AQA AS Biology Unit 1 3.1.3 Cells and Movement In and Out of them

Notes on topic 3.1.3 from the AQA AS Biology specification.

I made these using my class notes the AQA AS Biology textbook and the specification.

If you have any corrections or queries please leave them in the comments and I'll try and help.

I hope these are useful :)

Good Luck with your exams :) **

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Revision: Unit 1 Biology and Disease 3.1.3 Cells and Movement In and Out of them

Light microscope:

Maximum magnification is x1500.
Maximum resolution is 0.2µm (200nm).
Focusing method is eyepiece lens and objective lens.
Specimen preparation is
o Wet mount on slide
o Stained
o Can be living or dead…

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Image is viewed on a fluorescent screen and then that image is fed onto a computer screen.
Advantages
o 3D images can be viewed.
o Specimens can be viewed at a higher magnification and resolution so sub-cellular
images can be seen.
Disadvantages
o Artefacts
Features that are caused by the…

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o Site of respiration.
Do have ribosomes.
o Site of protein synthesis.
o They are smaller than those found in eukaryotic cells.

Eukaryotic Cells

Have a "true" membrane-bound nucleus and membrane bound organelles.
o Animal, plant and fungal cells are Eukaryotic.

Animal Cell




The Nucleus

Relatively large (10-20µm).
Surrounded by…

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1-10µm
Surrounded by a double layer of membrane.
Inner layer is folded into a series of cristae which provide a large surface area.
Central area is filled with fluid called the matrix.
o Matrix contains DNA and Ribosomes.

Ribosomes

The site of Protein Synthesis.
Can be found free in the…

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Watery liquid containing dissolved materials.

Cytoskeleton

System of protein microtubules and microfilaments which give the cell some support.

Centrioles

A pair of short cylinders. Each made of nine fibres.
Form a spindle-shaped structure of protein fibres on which the chromosomes move during
nuclear division.

Additional features found in plant cells…

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1. Cells are suspended in an ice cold, isotonic fluid.
Ice cold to reduce enzyme activity.
Isotonic to prevent osmotic damage to the organelles.
2. Cells are then broken open in a homogeniser.
Disrupts the cell membrane but leaves the organelles intact.
Any whole cells or debris is filtered off…

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o Shake the sample with ethanol in a boiling tube. Pour the liquid into another boiling
tube full of water.
A milky white precipitate forms if lipids are present.
Contain the elements carbon C, hydrogen H, and oxygen O.
o The large numbers of C-C and C-H bonds mean that…

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o Carrier proteins
o Channel proteins
o Cell surface antigens
o Components in energy transfer reactions such as respiration and photosynthesis
Proteins and lipids have short branching carbohydrate components, glycoproteins and
lipoproteins.
Membranes also contain cholesterol. They fit neatly into the bilayer between the
phospholipid molecules.




Movement in and out…

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o The surface area between the two regions
The larger the surface area, the faster the rate of diffusion.
o The temperature
At higher temperatures molecules have more kinetic energy and diffuse
more quickly.

Facilitated Diffusion

Diffusion sped up by specific membrane proteins. Occurs down a diffusion gradient and
therefore…

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Osmosis in Animal Cells

In hypotonic solutions, water will move by osmosis into the cells which will swell until they
eventually burst.
In hypertonic solutions, water will move by osmosis out of the cells which will then shrink.
To prevent this from happening, animals need to osmoregulate.
o Control the…

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