Biology

• Types of cells


  • Animal cells
  • Plant cells
  • Bacterial cells
• Animal cell


  • Has nucleus containing genetic material
  • Has mitochondria for aerobic respiration
  • Has cytoplasm where chemical reactions take place
  • Has ribosomes for protein synthesis
  • Has cell membrane controlling what goes in and out
• Plant cell


  • Has cell wall made of cellulose for strength
  • Has chloroplasts for photosynthesis
  • Has permanent vacuole containing cell sap
• Bacterial cell


  • Has single strand of DNA called plasmids instead of nucleus
  • Lacks chloroplasts and mitochondria
  • Has cell membrane, cell wall and cytoplasm
• Prokaryotes


  Type of organism
• Eukaryotes


  Type of organism
• Microscopy


  Using a microscope to see things that can't be seen with the naked eye, like sub-cellular structures
• Types of microscopes


  • Light microscopes
  • Electron microscopes
• Light microscopes


  Use light and lenses to magnify images, can see individual cells
• Electron microscopes


  Use electrons instead of light to form images, have higher magnification and resolution to see more detail like mitochondria
• Magnification formula


  Image size divided by real size
• Microscope experiment steps


  1. Get microscope slide and add water

  2. Cut onion, peel epidermal tissue

  3. Place tissue in water on slide

  4. Add iodine stain

  5. Place cover slip

  6. Use microscope
• Cell differentiation


  Process where a cell changes to become specialised for its job, developing different sub-cellular structures
• Examples of specialised cells and functions

  • Sperm cell - reproduction
  • Nerve cell - carry electrical signals
  • Muscle cell - contraction
  • Root hair cell - absorb water and minerals
  • Phloem and xylem cells - transport food and water in plants
• Cell division


  Crucial process for creating daughter cells from parent cells
• Stem cells


  Undifferentiated cells that can divide and change into different cell types, found in plant meristems, bone marrow, human embryos
• Chromosomes


  Coiled DNA molecules containing genetic material, one set has 23 pairs
• Cell cycle


  Series of events a cell undergoes as it divides and duplicates DNA, including cell growth, combining compounds, and mitosis or meiosis
• Mitosis


  Chromosomes line up at cell centre, cell fibres pull them apart, membranes form around new nuclei, cytoplasm and cell membrane divide to create two identical daughter cells
• Diffusion


  Spreading out of particles from an area of higher concentration to lower concentration
• Cell membranes and diffusion

  Cell membranes only allow small dissolved substances to diffuse through, not larger substances like proteins
• Osmosis


  Movement of water across a partially permeable membrane from an area of higher water concentration to lower water concentration
• Exchange surfaces


  Cells can use diffusion to take in substances they need and get rid of waste, like oxygen and carbon dioxide during gas exchange
• Multicellular organisms have a small surface area compared to their volume, so not enough substances can diffuse from the outside to supply their volume</b>
• Reasons why exchange surfaces are adapted

  • Have a thin membrane so substances have a short distance to diffuse
  • Have a large surface area so lots of substances can diffuse
• Active transport


  Transportation of molecules that requires the use of energy, like root hair cells transporting water and minerals against a concentration gradient
• Active transport is important for growth but requires energy from respiration to work
• Active transport can also be used in the gut to transport nutrients from a lower concentration in the gut to a higher concentration in the blood
• The human body is adapted for effective substance exchange, like in the lungs where gas exchange occurs in the alveoli which have a large surface area, moist lining, thin walls and good blood supply
• Plants are also adapted for effective substance exchange, with the leaf structure allowing carbon dioxide to diffuse in and oxygen and water vapour to diffuse out through the stomata, which are controlled by guard cells
• Villi


  Small projections in the small intestine that have a large surface area to absorb digested food quickly into the blood
• Cells


  Building blocks that make up all living organisms
• Cell differentiation


  The process of cells being specialised
• Tissue


  A group of similar cells that work together to carry a particular function
• Types of tissues in mammals

  • Muscular Tissue
  • Glandular Tissue
  • Epithelial tissue
• Organ


  A group of different tissues that work together to perform a particular function
• Tissues that make up the stomach

  • Muscular Tissue
  • Glandular Tissue
  • Epithelial tissue
• Organ system


  A group of organs working together to perform a particular function
• Organs that make up the digestive system

  • Glands
  • Stomach
  • Liver
  • Small intestine
  • Large intestine
• Enzymes


  Catalysts produced by living things that increase the speed of a reaction without being changed or used up