Science =)

CHAPTER 2

Cell as a Unit of Life


2.1 What is cell?

>basic unit of all living things
>including animals, plants and humans
>the smallest unit of living things
>has its own functions


Using a Microscope


How to use a microscope

1. Place the microscope on a flat surface in well-lit place
2. Turn the low-power objective lens until it is directly above the hole in the stage
3. Raise the condenser to its highest position. Adjust the opening of the diaphragm to the maximum to allow as much light as possible to enter
4. Look through the eyepiece. Adjust the mirror to obtain a bright field of view
5. Place a slide with the specimen onto the stage and clip to hold it in place
6. Start with a low magnification. Turn the coarse focus knob clockwise to move the body tube down until it almost touches the slide
7. Look through the eyepiece. Turn the coarse focus knob anticlockwise to move the body tube up, until the image of the specimen can be seen clearly
8. Turn the fine focus knob to obtain a sharp image



General structure of animal cells and plant cells

Nucleus:-
# found at the centre of cell
# spherical shape
# control all activities of cell

Cytoplasm:-
# jelly-like medium
# contains water and many other substances such as protein, starch, minerals and vitamins

Cell membrane:-
# forms the outer boundary of cell
# substances move into and out of cell through cell membrane

Vacuoles:-
# fluid-filled sac found in cytoplasm
# animals tiny spaces containing air, liquid and food substances
# forms the biggest part of cell and usually reduces cytoplasm to thin lining
# vacuole filled with cell sap
# cell sap contains water and dissolved substances sugar and salt

Cell wall:-
# rigid outer wall of plant cell
# tough substance called cellulose which forms layer around cell
# support and gives shape to the cell

Chloroplasts:-
# small disc-like structures found in green plants
# green pigment called chlorophyll


The functions of cell structures
Animal cells


Plant cells






Unicellular Organism and Multicellular Organism

 has only one cell
 e.g.> yeast, amoeba, paramecium, euglena and chlamydomonas
 known as unicellular organism cause they are very tiny sizes
 Amoeba and Paramecium animal kingdom
 Chlamydomonas, Euglena and Pleurococcus plant kingdom



Multicellular Organism


 consist of many cells
 made up of more than one cells
 they have a large number of cells
 Hydra, Spirogyra and Mucor


a) Spirogyra

 multicellular plants
 cylindrical in shape
 combine to form long filament
 green cause has chlorophyll
 makes its own foods


b) Mucor

 fungus
 consist of a mass o branching threads or hyphae


c) Hydra

 multicellular animal
 cylindrical shape
 flat and attaches itself to water plants
 end with tentacles functions as a mouth
 walls of its body have two layers of cells