Concepts of Biology 2nd Edition

1. Chapter 3
Organic Molecules and Cells

2. The Variety of Organic Molecules
Makes Life Diverse
The chemistry of carbon makes diverse molecules
possible
• Organic Chemistry – the chemistry of carbon
• Carbon has 6 electrons so it needs to bond with
other elements (CHNOPS) to fill its outer shell
• Hydrocarbons – chains of carbons bonded to
hydrogen
• Carbon can have single, double, or triple bonds

3. • Biomolecules are made of 4 classes
– Carbohydrates
– Lipids
– Proteins
– Nucleic acids
• Carbon is the essential ingredient to
biomolecules
• Functional groups add to the variety of
biomolecules
– Carbon chain – backbone of a biomolecule
– Functional group – specific combination of bonded
atoms that always react in the same way, regardless
of the particular carbon backbone
– R – rest of the molecule

4. -OH (hydroxyl) turns a
molecule into alcohol
-COOH (carboxyl) when it
ionizes, releases hydrogen
ions making a solution more
acidic

5. Isomers – organic molecules that have identical
molecular formulas but a different arrangement
of atoms

6. Molecular subunits can be linked to
form varied large biomolecules
• Polymer
– Largest of the biomolecules
– Made of many monomers
– Glucose is a monomer of starch, a polymer
– Proteins are made up of many amino acids
– Nucleic acids contain many nucleotides

7. To create a polymer, a dehydration reaction occurs
• A water molecule (-OH and –H) is removed
• A bond between two monomers results

8. Degredation of a biomolecule requires a hydrolysis (“water”
“breaking apart”) reaction
• -OH attaches to one subunit
• -H attaches to the other subunit
Enzyme – molecule that speeds a reaction by bringing
reactants together

9. Carbohydrates are energy sources
and structural components
Simple carbohydrates provide quick energy
• Monosaccharide
– Single sugar molecule
– Carbon backbone of 3-7 carbons
• Glucose (C6H12O6)
– Monosaccharide with 6 carbons
– Glucose has isomers such as fructose and galactose
• Ribose and deoxyribose
– Monosaccarides with 5 carbon atoms
– Found in RNA and DNA respectively

10. • Disaccharide
– Contains two monosaccharides joined during a
dehydration reaction
– Maltose, sucrose (table sugar), and lactose are
disaccharides
– People with lactose intolerance cannot break down
the disaccharide into monosaccharides
– When disaccharides come into the body, a hydrolysis
reaction occurs

11. Complex carbohydrates store energy
and provide structural support
Complex carbohydrates are polysaccharides
(polymers of monosaccharides)
• Some polysaccharides (glycogen and starch)
are storage molecules
– Potatoes contain starch during the winter until it is
needed for growth in the spring
• Structural polysaccharides
– Cellulose in plants
– Chitin in animals
– Peptidoglycan in bacteria

12. Lipids store energy and have other functions
Fats and oils are rich energy-storage molecules
• Fats and oils consist of
– Glycerol – a compound with 3 –OH groups
– Fatty acids – a compound with a long hydrocarbon chain with a
–COOH group at one end
• Fat or oil formation
– 3 fatty acids (-COOH portion) react with –OH of glycerol during a
dehydration reaction

13. • Saturated fatty acid
– No double bonded carbons
– No kinks
– Tightly packed solid
• Unsaturated fatty acids
– Double bonded carbons
– Kinks
– Liquid
• Trans fats
– Double bonds
– Hydrogens are on different sides of the chain (trans means across)
Saturated and trans fat cause plaque buildup in blood vessels
Unsaturated protects against plaque buildup

14. Other lipids have structural,
hormonal, or protective functions
Phospholipids, steroids, and waxes
• Phospholipids
– Glycerol, 2 fatty acids, phosphate
– Fatty acids are hydrophobic
– Head is hydrophilic
– In water a phospholipid bilayer naturally occurs
• Cell membrane is a phospholipid bilayer
• Steroids
– 4 fused carbon rings
– Cholesterol – participates in plaque formation
– Estrogen and testosterone – sex hormones
• Waxes
– Combines fatty acids and alcohols
– Hydrophobic so waterproof and resistant to degredation
– Plant leaves, animal skin and fun, ear canal, honey storage

15. Proteins have many vital functions
Proteins are the most versatile of life’s molecules
• Proteins – polymers of amino acids
– Support
• Structure
• Silk, hair, fingernails
– Metabolism
• Enzymes – bring reactants together
– Transport
• Allow substances to enter and exit cells
– Defense
• Antibodies
– Regulation
• Hormones
• Intercellular messengers
– Motion
• Contractile proteins allow parts of the cell to move and cause muscles to
contract

16. Each protein is a sequence of particular amino acids
• A monomer of a protein is an amino acid
• Amino acids have
– Central carbon
– Hydrogen atom
– -NH2 (amino group)
– -COOH (acid group)
– R group
The R group differs in amino acids and make them
different

18. • Amino acids bond via a dehydration reaction
• Peptide – two or more amino acids bonded
together
• Polypeptide – chain of many amino acids joined
by peptide bonds
• Peptide bond – covalent bond between two
amino acids
– Oxygen attracts electrons more than nitrogen
– Oxygen is slightly negative
– Hydrogen is slightly positive
– Polarity allows hydrogen bonds between –CO of one
amino acid and –NH of another amino acid

20. The shape of a protein is necessary
to its function
• Collagen
– Provides strength and support
– Super-coiled
• Hemoglobin
– Globular
– Allows it to travel in blood vessels
Extreme temperatures and pH can denature (alter
shape) so it can no longer perform its usual
function
Alcohol and salts of heavy metals also denature
proteins

21. Levels of Protein
Organization
• Primary structure
– Linear
– Sequence of amino
acids joined by peptide
bonds
• Secondary structure
– Peptide bond is polar
– Hydrogen bonds form
alpha helix (spiral) or
pleated sheet

22. • Tertiary structure
– Final shape for
globular proteins
– Hydrophobic portions
are packed on the
inside
– Hydrophilic portions
are on the outside
– Covalent, ionic, and
hydrogen bonds
between R groups are
present
• Quaternary structure
– More than one
polypeptide coming
together

23. Nucleic acids are information
molecules
DNA stores coded information
• Genes
– Hereditary units composed of DNA (deoxyribonucleic
acid)
– Control structure and function of cells and organisms
by coding for proteins
• Nucleotide contains
– Phosphate
– Pentose (5 carbon) sugar
– Nitrogen containing base
• Nucleic acid
– Polymer of nucleotides

24. • DNA and RNA (ribonucleic acid) are
nucleic acids
• DNA structure contains complementary
paired bases that are held together by
hydrogen bonds
– Thymine (T) always pairs with Adenine (A)
– Guanine (G) always pairs with Cytosine (C)
• Genome – DNA base sequence of all
genes of an organism

25. Genetic information flows from
DNA to RNA to proteins
• RNA bases include adenine, guinine, uracil, and cytosine
• RNA is synthesized next to a segment of DNA
• Messenger RNA (mRNA) is a copy of a gene that codes
for proteins
• DNA to mRNA to protein

26. Genetic mutations can result in
altered proteins
• Genetic mutation
– Change in the sequence of bases, can result in an altered amino
acid sequence in a protein
• Sickle-cell
– Amino acid valine (Val) appears instead of glutomate (Glu)
resulting in sickle shaped red blood cells
– Double mutation inheritance
• Hard and jagged cells
• Can clog vessels
• Pain, organ damage, low red blood cell count
– Single mutation inheritance
• Occasionally sickle shaped such as when invaded with malarial
parasite
• Shape causes parasite to die
• Individual has advantage
• More common in Africa where malaria is prevalent

27. The nucleotide ATP is the cell’s
energy carrier
Adenosine triphosphate (ATP)
• Adenine base and ribose
– Form adenosine
• 3 phosphate groups
• High energy molecule because last two phosphates are
unstable
• ADP (adenosine diphosphate) and phosphate molecule
– Created when the last phosphate bond is hydrolyzed

28. • ATP breaks down, releases energy, which
is used by cells to create biomolecules
• Muscle cells use it for muscle contractions
• Nerve cells use it for nerve impulses