Presentation on theme: "To understand biology, you MUST have a basic understanding of chemistry. Why?? Because each of your cells are able to function as a result of chemical."— Presentation transcript:
To understand biology, you MUST have a basic understanding of chemistry. Why?? Because each of your cells are able to function as a result of chemical reactions. If cells stop functioning – what happens? –HINT: look at the picture…
Chemistry & Biology Without Chemistry…there is no Biology!!!
I. In our study of chemistry, we will be concerned with MATTER and its transformations. A. Define matter: ANYTHING THAT TAKES UP SPACE AND HAS MASS (AMOUNT OF MATTER IN A GIVEN OBJECT)
B. What makes up matter? The basic unit of all matter is the ATOM. These in turn are composed of smaller parts: 1.) PROTON 2.) ELECTRON 3.) NEUTRON
C. Describe how these 3 parts are organized to make the structure of an atom: D. The 3 components of atoms also have an electrical charge. Protons have a POSITIVE charge, electrons have a NEGATIVE charge and neutrons have NO charge – they are neutral.
1.) In their “normal” state, the number of protons in an atom equals the number of ELECTRONS. This means that the atom is ELECTRICALLY NEUTRAL overall. + = Neutral p+e-
II. All matter is composed of atoms of one or more ELEMENTS. A.Define element: CANNOT BE REDUCED TO ANY SIMPLER SET OF SUBSTANCES B. The property that makes the element gold different from the element iron is the structure of their ATOMS! Gold atoms have 79 protons in their nuclei while iron atoms have only 26 protons.
1.) So, a gold nugget is really a HUGE collection of gold atoms each with 79 protons in their nucleus. A piece of iron would be a HUGE collection of iron atoms, each containing 26 protons in their nucleus.
2.) Because all elements have a different number of protons in their atoms, the number of protons an element has is called its ATOMIC number.
3.) The diagram that orders all elements according to their atomic number is called the PERIODIC TABLE. a.) In this diagram, each element is also assigned a symbol. For example, hydrogen is represented by H, oxygen by O, carbon by C, nitrogen by N, gold by Au, iron by Fe....and so on.
4.) So, elements are really defined by atoms with different numbers of protons. BUT, some elements can have different forms. a. For example, carbon atoms have 6 protons and most carbon atoms found in nature also have 6 neutrons in their nuclei. However, some carbon atoms have 6 protons and 8 neutrons. Carbon with this different number of neutrons behaves a little differently from the more common form. These forms of elements with different numbers of neutrons are called ISOTOPES.
C. KEY POINT: Everything in nature is made of the atoms of one or more elements.
III. Chemical Bonding: A. The part of chemistry that is most important to the study of biology is the way atoms of elements combine with one another. 1.) WHY do atoms combine (form chemical BONDS)? a. Atoms bond with each other because after bonding, they are more stable. b. The atoms are more stable due to the rearrangement of ELECTRONS.
c. So, it is really electrons that allow atoms to combine with one another. HOW??? 2. Electrons exist in ENERGY LEVELS around the nucleus of atoms. a. The number of energy levels depends on the atom – the more electrons, the more energy levels.
b. To keep it simple, we’ll focus on what “stabilizes” atoms. Atoms are more stable if their energy levels are filled. i. ) The first energy level requires 2 electrons to be full. ii.) All others outside the first require at least 8 electrons.
c. If the outermost energy level (or VALENCE LEVEL) is not full, the atom is unstable and reactive – this means that it will more easily bond with other atoms in an attempt to fill up its outer shell.
d.Example #1: Consider an atom of hydrogen. Hydrogen has 1 proton in its nucleus which means it has 1electron moving around the nucleus. Is hydrogen stable – why or why not? Example #2: Consider an atom of oxygen. Oxygen has 8 protons in its nucleus which means it has 8 electrons. Is oxygen stable – why or why not? Look it up on your periodic table!
2 electrons in first energy level & 6 electrons in 2 nd. Oxygen IS NOT stable because it’s outer most energy level has room for more electrons!!!!
B. Types of Chemical Bonds 1. COVALENT bonds: bond that is formed when atoms SHARE a pair of electrons.
a.Example #1: A hydrogen atom has 1 electron in its outer shell. To be stable, it needs 2. If this hydrogen atom encounters another hydrogen atom, they will bond with each other by sharing their electrons.
i.) This forms a hydrogen MOLECULE: a compound of a defined number atoms held together by covalent bonds (by SHARING electrons).
b. Example #2: Oxygen atoms have 8 electrons which means they have 2 in the first energy level and 6 in the next (or valence). This means that oxygen requires 2 electrons to be stable. When oxygen atoms encounter hydrogen atoms, one oxygen atom will share electrons with two hydrogen atoms. The result of this is one water molecule!
i.) This is why the chemical symbol/formula for water is H 2 O. Each water molecule consists of 2 hydrogen atoms and 1 oxygen atom sharing electrons and joined by COVALENT bonds.
c. Just because atoms are sharing electrons in a covalent bond, doesn’t mean they are sharing them equally!
i.) All atoms attract electrons to themselves differently. This is measured by a number called an atom’s ELECTRONEGATIVITY (EN). The HIGHER this number is, the more strongly the atom pulls electrons toward itself.
ii.) For example, in a water molecule, OXYGEN has a much higher EN than HYDROGEN. This means that oxygen tends to pull electrons toward itself and away from hydrogen.
Because the electrons have a NEGATIVE charge and are now closer to the oxygen atom, the oxygen end of every water molecule has a slight NEGATIVE charge and the hydrogen ends become slightly POSITIVLY charged.
When a molecule has a difference in charges at its ends, it is said to be POLAR and the atoms are said to be joined by a POLAR covalent bond. When the EN of atoms held together by covalent bonds is close and the ELECTRONS are shared equally, the molecule is said to be NONPOLAR and is held together by NONPOLAR covalent bonds.
iii.) Since all water molecules are polar, what happens when several water molecules are together?
The POSITIVE hydrogen ends of one water molecule are attracted to the NEGATIVE oxygen ends of another.
This attraction holds water molecules together by what is called a HYDROGEN bond. These types of bonds are found in many important biological molecules such as DNA and proteins.
2. IONIC bonds: bonds that are formed when electrons are LOST and GAINED. Examine the diagram in your notes. Describe (in detail) what is occurring. Pay attention to the electrical charges of each atom!
BONUS QUESTIONS! Initial instability part “a” 1.What is the key point of part “a”? Show energy levels & how neither element is stable 2.What is the arrow showing? How of e- from Na could fit w/ Cl energy level Electron Transfer 1.What is the key point of part “b”? Creation of Ionic bonds & ions 2.What is the arrow showing? Transfer of e- stabilizes both Na & Cl 3.What do the “+” & the “-” mean? Show how the loss of an e- creates a positive ion & gain of e- creates a negative ion.
a. This occurs when the differences in EN between atoms is so extreme that ELECTRONS are pulled off one atom and attach to the atom that is attracting them! b. Example: Sodium (Na) has 11electrons. This means it has 2 electrons in the first level, 8 in the second and only 1 in the third. Chlorine (Cl) has 17 electrons. 2 in the first level, 8 in the second, 7 in the third.
i.) So, to be stable, sodium just needs to LOSE one electron and chlorine needs to GAIN one. This is what happens when sodium and chlorine come into contact – sodium gives up an electron to chlorine.
ii.) However, since the sodium atom has lost an electron (which has a negative charge), it is no longer neutral. It has more protons than electrons which means it has a POSITIVE charge. Since the chlorine atom gained an electron, it now has a NEGATIVE charge. iii.) An atom with a charge is called an ION.
iv.) Now, we have 2 atoms with different charges close to each other. The opposite charges attract and the two atoms stick together forming an IONIC bond between them. v.) 2 or more elements joined by ionic bonds are called an IONIC COMPOUND.
IV. Some Final Key Points… A. Molecules are 3- dimensional and have a variety of shapes. 1. The shape of molecules is very important because the ability of molecules to bind with one another is the basis of most functions in our bodies!
B. Notation in Chemistry 1. First, for each element there is a symbol that is used as shorthand. 2. When elements combine into molecules, we must represent how many atoms of each element make up one molecule. Examples…
a. 2 atoms of oxygen: O 2 b. 2 hydrogen and 1 oxygen: H 2 O c. 6 carbon, 12 hydrogen and 6 oxygen: C 6 H 12 O 6 3. What if we have 3 molecules of O 2 ? 3O 2 a. 12 molecules of H 2 O? 12 H 2 O b. 6 molecules of CO 2 (CARBON DIOXIDE) 6 CO 2
4. An example of a chemical reaction: 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 a. The molecules on the left of the arrow are called the REACTANTS. These molecules are reacting with one another to form the PRODUCTS on the right side of the arrow. b. The arrow means YIELD. c. The reaction represented above is the overall reaction for the process of PHOTOSYNTHESIS where CARBON DIOXIDE and LIGHT are used by plants to make GLUCOSE (sugar) and OXYGEN.