Biology GCSE AQA Grade 9 Unit 2: Organisation notes made by Grade 9 student, now studying A level Biology. Includes all relevant details adhering to the specification and visual aids, such as diagrams, pictures, coloured notes, etc.. Similar quality notes available for all units for each triple sci...
Organelle: a specialized structure within a cell with a specific
function. (nucleus, cytoplasm)
Cell: the smallest structural and functional unit of life.
(neurons, muscle cell)
Tissue: group of similar cells that carry out a specific function.
(nerves, muscle tissue)
Organ: groups of tissues adapted to perform a specific
function. (brain, heart)
Organ system: group of organs working together to perform
one or a more functions. (nervous system, circulatory system)
Organism: a living thing, for example an animal, humans or
plants. (humans)
Specialised Cells
Cells become specialised as an organism develops and cells differentiate to form different
types of cells.
Most animal cell types differentiate at an early stage, but many plant cell types
differentiate throughout their life.
As a cell differentiates:
- it may change shape
- different sub-cellular structures develop to let it carry out a specific function
If cells are specialised, they become more efficient at their job but may lose the ability to do
other jobs.
Specialised animal cells:
Axon
A sperm cell Dendrites
Nucleus: contains only one set of
the genetic material.
Sheath
Mitochondria: sperm have
many of these to provide
energy for their journey. A motor neurone
Cell body
Acrosome: contains enzymes to
allow the sperm to penetrate the
outer layer of the egg.
Tail: to propel the sperm to
fertilise the egg.
, Specialised plant cells:
Root hair, xylem and phloem cells are specialised to transport water, minerals and sugars around the plant.
Xylem Phloem
Xylem cells are arranged end The end walls of the cells
to end but the walls break allow sugars through but
down to form hollow tubes. support the tubes.
Phloem cells are arranged
The cell wall of the cells is end to end in tubes.
strengthened by a substance
called lignin.
Companion cell
Root hair cell
Lots of mitochondria for
active transport of minerals
Long projection to increase
the surface area to absorb
water and minerals.
Enzymes
Biological catalysts
Speed up chemical reactions in living organisms Catabolic enzymes
Can be reused multiple times break down
Made of amino acids i.e. large proteins substancesAnabolic
enzymes build raw
Each enzyme catalyses a specific reaction
materials into more
Work best at a specific temperature and pH called the optimum complex substances
There is a space within the protein molecule called the active site
Lock and Key theory
- This is a model used to explain how enzymes work.
- The chemical that reacts is the substrate (key) and it
fits into the enzyme’s active site (lock).
Denaturation:
- When the pH or temperature are beyond the
optimum for a specific enzyme the active site gets
damaged and changes shape.
- The substrate can no longer bond to the enzyme, and
the enzyme no longer works.
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