Biology Sumery

SOME PRINCIPLES OF BIOLOGY

Cells and tissues
Cell structure
Cytoplasm
Thick liquid with particles in it. Particles exp iodinent be oil droplets or organelles. Chemical reactions take key in the cytoplasm.
Cell membrane
Thin layer of proteins around the cell. It controls the substances that are allowed to enter and leave the cell and maintains the cell structure.
Nucleus
It controls the type and meter of enzymes produced by the cytoplasm, so it regulates the chemic reactions. It controls cell division: a cell without substance cant reproduce. Inside the nucleus are chromosomes.
Mitochondria
Tiny organelles which are most numerous in regions of rapid chemical activity. They are responsible for producing energy from nutriment substances.
Plant cells
They have a cell wall make of cellulose which allows water and dissolved substances to pass through.
Mature plant cells declare a vacuole. The vacuole is full by cell sap, a faded solution of sugar, salts and pigments.
They have plastids in the cytoplasm. If they contain chlorophyll, they are called chloroplasts. dull plastids contain starch.
Cell division and cell specialization
Cell division
each(prenominal) cell in growing regions divides to produce two young lady cells.



These cells might divide again, but usually one of them changes and becomes competent to do one particular job; it becomes specialized and loses its index to divide.
Growth: result of cell division, followed by cell exaggeration and, in many cases, cell specialization.
Specialization of cells
They do one particular job.
They develop a different shape.
Special kinds of chemical change take place in their cytoplasm.
Nerve cells
consume electrical impulses to and from the brain
Long to connect distant parts of the body.
Their chemical reactions cause the impulses to travel along the fibre.
Guard cells of a stoma
on the loose(p) or close the stomatal pore in a leaf.
Curved shape and unevenly thickened cell walls.
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