THE LIVING BODY Digestive System and Digestion Add

THE LIVING BODY Digestive System and Digestion

Add iodine solution Starch test Colour change: orange/brown to blue/black

Test for sugar Add Benedict’s reagent, then HEAT Colour change: blue brick red

Test for proteins Add Biuret reagent Colour change: blue to purple

Remember! • Benedict’s reagent & Biuret reagent are BLUE • Proteins turn PURPLE

Test for Vitamin C If a sample, e. g. lemon juice, is added to a particular volume of DCPIP, the LESS juice needed to decolourise the DCPIP, the MORE vitamin C is present.

Fat leaves a grease spot on paper

Vitamins Vitamin Found in Function Deficiency C Citrus fruits e. g. oranges Proper formation of gums, skin etc. Scurvy (fatal) D Cod liver oil, egg yolk; formed in skin (sunlight) Healthy teeth & bones Rickets

Minerals Mineral Found in Function Deficiency Iron Red meat, green veg Make haemoglobin Anaemia (pale & tired) Calcium Dairy products e. g. milk Healthy teeth & bones Rickets

MALNUTRITION AND STARVATION Malnutrition is caused by not eating a balanced diet, which leads to health problems such as protein deficiency or obesity. Starvation is when a person does not eat enough food to keep them alive.

THE SEVEN COMPONENTS OF A HEALTHY DIET 1. 2. 3. 4. 5. 6. 7. Carbohydrates (bread, potatoes etc): energy Proteins (meat, eggs etc): growth & repair Fats (butter etc): energy store/insulation Water: solvent, transport, chemical reactions Fibre (fruit and vegetables): prevents constipation Vitamins: prevent deficiency diseases Minerals: prevent deficiency diseases

VARIATION 1. 2. 3. IN ENERGY REQUIREMENT Several factors can affect an individual’s energy requirement: Age Sex Activity

Enzymes • proteins • act as biological catalysts • speed up chemical reactions • specific: one enzyme speeds up one reaction e. g. protease breaks down protein into amino acids, but will not break down starch. This is because the active site of each enzyme is a different shape.

DENATURING ENZYMES As the temperature increases from 0ºC, the rate of the reaction increases. At around 40ºC (just above body temperature), the rate starts to decrease. This is because the high temperature changes the shape of the enzyme’s active site, and the substrate no longer fits. The enzyme is said to be denatured. A change in p. H has a similar effect.

Graph showing the effect of temperature on the rate of an enzyme-catalysed reaction.

EXAMPLES OF ENZYMES Carbohydrase e. g. amylase breaks down starch into glucose Protease e. g. pepsin breaks down protein into amino acids Lipase breaks down fats (lipids) into fatty acids and glycerol

REACTIONS 1. 2. CONTROLLED BY ENZYMES Building up larger molecules from smaller molecules (anabolic), e. g. protein synthesis Breaking down larger molecules into smaller molecules (catabolic), e. g. digestion

What is digestion? Breaking down of large insoluble molecules into small soluble molecules to be absorbed into and then transported in the blood

The structure of an incisor tooth

TOOTH DECAY bacteria in plaque break down sugar to acid erodes enamel this results in tooth decay. Fluoride strengthens tooth enamel

The digestion of a gram of fat releases more than twice as much energy as that released from carbohydrate or protein: carbohydrate 17 k. J/g protein 17 k. J/g fat 39 k. J/g

The digestive system of man buccal cavity oesophagus thorax diaphragm abdomen caecum appendix stomach liver pancreas duodenum ileum small intestine colon rectum large intestine anus

DIGESTIVE SYSTEM http: //highered. mcgrawhill. com/sites/0072495855/student_view 0/chapter 26/a nimation__organs_of_digestion. html overview of the digestive system http: //www. argosymedical. com/Digestive/samples/ani mations/Digestion/index. html another overview

Ingestion Digestion Absorption Assimilation Egestion taking food into the mouth breaking down food into soluble stomach, molecules duodenum, ileum taking products of digestion into ileum bloodstream e. g. respiration, cells of the body making proteins removal of undigested food anus

The tongue helps to mix the food and saliva together. The small pieces of food are than made into a ball or bolus and swallowed. http: //www. argosymedical. com/Digestive/samples/animations/Sherwood %20 Swallowing/index. html

Peristalsis When the circular muscles in the oesophagus contract the food is pushed towards the stomach. This is known as peristalsis. Food moves along the whole alimentary canal by peristalsis.

Digestion in the stomach The oesophagus carries food to the stomach. The stomach is like a bag and the food must stay there for some time. The cells lining the stomach make gastric juice and acid. The food is mixed with gastric juice and acid when the muscles in the stomach wall contract.

Digestion in the small intestine When food leaves the stomach it goes into the small intestine. The two parts of the small intestine are called the duodenum and the ileum. http: //www. yout ube. com/watch ? v=u. NGzmqg. J KNg

What happens to undigested food Some of the food we eat cannot be digested. Vegetables and other foods which come from plants have cell walls made of cellulose.

Absorption The small soluble products of digestion e. g. glucose, amino acids and fatty acids and glycerol are absorbed in the ileum The ileum is adapted to absorb these substances as 1. It is very long 2. It has villi to increase its surface area 3. It has a very close blood supply for the products of digestion to be absorbed into

What happens to the digested foods Digested foods are carried away from the ileum by the blood and lymph systems. The blood carries glucose and amino acids to the liver. The lymph carries digested fats to a vein at the base of the neck. The digested fats than pass into the blood system.

http: //www. youtube. com/watch? v=P 1 s. D OJM 65 Bc

The liver: 1. changes glucose into glycogen to store it. 2. changes glycogen into glucose when it is needed by the body. 3. changes amino acids which cannot be used by the body into urea (deamination). 4. makes bile. 5. Detoxifies the blood, e. g. by breaking down alcohol.