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This is our blog created for teaching module PGT436E.  

It is about Cell As a Unit of Life! 

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Unicellular and Multicellular Organisms

        What is organism? Organism is any living thing (plant or animal) that exist in this world. A living thing which can only be seen under a microscope is called a microorganism. An organism can be unicellular or multicellular. 

        Unicellular organism is an organism which only has one cell while a multicellular organism is an organism that made up of more than one cell. Unicellular organism usually quite active and always moving around. They can be easily found in water such as ponds, lakes, rivers and any moist area.Organisms such as amoeba, plasmodium, paramecium are unicellular organisms.

        Most animals and plants are multicellular organisms. Multicellular organism have different types of cells.  Each type of the cells contribute different functions. In humans, there are trillions of cells group into specialized tissues and organs. The examples of multicellular microorganisms such as hydra (animal) and spirogyra (plant) have shown as below.

Examples of unicellular organisms,

Paramecium

Amoeba

Plasmodium 

Examples of multicellular organisms,

 Hydra (Animal)

 Spirogyra (plant)

Similarities and Differences between Plant Cells and Animal Cells

Similarities : 

1. Basic units in plants and animals

2. Made of protoplasm

3. Has a cell membrane which encloses a nucleus and cytoplasm

4. Carries out chemical processes such as respiration

Differences : 

Animal Cells and Plant Cells

      a) Animal cells

• All living things include animals and plants are made up of cells. 
• Cells are the basic units of life.
• An animal cell is rounded with a nucleus in the middle.
• Animal cells are eukaryotic cells, filled with a transparent jelly-like substance and enclosed by a cell membrane.
• The transparent jelly-like substance known as cytoplasm.
• Protoplasm includes both structures of nucleus and cytoplasm.

  An animal cell

                                                  A human cell under microscope

      b)Plant Cells

• Plants are also made up of cells.
• Same as animal cells, plant cells also enclose by a cell membrane. The cell membrane is protected by cell wall. 
• A plant cell consists of a nucleus. 
• Each cell is filled with a jelly-like substance known as cyctoplsm. Both the nucleus and cytoplasm are made up of a substance known as protoplasm.
• Furthermore, some plant cells have a large space filled with cell sap. This large space is called vacuole. 
• Chloroplast is the organelles found in plant cells that conduct photosynthesis.   

 A plant cell

 

A plant under microscope

Functions of the Structures in Cells

Cell Structure     Function

Nucleus                Control all the activities in a cell

Cell membrane     Enclose and protect the cell

Cell wall               Maintains the shape of the plant cell

                            Act as protector to the plant cell

Cytoplasm           Keep water and nutrients inside the cell

Chloroplast          Produce chlorophyll which is required to do photosynthesis

Vacuole               Hold sap in plants

The Microscope

           A microscope is an used to examine specimens which are too small to be seen with the naked eye.  They are many types of microscope.  The most common and the first to be invented is the optical microscope.  Optical microscope uses light to image the sample.  It is very delicate and expensive instruments.  It must be used with great care.  

              

Parts of a Microscope and Their Function

1. Eyepiece : to observe specimen and enlarge the image formed by the objective lens
2. Body tube : to hold the lenses which magnify the specimen
3. Nose piece : the part that holds the objective
4. Objectives :  three or four of these lenses that have different magnifications/ to focus and enlarge the specimen
5. Stage : to support the microscope slide
6. Stage clip : hold the slides in place
7. Diaphragm : to control the amount of light entering the objective lens
8. Adjustment knobs : to raise or lower the lens tube for focusing.  The big knob is for coarse adjustment and the small knob is for fine adjustment
9. Light source/ Mirror : to reflect light into the objective lens
10. Base : bottom of the microscope which is used for support
11. Arm : for holding and taking the microscope