Digestion: Chapter 11(pg ) Digestion: the breaking down of macromolecules into simple compounds that can be absorbed. Chemical Foundations of Digestion All organisms regardless of size or complexity have some method to obtain the essential nutrients they need for survival Food= energy Hetertrophs: obtain energy by breaking down chemical bonds of organic molecules. Humans are ingestive heterotrophs Autotrophs: synthesise organic molecules from inorganic forms to obtain energy. Examples water and carbon dioxide Pathway of nutrient compounds: Digestive system blood cells Molecule must be small and soluble. Nutrients Any substance used by the human body to maintain homeostasis Essential nutrients The basic raw materials organism need to make their own structures, perform functions and obtain energy for survival Essential = needed and must be obtained from organisms diet 6 Essential Nutrients Water Carbohydrates Proteins Fats Minerals Vitamins Your body functions best when these essential nutrients are present in correct proportions. A diet that satisfies this is called balanced diet 1. Water Major role in the body is to act as a solvent Important for chemical reactions (hydrolysis) Needed for respiration (alveoli) Needed for movement of material (osmosis) Main source: food and liquids CARBOHYDRATES Carbohydrates: Consist of Carbon, hydrogen, oxygen Basic unit of carbohydrate is called a monosaccharide ( simple sugar) Examples of monosaccharide's are : glucose, fructose, and galactose Disaccharide: 2 monosaccharide's bonded together. Ex. Maltose Polysaccharide: many monosaccharide's bonded together. Ex: Cellulose, glycogen, starch Function: provide a source of energy. Can be held in energy stores: plants = starch animals= glycogen Excess carbohydrates are converted to fat and stored Food sources: glucose rice pasta etc How are monosaccharide's joined to make di and polysacchardies? Dehydration Synthesis Reaction This is a reaction in which two small molecules are joined together to make a larger molecule by removing (dehydrating) water Dehydration reactions happen in fats and proteins as well Ex: Glucose (monosaccharide) + Glucose(monosaccharide) = Maltose(disaccharide Hydrolysis Reactions This is a reaction where larger molecules are broken/split into smaller molecules by addition of water Hydrolysis reactions happen whenever large molecules such as polypeptides and lipids are broken down into smaller molecules Energy is released when the bonds of the large molecule are broken in the process of creating smaller molecules Enzymes Speed up hydration and dehydration (i.e. digestion) Function is affected by Temperature pH Inorganic micronutrients Enzyme types: General Type Specific example What it breaks down What it produces CarbohydraseCarbohydratesmonosaccaride s maltase MaltoseGlucose Lactase Salivary amylase LactoseGlucose + galactose Protease Proteins Amino acids Pepsin Protein Peptides (chains of amino acids) LipaseLipids / fats Glycerol + fatty acids Pepsin : made in stomach Salivary Amylase: mouth. All others: made in small intestine. Proteins Made up of strings of amino acids called peptides Amino acids : The basic building blocks of a protein Humans have 20 amino acids that make up all the proteins in the body 8 amino acids are essential meaning they have come from their dirt Proteins are made up of peptides created when more than one amino acid joins together Dipeptide= a combination of 2 amino acids Polypepetide= a combination of many(poly) amino acids Function: include, cell growth and repair, enzymes in your body are all proteins( act in metabolism) and can supply energy Food sources: meat, milk, poultry, fish, eggs, cheese, etc Polypeptides combine = prote in 8 Essential Amino Acids 20 amino acids exist We make all but 8 The essential 8 come from diet (eggs, legumes, meat, dairy, nuts. Complete proteins: contain all 8 essential amino acids Fats/lipids Contains fats, waxes and oils Structure of a Lipid Made up of 3 Fatty acids + Glycerol Function: Provides a source of energy, insulating the body from the cold and protecting organs from injury. Also used for Cell Membrane(Cholesterol) Building block In cell membranes, hormones, Make energy, store minerals and vitamins' Conduct nerve impulses Food sources: margarine, butter, meat, cheese nuts, eggs, etc. Minerals Inorganic compounds needed in small doses. Function: carry out certain chemical reactions and help to maintain acid base balance within the body Readily absorbed into bloodstream Used in : Bones, cartilage, haemoglobin, hormones, enzymes, vitamins, metabolic reactions Ex. Iron, magnesium, calcium, potassium. Vitamins Required in small amounts There are two types of Vitamins Fat soluble Vitamins - dissolve into fats Vitamins A,D,E and K are Fat soluble Water Soluble Vitamins - dissolve into water Vitamins B and C are water soluble These vitamins need to be replaced daily Main-function: Co-enzymes: help enzymes function (Enzymes break down complex molecules) Vitamins Vit A: antioxidant Found in fruit, vegs, milk Lack of : night blindness, poor bone growth Vit D Found in milk, fish oil, our skin (with sunlight) Lack of: weak brittle bones Night blindness (lack of Vit A) Vitamin D deficiency affects bone growth. Vit E: Antioxidant Found in green vegetables, nuts, grains. Lack of: unknown/undecided. Vit K Used in blood clotting/coagulation Found in green vegetables, bananas. Lack of: bruises, bleeding Vit C Collagen synthesis (cartilage, skin, bone..) Found in citrus fruits, sunlight. Lack of = scurvy (skin haemorrhaging, weak bones, sore gums, poor healing,...) Human Digestive System Function of Digestive system Break down food into small useful substances that can be absorbed into the circulatory system where nutrients are transported to individual cells Digestion The process of breaking necessary substances into smaller molecules so that they can be absorbed into the body Digestion occurs in the Alimentary Canal, a continuous tube beginning at the mouth and ending at the anus Structure of Human Digestive System Digestion:2 types Mechanical: Initial stage of physically breaking down food into smaller pieces. Occurs mainly in the mouth where teeth chew food and tongue manipulates it Some mechanical digestion occurs in the stomach(rugae) Chemical: Separation of food into molecular componds by chemical means Process begins in the mouth with the secretion of salvia which contains the digestive enzyme amylase Chemically breaking food down continues through the stomach and is completed in the small intestine. Both allow nutrients to be absorbed (24-33 hours after eating) Mechanical and chemical digestion act together to speed up the digestion process. Mechanical digestion aids chemical digestion by exposing more food particles to digestive enzymes Major Organs and Glands involved in the Digestive process Mouth Digestion begins here Contains teeth used for tearing food apart (mechanical digestion) Molars, premolars, canine, incisors Fig 11.4 pg 351 Contains tongue that moves food into position for digestion Contains Salivary glands that secrete Salvia Salivary Glands Saliva Glands Release saliva to lubricate food Contains the enzyme Salivary Amylase that converts Starch into Maltose StarchMaltose Saliva Glands Teeth Tongue Muscle Moves food, tastes (sweet, sour, bitter and salty) Has papillae which house taste buds. Uvula Dangles in back of mouth over tongue Prevents food from moving up the pharynx Digestion in the Mouth Food enters the mouth where teeth begin breaking it down. The salivary glands secrete Mucin which makes the food slippery and helps prepare it for further digestion. Salivary Amylase breaks down starches into maltose At the same time the tongue shapes the food into a round ball called a Bolus. Swallowing ( an involuntary response) is initiated when the food touches the back of the tongue. Food passes into the esophagu s Esophagus Hollow tube leading from the mouth to the stomach No digestion occurs here Lined with circular and longitudinal muscles that undergo a series of muscle contractions called Peristalsis Peristalsis: series of muscle contractions that forces food through the alimentary canal Contains the Esophageal Sphincter at the lower end of the esophagus Function of esophageal sphincter: controls amount of food entering stomach Food Movement Peristalsis Wave like muscle contractions of the digestive system Rhythmical Segmentation Contractions of the small intestine that mixes the partially digested food it holds. Stomach Muscular J-shaped sac like organ Protein digestion occurs here Has two distinct regions: Cardiac region: Region of stomach closest to the heart Pyloric Region: lower portion of stomach (closest to the feet) Contains folds of smooth muscle called Rugae Rugae: folds of muscle in the stomach that increases the surface area for digestion and also contract to break food into smaller pieces in a process called churning Churning: contractions of muscles in the stomach in order to break up food(mechanical digestion) The stomach secretes Gastric Juice that digests protein Gastric Juice: fluid in the stomach composed of HCl (hydrochloric acid), water and Pepsinogen Pepsinogen: Inactive enzyme in the stomach that changes into pepsin in the presence of HCl Pepsin: enzyme that breaks proteins into long polypeptides Proteins pepsin Long polypeptides Contains the pyloric sphincter at the bottom of the stomach at the entrance of the small intestine. Pyloric sphincter: ring of muscle that controls the amount of food entering the small intestine Stomach :note the rugae(folds) Sphincters: Esophageal sphincter: at top of stomach Prevents food from going back up esophagus Pyloric sphincter Bottom of stomach Slows/stops food from entering duodenum until well mixed Digestion in the Stomach A bolus enters the stomach via the cardiac sphincter Gastric juices secret juice that aid in the digestion of proteins pepsin changes proteins into long polypeptides when digestion in the stomach is finished, an acidic soupy liquid remains called chyme Chyme enters the small intestine by passing through the pyloric sphincter Small Intestine Most important organ of the digestive tract Approximately 6 metres long Site of most chemical digestion and absorption of food molecules into the blood Subdivided into 3 parts Three parts of Small Intestine: duodenum Short wide, first section Receives bile from gallbladder and secretions from pancreas Site of chemical digestion Site of final carbohydrate protein and lipid digestion Contains fold with finger like projections called villi (microvilli) that serve to increase the surface areas for digestion Small Intestine walls: villi (villus): Small finger-like projections on the folds of the small intestine that absorb nutrients. Increases surface area 30X Contains blood and lymph to absorb/distribute nutrients Have lacteal vessels to absorb large fat molecules and send to the lymphatic system. Lacteal is surrounded by blood vessels that absorb amino acids and monosaccharide's into the blood Microvilli: Brush like projections on the villi Increase surface area 600X Jejunum 2.5 meters long Contains folds and intestinal glands in order to Break down remaining proteins and carbohydrates. Ileum: 3m long Contains few and very small villi Absorbs remaining nutrients, pushes undigetsed material into large intestine Small Intestines: Large Intestine Divided into different structures Caecum, colon, rectum, anus Much shorter than the small intestine by a valve Caecum is a saclike structure at one end of the small intestine where the appendix is found where small intestine meets large intestine Large Intestine Colon (ascending, transverse, descending) main portion of the large intestine where water and dissolved minerals are absorbed from undigested food. Removes water and minerals Contains intestinal bacteria that help with breakdown undigested material to provide more nutrients and can produce Vitamins B-12 and K the mass of indigestible material in the large intestine is known as Feces Feces passes through the rectum and out the body through the anus The anus contains rings of muscle called the anal sphincter that allow the body to control timing of elimination to some extent Parts of colon Ascending Colon- portion of colon on the right side of the body Transverse Colon- portion of colon going across the abdomen Descending Colon portion of colon on the left side of the body Rectum Lower portion Hold waste until body is ready to void. Anus Has rings of muscles(anal sphincter) Allows timing of waste elimination Large Intestine: Pancreas Located under the stomach Makes enzymes to digest carbohydrates, fats and proteins Secretes neutralization agent (sodium bicarbonate) into duodenum to increase pH so enzymes can start working. Enzymes and Chemical Secretions of the Pancreas Name of enzyme /SecretionFunction Bicarbonate ionsNeutralize acidity of chyme Provide a basic Ph so enzymes can work Pancreatic AmylaseBreak polysaccharides into monosaccharide's Pancreatic LipaseBreak lipids into fatty acids and glycerol Trypsin/ ChymotrypsinBreak polypeptides into shorter peptides Pancreas relative to the Stomach Other related organs : Liver Makes bile from cholesterol which h aids with digestion of fats Converts unused glucose into glycogen that is stored in liver Recycles RBCs and filters toxins from blood. Bile Green liquid substance made from cholesterol stored in the gallbladder. released into duodenum via bile duct. Function: Emulsifies (breaks up) fats into small droplets called micelles to increase surface area for digestion Activates lipase Liver And Stomach Gall Bladder Structure located under the liver Stores bile Pathway of Food through the Human Digestive System Mouth Esophagus Esophageal Sphincter Stomach Pyloric Sphincter Small Intestine Large Intestine Anus Hormonal Control Of Chemical Digestion 1. Gastrin Stimulates HCL and pepsin production in stomach 2. Secretin Made in duodenum Causes pancreas to release sodium bicarbonate. 1. CCK Cholecystokinin Stimulated release of bile from gallbladder and enzymes from pancreas 2. Enterogastrone Made in duodenum Slows peristalsis and acid secretions Digestive Disorders Problems with the digestive system can range from minor inconveniences to a major impediment to a normal life We will discuss the following disorders Ulcers Gall stones Ileitis Colitis Anorexia Nervosa Bulimia nervosa Ulcers healing sores in the lining of the stomach and intestines Causes Acids: causes breakdown of mucus layer of stomach and intestines Helicobacter pylori; an acid resistant bacteria, attaches to stomach wall, stops mucous production in the area, ulcer forms. Lifestyle: Smoking, caffeine, alcohol, stress, all reduce mucous production, increase stomach pH and slow lining repairs. Ulcer Treatments Medication (antacids, antibacterial drugs) to reduce acid production Surgery Lifestyle changes Gallstones Hard masses that form in the gall bladder. Cholesterol in the gallbladder precipitates out as a solid forming crystal. Causes: diet, obesity, heredity, alcohol Treatments Medication Lithroscopy :ultrasound shockwaves break up the stone Diet( lower fat content in diet- reduce cholesterol Surgery( remoal of gall bladder Inflammatory bowel disease (IBD) Inflammation of the intestines Crohns (ileitis) Colitis Crohns Disease (Ileitis) inflamed and/or ulcerated intestine, usually the ileum (last part of small intestine) causing much pain Frequent bowel movements, pain, fever, weight loss. Causes Relatively unknown Does run in families Treatment anti-inflammatory drugs Surgery (remove infected section) No cure Colitis Inflamed/ulcerated colon. Affects the innermost lining of the colon Abdominal cramps, bloody feces, weight loss, diarreha.. Causes Relatively unknown Does run in families Treatment Anti-inflammatory drugs(reduce swelling) No cure Surgery( remove part or all colon, replace with colostomy bag) Eating Disorders: Anorexia Nervosa Fear of weight gain Distorted self image (psychological disorder) result in physical problems Constipation Lose weight which causes a lack of nutrients to the cells of the body Low Blood pressure Heart problems, Organs shut down (ex kidney, liver..) Menstruation stops, hair and teeth lose, skin dries out, internal organs shut down, digestive tract stops working Etc Treatments Hospitalization and forced feeding is often necessary Psychological therapy which includes behavioral and family therapy Most treatment is unsuccessful and the person dies Bulimia Episodes of binge eating and purging and/or laxative use. Individuals concerned with body shape and mass so they diet restrictively Loose control of diet and consume large amounts of forbidden food Very dangerous because it affects several organs Causes damage to heart, kidneys, esophagus and teeth Associated with anorexia and obesity Psychological disorder Treatments: Psychological therapy Antidepressants. Symptomatic treatment for physical problems. Results in physical problems: Bad teeth, hair loss, organ problems, perforated/ulcerated esophagus and mouth.