Diffusion and Facilitated Diffusion

?
  • Created by: Lotto65
  • Created on: 19-11-16 13:44
Is there net movement if particles are evenly spread?
No
1 of 37
What causes diffusion?
If there is a higher concentration of particles in one region than another
2 of 37
What is diffusion?
The passive movement of particles from a region of high to low concentration
3 of 37
Why does diffusion only happen in fluids?
Their particles move randomly in continuous motion
4 of 37
What is passive movement?
Without the need for energy
5 of 37
Does movement of particles occur in both directions in diffusion?
Yes - more move from high to low than low to high
6 of 37
What are the requirements for diffusion to occur across membranes?
There is a concentration gradient; The membrane is permeable to that particle
7 of 37
Give an example of a substance membranes are permeable to?
Oxygen
8 of 37
Give an example of something membranes are not permeable to?
Cellulose
9 of 37
What does partially permeable mean?
Membranes allow some substances to diffuse through but not others
10 of 37
Explain simple diffusion
Some particles can move through the phospholipid molecules to get into the cell
11 of 37
Explain facilitated diffusion
Some substances are unable to pass through the phospholipids as they are to big etc so channel proteins are needed to let them diffuse through
12 of 37
True/ false: A channel protein will allow different substances through
False- they are specific to a certain substance
13 of 37
What can cells control? How?
Which substances pass through their plasma membrane by inserting certain types of channel protein into the membrane
14 of 37
What are cells not able to control?
The direction of movement of particles across a membrane
15 of 37
Is facilitated like simple diffusion in that it is high to low concentration?
Yes
16 of 37
Is facilitated diffusion a passive process?
Yes
17 of 37
Name to ions that need channel proteins to let them pass through by facilitated diffusion
Sodium and potassium ions
18 of 37
Where are potassium ions needed? Why?
Axon membranes in neurons for use during an action potential
19 of 37
When are the potassium channels closed?
When the membrane is polarised (positive charge inside and negative outside)
20 of 37
When do potassium channels open?
In response to depolarisation across the membrane ( more potassium ions inside than outside)
21 of 37
What happens to the polarisation of the membrane when potassium ions leave?
It is repolarised
22 of 37
How long do potassium channels remain open?
Very short time
23 of 37
What temporarily closes the pore of the channel before it returns to its closed state?
A globular sub-unit
24 of 37
How do you describe potassium channels?
Voltage-gated
25 of 37
Particles from high to low concentration gradient move ... the concentration gradient
Down
26 of 37
Generally, what sort of particles can pass through the phospholipid bilayer by simple diffusion?
Non-polar molecules
27 of 37
Why can charged ions not pass through the phospholipid bilayer by simple diffusion?
The centre of membranes is hydrophobic and charged molecules repel uncharged molecules
28 of 37
Do small particles pass through the phospholipid bilayer easier than large particles?
Yes
29 of 37
Can polar molecules with partial positive and negative charges on their surface diffuse through the bilayer?
At low rates
30 of 37
Give an example of simple diffusion in the body
In the cornea of the eye- there is no blood supply so it gains oxygen by diffusion
31 of 37
Explain how the cornea gets oxygen
Oxygen diffuses into corneal tears that coat the cornea so there is a high concentration. There is a low concentration in the corneal cells due to aerobic respiration so oxygen diffuses through the plasma membrane into corneal cells
32 of 37
Name a property of the channels for facilitated diffusion
Their holes are very narrow
33 of 37
What are the walls of the channel made of?
Protein
34 of 37
What ensures the protein channels are specific?
The diameter and chemical properties - too large to fit through or too small to bond with amino acids
35 of 37
How many protein sub units make up a protein channel?
4
36 of 37
What happens to the potassium before it goes through the channel?
It breaks the bonds between itself and surrounding water molecules and bonds with a series of amino acids in the narrowest part of the pore so it is the size to go through
37 of 37

Other cards in this set

Card 2

Front

What causes diffusion?

Back

If there is a higher concentration of particles in one region than another

Card 3

Front

What is diffusion?

Back

Preview of the front of card 3

Card 4

Front

Why does diffusion only happen in fluids?

Back

Preview of the front of card 4

Card 5

Front

What is passive movement?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Cellular processes and structure resources »