Biology 103 - Main points/Questions 1. Why do you need to eat? 2. What does your body do with this food? 3. What is in plant food? What do you remember about human circulation? 1. Name the structure 2. Where is blood in this structure headed? 3. Blood in this structure has just come from where? 1. Aorta 2. Blood is headed out to the body 3. Blood here is returning from the body (this is the right atrium) Organisms’ two basic needs Source of organic molecules • Either build your own (autotrophs) • Or take from other organisms (heterotrophs) Energy source • Either chemical (called chemotrophs) • Or light (called phototrophs) Most organisms are chemoheterotrophs (Fungi, animals, many protists & bacteria) or photoautotrophs (plants, many protists & bacteria) We are Chemoheterotrophs so… • We get energy and complex carbon molecules (monomers) from other organisms • But often we actually get polymers – what are these? Polymers are chains built of smaller “monomer” pieces • These polymers are specific to the organism that made them but the monomers are more generic. • How can we break these polymers apart to get access to the monomers? Hydrolysis Your digestive system frees up monomers from food (hydrolysis). In vertebrates these monomers are moved throughout body by circulatory system. As always… exchange happens between cells and the interstitial fluid that surrounds them! Molecules come in 4 categories… do you remember them? (macromolecules) • Carbohydrates • Nucleic acids • Proteins • Lipids Their jobs are… Molecules come in 4 categories… do you remember them? (macromolecules) • Carbohydrates Energy storage (short, medium, long) & structure • Nucleic acids Information storage, short term energy storage (ATP) • Proteins Structure, enzymes, receptors, signaling • Lipids Long term energy storage, barriers, signaling The food pyramid and other dietary guidelines... sparingly milk, yogurt, meat, poultry, cheese fish, beans, eggs, nuts 2–3 servings 2–3 servings vegetables fruits 3–5 servings 3–5 servings bread, cereal, rice, pasta 6–11 servings Fig. 31.1 ... try to make sure people are getting the essential nutrients they need but not to many calories. Nutrition Labels provide important information like... Number of Calories per serving % of various macromolecules And % of some the the key vitamins and minerals So how do animals process food? Four stages of digestion • Ingestion Ingestion in a python! (chew your food!) Four stages of digestion • Ingestion • Digestion (mechanical and chemical) – Mechanical allows more surface area for... – Chemical - the actual breakdown of polymers into monomers (this is hydrolysis!) Four stages of digestion • Ingestion • Digestion (mechanical and chemical) • Absorption – Once digested into monomers and other nutrients you must absorb the molecules your body needs Four stages of digestion • Ingestion • Digestion (mechanical and chemical) • Absorption • Elimination - indigestible or unwanted material is eliminated from the digestive tract... nuff said Small molecules Pieces of food Chemical digestion Nutrient Mechanical (enzymatic hydrolysis) molecules digestion enter body cells Food Undigested material 1 Ingestion 2 Digestion 3 Absorption 4 Elimination In simple animals digestion occurs in one large cavity and there is only one opening (meaning only one meal at a time) These organisms have no specialized regions for different digestion and rely on diffusion to spread nutrients around • Complete tracts allow specialization • Food passes each region in order • Multiple meals at once ok The digestive system must also interact with other systems to move nutrients from the site of digestion to the site of need. These organisms use a circulatory system to move fluids throughout the organism. Although cells still use diffusion over short distance (the local environment) The human digestive system has several specialized regions Each one with a specialized function We will look at several specialized Mouth regions of the digestive tract in humans including: Esophagus 1. Mouth 2. Esophagus Stomach 3. Stomach Small intestine 4. Small & Large Intestine Large intestine Rectum Anus Salivary We will also look at several glands Mouth specialized “helper” organs/structures: Esophagus 1. Salivary glands Gall- 2. Liver bladder Stomach 3. Pancreas Small Liver intestine 4. Gall bladder Pancreas Large intestine Rectum Anus Tour of the Digestive system: Start in the mouth Fig. 31.8 Diagram of generalized vertebrate dentition Tour of the Digestive system: Start in the mouth • Lots of mechanical digestion (chewing) • Add saliva – moisten/dissolve food • Saliva includes amylase – what is this? • Starts carbohydrate digestion • What happens when you swallow? We us the same tube for breathing and eating at first (the pharynx). Food we swallow must pass over the opening to the trachea (the glottis) A flap of tissue (the epiglottis) covers the glottis as we swallow to prevent choking. food pharynx epiglottis glottis esophagus larynx (a) Before swallowing epiglottis (folds over) food (enters esophagus) larynx (moves up) (b) During swallowing Tour of the Digestive system: Next stop is the esophagus • Muscular tube that transports food to stomach • What kind of muscle do you think? Contraction of the muscle lining (called peristalsis!) pushes food down the tube Figure 31.12 The esophagus and peristalsis Tour of the Digestive system: Next stop is the stomach More smooth muscle causes stomach to “churn” food (more mechanical digestion) • Food is converted to an acidic soup called chyme by the churning and the addition of gastric juice from cells that line the stomach • Protein digestion starts here as enzymes secreted into the chyme start hydrolyzing the proteins you eat Tour of the Digestive system: Next stop is the small intestine • Controlled by a sphincter • First part is called the duodenum – Mixes chyme with other secretions from: – Pancreas, Liver, Gall bladder and the intestine itself Digestion in the Small Intestine • The small intestine is the longest section of the digestive system • It is the major organ of both chemical digestion and absorption • Each class of macromolecule needs different digestive enzymes Digestion takes place in several different places depending on the type of molecule. Carbohydrate digestion Polymers Disaccharides (starch, glycogen) (sucrose, lactose) Oral cavity, pharynx, Salivary amylase For example: esophagus Smaller polysaccharides, maltose Carbohydrate Stomach digestion starts in Polymers the mouth, stops in Lumen of small intestine Pancreatic amylases the stomach (why?) Maltose and other disaccharides then continues in Disaccharidases the small intestine. Epithelium of small intestine (brush border) Monosaccharides Absorption in the Small Intestine • Has a huge surface area - Why? • The enormous surface greatly increases the rate of nutrient absorption • The sm. intestine also contains a large network of blood vessels and small lymphatic vessels The large blood flow allows your body to constantly flush newly absorbed nutrients out of the intestine to the rest of the body. Figure 31.14 The small intestine Absorption in the Large Intestine • A major function of the colon is to recover water that has entered the alimentary canal • Wastes of the digestive tract, the feces, become more solid as they move through the colon • Feces pass through the rectum and exit via the anus Lactose Intolerance • As humans age many lose the ability to digest the milk sugar lactose • Lactose is a disaccharide formed from a glucose and a galactose Symptoms of Lactose Intolerance Present after a meal high in lactose: • Lactose present in stool • Diarrhea • Abdominal pain and cramping Questions about Lactose Intolerance 1. Where is lactose normally digested? 2. Why is lactose uncommon in the stool of people that are not intolerant – where does it go? 3. Diarrhea is a condition where excess water is mixed with undigested food. What part of the digestive system is normally responsible for removing excess water? 4. Pain and cramping can result from bacterial digestion of lactose – where are bacterial located in your digestive tract? Carbohydrate digestion Polysaccharides Disaccharides Oral cavity, (starch, glycogen) Salivary amylase (sucrose, lactose) • Lactose usually pharynx, esophagus Smaller polysaccharides, digested in small maltose intestine Stomach • If not it stays in & Polysaccharides Lumen of Pancreatic amylases – Bacteria eat & small intestine Maltose and other – draws water… disaccharides Disaccharidases Epithelium of small intestine Monosaccharides Incisors Natural selection has adapted the Molars Canines Premolars digestive system to (a) Carnivore different diets But notice that the basic pattern of (b) Herbivore teeth is the same – Homology! (c) Omnivore Fungi – the other chemoheterotrophs • all fungi perform external digestion • they secrete digestive enzymes into their surroundings and then absorb back into their bodies any organic molecules • many fungi are able to break down the cellulose in wood • some fungi are carnivores – for example, oyster fungus attracts nematode worms and then feeds upon them • Fungal hyphae spread throughout their food source by growing • The resulting mat is called a mycellium • Because hyphae are so thin they have very large surface area Photoautotrphs • Generate their own organic molecules from carbon dioxide & light energy • Use photosynthesis to capture light energy and CO2 – this builds complex molecules • Still need a source of nutrient atoms Magnesium deficiency in a tomato plant Nutrient Source Major function Carbon CO2 in Build organic atmosphere compounds Oxygen CO2 in Build organic atmosphere compounds Hydrogen H2O in soil Build organic compounds Nitrogen Nitrogen Build Proteins & compounds in soil Nucleic acids Phosphorus Phosphate in soil Build nucleic acids & phospholipids Potassium Potassium in soil Water balance, stomatal opening So a nutrition label for a plant might look like this. With information on amounts of • CD28020.GIF commonly needed nutrients. Where is the information on calorie content? Where do plants get nutrients? • Plant roots absorb water that has nutrients dissolved in it • High surface area in the root helps absorb • Plants can control what makes it into the stele. root hairs epidermis root hair cortex endodermis of cortex pericycle xylem phloem vascular cylinder apical meristem root cap • Plant root cross section • Zoom in on the cylinder cortex endodermis xylem phloem • Endodermis is key region that controls access to the xylem • Wax in the cell wall creates a barrier called the Casparian strip • Forces fluid through endodermal cells Absorption rates depend on surface area - so areas adapted for high absorption • 30 have high surface areas. • CD280931.JPG • Copyright Biological Photo Service Some roots are covered with fungal hyphea. Mycorrhizal Fungi can drastically increase a plant • CD28100.GIF roots surface area and access to nutrients!
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