Biology

• Cells


  The basic unit of life that can be found in every living thing, including humans, animals, plants and bacteria
• Cells


  • Small in structure, 0.1 to 5.0 μm in diameter for prokaryotic cells, 10 to 100 μm in diameter for eukaryotic cells
  • Have general structures that allow them to be self-regulating, such as producing energy, movement, removing wastes etc.
• Unicellular organism


  Living things that are made of a single cell, such as bacteria
• Multicellular organism


  More complex organisms like humans, animals and plants
• All known living things are made up of one or more cells
• All living cells arise from pre-existing cells by division
• The cell is the building block of structure and function in all living organisms
• The activity of an organism depends on the total activity of independent cells
• Cells are the site of all chemical reaction of life (metabolism and energy flow)
• Cells contain hereditary material (DNA), the blueprint for their cell growth, development and behavior
• All cells are basically the same in chemical composition in organisms of similar species
• Prokaryotes


  Earliest organisms on earth, mostly unicellular, lack well-defined nuclei and membrane-bound organelles, have a single circular chromosome, classified into Bacteria and Archaea
• Eukaryotes


  More complex and evolved organisms, can be unicellular (algae, protozoa) or multicellular (animals, plants, fungi), have a nucleus wrapped in a nuclear membrane and membrane-bound organelles
• Similarities between prokaryotes and eukaryotes


  • Ribosome
  • DNA
  • RNA
  • Cytoplasm
• Differences between prokaryotes and eukaryotes

  • Circular DNA (prokaryotes) vs Complex and extensive DNA (eukaryotes)
  • No nucleus (prokaryotes) vs Have nucleus (eukaryotes)
  • Mostly unicellular (prokaryotes) vs Can be uni- or multicellular (eukaryotes)
  • All have cell wall (prokaryotes) vs Some do contain cell wall (eukaryotes)
  • Few organelles (prokaryotes) vs Have membrane bound organelles (eukaryotes)
  • Small in size (prokaryotes) vs Larger in size (eukaryotes)

  
• Similarities between plant and animal cells

  • Mitochondrion
  • Golgi apparatus
  • Rough and smooth endoplasmic reticulum
  • Nucleus
  • Cytoplasm
  • Ribosomes

  
• Differences between plant and animal cells

  • Cell wall (plants) vs No cell wall (animals)
  • Large vacuole (plants) vs Small or no vacuole (animals)
  • Chloroplasts (plants) vs No chloroplasts (animals)
  • Flagella only in gametes (plants) vs Flagella (animals)

  
• Theoretically it is possible to build a living organism from cells
• Applications of prokaryotic cells


  • Cleaning up oil spills
  • Decompose organic matter into sludge
  • Produce vitamins, antibiotics, hormones (e.g. insulin)
  • Amplify DNA, cloning and genetic manipulation
• Applications of eukaryotic cells


  • Mammalian cell biology - DNA replication, gene expression, cell division etc.
  • Drug discovery and screening
  • Transgenic crop plants - make corn resistant to specific insect pest
  • Transgenic animals - production of pharmaceutically important protein
• The seven characteristics of life are: cells and organisation, metabolism, responsiveness and movement, growth and development, reproduction, homeostasis, and evolution
• Levels of organisation in the human body


  • Atoms and molecules
  • Cells
  • Tissues
  • Organs
  • Organ systems
  • Organism
• Types of stem cells

  • Totipotent stem cells
  • Pluripotent stem cells
  • Multipotent stem cells
• Examples of cells adapted to their function


  • Muscle cells with myofilaments to contract and relax
  • Nerve cells with axons and dendrites to produce and move nerve impulses
  • Red blood cells with biconcave shape and haemoglobin to carry oxygen
  • Intestinal epithelial cells with microvilli to increase surface area for nutrient absorption
• My Healthy Plate


  Recommended diet for average Singaporean to maintain a balanced diet
• Tim adjusted his diet in order to lose weight
• Alan, Marilyn and her friends are aspiring athletes wanting to achieve their goals in weightlifting and marathon running respectively
• Adhesion


  The attraction between unlike molecules or surfaces
• Cohesion


  The attraction between like molecules or surfaces
• Density


  The mass per unit volume of a substance
• Hydrophobic


  Having a tendency to avoid or repel water
• Hydrophilic


  Having a tendency to attract or be attracted to water
• Inter-molecular


  Occurring between molecules
• High specific heat capacity

  The amount of heat required to raise the temperature of a substance by one degree
• Intra-molecular


  Occurring within a molecule
• Non-polar


  Having no permanent electric dipole moment
• Polar


  Having a permanent electric dipole moment
• Solvent


  A liquid that dissolves a solute, forming a solution
• Solutes


  A substance dissolved in a solvent to form a solution
• Surface tension


  The cohesive force between the surface molecules of a liquid that causes the surface to behave like an elastic sheet