Transport through membranes

• Biologie
• Middelbare school
• havo
• Leerjaar 4

which homework questions would you like me to discuss?

AIM

• You can explain what diffusion and osmosis are and describe the role of osmosis in the rigidity of plants.
  
• You can describe how the transport of substances occurs through (cell) membranes.

What is concentration?

Concentration

• In organisms, substances are dissolved in the cytoplasm of the cell. 
• Living organisms require substances to enter and exit each cell.
• Chemical reactions take place in cells that can change the concentrations of solutes.

Diffusion

The movement of a substance from an area of high concentration to an area of low concentration of that substance.

Diffusionspeed depends on the temperature.

Osmosis

= diffusion of water through a semipermeable membrane

= the movement of water from a place with a low osmotic pressure to a place with a high osmotic pressure

Osmosis 

types of membranes

permeable = 

a membrane with big pores, water and substances can move through the pores

semi-permeable or selectively permeable = 

very small pores, only water can go through, not the dissolved substances

Osmotic pressure

How much water moves is determined by the osmotic value on both sides of the membrane.

  

Osmotic value: amount of dissolved substances in the water.

High osmotic pressure: a lot of dissolved substances.

Low osmotic presurre: a few dissolved substances.

Water flows of a low > high osmotic value.

The solution with the highest osmotic pressure  has a suction force on the water from the other solution. This suction force is called the osmotic pressure.

Osmosis in animal cells

hypotone solution OUTSIDE of the cell

water goes in by osmosis and the cells burst

isotone solution OUTSIDE of the cell

no osmosis, no difference in osmotic pressure

hypertone solution OUTSIDE of the cell

water leaves the cell through osmosis, the cells shrink

osmosis in a plant cell

passief transport

kost geen energie

verloopt altijd door een concentratieverschil

osmose en diffusie

Active transport, from low to high, costs energie = ATP.

gaat tegen de concentratiegradiënt in

kost wel energie

exo/endocytose

Exocytose:afsnoeren blaasjes (actief)

Endocytose: opnemen stoffen

-> endosoom.

Voeding opnemen: fagocytose

WHAT

beginner: read page 9-18 + make notes

intermediate: make exc. 1-9

HOW

individual

in silence

NEED HELP

1. look at the text page 9-18 in reader
2. go on to the next excercise
3. AKS TEACHER when passing your desk

get to work - IN SILENCE

What do you remember from this class?

Do you need more explanation?