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Title: Cell Structure
Description: Chapter 3 of AQA A Level Biology - Cell Structure. Includes: * Eukaryotic cell structure and organelles. * Prokaryotic cell structure and organelles. * Microscopy. * Cell fractionation and ultracentrifugation. * Mitosis.
Description: Chapter 3 of AQA A Level Biology - Cell Structure. Includes: * Eukaryotic cell structure and organelles. * Prokaryotic cell structure and organelles. * Microscopy. * Cell fractionation and ultracentrifugation. * Mitosis.
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Chapter 3 - Cell Structure
Eukaryotic Cells
A cell that contains a true nucleus is called a eukaryotic cell
...
Organelle
Description
Nucleus
Largest cell organelle
...
Contains small nuclear
pores to allow proteins to
move out of the nucleus
...
● Controls the activity of the
cell
...
Nucleolus
1-2 micrometers in
diameter
...
● Where ribosomes are
made
...
The outer layer is
continuous with the RER
and encrusted with
ribosomes
...
● Allows substances to
exchange across
membranes
...
Contains ribosomal
RNA
...
● Carries out
proteinsynthesis
...
Common in
cells that secrete h
ormones
and that m
etabolise lipids
...
Rough Endoplasmic Complex 3D system of
Reticulum
flattened sacs and
membranes
...
with ribosomes
...
Cell-surface
membrane
Double membrane
...
● Regulates m
ovement of
molecules in and out of
cells
...
Mitochondria
Double membrane
...
The matrix makes
up the rest and contains its
own DNA
...
● Provides a large surface
area for enzymic activity
...
A Golgi vesicle is
a small, spherical organelle
bound by a single
membrane
...
● Involved in the synthesis
and modification of
biological molecules from
the endoplasmic
reticulum
...
Chloroplasts
Double membrane
...
Contains their own
circular DNA
...
Cell Vacuole
Contains cell sap
...
● Maintains pressure inside
the cell and keeps it turgid
...
Cell Wall
Made of beta glucose
(cellulose)
...
● The cell wall prevents the
cell changing shape to
withstand t he p
ressures of
osmosis
...
Lysosomes
Type of Golgi v
esicle
...
● Contains hydrolytic
enzymes to break down
unwanted organelles or
material taken into the cell
by p
hagocytosis
...
These cells contain no true nucleus,
contain no membrane-bound organelles and are much smaller a
nd simpler than
eukaryotic cells
...
Capsule
Protects the cell and allows a
ttachment to other
objects
...
Plasma
Controls t he f low of small molecules in and out of
the cell
...
Nuclear zone
Contains the D
NA and RNA
...
Plasmids
Circular DNA not associated with histones
...
What is the difference between eukaryotic and prokaryotic cells?
Eukaryotic
Prokaryotic
Much bigger
...
Membrane-bound organelles
...
Contains a nucleus
...
DNA associated with histones
...
80s ribosomes (much bigger)
...
DNA enclosed in a nucleolus
...
Microscopy
Optical Microscope - U
ses light and lenses to magnify images
...
Resolution is much lower as light has a much longer wavelength than electrons
...
Scanning Electron Microscope - Directs a beam of electrons onto the surface of the
specimen
...
Specimens can be viewed in colour and
3D
...
Resolution is 20nm
...
The resolution is 0
...
The specimen must be
extremely thin, there is a complex staining process for preparing a sample and living
specimens cannot be viewed
...
Cell Fractionation and Ultracentrifugation
Cell f ractionation is the process by which scientists break open cells to study and
separate different organelles
...
Cold - To reduce enzymic activity breaking down the organelles
...
Buffered - To ensure that the pH does not fluctuate
...
The cell is placed in a homogeniser
...
The resulting fluid (homogenate) is then filtered to remove
debris
...
This removes the
most dense organelle (nucleus)
...
● Nucleus (most dense/lowest speed)
...
● ER
...
Mitosis
Mitosis i s important for growth, repair and reproduction, producing two genetically
identical daughter cells
...
The cell grows (G1), organelles are
synthesised (S) and the DNA is
checked for m
utation (G2)
...
Rapid
interphase suggests uncontrolled cell
division
...
The centrioles
divide
...
Sister chromatids are joined by a
centromere and chromosomes move
to the opposite p
oles of the cell
...
Prophase
Metaphase
Image
Each centriole is at an opposite pole
...
Each c
entromere is a
ttached to each
pole
...
Chromatids
are pulled to the poles (centromere
first) and each half of the cell now has
one chromatid
...
Spindle fibres
disintegrate and the nucleolus and
nuclear envelope reform
...
Two genetically
identical daughter cells are formed
...
Title: Cell Structure
Description: Chapter 3 of AQA A Level Biology - Cell Structure. Includes: * Eukaryotic cell structure and organelles. * Prokaryotic cell structure and organelles. * Microscopy. * Cell fractionation and ultracentrifugation. * Mitosis.
Description: Chapter 3 of AQA A Level Biology - Cell Structure. Includes: * Eukaryotic cell structure and organelles. * Prokaryotic cell structure and organelles. * Microscopy. * Cell fractionation and ultracentrifugation. * Mitosis.