Transcript
Science : Biology : DigestionScience : Biology : Digestion
Digestion refers to the breaking down of Digestion refers to the breaking down of large food molecules into smaller food large food molecules into smaller food
molecules in the body.molecules in the body.So that small food molecules can diffuse So that small food molecules can diffuse
through the walls and enter bloodstream. through the walls and enter bloodstream. Starch and proteins are large food Starch and proteins are large food
molecules that cannot pass through the molecules that cannot pass through the walls.walls.
NutrientsNutrientsBody needs energy to do work.Body needs energy to do work.Nutrients includeNutrients include– CarbohydratesCarbohydrates
Provide energy (growth, warmth, movement)Provide energy (growth, warmth, movement)– ProteinsProteins
For growth of cells and tissues For growth of cells and tissues Repair of damaged tissues. Repair of damaged tissues. Source of energy if carbohydrates and fats unavailableSource of energy if carbohydrates and fats unavailable
NutrientsNutrientsNutrients includeNutrients include– FatsFats
Provide energyProvide energyTwo times that of carbohydratesTwo times that of carbohydrates
Nutrients helpNutrients help– in our growth, in our growth, – by keeping us healthy, by keeping us healthy, – by repairing our cells and tissues, by repairing our cells and tissues, – by giving us energy.by giving us energy.
Enzymes : their roleEnzymes : their roleEnzymes are used to digest foodEnzymes are used to digest food– Carbohydrase / AmylaseCarbohydrase / Amylase
Carbohydrates to Simple sugarsCarbohydrates to Simple sugars– ProteaseProtease
Proteins to Amino acidsProteins to Amino acids– LipaseLipase
Fats to Glycerol and Fatty acidsFats to Glycerol and Fatty acids
Alimentary canal, organs and functionsAlimentary canal, organs and functions
Alimentary canal consists of the Alimentary canal consists of the – Mouth (20sec)Mouth (20sec)
Starch (carbohydrate) is digested to maltose by carbohydrase / Starch (carbohydrate) is digested to maltose by carbohydrase / amylaseamylase
– Oseophagus (10sec)Oseophagus (10sec)Walls of the alimentary canal are made of muscles which squeezes Walls of the alimentary canal are made of muscles which squeezes food along the canal.food along the canal.
– Stomach (2-6hrs)Stomach (2-6hrs)Produces gastric juice which mixes food when stomach churns.Produces gastric juice which mixes food when stomach churns.Protease in the juice breaks down complex proteins into simpler Protease in the juice breaks down complex proteins into simpler onesones
Organs joined to the Alimentary canalOrgans joined to the Alimentary canal
LiverLiver– Makes bileMakes bile
Greenish liquid which emulsifies fats, breaking them Greenish liquid which emulsifies fats, breaking them into smaller droplets, easier for lipase to digest it.into smaller droplets, easier for lipase to digest it.
Gall bladderGall bladder– Stores bileStores bile
PancreasPancreas– Creates pancreatic juiceCreates pancreatic juice
Flows to small intestine and contain enzymesFlows to small intestine and contain enzymes
Alimentary canal, organs and functionsAlimentary canal, organs and functions
Small intestine (5hrs)Small intestine (5hrs)– Produces intestinal juice which contains enzymesProduces intestinal juice which contains enzymes– Completes the digestion process with the help of Completes the digestion process with the help of
the organs joined to the alimentary canal.the organs joined to the alimentary canal.
Alimentary canal, organs and functionsAlimentary canal, organs and functionsDigestion ends at the small intestine:Digestion ends at the small intestine:–
– Small molecules of digested food passes through the small Small molecules of digested food passes through the small intestine wall, into the bloodstream surrounding it.intestine wall, into the bloodstream surrounding it.
Digested food enters bloodDigested food enters bloodDigested foodDigested food– Made of small food moleculesMade of small food molecules
Diffuse through walls of small intestineDiffuse through walls of small intestineInto blood vessels in wallsInto blood vessels in wallsCarried away by blood the rest of the bodyCarried away by blood the rest of the bodyCalled Called absorption of foodabsorption of food
– Blood carries the small food molecules to the cells Blood carries the small food molecules to the cells of the body where they can be used.of the body where they can be used.
Easier absorptionEasier absorptionFinger-like villiFinger-like villi– Provides large surface area Provides large surface area – Folds the cell membraneFolds the cell membrane
7 m-long small intestine7 m-long small intestine– Increases surface areaIncreases surface area
One-cell thick small intestineOne-cell thick small intestine– Shortens distance between wall and bloodstreamShortens distance between wall and bloodstream
Alimentary canal, organs and functionsAlimentary canal, organs and functions
Alimentary canal consists of theAlimentary canal consists of the– Large intestine and anus (24hrs)Large intestine and anus (24hrs)
Undigested food reaches the large intestineUndigested food reaches the large intestineLots of water is removed and taken back into the bodyLots of water is removed and taken back into the bodyPass out through anus as faecesPass out through anus as faeces
Summary : Digestion of foodsSummary : Digestion of foodsNutrients in foodsNutrients in foods– Carbohydrates and fats are used for respiration and as Carbohydrates and fats are used for respiration and as
sources of energy.sources of energy.– Proteins are used for growth and the repair of body Proteins are used for growth and the repair of body
tissues.tissues.– Starch and glucose are two kinds of carbohydrates.Starch and glucose are two kinds of carbohydrates.
Why digestion is neededWhy digestion is needed– Only small molecules are able to pass through cell Only small molecules are able to pass through cell
membranes into cells.membranes into cells.– Starch, fat and protein molecules are too large to pass Starch, fat and protein molecules are too large to pass
through.through.
Summary : Digestion of foodsSummary : Digestion of foodsMeaning of digestionMeaning of digestion– Digestion is the breaking down of large food molecules in Digestion is the breaking down of large food molecules in
the body into small food molecules.the body into small food molecules.– The small food molecules are: glucose (from starch), The small food molecules are: glucose (from starch),
amino acids (from proteins) and glycerol and fatty acids amino acids (from proteins) and glycerol and fatty acids (from fats).(from fats).
– Digestion takes place by the action of enzymes.Digestion takes place by the action of enzymes.
Summary : Digestion of foodsSummary : Digestion of foodsThe alimentary canal and digestionThe alimentary canal and digestion– MouthMouth
Digestion of starch begins here.Digestion of starch begins here.
– StomachStomachDigestion of proteins begins here.Digestion of proteins begins here.
– Small intestineSmall intestineMost digestion takes place here.Most digestion takes place here.Digestion of starch and proteins is completed here.Digestion of starch and proteins is completed here.Digestion of fats takes place only in the small intestine. Digestion of fats takes place only in the small intestine. Absorption of digested foodAbsorption of digested foodThe small, digested food molecules are absorbed into the The small, digested food molecules are absorbed into the bloodstream through the walls of the small intestine.bloodstream through the walls of the small intestine.The villi of the small intestine increase the surface area for faster The villi of the small intestine increase the surface area for faster absorption of small, digested food moleculesabsorption of small, digested food molecules..
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