BMSP 2135 Anatomy Physiology Chapter 2
BMSP 2135 Anatomy Physiology Chapter 2 2135 BMSP
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This 24 page Class Notes was uploaded by Marlena Trone on Saturday September 10, 2016. The Class Notes belongs to 2135 BMSP at Virginia Polytechnic Institute and State University taught by in Fall 2016. Since its upload, it has received 10 views.
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Date Created: 09/10/16
CHAPTER 2: The Chemistry of Life Element: The simplest form of matter to have unique chemical properties THE CHEMICAL ELEMENTS ATOMIC NUMBER: number of protons – Each element has a different atomic number – The periodic table arranges elements by their atomic number – 24 elements have biological role • Just 6 elements make up 98.5% of body weight – Oxygen – O – 65% – Carbon – C – 18% – Hydrogen – H – 10% – Nitrogen – N – 3% – Calcium – Ca – 1.5% – Phosphorus – P – 1% ATOM: the smallest unit of matter that still retains the properties of an element ATOMIC STRUCTURE • Atoms are made of over a hundred subatomic particles • only three subatomic particles are important for biological compounds – PROTON—has a single positive electrical charge and weighs about 1 amu (atomic mass unit) – NEUTRON—is electrically neutral and weighs about 1 amu – ELECTRON—has a single negative electrical charge and has a weight of about 0 amu (the weight is negligible since it takes almost 2,000 electrons to equal the weight of one neutron) • the atom is electrically neutral because number of electrons is equal to the number of protons • NUCLEUS: center of atom – Contains protons and neutrons • ATOMIC MASS of an element is approximately equal to its total number of protons and neutrons • ELECTRONS: in concentric clouds that surround the nucleus – VALENCE ELECTRONS: are the electrons in the outermost cloud • determine the chemical properties of an atom • For example, it will determine the chemical bonding behavior PLANETARY MODEL OF CARBON + • p represents protons • n represents neutrons • e represents electrons – Arranged in energy levels • The first energy level holds 2 electrons • The second and third level hold up to eight electrons PLANETARY MODELS OF ELEMENTS WHAT IS AN ISOTOPE? – Elements that differ from each other in the number of neutrons – Isotopes have the same proton number and are therefore the same element – Isotopes have the same electron number and therefore have the same chemical properties • Since the number of neutrons differ, they have different atomic masses THREE ISOTOPES OF HYDROGEN These three isotopes of Hydrogen are naturally occurring. Your body does not recognize any differences between these three isotopes since they have the same chemical activity. RADIOISOTOPES AND RADIOACTIVITY • ISOTOPES – same chemical behavior – differ in physical behavior and some breakdown (decay) to more stable isotope by giving off radiation • RADIOISOTOPES – unstable isotopes that give off radiation – every element has at least one radioisotope • RADIOACTIVITY – radioisotopes decay to stable isotopes releasing radiation – we are all mildly radioactive ISOTOPES OF CARBON • Carbon12: – 6 protons and 6 neutrons • Carbon13: – 6 protons and 7 neutrons • Carbon14: – 6 protons and 8 neutrons – Carbon14 is radioactive (a radioisotope) Isotopes are useful as tracers in the body – your body will treat radiolabeled glucose like regular glucose and the radiation can be detected to see which areas of the body are actively using glucose WHAT IS AN ION? • An ION is an atom or molecule with an electrical charge resulting from gain or loss of electrons IONS AND IONIZATION • Chlorine gains an electron and becomes a negative ion, an anion • Sodium has one electron in the outermost shell; if it loses that electron it will become a positive ion, a cation ANIONS AND CATIONS • ANION: atom that gained electrons (overall negative charge) • CATION: atom that lost an electron (overall positive charge) • Ions with opposite charges are attracted to each other ELECTROLYTES • Salts that ionize in water and form solutions capable of conducting an electric current. • Electrolyte importance – chemical reactivity – osmotic effects (influence water movement) – electrical effects on nerve and muscle tissue • Electrolyte balance is one of the most important considerations in patient care. • Imbalances have ranging effects from muscle cramps, brittle bones, to coma and cardiac arrest FREE RADICALS • Chemical particles with an odd number of electrons • Produced by – normal metabolic reactions – radiation – chemicals • Causes tissue damage – reactions that destroy molecules – causes cancer, death of heart tissue and aging • ANTIOXIDANTS: – neutralize free radicals CHEMICAL BONDS • CHEMICAL BONDS – forces that hold molecules together, or attract one molecule to another • Types of Chemical Bonds – Ionic bonds – Covalent bonds – Hydrogen bonds – Van der Waals force IONIC BONDS • The attraction of a cation to an anion • electron donated by one and received by the other COVALENT BONDS • Formed by sharing electrons • Types of covalent bonds – SINGLE sharing of single pair electrons – DOUBLE sharing of 2 pairs of electrons – NONPOLAR COVALENT BOND • shared electrons spend approximately equal time around each nucleus – POLAR COVALENT BOND • if shared electrons spend more time orbiting one nucleus than they do the other, they lend their negative charge to the area they spend most time SINGLE COVALENT BOND • One pair of electrons are shared DOUBLE COVALENT BONDS • Two pairs of electrons are shared NONPOLAR COVALENT BONDS • Electrons Shared Equally POLAR COVALENT BONDS • Electrons shared unequally HYDROGEN BONDS • HYDROGEN BOND – a weak attraction between a slightly positive hydrogen atom in one molecule and a slightly negative oxygen or nitrogen atom in another. • Water molecules are weakly attracted to each other by hydrogen bonds • relatively weak bonds • very important to physiology – protein structure – DNA structure WATER • SOLVENCY – SOLVENCY: ability to dissolve other chemicals – water is called the Universal Solvent • HYDROPHILLIC – substances that dissolve in water • molecules must be polarized or charged • HYDROPHOBIC substances that do not dissolve in water • molecules are nonpolar or neutral (fat) – Virtually all metabolic reactions depend on the solvency of water WATER AS A SOLVENT – Polar water molecules overpower the ionic bond in Na Cl + • forming hydration spheres around each ion • note the orientation of the molecules • ADHESION – ADHESION: tendency of one substance to cling to another • COHESION – COHESION: tendency of like molecules to cling to each other • water is very cohesive due to its hydrogen bonds • surface film on surface of water is due to molecules being held together by a force called surface tension • CHEMICAL REACTIVITY – CHEMICAL REACTIVITY: the ability to participate in chemical reactions • water ionizes into H and OH • water ionizes other chemicals (acids and salts) • water involved in hydrolysis and dehydration synthesis reactions • THERMAL STABILITY – Water helps stabilize the internal temperature of the body • Water has high heat capacity – the amount of heat required to raise the temperature of 1 g of a substance by 1 degree C. • calorie (cal) – the amount of heat that raises the temperature of 1 g of water 1 degree C. • hydrogen bonds inhibit temperature increases by inhibiting molecular motion • water absorbs heat without changing temperature very much • effective coolant • 1 ml of perspiration removes 500 calories ACIDS, BASES AND pH • An ACID is proton donor + – releases H ions in water • A BASE is proton acceptor – releases OH ions in water • pH – a pH of 7.0 is neutral pH + • (H = OH) – a pH of less than 7 is acidic solution • (H > OH) – a pH of greater than 7 is basic solution • (OH > H ) pH • pH measurement of molarity of H [H+] on a logarithmic scale – pH scale invented by Soren Sorensen in 1909 to measure acidity of beer + • a change of one number on the pH scale represents a 10 fold change in H concentration – a solution with pH of 4.0 is 10 times as acidic as one with pH of 5.0 – a solution with pH of 3.0 is 100 times as acidic as one with pH of 5.0 • Our body uses buffers to resist changes in pH – slight pH disturbances can disrupt physiological functions METABOLISM • All the chemical reactions of the body • Catabolism – energy releasing (exergonic) decomposition reactions • breaks covalent bonds • produces smaller molecules • releases useful energy • Anabolism – energy storing (endergonic) synthesis reactions • requires energy input • production of larger molecules • driven by energy that catabolism releases • Catabolism and Anabolism are inseparably linked ORGANIC CHEMISTRY • Study of compounds containing carbon • 4 categories of carbon compounds – carbohydrates – lipids – proteins – nucleotides and nucleic acids ORGANIC MOLECULES AND CARBON • 4 valence electrons – binds with other atoms that can provide it with four more electrons to fill its valence shell • carbon atoms bind readily with each other – carbon backbones – forms long chains, branched molecules and rings • carbon backbone carries a variety of functional groups FUNCTIONAL GROUPS • small clusters of atoms • determines many of the properties of organic molecules MONOMERS AND POLYMERS • Macromolecules very large organic molecules – very high molecular weights • EX: proteins, DNA • Polymers – molecules made of a repetitive series of identical or similar subunits (monomers) • Monomers an identical or similar subunits POLYMERIZATION • joining monomers to form a polymer • Dehydration synthesis (condensation) is how living cells form polymers – Monomers covalently bond together to form a polymer with the removal of a water molecule • A hydroxyl group is removed from one monomer and a hydrogen from the next HYDROLYSIS • Splitting a polymer (lysis) by the addition of a water molecule (hydro) – a covalent bond is broken • All digestion reactions consists of hydrolysis reactions ORGANIC MOLECULES: CARBOHYDRATES • hydrophilic organic molecule • general formula (CH O) 2 n n = number of carbon atoms ex: for glucose, n = 6, so formula is 6 12O 6 • names of carbohydrates often built from: – word root ‘sacchar’ – the suffix ’ose’ • both mean ‘sugar’ or ‘sweet’ MONOSACCHARIDES • Simplest carbohydrates – simple sugars • 3 important monosaccharides – Glucose – Galactose – Fructose – same molecular formula C H O6 12 6 • isomers of each other TYPE FUNCTION Glucose Blood sugar energy source for most cells Galactose Converted to glucose and metabolized Fructose Fruit sugar converted to glucose and metabolized DISACCHARIDES • Sugar molecule composed of 2 monosaccharides • 3 important disaccharides – sucrose table sugar • glucose + fructose – lactose sugar in milk • glucose + galactose – maltose grain products • glucose + glucose TYPE FUNCTION Sucrose Cane sugar digested to glucose and fructose Lactose Milk sugar digested to glucose and galactose; important in infant nutrition Maltose Malt sugar product of starch digestion, further digested to glucose POLYSACCHARIDES • long chains of glucose • 3 polysaccharides of interest in humans – Glycogen: energy storage polysaccharide in animals • made by cells of liver, muscles, brain, uterus, and vagina • liver produces glycogen after a meal when glucose level is high, then breaks it down between meals to maintain blood glucose levels • muscles store glycogen for own energy needs – Starch: energy storage polysaccharide in plants • only significant digestible polysaccharide in the human diet – Cellulose: structural molecule of plant cell walls • fiber in our diet TYPE FUNCTION Cellulose Structural polysaccharide of plants; dietary fiber Starch Energy storage in plant cells Glycogen Energy storage in animal cells (liver, muscle, brain, uterus, vagina) CARBOHYDRATE FUNCTIONS • quickly mobilized source of energy – all digested carbohydrates converted to glucose – oxidized to make ATP • Conjugated carbohydrate – a carbohydrate that is covalently bound to lipid or protein – glycolipids • external surface of cell membrane – glycoproteins • external surface of cell membrane • mucus of respiratory and digestive tracts ORGANIC MOLECULES: LIPIDS • hydrophobic organic molecule – Five primary types in humans • fatty acids • triglycerides • phospholipids • eicosanoids • steroids Fatty Acids – Chain of 4 to 24 carbon atoms • carboxyl (acid) group on one end • methyl group on the other – Classifications of Fatty Acids • saturated carbon atoms saturated with hydrogen • unsaturated contains C=C bonds • polyunsaturated – contains many C=C bonds • essential fatty acids – obtained from diet, body cannot synthesize Triglycerides (Neutral Fats) – 3 fatty acids covalently bonded to glycerol molecule • once joined to glycerol, fatty acids can no longer donate protons – neutral fats – triglycerides • when liquid at room temperature called oils • often polyunsaturated fats from plants • when solid at room temperature called fat • saturated fats from animals • Primary Function energy storage, insulation and shock absorption (adipose tissue) Phospholipids – similar to neutral fat except that one fatty acid replaced by a phosphate group – structural foundation of cell membrane – Amphiphilic • fatty acid “tails” are hydrophobic • phosphate “head” is hydrophilic Eicosanoids – hormonelike chemical signals between cells – includes prostaglandins – produced in all tissues • role in inflammation, blood clotting, & more Steroids and Cholesterol – Steroid – a lipid with four carbon rings – Cholesterol the ‘parent’ steroid from which the other steroids are synthesized • other steroids: cortisol, progesterone, estrogens, testosterone and bile acids – Cholesterol • synthesized only by animals • especially liver cells • 15% from diet, 85% internally synthesized • important component of cell membranes • required for proper nervous system function “GOOD” AND “BAD” CHOLESTEROL • one kind of cholesterol – does far more good than harm • ‘good’ and ‘bad’ cholesterol actually refers to droplets of lipoprotein in the blood – complexes of cholesterol, fat, phospholipid, and protein • HDL – highdensity lipoprotein – “good” cholesterol – lower ratio of lipid to protein – may help to prevent cardiovascular disease • LDL – lowdensity lipoprotein – “bad” cholesterol – high ratio of lipid to protein – contributes to cardiovascular disease ORGANIC MOLECULES: PROTEINS • Greek word meaning “of first importance” – Most versatile molecules in the body • Protein: a polymer of amino acid • Amino acid: central carbon with three attachments – amino group (NH ) 2 – carboxyl group (COOH) – radical group (R group) • 20 amino acids used to make the proteins are identical except for the radical (R) group – Properties of amino acid determined by –R group REPRESENTATIVE AMINO ACIDS • Note: they differ only in the R group NAMING OF PEPTIDES • peptide – any molecule composed of two or more amino acids joined by peptide bonds • peptide bond – bond between amino acids – formed by dehydration synthesis • Peptides named for the number of amino acids – dipeptides have 2 amino acids – tripeptides have 3 amino acids – oligopeptides have fewer than 10 to 15 amino acids – polypeptides have more than 15 amino acids – proteins have more than 50 amino acids DIPEPTIDE SYNTHESIS • dehydration synthesis creates a peptide bond that joins amino acids PROTEIN STRUCTURE AND SHAPE • Primary structure – protein’s sequence amino acid • Secondary structure – coiled or folded shape held together by hydrogen bonds – most common secondary structure are: • alpha helix – springlike shape • beta helix – pleated, ribbonlike shape • Tertiary structure – further bending and folding of proteins into globular and fibrous shapes • globular proteins –compact tertiary structure well suited for proteins embedded in cell membrane and proteins that must move about freely in body fluid • fibrous proteins – slender filaments better suited for roles as in muscle contraction and strengthening the skin • Quaternary structure – associations of two or more separate polypeptide chains PROTEIN CONFORMATION AND DENATURATION • Conformation – unique three dimensional shape of protein crucial to function – ability to reversibly change their conformation • enzyme function • muscle contraction • opening and closing of cell membrane pores • Denaturation – extreme conformational change that destroys function • extreme heat or pH PROTEIN FUNCTIONS • Structure – keratin – tough structural protein • gives strength to hair, nails, and skin surface – collagen – durable protein contained in deeper layers of skin, bones, cartilage, and teeth • Communication – some hormones and other celltocell signals – receptors to which signal molecules bind • ligand – any hormone or molecule that reversibly binds to a protein • Membrane Transport – channels in cell membranes that governs what passes through – carrier proteins – transports solute particles to other side of membrane – turn nerve and muscle activity on and off PROTEIN FUNCTIONS • Catalysis – enzymes • Recognition and Protection – immune recognition – antibodies – clotting proteins • Movement – motor proteins molecules with the ability to change shape repeatedly • Cell adhesion – proteins bind cells together – immune cells to bind to cancer cells – keeps tissues from falling apart ENZYMES • Enzymes proteins that function as biological catalysts – permit reactions to occur rapidly at normal body temperature • Substrate substance an enzyme acts upon • Naming Convention – named for substrate with ase as the suffix • lactase enzyme digests lactose • Lowers activation energy, the energy needed to get reaction started ENZYMATIC ACTION • Reusability of enzymes – enzymes are not consumed by the reactions • Astonishing speed – one enzyme molecule can consume millions of substrate molecules per minute • Factors that change enzyme shape – pH and temperature – alters or destroys the ability of the enzyme to bind to substrate – enzymes vary in optimum pH • salivary amylase works best at pH 7.0 • pepsin works best at pH 2.0 – temperature optimum for human enzymes = body temperature (37 degrees C) ORGANIC MOLECULES: NUCLEOTIDES • 3 components of nucleotides – nitrogenous base (single or double carbonnitrogen ring) – sugar (monosaccharide) – one or more phosphate groups • ATP – best know nucleotide – adenine (nitrogenous base) – ribose (sugar) – phosphate groups (3) ATP (ADENOSINE TRIPHOSPHATE) • body’s most important energytransfer molecule – briefly stores energy gained from exergonic reactions – releases it within seconds for physiological work • holds energy in covalent bonds – 2nd and 3rd phosphate groups have high energy bonds ~ rd – most energy transfers to and from ATP involve adding or removing the 3 phosphate group • Adenosine triphosphatases (ATPases) hydrolyze the 3 high energy phosphate bond – ATP separates into ADP + P + enirgy NUCLEIC ACIDS • polymers of nucleotides • DNA (deoxyribonucleic acid) – 100 million to 1 billion nucleotides long – constitutes genes • instructions for synthesizing all of the body’s proteins • transfers hereditary information from cell to cell and generation to generation • RNA (ribonucleic acid) – 3 types – messenger RNA (mRNA), ribosomal RNA (rRNA), transfer RNA (tRNA) – 70 to 10,000 nucleotides long – carries out genetic instruction for synthesizing proteins – assembles amino acids in the right order to produce proteins
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