chapter 3 - cellular metabolism

• all energy of organisms is ultimately derived from the sun
• autotrophs

  • use suns energy to create organic molecules that can store energy in their bonds
• heterotrophs

  • derive energy by breaking down organic molecules made by plants
• plants carry most of the earths autotrophic functions through the anabolic process of photosynthesis
• glucose is a simple sugar that can form ring structures called pyranoses
• in plants - photosynthesis

  in animals - cellular respiration
• when glucose breaks down, energy is released
• ATP, NAD+, and FAD are energy carriers taking energy where it is needed
• ATP

  • cells main energy currency
  • allow for energy to be stored and released as needed
  • made of adenine, ribose, and 3 phosphate groups
• NAD+ and FAD

  • coenzymes that carry high energy electrons
  • energy used to produce ATP
• glycolysis is a process that breaks down glucose into smaller molecules
• glycolysis occurs in the cytoplasm and can happen with or without oxygen
• glycolysis

  • inputs - 1 molecule of glucose (6 carbon)
  • outputs - 2 molecules of pyruvate (3 carbon each), 2 ATP, 2 NADH
• fermentation helps regenerate NAD+ so that glycolysis can continue when oxygen is not available
• after glycolysis, pyruvate is converted to either ethanol or lactic acid
• alcohol fermentation

  • pyruvate turned into acetaldehyde and then ethanol
  • releasing CO2+ and regenerating NAD
• lactic fermentation

  • pyruvate directly converted into lactic acid
  • regenerating NAD+
• cellular respiration is the most efficient way to break down glucose

  38-38 ATP per glucose
• cellular respiration - 3 main stages

  1. pyruvate decarboxylation - pyruvate converted into acetyl-CoA in mitochondria releasing CO2 and producing NADH
  2. citric acid cycle - breaks down acetyl-CoA, releasing more CO2 and generating NADH + FADH2
  3. electron transport chain - produce ATP with oxygen to form water
• glucose metabolism

  1. glycolysis - cytoplasm
  2. fermentation - cytoplasm
  3. pyruvate to acetyl-CoA - mitochondrial matrix
  4. electron transport chain - inner mitochondrial membrane
• carbohydrates

  • monosaccharide
  • sugar polymers can be broken down during digestion and stored in liver for later use as glycogen
• fats

  • stores as triglycerides in adipose tissue
  • highly efficient for long term energy storage
  • to utilize fats for energy storage, fatty acids go through beta-oxidation in mitochondria
• proteins

  • polypeptides made of amino acids
  • used as energy source when carbohydrates are not enough