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Chemistry in Biology. 6. The Big Idea. Atoms are the foundation of biological chemistry and the building blocks of all living things. Main Idea #1. Matter is composed of tiny particles called atoms. Atoms.
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The Big Idea • Atoms are the foundation of biological chemistry and the building blocks of all living things.
Main Idea #1 • Matter is composed of tiny particles called atoms.
Atoms • Chemistry is the study of matter. Matter is anything that takes up space and has mass. • Matter is composed of atoms. • Even though there are many types of atoms, they all have the same basic structure. • Neutrons and protons fill the nucleus, while electrons circle outside the nucleus in energy shells.
Atoms (continued...) • Neutrons are particles that have no charge, and protons are positively charged. • Electrons have a negative charge. • Under normal circumstances, the number of electrons equals the number of protons keeping the atom neutral in charge.
Elements • An element is a pure substance that cannot be broken down into other substances by physical or chemical means. • There are over 100 known elements, 92 of which occur naturally. • Each element has a unique name and symbol. • The four most important elements to living things are carbon (C), hydrogen (H), oxygen (O), and nitrogen (N). Together, these four compose over 90% of the mass of living matter..
Periodic Table • The atomic number of an element is equal to the number of protons it contains. This usually appears on the periodic table just above the chemical symbol. • The atomic mass of an element is equal to the number of protons plus the number of neutrons. This is located under the element’s name on the periodic table.
Isotopes • Atoms of the same element that have the same number of protons and electrons but have a different number of neutrons are called isotopes.
Radioactive Isotopes • When a nucleus breaks apart, it gives off radiation that can be detected and used for many applications.
Compounds • A compound is a pure substance formed when two or more different elements combine. • Compounds are always formed from a specific combination of elements in a fixed ratio. • Compounds cannot be broken down into simpler compounds or elements by physical means.
Chemical Bonds • Covalent Bonds - chemical bond that forms when electrons are shared • A molecule is a compound in which the atoms are held together by covalent bonds.
Chemical Bonds • Ionic Bonds - Electrical attraction between two oppositely charged atoms or groups of atoms • Most ionic compounds are crystalline at room temperature and have higher melting points than molecular compounds formed by covalent bonds.
Chemical Bonds • Some atoms tend to donate or accept electrons more easily than other atoms. • The elements identified as metals tend to donate electrons. • The elements identified as nonmetals tend to accept electrons.
van der Waals Forces • When molecules come close together, the attractive forces between slightly positive and negative regions pull on the molecules and hold them together. • The strength of the attraction depends on the size of the molecule, its shape, and its ability to attract electrons.
Main Idea #2 • Chemical reactions allow living things to grow, develop, reproduce, and adapt.
Chemical Reactions • A chemical reaction is the process by which atoms or groups of atoms in substances are reorganized into different substances. • Clues that a chemical reaction has taken place include the production of heat or light, and formation of a gas, liquid, or solid.
Chemical Equations • Chemical formulas describe the substances in the reaction and arrows indicate the process of change. • Reactants are the starting substances, on the left side of the arrow. • Products are the substances formed during the reaction, on the right side of the arrow.
Chemical Equations • Glucose and oxygen react to form carbon dioxide and water. • Is this equation written correctly?
Balancing Equations • The law of conservation of mass states matter cannot be created or destroyed. • The number of atoms of each element on the reactant side must equal the number of atoms of the same element on the product side.
Energy of Reactions • The activation energy is the minimum amount of energy needed for reactants to form products in a chemical reaction.
Energy of Reactions • This reaction is exothermic and released heat energy. • The energy of the product is lower than the energy of the reactants.
Energy of Reactions • This reaction is endothermic and absorbed heat energy. • The energy of the products is higher than the energy of the reactants.
Enzymes • A catalyst is a substance that lowers the activation energy needed to start a chemical reaction. • It does not increase how much product is made and it does not get used up in the reaction. • Enzymes are biological catalysts.
Enzymes • The reactants that bind to the enzyme are called substrates. • The specific location where a substrate binds on an enzyme is called the active site. • The active site changes shape and forms the enzyme-substrate complex, which helps chemical bonds in the reactants to be broken and new bonds to form.
Enzymes • To sum it up: • Enzyme and substrate link together. • Chemical reaction occurs • Substrate becomes something new and the enzyme is let go. • The enzyme can be reused.
Enzymes • Factors such as pH, temperature, and other chemicals affect enzyme activity. • When enzymes are exposed to one of these factors, they may become denatured. • Denaturing causes the enzyme to not be as effective or possibly quit working altogether.
Main Idea #3 • The properties of water make it well suited to help maintain homeostasis in an organism.
Water’s Polarity • Molecules that have an unequal distribution of charges are called polar molecules. • Polarity is the property of having two opposite poles. • A hydrogen bond is a weak interaction involving a hydrogen atom and a fluorine, oxygen, or nitrogen atom.
Cohesion and Adhesion • Cohesion is the attractive force between particles of the same kind. This property allows water to bulge from the top of a filled glass without spilling over. • Adhesion is the attractive force between unlike substances. • Together these properties make it possible for water to move upwards against the force of gravity in a narrow tube. • This phenomenon is called capillarity.
Homogenous Mixtures • A homogenous mixture is one that has a uniform composition throughout. • A solvent is a substance in which another substance is dissolved. • A solute is the substance that is dissolved in the solvent. Food coloring dissolved in water forms a homogenous mixture.
Heterogenous Mixtures • In a heterogeneous mixture, the components remain distinct. • In a suspension, the components will eventually settle to the bottom. • In a colloid, the particles will not settle over time. Examples include fog, smoke, butter, mayonnaise, milk, paint, and ink.
Acids and Bases • Substances that release hydrogen ions (H+) when dissolved in water are called acids. • Substances that release hydroxide ions (OH–) when dissolved in water are called bases.
The pH Scale • The measure of concentration of H+ in a solution is called pH. • Acidic solutions have pH values lower than 7. • Basic solutions have pH values higher than 7. • Buffers are mixtures that can react with acids or bases to keep the pH within a particular range.
Main Idea #4 • Organisms are made up of carbon-based molecules.
Why is Carbon Important? • The element carbon is a component of almost all biological molecules.
Why is Carbon Important? • Carbon has four electrons in its outermost energy level. • One carbon atom can form four covalent bonds with other atoms. • Carbon compounds can be in the shape of straight chains, branched chains, and rings.
Why is Carbon Important? • Carbon atoms can be joined to form carbon molecules. • Macromolecules are large molecules formed by joining smaller organic molecules together. • Polymers are molecules made from repeating units of identical or nearly identical compounds linked together by a series of covalent bonds.
Making or Breaking Molecules • Condensation Reaction - process of combining small molecules to form large molecules, and in the process, create water; also called dehydration synthesis • One molecule releases H+ and the other molecule releases OH-. • The two molecules become joined by a C-O-C bridge. • The H+ and the OH- combine to form water (H2O).
Making or Breaking Molecules • Hydrolysis - process that breaks down large molecules by using water • Opposite of a condensation reaction • Water is added to complex molecules to break the bonds that hold them together.
Molecules of Life • There are four main classes of organic compounds that are needed for living things: • Carbohydrates • Proteins • Lipids • Nucleic acids • All of these are mainly composed of carbon, hydrogen, oxygen, and nitrogen.
Carbohydrates • Carbohydrates are composed of C, H, and O in a 1:2:1 ratio for each carbon atom—(CH2O)n. • They can exist as monosaccharides, disaccharides, or polysaccharides. • Ex.’s sugar, pasta, potatoes
Carbohydrates • Monosaccharides are more commonly called “simple sugars.” • Common monosaccharides are: glucose, fructose, and galactose • These monosaccharides have the same chemical formula, C6H12O6, but they have very different structures. • Compounds like these structures, having the same chemical formula but different forms, are called isomers.
Carbohydrates • When two monosaccharides combine in a condensation reaction, a disaccharide is formed. GLUCOSE + FRUCTOSE = SUCROSE • When you combine three or more monosaccharides, a polysaccharide is formed. • Animals store glucose in the form of the polysaccharide glycogen. It is hundreds of glucose molecules stuck together. • Plants store glucose in the polysaccharide form of starch.
Lipids • Lipids are molecules made mostly of carbon and hydrogen. • Lipids are made up of building blocks called fatty acids. • One end of the fatty acid is hydrophilic (water loving) while the other end is hydrophobic (water fearing). • Saturated fats contain only single bonds (C-C). • Unsaturated fats contain at least one double bond (C=C). • Ex.’s oils, fats, steroids, waxes
Lipids • A triglyceride is a fat if it is solid at room temperature and an oil if it is liquid at room temperature. • Cell membranes are primarily composed of a lipid called a phospholipid. • Other examples of lipids include waxes and steroids.
Proteins • A protein is a compound made of small carbon compounds called amino acids. Ex.’s meat, beans, eggs • Amino acids are small compounds that are made of carbon, nitrogen, oxygen, hydrogen, and sometimes sulfur. • Amino acids have a central carbon atom. • One of the four carbon bonds is with hydrogen. • The other three bonds are with an amino group (–NH2), a carboxyl group (–COOH), and a variable group (–R).
Proteins • Dipeptides are formed when two amino acids join together. • The bond that holds them together is called a peptide bond. • Long chains of amino acids are called polypeptides. • Proteins are made up of one or more polypeptides.
Nucleic Acids • Nucleic acids are complex macromolecules that store and transmit genetic information. • DNA (deoxyribonucleic acid) contains information that is essential for almost all cell activities, including cell division. • RNA (ribonucleic acid) stores and transfers information that is essential for the manufacturing of proteins. • Both DNA and RNA are composed of thousands of nucleotides. • Each nucleotide is composed of a phosphate group, a 5-carbon sugar, and a ring-shaped nitrogen base.