large biomolecules. all organisms contain the same four classes of large biomolecules lipids -...
TRANSCRIPT
Large Biomolecules
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 organismsFigure 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
fats,
oils,
cis,
transFigure 3.19
saturated unsaturated
Four Classes of Large Biomolecules
• membrane lipids
– phospholipids
• diglycerides + polar head group
• amphipathic
a membrane
phospholipidFigure 3.20
biomembrane segment
Figure 5.2
amphipathic membrane phospholipidsFigure 3.21
Four Classes of Large Biomolecules• other lipid classes - carotenoids (isoprenoids)
• Figure 3.22
CH3
H2C = C – C = CH2
H
Four Classes of Large Biomolecules• other lipid classes - steroids (isoprenoids)
• Figure 3.23
CH3
H2C = C – C = CH2
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
pentosesFigure 3.14
three hexosesFigure 3.14
2 aldoses and a ketose
three forms of glucoseFigure 3.13
anomers ~1% ~99%
modified monosaccharides
and
a polysaccharideFigure 3.17
Four Classes of Large Biomolecules• carbohydrates: sugars & their polymers
– monosaccharides - subunits of polymers
– disaccharides
• two monosaccharides linked by a specific glycosidic bond
–differ by subunits & linked carbons
two glucose-glucose disaccharidesFigure 3.15
Four Classes of Large Biomolecules• carbohydrates: sugars & their polymers
– monosaccharides - subunits of polymers
– disaccharides
– oligosaccharides
• 3-20 monosaccharides linked by glycosidic bonds
Four Classes of Large Biomolecules• carbohydrates: sugars & their polymers
– monosaccharides - subunits of polymers
– disaccharides
– oligosaccharides
– polysaccharides
• thousands of monosaccharides linked by glycosidic bonds
-1,4 polyglucoseFigure 3.16
-1,4 polyglucose with -1,6 brancheFigure 3.16
three forms of polyglucoseFigure 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
amino acids
share a common structure
but have
different R groups
H
H2N - C - COOH
R
aminecarboxylic acid
variable
Amino acids organized by R groupsFigure 3.2
cysteines can form
disulfide bridgesFigure
3.4
peptide bonds join the
carboxyl group to theamino group
long chains are called
polypeptides Figure 3.5
4. Quaternary Structure: Polypeptides assemble into larger moleculesFigure 3.6
3. Tertiary Structure: Polypeptides fold
2. Secondary Structure:a. Helix
1. Primary Structure: Polypeptide chain
b. Pleated sheet
Figure 3.6 The Four Levels of Protein Structure
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
structuresFigure 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 denaturationFigure 3.11
chaperones assist in folding polypeptidesFigure 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 BiologyInformation 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: pentosesFigure 3.13
5 basesFigure 3.24
nucleotide componentsFigure 3.24
Four Classes of Large Biomolecules• nucleic acids: polymers of nucleotide subunits
– nucleotides• linked by phosphodiester bonds
–sugar-phosphate backbone
Hydrogen bonds between purines and pyrimidines hold the two strands of DNA together.Figure 3.25
Figure 3.25 Distinguishing Characteristics of DNA and RNA
DNA double helixFigure 3.27
double-stranded
segments
in a
single-stranded
RNAFigure 3.26