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Infection and response
Organisation
Cell biology
Biological molecules
Homeostasis and response
Responding to change (a2 only)
Energy transfers (a2 only)
The control of gene expression (a-level only)
Substance exchange
Bioenergetics
Genetic information & variation
Inheritance, variation and evolution
Genetics & ecosystems (a2 only)
Ecology
Cells
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1f industrialisation and the people: britain, c1783-1885
1c the tudors: england, 1485-1603
Britain & the wider world: 1745 -1901
Inter-war germany
World war one
2n revolution and dictatorship: russia, 1917-1953
World war two & the holocaust
1l the quest for political stability: germany, 1871-1991
The cold war
2j america: a nation divided, c1845-1877
Medieval period: 1066 -1509
The fight for female suffrage
2m wars and welfare: britain in transition, 1906-1957
2d religious conflict and the church in england, c1529-c1570
Britain: 1509 -1745
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06/04/2023
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Lipids Lipids are made from carbon, oxygen and hydrogen. They are non-polar so are hydrophobic and do not dissolve in water. They contain oil and fatty acids. Include sterols, phospholipids and triglycerides. Uses Energy source -They release more energy per gram (38kj/g) than carbohydrates (17kj/g). Storage molecule -They provide a lot of energy in a small mass. -e.g. Seeds Insulation -Lipids have slow heat conduction so keep heat in in animals. -e.g. Whale blubber. -They are also good electrical insulators. -e.g. There is a layer of lipids around nerve cells for electrical insulation. Protection -A layer of lipids protect delicate organs. Waterproofing -The hydrophobic properties protect some animals from water. -e.g. in bird feathers. Buoyancy -Lipids are less dense than water so can help some animals to float. Triglycerides Triglycerides are non-polar, hydrophobic molecules The monomers that make up triglycerides is a glycerol and three fatty acids. Glycerol is an alcohol. •Fatty acids -Contain a methyl group at one end of a hydrocarbon chain (R group) and a carboxyl group at the other end. -The short hand formula of a fatty acid is RCOOH. -Fatty acids can vary in hydrocarbon chain length or saturation. -Unsaturated fatty acids can be mono or poly unsaturated. -Unsaturated fatty acids have more than one double bond and can be cis fatty acids or trans fatty acids. -Cis fatty acids have the H atoms on the same side of the...
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double bond. -Trans fatty acids have the H atoms on different sides of the double bond. @ppppph METHYL GROUP CH₂ POLYUNSATURATED (>1 DOUBLE BONDI HYDROCARBON CHAIN (e.g. UNOLEIC ACIDI CARBOXYL GROUP COOH Phospholipids Formed from two fatty acids, a glycerol and a phosphate. As the phosphate is polar, it is soluble in water. The fatty acid tails are non-polar and therefore insoluble in water. Phospholipids are amphipathic (They have hydrophobic and hydrophilic parts. As a result of this, they form monolayers or bilayers when in water). O=P-O ESTER ITT BONDS GLYCEROL НО PHOSPHATE IP HYDROPHRIC POLAR HEAD Cholesterol Amphipathic like phospholipids so have hydrophilic and hydrophobic regions. Cholesterol molecules are synthesised in the liver and transported in the blood. GLYCEROL Cholesterol affects the permeability of cell membranes. It disrupts the close packing of phospholipids making the cell membrane more flexible. This prevents water soluble molecules from diffusing across the cell membrane. Cholesterol molecules are used to produce steroid based hormones such as oestrogen, testosterone, progesterone. CH₂ GLYCEROL HYDROPHILIC REGION (POLARI HYDROPHOBIC FATTY ACID TAILS NON-POLARI + FATTY ACID FATTY ACID CH₂ CH₂ CH₂ FATTY ACID CH₂ The ester bond Triglycerides are formed by esterification. Making an ester bonds forms from the hydroxyl group in glycerol bonding with the carboxyl group of the fatty acid. The H from glycerol combines with the OH from a fatty acid which makes water. This is why esterification is a condensation reaction. Therefore in triglycerides, three water molecules are made. AN ESTER BOND CH CH₂ CH CH₂ HYDROPHOBIC REGION (NON-POLARI CONDENSATION 3H₂0 GLYCEROL FATTY ACID FATTY ACID FATTY ACID TRIGLYCERIDE