Photosynthesis and cellular respiration

• Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to create oxygen and sugar

  
• In photosynthesis:

  • First step: absorption of light energy by chlorophyll molecules in the chloroplasts
  • Second step: conversion of light energy into chemical energy in the form of ATP and NADPH
  • Third step: use of ATP and NADPH to reduce carbon dioxide to glucose

  
• The Calvin cycle in photosynthesis makes sugar from carbon dioxide, with chemical energy (ATP and NADPH) generated by the light reactions providing the energy for sugar synthesis

  
• Cellular respiration is the process by which cells convert glucose into energy, starting with glycolysis in the cytosol, then converting pyruvate into acetyl-CoA in the mitochondria's citric acid cycle

  
• During cellular respiration, acetyl-CoA is broken down into carbon dioxide and water in the mitochondria, releasing energy used to produce ATP, the cell's energy currency

  
• Both photosynthesis and cellular respiration involve the use of glucose and oxygen as reactants, producing carbon dioxide, water, and energy (ATP) as products
• Cellular respiration has two types: aerobic (with oxygen) and anaerobic (without oxygen), both starting with glycolysis in the cytoplasm
• Aerobic cellular respiration is more efficient, yielding a total of 36 ATP, compared to anaerobic respiration which yields only 2 ATP