These are the new specification notes for the Biology AS Unit 2, I achieved full UMS in the exam and an A overall. They are very condensed but still have all the information required for the unit making them perfect for revision purposes.
As a student doing the new revised spec - especially on CCE...
Transport and Exchange mechanisms in plants and
animals
Root Hair cell
Red blood cell
Animals need oxygen + glucose + water Surface area- The amount of cells in direct contact with the surrounding environment
Plants need oxygen esp. at night + carbon -Affects rate of exchange, supply of metabolites and removal of wastes
dioxide during the day + inorganic ions + water
- The amount of 3D space taken up by metabolically active cells
Exchange of substances only occur at a moist, permeable surface -Affects need for metabolites
The relationship between these factors is called the SA:V ratio
Thin walls (short diffusion distance)
tubular extension increases SA
This means there is a need for specialised absorptive surfaces SMALL organisms have a LARGE SAV ratio Aids in uptake of oxygen, water and
Usually organisms need these surfaces if they are; LARGE organisms have a SMALL SAV ratio ions Biconcave disc shape increases SAV ratio for effective oxygen
• Terrestrial (Lives on land, impermeable membrane) uptake
• Large with small SAV ratio Thinness of cell allows oxygen to diffuse in and out easily
• Have a high metabolic rate
Exchange surfaces must have an increased surface area (can be achieved by flattening or folding of
membrane)
Thin separating surface
Maintain a large concentration gradient • Large SA as they are small and occur in
Exchange surfaces clusters In multicellular organisms there is a large demand for oxygen and other substances
• Moist allows gas exchange- stays which need to be delivered rapidly to all cells. Waste+ water also need transported
moist due to position in body, less throughout organism.
Leaf diagram water lost Whether an organism needs this depends on two factors;
• The leaf is a flattened structure (broad and thin) • Thin walls (simple squamous SAV ratio + metabolic rate
which ensures short diffusion distance while epithelium) - short diffusion distance
increasing surface area • Good blood supply maintains
• Wide expanse of palisade mesophyll efficient at concentration gradient as flow of Some examples of mass flow systems include;
trapping light blood + ventilation constantly brings Movement in xylem (generated by negative pressure by transpiration) resulting
• Loosely packed spongy mesophyll provides an air CO2 and O2 to exchange surface in transport of water and ions from roots to leaves
space system provides large amounts of SA for gas • Surfactant secreting cells- surfactant Translocation in phloem (By energy in plant) which results in two way flow of
exchange + moist for gas exchange reduces surface tension, preventing organic solutes in flower plants
• Guard cells allows CO2 and O2 to diffuse in and out alveolar collapse Breathing in mammals, pressure decreased/increases in thorax to draw in air
• Some oxygen produced is used in respiration • Goblet cells secrete mucous which and force it out
Capillaries- traps dirt+dust+microbes Circulation in mammals, high pressure generated by muscular heart results in
Small, allowing extensive network throughout body • Cilia cells have hairs which whisk dirt circulation of blood throughout body.
increasing SA particles out
Thin walls (Simple squamous endothelium)
Gas Exchange
Inhalation
Compensation point Respiration in plants Pleural fluid Exhalation
Ficks law = SA x Conc. difference Plants lack specialised respiratory Muscles of diaphragm and
Diffusion distance Rate of photosynthesis = Rate of respiration surfaces but can be large Muscle of diaphragm
external intercostal muscles
There no net exchange of gases at this point -Lack tissues with high energy demand contracts, flattening it
relax
and as such low respiration rate External intercostal muscles
Ficks law states that the rate of gas exchange Diaphragm returns to dome
contract and ribs move up
is improved by a; shape, ribs move down and in
They require a specialised gas exchange and out
Large SA, big concentration difference and Volume of thorax decreases,
surface as -Volume of thorax increases,
short diffusion distance increasing pressure around
-A high rate of photosynthesis can be decreasing pressure around
lungs
generated lungs
The higher the metabolic rate the greater the +Recoil of elastic lungs
-Concentration of carbon dioxide in air Pressure in alveoli decreases
need for these principles to be met Pressure in alveoli increases
is low Air enters lungs
Air exits lungs
Smoking
CO reduces ability of RBC to carry oxygen Emphysema Chronic bronchitis
Smoking causes cancer, emphysema and bronchitis
Nicotine is an addictive substance Smoke causes inflammatory response in alveoli and results of breakdown of Tar causes inflammatory response causing bronchioles to narrow and excessive amount of mucus
Tar paralyses cilia and causes an inflammatory Lung Cancer walls. Reduces area available for gas exchange, as well as loss of elastic fibresare produced. Tar paralyses cilia causing pathogens and mucus to build up. This restricts air flow.
response Tar contains carcinogens which damage DNA in epithelial cells, making breathing out more difficult. Can take a long time to develop. Symptoms include;
Smoke affects elasticity reduction, air not forced causing cancer Accompanied by a chronic cough, reflex action trying to remove dead cells and Shortness of breath, Persistent cough, Frequent respiratory infections (due to inability to clear
out as effectively as alveoli unable to recoil The cells divide uncontrollably creating a tumour, this can block mucus - unable to as cilia are dead/inactive mucus and bacteria), Wheezing
airways or damage large sections of the lung. This tumour may
Blue skin due to insufficient O2
spread and invade other tissues.
Biology AS2 Page 1
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