Lesson 3

• • Bacteria are used to produce yogurt, sour cream, pepperoni, and cheese
• • Both carbon monoxide and cyanide kill by disrupting cellular respiration
• • All the energy in all the food you eat can be traced back to sunlight
• • If you exercise too hard, your muscles shut down from a lack of oxygen
• • The ingredients for photosynthesis are carbon dioxide and water.
• • CO2 is obtained from the air by a plant’s leaves
• • H2O is obtained from the damp soil by a plant’s roots
• • Chloroplasts rearrange the atoms of these ingredients to produce sugars (glucose) and other organic molecules
• • Oxygen gas is a by-product of photosynthesis
• • Both plants and animals perform cellular respiration
• • Cellular respiration is a chemical process that harvests energy from organic molecules
• • Cellular respiration occurs in mitochondria
• • The waste products of cellular respiration, CO2 and H2O, are used in photosynthesis

  
• Glucose can be converted back into carbon dioxide during cellular respiration
• Cellular Respiration 

  • The main way that chemical energy is harvested from food and converted to ATP 
  • This is an aerobic process - it requires oxygen
• • Cellular respiration and breathing are closely related.
  • Cellular respiration requires a cell to exchange gases with its surroundings 
  • Breathing exchanges these gases between the blood and outside air

  
• • A common fuel molecule for cellular respiration is glucose 
• • During cellular respiration, hydrogen and its bonding electrons change partners 
• • Hydrogen and its electrons go from sugar to oxygen, forming water
• 1. Redox Reactions are Chemical reactions that transfer electrons from one substance to another are called oxidation-reduction reactions
  2. Redox reactions for short
• • The loss of electrons during a redox reaction is called oxidation 
• • The acceptance of electrons during a redox reaction is called reduction
• WHY IS RESPIRATION NECESSARY?

  Plants need energy to perform many essential functions of life: 

  • GROWTH, 
  • REPAIR, 
  • NUTRIENT
  • MOVEMENT, 
  • REPRODUCTION, & 
  • NUTRIENT TRANSPORT.
• • Cellular respiration is an example of a metabolic pathway 
  • A series of chemical reactions in cells
  • building or degradation process
• • All of the reactions involved in cellular respiration can be grouped into three main stages: 
  • Glycolysis 
  • The Krebs cycle 
  • Electron transport 
• Stage1: Glycolysis
• • Glycolysis breaks a six-carbon glucose into two three-carbon molecules 

  These molecules then donate high energy electrons to NAD+, forming NADH
• • A molecule of glucose is split into two molecules of pyruvic acid

  
• Stage 2: Krebs Cycle
• • The Krebs cycle completes the breakdown of sugar
• • In the Krebs cycle, pyruvic acid from glycolysis is first “prepped” into a usable form, Acetyl-CoA 

  
• • The Krebs cycle extracts the energy of sugar by breaking the acetic acid molecules all the way down to CO2 
  • The cycle uses some of this energy to make ATP 
  • The cycle also forms NADH and FADH2

  
• Stage 3: Electron Transport
• • Electron transport releases the energy your cells need to make the most of their ATP
• • The molecules of electron transport chains are built into the inner membranes of mitochondria 
• • The chain functions as a chemical machine that uses energy, released by the “fall” of electrons to pump hydrogen ions across the inner mitochondrial membrane 
  • These ions store potential energy

  
• The Versatility of Cellular Respiration 

  Cellular respiration can “burn” other kinds of molecules besides glucose

  • Diverse types of carbohydrates 
  • Fats 
  • Proteins
• Fermentation: Anaerobic  Process of Food Industry
• • Some of your cells can actually work for short periods without oxygen 
  • For example, muscle cells can produce ATP under anaerobic conditions 
• • Fermentation - The anaerobic harvest of food energy