mammalian nutrition

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Mammalian Nutrition. Chapter 11. Requirement for food. A balanced diet must contain: - Fats - Proteins - Carbohydrates - Vitamins & Minerals All foods contain the elements Carbon (C), Hydrogen (H) & Oxygen (O). Protein also contains Nitrogen (N) - PowerPoint PPT Presentation


Mammalian Nutrition

Chapter 11Mammalian NutritionRequirement for foodA balanced diet must contain:- Fats- Proteins- Carbohydrates- Vitamins & MineralsAll foods contain the elements Carbon (C), Hydrogen (H) & Oxygen (O). Protein also contains Nitrogen (N)Age, gender, body size, occupation - all affect food requirements

FatsEnergy-rich (twice as much as energy as carbohydrates)Made up of 2 components - glycerol & 3 fatty acid moleculesFat is insolubleStored around the organs to provide a layer of padding & insulation

carbohydratesGlucose (C6H12O6) is the most common simple sugarGlucose molecules (soluble) can join to form larger carbohydrates (insoluble)In animals glucose stored as glycogen (in liver)In plants stored as starch - converted to cellulose (in cell walls)- indigestible (forms roughage in diet)

proteinMade up of amino acidsProtein is used for tissue growth & repairHuman body cannot store excess protein - (minimum daily intake 80g)Excess protein is used for energyStructural proteins are only ever used for energy in an emergency (starvation)

vitamins2 types : Fat soluble (e.g. A & D)Water soluble (e.g. B & C)Work as coenzymes to promote chemical reactionsAre constantly re-used, so only required in small quantities

mineralsChemical components of food required for many functions in the body Calcium (dairy foods): - hardening bones & teeth Iron (meat & eggs): - structural component of haemoglobin Sodium/Potassium (in most foods):- for muscle contraction and nerve impulses

Food testsStarch - will turn iodine solution blue/blackProtein - will turn Biuret reagent lilacSimple Sugar- will turn heated Benedicts solution orangeFat- produces a translucent stain on white paper- OR red layer with Sudan III

Need For DigestionFood is needed for cells:Give fuel for energyProvide building materials for - growth- repair- fighting infection (antibody production)Digestion breaks down large insoluble molecules - into small soluble moleculesThese molecules can then be absorbed into the bloodstream

Alimentary CanalA long tube running from mouth to anusHas several associated organs connected to it e.g. liver, pancreas, salivary glandsThese organs are connected by tubes or ducts

Pharynx (throat)OesophagusMouth & Salivary GlandsIn the mouth food is broken down in 2 ways:mechanically - by chewing and grinding of teethchemically - by amylase, from the salivary glands (starch into maltose)saliva also contains mucus- keeps the mouth & food lubricated

Oesophagus & PeristalsisOesophagus is a muscular tube- connects the mouth to the stomachIts wall is lined with circular muscleContraction & relaxation of this muscle pushes food alongThis is known as Peristalsis

StomachA muscular sac, lined with 2 types of muscle- longtitudinal & circular muscleMuscles contract & relax- helps churn & mix food with digestive juices2 sphincters at either end - hold the contents inside

Gastric GlandsFound in the inner lining of the stomach- Mucus-secreting cells mucus sticks to the stomach lining - protects it from acid and digestive enzymes- Acid-secreting and enzyme-secreting glands Acid lowers pH- converts inactive pepsinogen into pepsinPepsin can then converts protein into peptides (amino acids)

Associated OrgansLiver:- produces bile - processes products of digestionGall Bladder:- stores bile- passes it into small intestine via bile duct- bile helps emulsify fatPancreas:- produces amylase, trypsin, & lipase

Small IntestineWhere the majority of digestion (& all absorption) takes placeFood moved along by peristalsis Food broken down by digestive enzymes- e.g. amylase, lipase, trypsinDigestion products absorbed into the bloodstream

Small Intestine - StructureVery longFolded inner lining -covered in finger-like villi The epithelial cells lining the villi are folded into microvilli Provides a very large surface area for food absorptionLining is only 1 cell thick

Small intestine - absorptionHas a very dense network of blood vesselsEach villus has a blood capillary and lactealGlucose & amino acids pass into the capillary Fat digestion products pass into the lacteal Vitamins & minerals also pass across

Fate of absorbed materialsAmino acids & glucose:- passed to the liver through the hepatic portal veinGlucose : - converted into glycogen & stored- released into circulation as an energy sourceAmino Acids :Some used for growth & repairExcess broken down into urea (deamination)- removed by kidneysFat - passed via the lymphatic system into the blood- some used as an immediate energy source- excess fatty acids & glycerol are converted into fat and stored in the tissuesVitamins & minerals - carried by the blood to the cells that need them

Large IntestineUndigested material, bacteria & dead cells pass into the large intestineAny excess water is reabsorbedThe remaining faeces are eliminated - by passing to the rectumFaeces are finally expelled through the anus