Metabolism and Enzymes

• Metabolism


  All the chemical reactions that take place in the cell
• Catabolic Reactions


  • Large molecules are broken down into smaller ones
  • Release energy
• Catabolic Reactions


  • Glycolysis
  • Digestion of food
  • Beta-oxidation
• Anabolic Reactions


  • Small molecules are built into larger ones
  • Requires energy to occur
• Anabolic Reactions


  • Bone growth mineralization
  • Muscle mass build up
  • Protein synthesis
• Enzymes


  Proteins that act as a catalyst (speed up) specific chemical reactions without being altered themselves
• Chemical reactions can be divided into many small steps or metabolic pathways
• Each step of a chemical reaction can require a specific enzyme for the reaction to proceed
• Why we need enzymes

  • At body temperature they speed up the chemical reactions at a fast enough rate for the body to function
  • Without enzymes speeding up reactions, the reaction would occur too slow to maintain homeostasis
• Activation energy


  The reacting particles MUST collide with enough energy to break the bonds
• How enzymes work


  Enzymes lower the activation energy by reducing the stability of the reactants OR providing alternative pathways
• Lock-Key Model


  • Attachment: The active site on the enzyme attaches to a substate molecule
  • Weakening of bonds: The enzyme causes weakening of the bonds = lowers the activation energy
  • Reaction Proceeds: The enzyme is NOT 'used up' or altered and therefore can be reused again and again
• Nutrient


  Any substance in food that is used for growth, repair or maintain our body
• Organic Compound


  Large compounds that always contain the element carbon
• Carbohydrates


  • All carbohydrates contain atoms of Carbon, Hydrogen, Oxygen
  • There are twice as many hydrogen atoms as oxygen atoms
  • Usually follows the ratio 1C:2H:1O
• Function of Carbohydrates


  • Main source of energy for cells
  • Simple sugars (particularly glucose) is used in cellular respiration to release energy
  • Complex carbohydrates such as starch are broken down into simple sugars
• Types of Carbohydrates


  • Monosaccharides: simple sugars, 'mono' means one (e.g. glucose, fructose, galactose)
  • Disaccharides: when two simple sugars join together, 'di' means two (e.g. sucrose, maltose, lactose)
  • Polysaccharides: when many sugars are joined together, 'poly' means many (e.g. glycogen, cellulose, starch)
• Lipids


  • Contain carbon, hydrogen, and oxygen
  • A smaller proportion of oxygen than in carbohydrates
  • Each lipid molecule contains one molecule of glycerol and 1,2 or 3 fatty acid molecules
• Glycerol


  • Can enter the glycolysis pathway of cellular respiration and its broken down to release energy
• Functions of lipids


  • Building blocks of fatty acids & glycerol
  • Energy source (lipids contain twice as much energy as carbohydrates)
  • Energy store
  • Insulation
  • Protects organs
  • Structural functions (e.g. Cell membrane)
  • Chemical messengers (e.g. hormones)
• Triglycerides


  Most lipids are triglycerides – i.e. one glycerol molecule attached to three fatty acid molecules
• Proteins


  • Contain carbon, hydrogen, oxygen, nitrogen, and some contain elements such as iron, Sulphur & phosphorous
• Functions of proteins


  • Structural (eg. Muscles)
  • Metabolic (eg. Enzymes)
  • Oxygen transport (haemoglobin)
  • Protection (antibodies, blood clotting)
  • Energy source (in emergencies, only if sufficient carbohydrates and lipid molecules are available)
• Amino acids


  • Proteins are the building blocks of amino acids
  • When two amino acids join together a peptide bond is formed and releases a water molecule
  • An amino acid molecule that contains both an amino group and a carboxylic acid group
  • There are 20 different amino acids found in proteins, each has a different structure of its side chain
• Nucleic acids


  • Include DNA and RNA
  • DNA is double stranded and carries genetic information in the nucleus, consists of two chains of nucleotides that contain the sugar deoxyribose
  • RNA is single stranded and is involved in protein synthesis
• Inorganic compounds


  Substances that do not contain carbon
• Vitamins


  • Inorganic substances essential in small quantities for normal health
  • Acts as coenzymes or help regulate metabolic processes
• Dietary minerals


  The chemical elements required by living organisms
• Functions of dietary minerals

  • Ca is needed and bones and muscles
  • Fe is needed in haemoglobin
  • P is an essential element in nucleic acids (DNA & RNA)