Biology - Animal Nutrition

Biology – Animal Nutrition Ingestion ● food is taken into the alimentary canal through the mouth Digestion ● the breakdown of large insoluble molecules into small soluble molecules that can be absorbed and assimilated by the body 1. Mechanical Digestion ● ● ● ● ● digestive juice contains enzymes increases the surface area fro the action of enzymes breakdown food into smaller pieces absence of chemical change eg. chewing by teeth, churning and peristalsis, emulsifying by bile 2. Chemical Digestion ● ● breakdown food into smaller molecules by enzymatic reaction ○ to help absorbtion presence of chemical change Stage One : Mouth Cavity ● ● ● Salivary amylase ○ starch is broken down to maltose Water ○ dissolves soluble food Mucus ○ moistens food to help swallowing ○ digested food is hence shaped into a bolus Stage Two : Swallowing ● ● Before swallowing ○ food is chewed by the teeth ○ tongue shapes the food into a bolus During swallowing ○ tongue rises to push the bolus to the back ○ bolus pushes the soft palate upwards – to prevent the food from going up to the nasal cavity ○ larynx rises, epiglottis covers the entrance to the trachea – to prevent the food from entering the trachea ○ bolus enters the oesophagus Stage Three : Peristalsis ● ● Behind the bolus ○ circular muscles contract ○ longitudinal muscles relax ○ lumen becomes smaller ○ food is squeezed forward In front of the bolus ○ circular muscles relax ○ longitudinal muscles contract ○ food slides through the lumen Stage Four : Stomach ● ● ● muscles contract food is churned up to form chyme (semi-solid) ○ a kind of mechanical digestion to increase surface area for enzyme activation gastric juice (gastric glands) ○ protease – catalyses the breakdown of proteins into peptides ○ hydrochloric acid – kill germs, provide acidic medium for enzyme to work, stop the action of amylase ○ mucus – lubricates the food, prevents stomach wall from being digested by the proteases and damaged by hydrochloric acid Stage Five : Duodenum ● ● ● Bile ○ ○ ○ secreted by liver, temporarily stored in the gall bladder released through bile duct into the duodenum bile salts – emulsifying fats into oil droplets, increase surface area for lipase to act on ○ bile pigments – products of the breakdown of haemoglobins ○ sodium hydrogencarbonate – provides an alkaline medium for pancreatic juice, neutralises the acidic chyme Pancreatic juice ○ pancreatic amylase – breaking down starch into maltose ○ proteases – catalyse the breaking down of proteins into peptides and amino acids ○ lipase - catalyses the breaking down of emulsified fats into glycerol and fatty acids ○ sodium hydrogencarbonate - makes the juice alkaline, neutralises the acidic chyme from the stomch, provides the optimum pH for the enzymes to work at Intestinal juice ○ released by glands in the walls of duodenum and ileum ○ carbohydrates – catalyse the breaking down of disaccharides into monosaccharides ○ protease – catalyse the breaking down of peptides into amino acids ○ sodium hydrogencarbonate – neutralises the acidic chyme and provides the optimum pH for the enzymes to work at Absorption ● ● ● movement of digested food molecules through the wall of the intestine into the blood or lymph by diffusion or active transport small intestine absorbs 90% of water large intestine reabsorbs water and the remaining 10% of water Structural adaptations of the small intestine ● ● ● ● ● ● ● very long greatly folded has many villi to increase the surface area for absorption thin epithelium (one cell thick) ○ shorten the distance for diffusion ○ allows rapid absorption network of blood capillaries ○ absorbed food can be carried away rapidly ○ maintain a steep concentration gradient to enhance the rate of diffusion movement of the villi ○ increases chance of contracting the food lacteal ○ transport fat molecules in food ○ fatty acids and glycerol are combined together again Villus ● ● fatty acids and glycerol recombine to form oil droplets in the walls of villi oil droplets enter the lacteal ○ pass to the main lymph vessels and eventually to the blood stream Assimilation ● the incorporation of digested substances from food into the tissues of an organism Egestion ● undigested and unabsorbed compounds are removed as feces through the anus Liver ● ● ● ● connected to three blood vessels hepatic vein ○ carries deoxygenated blood away from the liver to the heart hepatic artery ○ supplies the liver with oxygenated blood from the heart hepatic portal vein ○ carried deoxygenated blood which is rich in nutrients from the villi to the liver Roles of the liver ● ● ● ● ● regulation of the blood glucose level ○ glucose is converted to glycogen when blood glucose level is high ○ glyogen is converted to glucose when blood glucose level is low storage of glycogen, iron, fat soluble vitamins ○ stores glycogen ○ stores iron from old red blood cells ○ stores fat soluble vitamins (Vitamin A and Vitamin D) production of bile, vitamin A, heat ○ secretes bile ○ changes carotene to vitamin A ○ produces heat and helps to maintain body temperature deamination ○ deaminates excess amino acids ○ amino groups (nitrogen containing part of amino acids) are converted into urea ○ remaining parts are converted into carbohydrates or fats for the release of energy detoxification ○ changes some toxins (eg. alcohol and drugs) into harmless substances Chewing ● breakdown food into smaller pieces by teeth to increase the surface area for enzymatic reaction (physical digestion) Teeth ● ● provide mechanical digestion of food by breaking, cutting and tearing up of food 2123/2123 ○ milk teeth : without molar, 20 teeth ○ permanent teeth : no replacements for most, 32 teeth (including wisdom teeth) Structure of teeth ● ● ● ● ● Crown Enamel ○ contains 97% calcium salt, the hardest part ○ would not grow down into the root region but replaced by cement Periadontal membrance ○ fibres from the cement pass into the jawbone to anchor the teeth forming it Dentine ○ occupies a large part of the tooth is hard like bone but softer than enamel ○ living Pulp cavity ○ contains living cells which make dentine ○ contains blood vessels which supply oxygen and food ○ contains nerves which produce sensation of pain Incisors ● ● ● ● chisel-shaped sharp one root for biting and cutting of food Canine ● ● ● ● pointed and curve well developed in carnivores eg. lion one root for tearing flesh Premolars ● ● ● broad top with cusps in humans two roots for chewing, crushing, grinding food Molars ● ● ● ● similar to premolars, but larger three roots for chewing, crushing, grinding food last molars: wisdom teeth Tooth Decay ● ● ● ● ● ● oral bacteria, food debris and saliva form a plaque on tooth surface oral bacteria digest the sugar in food debris to form acid acid dissolves the enamel and makes small holes bacteria reach the holes and digest the dentine and infect the tissue in pulp cavity acid wil irritate the nerves and cause pain if not too serious, the decayed area can be drilled out and replaced with a filling Prevention of Tooth Decay ● ● ● ● ● ● ● ● ● have a balanced diet (including calcium, phosphorus, vitamin D) adding fluoride in water to strenfthen the enamel of our teeth ○ not chlorine as it is used for killing bacteria in water avoid sugary food and drinks between meals, so bacteria cannot make acid use dental floss ○ to remove food that remains between teeth form a good tooth-cleaning habit by using dental disclosing agent brush our teeth at least twice a day replace your toothbrush when it wears out do not bite hard materials have a dental check up at least once year to make sure any tooth decay is treated early Fluoride ● ● growing children can absorb fluoride in their diet ○ from toothpaste or fluoridated water becomes part of the enamel of their developing teeth and the enamel is then more resistant to tooth decay Argument of adding fluoride to public water supplies ● ● For ○ reduce the number of tooth decay (kids) ○ cannot buy fluoridated toothpaste Against ○ a form of mass medication ■ people have no choice about whether or not they want the treatment fluoride can lead to flurosis (white patches) ○ only benefit to growing children ■ if children take proper care of their teeth, fluoridation is unnecessary