Animal Nutrition

Chapter 41: Animal Nutrition *includes only basics from reading guide* - - - - Three purposes of taking in food: 1. Chemical energy for cellular processes 2. Organic building blocks for macromolecules 3. Essential nutrients: materials that animals cannot assemble from simple organic precursors; preassembled organic molecules and minerals  Serve as coenzymes and cofactors (amino acids) Essential Amino Acids: most animal species only have enough enzymes to synthesize half of the 20 amino acids, so the remaining must be obtained from food in prefabricated forms Carbohydrates, lipids, and proteins are used in cellular respiration to make ATP energy Ingestion: act of eating or feeding Digestion: food is broken down into molecules small enough for the body to absorb Absorption: cells take up small molecules such as amino acids and simple sugars Elimination: undigested material passes out of the digestive system Food vacuoles are the simplest digestive compartment o Intracellular Digestion: hydrolysis of food inside vacuoles o Newly formed ones fuse with lysosomes o Allows digestion to occur safely within a compartment enclosed by a protective membrane Gastrovascular Cavity: a digestive compartment with a single opening o Extracellular Digestion o Functions in digestion and distribution of nutrients o Specialized gland cells secrete digestive enzymes o Cells of the gastrodermis engulf food particles o Most of the hydrolysis occurs intracellularly o Alimentary Canal: a digestive tube extending between two openings (complete digestive track) Mammalian Digestive System: o First goal after ingestion is to break up food into smaller pieces for more efficient absorption  Mechanical digestion in the mouth (increase surface area) o Salivary Glands: deliver saliva through ducts  Amalase hydrolyzes starch and glycogen o Esophagus: connects mouth to stomach  Peristaltic contractions o Stomach: stores food and begins digestion of proteins  Gastric juice (digestive fluid) and churning action results in chyme  Protease: protein-digesting enzyme (pepsin) o Small Intestine: absorbs the vast majority of nutrients  Duodenum: first section of small intestine  Chemical digestion  Chyme mixes with digestive juices from the pancreas (bile), liver, and gallbladder  - Villi: large folds in the lining of the small intestine are studded with finger-like projections  Microvilli  Increase surface area to increase contact with food and absorb more nutrients o Food is stored in the liver  Made of many different enzymes to convert certain monomers into others and neutralize toxic elements o Large intestine: water is reabsorbed that was secreted by body cells earlier in the digestive system  Crucial as diarrhea and resulting dehydration may occur if this doesn’t happen o Rectum: feces are stored until they can be eliminated through the anus Mutualistic Intestinal Bacteria o Bacteria produce vitamins that supplement dietary intake and regulate the development of intestinal epithelium (aid in digestion) o The digestive track provides a microbiome for the bacteria to live in Macromolecules Elements Bonds Carbohydrates C, H, O Glydosidic Linkages (hydroxyl groups) Function Instant energy Monomer Monosaccharide Polymer Polysaccharide Lipids C, H, O Ester Linkages (hydroxyl and carboxyl groups) Long term energy storage Insulate body Cushion organs No true monomer (fatty acid) Triglycerol Proteins C, H, O, N, S Peptide Bonds (carboxyl and amine) Enzymes, defense, hormonal, etc. Nucleic Acids C, H, O, N, P Amino Acid Nucleotide Polypeptide Polynucleotide Instructions for making proteins Unit 2: Cell Structure and Function Chapter 6: A Tour of the Cell - - - Cells can be seen with a light microscope Cells: basic structural and functional units of every organism o Prokaryotes and eukaryotes All cells have o Cell membrane o DNA (chromosomes) o Ribosomes (protein synthesis) Eukaryotic Cell: most DNA is in the nucleus, which is bound by a double membrane o Internal membranes form compartments that support specific metabolic functions so that incompatible processes can occur at the same time o Cell and organelle membranes contribute to metabolism because of enzymes built directly in them  Mitochondria membrane contribute to cellular respiration Prokaryotic Cell: DNA is in a unconcentrated region o 1 to 5 micrometers - - - - - o Nucleoid: the concentrated region where DNA is stored without a membrane o Lack membrane-bound organelles o 10 to 100 micrometers Cytoplasm: interior part of cells o Between the nucleus and plasma membrane Plasma Membrane: selective barrier that allows passage of enough oxygen, nutrients, and wastes to service the entire cell o Want to have a high surface area : volume ratio  Explains the long, narrow shape of most cells  Large organisms have more cells, not larger cells Nucleus: contains most genes in eukaryotic cells o Nuclear Envelope: encloses the nuclear to separate it from the cytoplasm  Double membrane  Has many pores  Pore Complex: lines each pore and regulates the exit of RNA and proteins  Nuclear Lamina: lines the nuclear side of the envelope besides pores  Maintains the shape of the nucleus o Nuclear Matrix: framework of protein fibers extending throughout the nuclear interior o Chromosomes: DNA is organized into these discrete units  Chromatin: the complex of DNA and proteins making up chromosomes  Usually cannot be distinguished from one another  Thicken and distinguish as the cell prepares to divide o Nucleolus: prominent structure in nondividing nuclei Ribosomes: complexes made of ribosomal RNA and protein that carry out protein synthesis o Not considered organelles because they are not membrane bound o Cells with higher rates of protein synthesis have more ribosomes o Free ribosomes are suspended in cytosol  Most proteins made here function in the cytosol o Bound ribosomes are attached to the ER or nuclear envelope  Usually make proteins to be inserted in membranes or for packaging in other organelles such as lysosome o Cells that specialize in protein secretion (like pancreatic cells) have more bound ribosomes Endomembrane System: nuclear envelope, endoplasmic reticulum, golgi apparatus, lysosomes, vesicles and vacuoles, and the plasma membrane o Protein synthesis and transportation o Metabolism o Lipid movement o Detoxification o Connected through vesicles: stacks made of membranes o Vary in structure and function Endoplasmic Reticulum o More than half the membrane in eukaryotic cells o Membranous tubules and sacs (cisternae) o ER lumen / cisternal space: internal sections subdivided by the membrane o Continuous with the nuclear envelope o Smooth ER: lacks ribosomes  - - - Lipid synthesis  Sex and steroid hormones  Carbohydrate metabolism  Store calcium ions  Detoxify drugs  Add hydroxyl groups to make them soluble o Rough ER: ribosomes on the outer surface  Many cells secrete proteins made by the bound ER  As polypeptide chains grow from the bound ribosomes, they are threaded into the ER lumen by a pore formed by a protein complex in the ER membrane  Glycoproteins: proteins with carbohydrates covalently bonded to them  Most secretary proteins  Carbohydrates are attached to proteins in the ER lumen by enzymes in the ER membrane  Keeps secretory proteins separate from proteins that stay in the cytosol (made by free ribosomes)  Secretory proteins leave the ER wrapped in vesicles’ membranes  Transport Vesicles: vesicles in transit within the cell  Makes phospholipids and expands its membranes which is later transferred to other parts of the endomembrane system Golgi Apparatus: receiving, sorting, shipping, and some manufacturing o ER products, such as proteins, are modified and sent to other destinations o Cisternae: flattened membrane stacks  Membrane of each cisternae separates it from cytosol o Differ in thickness and molecular composition on different sides o Materials moved from ER to golgi body from transport vesicles o Manufactures some macromolecules (including secretory polysaccharides) o May have molecules on membranes to recognized “docking sites” on some organelles Lysosomes: membranous sac of hydrolytic enzymes that eukaryotic cells use to digest macromolecules o Small leakages from lysosomes are irrelevant because of the near neutral pH of the cytosol o Made in the golgi body from lysosomal membranes and hydrolytic enzymes from the ER o 3-D shape of proteins in the lysosomes spare them from being destroyed by enzymes o Intracellular digestion o Phagocytosis: engulf smaller organisms or food particles (“eating”)  Formed food vacuole fuses with the lysosome  Digested products go to cytosol as cell nutrients  Macrophages (white blood cell) do this o Autophagy: process that uses hydrolytic enzymes to recycle the cells’ own organic material  Ex: human liver cells recycle half of its organic molecules weekly  Damaged organelle is surrounded by a double membrane  outer membrane fuses with lysosome  lysosomal enzymes dismantle enclosed material  small, organic molecules released to cytosol o Some diseases make the lysosomes have indigestible material (Ex: Tay-sachs  inactive or missing lipid-digesting enzymes) Vacuoles: large vesicles derived from ER and golgi apparatus o Selective transportation of solutes o Food vacuoles for phagocytosis Contractile Vacuole: in unicellular organisms to pump excess water out Some may carry out enzymatic hydrolysis in plants and fungi May hold small amounts or organic material May protect plants from herbivores by storing poisonous or unpalatable material Central Vacuoles: contains cell sap, the plant cell’s main source of repository or inorganic ions (potassium and chloride)  In mature plant cells  Made by combining small vacuoles Mitochondria: sites of cellular respiration, the metabolic process that uses oxygen for ATP generation by extracting energy from sugars, fats, etc. o In nearly all eukaryotic cells (including unicellular) o Some cells have one large mitochondria, but more have hundreds, or even thousands o Cells that move or contract have more than average mitochondria o Has 2 membranes that are phospholipid bilayers  Outer membrane is smooth  Inner membrane is convoluted (complex)  Divides it into 2 inner compartments 1. Intermembrane Space 2. Mitochondrial Matrix: contains enzymes, ribosomes, and mitochondrial DNA o Enzymes catalyze some steps of cellular respiration o Other proteins may be build into the inner membrane o Increase the surface area (highly folded) and productivity o 1 to 10 micrometers o Changeable shape  grow and pinch in 2 to reproduce o Move along the cytoskeleton for mobility Chloroplasts: convert solar energy to chemical energy by using sunlight to drive organic compound synthesis, such as sugars from carbon dioxide and water o Plants and cyanobacteria o 3 to 6 micrometers o Green chlorophyll o Thylakoids: membranous systems that are flattened, interconnected sacs  Granum: thylakoids stacked like poker chips  Stroma: fluid outside the thylakoids (has chloroplast DNA, enzymes, and ribosomes) o Compartmental organization enables converting light to chemical energy o Changeable shape  grow and pinch in 2 to reproduce o Move along the cytoskeleton for mobility Plastids: family of closely related plant organelles o Chloroplast is a member o Amyloplast: colorless organelle that stores starch (amylose) in roots and tubers o Chromoplast: gives flowers and fruits pigments Endosymbiont Theory (for mitochondria and chloroplast): early ancestors of eukaryotic cells engulfed a non-photosynthetic, oxygen-using, prokaryotic cell o Engulfed cell alter formed a relationship with the host cell, eventually merging into a single organism (eukaryotic cell with mitochondria) o Supported because mitochondria and chloroplast have double membranes o Mitochondria and chloroplasts have ribosomes and circular DNA o o o o o - - - -  DNA directs the ribosome’s protein synthesis o Mitochondria and chloroplasts are somewhat autonomous (independently grow and reproduce) - - - Peroxisome: specialized metabolic compartment in the cytosol bound by a single membrane o Remove hydrogen from substrates and transfer them to O2 to make hydrogen peroxide (H2O2) Cytoskeleton: network of fibers extending throughout the cytoplasm o Organizing structures and activities of the cell o Physical support to maintain the shape  more important for animals because they lack cell walls o Anchorage for many organelles o Can quickly be dismantles and reassembled  shape keeps changing o Mobility  Cytoskeleton interacts with motor proteins to allows the whole cell to move along fibers outside the cell  Microtubules  intermediate filaments  microfilaments o Cilia and flagella Cell Wall: extracellular structure of plant cells that distinguished them from animal cells o Protection o Maintains shape o Prevents excessive water uptake o Prokaryotes, fungi, plants, some unicellular eukaryotes Extracellular Matrix: glycoproteins and other carbon-containing molecules secreted from cells o Biochemical support to surrounding cells Chapter 7: Membrane Structure and Function - - - - Made of lipids, proteins, and carbohydrates o Lipids  phospholipids are the most abundant o Proteins are grouped together in patches (not spread out evenly) to carry out specific reactions Amphipathic: hydrophilic and hydrophobic regions o Phospholipids Hydrophilic regions protrude from the rest of the membrane o Maximizes hydrophilic region contact with water in the cytosol and extracellular fluid Fluid Mosaic Model: the cell membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids Membrane is held together by hydrophobic interactions (weaker than covalent bonds) o Enables lateral (side to side) movement Membrane remains fluid until temperature decreases so much that the membrane solidifies and the lipids are held together tightly o Solidification temperature depends on the types of lipids  Lower temperature for phospholipids  kinks where double bonds are make it harder for the phospholipids to stack on each other Cholesterol limits membrane movement at high temperatures o Lowers temperature required for solidification o “fluidity buffer” Fluidity effects permeability and motility Integral Proteins: penetrate the hydrophobic interior of the lipid bilayer - - - - - o Mostly transmembrane proteins (go across the entire bilayer) o Hydrophobic regions have nonpolar amino acids Peripheral Proteins: appendages loosely bounded to the surface of the membrane o Control cell shape and size Membrane proteins may be held in place by attaching to the cytoskeleton Cell membrane is also a functional mosaic (especially in unicellular organisms) o Transport proteins provide a hydrophilic channel across the membrane that is selective for a particular solute o Transport proteins may shuttle a substance from one side to the other and hydrolyze ATP as an energy source to actively pump substance across the membrane o Enzymes built in the membrane may have active sites exposed  may be organized in “teams” to carry out sequential steps of a metabolic pathway o Signal transduction  have a binding site in the shape of chemical messengers that cause the protein to change shape to relay the message o Cell to cell recognition  glycoproteins serve as identification tags that are recognized by other cells’ membrane proteins to make short-lived cell to cell to binding o Intercellular Joining  membrane proteins of adjacent cells hook together in junctions to make long-lasting bonds Cell to cell recognition: o Glycolipids: carbohydrates covalently bonded to lipids o Glycoproteins: carbohydrates covalently bonded to proteins o Cells recognize other cells by binding to these on the plasma membrane surface o Ex: blood types (A, B, AB, O) Phospholipids allows nonpolar molecules to pass because they can dissolve in the bilayer Hydrophobic interior blocks polar molecules from passing o Charged molecules carry a shell of water making passage less likely o These molecules require transport proteins  Also called channel proteins  Aquaporins: channel proteins specific for water  Span the length of the entire membrane o Carrier Proteins: hold onto their passengers and change shape in a way that shuttle across the membrane Diffusion: movement of particles of any substance so that they spread out into the available space o Osmosis is water diffusion o Facilitated Diffusion: diffuse passively with the help of transport proteins o Simple  doesn’t require energy Concentration Gradient: the region along which the density of a chemical substance increases or decreases Passive Transport: diffusion of a substance across a biological membrane Tonicity: the ability of a surrounding solution to cause a cell to gain or lose water o Isotonic: solution and cell have the same concentrations  Plant cell is flaccid o Hypertonic: has more concentration  - - A solution is hypertonic to the cell when it has a higher solute concentration  Water will exit the cell o Animal cell shrivels o Plant cell gets plasmolyzed o Hypotonic: has less concentration  A solution is hypotonic to the cell when it has lower solute concentration  Water will enter the cell o Animal cell lyses o Plant cell is turgid (normal) Active Transport: pumping a solute across a membrane against its concentration gradient that requires energy o Enables a cell to maintain internal concentration of small solutes that differ from concentrations in its environment o Ex: animal cells have higher K+ and lower Na+ o ATP releasing a phosphate group can cause the protein to change shape to translocate the solute bound to the protein across the membrane o Sodium – Potassium Pump: exchanged Na+ for K+ across the plasma membrane of cell walls Electrochemical Gradient: the inside of the cell is negative compared to the outside, the membrane potential favors the passive transport of cations into the cell and anions out of the cell Exocytosis: cell secretes certain molecules by the fusion of vesicles with the plasma membrane Endocytosis o Pinocytosis and phagocytosis Chapter 36: Resource Acquisition and Transport in Vascular Plants - Xylem: transports water and minerals from roots to shoots Phloem: transports products of photosynthesis from where they are made or stored to where they are needed - Water Potential: the physical property that predicts the direction in which water will flow o Includes effects of solute concentration and physical pressure o Pure water is 0 o Sum of water and solute potential  Solute Potential: directional proportional to the molarity  -iCRT  Pressure Potential: physical pressure on a solution - - - -  Turgor Pressure: force of plasma membrane against the cell wall Bulk Flow: movement of lipid in response to a pressure gradient o Independent on solute concentration o Occurs in the xylem (vessel shape) o Root Push: concentration of solutes creates a negative solute potential in the xylem, causing water to rush in a cell walls to bulge, making a positive pressure potential that pushes more water up o TACT Mechanism: transpiration, adhesion, cohesion, and tension  Transpiration  weak hydrogen bonds in liquid water are broken as it turns to water vapor (this pull was a negative pressure potential)  Evaporation lowers the water potential to create a gradient  Cohesion  water sticks to itself so pulling a little bit of water will also pull more  Adhesion  allows water to stick to cell walls to resist gravity  Overall process creates a very negative pressure potential value up at the leaves the pulls water towards it o Moves the entire solution (water and solute) faster than diffusion Leaves have high SA : volume ratio to enhance light absorption, carbon dioxide absorption, and oxygen release o Also increase water loss from the stomata  guard cells Stomata open when guard cells accumulate K+ from epidermal cells  this and membrane potential from proton pumps drive the guard cells open o Stomata close when K+ is lost to neighboring cells o Aquaporins regulate osmotic swelling and shrinking of guard cells o Usually open in the day and close at night to prevent losing water in conditions where photosynthesis can’t occur o Light and CO2 depletion can open the stomata Lack of pull from transpiration can lose turgor pressure In CAM plants, leaves take in carbon dioxide at night so that stomata can remain closed during the day to avoid excessive water loss from the desert sun Chapter 42: Circulation and Gas Exchange - 2 adaptions to increase diffusion 1. Place many of all cells in direct contact with the environment to directly exchange material  Only in certain invertebrates - - - - 2. Circulatory system Gastrovascular Cavity: functions in the distribution of substances throughout the body as well as in digestion o Opening on one end connects the cavity to water o Fluid bathes both tissue layers to exchange gasses and cellular waste o Planarians and flatworms can use this instead of a circulatory system because of the flat body increasing surface area and minimized diffusion distances Open Circulatory System: circulatory fluid (hemolymph of interstitial fluid) bathes body cells o Arthropods, grasshoppers, mollusks, clams, etc. Closed Circulatory System: blood is confined to vessels and is distinct from the interstitial fluid Fish have single circulation (1 atrium and 1 ventricle), but this causes low blood pressure and takes more time for blood to reach the rest of the body Amphibian hearts added another circuit to help repressurize blood to solve this problem, but it mixes deoxygenated and oxygenated blood Mammalian hearts have 2 atria and 2 ventricles to keep the 2 kinds of blood separate o Endotherms require more energy (warm-blooded) Blood flow is slower in capillaries than in arteries o Good because it requires more time for the gas exchange to happen through diffusion in the capillaries o Blood pressure is lower in capillaries and slowest in veins Only 5 to 10% of capillaries have blood at any moment o Precapillary sphincters control the flow Red blood cells (erythrocytes) curve in towards the middle and lack nuclei to increase capacity to carry gasses o Hemoglobin Countercurrent exchange in fish gills