Matter and Energy: Chemistry Review Unit 2, Part 1

Ions During an ionic bond, one of the atoms will give up one or more of its electrons, while the other atom will gain those given up. In doing so, this affects the overall charge of each individual atom. An atom with a charge is called an ion. An atom that has more electrons than protons will have a negative charge, while an atom with more protons than electrons will have a positive charge. What do opposites always do? Attract!

Bond Types The first picture shows an ionic bond, where electrons move from the hydrogen atoms to the oxygen atom to fill its outermost energy level. The second picture shows a covalent bond, where two hydrogens take turns having full energy levels by sharing their single valence electron.

Properties of Matter Remember that all matter has properties, and these properties fit into two categories: physical and chemical. Characteristics such as the tendency to rust, reactivity with water, pH, and number of valence electrons are chemical properties. Characteristics like color, size, shape, texture, and mass are physical.

Changes in Matter Just like with properties, there are physical and chemical changes. If you change a substance without changing its identity or composition, you have made a physical change. For example, if you cut a piece of paper, you now have two pieces, but you still have paper. If you change a substance and end up with an entirely different substance, you have made a chemical change. Eating a plate of spaghetti is a chemical change, as it breaks down into new substances while being digested.

Solutions Solutions are made of two parts: the solute (dissolved substance) and the solvent (the dissolver). Solutions are mixtures that are the same throughout but have variable compositions, depending on how much solvent or solute is present.

Water: The Universal Solvent? Why is it that some substances dissolve in water and others do not? The nature of water prohibits some substances from doing this. Water is called a polar molecule because the oxygen atom is just a little negative and the hydrogens are just a little positive, making the molecule have charged regions, or poles. Polar molecules attract other polar molecules. For example, sugar molecules are polar, and so, are dissolved easily in water. Oil is not polar, and so, does not dissolve in water, or is insoluble.

Solubility in Ionic Compounds When an ionic molecule is placed in water, the positive end of the water is attracted to the negative ion of the other molecule, like salt. The negative end of the water is drawn to the positive ion in salt. The attraction is strong enough to break the bond between the atoms in salt. So, a solution of table salt and water is made of water molecules, sodium ions, and chloride ions.

Acids and Bases ACIDS A substance with more hydrogen ions than hydroxide ions is an acid. Acids have a pH less than 7. Acids usually have a sour taste. BASES A solution with more hydroxide ions than hydrogen ions is a base. Bases have a pH greater than 7. Bases are usually slippery and taste bitter.

The pH Scale The pH scale ranges from 0-14. Substances below 7 are acids, substances above 7 are bases, and substances right at 7 are neutral (such as water and salt). The pH of solutions is important to living organisms. The pH of water and soil determines what organisms can live there. Also, pH can influence the chemical reactions that can occur in an organism. In order for digestion to occur in the human stomach, the pH has to be about 2. Human blood has to be just above a pH of 7.

Why All The Chemistry Review? An understanding of atomic structure, behavior, properties, and solubility is important in biology because many living organisms consist of 70% or more water, and many substances are dissolved in that water. The chemical reactions that make up life processes take place in water solutions. Ions dissolved in the water of organisms are important to life functions, such as impulse conduction, muscle contraction, and photosynthesis.

Biological Chemistry Unit 2, Part 2

Section 2.2 Objectives Section 2.2: Biological Chemistry Relate the structure of a carbon atom to the complexity of carbon compounds. Compare the structures and functions of carbohydrates, lipids, proteins, and nucleic acids. Distinguish between condensation and hydrolysis reactions.

Carbon Compounds Carbon compounds are also known as organic compounds because they are found in almost all things living. There are a few exceptions to this. For example, CO2 is not considered to be an organic compound.

Isomers Isomers are substances that have the same chemical formula, but different structures. Examples are maltose, lactose, and sucrose. All have the formula C12H22O11. Because the structures are different, the properties change.

Biomolecule Group 1: Carbohydrates A carbohydrate (aka, carb) is an organic compound composed of C, H, and O with the ratio of 2H:1O Examples include starch, sugars, glucose The function of carbs is to serve as an energy source for metabolic functions Simple sugars are called monosaccharides. Glucose (C6H12O6) is a monosaccharide. What is a disaccharide? What is a polysaccharide?

Biomolecule Group 2: Lipids Lipids, or fats, are organic compounds composed of C, H, and O, but the numbers of H are much higher than in carbs. Examples include fats, oils, waxes, cholesterol, and steroids. Animals produce solid fats, while plants produce liquid fats. The function of fats is to serve as an energy reserve, provide insulation, and protect nerves. Fat molecules are a combo of fatty acids and glycerol, and are insoluble in water.

Biomolecule Group 3: Proteins Proteins make up the largest group of organic molecules. Their function is to make muscle, carry out chemical reactions by acting as catalysts, fight disease, and transport materials throughout organisms. The shape of a protein affects its function. Proteins contain C, H, O, N, and S.

Amino acids are the building blocks of protein Amino acids are the building blocks of protein. There are 20 total and they combine in different ways to produce numerous proteins. When amino acids bond together, they form a peptide. When two amino acid chains join together, they form a dipeptide. When multiple chains of amino acids join, they form a polypeptide.

Biomolecule Group 4: Nucleic Acids There are two nucleic acids: DNA and RNA. DNA - deoxyribonucleic acid; genetic code RNA - ribonucleic acid; carry out instructions for building proteins More on these later!

Reactions of Biological Compounds What’s wrong with this problem? C12H22O11 is made of two monosaccharides with the formula C6H12O6. What happened? A condensation reaction is when an -OH is broken from one molecule and -H from another. These join to form H2O. This occurs when joining small molecules to form larger molecules. A hydrolysis reaction requires the addition of water for the reaction to take place. It occurs when larger molecules are broken into smaller molecules. It’s important because complex substances must be simplified to be digested by the body.

Enzymes Unit 2, Part 3

Section 2.3 Objectives Section 2.3: Energy and Reactions Discuss the relationship between a reaction and activation energy. Describe the means by which an enzyme carries out a cellular reaction.

Enzymes Enzymes are proteins that lower the activation energy (energy needed to start a reaction) of a reaction, acting as catalysts to speed the reaction up. They allow reactions to occur at normal cell temperatures, rather than being heated up. Enzymes are very specific for the reaction they aid. They can be used over and over again, and their shape affects the reaction.

In a cellular reaction, the reactants are called substrates In a cellular reaction, the reactants are called substrates. Enzymes are named by adding -ase to the name of the substrate involved. For example, in the reaction changing maltose to glucose, the enzyme used is maltase.

What Good Are Enzymes? The active site (part of the enzyme’s surface) fits with the substrate involved, called the lock and key model. Recently, it’s been called the induced fit model because the enzyme can change shapes slightly like a flexible key. 2 AA’s H2O Dipeptide Enzyme Enzyme

Coenzymes Enzymes sometimes require helpers, or coenzymes. Coenzymes are usually vitamin molecules or fragments. They are reusable as well. Coenzymes can join enzymes or transfer atoms from substrates. To function properly, cells must carry out thousands of reactions and do so at the right time. How might the the body run differently if enzymes were not required for reactions?

If enzymes were not required for certain reactions, many cell reactions could only take place at very hot or very cold body temperatures. Also, the reactants and products of many reactions would not be reusable and the body would have to continually be working to make more of the necessary substances.

Biochemistry and Enzymes The effectiveness of an enzyme can be altered by changing body chemistry. For example, temperatures that are too high, pH levels that are outside the required range, or an excess of certain chemicals in the blood can all affect an enzyme’s ability to carry out a reaction by changing its shape. When that happens, we say that the enzyme has been denatured.