Post on 29-Jul-2015
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States of Matter
You will remember from science that matter exists in different forms depending on the amount of energy the atoms have
We only need to know about liquids, solids and gases
When molecules are in a liquid or in a gas they move and get mixed together
This is important in living organisms Let’s look at the States of matter:
Kinetic energy is the energy of
movement
Remember that in the solid the molecules only vibrate – they have low kinetic energy
In a liquid the molecules have more kinetic energy and kind of roll over each other
In a gas the molecules have a lot of kinetic energy and move randomly in any direction
If you have internet click on this animation which shows the different states. You will need to look at water and increase the pressure on the one axis
Using a diffusion tube
Litmus paper tells us what the pH of something is; that is if it is acidic or alkali
For the experiment with ammonia we will use red litmus paper
It should change to blue when ammonia is present (because it is alkali)
Potassium permanganate molecules mix with the water moleculesThe purple colour slowly spreads throughout the water: this is diffusion
Diffusion in Living Organisms
Living organisms rely on diffusion to move substances in and out of cells and organs
This only works when there is a diffusion gradient: when you look at the examples think about how the diffusion gradient is kept as steep as possible
Diffusion in the lungs
we need oxygen in our bodies for respiration
This oxygen is used in cells to make energy by respiration
Carbon dioxide is a product of respiration that we must get rid of!
We take oxygen in and expel carbon dioxide in the lungs
The lungs are a system of branching tubes that end in many small structures called alveoliThese are surrounded by blood vessels
Look at how gases move in/out of alveoliHow do you think we keep the oxygen content in the alveoli high even though oxygen is moving into the blood constantly?
Gaseous Exchange in a Leaf
Leaves need carbon dioxide for photosynthesis
The carbon dioxide has to go into the palisade cells at the top of the leaf
Oxygen is a product of photosynthesis; this must move out of the palisade cells
Let’s look at a leaf in section first
Can you see the Palisade cells? The green dots are chloroplasts where photosynthesis takes place. They are also found in spongy mesophyll cellsNote the stomata which are openings through which gases can pass
This picture shows how oxygen and carbon dioxide move in and out of the leafTo get in and out of cells they must diffuse across the membraneThe cells have large air spaces to allow gases to move around
Diffusion in the small intestine
When you eat your food is digested, or broken down, into small molecules
These can now diffuse out of the gut and into the blood – this is called absorption
This happens in a place called the ileum in the small intestine
To increase the surface area for absorption the ileum has tiny projections called villi:
This is what villi look likeLook at the scale bar to get an idea of how small they are - there are 1000µm in 1mm
This is what a villus looks like insideNote the thin layer of cells around it – this makes the distance for diffusion shorterAlso see there is a capillary with blood flowing through to take up digested food and move it away
The lacteal also absorbs some digested food – we will learn more about all of tis later this year