Chemistry 112

1
Chemistry 112

• Overview of
• Chapters 5, 8, 16, 9

2
Chapter 5 Highlights

• Chemical reactions involve energy.
• There are two types of energy potential (stored)
  and kinetic (energy of motion).
• The first law of thermodynamics states that
  energy is conserved during chemical reactions,
  but it may be transformed from one type to
  another.

3
Chapter 5 Highlights(cont)

• Reactions can be exothermic (releasing heat) or
  endothermic (absorbing heat).
• Chemical reactions are spontaneous if the
  products are energetically downhill with respect
  to the reactants.
• The second law of thermodynamics states that
  increasing molecular disorder (entropy) is
  favored.

4
Chapter 5 Highlights(cont)

• The size of the energy barrier between reactants
  and products (the activation energy) dictates the
  rate of a chemical reaction (the kinetics).
• A catalyst lowers the activation energy, thereby
  speeding up the rate of a chemical reaction.
• Collision theory predicts that increasing
  concentration of reactants or temperature leads
  to increased reaction rates.

5

• Energy
• Measuring Energy
• The two general types of energy are
  potential(stored energy) and kinetic (energy of
  motion).
• Energy is most often measured in either joulesor
  calories.

6
Types of Energy
7

• Energy (cont)
• Energy and Temperature
• Materials at higher temperatures contain more
  energy than the same amount of material at a
  lower temperature.

8
Thermal Energy
9

• Energy (cont)
• Energy and Chemical Reactions
• In chemistry, having low energy means increased
  stability, which is favored.
• Atoms and molecules undergo reactions to decrease
  their overall energies.

10
Reactions Go Energetically Downhill
11

• Energy Changes During Reactions
• Energy Diagrams
• Depict the relative energies of the reactants and
  products, as well as the energy barrier to
  reaction.

12
Energy Diagrams
13

• The First Law of Thermodynamics
• Energy is conserved during chemical reactions.
• Heat of Reaction
• Heat transferred during a chemical reaction
• Endothermic vs. Exothermic
• In endothermic reactions, heat can be considered
  to be one of the reactants. Endothermic reactions
  often feel cold and are energetically uphill.
• In exothermic reactions, heat can be considered
  to be one of the products. Exothermic reactions
  often feel warm and are energetically downhill.

14
Endothermic vs. Exothermic
15

• The Second Law of Thermodynamics
• No energy transformation can be absolutely
  efficient.
• Entropy
• Times arrow, molecular disorder
• Examples of favorable entropy
• Solids or liquids are converted to gases
• More molecules of products than of reactants
• A solid dissolves

16
Dissolving Solids Increases Entropy
17

• Kinetics
• Activation Energy
• The size of the energy barrier on the pathway
  from reactants to products determines how fast a
  reaction proceeds.
• Slow reactions have relatively large energy
  barriers, while fast reactions have relatively
  small energy barriers.

18

• Kinetics (cont)
• Collision Theory
• Two chemical species must come together in the
  right orientation with sufficient energy to
  undergo reaction.

19
Collision Theory
20

• Kinetics (cont)
• Factors that Affect Reaction Rates
• Concentration of Reactants
• Temperature
• Catalysts

21
Effect of Temperature
22
Effect of Catalysts
23
Chapter 8 Highlights

• The classes of molecules that form the basis of
  all living organisms are lipids (fats),
  carbohydrates (sugars), proteins, and nucleic
  acids.
• Lipids are nonpolar compounds that serve as the
  scaffolding for cell membranes, function in
  energy storage, and play a role in signaling.

24
Chapter 8 Highlights(cont)

• Carbohydrates, composed of monosaccharide
  building blocks, function in energy storage and
  cellular recognition.
• Proteins, composed of amino acids, act as
  catalysts, as structural components in hair,
  muscle, and other tissue, and as antibodies in
  the immune response.
• Nucleic acids, composed of nucleotides, are the
  molecules of inheritance.

25

• Lipids
• Overview
• Lipids are hydrophobic molecules that act as
  energy stores, as the structural units of
  membranes, and as cellular signals.
• Energy-Storage Lipids Triglycerides
• Three fatty acids linked to glycerol
• The fatty acids can be saturated or unsaturated,
  depending on the source.

26
Triglycerides
27

• Lipids (cont)
• Membrane Lipids Phospholipids
• Amphiphilic molecules composed of glycerol linked
  to two fatty acids and a charged
  phosphorus-containing group
• Phospholipids form a membrane bilayer in water.

28
Phospholipids
29

• Lipids (cont)
• Rigid Lipids Steroids
• Steroids are based on cholesterol.
• Some steroids are hormones, which send messages
  between cells. Examples include the sex hormones
  estradiol and testosterone.

30

• Carbohydrates (Sugars)
• Overview
• Polar molecules with the general formula CxH2Oy
  that have roles in energy storage, structure, and
  cell recognition.
• Building Blocks Monosaccharides
• Examples include glucose (blood sugar) and
  fructose (fruit sugar).

31
Monosaccharides
32

• Carbohydrates (cont)
• Carbohydrate Polymers Polysaccharides
• Examples include cellulose and starch.
• Carbohydrates for Recognition
• Examples include blood-type carbohydrates.

33
Blood-Group Carbohydrates
34

• Proteins
• Amino Acids and Peptides
• Twenty different amino acid building blocks
  comprise proteins.
• Linking two or more amino acids leads to a
  peptide.
• Long peptide chains (polypeptides) fold up to
  form proteins.

35
Polypeptide Folding
36

• Protein Principles
• Structure Determines Function
• Enzymes are Protein Catalysts
• Abnormal Protein Structures Can Lead to Disease

37

• Nucleic Acids (DNA and RNA)
• Building Blocks Nucleotides
• Contain a phosphate group, a sugar ring, and a
  nitrogen-containing base (A, G, C, T/U).
• Structure
• DNA is a two-chained helix with the chains
  running in opposite directions.
• Strands interact through specific
  hydrogen-bonding interactions (A with T and G
  with C).
• Function
• Stretches of DNA called genes code for proteins.

38
DNA Structure
39
Chapter 16 Highlights

• Every contact leaves its trace.
• Physical evidence is any material related to a
  crime, including fingerprints, weapons, and
  bodily fluids.
• Crime scene investigators document and collect
  physical evidence for analysis at a crime
  laboratory.

40
Chapter 16 Highlights(cont)

• A variety of techniques are used to characterize
  physical evidence, including
• mass spectrometry, which provides a unique
  fingerprint of a compound
• spectroscopy, which uses interactions with
  electromagnetic radiation to characterize
  compounds
• microscopy, which reveals features of
  fingerprints, bullets, and fibers invisible to
  the naked eye
• DNA analysis, which can be used to uniquely
  identify the source of a biological sample even
  years later

41

• Evidence Collection
• Preserve and Protect
• First responders must isolate the crime scene so
  that physical evidence is not disturbed
• Physical Evidence
• Anything that can link a suspect to a crime

42

• Evidence Analysis
• Organization of the Crime Lab
• Specialized branches handle specific types of
  evidence e.g., latent prints
• What is it?
• Identification at the molecular level(e.g., is
  the white powder cocaine?)
• Comparison to a reference sample(e.g., is the
  blood from the suspect?)

43

• Evidence Analysis (cont)
• Qualitative vs. Quantitative Analysis
• Qualitative analysis determines the identity of a
  sample (what is it?).
• Quantitative analysis measures how much of a
  substance is present.

44

• Techniques for Evidence Analysis
• Separating and Identifying
• Chromatography separates the components of a
  mixture based on polarity.
• Spectroscopy identifies molecules based on
  differential interactions with electromagnetic
  radiation.

45
Chromatography
46
Spectroscopy
47

• Analysis of Evidence
• Arson
• Accelerants are used during arson to make fires
  burn faster.
• Accelerants are volatile compounds that easily
  enter the gas phase.
• Gas chromatography coupled with mass spectrometry
  (GC-MS) is used to separate and identify the
  components of a suspected accelerant.

48
Mass Spectrum of Dodecane
49

• Analysis of Evidence (cont)
• Drugs
• Forensic toxicologists identify alcohol, drugs,
  and poisons in biological samples.
• Liquid chromatography coupled with mass
  spectrometry (LC-MS) is commonly used to analyze
  liquid mixtures such as blood.

50

• Analysis of Evidence (cont)
• Microscopic Analysis
• Tiny features of a sample invisible to the naked
  eye can be detected with a microscope.
• Types of evidence examined by microscopy include
  fingerprints, bullets and shell casings, and
  fibers.

51
Microscopic View of Fibers
52

• DNA Analysis
• Nuclear DNA Analysis
• Unique among individuals (except identical
  twins).
• Detects differences between individuals at highly
  variable, noncoding regions.
• In restriction fragment length polymorphism
  (RFLP) analysis, DNA is cut to yield fragments
  that vary in length between individuals.
• In PCR-STR analysis, DNA is amplified via the
  polymerase chain reaction to yield products that
  vary in length between individuals.

53
RFLP Analysis
54
PCR-STR Analysis
55

• DNA Analysis (cont)
• Mitochondrial DNA Analysis
• Identical among those related on a maternal line.
• Present in multiple copies per cell.
• Most useful for badly damaged remains.
• Hypervariable DNA region is amplified via the
  polymerase chain reaction and then sequenced.

56
Nuclear vs. mitochondrial DNA
57
Chapter 9 Highlights

• The macronutrients are carbohydrates (sugars and
  starches), lipids (fats and oils), and proteins.
• The micronutrients are vitamins, minerals, and
  phytochemicals.
• Dietary carbohydrates are broken down to glucose
  or its derivatives and oxidized for energy.

58
Chapter 9 Highlights (cont)

• Good carbohydrates, such as the complex
  carbohydrates, tend to raise blood sugar slowly.
• Proteins are broken down into their component
  amino acids, which are generally used to assemble
  new proteins rather than being oxidized.
• Lipids are oxidized for energy.
• Good lipids are polyunsaturated fats such as
  omega-3 and omega-6 fatty acids.

59
Chapter 9 Highlights(cont)

• Bad lipids are cholesterol, saturated fats, and
  trans fats.
• Dieting alone is not effective for weight control
  because the body responds by decreasing the
  amount of energy expended to maintain essential
  life processes.
• Vitamins are essential carbon-based compounds
  used as chemical reactants.
• Minerals are essential inorganic elements.
• Phytochemicals are disease-fighting molecules
  found in plant products.
• Processed food contains food additives.

60

• Food Guide Pyramids
• USDAs Original Pyramid
• Grains form the base of the pyramid fats, oils,
  and sweets form the tip fruit, vegetable, dairy,
  and protein groups are in the middle.
• MyPyramid
• Importance of exercise is stressed.
• Healthy Eating Pyramid
• Distinguishes between good and bad carbs and
  fats.

61

• Dietary Carbohydrates
• Simple Sugars (Monosaccharides)
• Complex Carbohydrates (Polysaccharides)
• Glycemic Index
• A measure of how fast dietary carbohydrates are
  broken down to raise blood sugar
• Diets rich in foods with high GI values have been
  linked to increased risk of certain chronic
  diseases such as diabetes.

62
Overview of Carbohydrates
63

• Dietary Proteins
• Essential Amino Acids
• Adult humans cannot make 9 of the 20 amino acids
  and must obtain these in the diet on a regular
  basis.
• Complete Proteins
• Provide all the essential amino acids
• Role of Dietary Proteins
• Provide the amino acids needed to make new
  proteins

64

• Dietary Lipids
• Cholesterol
• Cholesterol is carried through the bloodstream in
  lipoprotein complexes.
• LDL is the bad form of cholesterol, while HDL
  is the good form.
• Diets rich in saturated fats and cholesterol are
  linked to increased risk of heart disease.
• Although the French have diets rich in animal
  fats, they have a lower incidence of heart
  disease. This French paradox is attributed to
  protective compounds in red wine.

65
Lipoprotein Complexes
66

• Dietary Lipids (cont)
• Triglycerides
• Dietary triglycerides from animal sources tend to
  contain saturated fatty acids and are generally
  solids at room temperature
• Dietary triglycerides from plant sources tend to
  contain unsaturated fatty acids and are generally
  liquids at room temperature.

67
Dietary Fatty Acids
68

• Dietary Lipids (cont)
• The Bad Fats
• Saturated fats linked to increased risk of heart
  disease
• Trans fats made during hydrogenation of
  unsaturated fats
• The Good Fats
• Polyunsaturated fats such as the essential
  fatsthe omega-6 and omega-3 fatty acids

69

• Dieting
• Energy Balance
• Energy is expended through basal metabolism,
  physical activity, and thermogenesis.
• Dieting Affects Energy Expenditure
• The body adapts to less food by reducing its
  energy expenditure. The hormone leptin also tells
  the brain to stop eating.
• Low Fats vs. Low Carbs
• Diets low in carbohydrates lead to production of
  ketone bodies from fat stores, which can lead to
  a dangerous drop in blood pH and stress on the
  liver and kidneys.

70

• Micronutrients
• Vitamins
• Fat soluble (A, D, E, K)
• Water soluble (C and B family)
• Minerals
• Macrominerals (e.g., calcium)
• Trace minerals (e.g., iron)
• Phytochemicals
• Disease-preventing molecules found in plant
  products

71
Phytochemicals
72

• Food Additives
• GRAS List
• preservatives, coloring agents, flavoring agents,
  sweeteners, or nutrients
• Incidental Additives