Unit 4: Cellular Respiration and Photosynthesis

• Key Vocabulary


  • autotroph
  • cellular respiration
  • consumer
  • energy
  • food
  • glucose
  • heterotroph
  • photosynthesis
  • producer
• Autotroph


  An organism that produces its own food, like plants that photosynthesize with light, carbon dioxide, and water to produce glucose and oxygen (occurs in the chloroplast)
• Cellular respiration


  A process that converts glucose and oxygen into carbon dioxide, water, and ATP for energy (that is used in metabolic reactions), occurs inside the mitochondria
• Consumer


  An organism that feeds on other organisms (either autotrophs or heterotrophs) as a source of food to make energy
• Food


  Organic compounds or molecules that contain energy in their chemical bonds
• Heterotroph


  Organisms unable to produce their own food, so they consume other autotrophs and/or heterotrophs as food to make energy
• Glucose


  A simple sugar (carbohydrate) produced during photosynthesis and used in cellular respiration as it contains energy within its chemical bonds
• Photosynthesis


  A process that occurs in chloroplasts that convert carbon dioxide, water molecules, and light energy into glucose and oxygen. It is a process that produces food for plants
• Producer


  Organisms that make their own food for themselves and other organisms
• Living things need energy to do work. Without it, no organism would be able to carry out the biochemical reactions and other metabolic processes taking place within our bodies. They may need it for digestion, building new molecules, and cell transport.
• How autotrophs obtain energy

  1. Capture light energy in chlorophyll

  2. Convert carbon dioxide and water into glucose (food) and oxygen (byproduct)

  3. Use glucose and oxygen during cellular respiration in the mitochondria to get ATP energy for metabolic processes
• How heterotrophs obtain energy

  1. Consume autotrophs or other heterotrophs to obtain food

  2. Use the glucose from the food and oxygen from the air during cellular respiration to produce ATP energy for metabolic processes
• Photosynthesis and cellular respiration are closely related. Their products and reactants are the same, except their roles are the opposite (and there is the addition of a condition (light) and a new product (ATP)). Hence, the two processes produce molecules that carry energy, which are used for metabolic reactions to keep the organism alive.
• Living things need both glucose and ATP because they are both energy-carrying molecules. Glucose is used for storage and transportation as it is a highly concentrated but stable form of energy, which is transported through the bloodstream to a million cells. However, glucose has a high concentration of energy that is too much for metabolic processes. So, ATP is used as it contains the right amount of energy required for metabolic processes in the body.
• How living things recycle oxygen in Earth's atmosphere

  1. Autotrophs use carbon dioxide and water molecules with light energy to produce glucose and oxygen by photosynthesis

  2. Organisms use the oxygen in the atmosphere during cellular respiration, converting glucose and oxygen into carbon dioxide, water, and ATP energy

  3. The carbon dioxide produced would be used by autotrophs again during photosynthesis to release oxygen
• Plants and other photosynthetic autotrophs contain a green pigment called chlorophyll that captures sunlight. This chlorophyll is usually found in a chloroplast. The chlorophyll absorbs the light energy(blue and red wavelengths) and converts it into chemical energy during the light-dependent reaction.
• How light energy changes to chemical energy during photosynthesis

  1. Light energy passes inward from the pigment to the reaction center until it reaches P680 in photosystem II

  2. The electron moves into the excited state, reaching a high energy level, allowing water to be split and releasing oxygen gas

  3. ATP would be produced during the first stage of photosynthesis, which is then used during the second stage of photosynthesis to make glucose, which stores the chemical energy in itself
• Chemosynthesis


  A process used by some producers living in places that do not receive sunlight, where they produce food using chemical energy produced by the oxidation of inorganic molecules, without the use of sunlight
• Autotroph


  Organism that makes its own food
• Cellular respiration


  Process in which cells break down glucose and make ATP for energy
• Consumer


  Organism that consumes other organisms for food
• Energy


  Ability to do work
• Heterotroph


  Organism that gets food by consuming other organisms
• Photosynthesis


  Process of using the energy in sunlight to make food (glucose)
• Producer


  Organism that produces food for itself and other organisms