Section 2 : Human Nutrition

• Starch -> iodine -> turns blue-black
• Glucose -> Benedict's Solution -> heat till 80 degrees for 5 mins -> green to brick red. It is semi quantitative
• Fats - ethanol -> cloudy/milky appearance
• Protein -> Biuret Solution -> turns mauve upon presence
• Amylase -> digest starch -> glucose and maltose

  Amylase - polysaccharide of glucose

  Maltose - disaccharide of glucose
• pH and Enzyme function

  Low:

  • Enzyme action is slower
  • Less thermal energy converted into KE
  • Less collision & chemical reaction

  High:

  • Enzyme activity is faster
  • More KE for particle collision
  • Too much temp. -> enzymes denature & no enzyme - substrate complex made
• Denaturisation:

  • Active site changes shape
• Energy Requirement Factors :

  • Age
  • Gender
  • Activity Levels
  • Breastfeeding
  • Pregnancy
• Malnutrition : Lack/Excess of nutrients for human consumption
• Vitamin A

  Source : Carrots, retinol

  Function : Maintain retina of the eye

  Deficiency : Blindness
• Vitamin C

  Source : Citrus fruits

  Function : Make connective tissue

  Deficiency : Scurvy
• Vitamin D

  Source : Sunlight & Salmon

  Function : Helps bones absorb calcium

  Deficiency : Rickets/Weak bones
• Calcium

  Sources : Milk, Cheese, Eggs

  Function : Making bones & teeth

  Deficiency : Muscle aches, cramps, spasms
• Iron

  Sources : Spinach, Red meat

  Function : Making haemoglobin in red blood cells to carry oxygen

  Deficiency : Fatigue and pale skin
• Carbohydrates

  Sources : Rice, pasta, potatoes

  Function : Respiration ; release energy
• Protein

  Source : Chicken, Beef, Fish

  Function : Growth & Repair of cells
• Lipid

  Source : Butter, margarine, cheese, oily fish

  Function : Insulation and protecting organs
• Dietary fibre

  Sources : Vegetables & whole grains

  Function : Moves food along the gut
• 1. Mouth

  • Chemical Digestion - Amylase in saliva breaks down starch into maltose
  • Mechanical Digestion - Teeth break down food into smaller chunks -> gives enzymes a large surface area to work
• 2. Oesophagus

  • Bolus passes from the mouth into the stomach
• 3. Stomach

  • Chemical Digestion - Protease enzyme called pepsin breaks down protein into amino acids
  • Mechanical Digestion - Muscular stomach wall churns up the food. Secretes HCl to kill bacteria to protect us from food poisoning
• 4. Duodenum

  • Pancreatic juice contains several enzymes -> Amylase, Trypsin, and Lipase
  • Bile and pancreatic juice are alkali, neutralise the food covered in stomach acid
• 5. Ileum

  • Absorbs food into blood. Large surface area with villi & microvilli
• 6. Large intestine

  • Colon absorbs water
  • Indigestible fibre, feces stored in rectum and expelled in the anus. This is called egestion.
• Liver:

  • Bile is made there
  • Emulsify lipids; not an enzyme
• Gall Bladder:

  • Bile is stored and secreted in the duodenum as food passes there.
• Pancreas:

  • Makes pancreatic juices and enzymes; Breaks down sugar, fats and starches