Transcript Chemistry 112

Chemistry 112
Overview of
Chapters 5, 8, 16, & 9
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.
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.
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.
 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 joules
or calories.
Types of Energy
 Energy (cont)
 Energy and Temperature
 Materials at higher temperatures contain
more energy than the same amount of
material at a lower temperature.
Thermal Energy
 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.
Reactions Go Energetically
Downhill
 Energy Changes During Reactions
 Energy Diagrams
 Depict the relative energies of the reactants
and products, as well as the energy barrier to
reaction.
Energy Diagrams
 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.
Endothermic vs. Exothermic
 The Second Law of Thermodynamics
 No energy transformation can be absolutely
efficient.
 Entropy
 Time’s arrow, molecular disorder
 Examples of favorable entropy
 Solids or liquids are converted to gases
 More molecules of products than of reactants
 A solid dissolves
Dissolving Solids Increases
Entropy
 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.
 Kinetics (cont)
 Collision Theory
 Two chemical species must come together in
the right orientation with sufficient energy to
undergo reaction.
Collision Theory
 Kinetics (cont)
 Factors that Affect Reaction Rates
 Concentration of Reactants
 Temperature
 Catalysts
Effect of Temperature
Effect of Catalysts
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.
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.
 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.
Triglycerides
 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.
Phospholipids
 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.
 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).
Monosaccharides
 Carbohydrates (cont)
 Carbohydrate Polymers: Polysaccharides
 Examples include cellulose and starch.
 Carbohydrates for Recognition
 Examples include blood-type carbohydrates.
Blood-Group Carbohydrates
 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.
Polypeptide Folding
 Protein Principles
 Structure Determines Function
 Enzymes are Protein Catalysts
 Abnormal Protein Structures Can Lead to
Disease
 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.
DNA Structure
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.
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
 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
 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?)
 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.
 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.
Chromatography
Spectroscopy
 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.
Mass Spectrum of Dodecane
 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.
 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.
Microscopic View of Fibers

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.
RFLP Analysis
PCR-STR Analysis

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.
Nuclear vs. mitochondrial DNA
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.
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.
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.

Food Guide Pyramids

USDA’s Original Pyramid

MyPyramid



Grains form the base of the pyramid; fats, oils, and
sweets form the tip; fruit, vegetable, dairy, and protein
groups are in the middle.
Importance of exercise is stressed.
Healthy Eating Pyramid

Distinguishes between “good” and “bad” carbs and
fats.
 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.
Overview of Carbohydrates
 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

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.
Lipoprotein Complexes
 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.
Dietary Fatty Acids
 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 fats
the omega-6 and omega-3 fatty acids

Dieting

Energy Balance


Dieting Affects Energy Expenditure


Energy is expended through basal metabolism,
physical activity, and thermogenesis.
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.
 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
Phytochemicals
 Food Additives
 GRAS List
 preservatives, coloring agents, flavoring
agents, sweeteners, or nutrients
 Incidental Additives