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