Biology- F4 Chapter 2.1

• Cells


  The basic units of life
• Types of cells

  • Animal cells
  • Plant cells
• Animal cell

  • Irregular shape
  • Absent cell wall
  • Absent chloroplast
  • Smaller or absent vacuoles
  • Carbohydrate storage form: Glycogen
  • Present centrioles
• Plant cell

  • Fixed shape (due to presence of cell wall)
  • Present cell wall
  • Present chloroplast
  • Larger vacuoles
  • Carbohydrate storage form: Starch
  • Absent centrioles
• Cell components/organelles found in both animal and plant cells

  • Plasma membrane
  • Nucleus
  • Cytoplasm
  • Golgi apparatus
  • Mitochondria
  • Endoplasmic reticulum
  • Ribosomes
• Plasma membrane


  Outer membrane that separates the inside and outside of the cell, made up of proteins and phospholipid bilayer, semi-permeable
• Functions of plasma membrane


  • Enclose all cell components within the cytoplasm
  • Regulate exchange of ions, nutrients, respiratory gases and waste materials between the cell and external environment
• Nucleus

  Largest component in the cell, contains nucleolus, chromosomes (DNA) and nucleoplasm, surrounded by nuclear membrane
• Functions of nucleus

  • Control all cell activities, which include the characteristics of the cell and metabolic processes
• Cytoplasm


  Gel-like fluid that fills the cells, contains proteins, ions, sugars, amino acids, nucleotides and mostly water
• Functions of cytoplasm

  • Support the internal structure of the cell
  • Maintain shape and consistency of the cell
  • Store various chemical substances essential for life
  • Medium for metabolic activities
• Rough endoplasmic reticulum (RER)

  Its membrane is continuous with the nuclear membrane, contains ribosomes on the surface
• Functions of RER

  • Presence of ribosomes help to synthesize proteins
  • Transport proteins to Golgi apparatus for modification
  • Provide surface for enzyme attachment and biochemical processes
• Smooth endoplasmic reticulum

  Membrane-bound network of tubules, absence of ribosomes on its surface
• Functions of smooth ER

  • Synthesize lipids, steroids, carbohydrates
  • Involved in the metabolism of drugs or toxins
• Mitochondrion


  Membrane-bound organelle, contains two layers of membrane - outer and inner membranes
• Functions of mitochondria

  • Generate energy in the form of adenosine triphosphate (ATP) during cellular respiration
• Golgi apparatus


  Membrane-bound organelle, single layer membrane
• Functions of Golgi apparatus

  • Modify, package and transport carbohydrates, proteins and lipids into vesicles to be transported out of the cell
• Centrioles


  Tiny paired cylindrical organelles located near nuclear membrane, made up of microtubules, absent in plant cells
• Functions of centrioles

  • Form spindle fibres to separate chromosomes during cell division
• Lysosome


  Small circular membrane-bound organelle, contains digestive enzymes called lysozymes
• Functions of lysosomes


  • Destroy bacteria and viruses
  • Break down damaged or dead cells in the body
  • Digest macromolecules such as proteins, lipids and nucleic acids
• Ribosome


  Can be found in the cytoplasm or on the surface of RER, made up of two subunits - small and large ribosomal subunits
• Functions of ribosomes

  • Involved in protein synthesis
• Cell wall

  Only exist in plant cells, outer membrane that surrounds the plasma membrane, made up of cellulose, fully permeable
• Functions of cell wall

  • Protect the cell from osmotic and mechanical stress
  • Help to maintain the shape of the cell
• Chloroplast

  Can be found only in plant cells, double layer membrane, contains chlorophyll which gives the plant its green color
• Functions of chloroplasts


  • Convert light energy to chemical energy during photosynthesis
• Vacuole


  A space within cell that does not contain cytoplasm, surrounded by tonoplast membrane, larger vacuole in plant cells, smaller in animal cells, contains water, enzymes, ions, respiratory gases and waste products
• Functions of vacuoles

  • Store water to maintain turgidity of the cell
  • Excrete unwanted substances out of the cell