Biology P1

• Nucleus


  Contains genetic material and controls the activities of the cell
• Cytoplasm


  Gel-like substance where most of the chemical reactions happen. Contains enzymes that control these chemical reactions
• Cell membrane


  Holds the cell together and controls what goes in and out
• Mitochondria


  Where most of the reactions for aerobic respiration occur. Respiration transfers energy that the cell needs to work
• Ribosomes


  Where protein synthesis takes place - where proteins are made in the cell
• Cell walls


  Made of cellulose and they support and strengthen the cell
• Vacuole


  Contains cell sap and helps maintain the shape of the cell
• Chloroplasts


  Where photosynthesis occurs, which makes food for the plant. They contain chlorophyll - a green pigment - which absorbs light needed for photosynthesis
• What bacterial cells contain


  • Cytoplasm
  • Cell membrane
  • Cell wall
  • Flagella
  • Ribosomes
  • Mitochondria
  • Slime capsule
  • Plasmids
  • Single circular strand of DNA
• Bacterial cells do not contain a nucleus
• Magnification


  Image size divided by actual size
• Differentiation


  The process by which a cell changes to become specialised for its job
• Undifferentiated cells


  Stem cells
• Sperm cells


  • Specialised for reproduction
  • Have a flagella and streamlined head to help it swim towards the egg
  • Lots of mitochondria to provide energy
  • Carry enzymes in head to help digest through egg cell membranes
• Nerve cells


  • Specialised for rapid signalling
  • Long to cover more distance
  • Branched connections at ends to connect to other nerve cells and form a network
• Muscle cells


  • Specialised for contraction
  • Long to have space to contract
  • Contain lots of mitochondria to generate energy for contraction
• Root hair cells


  • Specialised for absorbing water and minerals
  • Grow into long hairs that stick out into the soil
  • Have a large surface area for absorbing water and mineral ions
• Chromosomes


  Coiled up lengths of DNA molecules that are found in the nuclei
• Mitosis


  Used by multicellular organisms to grow or replace cells that have been damaged
• Stem cells


  Undifferentiated cells that divide to produce lots more undifferentiated cells, then differentiate into different types of cell
• Where stem cells are found


  • Early human embryos
  • Bone marrow of adults
• Embryonic stem cells


  • Used to replace faulty cells in sick people
  • Used to replace faulty blood cells
• Diffusion


  Movement of particles from an area of high concentration to an area of low concentration
• Substances that can diffuse through cell membranes


  • Glucose
  • Water
  • Oxygen
  • Amino acids
• Substances that can't diffuse through cell membranes


  • Protein
  • Starch
• Osmosis


  Passive movement of water molecules through a partially permeable cell membrane from an area of high water concentration to an area of low water concentration
• Active transport


  Uses energy and goes against the concentration gradient, unlike diffusion
• Adaptations of exchange surfaces


  • Large surface area
  • Lots of blood vessels
  • Thin membrane
  • Often ventilated
• Adaptations of villi in small intestine


  • Single layer of surface cells
  • Very good blood supply to assist quick absorption
• Adaptations of leaves to maximise carbon dioxide intake


  • Exchange surface covered in stomata
  • Flattened shape increases exchange surface area
  • Cell walls act as exchange surface
  • Air spaces increase exchange surface area
• Factors affecting diffusion rate


  • Concentration gradient
  • Temperature
  • Surface area
  • Diffusion distance
• Active transport


  • Plants - root hairs absorbing minerals and water
  • Animals - glucose taken in from gut and kidney tubules
• Adaptations of alveoli in lungs


  • Enormous surface area
  • Moist lining for dissolving gases
  • Very thin walls
  • Good blood supply
• Fish respiration


  Water enters mouth and exits through gills, allowing oxygen to diffuse into blood and carbon dioxide to diffuse out
• Adaptations of fish gills


  • Gill filaments create large surface area
  • Lamellae increase surface area further
  • Lamellae have blood capillaries to speed up diffusion
  • Lamellae have thin surface layer to minimise diffusion distance
  • Blood and water flow in opposite directions to maintain concentration gradient
• Preparing a microscope slide


  1. Add drop of water

  2. Cut and peel off onion epidermal tissue

  3. Place tissue in water

  4. Add iodine stain

  5. Place cover slip
• Using a light microscope


  1. Clip slide onto stage

  2. Select lowest-powered objective lens

  3. Use coarse adjustment to focus

  4. Use fine adjustment to get clear image
• Drawing microscope observations


  1. Draw with pencil, taking up at least half the space

  2. Use clear, unbroken lines with no colouring or shading

  3. Draw subcellular structures in proportion

  4. Include title and magnification
• Binary fission


  1. DNA and plasmids replicate

  2. Cell gets bigger and DNA moves to opposite poles

  3. Cytoplasm divides and new cell walls form

  4. Two daughter cells produced, each with one copy of DNA
• Binary fission


  Type of simple cell division used by prokaryotic cells to reproduce and split into two