• Molecules
• building blocks of life
• four major types of biological macromolecules
• carbohydrates
• lipids
• proteins
• nucleic acids
• we’ll return to these later
• consist of 2 or more atoms bound together
• all small in comparison to what we can see
• some are "small"
• others are "gigantic"
• thousands of atoms
• organized into hundreds of smaller molecules linked into long chains
• almost always synthesized by living things
• organic molecules
• compounds that are synthesized by cells and contain carbon
• carbon
• plays central role in organic molecules
• involved in almost all molecules made by cells
• unparalleled in its ability to form large, diverse molecules
• containing compounds most common substances in living organisms, other than water

Carbon plays central role in organic molecules

• carbon
• forms 4 covalent bonds
• single, double, or triple covalent bonds w/ other carbon atoms
• forms variety of molecular shapes
• combines with hydrogen to form hydrocarbons
• bonds with H, N, O, S
• forms isomers
• Chemistry of carbon
• forms 4 covalent bonds
• outer electron shell can hold 8 electrons
• contains only 4 electrons in its outer shell
• can form up to 4 covalent bonds (8-4=4, or 4+4=8)
• can form single, double, or triple covalent bonds with other carbon atoms
• can readily form chains of carbon atoms
• forms variety of molecular shapes
• carbon chains, can be
• straight
• branched
• closed into rings
• can form greater variety of molecules than any other element
• combines w/hydrogen, forms hydrocarbons
• organic molecules consisting only of C and H
• C - H covalent bonds store a lot of energy
• hydrocarbons make good fuels
• most biologically important molecules are not hydrocarbons
• carbon forms bonds with H, N, O, S
• forming many other biologically significant molecules
• including biologically important functional groups
• forms isomers
• alternative forms of a molecule which have same empirical formula but atoms are arranged in different way
• types of isomers
• structural isomers
• stereoisomers (geometric)
• we’ll return to this later

The construction of biologically important organic molecules

• any organic molecule can be thought of as a carbon-based core to which specific groups of atoms with specific chemical properties are attached
• carbon skeleton or core
• repeating carbons to which specific groups of atoms with definite chemical properties are attached
• represented in diagrams by R =,"remainder"
• functional groups
• groups of atoms w/specific chemical properties attached to C core
• retain their chemical properties no matter where they occur
• most compounds in cells contain two or more different functional groups
• every amino acid contains at least two functional groups
• an amino group
• a carboxyl group

The construction of biologically important organic molecules

• functional groups
• there are several biologically important functional groups
• hydroxyl (R-OH)
• carbonyl (R-[C=O]-H, or (R-[C=O]-R)
• carboxyl (R-[C=O]-OH, R-COOH)
• amino (R-NH₂)
• phosphate (R-O-P[=O]-OH]-OH)
• sulfhydryl (R-SH)
• methyl (R-CH₃)

Making & Breaking Macromolecules

• Biological macromolecules
• polymers
• made up of repeating subunits (monomers)
• four categories
• each category contains different subunits
• assembled in the same way
• dehydration synthesis
• disassembled in the same way
• hydrolysis
• dehydration synthesis (condensation reaction)
• macromolecule is assembled by removing an –OH group from one subunit and an H from other subunit
• constitutes removal of molecule of H₂O
• also called "water-losing" reaction
• energy is required to break chemical bonds when water is extracted
• cells must supply energy to assemble macromolecules

Making & Breaking Macromolecules

• dehydration synthesis
• anabolic reactions
• reactions in which macromolecules are built from smaller subunits, requires
• energy
• catalysis
• process of positioning (reacting substances must be held close together)
• process of stressing bonds (correct chemical bonds be stressed and broken)
• these processes carried out by a special class of proteins known as enzymes
• Cells also disassemble macromolecules into their constituent subunits by performing
• catabolic reactions
• reactions in which macromolecules are synthesized by disassembling other macromolecules into their constituent parts
• energy released
• are essentially the reverse of dehydration synthesis, called
• hydrolysis (digestion)
• hydrolysis (digestion)
• macromolecules created by disassembling other macromolecules into their constituent parts
• by adding an –OH group to form one subunit and an H to form other subunit
• constitutes addition a molecule of water (H₂O) for every macromolecule that is disassembled
• energy is released when energy-storing bonds are broken

The 4 major classes of biological macromolecules

• carbohydrates
• monosaccharides
• lipids
• glycerol
• fatty acids
• proteins
• amino acids
• nucleic acids (DNA, RNA)
• nucleotide

Polymers are large molecules consisting of long chains of repeating subunits

Biological macromolecules have certain functions in organisms

• carbohydrates
• loosely defined group
• molecules that contain C, H, and O in molecular ratio of 1:2:1, with empirical formula of (CH₂O)_n
• functions
• energy storage molecules
• structural elements

• named based on number of sugar units they contain
• monosaccharides
• one sugar unit (mono-)
• disaccharides
• two sugar units (di-)
• polysaccharides
• many sugar units (poly-)
• monosaccharides
• structure
• simplest carbohydrate
• is a single sugar unit
• contain 3 to 7 carbons (typically 6-7)
• empirical formula, C₆H₁₂O₆ or (CH₂O)₆
• exist in straight chain form or in rings
• in water solutions they almost always form rings
• function
• play central role in energy storage
• glucose most important
• examples
• glucose
• fructose
• glyceraldehyde phosphate

• disaccharides
• structure
• "double sugars"
• two monosaccharides joined by a covalent bond
• function
• play a role in the transport of sugars
• examples
• sucrose
• lactose
• polysaccharides
• structure
• many monosaccharides put together
• precise number of sugar units varies
• chains can be single or branched
• function
• storage of energy
• structural
• functions
• storage of energy
• starch = formed in plants, consists of glucose units
• glycogen = formed in animals, consists of glucose units
• functions
• structural
• cellulose = formed in plants, consists of glucose units, component of plant cell walls
• chitin = formed in insects, fungi and certain other organisms, consists of glucosamine units (contains N)
• glycocalyx = coating or layer of oligosaccharides on outside of an animal cell
• glycoproteins = protein with covalently attached carbohydrates
• glycolipids = lipid with polysaccharide attached
• peptidoglycan = modified protein or peptide possessing an attached carbohydrate, bacterial cell walls
• examples
• starch = amylose, amylopectin
• glycogen
• cellulose
• chitin
• sugar isomers
• more than one sugar can have same empirical formula but different arrangement of their atoms
• these structural differences can account for functional differences between isomers
• two types of isomers
• structural isomers
• stereoisomers (geometric isomers)
• structural isomers
• identical chemical groups bonded to different carbon atoms
• example: glucose and fructose
• stereoisomers (geometric isomers)
• identical chemical groups bonded to same carbon atoms but in different orientations
• example: glucose and galactose

• Lipids
• loosely defined group
• molecules with one main characteristic
• insoluble in water
• main type
• fats (triglycerides or triacylglycerols)
• other types
• phospholipids
• steroids
• waxes
• fats (triglycerides or triacylglycerols)
• structure = glycerol + 3 fatty acids
• glycerol
• 3-carbon alcohol with each carbon bearing a hydroxyl group
• fatty acids
• long hydrocarbon chains ending in a carboxyl group
• functions
• energy storage
• efficient energy storage molecules because of their high concentrations of C-H bonds
• insulation
• cushioning
• saturated and unsaturated fats
• based on absence/ presence of double bonds between carbon atoms and number of hydrogen atoms

• saturated fats
• all internal C atoms are bound to at least two other C atoms
• results in maximum number of H atoms
• said to be saturated
• fatty acid chains tend to be straight and fit close together
• most are solid at room temperature
• such as butter

• unsaturated fats
• double bonds between one pair of C atoms
• results in less than maximum number of hydrogen atoms
• because double bonds replace some of hydrogen atoms
• said to be unsaturated
• most are liquid at room temperature
• such as oil

• polyunsaturated fats
• double bonds between 2+ pairs of C atoms
• have low melting points because fatty acid chains can’t closely align
• double bonds cause kinks
• most are liquid at room temperature
• such as corn oil

• fats (triglycerides or triacylglycerols)
• other types and their function
• phospholipids
• modified fats with two fatty acid chains rather than three
• one fatty acid chains is replaced by a phosphate group
• has hydrophillic head, hydrophobic tail
• structure of cell membranes = phospholipid bilayer
• waxes
• waterproof coating on leaves, bird feathers, mammalian skin, arthropod exoskeleton

• steroids = lipids composed of 4 carbon rings
• hormones
• regulatory
• cholesterol
• found in eukaryotic cell membrane
• bile salts (emulsify fats)

• proteins
• perform many functions
• are all polymers of only 20 amino acids
• structure
• amino acids joined by peptide bonds
• levels of structure
• functions
• types of

• structure
• made up of repeating subunits, amino acids
• joined by peptide bonds
• molecules containing
• an amino group (-NH₂)
• a carboxyl group (-COOH)
• unique chemical properties determined by nature of the side group

• amino acids
• grouped into 5 chemical classes based on their side groups
• nonpolar
• polar
• ionizable
• aromatic (rings)
• special function

• peptide bonds join amino acids together
• covalent
• has partial double bond characteristic
• is stiff
• amino acids are not free to rotate around C-N linkage
• levels of structure
• primary
• secondary
• motifs
• tertiary
• domains
• quaternary
• levels of structure
• primary
• result from specific amino acid sequence
• one dimensional
• secondary
• results from hydrogen bonding between individual amino acids
• two dimensional
• two patterns of hydrogen bonding
• b pleated sheets
• a helix

• tertiary
• final folded shape of protein
• globular, 3-D
• results from hydrophobic interactions with water
• domains
• different sections of a protein fold into a structurally independent globular protein like knots on a rope
• quaternary
• two or more polypeptide chains associate to form a functional protein

• levels of structure
• how proteins fold and unfold
• chaperone proteins
• help protein fold correctly
• denaturation
• process by which a protein changes its shape or unfolds
• chaperone proteins
• help protein fold correctly
• rescue proteins caught in a wrongly folded state giving them another chance to fold correctly
• chaperone deficiency may play role in disease
• how proteins fold and unfold
• denaturation
• process by which a protein changes its shape (secondary & + structure) or even unfolds when its "tolerance range" for some factor is exceeded
• results from breaking hydrogen bonds, disrupting polar - nonpolar interactions
• denaturation can be caused by
• heats
• acids
• bases
• salts
• proteins
• functions
• regulation
• structural
• contractile
• transport
• energy storage
• defense
• osmotic regulation
• functions
• regulation
• enzymes catalysts in metabolic pathways
• hormones
• in gene expression
• structural
• cell membranes
• cell cytoskeleton components
• collagen
• elastin
• keratin
• contractile
• muscle fibers
• transport
• hemoglobin
• myoglobin
• energy storage
• egg albumin
• plant seeds
• defense
• antibodies
• osmotic regulation
• globulins
• proteins
• types of
• dipeptides
• two amino acids
• polypeptides
• many amino acids
• fibrous
• globular

• nucleic acids
• information storage devices of cells
• long polymers of repeating subunits called nucleotides
• two types
• DNA
• deoxyribonucleic acid
• RNA
• ribonucleic acid
• genetic material organisms inherit from their parents consists of DNA
• within DNA are genes
• specific stretches of that program amino acid sequences of proteins
• nucleotides
• consist of three components
• five-carbon sugar
• phosphate group
• nitrogenous base
• organic nitrogen-containing base
• consist of three components
• five-carbon sugar
• ribose in RNA
• deoxyribose in DNA

• phosphate group

• nitrogenous base
• two types of organic bases occur in nucleotides
• purines
• pyrimidines

• two types of organic bases occur in nucleotides
• purines = large, double-ringed molecules
• adenine (A) - found in RNA and DNA
• guanine (G) - found in RNA and DNA
• pyrimidines = smaller, single-ringed molecules
• cytosine (C) – found in RNA and DNA
• thymine (T) – found in DNA only
• uracil (U) – found in RNA only

• nucleotides
• nucleotides are linked together with phosphodiester bonds
• result when phosphate group of one nucleotide binds to hydroxyl group of another nucleotide, releasing water
• creates a "sugar-phosphate" backbone

• nucleic acids
• types of and functions
• RNA
• DNA
• ATP and other high energy molecules
• types of and functions
• RNA
• usually consists of a single polynucleotide strand
• serves as an intermediary for DNA
• DNA’s information is transcribed into RNA
• interprets genetic blueprint through protein synthesis
• transcribing DNA message into a chemically different molecule
• allows cell to tell which is original information storage molecule and which is transcript
• 3 types
• mRNA = messenger RNA
• tRNA = transfer RNA
• rRNA = ribosomal RNA
• nucleic acids
• types of and functions
• DNA is a double helix
• two polynucleotides wrap around each other
• nitrogenous bases protrude from two sugar-phosphate backbones into center of helix where they pair
• adenine (A) with thymine (T)
• cytosine (C) with guanine (G)
• forms genetic blueprint in genes or chromosomes
• organisms encode information specifying amino acid sequences of their proteins as sequences of nucleotides
• ATP and other high energy molecules
• nucleotides play critical roles in molecules which serve as the energy currency of the cell
• ATP = adenosine triphosphate
• NAD⁺ = nicotinamide adenine dinucleotide
• FAD⁺ = flavin adenine dinucleotide

• discovering the structure of DNA
• x-ray crystallographer Rosalind Franklin
• in 1952, made image of DNA that showed a distinctive X-shape
• indication that DNA had twisted or helical structure
• in 1953, estranged co-worker (Wilkins) gave the image to James Watson (of Watson & Crick fame) without her knowledge (more of her data was subsequently passed to them as well)
• Watson & Crick
• in March 1953, announced they had solved DNA puzzle, produced model showing helical structure
• won 1962 Nobel Prize for Physiology and Medicine (along with Wilkins) for discovery of DNA’s structure
• Franklin was never mentioned
• Franklin died in 1958 at age 37 from ovarian cancer

The End.