cell structure
prokaryotes are simpler organisms
bacterial cells are much smaller than plant cells
cell membrane
site of chemical reactions in the cell
it is a Gell like substance containing enzymes to catalyse the reactions.
bacterial DNA
Floats in the cytoplasm
it controls the functions of a cell
cell wall
is not made of cellulose
it supports and strengthen the cell
plasmid
are small rings of DNA
it contains additional genes
cytoplasm
semi permeable
controls the movement of substances in and out of the cell
specialised cells
specialised animal cells
specialised plant cells
nerve
carries electrical signals
long branches connections and insulating sheath
sperm
fertilises an egg
streamlined with a long tail, acrosome containing enzymes, large number of mitochondria
muscle
contracts to allow movement
contains a large number of mitochondria
root hair cell
absorbs water and minerals from soil
xylem
phloem
carries glucose
carries water and minerals
hair like projections to increase surface area
TRANSPIRATION - dead cells cell walls toughened by lignin and flows in one direction
TRANSCOLATION - living cells cells have end plates with holes and flows in both directions
cell differentiation
animal cell differentiation
how a cell changes and becomes specialised , undifferentiated cells are called stem cells
plant cell differentiation
early stages of development only for repair and replacement
all stages of life cycle the system cells are grouped together in meristems
microscopy
magnification (m) = size of image (i) divided by real size of the object (a)
electron beams
light rays
radiation used
~ 2 000 000
~ 1500
Max Magnification
0.2nm
200nm
Resolution
very large and not possible
small and portable
size of microscope
several £100,000 to £1 million plus
~£100 for a school one
cost
prefixes
milli (mm)
centi (cm
micro (um)
nano (nm)
1 cm = 0.01m
x10-2
1mm = 0.001m
x10-3
1um = 0.000001m
x10-6
1nm = 0.000000001m
x10-9
eukaryotes complex organisms
animal cell
plant cell
cytoplasm
site of chemical reactions in cell
gel like substance contains enzymes to catalyse the reactions
nucleus
contains genetic material
controls the activities of the cell and codes for proteins
cell membrane
semi permeable
controls the movement of substances in and out of the cell
ribosome
site of protein synthesis
MRNA is translated into an amino acid chain
permanent vacuole
contains cell sap
keeps cell turgid, contains sugars and salts in solution
cell wall
made of cellulose
supports and strengthens the cell
chloroplatsts
site of photosynthesis
contains chlorophyll, absorbs light energy
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