Humes
Biology
Chapter 3
Biochemistry
Carbon Compounds- all compounds can be classified into two broad categories: organic
compounds and inorganic compounds
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Organic compounds are made primarily of carbon atoms
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Inorganic compounds with a few exceptions, do not contain carbon. Carbon dioxide is
inorganic and has carbon
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A carbon atom has 4 valence electrons and readily forms 4 covalent bonds to achieve
stability
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It can bond with other elements or can bond with itself
o It can form carbon to carbon single bonds
o It can form carbon to carbon double bonds
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o It can form carbon to carbon triple bonds
o It can form rings
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Large Carbon Molecules
o Many carbon compounds are built up from smaller, simpler molecules known as
monomers
o Monomers can bond to one another to form polymers. Polymers form by linking
many monomers together
o Large polymers are called macromolecules
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Examples of macromolecules are carbohydrates, proteins, lipids, and
nucleic acids
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Condensation reactions are chemical reactions that link monomers to
form polymers
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Each time a monomer is added to a polymer, a water molecule is
released
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One monomer releases a hydroxide ion (OH-) and the monomer
linking to it release a hydronium ion (H+)
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These ions combine to produce water (H2O)
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Hydrolysis Reactions use water to break down polymers into monomers
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Water molecules break the bonds linking each monomer
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One molecule receives a hydroxide ion while the other molecule
receives a hydronium ion from water
Energy Currency
o Adenosine triphosphate (ATP) is a molecule that can store large amounts of
energy in its structure
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It consists of a five carbon sugar, ribose, adenine, and three phosphate
groups.
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The energy is stored in the bonds between the phosphate groups
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When a bond between the phosphate groups is broken, energy is
released
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The hydrolysis of ATP is used by our cells to provide the energy necessary
to perform chemical reactions that enable an organism to function
Functional Groups clusters of atoms that influence the characteristics of the molecules
they compose
o
Molecules of Life
1. Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen in a
ratio of about one carbon to two hydrogen to one oxygen
a. Monosaccharide or simple sugar is a monomer of a carbohydrate
i. Contains carbon, hydrogen, and oxygen in a 1:2:1 ratio
ii. Most common monosaccharides are
1. Glucose- main source of energy for cells
2. Fructose- found in fruits and is the sweetest of the
monosaccharides
3. Galactose- is found in milk
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iii. Isomers are compounds with the same chemical formula but different
structural formulas
iv. Example: Glucose,fructose, and galactose all have the chemical formula
C6H12O6 but are assembled differently
b. Disaccharides are two monosaccharides bonded together
i. Example: When the monosaccharides glucose and fructose bond
together they make sucrose, table sugar
c. Polysaccharides are complex molecules composed of three or more
monosaccharides
i. Animals store glucose as glycogen, a polysaccharide that consists of
hundreds of glucose molecules bonded together in branched chains
1. It is stored in the liver and muscle cells and is used for quick
energy
ii. Plants store glucose in the polysaccharide starch. Starch is similar to
glycogen in that it is a highly branched chain molecule
iii. Plants also make cellulose (fiber) which gives strength and rigidity to
their stalks and stems. Cellulose is thousands of glucose molecules linked
in straight chains. These chains form hydrogen bonds with each other to
form a rigid structure
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2. Proteins- organic composed mostly of carbon, hydrogen, oxygen, and nitrogen.
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They are made by linking amino acids in a condensation reaction.
o There are 20 different amino acids
o Amino acids are composed of a central carbon atom attached to
 A single hydrogen atom
 A carboxyl group (COOH)
 An amino group (NH2)
 An R-group.
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The R-group can be as simple as a CH3 to a complex molecule
The R-group is the only difference among each amino acid
It contributes to each proteins shape
The different shapes of protein allow it to carry out many
different functions
o Shape of a protein molecule is influenced by the number
and arrangement of amino acids
 Temperature may also affect a proteins shape
 Example: raw egg vs. cooked egg
Hair, horns, nails, skin, muscles, and enzymes are all examples of proteins
A Dipeptide is formed when two amino acids link in a condensation reaction
o The bond that forms between them is a peptide bond
Polypeptides are very long chains of amino acids bonded by peptide bonds
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Biology
o Proteins are composed of one or more polypeptides
Enzymes- RNA or protein molecules that act as a biological catalyst
o Induced fit model- enzyme reaction depends on a physical fit between the
substrate and the enzyme
o The substrate fits into the active site on the enzyme. The enzyme changes shape
forcing the reaction to occur. The change in the enzymes shape weakens bonds
in the substrate which allows the reaction to happen much faster reducing
activation energy
 Enzyme activity is affected by temperature and pH.
3. Lipids- large non-polar organic molecules
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They do not dissolve in water
Lipids include triglycerides, phospholipids, steroids, wax, and pigments
They have a higher ratio of carbon and hydrogen atoms to oxygen atoms
o This causes them to have more carbon to hydrogen bonds which store more
energy….hence fats having a higher caloric value
Fatty acids- unbranched carbon chains that make up most lipids
o They are long carbon chains with a carboxyl group at the end (COOH)
o The carboxyl end in polar and thus hydrophilic-attracted to water
o The hydrocarbon end is non-polar and thus hydrophobic- water fearing
o Saturated fatty acid-a fatty acid where all the carbon to carbon bonds are single
bonds
o Unsaturated fatty acid- there is at least on carbon to carbon double bond
Three classes of important lipids
o Triglycerides7
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
Saturated triglycerides
 Composed of saturated fatty acids
 Have high melting points
 Tend to be solids at room temperature
 Examples include butter and fat in red meats
 Unsaturated triglycerides
 Composed of unsaturated fatty acids
 Soft or liquid at room temperature
 Found in plant seeds where they serve as an energy source for
germinating seeds
o Phospholipids
 Composed of 2 fatty acids joined to a glycerol molecule
 Found in cell membranes also called the phospholipid bi-layer because it
is composed of 2 layers of phospholipids
o Waxes
 Composed of a long fatty acid chain joined to a long alcohol chain
 Wax can be found on the outside of plants to prevent water loss
especially through leaves
 Can also be found in your ears where it prevents microorganisms from
entering the ear canal
o Steroids
 Composed of four fused carbon rings with various functional groups
attached to them
 Cholesterol is a steroid needed by the human body for nerve and other
cells to function normally
4. Nucleic acids- very large complex organic molecules that store and transfer important
information in the cell. There are two major types
 DNA or deoxyribonucleic acid
o Contains information that determines the characteristics of an organisms
o Directs cellular activities
o Contains the sugar deoxyribose
 RNA or ribonucleic acid
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o Stores and transfers information from DNA that is essential for the
manufacturing of proteins
o RNA molecules can also act as enzymes
**Both DNA and RNA are polymers composed of thousands of linked monomers called
nucleotides. Each nucleotide is made of three parts; a phosphate group, a five carbon sugar,
and a nitrogenous base
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