Chemistry of Life

Basic Structures of Life Matter: Matter: Has mass and occupies space Element: Element: Pure substance Compound: Compound: Chemical combination of two or more substances

Protonspositive Protons carry a positive charge. Electronsnegative Electrons carry a negative charge. Neutronsneutral Neutrons are electrically neutral. Protons, Electrons, and Neutrons

View animation on “All About Atoms” Nucleus Atoms

Atomic Number and Weight Each element carries a unique number of protons. Atomic number: Atomic number: The number of protons in the nucleus Atomic weight: Atomic weight: The number of protons + the number of neutrons

Question Which of the following is a pure substance that cannot be broken down into two or more substances? A. Compound B. Element C. Matter D. Atom

Chemical Bonds Ionic Covalent Hydrogen

Ionic Bonds transfers Ionic bonds occur when one atom transfers an electron to another atom

Ionic Bonds

Electrically charged atoms are called ions. positivecations positive = cations negativeanions negative = anions Compounds that ionize in water and create such a solution are called electrolytes.

Covalent Bonds View animation on “Chemical Bonds: Ionic and Covalent” share Covalent bonds occur when two atoms share one or more pairs of electrons.

Covalent Bonds Covalent bonds are stronger than ionic bonds; they are used to create many of the chemical structures of the body.

Hydrogen Bonds A hydrogen bond is a weak attraction between a slightly positive hydrogen atom in one molecule and a slightly negative oxygen or nitrogen atom in another.

View animation on “Hydrogen Bonds” Hydrogen Bonds

Unpaired electrons give water a partial negative charge near the oxygen atom and the two hydrogen atoms create a slight positive charge on the other side. polar Water is electrically neutral but has an uneven distribution of electrons making it a polar molecule.

Question What bond occurs when one atom transfers an electron to another atom? A. Hydrogen B. Chemical C. Ionic D. Covalent

To function, the body needsENERGY

Energy Energy is stored in the bonds of molecules. This is potential energy. Chemical reactions release the energy. Energy in motion is kinetic energy. All of the chemical reactions in the body are called metabolism.

Energy Catabolism – breaking down complex compounds into simpler ones. Catabolic reactions release energy. Anabolism – building larger and more complex chemical molecules from smaller subunits. Anabolic reactions require energy.

Organic and Inorganic Compounds Most of the molecules of the body form organic compounds. Organic compounds carbon Organic compounds contain carbon. Inorganic compounds Inorganic compounds include water, oxygen, carbon dioxide, and acids and bases.

Types of Chemical Reactions Synthesis Synthesis: A + B → AB Decomposition Decomposition: AB → A + B Exchange Exchange: AB + CD → AC + BD All three of these chemical reactions can go in either direction: They are reversible reactions.

Water Water comprises 50% of an adult’s body weight. Fluids in the body consist of chemicals dissolved in water. Water has unique characteristics solven It is a solvent. lubricant It is a lubricant. changes temperature slowly It changes temperature slowly.

Acids Strong acid Weak acid Acids and bases are among the most important chemicals in the body. Acids release hydrogen when dissolved in water.

Bases OH− ions accept H+ ions View animation on “Acids and Bases”

pH Scale

Acidity or alkalinity is expressed in terms of pH pH scale ranges from 0 to 14. pH greater than 7 = basic (alkaline); higher pH = more OH − ions pH of 7 = neutral; equal numbers of H + and OH − ions pH less than 7 = acidic; lower pH value = more H + ions Normal pH range of the human body is extremely narrow: ranging from 7.35 to 7.45.

Organic Compounds Carbohydrates Lipids Proteins Nucleic acids

Organic Compounds The term organic is used to describe the vast array of compounds that contain carbon. Carbon serves as the basis for thousands of molecules of varying size and shape.

Carbohydrates Carbohydrates Carbohydrates are the body’s main energy source. Glucose Glucose is the primary form of sugar used by cells. Glycogen Glycogen is the stored form of glucose.

Lipids A reserve energy supply Provide structure to cells Insulate nerves Serve as vitamins Cushion organs

Proteins Proteins are the most abundant and important organic compound in the body. amino acids Proteins consist of amino acids.

Amino Acid

Question What is the body’s primary energy source? A. Carbohydrates B. Proteins C. Lipids D. Water

Nucleic Acids DNARNA Nucleic acids include DNA and RNA. They consist of thousands of nucleotides. Nucleotides consist of a five-carbon sugar, a phosphate group, and one of several nitrogen bases.

Nucleic Acids In DNA, the sugar is deoxyribose; in RNA, the sugar is ribose. DNA is the largest molecule in the body. DNA carries the genetic code. RNA copies the genetic code of DNA to direct protein synthesis.

Adenosine Triphosphate Adenosine triphosphate (ATP) is a nucleotide that stores energy. Adenosine triphosphate (ATP) consists of a base, a sugar, and a phosphate group. The phosphate groups are connected with high-energy bonds.

ATP: Releasing Energy When one of these bonds is broken through a chemical reaction, energy is released that can be used for work. After the bond is broken through a chemical reaction, adenosine triphosphate (ATP) becomes adenosine diphosphate (ADP) and a single phosphate.

ATP: Repairing Bonds View animation on “Breakdown of ATP” The cell uses some of the energy released from the breakdown of the nutrients in food to reattach the third phosphate to the ADP, again forming ATP.

Question Which statement is true? A. DNA and RNA are nucleotides. B. ATP is a nucleic acid. C. Nucleic acids are inorganic compounds. D. Nucleotides consist of a sugar, a phosphate group, and a nitrogen base.