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
3-1-3-the-mammalian-gas-exchange-system as
Exam code:H020
The Mammalian Gas Exchange System
-
Gas exchange takes place in the human thorax. This is a collection of organs and tissues in the chest cavity
Tissues of the gas exchange system
-
There are a number of different tissue types present in the mammalian gas exchange system
-
Each tissue is structurally adapted to perform a very specific purpose
-
Ciliated epithelial cells, goblet cells and mucous glands play vital roles in maintaining the health of the gas exchange system
-
Cartilage, smooth muscle, elastic fibres and squamous epithelial tissue all play important structural roles in maintaining the gas exchange system
Cartilage
-
Cartilage is a strong and flexible tissue found in various places around the body
-
One place is in rings along the trachea, called Tracheal rings
-
These rings help to support the trachea and ensure it stays open while allowing it to move and flex while we breathe
-
Cartilage micrograph
Ciliated epithelium
-
Ciliated epithelium is a specialised tissue found along the trachea down to the bronchi
-
Each cell has small projections of cilia which sweep mucus, dust and bacteria upwards and away from the lungs and the epithelium itself
Ciliated epithelium showing microvilli, basement membrane, goblet cell and nucleus
Ciliated epithelium – electron micrograph
Goblet cells
-
Goblet cells can be found scattered throughout the ciliated epithelium in the trachea
-
They are mucus-producing cells that secrete viscous mucus which traps dust, bacteria and other microorganisms and prevents them from reaching the lungs
-
The mucus is then swept along by the cilia of the ciliated epithelium upwards and is swallowed
-
The mucus and any microorganisms will then be destroyed by the acid in the stomach
Goblet cell – light micrograph
Squamous epithelium
-
The alveoli have a lining of thin and squamous epithelium, that allows for gas exchange
-
The squamous epithelium forms the structure of the alveolar wall and so is very thin and permeable for the easy diffusion of gases
-
Squamous epithelium – light micrograph
Smooth muscle
-
Smooth muscle can be found throughout the walls of the bronchi and bronchioles
-
It helps to regulate the flow of air into the lungs by dilating when more air is needed and constricting when less air is needed
-
Smooth muscle – light micrograph
Elastic fibres
-
Elastic fibres are present in all lung tissues. They are very important as they enable the lung to stretch and recoil. This ability to recoil is what makes expiration a passive process
Capillaries
-
Each alveolus is surrounded by an extensive network of capillaries
-
Carbon dioxide diffuses out of the capillaries and into the alveoli to be exhaled, while oxygen diffuses the other way from alveoli and into the capillaries to be carried around the body
-
-
These capillaries have a diameter of around 3-4µm, which is only wide enough for one red blood cell to travel through at any one time
-
This ensures that there is sufficient time and opportunity for gas exchange to occur
-
Cross-section of capillaries – light micrograph
Structures & Functions in the Gas Exchange System Table
Responses