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

Introduction to metabolism