Digestive system

• Bile produced by the liver is secreted into the small intestine by the gall bladder to emulsify large fat globules into small fat droplets to increase the surface area to volume ratio of the fats, allowing more lipase to be in contact with the fat and speed up digestion.
• Gastric juices in the stomach contain hydrochloric acid that kills microorganisms and creates an acidic environment for protease to digest protein.
• Benedict's Test is used to detect reducing sugars when the solution turns from blue to brick-red.
• Iodine is used to detect starch when it changes from yellow-brown to blue-black
• Ethanol emulsion test is to detect fats when the solution turns cloudy
• Biuret test detects protein when the solution turns from blue to purple
• The types of reducing sugars are galactose, fructose, lactose and glucose.
• Iodine turns from yellow-brown to blue-black when in contact with starch
• Why do we need food?

  Food provides energy for vital activities like synthesizing new protoplasm, growth, and repair of worn out body parts.
• Digestion


  Digestion is the breaking down of large, complex and insoluble food molecules into small, simple and soluble molecules.
• Why is digestion important?

  Food molecules are too large to pass through our intestine walls. It has to be broken down into smaller molecules to be able to pass through the partially permeable membranes into the blood.
• Physical digestion

  Breaking down of food through physical or mechanical means like crushing or chewing to increase SA to V ratio for enzymes to access the food and break food down faster.
• Chemical digestion


  Breaking the chemical bonds between the

  atoms in the food through the use of enzymes, resulting in the simplest, smallest form of nutrients for absorption.
• Enzymes

  Catalysts that speed up breakdown of large molecules into smaller molecules
• Breakdown of Carbohydrates

  Starch > (Amylase) > Maltose > (Maltase) > glucose
• Carbohydrates (simplest form, function)

  Found in starchy sweet foods, breaks down into glucose , is a source of energy and part of respiration
• Protein breakdown process

  Protein > (protease) > Polypeptide > (Protease) > Amino Acids
• Protein (simplest form, function)


  Found in meat, fish, beans, eggs, breaks down into amino acids, used for growth or repair of cells
• Breakdown of fats (lipids)

  Fats > (lipase) > 1 glycerol, 3 fatty acids
• Fats (simplest form and function)

  - Found in dairy products

  - breaks down into fatty acids and glycerol

  - stored under skin to prevent heat loss and cushion internal organs

  - Long term storage of energy in animals
• Mouth physical digestion

  Teeth chew and crush food into smaller pieces.. This increases the surface area to volume ratio of the food for enzymes to access the food to increase the rate of chemical digestion
• Mouth chemical digestion

  Saliva contains amylase that breaks starch down into maltose.
• Uses of saliva and tongue

  • Saliva also helps to lubricate the food, making it easier to swallow.

  • Tongue rolls the food into a ball to swallow.
• Oesophagus


  •Muscular tube where starch from mouth continues to be digested by amylase to maltose

  • The food travels to the

  stomach via gravity, as well

  as muscle contractions. (Peristalsis)
• Physical digestion in the stomach

  Stomach churns the food into smaller pieces
• Chemical digestion in stomach

  Releases gastric juices containing protease to break protein down into polypeptides
• Hydrochloric acid


  - Kills microorganisms like bacteria

  - Creates an acidic environment for protease to work

  - acidity too high for amylase to work, hence digestion of starch is stopped
• Physical digestion in small intestine

  Bile is produced by the liver and is accumulated and

  secreted by gallbladder. Bile emulsifies fat from large fat globules to small fat droplets. Increases SA to V ratio for it to be exposed to lipase.
• Chemical digestion in small intestine

  - Main site of chemical digestion where all nutrients are completely digested

  - Amylase, maltase, proteases, lipases are present

  - Digested nutrients absorbed into the bloodstream
• Large Intestine

  mainly absorbs water and mineral salts from food
• Rectum


  Temporarily stores faeces
• Anus


  Ring of muscle that releases faeces out of the body
• Diabetes


  A condition in which the body is unable to produce enough insulin or does not respond to insulin, the hormone that regulates the concentration of glucose in the body.

  - linked to serious health conditions like obesity, heart attacks, kidney problems
• Diabetes symptoms

  - slow healing of wounds

  - constant hunger

  -frequent urination

  - tingling or numbness in hands or feet

  - unexplained weight loss

  - blurred vision
• Diabetes Monitoring

  Blood sugar meter or continuous monitoring
• Constipation


  Faeces moving through large intestine slowly that the large intestine absorbs more water resulting in faeces becoming hard and dry
• Gastritis

  Painful swelling or inflammation of the stomach lining.

  Caused by bacteria, virus, or lifestyle habits like skipping meals
• Food poisoning

  Leads to diarrhoea or vomiting and can lead to life threatening diseases like cholera and salmonella
• Beneficial bacteria

  Helps our immune systems, digestion and absorption of nutrients, and produces certain enzymes, vitamins and amino acids
• Benedict's test

  - Test for reducing sugars like glucose, galactose, fructose or lactose ( not sucrose or starch)

  - Heat solution with Benedict's solution in a water bath

  Blue - Green — Yellow -- Orange — Brick-red