Biology 1,2,3

• Light microscope


  Developed in the mid 17th century, uses light to form an image, can view live specimens, relatively cheap and easy to use, can magnify up to 2,000 times, has a resolution of around 200 nanometers
• Electron microscope


  Developed in the 1930s, uses electrons to form an image, can only view dead specimens, very expensive and has many conditions, can magnify up to 2 million times, has a resolution of 0.2 nanometers
• The electron microscope is much better than the light microscope in terms of magnification and resolution
• Nucleus


  Controls the cell's activities and contains genetic material (DNA)
• Cell membrane


  Responsible for controlling the passage of substances in and out of the cell
• Cytoplasm


  Liquid gel that fills the entire cell and is where chemical reactions occur
• Mitochondrion


  Where aerobic respiration occurs, releasing energy for the cell
• Ribosome


  Site of protein synthesis
• Parts of an animal cell


  • Nucleus
  • Cell membrane
  • Cytoplasm
  • Mitochondrion
  • Ribosome
• Chloroplast


  Contains chlorophyll and is responsible for photosynthesis
• Permanent vacuole


  Filled with cell sap, helps keep the cell rigid
• Cell wall


  Made of cellulose, strengthens and supports the plant cell
• Parts of a plant cell


  • Nucleus
  • Cell membrane
  • Cytoplasm
  • Mitochondrion
  • Ribosome
  • Chloroplast
  • Permanent vacuole
  • Cell wall
• Eukaryotic cells


  Animal, plant, fungi and protista cells that have a cell membrane, cytoplasm and genetic material enclosed in a nucleus
• Prokaryotic cells


  Bacterial cells that have a cell membrane and cytoplasm but their genetic material is not enclosed in a nucleus
• Differences between eukaryotic and prokaryotic cells


  • Eukaryotes have a nucleus, prokaryotes do not
  • Eukaryotes may have chloroplasts and mitochondria, prokaryotes do not
  • Eukaryotes have a cell wall that is sometimes made of cellulose, prokaryotes have a cell wall made of different materials
• Specialised cells


  Cells that have developed different subcellular structures to carry out a particular function
• Sperm cell


  Has a tail to swim, a midpiece with many mitochondria to provide energy, an acrosome with enzymes to break down the egg, and a large nucleus to contain DNA
• Muscle cell


  Has many mitochondria to release energy for contraction, special proteins that cause contraction by sliding, and can store glycogen
• Nerve cell


  Has a long axon to carry electrical impulses, dendrites to connect to other nerve cells, and nerve endings that release chemical messengers
• Root hair cell


  Has a large surface area for absorption, a large permanent vacuole to speed up osmosis, and many mitochondria for active transport of mineral ions
• Xylem cell


  Forms long hollow tubes with spirals of lignin to allow easy movement of water and minerals up the plant
• Phloem cell


  Has sieve plates to allow easy movement of dissolved food up and down the plant, and companion cells that provide the energy for this
• Diffusion


  The spreading out of particles in a solution or gas from an area of higher concentration to an area of lower concentration
• Factors affecting rate of diffusion


  • Temperature (higher temperature increases rate)
  • Concentration gradient (steeper gradient increases rate)
  • Surface area (larger surface area increases rate)
• Osmosis


  The diffusion of water molecules from a dilute solution to a more concentrated solution through a partially permeable membrane
• Osmosis is important in animal cells to maintain the right internal environment
• Left side of the membrane

  Has more water molecules
• Right side of the membrane


  Has less water molecules and more sucrose or solute molecules, therefore it is the concentrated side
• Osmosis


  1. Occurs down a concentration gradient or from a dilute solution to a more concentrated solution

  2. Net movement of water is from the left side to the right side

  3. Water concentration will eventually be equal on both sides

  4. Water molecules will continue to move back and forth across the partially permeable membrane but there's no further net movement of water, the water is balanced on both sides
• Importance of osmosis in animal cells


  • Ensures solutes like glucose and salts are at the right concentration inside the cell
  • The internal environment needs to be kept just right for the cell to work
  • The difference in concentration between the cell's internal environment and the external solution will determine how much osmosis occurs
• What happens when a red blood cell is put into a hypotonic solution

  Water moves into the cell, stretching it, and the cell may even burst if a lot of water moves in, killing the cell
• What happens when a red blood cell is put into an isotonic solution


  Nothing happens, as the two solutions are the same, there is no net movement of water, no osmosis occurs
• What happens when a red blood cell is put into a hypertonic solution

  Water moves out of the red blood cell and into the beaker, as the red blood cell solution is more diluted, the cell will shrink and won't function properly
• Required practical A by osmosis looks at the effect of concentration of salt or sugar on the mass of plant tissue
• Active transport


  Substances move from a low concentration to a high concentration, against the concentration gradient
• Active transport


  • Requires energy from respiration
  • Takes place across a partially permeable membrane, just like osmosis
• Active transport in plant roots


  Mineral ions move from the dilute solution in the soil into the more concentrated solution in the root hair cells, against the concentration gradient, requiring energy from respiration
• Active transport in the small intestines


  Glucose is moved from the dilute solution outside the blood vessels to the more concentrated solution inside the blood vessels, against the concentration gradient, using active transport
• Nucleus


  Contains chromosomes made up of DNA, which codes for genes