1. Topic 1 Cells
Mrs : Jackie

2. Cell theory
States that all living organism are made of one or more cells
Cells arise from other cells
Chemical reactions such as respiration and other metabolic reactions occur within these cells
Cells carry genetic material that can be passed to the daughter cell

3. Cell theory Organisms can be divide into the following groups
Unicellular organisms which are also called acellular. Amoeba or bacteria
Multicellular made of many cells such as mammals

4. Cell theory
Some organisms are made of cells with no partitions resulting in a structure with many nuclei
Multinucleated
Muscle fibers

5. Viruses Non cellular organism Lack very important structures
They depend on other organism for their living and so they are parasites
Made of nucleic acid molecules surrounded by a protein coat

6. Types of viruses RNA viruses- DNA viruses
Contain RNA as their genetic material and they have an enzyme reverse transcriptase which transcribes RNA into DNA.
Call retroviruses
Example AIDS caused by HIV virus
Tobacco Mosaic Virus
DNA viruses
Contain DNA as their genetic material
They have an enzyme RNA polymerase which transcribes DNA into RNA in the process of protein synthesis

7. Advantages of using microscopes
Light microscope
Living cells and organisms can be observe alive
The resolution power of the microscope is about .2 micrometers and a typical cell is about 10 micrometers in length
Wide range of magnification (40-400X)
Easy to maintain
Portable can be use in the field
Tissues and small organ can be view

8. Magnification and resolving power
Show things more clearly
Ability to show two close points as separate points to distinguish them as separate points
Magnification
Power of making things larger in order to see them more clearly
FOR HIGHER MAGNIFICATION AND STONGER RESOLVING POWER AN ELECTRON MICROSCOPE CAN BE USED

9. Resolving power- Huber Telescope

10. Electron Microscope Has a resolving power of about .2 nanometer
1000 times higher than the light microscope.

11. Electron microscope picture

12. Aspect
Light microscope
Electron microscope
Natural color of tissue can be seen, since tissue can be viewed without the addition of any substances or stains
Yes NO
Living material such as live insect can be observed. Specimen can be prepared without the addition of any chemicals No
Movement of organisms. Method of feeding and other processes can be viewed
A larger field of microscope view can be observed
More suitable for studying organs and large structure
More suitable for studying the details of small structures such as cell and organelles
Cheap, portable and easy to use

13. Cells and organelles
Cell contain formed structures inside them called organelles.
Comparison of relative sizes of certain structures inside the cell
Structure
Measurement
Molecules
0.5-1 nm
Membrane
10nm
Virus
50-100nm
Bacteria
1-5micrometers
Organelles
5-10micrometers
Cells
10-100micrometers
1micrometer=0.001mm
1nm=0.001micrometer

14. Cells Has a three dimensional figure
Its surface to area volume provides enough surface to exchange
As the cell increases in size its surface area to volume decreases
1x1x6/1x1x1= x5x6/5x5x5=1.2
Surface area to volume ratio of the 5cm is smaller than that of the 1cm cube
1cm
5cm

15. Surface area to volume ratio
A small cell has a bigger surface to area ratio than a big cell
Advantages
Faster rate of diffusion, osmosis and other kinds of transport
More control by the nucleus
Getting rid of excess heat is more efficient in smaller cells.

16. Surface area to volume ratio
Materials such as resources such as RNA proteins and enzymes would be adequate enough in a small cell
Small cells such as sperm can move fast enough to reach their destination
Production of energy for different reactions and functions is more efficient in small cell
IN big cells substances would need to travel a longer distance in the cytoplasm to reach certain organelles

17. Surface area to volume ratio
When cell divide they increase in number and lead to a multicellular structure, which enables specialization and differentiation into different tissues and organs
A small organism can be made of many small cells that can carry out different functions