Lecture 6
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Biological Molecules
Basic chemistry
Group of molecules especially important
Organic compounds: carbon compounds
Some books refer to organic compounds as being formed by living things: too simplistic
Biologically Important Molecules
Some molecules essential for life
W ater
Carbohydrates
Lipids
Proteins
Nucleic Acids
W ater
W ater important:
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Source of H+ and OH Solvent—important elements are carried by water through the biotic elements
 Polar–attracted to other water molecules
 High specific heat—can absorb large amount of heat without changing state
 Insulator
W ater
 Evaporative processes; increase in molecular motion, molecules escape, surface cools
 Sphere of hydration: formation of useful ions
 Heat distribution on a global scale: evaporating 1 g water absorbs 580 cal
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Carbon Compounds
Carbon: forms 4 covalent bonds
Orientation of atoms along C backbone
3 dimensional, not flat
Organic Compounds
Electron transfer
Functional group transfer
Bond rearrangement
Condensation: 2 molecules combine with covalent bonds
Cleavage: molecule splits into 2 smaller, hydrolysis (water splits, H, OH)
Organic Compounds
Carbon backbone
Single unit: monomer
Many units: polymer
Many molecules are polymers
Organic Compounds
 Functional groups: groups of atoms attached to C backbone
 Solubility
 Reactivity
 Binding sites
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Carbohydrates
Most abundant organic
Simple or complex
Simple energy source for cells
Stored energy
Cell wall components
 W ater soluble
 C, H, O: 1:2:1 ratio
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Carbohydrates
Building block: simple sugar—saccharide
Monosaccharide: 1 sugar unit
Glucose: primary energy source
Short chains: few repeating units—disachharide, sucrose
Oligosaccharide: with protein, found on cell membranes
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Carbohydrates
Complex carbohydrates: many unnits covalently bonded
Starch
Cellulose
Glycogen
Chitin
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Lipids
C, H, O: not 1:2:1 ratio
Fats
Many uses, include high density energy source (9 cal/g vs 4 cal/g)
Common lipids
 Glycerides
 Steroids
 Phospholipids
Lipids
 Glyceride: glycerol (head) and fatty acids (tails)
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Saturated: no double bonds
Unsaturated: double bonds
Polyunsaturated: many double bonds
Lipids
Steroids
4 carbon rings
Many different side chains
Hormones
Cell components, especially cell membrane
Proteins
C, H, O , N, S
Building blocks: amino acids
3+: polypeptide
Amino group and acid groups
20 different amino acids, great variety of proteins
Proteins
Primary structure: aa sequence
Secondary structure: H bonds form spirals or pleats
Tertiary Structure: folding of chains (proteins)
Tertiary structure: 2 or more chains joined (subunits)
Proteins
Krogh, p. 48, Table 3.2
Lists:
 T ypes—enzymes, hormones, etc
 Roles—biochemical catalysts, messengers
 Examples—am ylase (lab), insulin
Proteins
 Functional groups essential
 Shape is essential
 Alter shape, alter function
 Heat
 pH
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Nucleotides and Nucleic Acids
C, H, O , N, P
Chemical energy carriers
Storage and transfer of genetic information and protein formation
Nucleotide
 Phosphate group
 Sugar group
 Nitrogenous base
 DNA is like a cookbook
Nucleic Acids
 Each recipe (“gene”) calls for the production of a particular protein
 RNA is involved in bringing DNA’s instructions to the site of protein synthesis