All Organisms Contain the Same Four
Classes of Large Biomolecules
• lipids - hydrophobic
=> macromolecules - chains of subunits
• polysaccharides - repetitive macromolecules
=>information macromolecules
•proteins
•nucleic acids

constituents of hydrated and dry organisms
Figure 3.2

All Organisms Contain the Same Four
Classes of Large Biomolecules
• large biomolecules consist of the same subunits in all organisms
• large biomolecules are assembled, fresh from their subunits, by each organism

similar reactions assemble and disassemble all classes of large biomolecules
Figure 3.3

Table 3.1

Four Classes of Large Biomolecules
• Lipids
– defined by hydrophobicity
– chemically diverse hydrocarbons
– several functions, e.g.
• energy storage - fats & oils
• cell structures - membranes
• regulation - steroid & other hormones
• insulation - electrical & thermal

Four Classes of Large Biomolecules
• Lipids
– triglycerides
• fats solid at 20˚C; oils liquid at 20˚C
• energy per gram > carbohydrates or proteins

triglyceride synthesis (esterification)
Figure 3.18

saturated fats, oils, cis, trans
Figure 3.19
unsaturated

Four Classes of Large Biomolecules
• membrane lipids
– phospholipids
• diglycerides + polar head group
• amphipathic

a membrane phospholipid
Figure 3.20

biomembrane segment
Figure 5.2

amphipathic membrane phospholipids
Figure 3.21

Four Classes of Large Biomolecules
• other lipid classes - carotenoids (isoprenoids)
• Figure 3.22
H
2
CH
3
C = C – C = CH
2
H

Four Classes of Large Biomolecules
• other lipid classes - steroids (isoprenoids)
• Figure 3.23
H
2
CH
3
C = C – C = CH
2
H

Four Classes of Large Biomolecules
• other lipid classes - vitamins
– Vitamin E
– Vitamin K

Four Classes of Large Biomolecules
• other lipid classes - waxes
– high molecular weight, hydrophobic compounds
– useful for waterproofing p. 54

Four Classes of Large Biomolecules
• carbohydrates: sugars & their polymers
– monosaccharides - subunits of polymers
• trioses, tetroses, pentoses, hexoses, etc.
–families of structural & optical isomers
• aldoses; ketoses
• monosaccharides ≥5 C’s occur in 3 forms
• modified monosaccharides play important roles

a triose and two pentoses
Figure 3.14

three hexoses
Figure 3.14
2 aldoses and a ketose

~1% three forms of glucose
Figure 3.13
 anomers
~99%

modified monosaccharides and a polysaccharide
Figure 3.17

Four Classes of Large Biomolecules
• carbohydrates: sugars & their polymers
– monosaccharides - subunits of polymers
– di saccharides
• two monosaccharides linked by a specific glycosidic bond
–differ by subunits & linked carbons

two glucose-glucose disaccharides
Figure 3.15

Four Classes of Large Biomolecules
• carbohydrates: sugars & their polymers
– monosaccharides - subunits of polymers
– disaccharides
– oligo saccharides
• 3-20 monosaccharides linked by glycosidic bonds

Four Classes of Large Biomolecules
• carbohydrates: sugars & their polymers
– monosaccharides - subunits of polymers
– disaccharides
– oligosaccharides
– poly saccharides
• thousands of monosaccharides linked by glycosidic bonds

 -1,4 polyglucose
Figure 3.16

 -1,4 polyglucose with  -1,6 branche
Figure 3.16

three forms of polyglucose
Figure 3.16

Four Classes of Large Biomolecules
• proteins: polymers of amino acid subunits
– widely diverse functions
• structure, protection, transport, defense, regulation, movement, catalysis
– thousands of unique structures
• some bind prosthetic groups
– enzymes are chemical catalysts
• functions are defined by 3-D shape

Four Classes of Large Biomolecules
• proteins: polymers of amino acid subunits
– twenty kinds of (protein) amino acids
– four levels of structure
• primary - sequence of amino acids
–amino (N) terminus & carboxy (C) terminus

carboxylic amine
H
2
N - C - COOH
R variable amino acids share a common structure but have different
R groups

Amino acids organized by R groups
Figure 3.2

cysteines can form disulfide bridges
Figure
3.4

peptide bonds join the carboxyl group to the amino group long chains are called polypeptides
Figure 3.5

Figure 3.6 The Four Levels of Protein Structure
1. Primary Structure: Polypeptide chain
2. Secondary Structure: a.

Helix b.

Pleated sheet
3. Tertiary Structure: Polypeptides fold
4. Quaternary Structure: Polypeptides assemble into larger molecules
Figure 3.6

Four Classes of Large Biomolecules
• proteins: polymers of amino acid subunits
• tertiary & quaternary structures are stabilized by several interactions
• H-bonds - between polar R groups
• ionic interactions - between charged R groups
• hydrophobic interactions - between non-polar R groups
• disulfide bridges - between cysteines

interactions that stabilize
3-D structures
Figure 3.9

Four Classes of Large Biomolecules
• proteins: polymers of amino acid subunits
– 3-D folding is assisted by molecular chaperones
• during formation
• following denaturation

protein denaturation
Figure 3.11

chaperones assist in folding polypeptides
Figure 3.12

Four Classes of Large Biomolecules
• nucleic acids: polymers of nucleotide subunits
– DNA (deoxyribonucleic acid),
& RNA (ribonucleic acid)
– Store (DNA), transmit (DNA) & express
(RNA) hereditary information
– The Central Dogma of Molecular Biology
Information Flow
DNA=>RNA=>polypeptide

Four Classes of Large Biomolecules
• nucleic acids: polymers of nucleotide subunits
– nucleotide components
• pentose sugar
• nitrogenous bases
–purines: adenine, guanine
–pyrimidines: cyosine, thymine, uracil
• phosphate group O -
O=P-O-
O -

5-carbon sugars: pentoses
Figure 3.13

5 bases
Figure 3.24

nucleotide components
Figure 3.24

Four Classes of Large Biomolecules
• nucleic acids: polymers of nucleotide subunits
– nucleotides
• linked by phosphodiester bonds
–sugar-phosphate backbone

Figure 3.25 Distinguishing Characteristics of DNA and RNA
Hydrogen bonds between purines and pyrimidines hold the two strands of DNA together.
Figure 3.25

DNA double helix
Figure 3.27

doublestranded segments in a singlestranded
RNA
Figure 3.26