YV4-cells-4.5 Membrane transport Diffusion

• Biologie
• Middelbare school
• vwo
• Leerjaar 4

Ch 4 Cells 

4.5 Membrane transport

Diffusion 

Let's check what you memorized from last lesson?

We will start with Quiz Organelles in Lesson Up..

Want to practice some more with the organelles?....

www.cellsalive.com

Learning goals Membrane transport

Membrane Transport

• You can explain how a membrane is built
• You can explain that a membrane is (semi )permeable

Diffusion and Osmosis

• You can explain how, by means of diffusion and osmosis, compounds can pass through the cell membrane
• You can explain what consequences this transport might have for cells

Key words

Cell membrane transport

Permeable

Hydrophilic

Hydrophobic

Aquaporine

Diffusion

Facilitated diffusion

Channel protein

Carrier protein

(Semi) permeable

Osmosis

01:51

What molecules can pass the cell membrane without any difficulty?

1. charged particles / ions
2. glucose
3. water
4. oxygen and carbondioxide

02:14

'With the concentration gradient' means from...

1. a higher concentration to a lower
2. a lower concentration to a higher

04:51

In what organelle is the energy-rich ATP generated?

06:52

Pancreatic cells (alvleeskliercellen) create enzymes. When these proteins are completed, they need to be excreted.

By what way do enzymes leave the pancreatic cells?

1. simple diffusion
2. facilitated diffusion
3. active transport
4. exocytosis

04:51

Active transport requires...

Cell membrane transport

1. Passive: no energy necessary, concentration driven

- (Facilitated) Diffusion

- Osmosis

2. Active: costs energy

The cell membrane comprises of two layers of phospholipids

Hydrophylic out- and inside

Hydrophobic layer in between

Not permeable to water

aquaporine

A protein channel that allows the diffusion of water in and out the cell

facilitated diffusion

diffusion is made easer by protein channels through the cell membrane

Which diagram best shows the end result of diffusion?

1. F
2. G
3. H
4. J

Diffusion is the movement of molecules from an area of _____ concentration to an ______ concentration

1. high, low
2. high, high
3. low, high
4. low, low

Which is true of passive transport?

1. Moves from low to high concentration
2. Requires energy
3. Moves from high to low concentration
4. Moves against the gradient

Learning goals Diffusion and Osmosis

You can explain the process of diffusion and osmosis

You know why osmosis is important for the support of plants

You can explain why you shouldn't put salt on a snail

(" niet op iedere slak zout leggen" )

Describe what happens in the video

Diffusion

• Molecules going through the cell membrane
• Molecules (" go with the flow") move from a high to a low concentration
• The movement of molecules is random until a balance is reached
• This is a form of passive transport, because the energy comes from the molecules themselves

Try to describe what happens using this new information

How does heat affect diffusion?

1. It has no effect
2. More heat means faster diffusion
3. More heat means slower diffusion

Effect distance on diffusion

The shorter the distance, the faster the molecules will have equal concentrations throughout the space

Effect surface area on diffusion

The bigger the surface area, the faster the molecules will be evenly distributed over the available area

Effect concentration gradient on diffusion

The bigger the difference in concentration, the faster diffusion will happen

Misconceptions with diffusion

• Molecules want the concentration to be equal/ try to make the concentrations equal. 
• 
  
• Molecules stop moving after the concentrations are equal. 

Molecules never stop moving, but when concentrations are equal there are equal amounts of molecules moving in every direction = balance

Molecules have no mind to think with, they move randomly

Now... can you think of any examples of diffusion in living organisms?

What affects the rate of diffusion?

Diffusion is faster

High temperature

Large surface area

Small surface area

Low temperature

Large particles

Small particles

Large concentration gradient

Small concentration gradient

Shorter distance in between two regions

Longer distance in between two regions

Special type of diffusion = facilitated diffusion: faster movement (but still no energy or ATP needed)

1.  By channel proteins: charged ions e.g. Na+, Cl-

2. By carrier proteins:  larger polar molecules e.g. sugars, amino acids 

Channel protein vs. carrier protein

Molecule attaches to the carrier protein at binding site --> carrier protein changes shape --> molecule gets 'delivered' through the cell membrane