FOOD DIGESTION

nutrition6.4 Food digestion

2Substances needed in cell metabolismMetabolism : chemical reaction in cells that keep them alive, growing & dividingDivided into:Catabolism breaking down substances to produce energy & simpler moleculesAnabolism using ATP to synthesize new cell components from simple moleculesSubstances needed for metabolic processes:GlucoseAmino acidlipids

3Functions of glucose in cellular metabolismBroken down to produce chemical energy (ATP)ATP provide energy for all metabolic activities4

Functions of amino acidbasic building blocks of proteinsAbout 22 amino acids are used to synthesize the different type of protein required by the human body

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Lipids are used in the synthesis of:Triglycerides (energy storage molecules)Phospholipids (major building blocks of cell membrane)Hormones and vitamins6

HUMAN DIGESTIVE SYSTEMAlimentary CanalBasic structure of alimentary canalThe walls of the alimentary tract are formed by 4 layers of tissue:Adventitia / serosa outer coveringMuscle layerSubmucosaMucosa - lining89

Tr.Rez@SB201310

Pancreatic juicepH 7.8 8.5 Pancreatic amylase Starch + water maltose

Trypsin Protein / polypeptides + water peptides

LipaseFats + water fatty acid & glycerol

11Bile Bile salts (not enzyme)Fats fat droplets12Intestinal juicepH 7.6ErepsinPeptides + water amino acidsMaltase Maltose + water glucoseSucrase Sucrose + water glucose + fructoseLactaseLactose + water glucose + galactoseLipaseFats+ lipids fatty acids + glycerol13Digestion of Carbohydrates, Protein & LipidsDigestion of Carbohydrates, Protein & LipidsmouthOesophagus no digestion takes placeStomachSmall intestine duodenum, jejunum & ileumLarge intestine no digestion takes placeRectum 15MouthDigestion of carbohydratesSalivary glands produce salivaSaliva have 5 main components:Water moisten & soften foodLysozyme kill bacteriaMucusSodium salts provide alkaline mediumpH 6.5 7.5

Starch + water maltose

16amylase

17EsophagusTr.Rez@SB201318

Stomach

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Gastric gland secrete gastric juice that contain:PepsinRenninMucusHCl20Gastric juicepH 1.5 2Hydrochloric acid Lowers the stomach pH : pepsin activatedPepsinogen pepsinProrennin renninPepsin Protein + water polypeptides

RenninCaseinogen (milk protein) casein21Small intestineConsist ofDuodenumJejunumIleum

22Digestion of proteinTrypsinProtein + water polypeptidesPolypeptides + water peptides

ErepsinPeptides + water amino acidsPolypeptides + water amino acids23Digestion of lipidsBile salts (not enzyme)Fats fat droplets

Lipase Lipids + water glycerol + fatty acids

24Digestion of carbohydratesAmylaseStarch + water maltose

MaltaseMaltose + water glucose

LactaseLactose + water glucose + galactose SucraseSucrose + water glucose + fructose25DIGESTION IN RUMINANTS & RODENTSRuminantsHerbivore mammalsEg. Cow, goat, giraffe, deerFeed on plant - cellulose

27 Rodents..Rabbits and rats family

28Digestive System of RuminantsFeed on plant celluloseNeed cellulase to digest itBut ruminants do not produce cellulasedigestive system are specially adapted to carry out cellulose digestion29RuminantsHas a stomach with 4 chambers:RumenReticulumOmasumabomasumCarry out rumination process of regurgitating food and rechewing it 30

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32 Ruminantsthe saliva of a cow contains no salivary amylasedepend on the cellulase-secreting microorganism in its digestive system

33RUMENfirst & largest compartmentcontain bacteria that produced cellulase for the cellulose digestionfunction as the fermentation chamber

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36Organisms in rumen

37reticulumalso contains bacteria for digestioncontent of reticulum called cudregurgitation occurshas a honeycomb wall

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40 omasumreswallowed cud will be sent herelarge particle are broken down by peristalsiswater is removed

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43abomasumtrue stomach of the ruminants gastric juice containing digestive enzymes-HCl and pepsin

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45Flow of food in ruminant

mouthoesophagusrumenmouthomasumreticulumabomasumregurgitationfermentationcurdswallowswallow- H2Ochyme46

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rumenreticulumabomasumomasum48

49Digestive System of Rodentscaecum and appendix are enlarged to store the cellulase producing bacteriaFood pass the alimentary canal twicefirst as foodthen as soft faeces

50Soft and watery faeces usually produced at night

Eaten again

Pass out as hard and dry faeces during the day

51Rat digestive system

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56Rats caecum

57Flow of food in rodentsmouthoesophagusstomachcaecumanusSmall intestineswallow

Re-eat the faeces to absorb more nutrientDigest cellulose58 Eaten again? Why?? to enable the animals to absorb the products of bacterial breakdown allow rodent to recover the nutrients initially lost with the faeces

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