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T1 - Cells
Wednesday, 27 November 2019

Light
microscope

16:48

Electron Microscope

• Uses light as a • Electrons as a source of

source of
radiation
• Black and white image where
radiation
the colours enhanced by
• Resolution up
too 200nm
computers
• Living or non- • Only non-living specimen
living
because has to be done in a
specimen
vacuum due to the electrons
bouncing of air
...

• See organelles in great detail

How does a light microscope work?

1
...
The length of the
waves of visible light varies
...
It ranges from 400nm (violet light) to about 700nm
(red light)
...
The human eye can distinguish between these
different wavelengths
...

4
...

5
...

6
...
This is why many biological structures have
to be stained before they can be seen
...

Resolution = ability to distinguish between two
separate points
...
Greater resolution the
greater the detail
...
e
...


Waves
• Longer waves = lower their frequency, lower

amount of energy
...

• Shorter waves = higher frequency, greater amount
of energy
...

• Electrons are negatively charged particles which

orbit the nucleus of an atom
...

• Free electrons behave like electromagnetic
radiation
...

• Using an electron microscope, a resolution of
0
...


Electron Microscope
Transmission
Scanning electron
electron microscope microscope
• Beam of electrons

• Electrons are used to

pass through the
scan the surfaces of
specimen
structures; the reflected
beam reveals the shape
...

three-dimensional shape
...
show the same
resolution
...
Electron beam cannot be seen
...

• Dilute methylene blue can be used to stain animal cells like cheeks
...

• Cover slip is placed on top to protect the lens and to prevent the specimen
from drying out
...


Animal and Plant Cells Common Features
Cell membrane

1
...

3
...

2
...

2
...

1
...


Nucleus (stains intensely) =
Nucleus made out of chromatin which are loosely coiled threads
...

Nucleoli vary in number from 1-5 in mammals
...
Chemical reactions occur
Contains many organelles
Mitochondria =
Easily and commonly seen by light microscopes
Seen to move and divide
Carry out aerobic respiration
Golgi apparatus =
Part of a complex internal sorting and distribution system within in the cell
...


1
...

2
...


Cell membrane
• Very thin
• Partially permeable membrane
...

• At very high magnification, it can be seen to have 3 layers
...

•

This trilaminar appearance is described as having two dark lines (which are
heavily stained) which are either side of a pale interior
...
This
is useful as it increases absorption
...

• Increases reabsorption in tubes in the kidney
...

• Nuclear envelope has many nuclear pores
...


•

Substances leaving through PORES

Substances entering through
PORES

1
...
Proteins to make ribosomes
2
...
ATP (energy for protein
synthesis)
4
...
The
chromosomes contain genes and then DNA
...

• The nucleolus makes ribosomes using its own DNA
...

• Especially metabolic pathways including glycolysis and processes like cell

division
...
This releases energy from energy-rich

molecules such as sugars and fats
...

• ATP (adenosine triphosphate) is the energy-carrying molecule found in all
living cells
...
Most of this energy is transferred to
molecules of ATP
...

• The energy is released by breaking the molecule down to ADP
(adenosine diphosphate) in a hydrolysis reaction
...

• They carry out aerobic respiration AND synthesis of lipids

1
...

• The innards are folded to form finger-like cristae which hold the inner
solution called the matrix
...

• The matrix contains enzymes in solution
...

• The flow of electrons in the cristae provide the power to generate the ATP
molecules
...

• Once the folds have been made, ATP leaves thee mitochondria
...

2
...
Outer membrane contains a transport protein called porin
...

4
...
It controls precisely
what ions and molecules can enter the matrix
...
Liver and muscles contain lots of mitochondria because they need the
energy
...
If you exercise regularly then your muscles will make more mitochondria
...
Could be more than one in a cell
...
They

are then broken down again to form vesicles
...
It is the post office of the cell
...
It can add sugars to the protein to form
glycoproteins
...
Could be more than one in a cell
...
They
•
•
•
•

are then broken down again to form vesicles
...
It is the post office of the cell
...
It can add sugars to the protein to form
glycoproteins
...


Endoplasmic Reticulum
•
•
•
•

The ER is continuous with the outer membrane of the nuclear envelope
...

Rough ER is so called because it is covered in ribosomes
...
These vesicles joining
together to form the Golgi body
...


Ribosomes
• Ribosomes can only be seen by an electron microscope
...


•

At very high magnifications they can be seen to consist of two subunits: a
large and a small subunit
...

• They can be found free in the cytoplasm as well as on the rough ER
...


Found in Just Animal Cells Centrioles
• Located just outside nucleolus
• Hollow cylinder about 500nm long
• Formed by a ring of about 9 triplets’ short microtubules

•

Helps with cell division in animal cells - forms the spindle fibres that separate
the chromosome (mitosis)
• Sorts out the arrangement of the nucleus

Lysosomes
• Lysosomes are spherical sacs
...

They contain digestive enzymes so must be kept separate from the rest of the
cell to prevent damage from being done
...
This could
be old organelles
...

The heads of sperm also contain a special lysosome to break a path down for
the egg
...


Microtubules
• Microtubules are long, rigid, hollow tubes found in the cytoplasm
...

• They are made of a protein called tubulin
...

α- and β-tubulin molecules combine to form double molecules - dimers
...

Then 13 protofilaments then line up met to each other in a cylinder shape
...

It provides support to the cells
...

Microtubules form part of the structure of centrioles
...
This controls

the exchanges between the vacuole and the cytoplasm
• The fluid inside the vacuole is full of many components including sugars,
enzymes and other organic compounds
...
For example the
red pigment which makes beetroot red
...

The main function of chloroplasts is to carry out photosynthesis
...

Stages of photosynthesis –

1
...
The light energy is absorbed by chlorophyll
...
First stage of photosynthesis =
This is the light dependant stage
...

Some of this energy is used to manufacture ATP from ADP
...

The hydrogen is oxidised to provide the energy to make the ATP
...
E
...
ATP fetches the ribosome in
protein synthesis
...
These stacks up
like piles of coins and form a structure called grana
...
They also allow for the chloroplasts to change orientation so
that they can receive the lightest
...
The second stage of photosynthesis –
This is also called the the light independent stage
...

This takes place in a solution in the stroma, this is where sugars are stored
...
Black spheres can be seen in the
stroma, these are reserves of lipids in order to make membranes or to
destroy chloroplast membranes
...

• They are freely permeable
...
Some also contain other polysaccharides like

pectin
...

They link the cytoplasm’s to adjacent cells
...
They

form a living bridge
...
They

form a living bridge
...
e
...

Do not contain any membrane-bound organelles such as mitochondria
...

Some have a flagellum
...

• They are not surrounded by a partially permeable membrane containing

cytoplasm with ribosomes

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