1. Chapter 2
Chemistry of Life

2. Living things consist of atoms of different elements.
An atom is the smallest basic unit of matter.
An element is one type of atom.
Hydrogen atom (H) H O
Oxygen atom (O)

3. An atom has a nucleus and electrons.
The nucleus has protons and neutrons.
Electrons are in energy levels outside nucleus.
Oxygen atom (O)
Nucleus: 8 protons (+) 8 neutrons
outermost energy level: 6 electrons (-)
inner energy level: 2 electrons (-)

4. O A compound is made of atoms of different elements bonded together.
water (H2O) O H _ +

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

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

7. Ions form when atoms gain or lose electrons.
An ion is an atom that has gained or lost one or more electrons.
positive ions
negative ions
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

8. 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 )

9. 2.2 Properties of Water

10. Water Needed by all know forms of life
~75% of Earth’s surface is covered with water
Water refers to liquid form. (Solid and gas forms also seen)
Total Water on Earth

11. Structure and Properties of Water
What are some you can think of?
Tasteless & odorless
Transparent…Why is that important?
Some marine organisms need sunlight to make food

12. Chemical Structure of Water
One atom of O, two Atoms of H
O attracts negatively charged e- more than the H
Therefore O has a slightly – charge and the H has a slightly + charge
This makes it a polar molecule because it has a different electrical charge between different parts of the same molecule

13. This diagram shows the + and – parts of a water molecule
This diagram shows the + and – parts of a water molecule. It also shows how a charge such as an ion (Na or Cl) can interact with a water molecule

14. This forms a Hydrogen bond (weak)
Opposites attract
H+ end of one water molecule is attracted to the O- end of a nearby molecule
This forms a Hydrogen bond (weak)
Bonds between molecules are not as strong as inside molecules
They are strong enough to hold together nearby molecules
Cohesion - between two water molecules
Adhesion – attraction between two different molecules

15. Hydrogen bonds form between nearby water molecules

16. Properties of Water Water sticks together (cohesion) examples?

17. H bonds cause a higher boiling point (100 C, 212 F)
Higher boiling point causes most water on Earth to be in liquid state, not gas state
All living things on Earth need water
H bonds cause water to expand when frozen
Causes ice to have lower density than liquid water (ice floats)

18. Water and Life Human= ~70% water not counting fat (varies)
Why so much Water?
Substances the body needs are dissolved in water
Biochemical reactions occur in water
2 Important biochemical reactions:
1. photosynthesis: 6CO2 + 6H2O + Energy → C6H12O6 + 6O2
2. cellular respiration: C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy.
Just about all life processes involve water

19. Water in Biochemical Reactions

20. 2.3 Carbon-Based Molecules

21. Carbon is the most important element to life
Carbon is the most important element to life. Without this element, life as we know it would not exist. Carbon is the central element in compounds necessary for life.

22. The significance of Carbon
A compound in living things is an Organic Compound
Organic compounds make up cells/other structures and carry out life processes
Carbon is the main element in organic compounds (important)

23. Compounds
Compound: substance that consists of two or more elements (always the same)
The smallest part of a compound is a molecule
A molecule of water always contains 2 H atoms and 1 O atom
Water is not an organic compound

24. Chemical bond: force that holds molecules together (H bonds in water)
Chemical reaction: process that changes some chemical substances into others
Chemical reactions are needed to form compounds (also needed to break them apart)

25. Carbon Why is carbon needed for life?
It forms stable bonds with many elements including C
C forms a variety of complex and simple molecules (10 million C based compounds)
The millions can be grouped into 4 main types (macromolecules)
1. carbohydrates
2. lipids
3. proteins
4. nucleic acids

26. Built by dehydration (condensation) reactions
Carbohydrates, proteins and nucleic acids are large Polymers (large molecules) made up of smaller monomers (small molecules)
Built by dehydration (condensation) reactions
Dehydration reaction: Water is built as two monomers come together.

29. Carbohydrates
Carbohydrate: organic compound such as sugar or starch and is used to store E
Built of small monomers called monosaccharides
Contain only Carbon, Hydrogen and Oxygen

30. Monosaccharides and Disaccharides
Monosaccharide: simple sugar such as fructose (in fruit) or glucose (digestion of other carbs)
Glucose (C6H12O6): is used for E in almost all cells and is a main product of photosynthesis
Monosaccharide formula = (CH2O)n n is any number greater than 2
In glucose what does n equal?

31. If two monosaccharides come together they form a disaccharide
Sucrose is an example, contain glucose and fructose
Monosaccharides and disaccharides are called simple sugars
Major source of E in cells

32. Sucrose Molecule. This sucrose molecule is a disaccharide
Sucrose Molecule. This sucrose molecule is a disaccharide. It is made up of two monosaccharides: glucose on the left and fructose on the right.

33. Polysaccharides
Complex carbohydrate that forms when simples sugars come together and make a chain
Two main functions:
1. storing E
2. forming structures
What type of polysaccharides to our bodies use to store E?
Glycogen

34. Examples of complex carbohydrates and their functions
Name
Function
Example
Starch
Used by plants to store energy.
A potato stores starch in underground tubers.
Glycogen
Used by animals to store energy.
A human stores glycogen in liver cells.
Cellulose
Used by plants to form rigid walls around cells.
Plants use cellulose for their cell walls.
Chitin
Used by some animals to form an external skeleton.
A housefly uses chitin for its exoskeleton.

35. Lipids An organic compound like fat or oil
Used by organisms to store E
Lipids are made of repeating units called fatty acids
Two types of fatty acids:
1. saturated
2. unsaturated

36. Saturated Fatty Acids
Carbon atoms are bonded to as many hydrogen atoms as possible in saturated fatty acids
Molecules have straight chains
The straight chains can be packed together very tightly, allowing them to store energy in a compact form
Solid at room temperature.
Animals use them to store energy.

37. Saturated fatty acids have straight chains, like the three fatty acids shown in the upper left. Unsaturated fatty acids have bent chains, like all the other fatty acids in the figure.

38. Unsaturated Fatty Acids
Some carbon atoms are not bonded to as many hydrogen atoms
When carbon binds with other groups of atoms, it causes chains to bend
Not packed together as tightly
Liquids at room temperature
Plants use unsaturated fatty acids to store energy

39. Wherever carbon binds with these other groups of atoms, it causes chains to bend 

40. These plant products all contain unsaturated fatty acids.

41. Types of Lipids
Triglycerides: the main form of stored energy in animals.
Phospholipids: the major components of cell membranes.
Steroids: serve as chemical messengers and have other roles.

42. The left part of this triglyceride molecule represents glycerol
The left part of this triglyceride molecule represents glycerol. Each of the three long chains on the right represents a different fatty acid. From top to bottom, the fatty acids are palmitic acid, oleic acid, and alpha-linolenic acid. The chemical formula for this triglyceride is C55H98O6. KEY:H=hydrogen, C=carbon, O=oxygen

43. Lipids and Diet
Humans need lipids for storing E and forming cell membranes.
Lipids also supply cells with E.
Essential fatty acids must be consumed in food
These include omega-3 and omega-6 fatty acids.
Both of these are needed for important biological processes, not just E.

44. Excess dietary lipids can be harmful
Eating too many may cause weight gain.
A high-fat diet may also increase lipid levels in the blood.
Can increase the risk for cardiovascular disease.
Saturated fatty acids, trans fats, and cholesterol are to most common
Cholesterol is mainly responsible for narrowing arteries and causing the disease atherosclerosis

45. Proteins Organic molecule made up of monomers called amino acids
20 different amino acids found in living things
Proteins could contain just a few hundred to thousands of AA

46. This model shows the general structure of all amino acids
This model shows the general structure of all amino acids. Only the side chain, R, varies from one amino acid to another. For example, in the amino acid glycine, the side chain is simply hydrogen (H). In glutamic acid, in contrast, the side chain is CH2CH2COOH. Variable side chains give amino acids different chemical properties. The order of amino acids, together with the properties of the amino acids, determines the shape of the protein, and the shape of the protein determines the function of the protein. KEY: H = hydrogen, N = nitrogen, C = carbon, O = oxygen, R = variable side chain

47. Protein Structure
Amino acids bind together and form a chain called a polypeptide
Proteins consist of one or more polypeptide chains
A protein may have up to four levels of structure.
A protein’s primary structure is its sequence of amino acids.
The complex structures of different proteins give them unique properties, which they need to carry out their various jobs in living organisms.
Protein structure animation

48. The structure of a protein starts with its sequence of amino acids
The structure of a protein starts with its sequence of amino acids. What determines the secondary structure of a protein? What are two types of secondary protein structure?

49. Functions of proteins
Help cells keep their shape (structural proteins)
Make up muscle tissues
Transport items in and out of cells (transport proteins)
Act as signals and receive signals
Enzymes are proteins that speed up chemical reactions in cells
Others are antibodies which bind to foreign substances such as bacteria and target them for destruction.
Carry messages or transport materials (ex. Hemoglobin)
Protein Functions in the body video

50. This model represents the protein hemoglobin
This model represents the protein hemoglobin. The purple part of the molecule contains iron. The iron binds with oxygen molecules.

51. Proteins and Diet
Proteins are broken down into amino acids when food is digested
Cells use the AA to build new proteins
Essential amino acids must be consumed in foods
Dietary proteins can be broken down to provide cells with energy.

52. Nucleic Acids
Organic compound such as DNA or RNA that is built of monomers called nucleotides
The nucleic acid DNA (deoxyribonucleic acid) consists of two chains.
The nucleic acid RNA (ribonucleic acid) consists of just one chain.

53. Structure of Nucleic Acids
Each nucleotide consists of three molecules:
1.sugar
2.phosphate group
3.nitrogen base
The sugar of one nucleotide binds to the phosphate group of the next nucleotide.
This is known as the sugar-phosphate backbone.

54.  Sugars and phosphate groups form the backbone of a polynucleotide chain. Hydrogen bonds between complementary bases hold two polynucleotide chains together.

55. Roles of Nucleic Acids
DNA contains the genetic instructions for the correct sequence of amino acids in proteins
RNA uses the information in DNA to assemble the correct amino acids and help make the protein.
DNA is passed from parents to offspring when organisms reproduce.
This is how inherited characteristics are passed from one generation to the next.

56. The letters G, U, C, and A stand for the bases in RNA
The letters G, U, C, and A stand for the bases in RNA. Each group of three bases makes up a code word, and each code word represents one amino acid (represented here by a single letter, such as V, H, or L). A string of code words specifies the sequence of amino acids in a protein.

57. 2.4 Chemical Reactions

58. 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.
Products are made by a chemical reaction.

59. 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

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

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

62. 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.

63. Enzymes

64. Enzymes and Biochemical Reactions
Most chemical reactions within organisms would be impossible under the conditions in cells (ex. Temp to low)
The rate of reactions must be increased by a catalyst
Catalyst: a chemical that speeds up chemical reactions called enzymes (biological catalysts)

65. Enzymes are not reactants
They help the reactants but are not used up in the reactions
They may be used many times
Enzymes are highly specific for particular chemical reactions
Catalyze only one or a few types of reactions.

66. Efficient in speeding up reactions
Can catalyze up to several million reactions per second
A typical biochemical reaction might take hours or even days to occur under normal cellular conditions without an enzyme but less than a second with an enzyme
Enzymes video

67. Importance of Enzymes
Enzymes are involved in most of the biochemical reactions
Enzymes allow reactions to occur at the rate necessary for life.
In animals, an important function of enzymes is to help digest food.
Digestive enzymes speed up reactions that break down large molecules of carbohydrates, proteins, and fats into smaller molecules the body can use.
Without digestive enzymes, animals would not be able to break down food molecules quickly enough to provide the energy and nutrients they need to survive.

68. Enzyme Function
Enzymes lower the activation energy of chemical reactions.
Activation energy: the energy needed to start a chemical reaction.
Enzyme animation

69. The reaction represented by this graph is a combustion reaction involving the reactants glucose (C6H12O6) and oxygen (O2). The products of the reaction are carbon dioxide (CO2) and water (H2O). Energy is also released during the reaction. The enzyme speeds up the reaction by lowering the activation energy needed for the reaction to start. Compare the activation energy with and without the enzyme.

70. Enzymes bring reactants together, don’t have to expend energy moving until they collide at random.
Enzymes bind reactant molecules (called the substrate), tightly and specifically, at a site on the enzyme molecule called the active site 
Active site is specific for the reactants of the biochemical reaction the enzyme catalyzes. (puzzle pieces)
Enzymes also position reactants correctly which allows the molecules to interact with less energy.
Enzymes also allow reactions to occur by different pathways that have lower activation energy.

71. This enzyme molecule binds reactant molecules—called substrate—at its active site, forming an enzyme-substrate complex. This brings the reactants together and positions them correctly so the reaction can occur. After the reaction, the products are released from the enzyme’s active site. This frees up the enzyme so it can catalyze additional reactions.

72. The activities of enzymes also depend on the temperature, ionic conditions, and the pH of the surroundings.
Many enzymes lose function at lower and higher temperatures.
At higher temperatures, an enzyme’s shape deteriorates.
Only when the temperature comes back to normal does the enzyme regain its shape and normal activity.