Chapter 2: Chemistry, Matter, and Life

Overview

Key Terms acid chemistry ion salt amino acid colloid isotope solute anion compound lipid solution aqueous denaturation molecule solvent atom electrolyte nucleotide steroid base electron neutron substrate buffer element pH suspension carbohydrate enzyme protein valence catalyst glucose proton cation glycogen radioactive

Chemistry Science that deals with matter’s composition and properties Used to understand normal and abnormal body function

Elements Learning Outcomes Define a chemical element. Describe the structure of an atom.

Na Elements 11 Sodium 22.99 Matter The stuff from which the universe is made Elements All of the different types of matter Identified by names or chemical symbols Also identified by number Described and organized in the periodic table 11 Sodium Na 22.99

Appendix 1 Periodic Table of the Elements What is the symbol and number for carbon?

Table 2-1 Some elements found in the human body. Name Symbol Select Functions Oxygen O Participates in ATP production Carbon C Building block of organic compounds Hydrogen H Participates in acid-base balance Nitrogen N Present in protein, DNA, RNA, and ATP Calcium Ca Builds bones and teeth Potassium K Needed for nerve impulse conduction Sodium Na Chlorine Cl Found in stomach acid Iron Fe Carries oxygen in red blood cells

Elements Atoms Smallest subunits of elements Cannot be broken down or changed by ordinary chemical and physical means

Elements Atomic Structure Nucleus At atom’s center Composed of Protons; positively charged Neutrons; not charged Electrons Negatively charged Orbit in energy levels around nucleus Determine atom’s chemical reactivity

Figure 2-1 The oxygen atom. How does the proton number of this atom compare with the electron number?

O Elements 8 Oxygen 16.00 Atomic Number Equal to the number of protons in an atom’s nucleus Also represents the number of electrons orbiting the nucleus No two elements share the same atomic number Oxygen’s nucleus contains 8 protons. Its atomic number is 8.

Elements Energy Levels Regions around an atom’s nucleus where electrons orbit Each region has space for a specific number of electrons. The first energy level has room for 2 electrons. The second energy level has room for 8 electrons. An atom is most stable when its energy levels are filled with electrons.

Elements Energy Levels Hydrogen has only one energy level with room for 1 more electron. Carbon’s first energy level is full. Carbon’s second energy level has room for 4 more electrons. Hydrogen Carbon Total number of electrons 1 6 Number of electrons in first energy level 2 Number of electrons in second energy level 4

Elements Energy Levels An atom will form chemical bonds with other atoms to fill its outermost energy level. An atom will donate, accept, or share electrons to fill its outermost energy level.

Figure 2-2 Examples of atoms. How many electrons does oxygen need to complete its outermost energy level? How does magnesium achieve a stable outermost energy level?

✓ Elements Checkpoints 2-1 What are atoms? 2-2 What are three types of particles found in atoms?

? Elements Pop Quiz 2.1 Which element makes up the greatest percentage of body weight? Nitrogen Oxygen Potassium Sodium

? Elements Pop Quiz Answer 2.1 Which element makes up the greatest percentage of body weight? Nitrogen Oxygen Potassium Sodium

Chemical Bonds Learning Outcomes Differentiate between ionic and covalent bonds. Define an electrolyte. Differentiate between molecules and compounds.

Chemical Bonds An atom forms chemical bonds with other atoms to fill its outermost energy level with electrons. Electrons may be transferred between atoms. Electrons may be shared between atoms.

C Chemical Bonds Valence The number of bonds an atom needs to fill its outermost energy level. Example A carbon atom has 6 electrons. Its outermost energy level contains 4 electrons. It needs 4 more electrons to fill its outermost energy level. Carbon’s valence is 4. 6 Carbon C 12.01

Chemical Bonds Na+ Cl– Ionic bonds Form when one atom transfers electrons to another atom The atom that donates an electron becomes a positively charged cation. The atom that accepts an electron becomes a negatively charged anion. The ionic bond is the attraction between oppositely charged ions. Na+ Cl–

Figure 2-3 Ionic bonding. How many electrons are in the outermost energy level of a sodium atom? Of a chlorine atom?

Chemical Bonds Electrolytes Compounds that separate into ions in solution Term also used to refer to the ions themselves Example Sodium chloride (NaCl) is an electrolyte. When NaCl is added to water, it separates into Na+ and Cl– ions. Both Na+ and Cl– ions are electrolytes.

Chemical Bonds Ions in the body Ions play important physiologic roles in body fluid. Homeostasis maintains proper ion concentration. Examples Ion Functions Ca2+ Blood clotting, muscle contraction HCO3– pH regulation

Chemical Bonds Ions in the body Ions conduct electric currents in body fluid. Measurement of a tissue’s electrical activity is used to diagnose disease. Examples Electrocardiogram A record of the heart’s electrical activity Electroencephalogram A record of the brain’s electrical activity

Chemical Bonds Covalent bonds Form when two atoms share electrons The most common chemical bond in the body Types: Nonpolar covalent bond Electrons are shared equally. Polar covalent bond Electrons are shared unequally.

Figure 2-4 A nonpolar covalent bond. How many electrons are needed to complete the energy level of each hydrogen atom?

Figure 2-5 Formation of water. How many hydrogen atoms bond with an oxygen atom to form water?

Chemical Bonds Molecules Chemicals composed of two or more atoms held together with covalent bonds Examples: O2, H2O Compounds Chemicals composed of two or more different atoms held together by ionic or covalent bonds Examples: NaCl, H2O, CO2

✓ Chemical Bonds Checkpoints 2-3 What are the two types of chemical bonds and how are they formed? 2-4 What happens when an electrolyte goes into solution? 2-5 What are molecules and what are compounds?

? Chemical Bonds Pop Quiz 2.3 What bond forms between two atoms that share their electrons equally? Hydrogen bond Ionic bond Nonpolar bond Polar bond

? Chemical Bonds Pop Quiz Answer 2.3 What bond forms between two atoms that share their electrons equally? Hydrogen bond Ionic bond Nonpolar bond Polar bond

Mixtures Learning Outcomes Define mixture. List the three types of mixtures and give two examples of each. Explain why water is so important in metabolism.

Mixtures Mixture A blend of two or more chemicals, elements, or ions Type Definition Example Solution Homogeneous mixture of a solute dissolved in a solvent NaCl dissolved in water Suspension Heterogeneous mixture that will separate unless shaken Red blood cells in blood plasma Colloid Heterogeneous mixture in which suspended particles remain distributed because of their small size Intracellular fluid

Mixtures The importance of water Most abundant compound in body Critical in all physiologic processes Deficiency (dehydration) threatens health Universal solvent Stable liquid at ordinary temperatures Participates in body’s chemical reactions

✓ Mixtures Checkpoints 2-6 What is the difference between solutions and suspensions? 2-7 What is the most abundant compound in the body?

? Mixtures Pop Quiz 2.6 Which term describes a substance that dissolves another substance? Mixture Solute Solution Solvent

? Mixtures Pop Quiz Answer 2.6 Which term describes a substance that dissolves another substance? Mixture Solute Solution Solvent

Acids, Bases, and Salts Learning Outcomes Compare acids, bases, and salts. Explain how the numbers on the pH scale relate to acidity and alkalinity. Explain why buffers are important in the body.

Acids, Bases, and Salts HCl  H+ + Cl– NaOH  Na+ + OH– A substance that donates hydrogen ions Base A substance that donates hydroxide ions and accepts hydrogen ions Salt A substance formed by a reaction between an acid and a base HCl  H+ + Cl– NaOH  Na+ + OH– HCl + NaOH  NaCl + H2O

Acids, Bases, and Salts The pH scale Measures the relative concentrations of hydrogen and hydroxide ions in a solution Scale from 0 (most acidic) to 14 (most basic) Each unit represents a 10-fold change Normal body fluid pH range is between 7.35 and 7.45 Acidosis: body fluid pH <7.35 Alkalosis: body fluid pH >7.45

Figure 2-6 The pH scale. What happens to the amount of hydroxide ion (OH–) present in a solution when the amount of hydrogen ion (H+) increases?

Acids, Bases, and Salts Buffers Chemicals that prevent sharp changes in H+ concentration Are important in maintaining a relatively constant pH in body fluids

✓ Acids, Bases, and Salts Checkpoints 2-8 What number is neutral on the pH scale? What kind of compound measures lower than this number? Higher? 2-9 What is a buffer?

? Acids, Bases, and Salts Pop Quiz 2.8 Which substance always accepts hydrogen ions? An acid A base A buffer A salt

? Acids, Bases, and Salts Pop Quiz Answer 2.8 Which substance always accepts hydrogen ions? An acid A base A buffer A salt

Isotopes and Radioactivity Learning Outcomes Define radioactivity, and cite several examples of how radioactive substances are used in medicine.

Isotopes and Radioactivity Forms of an element that have the same atomic number but different atomic weight Different atomic weight because of a different number of neutrons May be stable or unstable (radioactive) Examples Isotope Proton Number Neutron Number Atomic Weight Carbon-12 6 12 Carbon-13 7 13 Carbon-14 8 14

Isotopes and Radioactivity Emission of atomic particles from an isotope Use of radioactive isotopes Used in the treatment of cancer Radiation penetrates and destroys tumor cells. Used in diagnosis X-rays penetrate tissues and produce an image on film.

Isotopes and Radioactivity ✓ Isotopes and Radioactivity Checkpoints 2-10 What word is used to describe isotopes that give off radiation?

Isotopes and Radioactivity ? Isotopes and Radioactivity Pop Quiz 2.11 A form of an element that differs in its atomic weight from other forms of that same element is a(n) ____________. Compound Ion Isotope Molecule

Isotopes and Radioactivity ? Isotopes and Radioactivity Pop Quiz Answer 2.11 A form of an element that differs in its atomic weight from other forms of that same element is a(n) ____________. Compound Ion Isotope Molecule

Organic Compounds Learning Outcomes Name the three main types of organic compounds and the building blocks of each. Define enzyme. Describe how enzymes work. List the components of nucleotides and give some examples of nucleotides.

Organic Compounds Living matter contains 26 of 92 natural elements. 96% of body weight—4 elements 4% of body weight—9 elements 0.1% of body weight—13 elements

Organic Compounds Chemistry of Living Matter Hydrogen, oxygen, carbon, and nitrogen make up 96% of body weight. Organic Compounds Chemical compounds found in living things Built on the element carbon Main types Carbohydrates Lipids Proteins

Figure 2-7 The body’s chemical composition by weight.

Organic Compounds Carbohydrates Monosaccharides Basic units of carbohydrates Disaccharides Two monosaccharides linked together Polysaccharides Many monosaccharides linked together Carbohydrate Examples Monosaccharide Glucose Disaccharide Sucrose and lactose Polysaccharide Glycogen and starch

Figure 2-8 Examples of carbohydrates. What are the building blocks (monomers) of disaccharides and polysaccharides?

Organic Compounds Lipids (fats) Triglycerides Simple fat composed of glycerol and three fatty acids Phospholipids Complex lipid containing phosphorus Steroids Contain rings of carbon atoms (e.g., cholesterol) Lipid Functions Triglyceride Insulates body, protects organs, stores energy Phospholipid Main component of cell membranes Steroid Regulate body function (e.g., cortisol, sex hormones)

Figure 2-9 Lipids. How many carbon atoms are in glycerol?

Organic Compounds Proteins Contain nitrogen (and sometimes sulfur or phosphorus) Found as structural materials and metabolically active compounds Composed of chains of amino acids held together by peptide bonds The overall three-dimensional shape of a protein is caused by folding

Figure 2-10 Proteins. What part of an amino acid contains nitrogen?

Organic Compounds Enzymes Are proteins that speed up (catalyze) chemical reactions Work on specific substrates Are not used up or changed during a chemical reaction Work via the “lock-and-key” mechanism Denature in harsh conditions (e.g., extremes of temperature or pH)

Figure 2-11 Diagram of enzyme action. How does the shape of the enzyme before the reaction compare with its shape after the reaction?

Organic Compounds Nucleotides Composed of A nitrogenous base A sugar (usually ribose or deoxyribose) A phosphate group Building blocks of DNA and RNA One type is a component of ATP.

Figure 2-12 Nucleotides. What does the prefix tri- in adenosine triphosphate mean?

✓ Organic Compounds Checkpoints 2-11 What element is the basis of organic chemistry? 2-12 What are the three main categories of organic compounds? 2-13 What is an enzyme? 2-14 What is in a nucleotide and what compounds are made of nucleotides?

? Organic Compounds Pop Quiz 2.12 Which element is the basis of organic chemistry? Carbon Hydrogen Nitrogen Oxygen

? Organic Compounds Pop Quiz Answer 2.12 Which element is the basis of organic chemistry? Carbon Hydrogen Nitrogen Oxygen

Case Study Learning Outcomes Use the case study to discuss the importance of body fluid quantity and composition.

Case Study Some terms that illustrate the importance of body fluid quantity and composition: Dehydration Hematocrit Hypernatremia Hypotension Tachycardia

Word Anatomy Learning Outcomes Show how word parts are used to build words related to chemistry, matter, and life.

Word Anatomy Word Part Meaning Example hom/o- same Homogeneous mixtures are the same throughout. heter/o- different Heterogeneous solutions are different throughout. hydr/o water Dehydration is a deficiency of water. phil to like Hydrophilic substances “like” water. phobia to fear Hydrophobic substances “fear” water. sacchar/o sugar A monosaccharide consists of one simple sugar. glyc/o glucose, sweet Glycogen is a storage form of glucose. de to remove Denaturation of a protein removes its ability to function. -ase suffix used in naming enzymes A lipase is an enzyme that acts on lipids.

? Organic Compounds Pop Quiz 2.15 A substance that has a name ending in -ase is most likely a(n)? Carbohydrate Enzyme Lipid Nucleotide

? Organic Compounds Pop Quiz Answer 2.15 A substance that has a name ending in -ase is most likely a(n)? Carbohydrate Enzyme Lipid Nucleotide