Biology AS CIE
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1-cell-structure10 主题
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1-2-cells-as-the-basic-units-of-living-organisms AS viruses
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1-2-cells-as-the-basic-units-of-living-organisms AS prokaryotic-v-eukaryotic-cells
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1-2-cells-as-the-basic-units-of-living-organisms AS the-vital-role-of-atp
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1-2-cells-as-the-basic-units-of-living-organisms AS animal-and-plant-cells
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1-2-cells-as-the-basic-units-of-living-organisms AS eukaryotic-cell-structures-and-functions
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1-1-the-microscope-in-cell-studies AS calculating-actual-size
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1-1-the-microscope-in-cell-studies AS resolution-and-magnification
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1-1-the-microscope-in-cell-studies AS eyepiece-graticules-and-stage-micrometers
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1-1-the-microscope-in-cell-studies AS magnification-calculations
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1-1-the-microscope-in-cell-studies AS the-microscope-in-cell-studies
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1-2-cells-as-the-basic-units-of-living-organisms AS viruses
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2-biological-molecules19 主题
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2-4-water AS water-and-the-hydrogen-bond
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2-4-water AS the-role-of-water-in-living-organisms
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2-3-proteins AS collagen
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2-3-proteins AS haemoglobin
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2-3-proteins AS globular-and-fibrous-proteins
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2-3-proteins AS protein-shape
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2-3-proteins AS the-four-levels-of-protein-structure
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2-3-proteins AS amino-acids-and-the-peptide-bond
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2-2-carbohydrates-and-lipids AS phospholipids
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2-2-carbohydrates-and-lipids AS triglycerides
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2-2-carbohydrates-and-lipids AS cellulose
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2-2-carbohydrates-and-lipids AS starch-and-glycogen
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2-2-carbohydrates-and-lipids AS the-glycosidic-bond
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2-2-carbohydrates-and-lipids AS reducing-and-non-reducing-sugars
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2-2-carbohydrates-and-lipids AS covalent-bonds-in-polymers
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2-2-carbohydrates-and-lipids AS biological-molecules-key-terms
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2-1-testing-for-biological-molecules AS testing-for-non-reducing-sugars
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2-1-testing-for-biological-molecules AS the-benedicts-test
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2-1-testing-for-biological-molecules AS biological-molecule-tests
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2-4-water AS water-and-the-hydrogen-bond
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3-enzymes13 主题
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3-2-factors-that-affect-enzyme-action AS enzyme-activity-immobilised-v-free
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3-2-factors-that-affect-enzyme-action AS enzyme-inhibitors
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3-2-factors-that-affect-enzyme-action AS vmax-and-the-michaelis-menten-constant
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3-2-factors-that-affect-enzyme-action AS rate-inhibitor-concentration
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3-2-factors-that-affect-enzyme-action AS rate-substrate-concentration
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3-2-factors-that-affect-enzyme-action AS rate-enzyme-concentration
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3-2-factors-that-affect-enzyme-action AS rate-ph
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3-2-factors-that-affect-enzyme-action AS rate-temperature
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3-1-mode-of-action-of-enzymes AS colorimetry
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3-1-mode-of-action-of-enzymes AS measuring-enzyme-activity
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3-1-mode-of-action-of-enzymes AS how-enzymes-work
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3-1-mode-of-action-of-enzymes AS enzyme-action
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3-1-mode-of-action-of-enzymes AS enzymes
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3-2-factors-that-affect-enzyme-action AS enzyme-activity-immobilised-v-free
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4-cell-membranes-and-transport16 主题
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4-2-movement-into-and-out-of-cells AS comparing-osmosis-in-plants-and-animals
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4-2-movement-into-and-out-of-cells AS osmosis-in-animals
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4-2-movement-into-and-out-of-cells AS osmosis-in-plant-cells
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4-2-movement-into-and-out-of-cells AS estimating-water-potential-in-plants
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4-2-movement-into-and-out-of-cells AS investigating-surface-area
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4-2-movement-into-and-out-of-cells AS surface-area-to-volume-ratios
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4-2-movement-into-and-out-of-cells AS investigating-diffusion
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4-2-movement-into-and-out-of-cells AS investigating-transport-processes-in-plants
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4-2-movement-into-and-out-of-cells AS endocytosis-and-exocytosis
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4-2-movement-into-and-out-of-cells AS active-transport
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4-2-movement-into-and-out-of-cells AS osmosis
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4-2-movement-into-and-out-of-cells AS diffusion
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4-1-fluid-mosaic-membranes AS cell-signalling
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4-1-fluid-mosaic-membranes AS the-cell-surface-membrane
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4-1-fluid-mosaic-membranes AS components-of-cell-surface-membranes
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4-1-fluid-mosaic-membranes AS the-fluid-mosaic-model
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4-2-movement-into-and-out-of-cells AS comparing-osmosis-in-plants-and-animals
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5-the-mitotic-cell-cycle8 主题
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5-2-chromosome-behaviour-in-mitosis AS observing-mitosis
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5-2-chromosome-behaviour-in-mitosis AS the-stages-of-mitosis
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5-1-replication-and-division-of-nuclei-and-cells AS how-tumours-form
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5-1-replication-and-division-of-nuclei-and-cells AS the-role-of-stem-cells
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5-1-replication-and-division-of-nuclei-and-cells AS the-role-of-telomeres-
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5-1-replication-and-division-of-nuclei-and-cells AS the-cell-cycle
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5-1-replication-and-division-of-nuclei-and-cells AS mitosis
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5-1-replication-and-division-of-nuclei-and-cells AS chromosome-structure
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5-2-chromosome-behaviour-in-mitosis AS observing-mitosis
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6-nucleic-acids-and-protein-synthesis9 主题
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6-2-protein-synthesis AS gene-mutations
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6-2-protein-synthesis AS transcription
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6-2-protein-synthesis AS constructing-polypeptides
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6-2-protein-synthesis AS the-universal-genetic-code
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6-2-protein-synthesis AS from-gene-to-polypeptide
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6-1-structure-of-nucleic-acids-and-replication-of-dna AS the-structure-of-rna
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6-1-structure-of-nucleic-acids-and-replication-of-dna AS semi-conservative-dna-replication
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6-1-structure-of-nucleic-acids-and-replication-of-dna AS the-structure-of-dna
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6-1-structure-of-nucleic-acids-and-replication-of-dna AS nucleotides
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6-2-protein-synthesis AS gene-mutations
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7-transport-in-plants11 主题
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7-2-transport-mechanisms AS phloem-mass-flow
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7-2-transport-mechanisms AS the-sucrose-loading-mechanism
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7-2-transport-mechanisms AS movement-in-the-phloem
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7-2-transport-mechanisms AS xerophytic-plant-leaf-adaptations
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7-2-transport-mechanisms AS water-and-the-transpiration-pull
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7-2-transport-mechanisms AS transpiration-in-plants
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7-2-transport-mechanisms AS water-and-mineral-ion-transport-in-plants
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7-1-structure-of-transport-tissues AS phloem-sieve-tube-elements
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7-1-structure-of-transport-tissues AS xylem-vessels-elements
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7-1-structure-of-transport-tissues AS xylem-and-phloem-distribution
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7-1-structure-of-transport-tissues AS plant-transverse-sections
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7-2-transport-mechanisms AS phloem-mass-flow
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8-transport-in-mammals16 主题
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8-3-the-heart AS heart-action
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8-3-the-heart AS the-cardiac-cycle
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8-3-the-heart AS the-walls-of-the-heart
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8-3-the-heart AS structure-of-the-heart
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8-2-transport-of-oxygen-and-carbon-dioxide AS the-bohr-shift
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8-2-transport-of-oxygen-and-carbon-dioxide AS the-oxygen-dissociation-curve
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8-2-transport-of-oxygen-and-carbon-dioxide AS plasma-and-carbon-dioxide
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8-2-transport-of-oxygen-and-carbon-dioxide AS the-chloride-shift
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8-2-transport-of-oxygen-and-carbon-dioxide AS red-blood-cells-haemoglobin-and-oxygen
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8-1-the-circulatory-system AS blood-tissue-fluid-and-lymph
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8-1-the-circulatory-system AS the-role-of-water-in-circulation
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8-1-the-circulatory-system AS cells-of-the-blood
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8-1-the-circulatory-system AS blood-vessels-structures-and-functions
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8-1-the-circulatory-system AS observing-and-drawing-blood-vessels
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8-1-the-circulatory-system AS the-main-blood-vessels
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8-1-the-circulatory-system AS circulatory-systems
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8-3-the-heart AS heart-action
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9-gas-exchange6 主题
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9-1-the-gas-exchange-system AS gas-exchange-processes
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9-1-the-gas-exchange-system AS structures-and-functions-of-the-gas-exchange-system
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9-1-the-gas-exchange-system AS recognising-structures
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9-1-the-gas-exchange-system AS recognising-tissues
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9-1-the-gas-exchange-system AS distribution-of-tissues
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9-1-the-gas-exchange-system AS the-human-gas-exchange-system
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9-1-the-gas-exchange-system AS gas-exchange-processes
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10-infectious-diseases6 主题
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11-immunity10 主题
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11-2-antibodies-and-vaccination AS vaccination-to-control-disease
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11-2-antibodies-and-vaccination AS how-vaccines-work
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11-2-antibodies-and-vaccination AS types-of-immunity
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11-2-antibodies-and-vaccination AS uses-of-monoclonal-antibodies
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11-2-antibodies-and-vaccination AS making-monoclonal-antibodies
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11-2-antibodies-and-vaccination AS antibodies
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11-1-the-immune-system AS memory-cells-and-immunity
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11-1-the-immune-system AS primary-immune-response
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11-1-the-immune-system AS antigens
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11-1-the-immune-system AS phagocytes
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11-2-antibodies-and-vaccination AS vaccination-to-control-disease
2-3-proteins AS the-four-levels-of-protein-structure
Exam code:9700
Proteins: structures
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There are four levels of structure in proteins, three are related to a single polypeptide chain and the fourth level relates to a protein that has two or more polypeptide chains
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Polypeptide or protein molecules can have anywhere from 3 amino acids (Glutathione) to more than 34,000 amino acids (Titin) bonded together in chains
Primary structure
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The sequence of amino acids bonded by covalent peptide bonds is the primary structure of a protein
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DNA of a cell determines the primary structure of a protein by instructing the cell to add certain amino acids in specific quantities in a certain sequence
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This affects the shape and therefore the function of the protein
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The primary structure is specific for each protein (one alteration in the sequence of amino acids can affect the function of the whole protein)
Secondary structure
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The secondary structure of a protein occurs when the weak negatively charged nitrogen and oxygen atoms interact with the weak positively charged hydrogen atoms to form hydrogen bonds
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There are two shapes that can form within proteins due to the hydrogen bonds:
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α-helix
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β-pleated sheet
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The α-helix shape occurs when the hydrogen bonds form between every fourth peptide bond (between the oxygen of the carboxyl group and the hydrogen of the amine group)
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The β-pleated sheet shape forms when the protein folds so that two parts of the polypeptide chain are parallel to each other enabling hydrogen bonds to form between parallel peptide bonds
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Most fibrous proteins have secondary structures (e.g. collagen and keratin)
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The secondary structure only relates to hydrogen bonds forming between the amino group and the carboxyl group (the ‘protein backbone’)
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The hydrogen bonds can be broken by high temperatures and pH changes
Tertiary structure
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Further conformational change of the secondary structure leads to additional bonds forming between the R groups (side chains)
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The additional bonds are:
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Hydrogen (these are between R groups)
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Disulfide(only occurs between cysteine amino acids, sometimes referred to as a disulfide bridge)
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Ionic (occurs between charged R groups)
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Weak hydrophobic interactions (between non-polar R groups)
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This structure is common in globular proteins such as antibodies
Quaternary structure
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Occurs in proteins that have more than one polypeptide chain working together as a functional macromolecule, for example, haemoglobin
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Each polypeptide chain in the quaternary structure is referred to as a subunit of the protein
|
Bonds |
Level |
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|---|---|---|---|
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Primary |
Secondary |
Tertiary |
|
|
Peptide |
✓ |
✓ |
✓ |
|
Hydrogen |
X |
✓ (only between the amine and carboxyl groups) |
✓ (only between the R, amine and carboxyl groups) |
|
Disulfide |
X |
X |
✓ |
|
Ionic |
X |
X |
✓ |
|
Hydrophobic interactions |
X |
X |
✓ |
Examiner Tips and Tricks
Familiarise yourself with the difference between the four structural levels found in proteins, noting which bonds are found at which level.
Remember that in secondary structures the hydrogen bonds form between the amino and carboxyl groups, whereas in tertiary structures the hydrogen bonds form between the R groups.
Responses