BIO UNIT 2

• Carbohydrates


  The first nutrients most organisms catabolize for energy
• Digestion of larger molecules

  1. Digested into component parts

  2. Cell reassembles into macromolecules for energy use

  
• Deamination

  1. Amino group (NH2) is removed from amino acid

  2. Amino group is converted to ammonia (NH3)
• Fate of remaining portion of amino acid

  1. Enters pyruvate oxidation

  2. Enters Kreb's cycle
• Less ATP is made overall when amino acids are used for energy
• Lipid metabolism

  1. Triacylglycerol metabolizes to form glycerol + 3 fatty acid chains

  2. Glycerol backbone can turn into glucose (gluconeogenesis) or DHAP

  3. Fatty acids undergo beta-oxidation in mitochondrial matrix

  
• Cells possess a limited supply of NAD+
• If oxygen is not present, NADH cannot be oxidized back to NAD+ and glycolysis will stop

  
• Fermentation

  Recycles NAD+ and allows glycolysis to continue when oxygen is unavailable

  
• Fermentation is much less efficient at supplying energy than aerobic respiration, but it is still commonly used
• Different fermentation pathways

  • Ethanol fermentation
  • Lactic acid fermentation
• Ethanol fermentation

  1. NADH is oxidized and donates its H atoms to acetaldehyde

  2. Acetaldehyde is formed when a CO2 molecule is removed from pyruvate

  3. Forms ethanol (alcohol used in alcoholic beverages)

  4. Recycles NAD+ and allows glycolysis to continue

  5. Produces 2 ATP

  
• Yeast


  Used to manufacture baked goods and alcoholic beverages since ancient times
• Yeast and some bacteria can function in both aerobic and anaerobic conditions
• Ethanol


  • Small uncharged polar molecule that can diffuse into virtually all cells
  • Interferes with nervous system signalling
  • Can change viscosity of fluid in ear canals, affecting balance
  • Metabolized by enzymes in liver, producing acetaldehyde
• Lactic acid fermentation

  1. NADH produced in glycolysis is oxidized and transfers its H atoms to pyruvate, regenerating NAD+ and allowing glycolysis to continue

  2. Each pyruvate becomes a lactate molecule (lactic acid)
• The accumulation of lactate molecules in muscle tissue causes stiffness, soreness, and fatigue
• Fate of lactic acid

  1. Reoxidized back to pyruvate when vigorous exercise stops and oxygen is available

  2. Transported to liver and converted to glucose and glycogen

  
• Oxygen debt


  The extra oxygen required to catabolize lactate to CO2 and H2O

  
• Panting after exercising is the body's way of "re-paying" the oxygen debt
• Summary of anaerobic respiration

  • Only goal is to convert NADH to NAD+ (to use in glycolysis)
  • No energy is directly gained (ATP is ONLY made in glycolysis)
  • Anaerobic respiration - 2 ATP produced
  • Aerobic respiration - 36/38 ATP produced

  
• Photosynthesis


  The process by which cells synthesize organic molecules (e.g. glucose) from inorganic molecules (CO2 and H2O) using the energy found in sunlight

  
• Photosynthesis

  • Requires a photosynthetic pigment (chlorophyll and others such as carotenoids)
  • Can only occur in certain organisms (plants, algae, and some bacteria)

  
• Chloroplast


  The specialized organelle in plants where photosynthesis occurs

  
• Photosynthesis

  1. Energy transformation from photons of light to energy available in glucose

  2. Carbon dioxide + water → glucose + oxygen

  
• Stages of Photosynthesis

  1. Light Dependent Reactions (LDR)

  2. Light Independent Reactions (Calvin Cycle)

  
• Light Dependent Reactions (LDR)

  Light energy is captured and used to make ATP and reduce NADP+ to NADPH
• Light Independent Reactions (Calvin Cycle)

  Use the energy from ATP and reducing power of NADPH to make glucose, from CO2

  
• Photosynthesis occurs in the thylakoid membrane (LDR) and the stroma (Calvin Cycle)

  
• Chloroplast

  • Has two membranes: an outer and inner membrane
  • Interior space filled with semi-liquid material called stroma
  • Contains tiny sacs called thylakoids that stack to form columns called grana
  • Neighbouring grana are connected by unstacked thylakoids called lamellae

  
• Photon

  A packet of light energy
• Pigments

  • Substances that absorb certain wavelengths of light and reflect others
  • Plants have many different pigments to absorb more energy from the sun
• Chlorophyll a

  The main plant pigment that absorbs in the blue and red regions of the visible spectrum
• Chlorophyll b


  A type of chlorophyll that differs from chlorophyll a in its functional groups
• Chlorophyll a is the reaction centre pigment of the photosystem
• Accessory/Antennae pigments

  Collect energy from various wavelengths of light other than those absorbed by chlorophyll a and pass it to the reaction centre chlorophyll a
• Photosystems

  • Clusters of hundreds of pigments and proteins that work together to absorb the energy found in the wavelengths of visible light
  • Embedded within the thylakoid membrane and contain reaction centre chlorophyll a surrounded by antennae pigments

  
• When photons strike a pigment, the energy is passed from molecule to molecule until it reaches the reaction centre chlorophyll a
• Photosynthesis has two photosystems in the light dependent reactions

  
• Photosynthetic structures appear green because all the colours in the visible spectrum are absorbed except green