Biology Paper 1 (mine)

• Types of microscopes


  • Light microscope
  • Electron microscope
• Light microscope


  • First developed in the mid 17th century
  • Uses light to form an image
  • Can be used to view live specimens
  • Relatively cheap and easy to use
  • Magnification up to 2,000 times
• Resolution


  The ability to see two things as separate objects
• The high magnification and resolution of the electron microscope allows scientists to see and understand more about the subcellular structures of cells
• Cell membrane


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

  Contains the following organelles: nucleus, cell membrane, cytoplasm, mitochondria, ribosomes, chloroplasts, permanent vacuole, cell wall
• Chloroplasts

  Contain chlorophyll and are the site of photosynthesis
• Specialized cells


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


  • Has a tail to help it swim, many mitochondria in the mid-piece to provide energy, an acrosome with enzymes to break down the egg, and a large nucleus to contain DNA
• 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
• Phloem cell

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

  The spreading out of particles in a solution or gas, resulting in a net movement 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 and solute concentrations
• Importance of osmosis in animal cells

  • Ensures that the 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
• Effect of different solutions on a red blood cell

  1. Hypotonic solution: Water moves into the cell, causing it to stretch and potentially burst

  2. Isotonic solution: No net movement of water, i.e. no osmosis occurs

  3. Hypertonic solution: Water moves out of the cell, causing it to shrink and not function properly
• Osmosis is a required practical that looks at the effect of concentration of salt or sugar on the mass of plant tissue
• Examples of active transport

  • Mineral ions moving from the dilute solution in the soil into the more concentrated solution in the root hair cells of a plant
  • Glucose moving from the dilute solution in the small intestine into the more concentrated solution in the bloodstream
• Cell cycle


  1. Stage 1: Cell growth, increase in subcellular structures, and DNA replication

  2. Stage 2: Mitosis - one set of chromosomes is pulled to each end of the cell, and the nucleus and cytoplasm divide

  3. Stage 3: Cytoplasm and cell membranes divide to form two identical cells
• Importance of mitosis and the cell cycle


  Development, growth, and repair
• Specialized cells


  • Nerve cell, muscle cell, red blood cell
• Issues with stem cells include risk of viruses, rejection, and ethical concerns
• Cells


  Basic building blocks of life
• Tissues


  Group of cells with similar structure and function
• Organs


  Collections of tissues performing specific functions
• Organ systems


  Organs working together to carry out a specific function
• Organism


  The whole living thing at the top of the hierarchy
• Digestion


  1. Food broken down into smaller soluble molecules that can be absorbed

  2. Mouth mechanically breaks down food

  3. Saliva glands produce saliva

  4. Esophagus transports food to stomach

  5. Stomach mixes food with hydrochloric acid

  6. Small intestine further digests and absorbs food

  7. Large intestine absorbs water from undigested material

  8. Rectum stores feces

  9. Anus excretes feces
• Small intestine adaptations


  • Large surface area (villi and microvilli)
  • Good blood supply (capillaries)
  • Short diffusion distance
• Temperature increases


  Enzyme activity increases (up to optimum), then decreases (denaturation)
• pH changes from enzyme's optimum

  Enzyme activity decreases (denaturation)
• Bile


  Alkaline liquid produced in liver, stored in gallbladder, helps digest fats by emulsification
• Enzyme production and site of action

  • Amylase: produced in saliva glands and pancreas, acts in mouth and small intestine
  • Protease: produced in stomach and small intestine, acts in stomach and small intestine
  • Lipase: produced in pancreas, acts in small intestine
• Three enzymes are produced in the pancreas
• The site of action for all three enzymes is the small intestines
• Amylase


  Also produced in the salivary glands, site of action is the mouth
• Protease


  Produced in the stomach and small intestines, site of action is the stomach
• Components of blood


  • Plasma
  • Red blood cells
  • White blood cells
  • Platelets