Chemicals of life and human nutrition

• Chemical elements in carbohydrates, fats, and proteins

  • Carbohydrates: carbon, hydrogen, oxygen
  • Fats and lipids: carbon, hydrogen, oxygen
  • Proteins: carbon, hydrogen, oxygen, nitrogen, sometimes sulfur
• Carbohydrates


  Many sugar molecules containing carbon, hydrogen, and oxygen. Hydrogen to oxygen ratio is always 2:1. Joined with glycosidic bonds
• Fats and lipids


  Composed of glycerol and fatty acids containing carbon, hydrogen, and oxygen (less oxygen in fats). Joined with ester bonds
• Proteins


  Composed of carbon, hydrogen, oxygen, nitrogen, sometimes sulfur linked in chains of amino acids. Joined with polypeptide or peptide bonds
• Synthesis of large molecules from smaller basic units

  1. Glucose to Starch, Glycogen, Cellulose

  2. Amino Acids to Proteins

  3. Fatty Acids and Glycerol to Fats and Oils
• Structure of proteins

  1. Primary: amino acids form a chain

  2. Secondary: hydrogen bonding forms alpha helix and beta sheets

  3. Tertiary: peptide chains join up

  4. Quaternary: folded polypeptides create a complex protein molecule
• Different arrangements of amino acids create different proteins with different shapes when folded, e.g., enzymes or hormones
• Amino acids are small molecules
• Amino acids join together to form a simple chain of polypeptides
• Folded polypeptides form a complex protein molecule
• Tests for various substances

  • Starch (iodine solution)
  • Reducing sugars (Benedict's solution)
  • Protein (biuret test)
  • Fats (ethanol)
  • Vitamin C (DCPIP)
• Water is an important solvent in organisms, making up 60% of the human body. It is involved in many chemical reactions, metabolic reactions, digestion, absorption, and cell hydration
• Functions of water in the body

  • Chemical reactions occur
  • Metabolite involved in many metabolic reactions
  • Needed for digestion to provide a medium for enzymes to act in
  • Allows the products of digestion to be absorbed into the blood
  • Prevents cells from drying out
  • Helps maintain a constant temperature in the body
  • Allows soluble molecules to be transported around the body and through cell membranes
  • Transports waste products so they can be excreted
• A balanced diet contains all essential nutrients (carbohydrates, fats, proteins, vitamins, mineral salts, fiber, and water) in the correct amounts and proportions
• Energy intake and food consumption


  • If you eat too much food, some of the extra will probably be stored as fat
  • If you eat too little, you may not be able to obtain as much energy as you need, making you feel tired
• Diet changes at different life stages

  • Woman needs to eat more when pregnant and ensure extra calcium and iron in her diet
  • Woman needs to eat more while breastfeeding
  • Older people eat less due to slowed metabolism
  • Olympic athletes need much more energy to keep up with training and exercises
• Principal sources of nutrients

  • Carbohydrates
  • Fats
  • Proteins
  • Mineral salts
  • Fiber
  • Water
• Carbohydrates


  • Main source of energy that fuels the body everyday
• Proteins

  • Important for growth and repair of the body's cells and for building muscle
• Fats


  • Contribute to energy intake and help absorb vital vitamins
• Vitamins


  • Required in tiny amounts for normal growth and metabolism
• Effects of malnutrition

  • Starvation
  • Coronary heart disease
  • Constipation
  • Obesity
  • Scurvy
• Starvation

  • Cause: taking in less calories than required
  • Effect: body begins to break down energy stores (fat and protein)
  • Consequences/symptoms: severe weight loss, fatigue, damage to heart and immune system, increased risk of other diseases
• Coronary heart disease

  • Cause: diet high in saturated fats and cholesterol
  • Effect: fat deposits build up in the arteries, reducing blood supply to the heart
  • Consequences/symptoms: heart muscles run short of oxygen, leading to heart attack and death
• Obesity


  • Cause: taking in more energy than required
  • Effect: extra energy is stored as fat
  • Consequences/symptoms: weight gain contributing to diseases like heart disease, strokes, and diabetes
• Constipation

  • Cause: insufficient fiber in the diet
  • Effect: food lacks bulk for muscles to push it through alimentary canal
  • Consequences/symptoms: stomachache, bloating, rectal bleeding
• Scurvy

  • Cause: insufficient vitamin C in the diet
  • Effect: body unable to make collagen, leading to pain in joints and muscles, bleeding from gums and other places
• Vitamin D and iron deficiencies

  Causes and effects
• Scurvy
• Cause


  Insufficient vitamin C in the diet
• Effect

  Body is unable to make collagen, which keeps skin and other tissues in good repair
• Consequences/symptoms

  • Pain in joints and muscles
  • Bleeding from gums and other places
• Explain the causes and effects of vitamin D and iron deficiencies
• Vitamin D deficiency (rickets)
• Cause

  Lack of butter, egg yolk in diet; lack of sunlight
• Effect

  Vitamin D is required for absorption of calcium into bones and teeth, and it also helps with blood clotting; therefore, calcium is not absorbed
• Consequences/symptoms

  • Soft and deformed bones
  • Brittle bones and teeth
  • Poor blood clotting
• Iron deficiency (anaemia)
• Cause

  Lack of iron-rich foods such as liver, red meat and vegetables in diet
• Effect

  Iron is necessary for making hemoglobin, the red pigment in red blood cells that carries oxygen; therefore, the body does not make sufficient red blood cells