Biology cie 9700 A level notes on topic 14 ( topic 3 from A level section)
summary made out of notes from both CIE textbook, classnotes and past papers. covers all the syllabus checklist for 2018.
Achieved 91% on my biology A level this june. Prepared for the exam using these notes and past paper...
Needs complex system t maintain constant internal conditions near constant.
(maintained within narrow limits).
The kidney removes any wastes from the blood and are the effectors for
controlling the water potential of blood.
Homeostasis: Homeostasis is the maintenance of an organisms internal
environment within set limits.
This requires information about conditions inside the body and surroundings,
detected by sensory cells.
Physiological factors controlled in mammals:
- core body temperature:
Metabolic wastes (co2 and urea)
Blood pH
Blood glucose conc.
Water potential of the blood
Conc. Of respiratory gases in the blood.
Cells in multicellular animals are surrounded by tissue fluid, its features influence
how cell functions:
Temperature: low temps slow down metabolic reactions. High temp. denatures
proteins(enzymes) proteins denature.
Water potential: decreases, water moves out of cell by osmosis metabolic reaction
slow down or stop depriving cell from energy source. Increases, water may enter
cell and burst it.
Conc. of glucose; fuel for respiration, too little, respiration slows down no energy
source , too much glucose may cause h20 to move out of cell, disturbing
metabolism
Enzyme activity: enzymes best operate over specific range of conditions . by
maintaining ph + temp in the body , all enzyme –linked reactions proceed
efficiently.
Cell size: changes in the water potential of the blood will affect the amount of
water in tissue fluid and cells. This could cause animal cells to dessicate or burst.
Independence from external conditions: animals with a constant internal
environment can maintain a constant level of activity regardless of their
environment.
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