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Summary Cell ultrastructure
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MicroscopymmmmmmmA light microscope can be used to examine cells and to distinguish between a plant
and animal cell however to really see the detail inside a electron microscope is needed
,
.
Electron microscopes can organelles
be used to examine the within the cells .
There are two types of electron microscopes .
ITEM ) Transmission produces a 2D
image of a thin section of a
specimen must be thin for
electrons to pass through it .
(SEM ) scanning produces a 3D image since electrons are reflected of the surface .
Microscopes compared :
Light Transmission Em Scanning Em Electro
micrograph
Resolution how highest high may be artificially
Magnification Low highest high colour enhanced
specimen Living or dead Dead ( preparation Dead ( preparation to show features
through vacuum through vacuum more clearly
Chamber) Chamber)
Preparation Relatively easy Complex prep complex prep Artefacts are
training needed training needed distortions due to
cost how
high high Preparation techniques
black and white
*
white
*
Image obtained .
matches specimen black and these may mistakenly
natural colour or 2D 3D be thought as part of
stained Artefacts possible Artefacts possible the cell .
One key advantage of using electrons over light is that a
higher resolution can be
obtained .
Resolution : The ability to see two adjacent (but separate ) points as distinct
following magnification .
Magnification The number of
: times larger an observed image is in relation to the actual
size of the specimen .
distance between two points at which two distinct
Resolving power is the : minimum
points are visible .
will into two entities using EM , light needs
Olnm separate upwards of 200mm to be
visible as two entities .
Em can achieve higher
meaning magnification than light but can cost to 1 million up
.
Unitsofmeasurmentmmmmmmmm Eatcmtakinynmmagnificationmn mmm
1000mm = Im eyepiece lens size of
1000µm = 1mm
1 image
1000mm =/ micrometre 1µm) Barrel magnification
Actual
M A
coarse focus rotating size of
Arm nosepiece specimen
fine focus objective lens
stage stage clips note : measure in mm then convert
a.
to micrometres 1µm) by ✗ 1000
Diaphragm light source Give answer in µm
Base
, Plasmid small
EELLNULtrastructuremnmm DNA LOOP
storage granule
:c i. i. ÷ :-. :-. ii :-. .i :
"
ii. ii. '
glycogen lipids
.
.
, ' ' ' ' ' ' ' '
or
' ' ' ' ' ' ' ' '
DNA loop ✗ 4
Two distinct categories : free in cytoplasm ,
@⑧§
*
PROKARYOTIC
cell wall ÷'
÷ 's
*
*
*
% : slime
:
÷ capsule
is
-
simple cells that lack a membrane bound nucleus in
"↳Plasm
.
do not possess membrane bound 1 structure within cell)
.
organelles .
small in size .
"
÷ ! ! ! ! ! i' iii. -
'
::: ; :p ,
, ,
Bacteria possess prokaryotic cells are described as prokaryotes . ribosomes cell membrane
golgi bodies
EUKARYOTIC :
÷;
possess a membrane-bound nucleus containing the DNA smooth granules
.
,
Er
many different membrane bound organelles such as
chloroplast "
with specialised roles
µgzg
'
.
cytoplasm
nucleoplasm
.
larger size
:|
.
Animals, plants, fungi and protocista are all composed of eukaryotic nuclear
.
. nuclear
cells and known as eukaryotes chromatin
i÷÷
so are .
. . .
seen .me#.nmi....e. :
nucleolus
centriole
free ribosomes
Plasma
membrane Mitochondrion
T.tt#::::::...
Size Usually 5µm 10 200µm
site of DNA DNA freecytoplasm
in DNA inside membrane bound nucleus
DNA circular ( arranged as a loop ) DNA linear and chromosomes
organisation in
an without associated protein contain both helically arranged
DNA and
packaging protein /histones)
Ribosomes small -20mm (70s ) large 25mm 180s)
Internal structure no complex organelles complex membrane bound organelles
including nucleus , golgi and mitochondria
cell walls complex made of peptidoglycan Cellulose cell wall in plants
( glycoprotein) chitin cell wall in
fungi none in animal
Microtubules not present spindle fibres and other present
Plasmids usually present not present
Examples Bacteria Animals , plants , fungi protocista
,
PLANT CELL
Plasmodesmata
&" " "
""" " cell wall
:€÷: ÷¥:¥¥÷
:÷i ÷: ÷ ÷ ÷¥ :*
space nucleus
÷¥¥É÷÷÷÷÷÷
"""" centrioles
nucleus
smoother
÷ apparatus
rough Er .
☒
Mitochondria
chloroplast
.
Tonoplast .
golgi
:
lamella
reticulum
cell membrane
apparatus
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