How many chemical elements are essential for life? 25.
Name the four elements that make up approximately 96% of your body weight. Oxygen, carbon, hydrogen, and nitrogen.
Name the subatomic particles that orbit the nucleus in different energy levels. Electrons.
Define the term compound. A substance formed when two or more chemical elements are chemically bonded together.
What is the most abundant compound on Earth? H2O.
Most of the compounds in living organisms contain at least 3 or 4 elements, name them. Proteins - enzymes, fat - storage of energy, nucleic acid - in DNA, carbohydrates - to make energy, or ATP.
If two electrons are in different energy levels, which electron has the most energy? The one furthest away from the nucleus.
Why do atoms form molecules and compounds? The electrons around them are unstable. They bond to become stable.
How many electrons does an atom desire in the first energy level? 2
If an atom has two energy levels, how many electrons does it desire in the second energy level? 0 or 8 If an atom has three energy levels, how many electrons does it desire in the third energy level? 0, 8, or 18
The interactions of unstable atoms usually result in atoms staying close together. What do we call these attractions? Chemical bonds
What do we call atoms that have an electrical charge resulting from a gain or loss of one or more electrons? Ionic bonds
What kind of bonds form when two atoms share one or more electrons? Covalent bonds
Define the term electronegativity. An atom's attraction for shared electrons
What kind of bond is formed when two atoms that don't have the same electronegativity share electrons? Nonpolar covalent bonds
What kind of bonds hold the two strands of DNA molecule together? Hydrogen bonds that create a protein's shape
What types of bonds help water to absorb a large amount of heat while warming up only a few degrees? High specific heat
What temperature is considered normal body temperature? 98.6 degrees Fahrenheit
Approximately what percentage of our body's weight is from water? 66%
What property does water have that gives it versatility as a solvent? Polarity
Define the term acid. A compound that donates hydrogen ions to solutions
What is the pH of the following: distiller water, the solution inside most living cells, stomach acid, human urine, normal human blood? 7.0, close to 7.0, between 1.0 and 3.0, 6.0, and 7.4
What is the pH range that blood can be before death occurs? Drops to 7.0 or rises to 7.8
How many covalent bonds are needed in order for a carbon atom to become stable? 4
What is a hydrocarbon? A compound of hydrogen and carbon
What are two atoms called if they have the same molecular formula but in a different structural formula? Isomers
Name the four main classes of macromolecules. Carbohydrates, lipids, proteins, and nucleic acids
What reaction is necessary to link monomers together to form polymers? Dehydration synthesis
What reaction is necessary to break macromolecules into polymers then into monomers? Hydrolysis reaction
What are the atomic building blocks of…