1. Chapter 2
The Chemistry of Life

2. Atoms
Atoms
The study of chemistry begins with the basic unit of matter, the atom.
Placed side by side, 100 million atoms would make a row only about 1 centimeter long.
Atoms contain subatomic particles that are even smaller.

3. Atoms The subatomic particles that make up atoms are
Protons –Positively Charged
Neutrons - No Charge
Electrons – Negatively Charged

4. Atoms The subatomic particles in a helium atom.
Helium atoms contain protons, neutrons, and electrons. The positively charged protons and uncharged neutrons are bound together in the dense nucleus, while the negatively charged electrons move in the space around the nucleus.

5. Atoms Protons and neutrons have about the same mass, 1 amu
Strong forces bind protons and neutrons together to form the nucleus, which is at the center of the atom.

6. Atoms The electron with 1/1840 the mass of a proton.
Electrons are in constant motion in the space surrounding the nucleus because of the energy of their motion.

7. Atoms
Because atoms have equal numbers of electrons and protons, and because these subatomic particles have equal but opposite charges, atoms are neutral.

8. Elements and Isotopes Elements and Isotopes
A chemical element is a pure substance that consists entirely of one type of atom.
Elements are represented by a one- or two-letter symbol.
C stands for carbon.
Na stands for sodium.

9. Elements and Isotopes
The number of protons in an atom of an element is the element's atomic number.
Carbon has 6 protons, so its atomic number is 6.

10. Elements and Isotopes Isotopes
Atoms of the same element that differ in the number of neutrons they contain are known as isotopes.
The sum of the protons and neutrons in the nucleus of an atom is called its mass number.

11. Elements and Isotopes Isotopes of Carbon 6 electrons 6 protons
Because they have the same number of electrons, these isotopes of carbon have the same chemical properties. The difference among the isotopes is the number of neutrons in their nuclei.
6 electrons
6 protons
6 neutrons
6 electrons
6 protons
7 neutrons
6 electrons
6 protons
8 neutrons

12. Chemical Compounds Chemical Compounds
In nature, most elements are found combined with other elements in compounds.
A chemical compound is a substance formed by the chemical combination of two or more elements in definite proportions.

13. Chemical Bonds Chemical Bonds
The atoms in compounds are held together by chemical bonds.
Bond formation involves the electrons that surround each atomic nucleus.
The electrons that are available to form bonds are called valence electrons.

14. Chemical Bonds The main types of chemical bonds are:
ionic bonds – transfer electrons
covalent bonds – share electrons

15. Chemical Bonds Sodium atom (Na) Chlorine ion (Cl-) Sodium ion (Na+)
Chlorine atom (Cl)
The chemical bond in which electrons are transferred from one atom to another is called an ionic bond. The compound sodium chloride forms when sodium loses its valence electron to chlorine.
Protons
Electrons
Charge
Protons
Electrons
Charge
Protons
Electrons
Charge
Protons
Electrons
Charge

16. Chemical Bonds
In a water molecule, each hydrogen atom forms a single covalent bond with the oxygen atom.
The chemical bond in which electrons are shared between atoms is called a covalent bond. In a water molecule, each hydrogen atom shares two electrons with the oxygen atom.

17. Chemical Bonds Ionic Bonds
An ionic bond is formed when one or more electrons are transferred from one atom to another.
An atom that loses electrons has a positive charge. 
An atom that gains electrons has a negative charge.
These positively and negatively charged atoms are known as ions.

18. Chemical Bonds Covalent Bonds
Sometimes electrons are shared by atoms instead of being transferred.
Sharing electrons means that the moving electrons actually travel in the orbitals of both atoms.

19. Chemical Bonds
A covalent bond forms when electrons are shared between atoms.
When the atoms share two electrons, the bond is called a single covalent bond.
When atoms share four electrons it is called a double bond.
When atoms share six electrons it is called a triple bond.

20. Chemical Bonds
The structure that results when atoms are joined together by covalent bonds is called a molecule.
A molecule is the smallest unit of most compounds.

21. Chemical Bonds Van der Waals Forces
When molecules are close together, a slight attraction can develop between the oppositely charged regions of nearby molecules.
Chemists call such intermolecular forces of attraction van der Waals forces, after the scientist who discovered them.

22. Chemical Bonds Although van der Waals forces are not as strong
as ionic bonds or covalent bonds, they can hold
molecules together, especially when the molecules
are large.

23. Chemical Bonds
For example, van der Waals forces form between the molecules on the surface of a gecko’s foot and the molecules on the surface of the wall.
The combined strength of all the van der Waals forces allows the gecko to grip the wall.
Photo Credit: top: Kellar Autumn & Ed Florance; bottom: © Mark Moffett/Minden Pictures, Inc.

24. 2-2 Properties of Water Water stores heat efficiently
Water retains heat longer than many other substances
Water is essential in maintaining homeostasis

25. 2-2 Properties of Water Polarity
Water is considered to be a polar molecule due to an uneven distribution of charge.
The electrons in a water molecule are shared unevenly between hydrogen and oxygen.
The polarity of water makes it effective at dissolving other polar substances such as sugars, ionic compounds, and some proteins.

26. Polar Water Molecule + -

27. 2-2 Properties of Water
A hydrogen bond is the force of attraction between a positive charge of one molecule and negative charge of another.

28. 2-2 Properties of Water Cohesion and Adhesion
Cohesion is an attractive force that holds molecules of a single substance together, such as water molecules
Adhesion is the attractive force between two particles of different substances, such as water molecules and glass molecules.

29. 2-2 Properties of Water Solutions
A solution consists of a solute dissolved in a solvent
i.e. Chocolate milk
Milk is the solvent
Chocolate powder is the solute

30. 2-2 Properties of Water Acids and Bases Ionization of Water
Water ionizes into hydronium ions (H3O+) and hydroxide ions (OH–)

31. 2-2 Properties of Water Acids
Acidic solutions contain more hydronium ions (H3O+) than hydroxide ions (OH–)

32. 2-2 Properties of Water Bases
Basic solutions contain more hydroxide ions (OH–) than hydronium ions (H3O+).

33. 2-2 Properties of Water pH
Scientists have developed a scale for comparing the relative concentrations of hydronium ions (H3O+) and hydroxide ions (OH–) in a solution.
This scale is called the pH scale, and it ranges from 0 to 14.

35. 2-2 Properties of Water Buffers
Buffers are chemicals that neutralize the effects of an acid or a base by adding small amounts of the opposite (either an acid or a base) to a solution.

36. 2-3 Carbon Compounds Carbon is the element of life
Organic compounds – carbon containing
Inorganic compounds- carbon lacking
Carbon has 4 valence e-
Will make 4 strong covalent bonds
Carbon found in many forms
Straight chain
Branched chain

37. 2-3 Carbon Compounds Carbon found in many forms Carbon ring
Double bonded
Triple bonded

38. 2-3 Carbon Compounds Macromolecules – “giant molecules”
Small units called monomers, come together in a process called polymerization
They form polymers

39. 2-3 Carbon Compounds Carbohydrates (CHO) C1H2O1 Main energy source
Only source of brain food (glucose)
4cal/1gram
1 cal = amount of energy needed to raise 1g of water, 1 °C

40. 2-3 Carbon Compounds Carbohydrates Sugars
Monosaccharides – simple sugars, I ring of carbon
glucose
Disaccharides- 2 sugars, 2 rings
sucrose
Polysaccharides- many sugars
starches

41. 2-3 Carbon Compounds Lipids – Fats
Insulate, protect, shock absorber, energy storage, cell membranes
9cal/1gram

42. 2-3 Carbon Compounds Lipids Fatty Acid Chains
Unsaturated -CH=CH- (double bonds) -liquids
Saturated –CH2-CH2- (single bonds) -solids

43. 2-3 Carbon Compounds Nucleic Acids DNA, RNA Nucleotide 5 Carbon sugar
Nitrogen base
Phosphate group

44. 2-3 Carbon Compounds Proteins Building blocks of the body 4cal/1 gram
Made of Amino Acids- 20 A.A.
We produce 12 A.A.
8 essential A.A. we must consume
Enzymes
Varying functions in the body

45. 2-4 Chemical Reactions and Enzymes
Energy and Chemical Reactions
Chemical rxns always involve changes in chemical bonds
Reactants are substances that enter chemical reactions.
Products are substances produced by chemical reactions.

46. 2-4 Chemical Reactions and Enzymes
Energy and Chemical Reactions
Energy is released or absorbed whenever chemical bonds form or are broken
Some rxns release energy (exothermic)
Some rxns absorb energy (endothermic)

47. 2-4 Chemical Reactions and Enzymes
Energy and Chemical Reactions

48. 2-4 Chemical Reactions and Enzymes
Energy and Chemical Reactions
Activation Energy
Amount of energy necessary for a reaction to begin
Enzymes can lower activation energy level
A Catalyst is a substance that speeds up a chemical reaction
Enzymes are Catalysts