biology

• Biology


  Study of living organisms
• Respiration


  The process of producing energy inside the body, just like burning of food to convert chemical energy inside the food to heat energy
• Respiration


  1. Food + oxygen ~> carbon dioxide + water + energy

  2. Carbohydrate + oxygen ~> carbon dioxide + water + energy

  3. Glucose + oxygen ~> carbon dioxide + water + energy
• Nutrition


  • Animals are consumers, get nutrition by feeding
  • Plants are producers, get nutrition by the process called photosynthesis
• Photosynthesis


  The process that the plants to make food on its own
• Photosynthesis


  Carbon dioxide + water + sunlight ~> glucose + oxygen
• Photosynthesis is exactly the reverse of respiration
• Photosynthesis is the process to make food, can only take place in plants
• Respiration is the process to use food to produce energy, takes place in all organisms
• Photosynthesis mainly takes place in the leaf
• After producing glucose, the plant uses up glucose to produce energy by respiration
• Excess glucose will be stored in the form of starch
• In winter, the plants have no leaf, no Photosynthesis, the plant will use up the stored starch to produce energy
• Photosynthesis takes place inside the leaf to make glucose
• Excess glucose is transported to storage organ to convert glucose to starch
• Essential conditions for photosynthesis to take place

  • Sunlight
  • Carbon dioxide
  • Chlorophyll
• Animal cell


  • Nucleus
  • Cell membrane
  • Cytoplasm
  • Mitochondria
  • Ribosomes
• Plant cell


  • Cell wall
  • Chloroplast
  • Vacuole
• Compared with animal cells, plant cell has 3 extra organelles: cell wall, chloroplast, vacuole</b>
• Different cells have different shapes because different cells have different functions, and the shape of the cell must be well adapted to carry out specific function
• Levels of organization in multicellular organism

  • Cell
  • Tissue
  • Organ
  • System
  • Organism
• Photosynthesis


  The process that the plant uses to make food
• Photosynthesis


  Carbon dioxide + water + Sunlight -> glucose + oxygen
• Where does water come from?

  Absorbed by root and transported to leaf
• Where does carbon dioxide come from?

  There are some small holes in the lower part of the leaf called stomata, for gas exchange
• Where does photosynthesis take place?

  In the chloroplast, in the leaf
• Most of the cells inside the leaf

  Have many chloroplasts for photosynthesis
• Functions of different plant organs

  • Root: Absorb water and minerals, hold tightly in soil for support
  • Stem: Transport water from root to leaf, support plant
  • Leaf: Photosynthesis, nutrition
  • Flowers: Reproduction, produce offspring
• Essential conditions for photosynthesis

  • Sunlight
  • Carbon dioxide
  • Chlorophyll (green pigment in chloroplast that absorbs sunlight)
• Experiments to prove essential conditions for photosynthesis

  1. Sunlight

  2. Carbon dioxide

  3. Chlorophyll
• How to prove photosynthesis has taken place

  Test for starch - if photosynthesis has occurred, leaf will make glucose, excess glucose will be converted to starch for storage
• Starch test procedure


  Destarch the plant

  2. Cover part of leaf with black strip/foil

  3. Put plant in sunlight

  4. Test leaf for starch using iodine solution
• Sunlight is essential for photosynthesis
• Starch is present = blue-black with iodine, starch is absent = brown with iodine
• Experiment to prove sunlight is essential

  Destarch the plant

  2. Cover part of leaf

  3. Put plant in sunlight

  4. Test leaf for starch
• Experiment to prove carbon dioxide is essential

  Destarch the plant

  2. Enclose part of leaf in flask with KOH to absorb CO2

  3. Put plant in sunlight

  4. Test leaf for starch
• Experiment to prove chlorophyll is essential

  Use variegated leaf, test green and yellow areas for starch
• Why do different cells have different shapes?

  Because they have different functions, the cell shape must be adapted to carry out its function
• Adaptive features of the leaf for photosynthesis

  • Broad and thin to provide large surface area to capture sunlight

  Waxy upper epidermis to prevent water loss

  Palisade cells to absorb sunlight

  Spongy layer with stomata for gas exchange
• Function of stomata


  For gas exchange, CO2 diffuses in and oxygen diffuses out