IT’S A IT’S A GREEN WORLDGREEN WORLD

WATER, WATER WATER, WATER EVERYWHEREEVERYWHERE

StarterStarter

Raise your hand when you can smell Raise your hand when you can smell the perfume…………………the perfume…………………

Why is perfume put on Why is perfume put on the warm places of the warm places of the body such as the the body such as the neck and wrists? neck and wrists?

Water, water Water, water everywhereeverywhereLearning objectivesLearning objectives Describe osmosisDescribe osmosis Describe the effects of Describe the effects of

the uptake and loss of the uptake and loss of water on plant and water on plant and animal cells.animal cells.

Explain the key terms: Explain the key terms: flaccid, plasmolysed, flaccid, plasmolysed, turgid, crenation and turgid, crenation and lysislysis

Success criteriaSuccess criteria Know the definition of Know the definition of

osmosisosmosis Be able to understand Be able to understand

and describe the effects and describe the effects of different of different concentrations of sugar concentrations of sugar solutions on plant cells solutions on plant cells

Be able to understand Be able to understand and therefore use the and therefore use the key terms correctly key terms correctly

Recap of diffusion

Diffusion and concentrationWhy can the student smell the sock from a distance?

The sock can be smelt because sweat and other molecules are moving away from it and spreading out in the air. This is called diffusion.

Where is the smell strongest?

The smell is strongest at the sock. The smell becomes weaker further away from the sock.

Changing concentrations

The rate of diffusion depends on several factors, such as the distance the particles have to travel and the difference in concentration.

Molecules diffuse until they are evenly spaced apart and equilibrium is reached.

During diffusion molecules move from an area of high concentration to an area of low concentration. They are said to move down a concentration gradient.

Diffusion is a passive process which means that no energy is needed.

highconcentration

lowconcentration

What is osmosis?

water

glucose

partially-permeablemembrane

(visking tubing)

Osmosis is the diffusion of water molecules from a low concentration solution to high concentration solution, across a partially-permeable membrane.

A partially-permeable membrane has holes in it that permit water molecules through but are too small to allow larger molecules through. Osmosis can be demonstrated using visking tubing filled with a solution and placed in a beaker of pure water.

Osmosis demoOsmosis demo

BeforeBefore After After

Dilute vs. concentrated

Concentrated solutions have a low concentration of water molecules.

Dilute solutions have a high concentration of water molecules.

During osmosis, water molecules diffuse from pure water or dilute solution to more concentrated solutions.

pure water dilute solution concentratedsolution

Support in plant cellsSupport in plant cellsWater can move in and out of a plant cell Water can move in and out of a plant cell

through itsthrough its Cell wall - permeableCell wall - permeable Cell membrane – partially permeableCell membrane – partially permeable

The presence of water in a plant cell gives The presence of water in a plant cell gives itit

Shape Shape Support Support

The cell wall also provides supportThe cell wall also provides support

Support in plant cellsSupport in plant cells

What happens when water uptake What happens when water uptake and water loss are not balanced a and water loss are not balanced a plant?plant?

The plant will wilt.The plant will wilt.

Osmosis and cellsPlant and animal cells are surrounded by a partially-permeable plasma membrane. This allows water and other small molecules to diffuse across.

plant cell red blood cell

cell wall

Plant cells additionally have a strong cell wall surrounding the membrane which offers support and protection.

plasmamembrane

HD onlyHD only - More on osmosis - More on osmosisWhen a potato chip is in salt water the When a potato chip is in salt water the

chips become flaccid (soft and floppy). chips become flaccid (soft and floppy).

WHY?WHY?

There is a higher concentration of water There is a higher concentration of water molecules inside the potato cells than molecules inside the potato cells than outside. Water leaves the cells by outside. Water leaves the cells by osmosis and the cells become osmosis and the cells become plasmolysed.plasmolysed.

Osmosis and plant cells

Osmosis and animal cellsAnimal cells do not have a cell wall. This means they respond differently to plant cells to the gain and loss of water.

In concentrated solutions, water loss causes the cells to shrink. When this happens to red blood cells, it is called crenation.

In dilute solutions, osmosis can cause animals cells, such as red blood cells, to swell up and burst. This is called lysis.

Osmosis and animal cells

Osmosis in onion cellsOsmosis in onion cells Follow instructions on w/s B4b5 – Follow instructions on w/s B4b5 –

osmosis in onion cellsosmosis in onion cells

OsmosisOsmosisWeak solution Concentrated solution

crenated

NormalTurgid

Normal

Plasmolysed

Lysed

Plenary - Predicting Plenary - Predicting osmosisosmosis

Water, water Water, water everywhereeverywhereLearning objectivesLearning objectives Describe osmosisDescribe osmosis Describe the effects of Describe the effects of

the uptake and loss of the uptake and loss of water on plant and water on plant and animal cells.animal cells.

Explain the key terms: Explain the key terms: flaccid, plasmolysed, flaccid, plasmolysed, turgid, crenation and turgid, crenation and lysislysis

Success criteriaSuccess criteria Know the definition of Know the definition of

osmosisosmosis Be able to understand Be able to understand

and describe the effects and describe the effects of different of different concentrations of sugar concentrations of sugar solutions on plant cells solutions on plant cells

Be able to understand Be able to understand and therefore use the and therefore use the key terms correctly key terms correctly