Chapter 6 Notes The Chemistry of Life

Composition of Matter Matter - Everything in the universe is composed of matter Matter is anything that occupies space or has mass Mass – quantity of matter an object has Weight – pull of gravity on an object

Elements Elements: Pure substance that consists of one type of atom (oxygen), and cannot be broken down chemically into simpler kinds of matter More than 100 elements (92 naturally occurring) Only four of the elements – Carbon, Hydrogen, Oxygen, and Nitrogen – make up 96% of the mass of a human.

Elements Atomic Number: # of Protons (+) An Element in the Periodic Table Section 2-1 Atomic Number: # of Protons (+) Atomic Mass: # of Protons (+) and Neutrons (0) To find the # of Neutrons (0): Atomic Mass – Atomic # = # of Neutrons (0)

Atoms: The Building Blocks of Elements Atoms: Basic unit of matter, is the smallest particle of an element that has the characteristics of that element, and is made of subatomic particles (protons “+”, neutrons “0”, and electrons “-”) Atoms contain equal #’s of electrons “-” and protons “+” (no charge)

Atoms: The Nucleus Nucleus: Central core of the atom Contains the protons and the neutrons (Protons “+” charge, Neutrons “0” charge)

Atoms: The Electron Cloud Electrons are found In the electron cloud around the nucleus (“-” charge) 1st level 2 electrons max 2nd level 8 electrons max 3rd level 18 electrons max

Atoms: The Electron Cloud Ex.: Oxygen – Atomic #8 = 8 electrons - 1st energy level (2 electrons) - 2nd energy level (6 electrons) Atoms contain equal numbers of electrons and protons; therefore, they have no net charge.

ATOMS

Isotopes Isotopes: Atoms of the same element that have a different number of neutrons. Ex: Carbon 12 6p and 6n Carbon 13 6p and 7n To find the number of neutrons, subtract the number of protons from the Mass # 13 – 6p = 7n

Carbon Isotopes Figure 2-2 Isotopes of Carbon 6 electrons 6 protons Section 2-1 Nonradioactive carbon-12 Nonradioactive carbon-13 Radioactive carbon-14 6 electrons 6 protons 6 neutrons 6 electrons 6 protons 7 neutrons 6 electrons 6 protons 8 neutrons

Compounds Compound: substance formed by the chemical combination of two or more elements. Compounds form between elements so they can become stable. An atom becomes more stable when its outermost energy level is full, such as having eight electrons in the second level.

Bonding Chemical Bonds - Ionic Bond: when one or more electrons are transferred from one atom to another. -Ions: positively and negatively charged atoms Ex. Na(+) Cl(-) (table salt) -Covalent Bond: Forms when electrons are shared by atoms to become stable (water H20) -A molecule is a group of atoms held together by a covalent bond

Ionic Bond

Covalent Bond

Chemical Reactions Chemical reactions occur when bonds are formed or broken, causing substances to recombine into different substances. (Examples: Metabolism and Photosynthesis)

Mixtures Mixture: A material composed of two or more elements or compounds, in which the individual components retain their own properties. Ex. Salt and Pepper Mixture Ex. Earth’s Gases

Solutions Solutions: Is a mixture in which one or more substances (solutes) are distributed evenly in another substance (solvent). -Ex. Salt water ( Salt is the solute – substance that is dissolved, Water is the solvent – substance in which the solute dissolves)

Suspensions Suspensions: Mixtures of water and non-dissolved materials. -Ex. Blood: transports un-dissolved particles throughout the body

Acids and Bases pH Scale: is a measure of how acidic or basic a solution is. (0 – 14) 0 – 6: Acids, higher number of hydrogen ions 8 – 14: Bases, higher number of hydroxide ions 7: Neutral, not acidic or basic Buffer: Weak acids or bases, that can react with strong acids or bases to prevent sharp sudden changes in pH

pH Scale

Water A water molecule (H2O), is made up of three atoms --- one oxygen and two hydrogen. H O 1

Importance of Water Water is perhaps the most important compound in living things. Water is polar. The electrons in water are not shared equally – the electrons are attracted by the oxygen atom more strongly than by the hydrogen atoms. Water can dissolve many ionic compounds, such as salt, yet can also dissolve many other polar molecules such as sugar.

Importance of Water Water molecules also attract other water molecules. The attraction of opposite between hydrogen and oxygen forms a weak bond called a hydrogen bond. Hydrogen bonds are important because they help hold proteins together and moving water throughout plants.

Hydrogen Bonds Cohesion: Attraction of molecules of the same substance. -Ex. Water droplets -Ex. Insects walking on water

Hydrogen Bonds Adhesion: Attraction of molecules of different substances. -Ex. Water in a glass container

Importance of Water Water resists temperature changes. It is like an insulator that helps maintain a steady environment when conditions fluctuate. Because cells exist in an aqueous environment, this property of water is extremely important to cellular functions as it helps cells maintain homeostasis.

Importance of Water Water expands when it freezes. Water is one of the few substances that expands when it freezes. This property of water breaks down rocks, which then helps form soil.

Importance of Water The properties of water make it an excellent vehicle for carrying substances in living systems. One way to move substances is by diffusion. Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration.

Carbon Compounds Carbon Atoms: In order to become stable, a carbon atom forms four covalent bonds that fill its outer energy level. This property makes a huge number of carbon structures possible. Macromolecule: Monomers join together to form polymers Four groups of organic compounds: Carbohydrates, lipids, nucleic acids, and proteins

Carbon Compounds Carbohydrates: Living things use carbohydrates as main source of energy, also can be used for structural purposes. -Ex. Starches and Sugars 1. Monosaccharide: (Single sugars Ex. Glucose, Fructose, and Galactose) 2. Polysaccharide: Linked to monosaccharides (Ex. Glycogen or Animal starch, plants make cellulose)

Carbon Compounds Lipids: Fats and oils, used to store energy, insulation, and protective coating. Non-soluble (Ex. Water and oil)

Carbon Compounds Nucleic Acids: Macromolecules that contain hydrogen, nitrogen, oxygen, carbon, and phosphorous. Nucleotides: 3 parts (5 carbon sugar, phosphate group, and a nitrogen base) Two types DNA and RNA

Carbon Compounds Proteins: Provide structure for tissues and organs and carry out cell metabolism; made of amino acids. - 20 different amino acids - Amino Acids combine to make proteins.

Chemical Reactions and Enzymes Chemical Reactions: Process that changes or transforms chemicals into other chemicals. Reactants: Elements or compounds that start the reaction Products: The end result of the reactants

2.4 Enzymes Catalyst: A substance that speeds up the rate of a chemical reaction. (Enzymes and Energy are catalysts) - Enzymes: Proteins found in living things that speed up chemical reactions that take place in cells, speed the reactions in digestion of food, affect synthesis of molecules, and storage and release of energy.