Biology AS OCR
-
1-1-practical-skills-written-assessment AS7 主题
-
1-2-practical-skills-endorsement-assessment AS16 主题
-
1-2-1-practical-ethical-use-of-organisms as
-
1-2-2-practical-aseptic-techniques as
-
1-2-3-practical-dissection-of-gas-exchange-surfaces-in-fish-and-insects as
-
1-2-4-drawing-cells-from-blood-smears as
-
1-2-5-practical-investigating-biodiversity-using-sampling as
-
1-2-6-practical-data-loggers-and-computer-modelling as
-
1-2-7-practical-investigating-the-rate-of-diffusion as
-
1-2-8-practical-investigating-water-potential as
-
1-2-9-practical-factors-affecting-membrane-structure-and-permeability as
-
1-2-10-biochemical-tests-reducing-sugars-and-starch as
-
1-2-11-biochemical-tests-lipids as
-
1-2-12-biochemical-tests-proteins as
-
1-2-13-chromatography as
-
1-2-14-serial-dilutions as
-
1-2-15-practical-investigating-the-rate-of-transpiration as
-
1-2-16-practical-using-a-light-microscope as
-
1-2-1-practical-ethical-use-of-organisms as
-
2-1-cell-structure AS9 主题
-
2-1-2-using-a-microscope as
-
2-1-3-drawing-cells as
-
2-1-4-magnification-and-resolution as
-
2-1-5-eukaryotic-cells as
-
2-1-6-eukaryotic-cells-under-the-microscope as
-
2-1-7-organelles-and-the-production-of-proteins as
-
2-1-8-the-cytoskeleton as
-
2-1-9-prokaryotic-and-eukaryotic-cells as
-
2-1-1-studying-cells as
-
2-1-2-using-a-microscope as
-
2-2-biological-molecules AS17 主题
-
2-2-1-properties-of-water as
-
2-2-2-monomers-and-polymers as
-
2-2-3-monosaccharides as
-
2-2-4-the-glycosidic-bond as
-
2-2-5-polysaccharides as
-
2-2-6-biochemical-tests-reducing-sugars-and-starch as
-
2-2-7-lipids-and-ester-bonds as
-
2-2-8-lipids-structure-and-function as
-
2-2-9-biochemical-tests-lipids as
-
2-2-10-amino-acids-and-peptide-bonds as
-
2-2-11-protein-structure as
-
2-2-12-globular-proteins as
-
2-2-13-fibrous-proteins as
-
2-2-14-inorganic-ions as
-
2-2-15-biochemical-tests-proteins as
-
2-2-16-finding-the-concentration-of-a-substance as
-
2-2-17-chromatography as
-
2-2-1-properties-of-water as
-
2-3-nucleotides-and-nucleic-acids AS8 主题
-
2-4-enzymes AS9 主题
-
2-4-1-the-role-of-enzymes as
-
2-4-2-enzyme-action as
-
2-4-3-enzyme-activity-ph as
-
2-4-4-enzyme-activity-temperature as
-
2-4-5-enzyme-activity-enzyme-concentration as
-
2-4-6-enzyme-activity-substrate-concentration as
-
2-4-7-enzyme-activity-enzyme-inhibitors as
-
2-4-8-coenzymes-cofactors-and-prosthetic-groups as
-
2-4-9-practical-measuring-enzyme-activity as
-
2-4-1-the-role-of-enzymes as
-
2-5-biological-membranes AS9 主题
-
2-5-1-the-cell-surface-membrane as
-
2-5-2-membrane-structure-and-permeability as
-
2-5-3-diffusion-and-facilitated-diffusion as
-
2-5-4-practical-investigating-the-rate-of-diffusion as
-
2-5-5-active-transport as
-
2-5-6-endocytosis-and-exocytosis as
-
2-5-7-osmosis as
-
2-5-8-osmosis-in-animal-and-plant-cells as
-
2-5-9-practical-investigating-water-potential as
-
2-5-1-the-cell-surface-membrane as
-
2-6-cell-division-cell-diversity-and-cellular-organisation AS11 主题
-
2-6-1-the-cell-cycle as
-
2-6-2-the-stages-of-mitosis as
-
2-6-3-identifying-mitosis-in-plant-cells as
-
2-6-4-the-significance-of-mitosis as
-
2-6-5-the-stages-of-meiosis as
-
2-6-6-the-significance-of-meiosis as
-
2-6-7-specialised-cells as
-
2-6-8-the-organisation-of-cells as
-
2-6-9-stem-cells as
-
2-6-10-stem-cells-in-animals-and-plants as
-
2-6-11-the-use-of-stem-cells as
-
2-6-1-the-cell-cycle as
-
3-1-exchange-surfaces AS7 主题
-
3-2-transport-in-animals AS12 主题
-
3-2-1-the-need-for-transport-systems-in-animals as
-
3-2-2-circulatory-systems as
-
3-2-3-blood-vessels as
-
3-2-4-tissue-fluid as
-
3-2-5-the-mammalian-heart as
-
3-2-6-practical-mammalian-heart-dissection as
-
3-2-7-the-cardiac-cycle as
-
3-2-8-cardiac-output as
-
3-2-9-heart-action-initiation-and-control as
-
3-2-10-electrocardiograms-ecgs as
-
3-2-11-the-role-of-haemoglobin as
-
3-2-12-adult-and-fetal-haemoglobin as
-
3-2-1-the-need-for-transport-systems-in-animals as
-
3-3-transport-in-plants AS11 主题
-
3-3-1-the-need-for-transport-systems-in-plants as
-
3-3-2-the-xylem-and-phloem as
-
3-3-3-the-xylem as
-
3-3-4-the-phloem as
-
3-3-5-transverse-sections-stems-roots-and-leaves as
-
3-3-6-the-process-of-transpiration as
-
3-3-7-transpiration-in-plants as
-
3-3-8-practical-investigating-the-rate-of-transpiration as
-
3-3-9-translocation as
-
3-3-10-the-mass-flow-hypothesis as
-
3-3-11-the-adaptations-of-xerophytic-and-hydrophytic-plants as
-
3-3-1-the-need-for-transport-systems-in-plants as
-
4-1-communicable-diseases-disease-prevention-and-the-immune-system AS16 主题
-
4-1-1-common-pathogens-and-communicable-diseases as
-
4-1-2-transmission-of-communicable-pathogens as
-
4-1-3-plant-defences-against-pathogens as
-
4-1-4-non-specific-immune-responses as
-
4-1-5-phagocytes as
-
4-1-6-blood-cells as
-
4-1-7-the-t-lymphocyte-response as
-
4-1-8-the-b-lymphocyte-response as
-
4-1-9-primary-and-secondary-immune-responses as
-
4-1-10-antibodies as
-
4-1-11-opsonins-agglutinins-and-anti-toxins as
-
4-1-12-types-of-immunity as
-
4-1-13-autoimmune-diseases as
-
4-1-14-principles-of-vaccination as
-
4-1-15-sources-of-medicine as
-
4-1-16-antibiotics as
-
4-1-1-common-pathogens-and-communicable-diseases as
-
4-2-biodiversity AS10 主题
-
4-2-1-biodiversity as
-
4-2-2-sampling-to-determine-biodiversity as
-
4-2-3-practical-investigating-biodiversity-using-sampling as
-
4-2-4-measuring-species-richness-and-species-evenness as
-
4-2-5-simpsons-index as
-
4-2-6-genetic-diversity as
-
4-2-7-factors-affecting-biodiversity as
-
4-2-8-reasons-for-maintaining-biodiversity as
-
4-2-9-methods-of-maintaining-biodiversity as
-
4-2-10-conservation-agreements as
-
4-2-1-biodiversity as
-
4-3-classification-and-evolution AS15 主题
-
4-3-1-classification-of-species as
-
4-3-2-binomial-system as
-
4-3-3-classification-of-the-three-domains as
-
4-3-4-classification-of-the-five-kingdoms as
-
4-3-5-classification-and-phylogeny as
-
4-3-6-evidence-of-evolution as
-
4-3-7-types-of-variation as
-
4-3-8-standard-deviation as
-
4-3-9-variation-t-test-method as
-
4-3-10-variation-t-test-worked-example as
-
4-3-11-spearmans-rank-correlation as
-
4-3-12-adaptation as
-
4-3-13-natural-selection as
-
4-3-14-evolution-of-resistance as
-
4-3-15-consequences-of-resistance as
-
4-3-1-classification-of-species as
2-1-5-eukaryotic-cells as
Exam code:H020
Eukaryotic Cell Structure
Cell surface membrane
The structure of the cell surface membrane – although the structure looks static the phospholipids and proteins forming the bilayer are constantly in motion
-
All cells are surrounded by a cell surface membrane which controls the exchange of materials between the internal cell environment and the external environment
-
The membrane is described as being ‘partially permeable’
-
-
The cell membrane is formed from a phospholipid bilayer of phospholipids spanning a diameter of around 10 nm
Cell wall
The cell wall is freely permeable to most substances (unlike the plasma membrane)
-
Found in plant cells but not in animal cells
-
Cell walls are formed outside of the cell membrane and offer structural support to cell
-
Structural support is provided by the polysaccharide cellulose in plants, and peptidoglycan in most bacterial cells
-
Narrow threads of cytoplasm (surrounded by a cell membrane) called plasmodesmata connect the cytoplasm of neighbouring plant cells
Nucleus
The nucleus of a cell contains chromatin (a complex of DNA and histone proteins) which is the genetic material of the cell
-
Present in all eukaryotic cells (except red blood cells), the nucleus is relatively large and separated from the cytoplasm by a double membrane (the nuclear envelope) which has many pores
-
Nuclear pores are important channels for allowing mRNA and ribosomes to travel out of the nucleus, as well as allowing enzymes (eg. DNA polymerases) and signalling molecules to travel in
-
The nucleus contains chromatin (the material from which chromosomes are made)
-
Chromosomes are made of sections of linear DNA tightly wound around proteins called histones
-
-
Usually, at least one or more darkly stained regions can be observed – these regions are individually termed ‘nucleolus’ (plural: nucleoli) and are the sites of ribosome production
Mitochondria
A single mitochondrion is shown – the inner membrane has protein complexes vital for the later stages of aerobic respiration embedded within it
-
The site of aerobic respiration within all eukaryotic cells, mitochondria are just visible with a light microscope
-
Surrounded by double-membrane with the inner membrane folded to form cristae
-
The matrix formed by the cristae contains enzymes needed for aerobic respiration, producing ATP
-
Small circular pieces of DNA (mitochondrial DNA) and ribosomes are also found in the matrix (needed for replication)
Chloroplasts
Chloroplasts are found in the green parts of a plant – the green colour a result of the photosynthetic pigment chlorophyll
-
Found in plant cells
-
Larger than mitochondria, also surrounded by a double-membrane
-
Membrane-bound compartments called thylakoids containing chlorophyll stack to form structures called grana
-
Grana are joined together by lamellae (thin and flat thylakoid membranes)
-
Chloroplasts are the site of photosynthesis:
-
The light-dependent stage takes place in the thylakoids
-
The light-independent stage (Calvin Cycle) takes place in the stroma
-
-
Also contain small circular pieces of DNA and ribosomes used to synthesise proteins needed in chloroplast replication and photosynthesis
Ribosomes
Ribosomes are formed in the nucleolus and are composed of almost equal amounts of RNA and protein
-
Found in all cells
-
Found freely in the cytoplasm of all cells or as part of the rough endoplasmic reticulum in eukaryotic cells
-
Each ribosome is a complex of ribosomal RNA (rRNA) and proteins
-
80S ribosomes (composed of 60S and 40S subunits) are found in eukaryotic cells
-
70S ribosomes (composed of 50S and 30S subunits) in prokaryotes, mitochondria and chloroplasts
-
Site of translation (protein synthesis)
Endoplasmic reticulum
The RER and ER are visible under the electron microscope – the presence or absence of ribosomes helps to distinguish between them
Rough Endoplasmic Reticulum (RER)
-
Found in plant and animal cells
-
Surface covered in ribosomes
-
Formed from continuous folds of membrane continuous with the nuclear envelope
-
Pr
Responses