Biology Ch 2

1. Biology Ch 2 Chemistry of Life

2. matter • Matter is anything that occupies space and has mass • Mass is the quantity of matter an object has • Weight is the force produced by gravity acting on mass, not the same as mass • Chemical changes in matter are part of all life processes • Biologists study chemistry because all living things are made of matter just like nonliving things

3. elements • Elements are substances that cannot be broken down chemically into simpler kinds of matter • Around 30 elements are associated with life • Carbon • Oxygen • Hydrogen • Nitrogen

4. Periodic table • Elemental information is collected on the Periodic Table • Each element is represented with a chemical symbol • A chemical symbol is a 1-3 letter abbreviation • The symbol either comes from the current or the Latin name • Ex. Chlorine = Cl • Ex. Sodium = Na

6. atom • An atom is the simplest particle of an element that is still an element • The central region of an atom is the nucleus • A proton is a positively charged subatomic particle in the nucleus • A neutron is a neutral subatomic particle in the nucleus

7. Atomic and mass numbers • The atomic number tells the number of protons in an atom of an element • In a stable atom, protons = electrons, so the atomic number can tell electrons too • On the periodic table, the number often appears above the element symbol • The mass number tells the number of protons + the number of neutrons • On the periodic table, the number often appears below the element symbol

8. electrons • Small negatively charged particles in an atom are electrons • The number of negative electrons equals the number of positive protons, so a stable atom is neutrally charged (net charge) • Electrons move about the nucleus at high speeds in orbitals • An orbital is a 3D region around a nucleus that is a probable location of an electron • Energy level decreases with each orbital farther away from the nucleus • All orbitals combined produce an electron cloud

10. isotopes • All atoms of an element have the same number of protons • All atoms do not always have the same number of neutrons • Atoms of the same element that have a different number of neutrons are called isotopes

11. compounds • Naturally, elements do not exist alone, they combine with the same element or other elements to form compounds • Compounds are made of atoms of 2+ elements in fixed proportions • Ex H2O • Elements combine when their outer electron orbitals are not full • Compounds form when a chemical bond is created between two elements’ unfull outer electron orbitals • Noble gases on the periodic table are full and stable and do not form compounds

12. Covalent bond • A covalent bond forms when 2 atoms share 1+ pairs of electrons • Ex. Hydrogen needs 2 electrons in its outer orbital to be stable and oxygen needs 4. So with 1 oxygen and 2 hydrogen, each are stable

13. molecule • A molecule is the simplest part of a substance that retains all of the properties of that substance and can exist alone • All molecules share covalent bonds.

14. Ionic bond • An ionic bond forms when 2 atoms gain and lose electrons to form a compound • Again, the outer orbitals will not be full and looking for stability (more/less electrons) • An atom that is unbalanced and charged is an ion • An atom with more protons than electrons is a positive ion, cation • An atom with more electrons than protons is a negative ion, anion

15. Biology ch 2 Energy

16. energy • Energy is the ability to do work • Energy can exist in many forms • Electrical energy • Chemical energy • Thermal energy • Energy of Motion • Inside living organisms energy is converted from one form to another • Ex. After eating a meal, the chemical energy in food is changed to thermal, mechanical, etc. energy

17. States of matter • All atoms and molecules in all matter are moving • The motion of the atoms/molecules, and the spacing between them, determining a substance’s state • Solid • Liquid • Gas

18. States of matter • Solid substances will have a fixed shape and a fixed volume • Solid substacne atoms will move less than other, they will only vibrate • A liquid has a fixed volume but no fixed shape • Liquid substances will move more freely but the atoms will simply roll around one another • Gas substances have no fixed volume and no fixed shape • Gas substance atoms move rapidly with little contact; they will fill their space • Thermal energy (heat) must be applied to/taken away from a substance for it to change states

19. Energy transfer • Living things are carrying out many chemical reactions each day (metabolism) • In a chemical reaction, 1+ substances change to produce 1+ different substances • Chemical reaction can either continue to completion or reach a state of equilibrium • Energy is absorbed or released when chemical bonds are broken or formed • Reactants are the substances present before the chemical reaction • Products are the substances after the chemical reaction

20. Activation energy • Energy must be added for most reactions to begin • The amount of energy needed to start a reaction is the activation energy • For most reactions, this amount (activation energy) is large • Catalysts reduce the activation energy needed and help the reaction to proceed • An enzyme is a protein that speeds up metabolic reactions without being permanently changed or destroyed

22. Redox reactions • Many reactions that transfer energy in living things transfer electrons • Reaction in which electrons are transferred between atoms are redox reactions • An oxidation reaction occurs when a reactant loses 1+ electrons (more positive) • A reduction reaction occurs when a reactant gains 1+ electrons (more negative) • Oxidation and reduction reactions always occur together