Complete B7 Revision Notes

Here's my OCR 21st century science B7 revision notes for the exam on Wednesday 15th 2011. Hope they're useful!

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  • Created by: Bill Dunn
  • Created on: 12-06-11 11:44
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Heterotrophs that feed on waste are called decomposers.
As there is less food and energy at each feeding level, there is a limit to the length of food
Soil contains biomass, inorganic particles (sand, silt, clay), air and water.
Energy from light is used to rearrange the atoms of CO and HO.
Plants use glucose to: Make chemicals for growth ­ cellulose, protein,
Store energy as starch.
Release energy in respiration.
Starch is ideal as an energy store. As it is insoluble in water, it has no effect on the osmotic
balance of cells (unlike glucose).
Energy from respiration is used to synthesise: Starch and cellulose from glucose.
Amino acids from glucose and nitrates.
Plant roots absorb nitrates by active transport (requires energy).
Organisms that benefit each other have a symbiotic relationship.
An organism that benefits from another organism (without harming it) is called
An organism that benefits from another organism (while harming it) is called parasitism.
Parasites have to be adapted for finding a host and living on/it it.
Sickle cell anaemia is caused by a faulty recessive allele that codes for haemoglobin.
Some red blood cells go sickle shaped which causes:
Pain when the cells block blood vessels.
Anaemia as damaged cells can't be replaced fast enough.
Tiredness due to a shortage of oxygen.

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Bacteria can be grown on a large scale using fermenters.
Products made this way are: Antibiotics
Single-cell proteins
Enzymes for food manufacture.
Genetically modifying an organism means altering its characteristics by transferring genes
from another organism into its DNA. A vector is used to transfer the genes.
Genetic testing can be used to detect faulty alleles in adults, foetuses and IVF embryos.
A gene probe is used. This is a single strand of DNA with bases that will pair with the faulty
1.…read more

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Blood contains: Plasma contains water, glucose, hormones and waste
RBCs contain haemoglobin to carry oxygen.
WBCs some make antibodies, some engulf microorganisms.
Platelets fragments of cells that help blood clot at a wound.
Markers called antigens are on the surface of cells. Antibodies recognise foreign antigens
and destroy the cells.
If a blood recipient has antibodies to the donor's red blood cells: The RBCs clump and
block blood vessels.
People with type AB blood are universal recipients.…read more

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A plan may be changed because it isn't working, or its causing side effects.…read more


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