DIGESTION Flashcards
A balanced diet consists of?
- vitamins
- minerals
- carbs
- fats
- fibre
- water
- protein
What is iodine used to test for?
Starch
Iodine result if starch is present?
Blue/black
Iodine test?
- Grind the food
- Add 5 drops of iodine solution to 5cm cubed of food sample
- Gently shake
- Colour change, brown-orange to blue/black
What is biuret used to test for?
Protein
Biuret result is protein is present
Lilac/purple
Biuret test?
- Grind the food
- Add 5 drops of biuret to the sample
- Colour change, blue to lilac/purple
What is Benedicts used to test for?
Glucose
Benedicts result if glucose is present?
Brick-red
Benedicts test?
- Grind the food
- Add 10 drops of Benedicts to 5cm cubed of the food sample
- Heat in a water bath at 80C for 5 minutes
- Colour change to brick-red
What is Sudan III used to test for?
Lipids/fats
Sudan III result if lipids/fats are present?
- the mixture will separate into 2 layers
- top layer will be bright red
- if no lipid present there will be no red layer
Sudan III test?
- Grind the food
- Add 3 drops of Sudan III solution to 5cm cubed of the food sample and gently shake the tube
- The mixture will separate into 2 layers, top layer will be bright red. If no lipid present there will be no red layer
The mouth?
- Food is eaten here.
- Mechanical and chemical digestion takes place.
- Your teeth chew the food and break it down into smaller pieces mechanically, to increase surface area of food and easier to swallow
- The enzyme amylase contained within the saliva starts to break down starch into maltose.
- With the help of the tongue food is rolled into balls of food called a bolus and swallowed.
The oesophagus?
• The food pipe connecting the mouth to the stomach
• Food is moved down here with the aid of muscular contractions known as
peristalsis
(Note: peristalsis also occurs in the intestines)
The stomach?
- Large muscular bag – contracts and relaxes to churn the food.
- The food is mixed with gastric juice, produced by millions of gastric glands located in the stomach walls.
Gastric juice consists of:
• Proteases – Enzymes which break proteins into amino acids
• HCl – kills bacteria and provides acidic (pH 2) conditions which are optimal for stomach proteases.
The churned food is known as chyme
Duodenum in the small intestine
- This is the first section of the small intestine
- It is where most digestion is completed.
- Digestive juices are secreted from the pancreas (pancreatic juice) and the intestine walls. These include carbohydrases (including maltase and pancreatic amylase), proteases and lipases.
- Bile, which is made in the liver, and stored in the gall bladder is released into the duodenum
- The function of bile is to emulsify fats (makes large fat droplets into smaller fat droplets). This provides a larger surface area on which the enzyme lipase can act.
- Bile also neutralises stomach acid which will be in the partly digested food (chyme) that moves into the duodenum from the stomach
Ileum in the small intestines
• The ileum is the part of the small intestine where most of the absorption of foods takes place.
Absorption: digested food molecules are absorbed
• The inner surface is folded, producing finger-like projections called villi
• Absorption may take place by diffusion or via active transport.
Villi?
(infoldings of the wall of the ileum section of the small intestine)
Function of villi?
• Increase surface area and therefore greatly improve the efficiency of the absorption process.
• Have very thin walls to decrease diffusion distance.
• Each villi has a network of capillaries and a lacteal (a small vessel of the
lymphatic system).
• Amino acids and glucose are absorbed into the blood and taken via the hepatic portal vein to the liver for processing.
• Fatty acids and glycerol are taken into the lacteal and travel in the lymphatic system.
Colon in the large intestines
Most useful substances have been removed by the time food enters the large intestines, what’s left is:
• Undigested food
• Mucus
• Dead cells
• Bacteria
The main role is the reabsorption of water and mineral ions such as sodium and chloride. Water found in the large intestines is not only from our dietary intake but also additional quantities added by the body within digestive juices.
Rectum in the large intestine
What remains after this point is known as feces and is stored in
the rectum until it is egested from the body via the anus
Egestion: discharge of undigested material from the digestive tract.
What are enzymes?
- special chemicals released at diff points in the digestive system
- these chemicals break up large molecules of food into smaller molecules of food so that they can be absorbed
- there are diff enzymes for diff nutrients
Amylase digests starch into…
Maltose
