Biology

• This video is made from the specifications so I've taken all the spec points for the first unit the first topic and given the information about those
• Cell types


  • Eukaryotes (animals and plants)
  • Prokaryotes (bacteria)
• Animal cell


  • Nucleus (controls cell activities, contains DNA)
  • Cytoplasm (where chemical reactions take place)
  • Cell membrane (controls what goes in and out, partially permeable)
• Plant cell


  • Nucleus (controls cell activities, contains DNA)
  • Cytoplasm (where chemical reactions take place)
  • Cell membrane (controls what goes in and out, partially permeable)
  • Cell wall (for strength and support, made of cellulose)
  • Sap vacuole (contains cell sap, a sugary solution)
  • Chloroplast (contains chlorophyll to absorb sunlight for photosynthesis)
• Prokaryotic cell

  • No nucleus
  • No mitochondria
  • No subcellular structures with membranes
  • Circular DNA (controls cell activities, makes proteins)
  • Plasmid (small ring of DNA with a few genes)
• Approximate sizes: Animal cell 10 micrometers, Plant cell 50 micrometers, Prokaryotic cell 5 micrometers
• Cell differentiation


  1. Undifferentiated cells (e.g. sperm and egg)

  2. Differentiate into specialized cells (e.g. nerve, muscle, sperm, xylem, phloem, root hair)
• Nerve cell


  • Cell body (contains cytoplasm)
  • Dendrites (connect to other nerve cells)
  • Axon (long projection that carries impulses)
  • Insulating sheath (speeds up electrical impulse)
• Sperm cell

  • Mid piece (contains mitochondria for energy)
  • Tail (for swimming)
  • Acrosome (contains enzymes to penetrate egg cell)
• Muscle cell

  • Fibers that can shorten for contraction
  • Mitochondria (provide energy)
  • Glycogen (stored energy)
• Xylem cell


  • No end plates (allows water flow)
  • No cytoplasm (dead tissue)
  • Rings of lignin (support and prevent collapse)
• Phloem cell


  • Very little cytoplasm (allows more solution flow)
  • End plates with pores (allow dissolved substances through)
  • Companion cells (provide energy for transport)
• Root hair cell


  • Large surface area
  • Many mitochondria (provide energy for active transport)
• Microscopes have developed from simple to light to electron microscopes, with higher magnification and resolving power
• Millimeter

  One thousandth of a meter
• Micrometer


  One thousandth of a millimeter
• Nanometer


  One thousandth of a micrometer
• Calculating magnification


  Magnification = Size of image / Size of real object
• Culturing microorganisms


  1. Bacteria divide by binary fission

  2. Provide nutrients like glucose and amino acids

  3. Incubate at 25°C to allow growth
• Growing uncontaminated cultures


  1. Sterilize equipment and media

  2. Use inoculating loop to transfer bacteria to agar gel

  3. Seal petri dish to prevent contamination

  4. Incubate at 25°C
• Testing antibiotics/antiseptics


  1. Place antibiotic/antiseptic discs on agar with bacteria

  2. Measure area of dead bacteria around discs

  3. Control variables: disc area, concentration, volume
• Cell cycle


  1. Stage 1: Cell growth, DNA replication

  2. Stage 2: Mitosis - chromosomes line up, divide, form two cells

  3. Stage 3: Cytoplasm and cell membrane divide to form two genetically identical cells
• Embryonic stem cells


  • Undifferentiated cells from early embryo
  • Can differentiate into any cell type
• Cell growth and division

  1. Cell grows and increases number of subcellular structures

  2. DNA replicates to form two copies of each chromosome

  3. Chromosomes line up along center and are pulled to each end of cell

  4. Cytoplasm and cell membranes divide to form two genetically identical cells
• Mitosis


  The process of cell division described above
• Types of stem cells

  • Embryonic stem cells
  • Adult stem cells
  • Plant stem cells (meristem tissue)
• Embryonic stem cells


  • Undifferentiated
  • Can be cloned
  • Can differentiate into most other cell types
• Adult stem cells


  • Found in bone marrow
  • Can differentiate into many cell types, mainly blood cells
• Plant stem cells


  • Found in meristem tissue in root and shoot tips
  • Can differentiate into any plant cell
• Therapeutic cloning


  1. Patient body cell nucleus removed and inserted into empty human egg cell

  2. Cloned to produce stem cells

  3. Stem cells differentiated to make specialized cells/tissues for treatment
• Diffusion


  Spreading out of particles in a solution or gas, with net movement from higher to lower concentration
• Factors affecting rate of diffusion

  • Concentration gradient
  • Temperature
  • Surface area
• Active transport


  Movement of particles from lower to higher concentration, requires energy
• Examples of diffusion in living things

  • Oxygen diffusing into cells from blood
  • Carbon dioxide diffusing out of cells into blood
  • Urea diffusing out of cells
• Examples of active transport in living things

  • Sugar absorption in small intestine
  • Mineral ion absorption in root hair cells
• Surface area to volume ratio

  • Measure of how much surface area an organism has relative to its volume
  • Smaller organisms have higher ratio, allowing sufficient transport of molecules
• Adaptations for exchange systems in larger organisms

  • Villi and microvilli in small intestine to increase surface area
  • Thin walls for short diffusion distance
  • Many mitochondria for active transport energy
  • Good blood supply to maintain concentration gradient
• Adaptations of alveoli in lungs


  • Large surface area
  • Thin walls for short diffusion distance
  • Good blood supply to maintain concentration gradient
  • Ventilation to maintain oxygen concentration
• Adaptations of leaves


  • Flat and thin to provide large surface area
  • Air spaces between cells to increase diffusion rate
  • Stomata that can open/close to regulate gas exchange
• Adaptations of gills in fish

  • Many gill filaments for large surface area
  • Thin capillary walls for short diffusion distance
  • Good blood supply to maintain concentration gradient
  • Fresh water flowing over to maintain oxygen concentration