Biology Unit 2 Key Points

The Key Points you need to know about Biology Unit 2.

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  • Created on: 16-03-12 17:47
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Biology Unit 2 Key Points
1. Cells
a) Animal cells
I) A nucleus to control the cells activities
II) Cytoplasm where many chemical reactions take place
III) Cell Membrane to control the movement of materials
IV) Mitochondria where energy is released during aerobic respiration
V) Ribosome's where protein synthesis happens ­ proteins are made
b) Plant cells also have
I) A rigid cell wall for support
II) Chloroplasts which contain chlorophyll for photosynthesis
III) A permanent vacuole containing cell sap
c) Specialised cells
I) As organisms develop some of their cells become specialised to carry out
different jobs, this is called differentiation.
II) Differentiation happens earlier in the development of animals than plants
d) How substances get in and out of cells
I) Molecules move randomly because of the natural energy they contain
II) Diffusion is the random movement of molecules from an area of high
concentration to an area of lower concentration.
III) Diffusion requires no energy from the cell
IV) The larger the difference in concentration, the faster the rate of diffusion
V) One example is the diffusion of oxygen into cells of the body from the blood
stream as the cells respire ­ use up oxygen
VI) Carbon Dioxide diffuses into actively photosynthesising plant cells
e) Osmosis
I) Osmosis is the movement of water across a semi/partially permeable
membrane, it is a special kind of diffusion
II) Like diffusion it is the random movement of molecules which requires no energy
from the cell
III) The water moves from a more dilate solution to a more concentrated solution.
IV) No solute molecules can cross the partially permeable membrane
V) Water is needed to support cells because chemical reactions take place in
VI) Some water will pass through the partially permeable membrane from low to
high concentration but the net movement of water is from high to low

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How Plants Produce Food
a) Photosynthesis
I) Carbon Dioxide + Water (+ Light Energy) Glucose + Oxygen
II) Carbon dioxide is taken in by the leaves and Water by the roots
III) The chlorophyll traps the energy required for photosynthesis
IV) Photosynthesis can only be carried out by green plants ­ chlorophyll makes the
leaves green
b) Limiting Factors
I) If things like Sunlight, Water and Carbon Dioxide are in short supply, or the
temperature is not right it slows down the rate of photosynthesis…read more

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III) Some is used for respiration ­ which releases energy for living processes like
movement ­ the more something moves, the more energy it uses
IV) Some animals require a constant temperature so some of the energy is used to
maintain this temperature.
c) Energy in Food Production
I) The shorter the food chain the less energy will be lost ­ it is more efficient to eat
plants than animals.…read more

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II) If the temperature gets to hot the enzymes active site changes shape and it
becomes denatured
III) Enzymes work at different PH's depending on where they are naturally found ­
if the ph is to alkali or acidic it can cause the active site to change shape
c) Aerobic Respiration
I) Glucose + Oxygen Carbon Dioxide + Water (+ energy)
II) The process takes place mostly in the mitochondria
III) The energy released can be used for building larger molecules from smaller ones
enabling…read more

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Controlling internal conditions
I) We must remove the waste products produced through chemical reactions from
the body
II) Homeostasis is the processes in the body which help to maintain a constant
internal environment
III) We have to keep our internal temperature the same as well as coping with
blood sugar and varying rates of respiration needed during different activities
IV) Carbon Dioxide is a waste product of respiration and is excreted through the
V) Some of the amino acids we take in are not…read more

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I) Stem cells are unspecialised so they can develop (differentiate) into many
different types of specialised cell
II) Stem cells are found in embryos and in adult bone marrow
III) Most embryonic stem cells that we carry out research on are from aborted
embryos or spare embryos from fertility treatment ­ this causes ethical issues
because some people argue that you are destroying life to obtain these stem cells
for research
IV) The use of stem cells from adult bone marrow is still limited by…read more


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