Introduction to metabolism

							Introduction to metabolism

         Chapter 3
                   Objectives
• Recognize the difference between a macro and a
  micronutrient.
• Recognize the role of antioxidants
• Be able to describe the role of enzymes and how
  enzymes work
• Be able to explain the difference between Active and
  passive transport
• Be able to explain simple diffusion, osmosis,
  facilitated diffusion, Pumps, and exo/endocytosis
                           Diet
• One’s diet is important to
  one’s physical wellbeing
• The foods we eat supply our
  body will energy and
  building materials
• Energy is stored in the
  macromolecules we
  consume
• Building materials are
  extracted from the
  macromolecules we
  consume
• Different foods have
  different types of materials
              Sources of energy
• Carbohydrates, lipids, and proteins are sources of
  energy for the body
• Energy is stored in the electrons associated with C-H
  bonds
• Lipids contain the most of these bonds per gram and
  so have the highest number of Calories
• A food Calorie contains sufficient energy to elevate 1
  liter of water by 1 degree Celsius
• Energy from foods is converted to ATP: Cell energy
            Building Materials
• Building materials may
  be consumed directly or
  synthesized from
  materials through
  metabolic pathway
• A metabolic pathway is
  a series of chemical
  steps that lead to
  molecules being
  converted to different
  forms
• “Essential” means must
  be eaten
Micronutrients
• Materials needed in
  very small amounts
• Vitamins: fine tune
  body chemistry
• Minerals: structural
  materials
• Water vs. Fat soluble
           Role of Antioxidants
• Metabolism
  occasionally
  produces free
  radicals that
  negatively affect
  body chemistry
• Antioxidants are
  molecules that
  eliminate free
  radicals preventing
  damage to the cells
                Metabolism
• Term used to describe all the chemical
  reactions occurring in an organism
• Break down chemistry is called catabolism
• Buildup (synthesis) chemistry is called
  anabolism
• Most chemistry is assisted by proteins called
  enzymes
                    Enzymes
• Enzymes are proteins
  – Specific because of conformational shape
• Enzymes are catalysts
  – Catalyst: chemical that changes the rate of a reaction
    without being consumed
  – Recycled
• Enzymes reduce the activation energy of a
  reaction
  – Amount of energy that must be added to get a reaction
    to proceed
Activation Energy
         • Activation energy is
           the amount of energy
           that must be supplied
           to get reactants to
           form products
            – is usually supplied by
              heat
         • Prevents reactions
           from “just happening”
   How Enzymes Function
• Enzymes are substrate specific
   – Substrate: any molecule to
     which an enzyme will bind
• Although an enzyme can be a
  large protein, only a specific
  region of the enzyme interacts
  with the substrate
   – Active Site: region of enzyme
     that “reacts” to substrate
• As enzyme and substrate bind,
  the enzyme shape is modified to
  better fit the substrate
   – Induced fit occurs as a result of
     the enzyme substrate complex
                    Enzyme activity
• The rate at which an enzyme
  can function is dependant on
  several factors including:
    – Temperature
    – pH
• The rate of reaction is also
  influenced by the concentration
  of the substrate or enzyme
• Some enzymes utilize inorganic
  or organic molecules as helpers
    – Cofactor: inorganic molecule
      (mineral)
    – Coenzyme: organic non-
      protein molecule (vitamin)
    How do macromolecules enter the cell?




•   The plasma membrane borders every cell in our body
•   Materials have to cross the border to enter the cell
•   This is called membrane transport
•   There are active and passive means of moving materials
•   Active mechanisms requires ATP, passive mechanisms do not
    Plasma membrane composed of both
            lipid and protein




• Lipids: mostly phospholipids arranged as a bilayer
• Proteins: vary in form, some proteins help move molecules
                What moves….
• Passively
  – Through the lipid bilayer (simple diffusion)
     • Hydrophobic (nonpolar) molecules (O2, lipids)
     • Small uncharged polar molecules (CO2, H2O)
  – Through a protein (facilitated diffusion)
     • Hydrophilic (polar) molecules
     • Ions (+ or – charged particles)
• Actively (pump or exo/endocytosis)
  – Requires a protein and ATP
     • Hydrophilic molecules
 Passive Transport
 Mechanisms
• Simple Diffusion: the
  movement of a substance
  from higher concentration
  to lesser concentration
• Osmosis: the diffusion of
  water (solvent) across a
  membrane
  – influenced by total solute
    concentration
           The Importance of
            Osmoregulation
• Living things must
  balance water uptake
  and loss
• If cells lose water they
  crenate (shrivel)
• If cells gain water
  they lyse
Facilitated Diffusion
           • Involves transport
             proteins moving a
             solute along a
             concentration
             gradient
           • May be specific
           • May be saturated
             (can only work so
             fast) or inhibited
           • Assist the physical
             process of diffusion
     Active Transport: Pumps
• Moves solute uphill and requires energy
• Always requires transport proteins
• Major factor that allows the cell to regulate
  the concentration of solute within the cell
• May result in an imbalance of solute
  across a membrane that the cell can utilize
   Exocytosis and Endocytosis
• Exocytosis involve the movement of
  macromolecule out of the cell by the fusion of
  membrane bound vesicles to the plasma
  membrane
• Endocytosis involves the movement of
  macromolecule into the cell by the pinching of
  the plasma membrane into membrane bound
  vesicles
   – Phagocytosis
   – Pinocytosis
    Exocytosis and Endocytosis
• Phagocytosis:
  ingestion of
  large particle
• Pinocytosis:
  ingestion of
  small mixed
  solutes