Chapter 5: Macromolecules
AP Biology
4 Classes of Large Biological Molecules
• Carbohydrates
• Lipids
• Proteins
• Nucleic Acids
Monomer vs. Polymer
• Most biological molecules are made from smaller subunits called monomers
• Polymers are formed by covalently bonded monomers
Building and Breaking of Polymers
1. Condensation Reaction
2.Hydrolysis
Diversity of Macromolecules
• Polymer arrangement can be compared to the alphabet
• Most living things use 40-50 most common monomers
• Arrangement is the most important aspect
Carbohydrates
• Sugars–Monosaccharides
–Disaccharides
–Polysaccharides
Monosaccharides
• Empirical Formula: CH2O (twice as many Hydrogen as Carbon)
• Commonly end in –ose– Literal meaning-”water of carbon”
• Examples: – Glucose– Fructose– Ribose
Monosaccharides
• Provide “ready” energy for living systems (easily digested)
• Three to nine carbons– Number of carbons dictates naming of simple
sugars– Pentose (Ribose) = 5 carbon – Hexose (Glucose) = 6 carbon
Monosaccharides
• Can be straight chain structures• Can form ring structures:
–Must have at least 5 carbons–In aqueous environment–Carbon -1 will attach to the oxygen of carbon-
5
• Both ring and straight chains will be in chemical equilibrium
•Ketose vs. Aldose
(Alpha- glucose)
Disaccharides
• Two monosaccharides joined together by glycosidic (covalent)
linkage– Glucose and Fructose = sucrose (table
sugar)(1-2 connection)– Glucose and Galactose= lactose (sugar
found in milk)– Two alpha glucose = maltose (malt
sugar)(1-6 connection)
Disaccharides:
• Energy transportation through out the body
Lactose
Polysaccharides
• Polymers of hundreds to a few thousand monosaccharides
• Can be used for energy storage as well as structure
Storage Polysaccharides: • Starch: consists entirely of
glucose
• Joined together by 1-4 glycosidic linkages
• Allows plants to stockpile E
Starch continued
• Most animals have enzymes that hydrolyze starch– Amylase- found in saliva and intestines-
produced by salivary glands and pancreas
Storage Polysaccharides:
• Glycogen• Branched version of starch that is
used by animals as glucose storage
• Located in the liver and muscle cells
• In humans, glycogen supply can last about 1 day
Structural Polysaccharides:
• Cellulose
• Most abundant organic compound on Earth
• Polymer of glucose, but differs in structure from starch
Starch vs. Cellulose
• Starch : 1-4 linkage of alpha glucose
Starch vs. Cellulose
• Cellulose: 1-4 linkage of beta glucose
• Interesting fact: humans do not have the enzyme to hydrolyze beta glucose linkages
• Alpha-glucose plays the role of energy– Compact, portable, easily broken down
• Beta –plays the role of roughage– Stable, structurally solid, hard to break down
Chitin: the “unused” structural polysaccharide
• Composes the exoskeleton of arthropods
• Chitin is soft but hardened with calcium carbonate
• Fungi also contains chitin
Starch
Cellulose
Glycogen
Lipids: • Non-polar organic compounds(can only be
dissolved in non-polar solvents)– hydrophobic
• Contain many carbon- hydrogen bonds
• Vital components of membranes
• Excellent for energy storage– Stored in large concentrations because they
do not attract water
• No monomer
Lipids:
• Fatty acids
• Waxes
• Triglycerides
• Fats and oils
• Phospholipids
• Steriods
Triacylglycerol:
• Triglycerides (fats)– Glycerol- contains three hydroxyl (alcohol)
functional groups– Three fatty acid chains(carboxylic ends with
long hydrocarbon chains(16-18))
• Ester linkage- condensation reaction between and alcohol group of the glycerol and carboxylic acid of the fatty acid
Fats(continued)
• Triacylglycerols(triglycerides)
• Solid at room temperature
• Saturated- all single covalent bonds- gives the fatty acids the tendency to lie in straight chains
• Tightly packed
• Butter, lard
• Animal fats
Fats(continued)
• Energy storage– Have double the energy storage capacity
compared to polysaccharides
Oils:
• Triacylglycerols(triglycerides)
• Liquid at room temperature
• Unsaturated- containing many double covalent bonds which creates rigid elbows or kinks in the fatty acid chain
• Loosely packed
• Olive oil, corn oil, peanut oil
• Plants and fish
Phospholipids:
• Chief component of biological membranes
• Amphipathic
• Structural molecules
Phospholipids (continued)
• Similar to triglycerides
• Composed of: – Nitrogen based compound– Phosphate(attaches to one of the three
alcohol groups of glycerol)– Glycerol– Two fatty acid chains(attached to glycerol)-
one of which contains a double bond giving it a kink
Steroids
• Four contiguous carbon rings with different functional groups
• Insoluble in water
Steroids (continued)
• Cholesterol- most abundant
• Hormones-chemical messengers– Estrogen– Progesterone– Testosterone-determines sex
Waxes:
• Long fatty acid chain (24-36 carbons) joined to long alcohol chain (24-36 carbons)– Ester linkage
• Water proofing- leaves, fruit, skin, hair
• Long term energy storage in some marine animals
Waxes (continued)
• Cornauba wax- palm wax
• Bees wax
• Lanolin- wools wax
Proteins
• 50% of the dry mass of most cells
Proteins(many functions of):• Enzymes-(cellular catalysts)speed up the
rate of the reaction with out being consumed
• Hormones- insulin• Storage- ovalbumin• Structure- collagen• Transport- hemoglobin• Receptor- clathrin • Contractile- actin and myosin• Defense- antibodies
Enzyme
• Acts as cellular catalyst: selectively speed up reaction w/o being consumed
• Example: Urease – Produced by bacteria
– Converts urea to ammonia and CO2
– 30,000 molecules of urea/ second– Would take 3 x 106 years if no enzyme
present
Enzyme Substrate Complex
(E + S = ES= E + P)
Most important Aspect of Proteins
• A proteins structure defines its function. –Change its structure and the
protein’s function will change
–Example: Troponin- used in muscle contraction
Amino Acid Monomers
• All proteins are made from 20 different Amino Acids
• Each amino acid is composed of:
–Central carbon
–Amine group
–Carboxylic acid
–R – group (side chains)
General Amino Acid Structure
Amino Acid Monomers
• Polymers of amino acids are called polypeptides–Joining of two amino acids =
peptide bond
–Dipeptide- chain of two amino acids
–Polypeptide- 150-750 amino acid residues
Amino Acid Polymerization
• Condensation reaction–Carboxylic acid of one amino
acid bonds to amine group of another
–H2O is a by product
4 Levels of Protein Structure
1. Primary (1˚)- linear structure of amino acids formed at ribosome
4 Levels of Protein Structure
2. Secondary (2˚)- alpha helices or beta pleated sheets– alpha helices- 3.6 amino acids per turn
• Amphipathic• Can stretch
– beta sheets- rigid structures held together by H- bonds
4 Levels of Protein Structure
3. Tertiary (3˚)- 3-d folding of proteins• Stabilized by four different interactions:
– Ionic bonds– Hydrogen bonds– Amphipathic interactions– Sulfur bridges(disulfide bonds)
• Motifs and Domains
4 Levels of Protein Structure
• 4o- quarternary structure: formation of the complete functional protein– Aggregation of the polypeptide subunits
Denaturation
• pH, salt concentration, and temperature can alter a protein’s shape– Temperature > 60oC cause the protein
ovalbumen to solidify
– Scrambling eggs
• Sometimes proteins can re-nature
Central Dogma of Biology
DNA RNA Protein
Nucleic Acids- largest of the biological molecules
• Determines the primary structure of a polypeptide–Gene: codes for an amino acid
sequence in a polypeptide
DNA
• Deoxyribonucleic Acid– Genetic material of all organisms and many
viruses– Contains information for making RNA
DNA
• Arranged in chromosomes that contain one long DNA molecule consisting of several hundred or thousand genes
• Nucleus bound
RNA
• Ribonucleic Acid– Responsible for the production of
proteins
– Genetic material of some viruses
RNA
• Smaller pieces of nucleic acids that directly make the proteins for the DNA codes(types of RNA):
1. Transfer (tRNA)
2. Messenger (mRNA)
3. Ribosomal (rRNA)
DNA and RNA
Nucleotides:
• Nucleic acid subunits, composed of: – 5 carbon sugar (pentose= deoxyribose or
ribose)– Phosphate group
• Sugar and phosphate group are linked by a phosphodiester bond (C-O-P-O-C)(5’- 3’)
– Nitrogenous base (ring structures)
Nitrogen Bases:
• 1. Pyrimidines: single ring nitrogenous bases– Uracil (U)- RNA only– Thymine (T)– Cytosine (C)
Nitrogen Bases:
• 2. Purines: double ring nitrogenous bases– Adenine (A)– Guanine (G)
DNA structure:
• Double helix:– Sugar and phosphate backbone– Nitrogenous base center
• Pyrimidines bond with purines (hydrogen bonds)• A-T (two hydrogen bonds)• C-G (three hydrogen bonds)
Which of the following lists ranks these molecules in the correct order by size?
• water, sucrose, glucose, protein
• protein, water, glucose, sucrose
• water, protein, sucrose, glucose
• protein, sucrose, glucose, water
• glucose, water, sucrose, protein
The lipids that form the main structural component of cell membranes are _____.
• triacylglycerols
• proteins
• cholesterol
• carbohydrates
• phospholipids
A shortage of phosphorus in the soil would make it especially difficult for a plant to manufacture _____.
• DNA
• proteins
• cellulose
• fatty acids
• sucrose
Ring Structure of Nitrogenous Bases
• Pyrimidine: 1 ring structure; includes cytosine, uracil, thymine
• Purine: 2 ring structure; includes guanine and adenine