Nutrition Overview - Nutrition – Adaptation and Needs •...

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Unformatted text preview: Nutrition – Adaptation and Needs • P ro ka ry o tic nutritio na l a nd m e ta b o lic d ive rs ity • Nutritio na l re q uire m e nts o f p la nts • Nutritio na l re q uire m e nts o f a nim a ls What do organisms require in order to survive? How are essential nutrients acquired? How many adaptations are there? Prokaryotes Have Exploited Many Metabolic Possibilities • Anaerobic versus aerobic metabolism: • Obligate anaerobes live only in the absence of oxygen. Oxygen is toxic to them. oxygen. • Facultative anaerobes can shift between anaerobic and aerobic modes. • Some cannot use oxygen but are not damaged Some by it (Aerotolerant anaerobes) by • Obligate aerobes are unable to survive for extended periods in the absence of oxygen. extended Four Nutritional Categories Four The four nutritional categories of organisms The include: include: 1. 2. 3. 4. Four Nutritional Categories Four Photoautotrophs Photoautotrophs Photoautotrophs are photosynthesizers. photosynthesizers. • Photoautotrophs use light for energy and carbon dioxide as a Photoautotrophs light carbon carbon source. carbon • Cyanobacteria use chlorophyll a (same chlorophyll as plants) and produce oxygen as a by-product. oxygen • Other photosynthetic bacteria use bacteriochlorophyll. Other bacteriochlorophyll. These bacteria do not produce O2. do • Some produce particles of pure sulfur, because H2S is is used instead of H2O as an electron donor. used • Bacteriochlorophyll uses longer wavelengths than Bacteriochlorophyll chlorophylls. This longer wavelength of light penetrates farther into water and is not absorbed by plants. plants. P h o to s y nth e tic Ba c te ria • Cells of purple sulfur bacteria store granules of sulfur that they produce via anaerobic photosynthesis. • Ulva, a green alga, absorbs no light of wavelengths longer than 750 nm. Purple sulfur bacteria can conduct photosynthesis using the longer wavelengths that pass through the algae. Algae absorb strongly in the blue and red regions shading bacteria living below Purple bacteria can use long wavelengths of light which the algae do not absorb Cyanobacteria • C y a no b a c te ria , unlike o th e r b a c te ria , p h o to s y nth e s ize us ing th e s a m e p a th wa y s p la nts us e . • T h e y h a ve e la b o ra te inte rna l m e m b ra ne s y s te m s c a lle d la m e lla e o r th y la ko id s • C y a no b a c te ria m a y live s ing ly o r in c o lo nie s o f d iffe re nt s h a p e s (m a ts , b a lls ) • Ma ny fix nitro g e n • Le a c h e d P h o s p h o rus a nd o th e r nutrie nts fro m la nd c a n c a us e m a s s ive m ultip lic a tio n o f c y a no b a c te ria (b lo o m s ) Cyanobacteria were responsible for the accumulation of oxygen in Earth’s atmosphere---life changed forever when this happened! Cyanobacteria Cyanobacteria Some filamentous colonies specialize into 3 cell types: – Vegetative cells, which photosynthesize which – Spores, resting cells that can develop into new filaments – Heterocysts, cells adapted for nitrogen fixation Spore (a “resting” cell) Heterocyst A thick wall separates the cytoplasm of the nitrogen-fixing heterocyst from the surrounding environment Vegetative Cells Photoheterotrophs Photoheterotrophs • Photoheterotrophs use light as a source of Photoheterotrophs energy but must get carbon from other organisms. organisms. • They can use carbohydrates, fatty acids, and They alcohols for carbon. alcohols • Purple non-sulfur bacteria are an example of a Purple photoheterotroph. photoheterotroph. Chemoautotrophs Chemoautotrophs Chemoautotrophs obtain energy from oxidizing Chemoautotrophs inorganic substances. inorganic Chemoautotrophs use some of the energy to fix Chemoautotrophs carbon dioxide. carbon Some use pathways to fix CO2 identical to those of the Calvin cycle in photoautotrophs. of Some use ammonia as the chemical source of Some energy; others use hydrogen gas, hydrogen sulfide, sulfur, or methane. sulfide, Some deep-sea ecosystems are based on Some chemoautotrophic prokaryotes and they form the basis for a food chain that includes giant worms, crabs, and mollusks. Chemoheterotrophs Chemoheterotrophs • Chemoheterotrophs typically obtain energy Chemoheterotrophs and carbon atoms from one or more organic compounds. • Most known bacteria and archaea are Most chemoheterotrophs, as are all animals, fungi, and many protists. and Prokaryotes in Their Environments Prokaryotes Many prokaryotes live in or on other organisms, with neutral, beneficial, or harmful effects e.g. bacteria in digestive tracts, Examples: Cows cannot produce the enzyme cellulase and so depend on prokaryotes in their gut for cellulose digestion gut Humans rely on vitamins B12 and K produced by Humans bacteria living in our gut bacteria Any other examples you can think of? A Minority Of Bacteria Are Pathogens Minority • Invasiveness and Toxigenicity are important factors in Invasiveness infections infections – Corynebacterium diptheriae, (causes diptheria) low (causes invasiveness , multiplies only in throat, but high toxigenicity, affects entire body toxigenicity, – Bacillus anthracis (anthrax) low toxigenicity but very invasive invasive • Some produce endotoxins - lipopolysaccharides, Some endotoxins components of bacterial outer membrane, released when bacteria burst, rarely fatal, cause fever, vomiting, diarrhea. E.g. E.coli, Salmonella E.coli Salmonella • Others produce often highly toxic exotoxins – released by Others multiplying bacteria, move through body, often fatal, Tetanus (Clostridium tetani), botulism (Clostridium Tetanus Clostridium botulinum), cholera (Vibrio cholerae), plague (Yersinia botulinum), cholera Yersinia pestis), E. coli strain 0157:H7. pestis), E. How would natural selection favor bacteria producing toxins? How does a stationary organism (a plant) find nutrients? plant) • Sessile plants grow in search of new resources. • As the plant root grows through the soil it As mines minerals and water. mines • Growth of stems and leaves position the plant Growth to receive the best light sources to • Beneficial microenvironments encountered Beneficial cause more growth to exploit the resource cause Plant Macronutrients and Micronutrients • More than 50 chemical elements have been identified among the inorganic substances in plants, but not all of these are essential • A chemical element is considered essential if it is required for a plant to complete a life cycle Essential Mineral Nutrients • Essential: Universal for all plants (14) – Necessary for normal growth and reproduction – Cannot be replaced by another element – Effect must be direct (not indirect need such as only to relieve toxicity of something else) • Macronutrients – elements needed in concentrations of at least 1 mg/g of dry matter • Micronutrients – elements needed in concentrations < 100 µg/g dry matter • Essential Non-mineral: C, O, H • Beneficial: Often limited to a few species – Stimulates growth and development, may be required in some species, examples: Co, Na, Si, Se Experiments Were Designed to Identify Essential Elements Essential Macronutrients, Part 1 Essential Micronutrients, Part 2 •Na, Co, Si, and Se may be required by some plants. Nutrient deficiencies • Mineral nutrient deficiencies occur when the concentration of a nutrient decreases below a typical range (the range may depend on the species) • Deficiencies of specific nutrients lead to specific visual, often characteristic, symptoms reflective of the role of that nutrient in plant metabolism • Nitrogen Deficiency the Most Common Mineral Deficiency in Natural and Agricultural Plants No Nitrogen + Nitrogen Nutrient deficiencies can have obvious impact on plant growth, as in the phosphorus addition field trial above, or more subtle signs as in discolored, often older, leaves in the image to the right. In both cases, Phosphorous deficiency - sweet however, there is a negative impact potato – purpling/ yellowing of on plant health, production and older leaves in a young, stunted longevity. plant, new leaves are dark green Symptoms of Mineral Deficiency • The symptoms of mineral deficiency – Depend partly on the nutrient’s function – Depend on the mobility of a nutrient within the plant • Deficiency of a mobile nutrient usually affects older organs more than young ones • Deficiency of a less mobile nutrient usually affects younger organs more than older ones Mineral deficiencies • The most common deficiencies are those of nitrogen, potassium, and phosphorus Healthy Phosphate-deficient Potassium-deficient Nitrogen-deficient Animals are heterotrophs • Require external source of food (energy & mass), hence “need to feed” • Classified by diet: herbivore, carnivore or omnivore • Classified by feeding strategies (filter or suspension feeders, bulk feeders, fluid feeders, substrate feeders) • Ultimately, food must be chemically converted into tissue or used for energy Feeding Styles SUSPENSION FEEDERS SUBSTRATE FEEDERS Feces Baleen Caterpillar FLUID FEEDERS BULK FEEDERS What style of feeding is used by humans? • Regardless of what an animal eats, an adequate diet must satisfy three nutritional needs – Fuel for all cellular work – The organic raw materials for biosynthesis – Essential nutrients, substances such as vitamins that the animal cannot make for itself Digestion is hazardous process! Digestive system (extracts energy & mass) Respiratory system (gas exchange) Circulatory system (transport) Body tissues & cells Excretory system (waste removal, osmoregulation) “Food” is chemically identical to body’s tissues…and enzymes can’t tell the difference. Digestion is carefully regulated process that occurs outside the body. Brain signals: Appetite ⇔ Appetite Control • Several chemical signals called hormones regulate both long-term and short-term appetite by affecting a “satiety center” in the brain Secreted by the stomach wall, ghrelin is one of the signals that triggers feelings of hunger as mealtimes approach. In dieters who lose weight, ghrelin levels increase, which may be one reason it’s so hard to stay on a diet. Produced by adipose (fat) tissue, leptin suppresses appetite as its level increases. When body fat decreases, leptin levels fall, and appetite increases. New discovery: Obestatin, suppresses appetite Ghrelin The hormone PYY, secreted by the small intestine after meals, acts as an appetite suppressant that counters the appetite stimulant ghrelin. Insulin Leptin PYY A rise in blood sugar level after a meal stimulates the pancreas to secrete insulin. In addition to its other functions, insulin suppresses appetite by acting on the brain. The brain determines the frequency, quantity & type of food consumed. Receptors in the brain respond to hormones produced in the digestive tract. The Power of Hormones over Behavior! This mouse has a mutated gene for leptin, thus disrupting signal from adipose tissue to brain, appetite not suppressed This mouse is genetically identical to the fat one, except it has a normal gene for leptin. Adipose tissue signals brain to stop eating. Food-Related Health Problems • Caloric imbalance - Undernourishment – Occurs in animals when their diets are chronically deficient in calories and can have detrimental effects on an animal • The World Health Organization recognizes obesity as a major global health problem. Obesity contributes to a number of health problems, including diabetes, cardiovascular disease, and colon and breast cancer Diet must supply all essential nutrients • Essential Nutrients – cannot be synthesized (must be obtained preassembled) • Malnourishment – lacking essential nutrient • Four classes – – – – Essential amino acids Essential fatty acids Vitamins Minerals Essential Amino Acids Methionine Beans and other legumes Valine Threonine Phenylalanine Corn (maize) and other grains Leucine Isoleucine Tryptophan Lysine Kwashiorkor • Meat contains all essential amino acids, vegetarians should eat grains & legumes • A diet that provides insufficient amounts of one or more essential amino acids causes a form of malnutrition called protein deficiency. Essential Fatty Acids • Animals can synthesize most of the fatty acids they need • The essential fatty acids are certain unsaturated fatty acids • Deficiencies in fatty acids are rare Two categories of vitamins: fat & water soluble Minerals: simple inorganic nutrients • Mineral requirements of humans ...
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This note was uploaded on 05/23/2011 for the course BIOLOGY 1520 taught by Professor Davidgarton during the Fall '09 term at Georgia Institute of Technology.

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