Biology AS Edexcel Snab Revision
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lifestyle-health-and-risk as19 主题
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diet-and-health interpreting-data-on-risk-factors
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diet-and-health treatment-of-cvd
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diet-and-health energy-budgets-and-diet
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diet-and-health monosaccharides
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diet-and-health the-glycosidic-bond
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diet-and-health disaccharides
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diet-and-health polysaccharides
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diet-and-health lipids-and-ester-bonds
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diet-and-health reducing-risk-factors-of-cvd
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diet-and-health practical-vitamin-c-content
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the-circulatory-system the-need-for-a-circulatory-system
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the-circulatory-system the-importance-of-water-in-transport
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the-circulatory-system mammalian-heart-structure-and-function
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the-circulatory-system blood-vessels-structure-and-function
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the-circulatory-system cardiac-cycle
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the-circulatory-system investigating-heart-rate
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the-circulatory-system atherosclerosis
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the-circulatory-system blood-clotting
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diet-and-health cardiovascular-disease
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diet-and-health interpreting-data-on-risk-factors
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genes-and-health as28 主题
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gas-exchange-cell-membranes-and-transport properties-of-gas-exchange-surfaces
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gas-exchange-cell-membranes-and-transport ficks-law-of-diffusion
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gas-exchange-cell-membranes-and-transport the-mammalian-lung
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gas-exchange-cell-membranes-and-transport cell-membranes
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gas-exchange-cell-membranes-and-transport practical-investigating-membrane-permeability
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gas-exchange-cell-membranes-and-transport diffusion-and-facilitated-diffusion
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gas-exchange-cell-membranes-and-transport active-transport
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gas-exchange-cell-membranes-and-transport osmosis
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nucleic-acids nucleotides-and-phosphodiester-bonds
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nucleic-acids dna-structure
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nucleic-acids rna-structure
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proteins transcription
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proteins translation
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proteins nature-of-the-genetic-code
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proteins amino-acids-and-peptide-bonds
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proteins levels-of-protein-structure
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proteins globular-proteins-structure-and-function
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proteins fibrous-proteins-structure-and-function
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proteins the-role-of-enzymes
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proteins mode-of-enzyme-action
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proteins enzyme-and-substrate-concentrations
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inheritance dna-replication
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inheritance mutations
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inheritance inheritance-key-terms
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inheritance pedigree-diagrams
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inheritance monohybrid-crosses
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inheritance chi-squared-test
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inheritance genetic-screening
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gas-exchange-cell-membranes-and-transport properties-of-gas-exchange-surfaces
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voice-of-the-genome as19 主题
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cell-structure-and-organisation cell-theory
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cell-structure-and-organisation eukaryotic-cells
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cell-structure-and-organisation prokaryotic-cells
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cell-structure-and-organisation organisation-of-cells
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cell-structure-and-organisation microscopy
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cell-structure-and-organisation magnification-calculations
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cell-structure-and-organisation recognising-organelles
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cell-division the-cell-cycle
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cell-division mitosis
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cell-division practical-identifying-mitosis-in-plant-cells
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reproduction-and-inheritance mammalian-gametes
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reproduction-and-inheritance fertilisation-in-mammals
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reproduction-and-inheritance genes-and-linkage
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reproduction-and-inheritance meiosis-source-of-genetic-variation
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differentiation-and-variation stem-cells
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differentiation-and-variation stem-cells-in-medicine
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differentiation-and-variation cell-differentiation
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differentiation-and-variation epigenetics
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differentiation-and-variation phenotypes-and-variation
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cell-structure-and-organisation cell-theory
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biodiversity-and-natural-resources as19 主题
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biodiversity the-variety-of-life
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biodiversity measuring-biodiversity-within-a-habitat
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biodiversity comparing-biodiversity-between-habitats
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biodiversity ecological-niches-and-adaptations
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biodiversity natural-selection
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biodiversity hardy-weinberg-equation
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biodiversity reproductive-isolation
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biodiversity classification
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biodiversity conservation-of-biodiversity
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resources-from-plants plant-cell-structure
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resources-from-plants plant-stems
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resources-from-plants importance-of-water-and-inorganic-ions-to-plants
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resources-from-plants starch-and-cellulose-structure-and-function
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resources-from-plants plant-fibres
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resources-from-plants practical-identifying-tissue-types-within-stems
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resources-from-plants tensile-strength-plant-fibres
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resources-from-plants development-of-drug-testing
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resources-from-plants antimicrobial-properties-of-plants
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resources-from-plants sustainability-and-plant-materials
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biodiversity the-variety-of-life
proteins amino-acids-and-peptide-bonds
Exam code:8BN0
Amino Acid: Structure
Proteins
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Proteins are polymers (and macromolecules) made of monomers called amino acids
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The sequence, type and number of the amino acids within a protein determines its shape and therefore its function
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Proteins are extremely important in cells because they form all of the following:
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Enzymes
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Cell membrane proteins (eg. carrier)
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Hormones
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Immunoproteins (eg. immunoglobulins)
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Transport proteins (eg. haemoglobin)
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Structural proteins (eg. keratin, collagen)
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Contractile proteins (eg. myosin)
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Amino acids
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Amino acids are the monomers of polypeptides
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There are 20 amino acids found in proteins common to all living organisms
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The general structure of all amino acids is a central carbon atom bonded to:
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An amine (also called amino) group -NH2
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A carboxylic acid group -COOH
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A hydrogen atom
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An R group (which is how each amino acid differs and why amino acid properties differ e.g. whether they are acidic or basic or whether they are polar or non-polar)
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The general structure of an amino acid
The Peptide Bond
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Peptide bonds form between amino acids
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Peptide bonds are covalent bonds and so involve the sharing of electrons
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In order to form a peptide bond :
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A hydroxyl (-OH) is lost from the carboxylic group of one amino acid
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A hydrogen atom is lost from the amine group of another amino acid
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The remaining carbon atom (with the double-bonded oxygen) from the first amino acid bonds to the nitrogen atom of the second amino acid
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This is a condensation reaction so water is released
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Dipeptides are formed by the condensation of two amino acids
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Polypeptides are formed by the condensation of many (3 or more) amino acids
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A protein may have only one polypeptide chain or it may have multiple chains interacting with each other
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During hydrolysis reactions, the addition of water breaks the peptide bonds resulting in polypeptides being broken down to amino acids
Peptide bonds are formed by condensation reactions (releasing a molecule of water) and broken by hydrolysis reactions (adding a molecule of water)
Examiner Tips and Tricks
When asked to identify the location of the peptide bond, look for where nitrogen is bonded to a carbon which has a double bond with an oxygen atom, note the R group is not involved in the formation of a peptide bond.
Structures of specific amino acids are not required.
Responses