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Cells and their activities

 

Cells, tissues, organs and organism


  • All living things are made from very small components called CELLS.  Cells are the smallest units of living matter.  They are the building blocks of all living things.
    • Extremely tiny living things, otherwise known as Micro-organisms may consist of one cell, but larger animals and plants are made up of many cells.
    • There are many different types of cells and they carry out different jobs within a living organism.
    • When the same type of cells work together, they are called a TISSUE. Different tissues working  together are known as an ORGAN.  These organs have special structure to carry out a particular function.


Cells and their activities

 

  • Cells have many structures in common, but there are notable differences between animal and plant cells.
  • Cells divide during reproduction and growth.
  • Function of the cell determines its structure.

 

Animal and Plant cells

Plant and animal cells

Fact: Although plant and animal cells differ in structure from each other, they all share  three common features which enable them to carry out their jobs.

 

These features include: Nucleus, Cytoplasm and Cell Membrane

    Nucleus

    The control centre of the cell and contains the thread-like structures called chromosomes which are composed of DNA -  the genetic material.  This consists of the information needed to make a living thing.

  •  All the cells instruction come from this genetic material.

  • This is passed from one generation to another by inheritance.

  • And give living things its characteristics.

 

Cytoplasm

This jelly-like material contains many tiny structures known as organelles, which keep the cell alive. All the chemical processes happen in this part of the cell.  The speed at which these chemical reactions happen is controlled by enzymes.

  • The organelles have a particular function.

  • For example, mitochondria are the organelles in the cells which produce energy (respiration) and small granules of stored food.

 

Cell membrane

It forms the boundary of the cell and is made from a very thin protein layer.  The membrane controls what moves in and out of the cell.  Only certain type of materials are able to cross the membrane, either using active transport mechanism or by diffusion.

Fact: Plant cells differ from animal cells in three ways.  They have Cellulose cell walls, chloroplasts and an inner membrane surrounding a vacuole.

 

Cell wall

Made of cellulose and it gives rigid support and toughness to the cell.

 

Chloroplasts

Are green because they contain the green pigment of chlorophyll and used for photosynthesis.  Chlorophyll absorbs light energy, which is used by the plants to make food and grow.

 

Vacuoles

A large space filled with a week solution of sugar and salt called, watery sap.  Turgor pressure, due to water, in the vacuole pushes the cytoplasm against the cell wall, aiding plants to maintain their shape.  When the vacuoles are full of watery sap, plant cells are strong and rigid.

Fact: Cells are able to divide to make more cells, so that plants and animals can reproduce, grow and repair their tissues.  Cells divide in two different ways.

 

Mitosis

This type of cell division takes care of growth and tissue repair.

 

Meiosis

Happen with sex cells during reproduction.

 

Special Cells and their function

 

 

Tags:Cells, Tissues, Organs, Organisms, Nucleus, Cytoplasm, Cell Membrane, Cells in living things

 

 

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