An Introduction to the Chemical Level of Organization

An Introduction to the Chemical Level of Organization
Chemistry Is the science of change Topics of this chapter include: The structure of atoms The basic chemical building blocks How atoms combine to form increasingly complex structures © 2015 Pearson Education, Inc.

2-1 Atoms and Atomic Structure
Matter Is made up of atoms Atoms join together to form chemicals with different characteristics Chemical characteristics determine physiology at the molecular and cellular levels © 2015 Pearson Education, Inc.

Figure 2-1 The Structure of Hydrogen Atoms.
Electron shell n − e p + + − e p − + n e n p + Hydrogen-2, deuterium Hydrogen-3, tritium Hydrogen-1 mass number: 1 mass number: 2 mass number: 3 a A typical hydrogen nucleus contains a proton and no neutrons. b A deuterium (2H) nucleus contains a proton and a neutron. c A tritium (3H) nucleus contains a proton and two neutrons.

Table 2-1 Principal Elements in the Human Body
© 2015 Pearson Education, Inc. 7

Table 2-1 Principal Elements in the Human Body
© 2015 Pearson Education, Inc. 8

Elements and Isotopes Isotopes are the specific version of an element based on its mass number Mass number = number of protons plus the number of neutrons Only neutrons are different because the number of protons determines the element © 2015 Pearson Education, Inc.

Electrons and Energy Levels Electrons in the electron cloud determine the reactivity of an atom The electron cloud contains shells, or energy levels, that hold a maximum number of electrons Lower shells fill first Outermost shell is the valence shell, and it determines bonding The number of electrons per shell corresponds to the number of atoms in that row of the periodic table © 2015 Pearson Education, Inc.

Figure 2-2 The Arrangement of Electrons into Energy Levels.
The first energy level can hold a maximum of two electrons. n − + − − e p e + e p Hydrogen, H Helium, He Atomic number: 1 Mass number: 1 1 electron Atomic number: 2 Mass number: 4 (2 protons + 2 neutrons) 2 electrons a Hydrogen (H). A typical hydrogen atom has one proton and one electron. The electron orbiting the nucleus occupies the first, or lowest, energy level, diagrammed as an electron shell. b Helium (He). An atom of helium has two protons, two neutrons, and two electrons. The two electrons orbit in the same energy level.

Figure 2-2 The Arrangement of Electrons into Energy Levels.
The second and third energy levels can each contain up to 8 electrons. − e − − e e − − n e n e − − e − − e p + e + e p − − e e − − e e Lithium, Li Neon, Ne Atomic number: 3 Mass number: 6 (3 protons + 3 neutrons) 3 electrons Atomic number: 10 Mass number: 20 (10 protons + 10 neutrons) 10 electrons c Lithium (Li). A lithium atom has three protons, three neutrons, and three electrons. The first energy level can hold only two electrons, so the third electron occupies a second energy level. d Neon (Ne). A neon atom has 10 protons, 10 neutrons, and 10 electrons. The second level can hold up to eight electrons; thus, both the first and second energy levels are filled.

2-2 Molecules and Compounds
Chemical Bonds Involve the sharing, gaining, and losing of electrons in the valence shell Three major types of chemical bonds Ionic bonds Attraction between cations (electron donor) and anions (electron acceptor) Covalent bonds Strong electron bonds involving shared electrons Hydrogen bonds Weak polar bonds based on partial electrical attractions © 2015 Pearson Education, Inc.

Chemical Bonds Form molecules and/or compounds Molecules Two or more atoms joined by strong bonds Compounds Two or more atoms OF DIFFERENT ELEMENTS joined by strong or weak bonds Compounds are all molecules, but not all molecules are compounds H2 = molecule only H2O = molecule and compound © 2015 Pearson Education, Inc.

Figure 2-3 Chemical Notation (Part 1 of 4).
Atoms The symbol of an element indicates one atom of that element. A number preceding the symbol of an element indicates more than one atom of that element. VISUAL REPRESENTATION CHEMICAL NOTATION H O H O one atom of hydrogen one atom of oxygen one atom of hydrogen one atom of oxygen H H O O 2H 2O two atoms of hydrogen two atoms of oxygen two atoms of hydrogen two atoms of oxygen

Molecules A numerical subscript following the symbol of an element indicates the number of atoms of that element in a molecule. VISUAL REPRESENTATION CHEMICAL NOTATION H H O O H2 O2 hydrogen molecule oxygen molecule hydrogen molecule oxygen molecule composed of two hydrogen atoms composed of two oxygen atoms H2O H H water molecule composed of two hydrogen atoms and one oxygen atom water molecule O

Reactions In a description of a chemical reaction, the participants at the start of the reaction are called reactants, and the reaction generates one or more products. Chemical reactions are represented by chemical equations. An arrow indicates the direction of the reaction, from reactants (usually on the left) to products (usually on the right). In the following reaction, two atoms of hydrogen combine with one atom of oxygen to produce a single molecule of water. VISUAL REPRESENTATION CHEMICAL NOTATION H H 2H + O H2O + H H O O Balanced equation Chemical reactions neither create nor destroy atoms; they merely rearrange atoms into new combinations. Therefore, the numbers of atoms of each element must always be the same on both sides of the equation for a chemical reaction. When this is the case, the equation is balanced. 2H + 2O H2O Unbalanced equation

Ions A superscript plus or minus sign following the symbol of an element indicates an ion. A single plus sign indicates a cation with a charge of +1. (The original atom has lost one electron.) A single minus sign indicates an anion with a charge of −1. (The original atom has gained one electron.) If more than one electron has been lost or gained, the charge on the ion is indicated by a number preceding the plus or minus sign. VISUAL REPRESENTATION CHEMICAL NOTATION Na+ Cl− Ca2+ Na+ Cl− Ca2+ sodium ion chloride ion calcium ion sodium ion chloride ion calcium ion the sodium atom has lost one electron the chlorine atom has gained one electron the calcium atom has lost two electrons A sodium atom becomes a sodium ion Electron lost + Na Na+ Sodium atom (Na) Sodium ion (Na+)

Ionic Bonds One atom—the electron donor—loses one or more electrons and becomes a cation, with a positive charge Another atom—the electron acceptor—gains those same electrons and becomes an anion, with a negative charge Attraction between the opposite charges then draws the two ions together © 2015 Pearson Education, Inc.

Figure 2-4a The Formation of Ionic Bonds.
1 2 3 Formation of ions Attraction between opposite charges Formation of an ionic compound Sodium atom Sodium ion (Na+) Na Na Na + + − − Cl Cl Cl Sodium chloride (NaCl) a Chlorine atom Chloride ion (Cl−) a Formation of an ionic bond. 1 A sodium (Na) atom loses an electron, which is accepted by a chlorine (Cl) atom Because the sodium ion (Na+) and chloride ion (Cl−) have opposite charges, they are attracted to one another The association of sodium and chloride ions forms the ionic compound sodium chloride. 2 3

Figure 2-4b The Formation of Ionic Bonds.
Chloride ions (Cl−) Sodium ions (Na+) b Sodium chloride crystal. Large numbers of sodium and chloride ions form a crystal of sodium chloride (table salt).

Covalent Bonds Involve the sharing of pairs of electrons between atoms One electron is donated by each atom to make the pair of electrons Sharing one pair of electrons is a single covalent bond Sharing two pairs of electrons is a double covalent bond Sharing three pairs of electrons is a triple covalent bond © 2015 Pearson Education, Inc.

Figure 2-5 Covalent Bonds in Five Common Molecules.
Electron Shell Model and Structural Formula Molecule Hydrogen (H2) H − H Oxygen (O2) O = O Carbon dioxide (CO2) O = C = O Nitrogen (N2) N ≡ O Nitric oxide (NO) N = O

Covalent Bonds Nonpolar covalent bonds Involve equal sharing of electrons because atoms involved in the bond have equal pull for the electrons Polar covalent bonds Involve the unequal sharing of electrons because one of the atoms involved in the bond has a disproportionately strong pull on the electrons Form polar molecules — like water © 2015 Pearson Education, Inc.

Figure 2-6 Water Molecules Contain Polar Covalent Bonds.
Hydrogen atom Hydrogen atom Oxygen atom a Formation of a water molecule. In forming a water molecule, an oxygen atom completes its outermost energy level by sharing electrons with a pair of hydrogen atoms. The sharing is unequal, because the oxygen atom holds the electrons more tightly than do the hydrogen atoms. δ+ Hydrogen atom Oxygen atom δ+ 2δ− b Charges on a water molecule. Because the oxygen atom has two extra electrons much of the time, it develops a slight negative charge, and the hydrogen atoms become weakly positive. The bonds in a water molecule are polar covalent bonds.

Hydrogen Bonds Bonds between adjacent molecules, not atoms Involve slightly positive and slightly negative portions of polar molecules being attracted to one another Hydrogen bonds between H2O molecules cause surface tension © 2015 Pearson Education, Inc.

Figure 2-7 Hydrogen Bonds Form between Water Molecules.
δ+ δ+ 2δ− 2δ− δ+ δ+ δ+ 2δ− δ+ δ+ δ+ 2δ− 2δ− δ+ δ+ δ+ 2δ− 2δ− KEY Hydrogen Oxygen Hydrogen bond

2-3 Chemical Reactions In a Chemical Reaction
Either new bonds are formed or existing bonds are broken Reactants Materials going into a reaction Products Materials coming out of a reaction Metabolism All of the reactions that are occurring at one time © 2015 Pearson Education, Inc.

2-3 Chemical Reactions Types of Chemical Reactions
Decomposition reaction (catabolism) Synthesis reaction (anabolism) Exchange reaction Reversible reaction © 2015 Pearson Education, Inc.

2-3 Chemical Reactions Decomposition Reaction (Catabolism)
Breaks chemical bonds AB  A + B Hydrolysis A-B + H2O  A-H + HO-B Synthesis Reaction (Anabolism) Forms chemical bonds A + B  AB Dehydration synthesis (condensation reaction) A-H + HO-B  A-B + H2O © 2015 Pearson Education, Inc.

2-3 Chemical Reactions Exchange Reaction
Involves decomposition first, then synthesis AB + CD  AD + CB © 2015 Pearson Education, Inc.

2-3 Chemical Reactions Reversible Reaction A + B ↔ AB
At equilibrium the amounts of chemicals do not change even though the reactions are still occurring Reversible reactions seek equilibrium, balancing opposing reaction rates Add or remove reactants Reaction rates adjust to reach a new equilibrium © 2015 Pearson Education, Inc.

2-4 Enzymes Chemical Reactions In cells, cannot start without help
Activation energy is the amount of energy needed to get a reaction started Enzymes are protein catalysts that lower the activation energy of reactions © 2015 Pearson Education, Inc.

Figure 2-8 Enzymes Lower Activation Energy.
Activation energy required Without enzyme 1 2 With enzyme Energy Reactant(s) 3 Stable product(s) 4 Progress of reaction

2-4 Enzymes Exergonic (Exothermic) Reactions
Produce more energy than they use Endergonic (Endothermic) Reactions Use more energy than they produce © 2015 Pearson Education, Inc.

2-5 Inorganic and Organic Compounds
Nutrients Essential molecules obtained from food Metabolites Molecules made or broken down in the body Inorganic Compounds Molecules not based on carbon and hydrogen Carbon dioxide, oxygen, water, and inorganic acids, bases, and salts Organic Compounds Molecules based on carbon and hydrogen Carbohydrates, proteins, lipids, and nucleic acids © 2015 Pearson Education, Inc.

2-6 Properties of Water Water
Accounts for up to two-thirds of your total body weight A solution is a uniform mixture of two or more substances It consists of a solvent, or medium, in which atoms, ions, or molecules of another substance, called a solute, are individually dispersed © 2015 Pearson Education, Inc.

2-6 Properties of Water Solubility Reactivity High Heat Capacity
Water’s ability to dissolve a solute in a solvent to make a solution Reactivity Most body chemistry occurs in water High Heat Capacity Water’s ability to absorb and retain heat Lubrication To moisten and reduce friction © 2015 Pearson Education, Inc.

Figure 2-9a Water Molecules Surround Solutes in Aqueous Solutions.
Negative pole 2δ− O δ+ H Positive pole δ+ a Water molecule. In a water molecule, oxygen forms polar covalent bonds with two hydrogen atoms. Because both hydrogen atoms are at one end of the molecule, it has an uneven distribution of charges, creating positive and negative poles.

2-6 Properties of Water The Properties of Aqueous Solutions
Electrolytes and body fluids Electrolytes are inorganic ions that conduct electricity in solution Electrolyte imbalance seriously disturbs vital body functions © 2015 Pearson Education, Inc.

Table 2-2 Important Electrolytes That Dissociate in Body Fluids.

2-6 Properties of Water The Properties of Aqueous Solutions
Hydrophilic and hydrophobic compounds Hydrophilic hydro- = water, philos = loving Interacts with water Includes ions and polar molecules Hydrophobic phobos = fear Does NOT interact with water Includes nonpolar molecules, fats, and oils © 2015 Pearson Education, Inc.

2-7 pH and Homeostasis pH Neutral pH
The concentration of hydrogen ions (H+) in a solution Neutral pH A balance of H+ and OH Pure water = 7.0 © 2015 Pearson Education, Inc.

2-7 pH and Homeostasis Acidic pH Lower Than 7.0
High H+ concentration Low OH concentration Basic (or alkaline) pH Higher Than 7.0 Low H+ concentration High OH concentration pH of Human Blood Ranges from 7.35 to 7.45 © 2015 Pearson Education, Inc.

2-7 pH and Homeostasis pH Scale
Has an inverse relationship with H+ concentration More H+ ions means lower pH, fewer H+ ions means higher pH © 2015 Pearson Education, Inc.

Figure 2-10 The pH Scale Indicates Hydrogen Ion Concentration.
1 mol/L hydrochloric acid 1 mol/L sodium hydroxide Beer, vinegar, wine, pickles Urine Oven cleaner Stomach acid Tomatoes, grapes Blood Ocean water Household bleach Saliva, milk Pure water Eggs Household ammonia Extremely acidic Extremely basic Increasing concentration of H+ Neutral Increasing concentration of OH− pH [H+] 100 14 10−1 10−2 10−3 10−4 10−5 10−6 10−7 10−8 10−9 10−10 10−11 10−12 10−13 10−14 (mol/L)

2-8 Inorganic Compounds Acid Base Weak Acids and Weak Bases
A solute that adds hydrogen ions to a solution Proton donor Strong acids dissociate completely in solution Base A solute that removes hydrogen ions from a solution Proton acceptor Strong bases dissociate completely in solution Weak Acids and Weak Bases Fail to dissociate completely Help to balance the pH © 2015 Pearson Education, Inc.

2-8 Inorganic Compounds Salts
Solutes that dissociate into cations and anions other than hydrogen ions and hydroxide ions © 2015 Pearson Education, Inc.

2-8 Inorganic Compounds Buffers and pH Control Buffers Antacids
Weak acid/salt compounds Neutralize either strong acid or strong base Sodium bicarbonate is very important in humans Antacids Basic compounds that neutralize acid and form a salt Alka-Seltzer, Tums, Rolaids, etc. © 2015 Pearson Education, Inc.

2-9 Carbohydrates Organic Molecules Contain H, C, and usually O
Are covalently bonded Contain functional groups that determine chemistry Carbohydrates Lipids Proteins (or amino acids) Nucleic acids © 2015 Pearson Education, Inc.

Table 2-3 Important Functional Groups of Organic Compounds.

2-9 Carbohydrates Carbohydrates
Contain carbon, hydrogen, and oxygen in a 1:2:1 ratio Monosaccharide — simple sugar Disaccharide — two sugars Polysaccharide — many sugars © 2015 Pearson Education, Inc.

2-9 Carbohydrates Monosaccharides Disaccharides Polysaccharides
Simple sugars with 3 to 7 carbon atoms Glucose, fructose, galactose Disaccharides Two simple sugars condensed by dehydration synthesis Sucrose, maltose Polysaccharides Many monosaccharides condensed by dehydration synthesis Glycogen, starch, cellulose © 2015 Pearson Education, Inc.

Figure 2-11 The Structures of Glucose.
a The structural formula of the straight-chain form b The structural formula of the ring form, the most common form of glucose KEY = Carbon = Oxygen = Hydrogen c A three-dimensional model that shows the organization of the atoms in the ring form

Figure 2-12a The Formation and Breakdown of Complex Sugars.
DEHYDRATION SYNTHESIS Glucose Fructose Sucrose a Formation of the disaccharide sucrose through dehydration synthesis. During dehydration synthesis, two molecules are joined by the removal of a water molecule.

Figure 2-12a The Formation and Breakdown of Complex Sugars (Part 1 of 2).
DEHYDRATION SYNTHESIS Glucose Fructose a Formation of the disaccharide sucrose through dehydration synthesis. During dehydration synthesis, two molecules are joined by the removal of a water molecule.

Figure 2-12a The Formation and Breakdown of Complex Sugars (Part 2 of 2).
DEHYDRATION SYNTHESIS Sucrose a Formation of the disaccharide sucrose through dehydration synthesis. During dehydration synthesis, two molecules are joined by the removal of a water molecule.

Figure 2-12b The Formation and Breakdown of Complex Sugars.
HYDROLYSIS Sucrose Glucose Fructose b Breakdown of sucrose into simple sugars by hydrolysis. Hydrolysis reverses the steps of dehydration synthesis; a complex molecule is broken down by the addition of a water molecule.

Breakdown of sucrose into simple sugars by hydrolysis.
Figure 2-12b The Formation and Breakdown of Complex Sugars (Part 1 of 2). HYDROLYSIS Sucrose b Breakdown of sucrose into simple sugars by hydrolysis. Hydrolysis reverses the steps of dehydration synthesis; a complex molecule is broken down by the addition of a water molecule.

Figure 2-12b The Formation and Breakdown of Complex Sugars (Part 2 of 2).
HYDROLYSIS Glucose Fructose b Breakdown of sucrose into simple sugars by hydrolysis. Hydrolysis reverses the steps of dehydration synthesis; a complex molecule is broken down by the addition of a water molecule.

Figure 2-13 The Structure of the Polysaccharide Glycogen.
Glucose molecules

Table 2-4 Carbohydrates in the Body.

2-10 Lipids Lipids Mainly hydrophobic molecules such as fats, oils, and waxes Made mostly of carbon and hydrogen atoms Include: Fatty acids Eicosanoids Glycerides Steroids Phospholipids and glycolipids © 2015 Pearson Education, Inc.

2-10 Lipids Fatty Acids Long chains of carbon and hydrogen with a carboxyl group (COOH) at one end Are relatively nonpolar, except the carboxyl group Fatty acids may be: Saturated with hydrogen (no covalent bonds) Unsaturated (one or more double bonds) Monounsaturated = one double bond Polyunsaturated = two or more double bonds © 2015 Pearson Education, Inc.

Figure 2-14a Fatty Acids. Lauric acid (C12H24O2) a Lauric acid demonstrates two structural characteristics common to all fatty acids: a long chain of carbon atoms and a carboxyl group (⎯ COOH) at one end.

Figure 2-14b Fatty Acids. Saturated Unsaturated b A fatty acid is either saturated (has single covalent bonds only) or unsaturated (has one or more double covalent bonds). The presence of a double bond causes a sharp bend in the molecule.

Figure 2-15 Prostaglandins.

2-10 Lipids Glycerides Fatty acids attached to a glycerol molecule
Triglycerides are the three fatty-acid tails Also called triacylglycerols or neutral fats Have three important functions Energy source Insulation Protection © 2015 Pearson Education, Inc.

Figure 2-16 Triglyceride Formation.
Glycerol Fatty acids Fatty Acid 1 Saturated Fatty Acid 2 Saturated Fatty Acid 3 Unsaturated DEHYDRATION SYNTHESIS HYDROLYSIS Triglyceride

2-10 Lipids Steroids Four rings of carbon and hydrogen with an assortment of functional groups Types of steroids Cholesterol Component of plasma (cell) membranes Estrogens and testosterone Sex hormones Corticosteroids and calcitriol Metabolic regulation Bile salts Derived from steroids © 2015 Pearson Education, Inc.

Figure 2-17 Steroids Have a Complex Four-Ring Structure.
Cholesterol b c Estrogen Testosterone

2-10 Lipids Phospholipids and Glycolipids
Diglycerides attached to either a phosphate group (phospholipid) or a sugar (glycolipid) Generally, both have hydrophilic heads and hydrophobic tails and are structural lipids, components of plasma (cell) membranes © 2015 Pearson Education, Inc.

Figure 2-18a Phospholipids and Glycolipids.
Nonlipid group Phosphate group Glycerol Fatty acids a The phospholipid lecithin. In a phospholipid, a phosphate group links a nonlipid molecule to a diglyceride.

Figure 2-18b Phospholipids and Glycolipids.
Carbohydrate Glycerol Fatty acids b In a glycolipid, a carbohydrate is attached to a diglyceride.

Figure 2-18c Phospholipids and Glycolipids.
Hydrophilic heads c In large numbers, phospholipids and glycolipids form micelles, with the hydrophilic heads facing the water molecules, and the hydrophobic tails on the inside of each droplet. Hydrophobic tails Phospholipid Glycolipid WATER

Table 2-5 Representative Lipids and Their Functions in the Body.

2-11 Proteins Proteins Are the most abundant and important organic molecules Contain basic elements Carbon (C), hydrogen (H), oxygen (O), and nitrogen (N) Basic building blocks 20 amino acids © 2015 Pearson Education, Inc.

2-11 Proteins Seven Major Protein Functions Support Buffering Movement
Structural proteins Movement Contractile proteins Transport Transport (carrier) proteins Buffering Regulation of pH Metabolic Regulation Enzymes Coordination and Control Hormones Defense Antibodies © 2015 Pearson Education, Inc.

2-11 Proteins Protein Structure Long chains of amino acids
Five components of amino acid structure Central carbon atom Hydrogen atom Amino group (—NH2) Carboxyl group (—COOH) Variable side chain or R group © 2015 Pearson Education, Inc.

Structure of an Amino Acid
Figure 2-19 Amino Acids. Structure of an Amino Acid Amino group Central carbon Carboxyl group R group (variable side chain of one or more atoms)

2-11 Proteins Hooking Amino Acids Together
Requires a dehydration synthesis between: The amino group of one amino acid and the carboxyl group of another amino acid Forms a peptide bond Resulting molecule is a peptide © 2015 Pearson Education, Inc.

Figure 2-20 The Formation of Peptide Bonds
Peptide Bond Formation Glycine (gly) Alanine (ala) DEHYDRATION SYNTHESIS HYDROLYSIS Peptide bond © 2015 Pearson Education, Inc. 86

2-11 Proteins Protein Shape Primary structure Secondary structure
The sequence of amino acids along a polypeptide Secondary structure Hydrogen bonds form spirals or pleats Tertiary structure Secondary structure folds into a unique shape Quaternary structure Final protein shape — several tertiary structures together © 2015 Pearson Education, Inc.

Figure 2-21 Protein Structure.
A1 A2 A3 A4 A5 A6 A7 A8 A9 Linear chain of amino acids a Primary structure. The primary structure of a polypeptide is the sequence of amino acids (A1, A2, A3, and so on) along its length. a A1 A2 A3 A4 Hydrogen bond A5 Hydrogen bond A9 A8 A7 A6 A 10 A2 A6 A1 A3 A5 A7 A9 OR A11 A12 A13 A14 Alpha helix Beta sheet b Secondary structure. Secondary structure is primarily the result of hydrogen bonding along the length of the polypeptide chain. Such bonding often produces a simple spiral, called an alpha helix (α helix) or a flattened arrangement known as a beta sheet (β sheet). Alpha helix OR Heme units c Tertiary structure. Tertiary structure is the coiling and folding of a polypeptide. Within the cylindrical segments of this globular protein, the polypeptide chain is arranged in an alpha helix. Hemoglobin (globular protein) Collagen (fibrous protein) d Quaternary structure. Quaternary structure develops when separate polypeptide subunits interact to form a larger molecule. A single hemoglobin molecule contains four globular subunits. Hemoglobin transports oxygen in the blood; the oxygen binds reversibly to the heme units. In collagen, three helical polypeptide subunits intertwine. Collagen is the principal extracellular protein in most organs.

Figure 2-21ab Protein Structure (Part 1 of 2).
A1 A2 A3 A4 A5 A6 A7 A8 A9 Linear chain of amino acids a Primary structure. The primary structure of a polypeptide is the sequence of amino acids (A1, A2, A3, and so on) along its length. Hydrogen bond A2 A6 A1 A3 A5 A7 A9 Alpha helix b Secondary structure. Secondary structure is primarily the result of hydrogen bonding along the length of the polypeptide chain. Such bonding often produces a simple spiral, called an alpha helix (α helix) or a flattened arrangement known as a beta sheet (β sheet).

Figure 2-21ab Protein Structure (Part 2 of 2).
A1 A2 A3 A4 A5 A6 A7 A8 A9 Linear chain of amino acids a Primary structure. The primary structure of a polypeptide is the sequence of amino acids (A1, A2, A3, and so on) along its length. A1 A2 A3 A4 Hydrogen bond A5 A9 A8 A7 A6 A 10 A11 A12 A13 A14 Beta sheet b Secondary structure. Secondary structure is primarily the result of hydrogen bonding along the length of the polypeptide chain. Such bonding often produces a simple spiral, called an alpha helix (α helix) or a flattened arrangement known as a beta sheet (β sheet).

Figure 2-21cd Protein Structure (Part 1 of 2).
Alpha helix Heme units c Tertiary structure. Tertiary structure is the coiling and folding of a polypeptide. Within the cylindrical segments of this globular protein, the polypeptide chain is arranged in an alpha helix. Hemoglobin (globular protein) d Quaternary structure. Quaternary structure develops when separate polypeptide subunits interact to form a larger molecule. A single hemoglobin molecule contains four globular subunits. Hemoglobin transports oxygen in the blood; the oxygen binds reversibly to the heme units. In collagen, three helical polypeptide subunits intertwine. Collagen is the principal extracellular protein in most organs.

Figure 2-21cd Protein Structure (Part 2 of 2).
Alpha helix Heme units Collagen (fibrous protein) c Tertiary structure. Tertiary structure is the coiling and folding of a polypeptide. Within the cylindrical segments of this globular protein, the polypeptide chain is arranged in an alpha helix. d Quaternary structure. Quaternary structure develops when separate polypeptide subunits interact to form a larger molecule. A single hemoglobin molecule contains four globular subunits. Hemoglobin transports oxygen in the blood; the oxygen binds reversibly to the heme units. In collagen, three helical polypeptide subunits intertwine. Collagen is the principal extracellular protein in most organs.

2-11 Proteins Fibrous Proteins Globular Proteins
Structural sheets or strands Globular Proteins Soluble spheres with active functions Protein function is based on shape Shape is based on sequence of amino acids © 2015 Pearson Education, Inc.

Figure 2-21d Protein Structure.
Heme units Hemoglobin (globular protein) Collagen (fibrous protein) d Quaternary structure. Quaternary structure develops when separate polypeptide subunits interact to form a larger molecule. A single hemoglobin molecule contains four globular subunits. Hemoglobin transports oxygen in the blood; the oxygen binds reversibly to the heme units. In collagen, three helical polypeptide subunits intertwine. Collagen is the principal extracellular protein in most organs.

2-11 Proteins Enzyme Function Enzymes are catalysts
Proteins that lower the activation energy of a chemical reaction Are not changed or used up in the reaction Enzymes also exhibit: Specificity — will only work on limited types of substrates Saturation Limits — by their concentration Regulation — by other cellular chemicals © 2015 Pearson Education, Inc.

1 Substrates bind to active site of enzyme S2 S1 Substrates
Figure 2-22 A Simplified View of Enzyme Structure and Function (Part 1 of 4). 1 Substrates bind to active site of enzyme S2 S1 Substrates ENZYME Active site

Enzyme-substrate complex
Figure 2-22 A Simplified View of Enzyme Structure and Function (Part 2 of 4). 2 Once bound to the active site, the substrates are held together and their interaction facilitated S1 S2 ENZYME Enzyme-substrate complex

Figure 2-22 A Simplified View of Enzyme Structure and Function (Part 3 of 4).
Substrate binding alters the shape of the enzyme, and this change promotes product formation PRODUCT ENZYME

4 Product detaches from enzyme; entire process can now be repeated
Figure 2-22 A Simplified View of Enzyme Structure and Function (Part 4 of 4). 4 Product detaches from enzyme; entire process can now be repeated PRODUCT ENZYME

2-11 Proteins Cofactors and Enzyme Function Cofactor Coenzyme Isozymes
An ion or molecule that binds to an enzyme before substrates can bind Coenzyme Nonprotein organic cofactors (vitamins) Isozymes Two enzymes that can catalyze the same reaction © 2015 Pearson Education, Inc.

2-11 Proteins Effects of Temperature and pH on Enzyme Function
Denaturation Loss of shape and function due to heat or pH © 2015 Pearson Education, Inc.

2-11 Proteins Glycoproteins and Proteoglycans Glycoproteins
Large protein + small carbohydrate Includes enzymes, antibodies, hormones, and mucus production Proteoglycans Large polysaccharides + polypeptides Promote viscosity © 2015 Pearson Education, Inc.

2-12 Nucleic Acids Nucleic Acids
Are large organic molecules, found in the nucleus, which store and process information at the molecular level Deoxyribonucleic acid (DNA) Determines inherited characteristics Directs protein synthesis Controls enzyme production Controls metabolism Ribonucleic acid (RNA) Controls intermediate steps in protein synthesis © 2015 Pearson Education, Inc.

2-12 Nucleic Acids Structure of Nucleic Acids
DNA and RNA are strings of nucleotides Nucleotides Are the building blocks of DNA and RNA Have three molecular parts A pentose sugar (deoxyribose or ribose) Phosphate group Nitrogenous base (A, G, T, C, or U) © 2015 Pearson Education, Inc.

Figure 2-23a Nucleotides and Nitrogenous Bases.
Nucleotide structure The nitrogenous base may be a purine or a pyrimidine. Phosphate group Sugar Nitrogenous base

Figure 2-23b Nucleotides and Nitrogenous Bases.
Purines A Adenine G Guanine

Figure 2-23c Nucleotides and Nitrogenous Bases.
Pyrimidines C Cytosine Thymine (DNA only) T Uracil (RNA only) U

2-12 Nucleic Acids DNA and RNA
DNA is double stranded, and the bases form hydrogen bonds to hold the DNA together Sometimes RNA can bind to itself but is usually a single strand DNA forms a twisting double helix Complementary base pairs Purines pair with pyrimidines DNA Adenine (A) and thymine (T) Cytosine (C) and guanine (G) RNA Uracil (U) replaces thymine (T) © 2015 Pearson Education, Inc.

Figure 2-24 The Structure of Nucleic Acids.
Phosphate group Deoxyribose Adenine Thymine Hydrogen bond DNA strand 1 DNA strand 2 a RNA molecule. An RNA molecule has a single nucleotide chain. Its shape is determined by the sequence of nucleotides and by the interactions among them. Cytosine Guanine b DNA molecule. A DNA molecule has a pair of nucleotide chains linked by hydrogen bonding between complementary base pairs.

2-12 Nucleic Acids Types of RNA Messenger RNA (mRNA)
Transfer RNA (tRNA) Ribosomal RNA (rRNA) © 2015 Pearson Education, Inc.

Table 2-6 Comparison of RNA with DNA.

2-13 High-Energy Compounds
Nucleotides Can Be Used to Store Energy Adenosine diphosphate (ADP) Two phosphate groups; di- = 2 Adenosine triphosphate (ATP) Three phosphate groups; tri- = 3 Phosphorylation Adding a phosphate group to ADP with a high-energy bond to form the high-energy compound ATP Adenosine triphosphatase (ATPase) The enzyme that catalyzes the conversion of ATP to ADP © 2015 Pearson Education, Inc.

Figure 2-25 The Structure of ATP.
Adenine Ribose Phosphate Phosphate Phosphate Adenosine High-energy bonds Adenosine monophosphate (AMP) Adenosine diphosphate (ADP) Adenosine triphosphate (ATP) Adenine Phosphate groups Ribose Adenosine

An Introduction to the Chemical Level of Organization

Similar presentations

Presentation on theme: "An Introduction to the Chemical Level of Organization"— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

An Introduction to the Chemical Level of Organization

Similar presentations

Presentation on theme: "An Introduction to the Chemical Level of Organization"— Presentation transcript:

Similar presentations

About project

Feedback