Simple Microscope
• uses single lens
• max magnification x400
• uses light
Compound Microscope
• microscope used in our labs.
• max magnification x1000

Compound Microscope
•
Has two magnifying lens:
the Eyepiece Lens is the lens that you look through.
- the Objective lens is the lens that is immediately above the specimen.

Compound Microscope
The Objective Lens:
•
There are three objective lenses:
- the scanning lens with the 4X label
- the low power lens with the 10X label
- the high power lens with the 40X label

Compound Microscope
Parts of the Microscope

Compound Microscope
Parts of the Microscope
Part Function
Lenses
Stage
Clips
Diaphragm
Magnification
To place the slide on
Hold the slide in place
To control the amount of light
Coarse Focus Knob To focus the image
Fine Focus Knob To precisely focus the image
Light To supply light to the object

Compound Microscope
Magnification
Total Magnification: magnifying power of the eyepiece lens x the magnifying power of the objective lens
Example:
Eyepiece lens = 10X
Objective lens = 4X
Total magnification = 10 x 4= 40X

Cell Structure seen using the
Light Microscope
Robert Hooke
Robert Hooke looked at thin slices of cork under a microscope.
He thought the spaces he saw reminded him of Monks Cells –
Hence the name cells

Cell Structure seen using the
Light Microscope
Animal Cell
Cytoplasm:
• living material outside the nucleus.
• most reactions take place in cytoplasm.
Protoplasm:
• comprises all the living parts of the cell e.g. Nucleus and surrounding cytoplasm.

Cell Structure seen using the Light
Microscope
Cell Wall:
- made of cellulose
- function: support
Cell Membrane:
- pressed close to cell wall
Vacuoles:
- contain cell sap
Plant Cell
- function: strength shape store materials
Chloroplasts:
photosynthesis

Electron Microscope
Allow cell structure to be seen in greater detail
- ultrastructure

Electron Microscope
•
Uses Electrons instead of light
•
Electrons have much lower wavelength than light – image is shown on a screen or as a photograph
•
Resolution is much better
•
Magnification is much greater

Images from Electron Microscope
Bacteria
Platelet
Cytoplasm

Electron Microscope
2 Types
Transmission Electron
Microscope (TEM)
• beam of electrons sent through thin section of the sample and shows the INTERNAL structure
Scanning Electron
Microscope (SEM)
• beam of electrons provides a surface view.

Cells
- All living things are composed of one or more cells.
- Cells are the basic units of structure and function in an organism.
- Cells come only from reproduction of existing cells.

Organelles
•
Cells contain a variety of internal structures called ORGANELLES.
•
An organelle is a cell component that
PERFORMS SPECIFIC FUNCTIONS FOR
THE CELL

Organelles we need to know
• Cell membrane
• Nucleus
• Mitochondria
• Chloroplast
• Ribosomes
• DNA
• Cell Wall
• Vacuole
• Nucleolus

Animal Cells
Animal Cells contain the following structures
Cell Membranes
Mitochondria
Nucleus
Cytoplasm
Only the cell membrane, the cytoplasm and the nucleus can be seen under the light microscope.

Cell (Plasma) Membrane
Cell Membrane: composed of phospholipids and proteins.

Cell (Plasma) Membrane
Phospholipids:
• contain a water-loving phosphate group and a water-hating lipid group.
Phosphate
(Water loving)
Lipid
(Water Hating)
• arranged into double layers - bilayers

Cell (Plasma) Membrane
Proteins:
• completely or partially embedded in phospholipid bilayer.
The phospholipids and proteins are in constant motion.
Therefore membranes are thought of as fluids

Functions of Cell Membrane
•
Separate the cell organelles and cytoplasm from the outside.
•
Semi permeable
– controls what enters and leaves the cell.
•
Membranes give some support to the cell.
•
Membranes recognise molecules that touch them.

Nucleus
•
A large organelle near the center of the cell is the NUCLEUS.
•
It contains the cell's genetic information.
•
It is the control centre of the cell.

Ultra Structure of the Nucleus

What’s in the Nucleus???
Double Membrane: nucleus is surrounded by a double membrane with nuclear pores.
Nuclear Pores: allows the controlled entry and exit of molecules in and out of the nucleus e.g.
- allow a type of RNA called mRNA to pass in and out of the nucleus.
Nucleolus:
• contains RNA, DNA and protein.
• is responsible for making ribosomes which are made up of RNA (Ribonucleic acid).

What’s in the Nucleus???
Chromosomes:
• nucleus contains strands of DNA which are arranged into structures called Chromosomes.
• genes are located randomly along chromosomes: genes = units of inheritance
• when cell is not dividing the chromosomes form a mass of threads called chromatin.

Functions of Nucleus
• directs growth, development and activities of the cell.
• makes replicas of DNA for new cells
• carries out cell division
• instructs the formation of enzymes and hormones

Cytoplasm
• liquid in a cell that surrounds the nucleus
• small bodies called organelles are suspended in the cytoplasm:
1. Mitochondria
2. Chloroplasts
3. Ribosomes
4. Vacuoles

Cytoplasm Organelles
Mitochondria

Cytoplasm Organelles
Mitochondria
•
Found in all cells except bacteria.
•
Supply energy to the cell – sites of respiration:
Lots of mitochondria Lots of energy
Few mitochondria Less energy
•
Consist of a smooth outer membrane and a
folded inner membrane.
•
It is on the inner membrane, especially the infoldings, that energy is released. Therefore the more infoldings the more energy produced.

Cytoplasm Organelles
Mitochondria
Inactive mitochondria:
- have a decrease in infoldings and as a result a decrease in the energy released.
Active mitochondria:
have a increase in infoldings and as a result an increase in the energy released.

Cytoplasm Organelles
Chloroplasts (Plants Only)
•
Found in plant cells only.
•
Green structures in which photosynthesis takes place.
•
Contain the green pigment chlorophyll.

Cytoplasm Organelles
Ultrastructure of the Chloroplast
The thylakoids contain the chlorophyll which traps the sun’s energy

Cytoplasm Organelles
Ribosomes
•
Found in all cells
•
Tiny, bead – like structures
•
Made up of ribonucleic acid (RNA) and proteins.
•
Function:
to make proteins by combining a sequence of amino acids.

Cytoplasm Organelles
Vacuoles
•
Vacuoles are membrane-bound sacs within the cytoplasm of a cell.
•
Vacuoles provide structural support, as well as serving functions such as storage, waste disposal, protection, and growth.
•
Plant cells have large vacuoles

Cell Wall
•
Found in plant cells only
•
Made of cellulose
•
Very strong and contributes the following to the cell:
- strength
- protection
- shape

Ultra Structure of an Animal Cell

Ultra Structure of a Plant Cell

Differences between Plant and
Animal Cells
Plant Cells Animal Cells
Have cell walls No cell walls
Contain chloroplasts Do not contain chloroplasts
Contain chlorophyll Do not contain chlorophyll
Have large vacuoles Have small (if any) vacuoles

Living things can be placed into special categories depending on the complexity and structure of their cells.

Prokaryotic Cells
Do not have a nucleus or membrane enclosed organelles.
•
They are single celled organisms e.g. Bacteria
•
Their DNA is found as circular loops found in the cytoplasm.
•
Do not have mitochondria or chloroplasts.
•
Respiration and photosynthesis is carried out on infolding of the plasma membrane.

Eukaryotic Cells
Have a nucleus and cell organelles, all of which are enclosed by membranes
•
More advanced than prokaryotic cells.
•
Larger than prokaryotic cells .
•
Plant and animal cells are examples of eukaryotic cells.