Biology AS AQA Unit 1 Cells and Movement in and out of them

Made these notes for my year 12 summer exam to revise and read over. There are spelling mistakes in most of my files but due to the busy exam schedule I had no time to correct them (sorry).

Most files have more information than what is needed but I feel it helps you feel more confident walking into the exam if you have a greater knowledge background and may help when having to apply knowledge to questions. Good luck :)

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  • Created by: Chelcie
  • Created on: 02-09-13 12:34
Preview of Biology AS AQA Unit 1 Cells and Movement in and out of them

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Cells and movement in and out of them
Magnification = size of image
Actual size of object
Kilometre km
Metre m
Millimetre mm
Micrometre m
Nanometre nm
x 10-3 when going down table
RESOLUTION: The minimum distance apart two objects can be in order for them to appear separate.
Cold- To reduce enzyme activity.
Isotonic- To prevent organelles bursting/shrinking as a result of osmosis by having same water
potential as original tissue.
Buffered- to maintain pH.
Cells are broken up by a homogeniser to release organelles. Homogenate (resultant fluid) is filtered
off to remove any complete cells/debris.
Process which fragments, in the filtered homogenate, are separated by an ultracentrifuge.
This spins tubes at high speed to create a centrifugal force.
The heaviest organelles (nuclei) are forced to the bottom of the tube and form sediment/pellet
Supernatant (fluid at the top) is removed leaving the sediment of nuclei.
Next heaviest organelles (mitochondria) are forced to the bottom.
Nuclei Mitochondria Lysosomes Ribosomes
The electron beam has a very short wavelength and hence has high resolving power.
The electrons are negatively charged so are focused using electromagnets.
Can resolve objects 0.1 nm apart.
A near vacuum has to be created otherwise molecules in the air will absorb the electrons.
Two types: transmission and scanning.

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An electron gun produces a beam of electrons from below which are focused onto the specimen by
a condenser electromagnet.
The beam passes through a thin section of the specimen. The parts of the specimen that absorb
electrons appear dark.
An image is created called a photomicrograph.
0.1nm resolving power.
Main limitations are:
Vacuum, therefore no living specimens.…read more

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Nuclear pores
Allow passage of large molecules, such as RNA, out of nucleus.
Granular, jelly like material that makes up the bulk of the
Is the DNA inside the nucleoplasm. This is the diffuse form that chromosomes take up when the cell
is not dividing.
Small spherical body within the nucleoplasm.
It manufactures RNA and assembles the ribosomes.
Site of respiration.
Responsible for production of ATP from carbohydrates.
Double membrane
Double membrane surrounds the organelle.…read more

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Formed by Golgi apparatus. It is an organelle containing enzymes e.g. protease and lipase.
Lysosomes isolate potentially harmful enzymes from the cell.
Its functions are to:
Break down material ingested by phagocytic cells
Exocytosis - release enzymes to the outside of the cell (to destroy material outside cell)
Autolysis- completely break down cells after they have died
80S type ­ found in eukaryotic cells
70S type- prokaryotic cells
Ribosomes have two sub units which contain ribosomal RNA and protein.
Protein synthesis.…read more

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Insoluble in water
Soluble in organic solvents
Main groups are triglycerides (fats and oils), phospholipids and waxes.
The main role of lipids is plasma membranes.
Phospholipids contribute to the flexibility of membranes and transfer of lipid soluble
substances across them.
Lipids are an energy source
Triglycerides have 3 fatty acids combined with glycerol.
Each fatty acid forms a bond with glycerol in a condensation reaction.
Hydrolysis of a triglyceride therefore produces glycerol and three fatty acids.…read more

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MOSAIC: because the proteins embedded in the phospholipid bilayer vary in shape, size and pattern.
MODEL: because it's only a theory.
Diffusion is the net movement of molecules or ions from a region where there is a high
concentration to a low concentration.
DYNAMIC EQUILIBRIUM: Where the number of particles on each side remain the same although the
particles are continually changing position.…read more

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The cell membrane will break, bursting the cell.
Water potential is higher than plant cell, water enters and the protoplast swells which makes the
plant turgid.
If same water potential, there is no osmosis and the protoplast is in an incipient plasmolysis state,
where the protoplast begins to pull away from the cell.
Lower water potential causes the protoplast to shrink causing the cell to be plasmolysed where it
has pulled away from the cell wall.…read more

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Glucose is constantly used by cells
during respiration. This helps to maintain concentration gradient.
The villis muscles that contract and relax mix the contents of the small intestine, hence keep the
concentration gradient.
1. Sodium ions are AT out of epithelial cells by sodium potassium pump into blood. This
takes place in one type of protein carrier molecule found in the CSM of epithelial cells.
2.…read more

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Vibrio cholerae is transmitted by ingestion of water, or food, that has been contaminated with faecal
material containing pathogen.
1. Most of pathogen is killed in stomach acid however a few survive
2. Surviving bacterium reach small intestine and use flagella to propel them through mucus
lining of intestinal wall.
3. They then produce toxic protein. Protein has 2 parts.…read more


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