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Basic Chemistry
Chapter 2
Chemistry of Life
• All life processes involve chemical
reactions (clinical day)
– Ex. Ca++ in muscle contraction
Na+, K+ in nerve impulses
Matter
• anything that has
mass and takes up
space
• can you think of
solids, liquids, and
gases that might be
found in the body?
Energy
• the capacity to do work
• No mass & does not
take up space
• Types:
– Potential: stored in
bonds (chemical)
– Kinetic: doing work
(electrical, mechanical,
radiant)
• Exergonic &
endergonic reactions
Composition of Matter
• 92 naturally occurring elements (112 known, 113118 are alleged)
• Living organisms require about 26 of these elements
(table 2.1, p.28)
• About 96% (by mass) comes from Oxygen (O),
Carbon (C), Hydrogen (H), and Nitrogen (N)
Atoms
• smallest complete unit of an element
– Composed of dozens of subatomic particles,
but we are only concerned with THREE!
Subatomic Charge Location
Particle
What it tells you!
Proton
+
Nucleus
Identity of atom, mass
Neutron
0
Nucleus
Isotope, mass
Electron
-
Surrounds
nucleus
Properties of atom,
negligible mass
Identifying Elements
• Atomic number
• equal to the number of protons in an
atom (& electrons in neutral atom!)
• Atomic mass
• sum of the masses of all the protons &
neutrons contained in nucleus
Isotopes
• atoms of same element with a different mass
(due to neutrons) but same chemical properties
• Ex. C-12 and C-14
• Radioactive isotopes used in many medical tests
to tag biological molecules to be followed or
traced
• i.e. PET scans, I-131 for thyroid activity,
destroying localized cancers (Ra, Co, etc.)
Ions
•
•
•
•
Charged particles
Form ionic bonds
Cations (+)
Anions (-)
Find the Face (in the Beans)
Chemical Bonds
• Transfer or share electrons in order to fill
their valence shell (stability)
• All atoms want 8 e- in their valence shell
(except H & He)
• Ionic bond – transfer electrons
• Covalent bond – share electrons
– Nonpolar: shares electrons equally
– Polar: shares electron unequally
Chemical Bonding
• Due to
electronegativity
– How much an atom in
a bond pulls electrons
to itself
– Ionic: >1.7
– Polar covalent: 0.4-1.7
– Covalent: <0.4
Hydrogen Bonding
• Weak bonds
• attraction of H to
partial negative charge
– Example: polar
covalent bonds
between oxygen and
hydrogen
Molecular Formula
• represents the numbers and types of
atoms in a molecule
– Ex. H2O
,
C6H12O6
Chemical Reactions
• Metabolism= sum of all chemical reactions
in the body
– Synthesis (anabolism)
A+B
AB
• Energy absorbing
• i.e. growth, repair, protein synthesis
– Decomposition (catabolism) AB
A+B
• Energy releasing
• i.e. digestion of foods, breakdown of glycogen in
liver to produce glucose
– Single replacement
– Double replacement
AB + C
AB + CD
AC + B
AD + CB
Rate of Chemical Reactions
• Temperature ( temp increases collisions)
• Concentration of reactants ( number =
faster, more collisions)
• Particle size (smaller = faster, more
collisions)
• Presence of catalysts
– Affect rate of reaction without being changed by
reaction
– Biological catalysts: enzymes (proteins)
– Shape matters! Like a puzzle piece
Biochemistry
• Inorganic compounds: lack carbon (with few
exceptions)
– Small, simple molecules
– Water, salts, many acids
& bases
• Organic compounds: carbon-containing
compounds
– Large covalently bonded molecules
– Carbohydrates, lipids, proteins, nucleic acids
Inorganic Compounds
• Water
– High heat capacity
• Absorbs & releases large amounts of heat
• Prevents sudden changes in body temperature
(homeostasis!)
– Polarity/solvent properties
•
•
•
•
“universal solvent”
Chemical reactions depend on solvent
Transport/exchange medium
Lubrication (synovial fluid in joints)
– Chemical reactivity (hydrolysis reactions)
– Cushioning
• Protective (CSF, amniotic fluid)
Inorganic Compounds
• Oxygen
– used to release energy
from glucose
• Carbon dioxide
– waste of metabolic
processes
Inorganic Compounds
• Salts
– Ionic compound containing cations other than H+
and anions other than OH– Vital to body functions
• K+ & Na+ essential for nerve function, Fe2+ is essential
for hemoglobin, Cl-, Ca++, Mg++, PO4-, CO3-, etc.
– All salts are electrolytes (substances that conduct
an electrical current in solvent)
• Release ions when dissolved in water
– Functions in Table 2.1, page 28
Inorganic Compounds
• Acids & Bases
– Electrolytes
• Acids
– Release H+ ions in solution
– “proton donors”
– HCL, acetic acid, carbonic
acid
• Bases
– Release OH- ions in solution
– “proton acceptors”
– HCO3- (important base in
blood)
• pH scale measures
hydrogen ion
concentration
– pH 7 = neutral
– pH >7= basics (more
OH- than H+)
– pH <7= acidic (more
H+ than OH-)
• Normal blood pH for
humans is 7.35 to 7.45
– If > , alkalosis
– If < , acidosis
• Buffers- maintain pH
Organic Compounds
Carbohydrates
• sugars, starches, glycogen, cellulose
– 2-3% body weight
– Plants- starches and cellulose (cannot digest)
– Animals- source of energy- stored as
glycogen
Carbohydrates
• Monosaccharides: 3 to 7 carbons
– Ex. Glucose, fructose, galactose
Many C6H12O6
• Carbohydrate
utilized by the
cell
Carbohydrates
• Disaccharides: 2 monosaccharides combine by
dehydration synthesis (condensation)
– Ex. Sucrose
• Broken apart by hydrolysis (add water)
Carbohydrates
• Polysacchride: 10-100s of monos
– Ex. starch
Lipids
• 18-25% in lean adults
– Contain C, H, O - neutral
– Fats- concentrated energy stored in adipose
tissue
Lipids
• Triglycerides: Glycerol + 3 fatty acids
• Monounsaturated- one double bond
• Polyunsaturated- more than one double bond
• Saturated- no double bonds
Lipids
• Phospholipidspolar head and 2
non-polar tails
(membrane)
Lipids
• Steroids- cholesterol, sex hormones,
cortisol, etc.
Proteins
• 12-18% in lean adults
– Structural and physiological enzymes
– Made of amino acids (20)- held by peptide
bonds
– 3D shape held by H-bonds (denatured with
heat)
Nucleic Acids
– Base + sugar +
phosphate
– DNA and RNA
– ATP- provides energy
for the cell
Isomers
• molecules with the same chemical formula
and with the same kinds of bonds between
atoms, but in which the atoms are
arranged differently.
• share similar if not identical properties in
most chemical contexts.