Chapter 4 The Importance of Carbon
Key Terms: organic chemistry, isomer, hydrocarbon, and hydroxyl, carbonyl, carboxyl, amino groups
Many Molecules Are Very Small
Other Molecules Are Very Large
Called macromolecules
Four general types: carbohydrates, lipids, proteins, and nucleic acids
Isomers
Have same empirical formula
Atoms are arranged differently
Glucose and fructose are structural isomers
Glucose and galactose are stereoisomers
THE BUILDING BLOCKS OF ORGANISMS
The Chemistry of Carbon
Organic molecules contain carbon
Four electrons needed to fill outer orbital
Forms single, double and triple bonds with itself
Hydrocarbons: made of only carbon and hydrogen
FUNCTIONAL GROUPS (Table 4.1)
Area of molecule involved in chemical reactions
Hydroxyl
Hydrogen bonded to oxygen which is bonded to carbon skeleton
Hydroxyl is polar due to stronger O pulling on electron
Reason why sugars dissolve in water (water attracted to hydroxyl)
Carbonyl Group
Carbon double bonded to oxygen
If C=O is on end of moleculeà aldehyde
If C=O is anywhere else in moleculeàketone
Carboxyl Group (written as –COOH)
Carbon double bonded to oxygen and single bonded to hydroxyl
Carboxyl group has acidic properties due to ability to lose H+ ion
Amino Group
Nitrogen bonded to two hydrogens -NH2
Amino acids are the building block of proteins
Chapter 5 Macromolecules
Key Terms: polymer, dehydration synthesis, hydorlysis, carbohydrate, monosaccharide, disaccaride,
polysaccharide, starch vs. cellulose vs. glycogen, lipids, saturated vs. unsaturated fatty acids,
phospholipid, amino acid, primary, secondary, tertiary, quaternary, deoxyribonucleic acid,
ribonucleic acid
MACROMOLECULES
Structural or informational function
Many are polymers, repeating units bonded together
Building Macromolecules
Dehydration synthesis (reaction)
OH- removed from one subunit
H+ removed from other subunit
Molecule of water is removed as subunits are linked
Requires input of energy to assemble
Reaction carried out by enzymes
Hydrolysis reaction
Molecule of water added as subunits are broken apart
Reactions disassemble molecules to subunits, energy released
CARBOHYDRATES
Sugars Are Simple Carbohydrates
Contain C, H, O in 1:2:1 ratio
Function in energy storage
Important monosaccharides have six carbons
Empirical formula C6H12O6 or (CH2O)6
Are straight chains that form rings in water
Glucose is primary six carbon sugar
Transport Disaccharides
Protects sugar from being metabolized during transport
Are made of two monosaccharides linked together
Maltose = glucose + glucose
Sucrose = glucose + fructose
Lactose = glucose + galactose
Starches Are Chains of Sugars
Insoluble polymers called polysaccharides
Starches are polysaccharides made from glucose
Amylose is simplest form in plants
Carbon 1 of glucose bonds to carbon 4 of next glucose
Chains of maltose coil in water
Glycogen is branched form in animals
Long chain length
Great number of branches
Cellulose Is a Starch That Is Hard to Digest
Different orientation of glucose subunits (Fig. 5.7)
In starch all are on same side
In cellulose subunits alternate sides
Component of plant cell walls
Same subunits as amylose
Different bonds connect subunits
Cannot be degraded by enzyme that breaks amylose
Indigestible by most organisms, human dietary fiber
Degraded by certain bacteria and protists
LIPIDS
Fats
Are lipids that are insoluble due to nonpolar nature
Cannot form hydrogen bonds like water can
Fat molecules cluster together and exclude water
Oils and waxes are other kinds of lipids
Triglyceride = glycerol + three fatty acids
Fatty acids can be different from one another
Saturated fatty acids
Internal carbons have maximum number of hydrogens
Single bonds between carbons
Linear molecule is flat allowing it to stack into solid form
Unsaturated fatty acids
Internal carbons have fewer hydrogens
Double bonds between many carbons
Double bonds cause bends in linear molecule
Bends prevent molecules from stacking=LIQUID at room temp.
Polyunsaturated fats have more than one double bond
Humans and fats
Over consumption of saturated fats raises cholesterol levels
Natural unsaturated fats are healthier than saturated fats
They are also healthier than artificially hydrogenated fats
Efficient energy storage molecules
Many C-H bonds, saturated have more than unsaturated
9 kcal per gram fat, 4 kcal per gram carbohydrate
Conversion of consumed carbon molecules
Glucose available for immediate use
Disaccharides transported within organism
Starch and fat storage reserves
There Are Many Other Kinds of Lipids
Phospholipids comprise membranes
Composed of polar head and nonpolar tail
Form lipid bilayers
Polar head region faces outward (hydrophilic)
Nonpolar tails face inward (hydrophobic)
Steroids composed of four carbon rings
Terpenes form various long-chain pigments
Prostaglandins are modified fatty acids
Composed of two nonpolar tails attached to ring
Variety of biological functions
PROTEINS
Diverse Functions
Enzymes are globular and catalyze biological reactions
Fibrous proteins are structural
Peptides are short protein chemical messengers
Amino Acids Are the Building Blocks of Protein
Among first biological molecules to evolve
Amino, carboxyl, hydrogen bonded to central carbon
Identity conferred by variable R group
Five classes
Nonpolar
Polar, uncharged
Ionizable
Aromatic
Special function
Amino acids are linked together by peptide bonds
Proteins Are Chains of Amino Acids
Proteins composed of one or more polypeptides
Polypeptides are long chains of amino acids
Each protein has a unique, defined amino acid sequence
The Shape of Globular Proteins
Globular protein chains are folded up into complex shapes
Examine three dimensional structure with X-ray diffraction
Myoglobin first one examined
All internal amino acids are nonpolar
Hydrophobic interactions shove nonpolar molecules inside
Interactions result from hydrogen bonding
Possess four structural levels
Primary, secondary, tertiary, quateranary, structures
Primary structure
Specific amino acid sequence determined by gene's nucleotide sequence
Permits great diversity of proteins
Secondary structure
Side groups, CO and NH groups of main chain form hydrogen bonds
Two patterns of H bonding
Linking of two amino acids along chain forms alpha helix
Many parallel links across two chains form a pleated sheet
Tertiary structure
Protein's final folded shape
Spontaneous, driven by hydrophobic interactions with water
Nonpolar chains in close proximity exhibit van der Waal's forces
Allow very close fitting of nonpolar chains in protein interior
Single amino acid change can significantly disrupt fit
Quaternary structure
Combination of two or more polypeptide subunits
Composes functional unit of a protein
Denaturation
Protein shape altered with changes in pH, temperature, ion concentration
Protein becomes biologically inactive
Enzymes function only within a narrow environmental range
Proteins may return to natural shape
Large proteins rarely refold naturally
May do so with help of protein chaperone cofactors
NUCLEIC ACIDS
Cellular Information Storage Devices, the Hereditary Material
Deoxyribonucleic acid = DNA, master molecule found in nucleus
Ribonucleic acid = RNA, template copy sent to cytoplasm for synthesis of protein
Nucleotides Polymerize Forming Nucleic Acids
Chemical components
Five-carbon ribose or deoxyribose sugar
Phosphate group
Organic nitrogen-containing base
Phosphodiester bonds join sugars
Nitrogen base attached to sugar and protrudes from chain
Two kinds of organic bases
Purines: adenine (A), guanine (G)
Pyrimidines: cytosine (C), thymine (T) (DNA), uracil (U) (RNA)
Adenine also found in ATP, NAD and FAD
DNA
DNA forms double chains
Helix is a spiral staircase shape
Two intertwined DNA molecules form a double helix
Hydrogen bonds between bases hold chains together as duplex
Base pairing is specific and complementary
Adenine with thymine (DNA) or uracil (RNA)
Guanine with cytosine (DNA and RNA)
RNA provides copy of DNA from which proteins are synthesized
Chemical differences between RNA and DNA
RNA contains ribose sugar with hydroxyl at carbons 2 and 3
Uracil base in RNA, thymine in DNA
Single stranded helix under most circumstances
Which Came First, DNA or RNA
DNA stores information for protein synthesis
RNA is working copy of DNA master information
DNA protected by not being actively used to make protein
DNA evolved from RNA to protect the genetic information
Flow of genetic information: DNA RNA protein