Topic 1 Cells

Mrs : Jackie

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

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

Cell theory

Some organisms are made of cells with no partitions resulting in a structure with many nuclei

Multinucleated Muscle fibers

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

Types of viruses RNA 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

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

Magnification and resolving power 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

Resolving power- Huber Telescope

Electron Microscope

Has a resolving power of about .2 nanometer

1000 times higher than the light microscope.

Electron microscope picture

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

Yes No

Movement of organisms. Method of feeding and other processes can be viewed

Yes NO

A larger field of microscope view can be observed

Yes No

More suitable for studying organs and large structure

Yes No

More suitable for studying the details of small structures such as cell and organelles

NO Yes

Cheap, portable and easy to use Yes No

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=0.001mm1nm=0.001micrometer

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=6 5x5x6/5x5x5=1.2

Surface area to volume ratio of the 5cm is smaller than that of the 1cm cube

1cm5cm

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.

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

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