration to an area of lower concentration - until equilibrium is reached
4
Molecules which can diffuse through the phospholipid bilayer include
non-polar, small molecules e.g. oxygen and carbon dioxide
5
Facilitated diffusion and diffusion differ because
facilitated diffusion requires a special protein molecules e.g. carrier or channel protein
6
Facilitated and diffusion are similar because
they are both passive and molecules move with their concentration gradient (high to low)
7
Molecules which do not diffuse easily across the phospholipid bilayer are
large, charged ions and polar molecules e.g. glucose
8
What prevents large, charged and polar molecules diffusing across the plasma membrane
the hydrophobic fatty acids tails of the phospholipid bilayer
9
Name the two types of protein molecules involved in facilitated diffusion
carrier and channel proteins
10
Carrier proteins transport
molecules like glucose
11
How do carrier proteins transport molecules like glucose?
glucose binds to the carrier specifically, carrier changes shape, releasing it onto the other side of the membrane
12
Channel proteins transport...
water soluble ions
13
How do channel proteins transport molecules like water soluble ions?
ion binds causing a change in the shape of the channel allowing the ion to enter the cell
14
State 3 factors that affect the rate of diffusion
surface area, concentration gradient and thickness of exchange surface
15
For maximum diffusion what adaptations does the exchange surface need
large surface area
Large concentration gradient
Thin - short diffusion distance
16
Name 2 exchange surfaces in living organisms (humans)
alveoli and villi
17
Where does diffusion take place in living organisms
1. alveoli - exchanging oxygen and carbon dioxide
2. Villi - exchange soluble molecules into the blood
3. Leaf (stomata) - carbon dioxide and oxygen
4. Roots - water
18
How would diffusion be affected if the alveoli surface area is doubled
doubles
19
How would diffusion be affected if the surface area is halved but the oxygen concentration gradient is doubled
no change
20
How would diffusion be affected if the oxygen concentration is halved and the total thickness of the exchange surface is doubled
decreases 4 fold/quarter
21
what is a protein channel filled with?
water
22
What do carrier proteins and channel proteins have in order to transport molecules across the membrane?
binding sites
23
