2.1 Cell Structure & Function

Biology Form 4

Chapter 2: Cell Structure and Cell Organisation

Subtopic 2.1: Cell Structure & Function

Introduction to cells.



What are cells?
  • are basic units of living organisms
  • Consist of Protoplasm:
    • living component of a cell
    • surrounded by a thin layer called the plasma membrane
    • made up of cytoplasm & nucleus
    • contains small structures called organelles
  • Most of the organelles can only be seen using an electron microscope
  • Plants cells have an outer layer called the cell wall
Animal Cells

Animal Cells

Plant Cells

Plant Cells

Cellular Components of Animal and Plant Cells

Cellular components can be classified into organelles or non-organelles


a) Nucleus

  • cell-nucleus-5-638Functions :
    • Controls all activities of the cell
    • Nucleolus is involved in the synthesis of ribosomes and ribonucleic acid (RNA)




b) Mitochondria


  • Functions :
    • Sites of cellular respiration
    • Enzymes involved in cellular respiration to help oxidise glucose to release energy in the form of ATP (Adenosine TriPhosphate)



c) Endoplasmic reticulum (ER)


  • Two types of ER
    • Rough Endoplasmic Reticulum (RER) – has ribosomes on its surface
    • Smooth Endoplasmic Reticulum (SER) – has no ribosomes on its surface
  • Functions :
    • RER transports proteins synthesised by ribosomes
    • SER synthesises lipids and is the centre for detoxification of drugs


d) Golgi apparatus


  • Functions :
    • Centre for processing, packaging and transporting macromolecules such as proteins and carbohydrates




e) Ribosomes


  • Functions:
    • Sites of protein synthesis




f) Lysosomes


  • Functions :
    • Break down macromolecules such as proteins, lipids, nucleic acids, polysaccharides as well as worn-out organelles







g) Vacuoles


  • Usually found in plants cells, in animals cells, if vacuoles are present they are small
  • Functions :
    • Store food substances such as sugars and amino acids
    • Site for waste products
    • Regulate water balance in cells
    • Turgidity of cells gives support to plants



h) Centrioles


  • Only found in animal cells
  • Functions:
    • Form spindle fibres during cell division



i) Chloroplast


  • Only found in green plants
  • Functions :
  • Site for photosynthesis
    • Chlorophyll traps light energy for photosynthesis




Non-organelles components

a) Plasma membrane


  • Functions :
    • Regulates and controls the movement of substances in and out of the cells
    • protects the cell by separating the content of the cell from its environment



b) Cytoplasm


  • Functions :
    • Place where biochemical reactions occur






c) Cell wall


  • Only found in plant cells
  • Functions :
    • Maintain the shape of plant cell
    • protects the cell from bursting
    • gives support to cells






Comparing and contrasting the structure of animal and plant cells




The Density of Certain Organelles in Relation to Functions of Specific Cells

What are organelles?

  • “little organs”
  • Are tiny structures inside a cell that perform specific functions for the cell
  • 3 main functions of organelles:
    • Carry out their specialized functions:
      • E.g. Mitochondria produce energy in the form of ATP
    • Acts as containers to separate parts of the cell from other parts
      • E.g. lysosomes
    • Sites for chemical reaction
      • E.g. Choloroplast

Relationship between the Density & Functions of certain Organelles

  • Plant and animals are made up of different types of cells
  • Different cells carry out different functions.
  • For example, muscle cells bring above movement while nerve cells transmit nerve impulses
  • The density of certain organelles in a specific cell is related to its specific function




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