AQA Biology AS Unit 1

A fair chunk of notes which have been found and collated from various documents, pictures collected from same source. Hope this helps! Best of Luck with the exam

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  • Created on: 16-05-12 19:30
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Biol 1 Revision
BIOLOGICAL MOLECULES
Organic macro molecules all belong to the groups ­ Carbohydrates, Lipids, Proteins and nucleic acids.
These are polymers made up of monomers shown in table.
Two important bonds:
1) Covalent bonds ­ are strong. Can only be made or broken by enzymes
2) Hydrogen bonds ­ are weaker. Can easily be broken without enzymes
Monosaccharide's
Formula (CH2O)n where n can be 3-7
Most important monosaccharide is glucose which is a hexose sugar
Many isomers of glucose with the same formula (galactose and fructose)
Disaccharides
Formed by condensation reaction of monosaccharides with glycosidic bond (polymerisation)
The reverse reaction is breaking the glycosidic bonds by hydrolysis

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Alpha Glucose + Alpha Glucose Maltose
Alpha Glucose + Fructose Sucrose
Alpha Glucose + Galactose Lactose
Starch is a polysaccharide found in plants. It is a chain of many glucose monomers joined
together by glycosidic bonds.
Lipids ­ CHOP
Group of hydrophobic compounds.…read more

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Enzymes (amylase)
Transport (haemoglobin)
Pumps (active pumps ATP)
Antibodies
Amino acids - CHONS
Proteins are made up of amino acids
Amino Group
Carboxylic Acid Group
Hydrogen Group
Variable `R' Group
Polypeptides
Amino acids are joined together by peptide bonds
In a polypeptide chain there is always one free amino group (N-terminus) and one free
carboxylic acid group (C-terminus) at the ends of the chain
Amino acid polymerisation to form polypeptides is part of protein synthesis, it takes place in
the ribosomes
Protein structure
Primary Structure…read more

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Fibrous proteins are long and thin and tend to have structural roles such as collagen. Always
composed of many polypeptide chains.
Protein Denaturing
Proteins held together by hydrogen bonds in the secondary, tertiary and quaternary structures and
therefore we are able to break these bonds easily by using HIGH TEMPERATURES and/or LOW or
HIGH pH's.
Covalent bonds are not denatured under these conditions and therefore the primary structure will be
kept in tact.…read more

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Enzyme concentration ­ increases the rate of reaction proportionally because there are more
enzyme molecules available to catalyse the reaction
4) Substrate concentration ­ as the substrate concentration increases, the rate of enzyme
reaction also increases only up until a certain point where enzyme active sites become
saturated. There will be no difference in adding more
5) Inhibitors ­ Competitive and non-competitive.…read more

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Cytoplasm ­ contains enzymes for respiration and everything else for the cell to function
Nucleus ­ largest organelle, surrounded by nuclear envelope with nuclear pores, nucleolus
Mitochondria ­ site of aerobic respiration; outer membrane cristae (large surface area) space
enclosed is called matrix ­ contains circular DNA
Chloroplast ­ site of photosynthesis (only found in plants and algae) has a double membrane, but
chloroplasts have a third membrane called Thylakoid membrane. Thylakoid disks are stacked into
piles called grana.…read more

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Cell Wall ­ Thick layer outside the cell surface membrane used to give strength and rigidity; freely
permeable to solutes
Different types of Eukaryotic cell
Prokaryotic Cells
Cytoplasm ­ contains all the enzymes needed for metabolic reactions, since there are no organelles
Ribosomes ­ the smaller (70s) type all free in the cytoplasm, never attached to membranes.…read more

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Summary of differences between Eukaryotic and Prokaryotic cells
Cell fractionation
The separation of different parts and organelles of the cell so they can be studied in detail:
1) Cut tissue in ICE-COLD ISOTONIC BUFFER
2) Homogenise the tissue (blend) to break open the cells
3)
4) Filter the homogenate to remove insoluble tissues and cell debris.…read more

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Microscopy
Resolution of an object is the smallest separation at which two separate objects can be distinguished
Magnification of a microscope indicates how much bigger the image is than the original object
Two different types of Microscopy ­
1) Light Microscope
2) Electron Microscope
Light Microscope Electron Microscope
Magnification Calculation:
Magnification = Image length/actual length
When using a Scale Bar:
Actual size = (Image length/bar length) * bar scale
The Cell Membrane
Membranes are very important in the cell, they control what goes in and…read more

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Phospholipids form a thin flexible sheet, whilst the carbohydrates extend out from the proteins. The
structure is called a FLUID MOSAIC STRUCTURE (components can move around).
Phospholipids ­ arranged in a bilayer (double layer) with their polar, hydrophilic phosphate heads
facing out towards water, and their non-polar hydrophobic tails facing each other in the middle of the
bilayer.…read more

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