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Unit 1

Cells and transport
Cells and their function:
Nucleus- largest organelle which is surrounded by a nuclear envelope (double membrane)
which contains pores. The pores are used for exchange of substances i.e. mRNA. The outer
layer of the membrane contains ribosomes and is continuous with the endoplasmic reticulum.

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Prokaryotes (bacterium) Eukaryotes (mammals, green plants, fungi)
No nucleus, instead free-floating DNA which is long Contains a nucleus
and coiled up as a strand or DNA which is in a
plasmid (small loops of DNA which contains genes
for antibiotic resistance, for example)
Contains a cell wall but without cellulose…

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denser parts, and this is where the electrons have been absorbed more. TEMS's are good as
they give high resolution, so details can be seen within the cell, however they have to be used
on thin specimens which are dead, and the image is black and white.
Scanning electron microscopes-…

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condense to make three ester bonds, and three water molecules are released.
Fatty acids can be either saturated (don't have any double bonds between their carbon
atoms) or unsaturated (have double bonds between the carbon atoms).

The fluid mosaic model:
The Fluid mosaic model describes the arrangement of the phospholipid…

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Diffusion is the net movement of particles (molecules or ions) from an area of a higher
concentration to an area of lower concentration, down a concentration gradient.
The process is passive, therefore ATP is not required. However, energy needed for the
process comes from the kinetic energy of the…

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The higher the concentration of water molecules, the higher the water potential. Pure water
has the highest water potential at 0; all solutions have a lower water potential than pure

Active transport
Active transport happens when molecules move from low to high against a concentration
gradient, requiring energy from…

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constantly flowing, so it replaces and takes away glucose and ions.

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The cholera bacterium produces a toxin called choleragen.
The toxin binds to the epithelial cells lining the small intestine; this causes chloride ion protein
channels in the plasma membrane to open, so more Cl- ions move into the small intestine
lumen. This build up lowers the water potential of…

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which hydrolyses protein) and mucus. Peristalsis of the stomach turns food into chime (acidic
The small intestine is made up of the duodenum and ileum.
The chime is moved along the small intestine by peristalsis in
the duodenum, bile (alkaline) and pancreatic juice neutralise
the acidity of the chyme,…

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Starch is made from two polysaccharides, 20% is amylose
and 80%amylopectin. Amylose is in a helix, amylopectin is
branched. They are both long chains of a-glucose linked
together by glycosidic bonds, formed in condensation
reaction and are both compact so can be stored in large
amounts for release of…




great notes, thank you! :)

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