Biology 101 Chapter 3

1. 3-1
Chapter 3
The Organic
Molecules of Life
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2. • In this section, the following objective will be
covered:
• List the characteristics of a carbon atom that allow it
to form a variety of molecules.
3.1 ORGANIC MOLECULES

3. Organic Chemistry
• Biological molecules
• Organic molecules contain carbon and hydrogen
• Inorganic molecules do not contain a combination of
carbon and hydrogen (H2O and NaCl)

4. THE
CARBON
ATOM
• Total of six electrons—4 in outer shell
• Almost always shares electrons with
nonmetal elements such as hydrogen,
nitrogen, and oxygen
• Can bond with as many as 4 other
elements
• Most often shares electrons with other
carbon atoms
• Hydrocarbons—chains of carbon atoms
bonded only to hydrogen atoms
• Isomers—same number and kinds of
atoms in a variety of arrangements
• May have different properties due to
different shape

5. HYDROCARBONS ARE HIGHLY VERSATILE
Carbon chains can vary in
length, and/or have double
bonds, and/or be branched.
Carbon chains can from rings of
different sizes and have double
bonds.

6. CARBON MOLECULES
• Size and shape of carbon skeleton or backbone can vary
drastically
• Functional group—specific combination of bonded atoms
that always has the same chemical properties and always
reacts the same way
• Reactivity of organic molecule largely dependent on
attached functional groups
• Often use R to stand for the rest of the molecule

7. COMMON FUNCTIONAL GROUPS
Group
Structure Found In
Hydroxyl Alcohols, sugars
Carboxyl
Amino acids, fatty acids
Amino Amino acids, proteins
Sulfhydryl Amino acid cysteine, proteins
Phosphate
R = remainder of molecule
ATP, nucleic acids

8. ORGANIC MOLECULES SERVE AS
STRUCTURAL MATERIALS IN
LIVING ORGANISMS
a: © SuperStock/Alamy; b: © Science Photo Library/Alamy Stock Photo RF; c: © Zeljko Radojko/Getty Images; d: Design Pics/Bilderbuch RF Will & Deni Mclntyre/Science Source

9. • In this section, the following objectives will be
covered:
• Summarize the structure and function of each category of
carbohydrates.
• Summarize the structure and function of each category of
lipids.
• Summarize the structure and function of proteins.
• Summarize the two categories of nucleic acids and
describe their biological functions.
3.2 THE BIOLOGICAL MOLECULES OF
CELLS

10. MACROMOLECULES
AKA BIOMOLECULES
•4 categories:
• Carbohydrates
• Lipids
• Proteins
• Nucleic Acids

11. BIOMOLECULE BASICS
• Monomers—subunits or building blocks of the large molecule
• Polymer—monomers joined together to form a large molecule
• Dehydration synthesis reactions join monomers to form polymers
• Equivalent of removing a water molecule
• Hydrolysis reactions break polymers apart into monomers
• Equivalent of adding a water molecule

12. SYNTHESIS OF POLYMERS

13. BREAKDOWN OF POLYMERS

14. CARBOHYDRATES
• Almost universally used as
immediate energy source in living
things
• Play structural roles
• Polymers of monomers called
saccharides or sugars
• Monosaccharide, disaccharide,
polysaccharide

15. CARBOHYDRATES
• Monosaccharides
• Single sugar molecule
• Simple sugars
• 3–7 carbon backbone
• Glucose C6H12O6
• 2 isomers—fructose and galactose
• Cells use glucose as the energy source of choice.
• Ribose and deoxyribose are found in RNA and
DNA.

16. GLUCOSE
𝐂 𝟔 𝐇 𝟏𝟐 𝐎 𝟔

17. DISACCHARIDES
• Disaccharides
• 2 monosaccharides bonded together
• Maltose—yeast breaks down maltose in beer for
energy and produces ethyl alcohol
• Fermentation
• Sucrose—table sugar

18. BREAKDOWN
OF MALTOSE, A
DISACCHARIDE

19. POLYSACCHARIDES
• Polysaccharides are energy storage
molecules
• Polymers of monosaccharides
• Some function as energy storage molecules.
• Plants store glucose as starch.
• Animals store glucose as glycogen.
• Some function as structural components.
• Cellulose—plant cell walls
• Most abundant of all organic molecules
• Digested only by some microbes
• Chitin—crab, lobster, insect exoskeletons

20. STARCH FUNCTION

21. CELLULOSE STRUCTURE AND FUNCTION

22. GLYCOGEN STRUCTURE

23. CARBOHYDRATE
FOODS

24. LIPIDS
• All are insoluble in water
• Long nonpolar
hydrocarbon chains
• Relative lack of
hydrophilic functional
groups
• Very diverse structures
and functions
• Fats and oils used for
long-term energy storage
• Oil may help waterproof
skin, hair, and feathers.

25. TRIGLYCERIDES
• Fats and oils
• Triglycerides are composed of 1 glycerol
and 3 fatty acids.

26. SYNTHESIS
AND
BREAKDOWN
OF FAT

27. SATURATED OR
UNSATURATED FATS
• Fatty acids are either:
• Saturated—no double bonds
between carbon atoms
• Butter is solid at room
temperature.
• Unsaturated—one or more
double bonds between
carbon atoms
• Oil is liquid at room
temperature.
• Trans fatty acids have
been artificially
hydrogenated to make
them more solid.

28. UNSATURATED FATTY ACID CHAIN

29. SATURATED FATTY ACID CHAIN

30. TRANS FATTY ACID CHAIN

31. LIPIDS IN
CELLS
• Phospholipids
• Form the bulk of the
plasma membrane
• One end of the
molecule is water-
soluble.
• Polar phosphate
head
• Other end of the
molecule is not water-
soluble.
• Nonpolar fatty acid
tails

32. PHOSPHOLIPIDS
FORM
MEMBRANES
PLASMA MEMBRANE OF A CELL

33. STEROIDS
• Lipids made of 4 fused
rings
• Not fatty acids but are
insoluble in water
• Derived from
cholesterol
• Differ only in functional
groups

34. STEROID DIVERSITY

35. LIPID
FOODS

36. PROTEINS
• Proteins are composed of amino acid
monomers
• Central carbon bonded to hydrogen atom, amino group,
carboxyl group, and a side chain, or R group
• 20 different amino acids
• Differ according to R group
• Many functions: support, metabolism, transport, defense,
regulation, and motion
This Photo by Unknown Author is licensed under CC BY

37. AMINO
ACIDS

38. AMINO ACIDS AND
PEPTIDES
• Peptide—two or more amino acids
covalently linked
• Peptide bond—formed by dehydration
reaction between two amino acid
monomers
• Polypeptide—chain of many amino acids
joined by peptide bonds
• Amino acid sequence determines the
final three-dimensional shape of protein
This Photo by Unknown Author is licensed under CC BY

39. SYNTHESIS AND
DEGRADATION
OF PEPTIDE

40. SHAPE OF
PROTEINS
• Function is determined by three-
dimensional shape
• Denature: Loss of structure and
function; usually due to pH or
temperature change
• Primary structure—amino acid
sequence
• Secondary structure—portions of
chain form helices or pleated sheets
• Tertiary structure—overall three-
dimensional shape of interacting
secondary structures
• Quaternary structure—more than one
polypeptide chain interacting

41. LEVELS OF
PROTEIN
ORGANIZATION –
PRIMARY
PRIMARY STRUCTURE:
SEQUENCE OF AMINO
ACIDS

42. LEVELS OF
PROTEIN
ORGANIZATION –
SECONDARY
SECONDARY
STRUCTURE: ALPHA
HELIX AND PLEATED
SHEET

43. LEVELS OF
PROTEIN
ORGANIZATION –
TERTIARY
TERTIARY STRUCTURE:
GLOBULAR SHAPE

44. LEVELS OF
PROTEIN
ORGANIZATION –
QUATERNARY
QUATERNARY
STRUCTURE: MORE
THAN ONE
POLYPEPTIDE

45. PROTEIN
FOODS

46. NUCLEIC ACIDS
• Deoxyribonucleic acid (DNA)
• Stores genetic information
• Ribonucleic acid (RNA)
• Helps to make proteins
• Polymers of nucleotide monomers
• Nucleotide composed of a phosphate, 5-carbon
sugar, and nitrogen-containing base
• 5 types of bases—adenine (A), guanine (G),
cytosine (C), and thymine (T) [DNA only], Uracil
(U) [RNA only]
This Photo by Unknown Author is licensed under CC BY-ND

47. NUCLEOTIDE STRUCTURE
NUCLEOTIDE: PHOSPHATE, SUGAR AND NITROGEN-CONTAINING BASE

48. STRUCTURE OF DNA
• DNA- Genetic information stored in
sequence of bases
• Deoxyribose as sugar
• Double helix
• Complementary base pairing
• Adenine (A) with thymine (T)
• Cytosine (C) with guanine (G)

49. DNA STRUCTURE
DNA STRUCTURE WITH BASE PAIRS: G WITH C AND A WITH T

50. RNA BASES
• RNA
• Ribose as sugar
• Single-stranded
• Uses uracil (U) instead of thymine (T)
This Photo by Unknown Author is licensed under CC BY-ND

51. RNA STRUCTURE
RNA STRUCTURE WITH BASES G, U, A, C

52. CONNECTING
PROTEINS
AND NUCLEIC
ACIDS
• Sequence of bases in DNA determines
sequence of amino acids in a protein.
• Sequence of amino acids determines a
protein's structure and function.
• Small changes in the DNA may cause large
changes in a protein.
• Sickle-cell disease
• Individual’s red blood cells are sickle-
shaped
• One amino acid difference
• Inherited disease

53. SICKLE-CELL DISEASE

54. CHAPTER 3 OBJECTIVE SUMMARY
• You Should now be able to:
• 1. List the characteristics of a carbon atom that allow it to form
a variety of molecules.
• 2. Summarize the structure and function of each category of
carbohydrates.
• 3. Summarize the structure and function of each category of
lipids.
• 4. Summarize the structure and function of proteins.
• 5. Summarize the two categories of nucleic acids and describe
their biological functions.