Chapter 6-Protiens

• Amino Acid


  Building block of proteins
• Components of amino acids

  • Carbon
  • Hydrogen
  • Oxygen
  • Nitrogen
  • Sulfur
• Parts of an amino acid

  • Carboxy acid group (CO₂H)
  • Amino group (NH₂)
  • Side chain group
• Essential amino acids


  Amino acids that cannot be synthesized by humans in sufficient amounts or at all and must be obtained through diet
• Non-essential amino acids

  Amino acids that can be synthesized by humans in sufficient amounts
• Dispensable amino acids


  Amino acids that can be made by the body
• Peptide bond


  Chemical bond (hydrogen bond) that links amino acids together in a protein
• Polypeptide


  Chains of many amino acids
• Denaturation


  Alteration/change of a protein's 3-dimensional structure, usually due to heat, enzymes, acids or bases
• High quality (complete) proteins


  Dietary proteins that optimally contain large amounts of all the essential amino acids
• Lower quality (incomplete) proteins

  Dietary proteins that are low or lack one or more essential amino acids, primarily of plant origin
• Pepsin


  Enzyme made in the stomach that degrades proteins
• Trypsin

  Enzyme made in the pancreas that digests proteins in the small intestine (duodenum)
• Urea


  Nitrogenous waste product of protein metabolism, major source of nitrogen in urine
• Edema


  Build up of excess fluid in the extracellular space
• Proteins are made up of carbon, oxygen, hydrogen and nitrogen atoms; sometimes sulfur
• Proteins are made up of a sequence of subunits called amino acids held together by peptide bonds
• All proteins are made up of a combination of 20 amino acids
• Eggs are a high quality protein source as they contain the maximum amount of essential amino acids
• Good food sources of proteins

  • Meats
  • Poultry
  • Eggs
  • Fish
  • Beans
  • Nuts
  • Milk
  • Dairy
  • Soy
• Components of an amino acid

  • Carboxyl group (COOH)
  • Amino group (NH₂)
  • Side group (R)
• Types of peptides


  • Dipeptide (2 amino acids)
  • Tripeptide (3 amino acids)
  • Polypeptide (chains of many amino acids)
• Functions of proteins

  • Building blocks (Structure)
  • Tissue growth (muscles)
  • Enzymes (metabolism)
  • Hormones (regulation of body/functions)
• Proteins

  • Insulin
  • Antibodies (Protection against infections)
• Sources of protein within the body

  • Hair, Nails, Skin = Keratin
  • Muscle tissue = Myosin & Actin
  • Bones = Bone
  • Red Blood Cells = Hemoglobin
  • Blood (3 main proteins) = Albumin, Globulin, Fibrinogen
  • DNA & RNA (Nucleic Acids) = Proteins
• Essential amino acids

  • Histidine
  • Isoleucine
  • Leucine
  • Lysine
  • Phenylalanine
  • Threonine
  • Tryptophan
  • Valine
• Non-essential amino acids


  • Alanine
  • Arginine
  • Aspartic acid
  • Asparagine
  • Cysteine
  • Glycine
  • Glutamic Acid
  • Glutamine
  • Proline
  • Serine
  • Tyrosine
• Digestion of protein

  1. Mechanical digestion in mouth

  2. Chemical digestion begins in stomach, activates pepsin

  3. Pepsin breaks down proteins into polypeptides

  4. Trypsin (from pancreas) breaks down polypeptides

  5. Absorption of amino acids into blood

  6. Liver converts nitrogen to urea (waste product)
• Most foods from animals have complete proteins, while vegetables, fruits, and grains have incomplete proteins. Exception: soy beans have complete proteins with sufficient amount of all essential amino acids, no cholesterol and dietary fiber.
• Protein intake


  • Women: 46g protein/day
  • Men: 56g protein/day
  • Body weight (lbs) / 0.8g protein/kg
  • Infants and children need more protein per unit body weight than adults due to development
• Phenylalanine (essential amino acid) is needed to synthesize amino acid tyrosine (non-essential) in the human body. A hereditary disease caused by a defective enzyme needed to make tyrosine results in excessive amount of phenylalanine in blood, leading to severe mental retardation if not detected at birth.
• Protein deficiency symptoms


  • Muscle weakness
  • Thin hair/loss of hair
  • Flaky/scaly skin
  • Anemia
  • Edema (not enough protein)
• Protein excess symptoms


  • Increased kidney disease
  • Gout (build-up of uric acid in blood)
  • Affect nervous system
  • Increased risk of cancer
  • Increased risk of kidney stones
• Amino acid


  The basic building block of a protein
• Polypeptide


  A group of amino acids bonded together through peptide bonds
• Essential amino acids


  Amino acids that can not be made by humans in sufficient amounts
• Nonessential amino acids


  Amino acids that can be made within the human body in sufficient amounts
• Complete proteins


  High-quality proteins that contain all the essential amino acids
• Incomplete proteins


  Low-quality proteins that are low or lack some amino acids
• Peptide bond


  The chemical bond that links amino acids together in a protein