Biology (bri) cell

• The cell is the basic unit of life.
• Cell theory states that all living things are made up of cells, cells come from other cells, and cells contain hereditary information.
• There are two types of cells: prokaryotic (simple) and eukaryotic (complex).
• Cells


  Structural and functional units of all living organisms
• Types of organisms based on number of cells

  • Unicellular organisms (e.g. bacteria, yeast)
  • Multicellular organisms (e.g. humans, cow, birds, trees)
• Cells


  • Capacity to intake nutrients and convert to energy
  • Ability to synthesise necessary proteins
  • Store their own genetic material
• Anton Von Leeuwenhoek first described a live cell
• The largest cell in the world is Ostrich egg
• Cell theory


  Proposed by Matthias Schleiden (1838) and Theodore Schwann (1839), further developed by Rudolf Virchow (1855)
• Key principles of cell theory

  • All living organisms are composed of cells and products of cells
  • Cell is the basic unit of life
  • All cells arise from pre-existing cells (Omnis cellula-e-cellula)
• Differences between plant and animal cells

  • Plant cells have a cellulose cell wall, large vacuoles, and plastids like chloroplasts
  • Animal cells lack a cell wall, have smaller vacuoles, and lack plastids
• Basic features of all cells

  • Plasma membrane
  • Cytosol/cytoplasm
  • Chromosomes with genes
  • Cell organelles (e.g. endoplasmic reticulum, Golgi complex, lysosomes, mitochondria, chloroplasts)
  • Ribosomes
• Animal cells contain a centrosome which helps in cell division
• Types of cells based on presence/absence of true nucleus

  • Prokaryotes (no well-developed nucleus)
  • Eukaryotes (membrane-bound nucleus)
• Prokaryotic cells


  • No well-developed nucleus, DNA in nucleoid region, cytoplasm surrounded by plasma membrane
• Eukaryotic cells


  • Membrane-bound nucleus, genetic material organised into chromosomes, membrane-bound organelles in cytoplasm
• Protoplasm


  The living content of a cell, including cytoplasm and nucleus
• Hyaloplasm/cytoplasm


  The ground substance of protoplasm, after removing nucleus and cell organelles
• Cell membrane/plasma membrane


  Composed of lipid bilayer and proteins, selectively permeable
• Singer and Nicolson (1972) proposed the fluid mosaic model of plasma membrane
• Cell wall


  • Non-living rigid structure surrounding plant and fungal cells, provides shape and protection
• Components of plant cell wall

  • Cellulose
  • Hemicellulose
  • Pectins
  • Proteins
• Middle lamella


  Layer joining adjacent plant cell walls, made of calcium and magnesium pectate
• Functions of cell wall

  • Provide shape and strength
  • Protect from damage and infection
  • Allow entry of molecules
  • Facilitate cell-cell interaction
  • Act as barrier
• Nucleus


  Most important cell organelle, directs and controls cellular activities
• Nucleus was discovered by Robert Brown in 1831
• Nucleus


  • Double-layered nuclear membrane with pores, contains nucleolus and chromatin material, filled with nucleoplasm
• Chromosomes/chromatin material


  Contain DNA that stores and transmits hereditary information
• Nucleolus


  Structure where ribosomes are formed
• Functions of nucleus

  • Control metabolic activities
  • Regulate cell cycle
  • Transmit hereditary characters
• Cytoplasm


  Site of biosynthetic and catabolic pathways, contains cytosol and cell organelles
• Types of cell organelles

  • Double-membranous (nucleus, mitochondria, chloroplasts)
  • Single-membranous (endoplasmic reticulum, Golgi bodies, lysosomes, vacuoles)
  • Non-membranous (ribosomes, cytoskeleton)
• Mitochondria


  Double-membranous organelles, called "powerhouse of the cell", site of ATP production
• Mitochondria


  • Outer membrane with specific proteins, inner membrane folded into cristae, matrix contains enzymes for Krebs cycle
• Plastids


  Double-membranous organelles found only in plant cells
• Types of plastids


  • Leucoplasts (colourless, store nutrients)
  • Chromoplasts (coloured, contain carotenoid pigments)
  • Chloroplasts (green, contain chlorophyll)
• Plastid


  Double membranous discoidal structure found only in plant cells
• Term plastid was given by Haeckel
• Shapes and size of plastids varies from plant to plant
• Types of plastids based on pigment

  • Leucoplast
  • Chromoplast
  • Chloroplast