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- 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

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 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 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

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

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 1cm 5cm

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