BIOLOGY PAPER 1

• Sub-cellular structures in plant and animal cells

  • Nucleus - controls cell activities
  • Cell membrane - controls what comes in and out of the cell
  • Cytoplasm - where chemical reactions take place
  • Mitochondria - where aerobic respiration takes place: releases energy
  • Ribosomes - proteins synthesis
• Sub-cellular structures found in plant cells and not animals

  • Chloroplasts - contain chlorophyll: where photosynthesis takes place
  • Vacuole - contains cell sap: controls water concentration
  • Cell wall - strengthens cells contains cellulose
• Prokaryotic cell


  No nucleus, contains plasmids, smaller
• Eukaryotic cell


  Contains nucleus, only plant cell has cell wall
• Both prokaryotic and eukaryotic cells have a cell membrane and cytoplasm
• Specialised animal cells


  • Red blood cell
  • Sperm cell
  • White blood cell
  • Nerve cell
• Specialised plant cells


  • Root hair cell
  • Xylem
  • Phloem
  • Palisade cell
• Total magnification of a microscope

  Eyepiece lens x Objective lens magnifying power
• Magnification equation


  Magnification = image size ÷ actual size
• Resolution


  The ability to distinguish between two separate points that are very close together
• Electron microscopes


  • Higher resolution and higher magnification than light microscopes
• Staining tissue sample


  To see the organelles
• Thin specimen


  To see a single layer of cells / so light can pass through
• Cover slip angle


  To avoid air bubbles
• Starting objective lens


  Lowest power objective lens - it is easier to locate the specimen, then you can increase the magnification to see more detail
• Improving image clarity


  Turn the focus knob
• Increasing image size


  Use a higher power objective lens
• Cell differentiation


  When a cell becomes specialised
• Role of sperm cells


  Swim to and fertilise the egg
• Sperm cell adaptations


  • Have a tail - for swimming
  • Contain a lot of mitochondria - to release energy
• Role of muscle cells

  To contract
• Muscle cell adaptations


  • Contain a lot of mitochondria - to release energy
• Role of nerve cells


  Transport electrical signals around the body
• Nerve cell adaptations


  • Long shape - cover long distances
  • Insulated - to prevent electrical signals escaping
• Chromosomes


  Made of DNA
• Importance of mitosis


  For growth and replacement of damaged cells
• Mitosis


  1. cells and organelles grow

  2. DNA replicates

  3. chromosomes line up along centre of cell

  4. they are pulled to opposite sides of cells

  5. nucleus divides

  6. cytoplasm and cell membrane divides

  7. forms two genetically identical daughter cells

  8. that contain the same DNA
• Stem cell


  An unspecialised cell that can differentiate into different types of cells
• Types of animal stem cells

  • Adult stem cells
  • Embryotic stem cells
• Where adult stem cells are produced

  Bone marrow
• Conditions stem cells can treat

  • Diabetes
  • Paralysis
• Where meristems are found

  Growing regions of plants
• Advantage of embryotic stem cells

  They can differentiate into any type of cell
• Concern with embryotic stem cells


  Ending a potential humans life
• Diffusion


  The movement of particles from a high concentration to a low concentration
• Factors affecting rate of diffusion

  • Surface area
  • Thickness of surface (diffusion pathway)
  • Concentration gradient
  • Temperature
• Substances that diffuse in and out of blood in lungs

  • Oxygen
  • Carbon dioxide
• Alveoli adaptations in mammal lungs

  • Folded shape = large surface area
  • Capillaries one cell thick - thin surface for short diffusion pathway
  • Vast network of capillaries - to provide concentration gradient
  • Well-ventilated = steep concentration gradient
• Root hair cell adaptations in plants

  • Long (elongated) thin shape = large surface area
  • Thin walls = thin surface
  • Large vacuole = maintains water concentration
  • Mitochondria = releases energy for active transport of minerals
• Villi adaptations in small intestine

  • Folded shape = large surface area
  • Capillaries one cell thick - thin surface for short diffusion pathway
  • Vast network of capillaries = concentration gradient
  • Mitochondria = releases energy for active transport of minerals