AQA AS Biology 3.1.3 Study Guide

Here is a homemade revision guide for 3.1.3 of the AQA Unit 1 AS Biology specification...enjoy!


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  • Created on: 23-10-12 10:53
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3.1.3 Exchange of Materials
This is the structure of the epithelial cell of the small intestine under a microscope.
The fuzzy layer at the top is actually the microvilli.
The nuclei are the ovular shapes two thirds of the way down the shape.
The villi contain epithelial cells which in turn contain microvilli.
Plasma Membrane
Controls the passage of substances into and out of the cell as well as having structural properties and giving
the cell strength.
Increase the surface area of the cell allowing for faster rates of diffusion; they are also folded to allow this.
The nuclear envelope consists of a double membrane.
There are pores in the nuclear envelope.
Contains DNA and chromatin to hold genetic information.
Proteins within the envelope are implicated in gene regulation and chromatin.
Rod-shaped organelles which contain an inner membrane that is folded.
The inside is called the matrix and the folded membranes are called cristae.
Release ATP from aerobic respiration to provide energy for active transport.
An enzyme which is found in the cytoplasm of the cell.
It breaks down lipid walls in cells and aids in digestion.
They digest unwanted materials and foreign bodies in the cell.
They are found of the surface of the rough E.R.
They are involved in the synthesis of proteins from amino acids.
They are small and round structures.
Endoplasmic Reticulum
The smooth endoplasmic reticulum is involved in synthesising and transporting lipids in the cell.
The rough endoplasmic reticulum has ribosomes on its surface and it is involved in transporting proteins as
well as making new membrane.
Golgi apparatus
Flattened sacs on top of one another.
They are involved in packaging and processing proteins ready to be carried around the cell to the membrane.
They pinch off vesicles to carry the proteins.
They have receptors which proteins can bind to.
They control molecular traffic.
Generally transporting the molecules that otherwise wouldn't be secreted by the cell as they would be too
Eukaryotic cells contain a nucleus which is what sets them apart from prokaryotic cells.
In prokaryotic cells, such as bacteria, there is not a nucleus but there are plasmids and DNA is freely floating.
Also there may be flagella, a slime capsule and a cell wall made of meurin.
Electron Microscopes

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The wavelengths of electron beams are much shorter than that of optical beams and so the images are a lot
more resolved.
A beam of electrons is passes to produce an image of the sample.
There are limitations in that the sample must be dead and all water must be removed.
Incredibly small and thin samples have to be prepared.…read more

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The emulsion test for lipids
The way we test for lipids is fairly simple.
We break up the sample and add it to a test tube.
We then add ethanol and shake the contents thoroughly.
We leave the test tube to sit for a few minutes so that any remaining solid falls to the bottom.
We then pour off the supernatant into a separate test tube.
Then we add water.…read more

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Gated channels open and close as they have hormone receptors. They open when a specific hormone is
delivered and this enables them to allow certain substances through, into the cell.
Facilitated diffusion relies on the kinetic energy of the molecules but it still doesn't require ATP from respiration like
active transport does.…read more


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