1. Chapter 2
Chemistry of Life

2. KEY CONCEPT All living things are based on atoms and their interactions.

3. Biology
Biology: The study of life
In order to understand life your must have a basic understanding of chemistry

4. Matter and Energy
Matter: anything that occupies spaces and has mass
Everything around us is matter
Element: a pure substance that cannot be broken down into other substances by chemical means
ex. gold, helium, mercury

5. Living things consist of atoms of different elements.
An atom is the smallest basic unit of matter.
An element is one type of atom.
Four most common elements in living things
Carbon
Hydrogen
Nitrogen
Oxygen
Other elements are also found in living
Things, but in very small amounts.
These are called trace elements
Ex: calcium and iodine
Hydrogen atom (H) H O
Oxygen atom (O)

6. An atom has a nucleus and electrons.
The nucleus has protons (positive) and neutrons (no charge).
Electrons (negative) are in energy levels outside nucleus.
Oxygen atom (O)
Nucleus: 8 protons (+) 8 neutrons
outermost energy level: 6 electrons (-)
inner energy level: 2 electrons (-)

7. O A compound is made of atoms of different elements bonded together.
water (H2O)
A compounds properties may differ greatly from those of its component elements
Ex. NaCl O H _ +

8. A compound is made of atoms of different elements bonded together.
water (H2O)
carbon dioxide (CO2)

9. A compound is made of atoms of different elements bonded together.
water (H2O)
carbon dioxide (CO2)
many other carbon-based compounds in living things

10. Elements
Left alone atoms generally tend to hold as many protons and electrons.
This creates an atom with an electrically neutral charge because the positive charge of the protons and the negative charge of the electrons cancel each other out
The number of electrons is not always equal to the number of protons, because some elements tend to lose or gain electrons (these atoms are called Ions)

11. Isotopes
Some elements have alternative forms called Isotopes
Isotopes have the same number of protons in their atom but a different number of neutrons

12. Radioactive isotopes
Radioactive Isotope: isotope in which the nucleus decays (breaks down) over time, giving off radiation in the form of matter and energy
Ex. carbon-14
Radioactive isotopes have many uses in research and medicine because living cells use radioactive isotopes just as they would use the nonradioactive forms
They are like spies

13. Electron configuration
Electrons differ in the amount of energy they have and the how tightly they are held by the protons in the nucleus
Based in these properties electron are classified into different energy levels
The first and lowest energy level (nearest to the nucleus) can hold 2 electrons
The second level holds 8
If the outermost energy level is not full the element is considered chemically reactive

14. Electron configuration

15. Ions form when atoms gain or lose electrons.
An ion is an atom that has gained or lost one or more electrons.
positive ions: lose electrons
negative ions: gain electrons
Ionic bonds form between oppositely charged ions.
Sodium atom (Na)
Chlorine atom (CI)
Sodium ion (Na+)
Chloride ion (CI-)
Na loses an electron to CI
ionic bond
gained electron

16. Atoms share pairs of electrons in covalent bonds.
A covalent bond forms when atoms share a pair of electrons.
multiple covalent bonds
diatomic molecules
covalent bonds
Oxygen atom (O)
Carbon atom (C)
Carbon dioxide (CO2 )

17. Reaching Stability
All atoms want to be stable!
The goal of bonding atoms together is to create stability.
When atoms gain, lose, or share electrons, an attraction forms between the atoms, pulling them together to form a compound.
This attraction is called a chemical bond. A chemical bond is the force that holds atoms together in a compound.

18. Bonding Numbers of bonds
The number of bonds an atom can form usually equals the number of additional electrons that will fill its highest energy level.
Ex. a hydrogen atom can accept one additional electron so it can form only one bond
Ex. an oxygen atom can accept 2 additional electrons so its can form up to 2 bonds

19. KEY CONCEPT Water’s unique properties allow life to exist on Earth.

20. Life depends on hydrogen bonds in water.
Water is a polar molecule.
Polar molecules have slightly charged regions. O H _ +
Nonpolar molecules do not have charged regions.
Hydrogen bonds form between slightly positive    hydrogen atoms and slightly negative oxygen atoms.

21. Hydrogen bonds are responsible for three important properties of water.
High specific heat: this means water must absorb large amounts of energy in order for the temperature to change
Cohesion: water molecules are attracted to other water molecules
Adhesion: water molecules are attracted to other substances

22. Low density of ice Properties of Water
Density is the amount of matter in a given volume
In most substances the solid state is more dense than the liquid state
But in water the solid form is much less dense than the liquid
This is why ice floats on water

23. Many compounds dissolve in water.
A solution is formed when one substance dissolves in another.
A solution is a homogeneous mixture.
Solvents dissolve other substances.
Solutes dissolve in a solvent.
solution

24. “Like dissolves like.”
Polar solvents dissolve polar solutes.
Nonpolar solvents dissolve nonpolar solutes.
Polar substances and nonpolar substances generally remain separate.

25. KEY CONCEPT Carbon-based molecules are the foundation of life.

26. Carbon atoms have unique bonding properties.
Carbon forms covalent bonds with up to four other atoms, including other carbon atoms.
Carbon-based molecules have three general types of structures. (Organic Molecules)
straight chain
branched chain
ring

27. Many carbon-based molecules are made of many small subunits bonded together.
Monomers are the individual subunits.
Polymers are made of many monomers.

28. Four main types of carbon-based molecules are found in living things.
Carbohydrates are made of carbon, hydrogen, and oxygen.

29. Four main types of carbon-based molecules are found in living things.
Carbohydrates are made of carbon, hydrogen, and oxygen.
Carbohydrates include sugars and starches.
Monosaccharides are simple sugars.
Polysaccharides include starches, cellulose, and glycogen.

30. Polysaccharides (complex carbohydrates)
Long polymer chains made up of simple sugar monomers
Ex. Starch is a polysaccharide made entirely of glucose molecules
Starch is found in plant cells
Starch chains branch and coil up into loop
Animal cell do not contain starch they contain glycogen
Glycogen is a polysaccharide that helps animals store excess sugar

31. Carbohydrates can be broken down to provide energy for cells.
Some carbohydrates are part of cell structure.
Polymer (starch)
Starch is a polymer of glucose monomers that often has a branched structure.
Polymer (cellulose)
Cellulose is a polymer of glucose monomers that has a straight, rigid structure
monomer

32. Carbohydrates
Some polysaccharides in plants serve as building materials
Ex. Cellulose- protects cells and stiffens the plant
Cellulose is also made of glucose molecules (like glycogen and starch)
Most animals, including people cannot digest cellulose because they lack the molecule necessary to break the bonds between the glucose molecules in cellulose
But some organisms like cows and termites can break down cellulose and use it for nutrients because they have microorganisms in their digestive tracts that are able to break down the cellulose

33. Carbohydrates

34. Carbohydrates
Almost all carbohydrates are hydrophilic because there are many hydroxyl found on them
This means that monosaccharides and disaccharides dissolve easily in water
On the other hand cellulose and some forms of starch are such large molecules that they do not dissolve in water

35. Lipids
Characteristics of lipids
Lipids are water avoiding
Hydrophobic: meaning water fearing
Uses of lipids
They can act as a boundary that surrounds and contains the watery contents in your cell
They can also store energy in your body

36. Many contain carbon chains called fatty acids.
Lipids are nonpolar molecules that include fats, oils, and cholesterol.
Many contain carbon chains called fatty acids.
Fats and oils contain fatty acids bonded to glycerol.
Triglyceride

37. Lipids Unsaturated Fat Fats
Fat consists of a three-carbon backbone called glycerol attached to three fatty acids
Fatty acids contain long hydrocarbon chains
Some fats are solid at room temperature
Some fats are oil and liquids at room temperature
Unsaturated Fat

38. Lipids have several different functions.
broken down as a source of energy
make up cell membranes
used to make hormones

39. Fats and oils have different types of fatty acids.
saturated fatty acids
unsaturated fatty acids

40. Lipids
Saturated Fats
A fat in which all three fatty acid chains contain the maximum possible number of hydrogen atoms
All the carbon atoms in the fatty acid chains form single bonds with each other, and the rest of their bonds are with hydrogen atoms.
Saturated fats are solid at room temperature
Unsaturated Fats
Contains less than the maximum number of hydrogen atoms in one or more of its fatty acid chains, because some of its carbon atoms are double bonded to each other
Usually liquids at room temperature

41. Lipids
Steroids
A lipid molecule in which the carbon skeleton forms four fused rings
While all steroids have the core of four rings, they differ in the kinds of functional groups that are attached to the rings
Steroids can circulate in your body as chemical signals
Ex. estrogen and testosterone

42. Lipids
Maybe the best known steroid is cholesterol
It is an essential molecule found in the membranes that surround your cells
It is also the starting point from which your body produces other steroids

43. Proteins are polymers of amino acid monomers.
Twenty different amino acids are used to build proteins in organisms.

44. Proteins are polymers of amino acid monomers.
Twenty different amino acids are used to build proteins in organisms.
Amino acids differ in side groups, or R groups.

45. Proteins are polymers of amino acid monomers.
Twenty different amino acids are used to build proteins in organisms.
Amino acids differ in side groups, or R groups.
Amino acids are linked by peptide bonds.

46. Proteins

47. Proteins differ in the number and order of amino acids.
Amino acids interact to give a protein its shape.
hydrogen bond
Hemoglobin
Incorrect amino acids change a protein’s structure and function.

48. Proteins Protein Shape
A protein in a simple form of an amino acid linked together cannot function properly
A functional protein consists of one or more polypeptides precisely twisted, folded and coiled into a unique shape
An unfavorable change in temperature, pH, or some other quality of the environment can cause the protein to unravel and lose it normal shape
This is called the denaturation of the protein

49. Nucleic acids are polymers of monomers called nucleotides.

50. Nucleic acids are polymers of monomers called nucleotides.
Nucleotides are made of a sugar, phosphate group, and a nitrogen base.
A phosphate group
nitrogen-containing molecule, called a base
deoxyribose (sugar)

51. Nucleic acids are polymers of monomers called nucleotides.
Nucleotides are made of a sugar, phosphate group, and a nitrogen base.
DNA stores genetic information.
DNA
RNA builds proteins.
RNA

52. KEY CONCEPT Life depends on chemical reactions.

53. Bonds break and form during chemical reactions.
Chemical reactions change substances into different ones by breaking and forming chemical bonds.
Reactants are changed during a chemical reaction. These are what you start with
Products are made by a chemical reaction. These are what you end with

54. Bond energy is the amount of energy that breaks a bond.
Energy is added to break bonds.
Energy is released when bonds form.
A reaction is at equilibrium when reactants and products form at the same rate.
CO2 + H2O H2CO3

55. Chemical reactions release or absorb energy.
Activation energy is the amount of energy that needs to be absorbed to start a chemical reaction.

56. Exothermic reactions release more energy than they absorb.
Reactants have higher bond energies than products.
Excess energy is released by the reaction.

57. Endothermic reactions absorb more energy than they release.
Reactants have lower bond energies than products.
Energy is absorbed by the reaction to make up the difference.

58. Dehydration Reactions
Dehydration reactions remove water to join compounds together

59. Hydrolysis Reaction
Hydrolysis reactions add water to break apart compounds (hydro – water lysis – cut)

60. Building and breaking polymers
Dehydration Reaction
Hydrolysis Reaction
Hydro-water
Lysis- to break

61. KEY CONCEPT Enzymes are catalysts for chemical reactions in living things.

62. A catalyst lowers activation energy.
Catalysts are substances that speed up chemical reactions.
decrease activation energy
increase reaction rate

63. Enzymes are catalysts in living things.
Enzymes allow chemical reactions to occur under tightly controlled conditions.
Enzymes are catalysts in living things.
Enzymes are needed for almost all processes.
Most enzymes are proteins.

64. Disruptions in homeostasis can prevent enzymes from functioning.
Enzymes function best in a small range of conditions.
Changes in temperature and pH can break hydrogen bonds.
An enzyme’s function depends on its structure.

65. An enzyme’s structure allows only certain reactants to bind to the enzyme.
substrates
active site
substrates (reactants)
enzyme
Substrates bind to an enzyme at certain places called active sites.

66. The lock-and-key model helps illustrate how enzymes function.
substrates brought together
bonds in substrates weakened
Substrates bind to an enzyme at certain places called active sites.
The enzyme brings substrates together and weakens their bonds.
The catalyzed reaction forms a product that is released from the enzyme.