Transcript ppt

What is the chemical basis of life?
• What are some of the
ideas central to the
chemistry of life?
• (Key concepts of the
chemical basis of life)
Ideas central to the chem of life
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Based on covalent bonding
Carbon is the “backbone” of biomolecules
Simple building code
Variation on common theme in extreme
Only 4 fundamental types of biomolecules
Enzymes make and break the covalent bonds in
the chemical reactions in the cell
• Isomers and polymers
• Condensation and Hydrolysis
Elements Essential to Life
• About 25 of the 92
natural occurring
elements are essential
to life
• CHON = 96% liv mat
• CHONPS = > 99%
Famous ions in Biology
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Hydronium H3O+ and Hydroxide OHPotassium K+ ions
Sodium Na+ ions
Calcium Ca2+ ions
Hydrogen H+ ions (protons)
A continuum view of bonding
• Atoms complete their valence shell in a
continuum of:
• Nonpolar covalent with equal sharing of e– Examples:
H—H
O=O
• Polar covalent, unequal sharing of e– Examples:
H2O
NH3
• Ionic, with complete transfer of e– Examples:
NaCl
Al2O3
Weak Bonds are Bio’ly Important
H bonds, hydrophobic interactions
• Can form between different parts of a
single large molecule or between
molecules
• Help stabilize 3D shape of proteins &
Nucleic Acids
• Hold enzymes to substrates
• Function in chemical signaling
Biological Building Codes
• Covalent Bond=
shared pair of
electrons between 2
nonmetals
• H, 1 unpaired e• O, 2 unpaired e• N, 3 unpaired e• C, 4 unpaired e-
Versatility of Carbon
• 4 valence electrons
• Compatibility with
many different el’s
• S, D, T bonds
• Makes large, complex
molecules possible
– Strait chains
– Branched chains
– Rings
• Polymer
• (poly = many; mer = part)
• Large molecules consisting of many similar
subunits connected together
• Monomer = subunit or building block of
polymer
Macromolecules are Polymers
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Carbohydrates = polymer of monosaccharides
Lipids = polymer of fatty acids & glycerol
Proteins = polymer of amino acids
Nucleic Acids = polymer of nucleotides
Polymers & Molecular Diversity
• Unity in life: Only about 40 or 50 common
monomers build macromolecules
• Diversity in life: New properties emerge
when these monomers are arranged in
different ways
Sucrose Synthesis
Hydrolysis
Making & Breaking Polymers
animation
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Dehydration synthesis
Link monomers
Via removal of H2O
1 water per link (out)
One monomer lose
OH, other loses H
• Any assembling of
molecules in cells
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Hydrolysis
Disassemble polymers
Via addition of H2O
1 water per link (in)
One monomer gains
OH, other gains H
• Any disassembly of
molecules in cells
Carbohydrates (sugars)
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Classified based on # of simple sugars
C H O in 1:2:1 ratio
Major nutrients for cells; ie glucose
Produced by photosynthetic organisms
Store energy in chemical bonds
C skeletons raw materials for other organic
compounds
Carbohydrates-disaccharides
Disacch.
Maltose
Lactose
Sucrose
Monomers
glu + glu
glu + galac
glu + fru
Carbohydrates: Polysaccharides
• 2 Important biological functions:
– Energy storage (starch, glycogen)
– Structural support (cellulose, chitin)
Storage Polysaccharides
• Starch = glucose polymer, for energy
storage in plants
– Helical glucose polymer
– Most animals have enzymes to hydrolyze it
– Major sources in
Human diet are potatoes
And grains
Storage Polysaccharides
• Glycogen = glucose polymer, for energy
storage in animals
• Branched molec.
• Stored in muscle
and liver of humans
and other vertebrates
Structural Polysaccharides
• Cellulose = linear unbranched polymer
– Major structural component of plant cell walls
– Differs from starch in its monomer linkage
– Cannot be digested by most organisms
Structural Polysaccharides
• Chitin = structural polysacch.; a polymer
of an amino sugar (nature’s plastic)
• Forms exoskeleton of Arthropods
• Found as cell walls in fungi
Lipids
Diverse group of organic compounds that are
insoluble in water
Includes animal fats,
plant oils, steroids,
phospholipids
Made of fatty acids
and glycerol
Fat
• Saturated
• All single bonds
• Solid at room temp
• Animal fats
• Unsaturated
• One or more double
bonds between carbons
• Liquid at room temp
• “Vegetable” or plant oils
Useful functions of fat
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Energy storage
More compact fuel reserve than carbo.
Cushions vital organs in mammals
Insulates against heat loss
Phospholipids
• Component of cell membranes (bilayer)
• 2 fatty acids & phosphate group
• Amphipathic behavior in water
Steroids
• Lipids w/ 4 fused carbon rings and various
functional groups
• Cholesterol important as precurser to other
steroids; and enhance membrane fluidity
Proteins
• Complex polymers of amino acids
• Abundant: make up 50% or more of dry wt
• Varied functions in cell: structure,
metabolism, transport, signaling,
movement, defense
• Each has unique 3-D shape
• Made of only 20 different amino acids
Amino Acid Structure
Nucleic Acids
• Deoxyribonucleic
Acid (DNA)
• Can replicate itself
and be passed from
one generation of
cells to the next
• Genes are segments
of DNA that code for
protein
• Ribonucleic Acid
(RNA)
• Functions as mediator
between genotype and
phenotype
• 3 functional forms
carry out “protein
synthesis”
Nucleic Acids
DNA, the Genetic Code
RNA the Trait Maker
Nucleotides: monomers of nucleic acids
• Pentose, a 5C sugar
• Nitrogen Base
• Phosphate