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1
Chapter 2:
The Chemical Level of Organization
2
Introduction to Chemistry
• Matter is made up of atoms• Atoms join together to form
chemicals with different characteristics
• Chemical characteristics determine physiology at the molecular and cellular level
3
Atomic Particles
• Proton: – positive, 1 mass unit
• Neutron: – neutral, 1 mass unit
• Electron: – negative, low mass
4
Particles and Mass
• Atomic number: – number of protons
• Mass number: – number of protons plus neutrons
• Atomic weight: – exact mass of all particles (daltons)
5
Isotopes
• 2 or more elements with equal numbers of protons but different numbers of neutrons
Electron shell
p+ p+
p+n
n
n
e e e
(a) Hydrogen-1(electron-shell model)
(b) Hydrogen-2 deuterium
(c) Hydrogen-3, tritium
6
Elements in the Human Body
Table 2–1
7
How do atoms form molecules and compounds?
8
Molecules and Compounds
• Molecules: – atoms joined by strong bonds
• Compounds: – atoms joined by strong or weak bonds
9
Chemical Bonds
• Ionic bonds: – attraction between cations (+) and anions
(-)• Covalent bonds:
– strong electron bonds– Non polar covalent bonds: equal sharing of
electrons– Polar covalent bonds: unequal sharing of
electrons• Hydrogen bonds:
– weak polar bonds
10
Ionic Bonds
Figure 2–3a
Are atoms with positive or negative charge
11
Covalent Bond
• Formed between atoms that share electrons
Hydrogen(H2)
Oxygen(O2)
CarbonDioxide
(CO2)
NitricOxide(NO)
MoleculeElectron-Shell Model and
Structural Formula
H–H
O=O
N=O
O=C=O
Free Radicals:Ion or molecule that contain unpaired electrons in the outermost shell. - Extremely Reactive -Typically enter into destructive reactions -Damage/destroy vital compounds
12
Hydrogen Bonds
• Attractive force between polar covalent molecules
• Weak force that holds molecules together
• Hydrogen bonds between H2O molecules cause surface tension
Figure 2–6
13
How is it possible for two samples of hydrogen to contain the same
number of atoms, yet have different weights?
A. One sample has more bonds.
B. One sample contains fewer electrons, decreasing weight.
C. One sample contains more of hydrogen’s heavier isotope(s).
D. One sample includes more protons, increasing weight.
14
Both oxygen and neon are gases at room temperature. Oxygen combines readily with other elements, but neon does
not. Why?
A. Neon has 8 electrons in its valence shell, oxygen has only 6.
B. Neon cannot undergo bonding due to its polarity.
C. Neon is exergonic.D. Neon’s molecular
weight is too low to allow bonding.
15
Both oxygen and neon are gases at room temperature. Oxygen combines readily with other elements, but neon does
not. Why?
A. Neon has 8 electrons in its valence shell, oxygen has only 6.
B. Neon cannot undergo bonding due to its polarity.
C. Neon is exergonic.D. Neon’s molecular
weight is too low to allow bonding.
16
Which kind of bond holds atoms in a water molecule together?
What attracts water molecules to one another?
A. polar covalent bonds; hydrogen bonds
B. ionic bonds; charge interactions
C. hydrogen bonds; charge interactions
D. covalent bonds; hydrogen bonds
17
Why are chemical reactions important to
physiology?
18
Energy
• Energy: – the capacity to do work
• Work: – a change in mass or distance
19
Forms of Energy
• Kinetic energy: – energy of motion
• Potential energy: – stored energy
• Chemical energy: – potential energy stored in chemical bonds
When energy is exchanged, heat is produced - cells cannot capture it or use it for work
20
Break Down, Build Up
• Decomposition reaction (catabolism): AB A + B• Synthesis reaction (anabolism): A + B AB• Exchange reaction (reversible): AB + CD AD + CBIf Water is Involved:• Hydrolysis:
A—B—C—D—E + H2O A—B—C—H + HO—D—E
• Dehydration synthesis (condensation):A—B—C—H + HO—D—E A—B—C—D—E
+ H2O
21
KEY CONCEPT
• Reversible reactions seek equilibrium, balancing opposing reaction rates
• Add or remove reactants:– reaction rates adjust to reach a new
equilibrium
22
How do enzymes control metabolism?
23Figure 2–7
Activation Energy
• Chemical reactions in cells cannot start without help
• Activation energy gets a reaction started
24
Materials in Reactions
• Reactants: – materials going into a reaction
• Products: – materials coming out of a reaction
• Enzymes: – proteins that lower the activation
energy of a reaction
25
Energy In, Energy Out
• Exergonic reactions: – produce more energy than they use– Heat will be the by-product
• Endergonic reactions: – use more energy than they produce
• Most chemical reactions that sustain life cannot occur unless the right enzymes are present
26
In cells, glucose, a six-carbon molecule, is converted into two three-carbon molecules by a reaction that
releases energy. How would you classify this reaction?
A. endergonicB. exergonicC. decompositionD. B and C
27
In cells, glucose, a six-carbon molecule, is converted into two three-carbon molecules by a reaction that
releases energy. How would you classify this reaction?
A. endergonicB. exergonicC. decompositionD. B and C
28
Why are enzymes needed in our cells?
A. to promote chemical reactionsB. for chemical reactions to proceed under conditions compatible with lifeC. to lower activation energy requirementsD. all of the above
29
What is the difference between organic and inorganic compounds?
30
Organic and Inorganic Molecules
• Organic: – molecules based on carbon and
hydrogen
• Inorganic: – molecules not based on carbon and
hydrogen
31
Essential Molecules
• Nutrients: – essential molecules obtained from
food
• Metabolites: – molecules made or broken down in
the body
32
Why is water so important to life?
33
Properties of Water• Solubility:
– water’s ability to dissolve a solute in a solvent to make a solution
• Reactivity: – most body chemistry uses or occurs in water
• High heat capacity: – water’s ability to absorb and retain heat
• Lubrication: – to moisten and reduce friction
Water is the key structural and functional component of cells and their control mechanisms, the nucleic acids
34
Aqueous Solutions
Figure 2–8
Polar water molecules form hydrationspheres around ions and small polar molecules to keep them in solution
35
Electrolytes
• Inorganic ions: conduct electricity in solution
• Electrolyte imbalance seriously disturbs vital body functions
36
Molecules and Water
• Hydrophilic: – hydro = water, philos = loving– reacts with water
• Hydrophobic:– phobos = fear– does not react with water
37
Solutions
• Suspension: – a solution in which particles settle
(sediment)
• Concentration: – the amount of solute in a solvent
(mol/L, mg/mL)
38
What is pH and why do we need buffers?
39
pH: Neutral, Acid, or Base?
• pH: – the concentration of hydrogen ions (H+) in a
solution• Neutral pH:
– a balance of H+ and OH— – pure water = 7.0
• Acid (acidic): pH lower than 7.0 – high H+ concentration,
low OH— concentration• Base (basic): pH higher than 7.0
– low H+ concentration, high OH— concentration
40
pH Scale
Figure 2–9
• Has an inverse relationship with H+ concentration: – more H+ ions mean lower pH, less H+
ions mean higher pH
41
KEY CONCEPT
• pH of body fluids measures free H+ ions in solution
• Excess H+ ions (low pH): Acidosis– damages cells and tissues– alters proteins– interferes with normal physiological functions
• Excess OH— ions (high pH): Alkalosis – Uncontrollable and sustained skeletal muscle
contractions
42
Controlling pH
• Salts: – positive or negative ions in solution– contain no H+ or OH— (NaCl)
• Buffers: – weak acid/salt compounds– neutralizes either strong acid or
strong base
43
Why does a solution of table salt conduct electricity, but a sugar
solution does not?
A. Electrical conductivity requires ions.
B. Sugar forms a colloid, salt forms a suspension.
C. Electricity is absorbed by glucose molecules.
D. Table salt is hydrophobic, sugar is hydrophilic.
44
How does an antacid help decrease stomach discomfort?
A. by reducing buffering capacity of the stomach
B. by decreasing pH of stomach contents
C. by reacting a weak acid with a stronger one
D. by neutralizing acid using a weak base
45
What kinds of organic compounds are there, and how do they work?
Organic Compounds
46
Functional Groups of Organic Compounds
Table 2–4
• Molecular groups which allow molecules to interact with other molecules
47
Carbohydrates
• Consist of C:H:O in 1:2:1 ratio1. Monosaccharides:
– simple sugars with 3 to 7 carbon atoms (glucose)• Glucose: important metabolic fuel
2. Disaccharides: – 2 simple sugars condensed by
dehydration synthesis (sucrose)
48
Simple Sugars
Figure 2–10
Structural Formula:• Straight-chain form• Ring from• 3-D
Isomers: Glucose vs. Fructose: - Same chemical formula but different shape
49
Polysaccharides
• Chains of many simple sugars (glycogen)
• Formation:– Dehydration
synthesis
• Breakdown:– Hydrolysis synthesis
Figure 2–12Glycogen: made and stored in muscle cells
50
Carbohydrate Functions
Table 2–5
PolysaccharidesGlycogen: made and stored in muscle cellsCellulose: structural component of plants -Ruminant Animals: Cattle, sheep, and deerCattle, sheep, and deer
51
The Ruminant StomachRuminant stomach is polygastric: four compartments
-Rumen -Reticulum
-Abomasum -Omasum
52
RumenOccupies 80% of the stomach
Muscular PillarContract to mix feed
Digest starch and fibersMicrobes produce VFA’s
Lined with Papillae
pH of 5.8-7.0Provide a suitable environment for bacteria and protozoa
53
KEY CONCEPT
• Carbohydrates are quick energy sources and components of membranes
• Lipids have many functions, including membrane structure and energy storage– Provides 2x more energy then
carbohydrates
54
Lipids
• Mainly hydrophobic molecules such as fats, oils, and waxes
• Made mostly of carbon and hydrogen atoms (1:2), and some oxygen– Less oxygen then carbon
55
Classes of Lipids
• Fatty acids• Eicosanoids• Glycerides• Steroids• Phospholipids and glycolipids
56
Fatty Acids
• Carboxyl group -COOH– Hydrophilic
• Hydrocarbon tail:– Hydrophobic– Longer tail = lower solubility
• Saturated vs. Unsaturated– Saturated: solid at room temp.
• Cause solid plaques in arteries
– Unsaturated: liquid at room temp.
• Healthier
Figure 2–13
57
Eicosanoids
• Used for cellular communication • Never burned for energy1. Leukotrienes:
– active in immune system– Used by cells to signal injury
2. Prostaglandins: local hormones– Used for cell-to-cell signaling to
coordinate events
58Figure 2–16
Steroids
• 4 carbon ring with attached carbon chains
• Not burned for energy
59
Types of Steroids
• Cholesterol: – cell membrane formation and maintenance,
cell division, and osmotic stability
• Estrogens and testosterone: – Regulation of sexual function
• Corticosteroids and calcitrol: – Tissue metabolism and mineral balance
• Bile salts: – Processing of dietary fats
60Figure 2–15
Glycerides
• Glycerides: are the fatty acids attached to a glycerol molecule
• Triglyceride: are the 3 fatty-acid tails, fat storage molecule
Fat Deposits are Important1. Energy Storage2. Insulation3. Mechanical Protection
-Knees and Eye Sockets
61
Phospholipids Vs. GlycolipidsCombination Lipids
Figure 2–17a, b
Diglyceride
Cell Membranes are Composed of these lipids
Hydrophilic
Hydrophobic
62
Phospholipids Vs. GlycolipidsCombination Lipids
Figure 2–17c
Spontaneous formation of Micelle
63
5 Lipid Types
Table 2–6
64
A food contains organic molecules with the elements C, H, and O in a
ratio of 1:2:1. What class of compounds do these molecules
belong to, and what are their major functions in the body?
A. lipids; energy sourceB. proteins; support and
movementC. nucleic acids; determining
inherited characteristicsD. carbohydrates; energy
source
65
When two monosaccharides undergo a dehydration synthesis
reaction, which type of molecule is formed?
A. polypeptideB. disaccharideC. eichosanoidD. polysaccharide
66
Which kind of lipid would be found in a sample of fatty
tissue taken from beneath the skin?
A. eichosanoidB. steroidC. triglycerideD. phospholipid
67
Which lipids would you find in human cell membranes?
A. cholesterolB. glycolipidsC. phospholipidsD. all of the above
68
Protein Structure
• Proteins are the most abundant and important organic molecules
• Basic elements: – carbon (C), hydrogen (H), oxygen (O),
and nitrogen (N) • Basic building blocks:
– 20 amino acids
69
Protein Functions
• 7 major protein functions:– support: structural proteins– movement: contractile proteins– transport: transport proteins– buffering: regulation of pH– metabolic regulation: enzymes– coordination and control: hormones– defense: antibodies
70
Proteins
• Proteins: – control anatomical structure and
physiological function– determine cell shape and tissue
properties– perform almost all cell functions
71
Amino Acid Structure
1. central carbon2. hydrogen3. amino group (—
NH2)
4. carboxylic acid group (—COOH)
5. variable side chain or R group
Figure 2-18
72
Peptide Bond
• A dehydration synthesis between:– amino group of 1 amino acid– and the carboxylic
acid group of another amino acid
– producing a peptide
73Figure 2–20a
Primary Structure
• Polypeptide:– Linear sequence of amino acids
• How many amino acids were bound together
• What order they are bound
74
Secondary Structure
Figure 2–20b
• Hydrogen bonds form spirals or pleats
75Figure 2–20c
Tertiary Structure
• Secondary structure folds into a unique shape
• Global coiling or folding due to R group interaction
76
Quaternary Structure
Figure 2–20d
• Final protein shape: – several tertiary structures together
Fibrous proteins: - structural sheets
Globular proteins: - soluble spheres with active functions
77
Shape and Function
• Protein function is based on shape• Shape is based on sequence of
amino acids• Denaturation:
– loss of shape and function due to heat or pH
78
Enzymes
• Enzymes are catalysts: – proteins that lower the activation
energy of a chemical reaction – are not changed or used up in the
reaction
79
How Enzymes Work
Figure 2–21
Substrates: reactants in enzymatic reactionsActive site: location on an enzyme that fits a particular substrate
80
Enzyme Helpers
• Cofactor: – an ion or molecule that binds to an
enzyme before substrates can bind• Coenzyme:
– nonprotein organic cofactors (vitamins)
• Isozymes: – 2 enzymes that can catalyze the
same reaction
81
Enzyme Characteristics
• Specificity: – one enzyme catalyzes one reaction
• Saturation limits: – an enzyme’s maximum work rate
• Regulation: – the ability to turn off and on
82
Conjugated Protein
• Glycoproteins: – large protein + small carbohydrate
• includes enzymes, antibodies, hormones, and mucus production
• Proteoglycans: – large polysaccharides + polypeptides
• promote viscosity
83
Proteins are chains of which small organic molecules?
A. saccharidesB. fatty acidsC. amino acidsD. nucleic acids
84
Which level of protein structure would be affected by an agent that breaks hydrogen bonds?
A. the primary level of protein structure
B. the secondary level of protein structure
C. the tertiary level of protein structure
D. the protein structure would NOT be affected by this agent
85
Why does boiling a protein affect its structural and functional
properties?
A. Heat denatures the protein, causing unfolding.
B. Heat causes the formation of additional quaternary structure.
C. Heating rearranges the primary structure of the protein.
D. Heat alters the radical groups on the amino acids.
86
Why does boiling a protein affect its structural and functional
properties?
A. Heat denatures the protein, causing unfolding.
B. Heat causes the formation of additional quaternary structure.
C. Heating rearranges the primary structure of the protein.
D. Heat alters the radical groups on the amino acids.
87
How might a change in an enzyme’s active site affect its
functions?
A. increased activity due to a better fit with the substrate
B. decreased activity due to a poor substrate fit
C. inhibited activity due to no substrate fit
D. all of the above
88
Nucleic Acids
• C, H, O, N, and P• Large organic molecules, found in the
nucleus, which store and process information at the molecular level
• DNA – deoxyribonucleic acid• RNA – ribonucleic acid
89
DNA and RNA
DNA• Determines inherited characteristics• Directs protein synthesis• Controls enzyme production• Controls metabolismRNA• Codes intermediate steps in protein
synthesis
90
KEY CONCEPT
• DNA in the cell nucleus contains the information needed to construct all of the proteins in the body
91
Nucleotides
• Are the building blocks of DNA• Have 3 molecular parts:
– sugar (deoxyribose)– phosphate group– nitrogenous base (A, G, T, C)
92
The Bases
Figure 2–22b, c
93
Complementary Bases• Purines pair with pyrimidines:
• DNA: – adenine (A) and thymine (T) – cytosine (C) and guanine (G)
• RNA: – uracil (U) replaces thymine (T)
94
RNA and DNA
• RNA: – a single strand
• DNA: – a double helix joined at bases by
hydrogen bonds
95
Protein Synthesis:Three forms of RNA
• messenger RNA (mRNA)– Protein blueprint or instructions
• transfer RNA (tRNA)– Carry amino acids to the place where
proteins are being synthesized
• ribosomal RNA (rRNA)– Forms the site of protein synthesis in the
cell• Factory = ribosomes
96
High-Energy Compounds:ADP and ATP
- Assembled using RNA Nucleotides- Bonds are broken easily by cells to
release energy as needed- During digestion and cellular
respiration: - energy from food is transferred to high
energy compounds for quick and easy access.
97
ADP to ATP:Phosphorylation
ADP vs. ATP:• adenosine diphosphate (ADP):
– 2 phosphate groups (di = 2)• adenosine triphosphate (ATP):
– 3 phosphate groups (tri = 3)Adding a phosphate group to ADP with a
high-energy bound to form the high-energy compound ATP
• ATPase: – the enzyme that catalyzes phophorylation
98Figure 2–24
The Energy Molecule
• Chemical energy stored in phosphate bonds
99
A large organic molecule composed of the sugar ribose,
nitrogenous bases, and phosphate groups is which kind
of nucleic acid?
A. DNAB. ATPC. tRNAD. RNA
100
What molecule is produced by the phosphorylation of ADP?
A. ATPaseB. ATPC. Adenosine DiphosphateD. Uridine Triphosphate
101
Compounds Important to Physiology
Table 2–8
102
SUMMARY
• Atoms, molecules, and chemical bonds control cellular physiology
• Metabolism and energy work within the cell
• Importance of organic and inorganic nutrients and metabolites
103
SUMMARY
• Role of water and solubility in metabolism and cell structure
• Chemistry of acids and bases, pH and buffers
• Structure and function of carbohydrates, lipids, proteins, and nucleic acids