A Level Biology Revision Notes

Comprehensive A Level Biology revision notes providing information and assistance for all UK examination boards (AQA, OCR, Edexcel) as well as international curriculum (CIE).

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Biological Compounds

Introduction Carbohydrates are made up of monosaccharides – which are with relatively small molecules used as building blocks. As well as monosaccarides other monomers like amino acids and nucleotides are also used as building-blocks for the larger polymer structures. Polymers are the larger structures, built from monomers, and include carbohydrates, proteins and nucleic acids. The …

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Meiosis

Summary Meiosis is a specialised type of cell division that produces gametes, which require a haploid genome in order to participate in sexual reproduction Meiosis is fairly similar to mitosis, but the differences can be remembered with the pneumonic DISCOPUG (division, independent, synapsis, crossover, outcome, ploidy, use, genetics Meiosis can be divided into two stages, …

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Oxidative Phosphorylation

Summary Oxidative phosphorylation is comprised of the electron transport chain and chemiosmosis. It is the most efficient producer of ATP in the process of aerobic respiration Electrons carried from previous steps of respiration enter the electron transport chain, and are sequentially passed through membrane bound proteins The final member of the chain is oxygen, which …

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Variation

Summary Variation describes diversity in the genetic make-up of a species Variation arises from mutations Variations usually have a small effect on phenotype (continuous variation), but there are examples where a variant has a large effect on a phenotype, and generates distinct categories (discontinuous variation) Variation in a population can be influenced by mutation rate, …

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Lipids Structure & Functions

Summary Lipids are most often triglycerides, which are made up of 3 fatty acids and glycerol Triglycerides are generated by a condensation reaction, and the bond between glycerol and the fatty acid is called an ester bond Fatty acids can be saturated (single bonds between all carbons) or unsaturated, at least one double bond between …

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Water

Summary Water is made up of two hydrogens covalently bonded to oxygen. Water molecules are polar, and are attracted to one another by hydrogen bonding Water is an excellent solvent, breaking up compounds so that the components can take part in biological processes It is also important in regulating temperature fluctuations in living organisms Water …

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