Transcript Chemistry of Life

Pages 22-40

The science of structure and interactions of
matter (anything that occupies space and has
mass)
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Recall:
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Chemical elements are substances that cannot be
broken down into a simpler form by ordinary means
Chemical symbols are the one or two letters of the
element’s name designated to represent that element
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26 elements found in human body; 4 of them
make-up 96% of the human body
Carbon 18%
 Oxygen 65%
 Hydrogen 10%
 Nitrogen 3%
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Another 8 make-up 3.8%
And the final 14 make up 0.2%, these are called
trace elements
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Ion charged particle (atom) that has lost or
gained an e
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Example : Ca 2+; has given up two electrons
Molecules are formed when two or more atoms
share electrons. Can be same elements sharing or
different elements sharing
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Recall: molecular formulas show number and type of
atoms
 Example: 2H2O
2 molecules of water composed of 2 atoms
of hydrogen; one oxygen atom each
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A compound is a molecule containing two or more
different elements
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Forces that bind the atoms of molecules and
compounds together, resisting their separation
Chemically stable atoms have 8 electrons in their
outer shells, and unlikely to form chemical bonds
 Atoms without 8 electrons in their outer shell form
chemical bonds easily because they want eight (octet
rule)
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Three general types of chemical bonds:
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Ionic bonds
Covalent bonds
Hydrogen bonds
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Force of attraction between ions of opposite
charge
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Cation: protons exceed electrons = positively
charged atom
Anion: electrons exceed protons = negatively
charged atom
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Nnn
Give strength to the tissue
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Most other ions in the human body are found
dissolved in body fluids….
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Ionic compounds that break down into cations and
anions when dissolved are called electrolytes; they can
conduct an electrical current
 Function examples:
 Control water movement within the body
 Maintain acid-base balances
 Produce nerve impulses
 Transport nutrients
 Support mental function
 Convert calories into energy
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No electrons lost or gained; atoms form
molecules by sharing one, two, or three pairs of
their outer shell electrons
The more pairs shared the stronger the bond
 Most common type of bonding in human body
 Do not easily break apart in water (ionic bonds do)
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Single covalent: two atoms share one electron pair
Double covalent: two atoms share two electron
pairs
Triple covalent: two atoms share three electron
pairs
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Nonpolar covalent: atoms share equally one
atom does not attract the shared electrons more
strongly than the other atom
Polar covalent: atoms share unequally one
atom attracts the shared electron more strongly
than the other
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Polar covalent bonds between hydrogen and
other atoms is the third type of chemical bond
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Hydrogen is slightly positively charged and attracts
another atom with a slightly negative charge;
attraction between oppositely charged parts of
molecules rather than sharing of electron
These are weak bonds
Do not bind atoms into molecules; rather create
a link between molecules or between different
parts of a large molecule, like DNA
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Defined: ion or molecule with an unpaired
electron in its outermost shell; highly unstable;
destructive to other nearby
molecules…WHY???
They will steal an electron or give one up to
another ion or molecule thus damaging it
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Produced during metabolic activity
How? Exposure to certain substances in our
environment can impede normal metabolic
processes during which ions and molecules
separate in our cells…
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Sunlight
Automobile Exhaust
Cigarette Smoke
Alcohol Consumption
Emotional Stress
Exposure to Heavy Metals
 i.e.: Mercury, Cadium, Lead
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ANTIOXIDANTS!!!!!!
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THEY NEUTRALIZE FREE RADICALS…
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The antioxidants within food are not all the same.
Some antioxidants prevent destruction, while
others interrupt the effect of free radicals. Vitamin
C, for example, breaks the chain reaction of free
radical damage.
Studies have shown that antioxidant supplements
do not have the same beneficial effects as a diet full
of fruits and vegetables. In fact, there are concerns
that the amount of antioxidants, such as betacarotene, ingested through a daily supplement
may be unsafe.
Therefore, it is important to consume a variety of
foods with antioxidant qualities rather than take a
supplement to get the beneficial effect.
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Many experts believe the aging process is due
to free radicals that damage DNA and decrease
organ function
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Occurs when new bonds form and/or old
bonds break
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Enables body structures to be built and functions to
be carried out through energy transfers
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ENERGY capacity to do work
Two main forms:
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Potential energy: energy stored by matter
due to its position
 Example: sitting at the top of a slide waiting to
go down
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Kinetic energy: energy of matter in motion
 Example: sliding down the slide
CHEMICAL ENERGY IS A FORM OF
POTENTIAL ENERGY STORED IN THE
BONDS OF MOLECULES
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Synthesis Reaction (“to put together”)
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Two or more atoms, ions, or molecules combine to
form new and larger molecules (anabolic)
Decomposition Reaction
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A molecule is split apart into smaller parts
(catabolic)
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Exchange Reaction
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Consists of both synthesis and decomposition
reactions
Reversible Reaction
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Reactions that can go either way under different
conditions, either building up or breaking down
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Chemicals in human body divided into two main
classes of compounds:
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Inorganic compounds
 Lack carbon
 Structurally simple
 Bonded ionically or covalently
 Examples: water, many salts, acids, and bases
 Exceptions: two-carbon compounds
 carbon dioxide and bicarbonate ions
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Organic compounds; contain carbon and usually also
hydrogen
 Covalently bonded
 Examples: carbohydrates, lipids, proteins, nucleic acids, and
ATP (all macromolecules)
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Water most important one physiologically, also
most abundant compound in all living systems
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55% to 60% of body mass in lean adults
Cells also are mostly composed of water
WHY IS WATER THE MOST IMPORTANT???
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UNIQUE PROPERTIES….due to its polar covalent
bonds and its ‘bent’ shape (can interact with four
or more ions or molecules)
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Solvency
Water..continued
 Recall:
 Solvent  liquid or gas in which some other substance can
dissolve
 Solute  substance that is dissolved in a solvent
 Solution  combination of a solvent and a solute
Importance of the property physiologically:
Carries nutrients, oxygen, and wastes throughout the body
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Excellent medium for chemical reactions; b/c
dissolves so many substances
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Medium for  some decomposition and synthesis
reactions
 Examples:
 Digestion decomposition breaks down large nutrient
molecules by adding water so they can be absorbed
 Reaction called hydrolysis
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Absorbs and releases heat very slowly
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Requires a huge amount of heat to change form
liquid to gas
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Thus regulates body temperature = homeostasis
Thus remains liquid sweat long enough to act
cooling mechanism for body
Acts as a lubricant
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Saliva, mucus, and others
 Important in thoracic and abdominal cavity, allow
internal organs to touch and slide over one another
 Needed in joints, so bones, ligaments, and tendons can
run against one another
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Acid: breaks apart; disassociates into one or
more H+ ions in water
Base: breaks apart; disassociates into one or
more OH- ions in water
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Acids and bases react together to form salts
 Example: NH3 + HCl → NH3Cl
Ammonia + Hydrochloric acid  Ammonium chloride
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Salt: breaks apart; disassociates into cations
and anions in water; neither are H+ ions or OHions
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Homeostasis maintained through a balance between acid
and base quantities in the human body
More H+ ions  acidic (acidity);
 More OH- ions  basic (alkalinity)
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Solutions acidity/alkalinity expressed as pH
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Recall pH scale 0 to 14
 pH of 7 is neutral (pure water); H+ ions = OH- ions
 pH below 7 acidic; H+ ions > OH- ions
 pH above 7 basic (alkaline); H+ ions < OH- ions
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Each whole number change on scale = 10-fold change in
number of H+ ions
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pH level limits in body fluids very narrow in scope
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Examples:
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Blood 7.35 - 7.45
Urine 6.5 -7.0 a.m.; 7.5 - 8.0 p.m.
Digestive system      
Lysosomes 4.0 -4.5
Cytosol 7.2 - 7.4
Mitochondrial matrix 7.5 - 7.8
Buffers convert strong acids
and bases into weak acids and
bases to maintain optimum
pH levels in body fluids
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Carbohydrates
Lipids
Proteins
Enzymes
Nucleic acids
Adenosine triphosphate
A
F
B
E
D
C
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Sugars, glycogen, starches, and cellulose
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Contain C, H, and O (1:2:1 ratio; i.e. C6H12O6)
Three major groups of carbohydrates:
Monosaccharides, simple sugars
 Disaccharides, simple sugars
 Polysaccharides, complex carbohydrates
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Monomer of carbohydrates
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Most important one=> glucose; source of chemical
energy fro generating ATP
Others => ribose and deoxyribose used to make
RNA and DNA
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Two monosaccharides bonded together
covalently through dehydration synthesis
Can be broken back down into
monosaccharides through hydrolysis
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Contain tens or hundreds of monosaccharides
joined through dehydration synthesis; can be
broken down through hydrolysis
Main polysaccharides in human body => glycogen;
made entirely of glucose
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Stored in liver cells
Also in skeletal muscles
Why do you think it is composed entirely of glucose; for
what purpose????
Plants make starches ; we consume them and break them
down to glucose to be used as an energy source
Cellulose is the polysaccharide found in plant cell walls, we
cannot digest it… provides us with roughage to aid digestive
processes
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Contain C, H, and O
Hydrophobic (insoluble in water) because of fewer
polar covalent bonds
Includes:
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triglycerides (fats; solids and oils; liquids at room temperature)
Phospholipids
Steroids
fatty acids
fat-soluble vitamins (A, D, E, and K)
Provide body with chemical signals, insulation,
padding and stored energy (two times as much as
carbohydrates or proteins)
Large amounts can contribute to heart & blood vessel
disease
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Most plentiful in human body
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Stored in fat tissue called adipose tissue
 Excess dietary carbohydrates, proteins, fats, and oils
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Composed of three fatty acids (hydrocarbon) &
a 3-C glycerol
Fatty acids can be saturated, monounsaturated,
or polysaturated
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Saturated
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Single covalent bonds between carbons
 Allows saturation of hydrogen atoms
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Found mainly in animal products, mostly fats
 Also a few tropical plants: cocoa, palm, coconut
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Solid at room temperature
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Monounsaturated (Unsaturated)
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Contains one double covalent bond between two
carbons
 Lowers hydrogen atom saturation
Usually liquid at room temperature
 Examples: olive oil, peanut oil
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Polyunstaurated
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More than one double covalent bond
Examples: canola oil, corn oil, safflower oil,
sunflower oil, soybean oil
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Phospholipids
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Glycerol backbone with only two fatty acids attached to
two carbons and a phosphate group attached to the third
carbon
 Nonpolar fatty acids are hydrophobic “tails”
 Polar phosphate group are hydrophilic “heads”
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Build body structures, make up cell membranes
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Have complex carbon skeleton with 4 rings
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Cholesterol – steroid body cells uses to synthesize
other steroids
 Examples:
 Cells in ovaries synthesize estradiol (female sex hormone)
 Leydig cells (found in testicles) synthesize testosterone
(male sex hormone)
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Contain C, H, O, and N
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Some also contain S
Make up about ½ the body’s dry mass
Serve a multitude of functions:
Structure of body cells; like muscles, tendons, bones,
skin, etc.
 Act as enzymes; speeding up chemical reactions
 Aid in muscle contractions
 Some are antibodies; others are hormones; gene
regulators; components of blood
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Building block (monomer) of proteins
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Union of two or more amino acids produces a peptide bond
 United molecule composed of two amino acids called a dipeptide
 Three amino acids united called tripeptide
 More than three united called polypeptide; these form proteins
 Sequence is crucial for proper function
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Made of amino group (NH2), carboxyl group
(COOH) and one of many side or “R” (radical)
groups
20 different varieties of amino acids in human body
Protein function is
highly sensitive to
protein structure!!!
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Primary Protein Structure:
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sequence of amino acids
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Secondary Protein Structure:
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Sequence of amino acids linked by hydrogen bonds
to form new shape, such as…
Pleated
sheath
Helix
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Tertiary Protein Structure
Folded shape of protein when there are attractions
between alpha helices & pleated sheets
 Denaturation occurs when hydrogen bonds holding
shape together are broken
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The change in the shape of a protein molecule
without breaking peptide bonds
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Is irreversible!
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Changes or halts what the protein does
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Is caused by…
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Quaternary Protein Structure
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Protein consisting of more than one amino acid chain
Model of myoglobin – an oxygen-storing
protein found in muscles
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Enzymes are proteins; usually end in –ase
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Named for type of chemical reaction they catalyze
Speed up chemical reactions by increasing the
frequency of collisions and by properly
orienting the colliding molecules
They are called catalysts because they speed up
reactions without being altered themselves and
can be used over and over again
Important properties: specificity, efficiency,
and control…
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Specificity: highly specific
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Each enzyme catalyzes a particular chemical reaction that
involves specific substrates (molecule upon which the enzyme
acts)
 Specific products are produced
 Enzyme and substrate fit together like a lock-n-key
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Efficiency: single enzyme molecule can convert
substrate molecules to products at rate of 600,000 per
second…
Control: regulated by cell’s genes; sets rate of synthesis
by enzymes and their concentration
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Co factors/ coenzymes: non-protein substances affect rate at
which inactive enzyme forms become active and visa versa
 Cofactors: ions of iron, zinc, magnesium, or calcium
 Coenzymes: niacin, riboflavin, derivatives of Vitamin B
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Heat
pH
Concentration of substrate
Competitive inhibitors
Noncompetitive inhibitors
Lack of cofactors
Defective genes
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Contain C, H, O, N, and P
Two types of nucleic acid:
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DNA (deoxyribonucleic acid); double helix, 2 strands
RNA (ribonucleic acid); one strand
Nucleic acid molecule made up of repeating nucleotides
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DNA nucleotides consists of: four different nitrogenous bases
(adenine, guanine, cytosine, and thymine), 5-C sugar
(deoxyribose), and a phosphate group
RNA nucleotides consists of: four different nitrogenous bases
(adenine, guanine, cytosine, and uracil), 5-C sugar (ribose), and
a phosphate group
Nitrogenous bases are bonded together by hydrogen bonds
These carry genetic materials and transfer energy from food to body
functions
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“Energy Currency” of living organisms
Main function: transfer energy from energy-releasing
reactions to energy-requiring reactions that maintain
cellular activities Examples: contraction of muscles,
movement of chromosomes during cell division,
movement of structures within a cell, transport of
substances across cell membrane, and synthesis of
larger molecules from small ones
Adenosine composition = adenine + ribose
Hydrolysis reduces ATP to ADP (adenosine
diphosphate) thus releasing its stored energy
ATP synthase and energy from glucose promotes the
addition of a phosphate group to ADP to reenergize it
to ATP