Chapter 5 Macromolecules

Chapter 5 Macromolecules • Gen Information A. Macromolecules are polymers 1. Polymers – large molecules consisting of many identical subunits connected together. 2. Monomers – subunit molecule of a polymer. 3. Types of Macromolecules A. Carbohydrates B. Lipids C. Proteins D. Nucleic Acids

B. Formation of Macromolecules 1. Condensation reaction/dehydration reaction – monomers are covalently linked, producing net removal of a water molecule 2. Process requires energy 3. Process requires enzymes C. Breakdown of Macromolecules 1. Hydrolysis – a reaction process that breaks covalent bonds between monomers by the addition of water molecules

II. Carbohydrates A. Organic molecules made of sugars and their polymers which are formed by condensation reactions B. Monosaccharides 1. simple sugar in which C, H, and O occur in the ratio of (CH2O) 2. monosaccharides are major nutrients for cells. 3. glucose can be produced by photosynthetic organisms. 4 . store energy in their chemical bonds which is released by cellular respiration

5. can be incorporated as monomers into disaccharides and polysaccharides. 6. Characteristics of a sugar a. an –OH group is attached to each carbon except one, which is double bonded to an oxygen(carbonyl); can be a ketone or aldehyde b. size of the carbon backbone varies from 3 to 7 carbons. 1. most common monosaccharides: glyceraldehyde – 3 Carbons – triose ribose – 5 Carbons – pentose glucose – 6 Carbons – hexose

c. spatial arrangement around asymmetric carbons may vary, the small difference between isomers affects molecular shape which gives these molecules distinctive biochemical properties. d. many monosaccharides form rings in aqueous solutions. C. Disaccharides 1. a double sugar that consist of two monosaccharides joined by glycosidic linkage glycosidic linkage – covalent bond formed by a condensation reaction between 2 sugars monomers

2. Common Disaccharides Maltose – glucose + glucose – important in brewing beer Lactose – glucose + galactose – sugar present in milk Sucrose – glucose + fructose – common table sugar D. Polysaccharides 1. polymers of thousands of monosaccharides 2. are formed by linking monomers in enzyme mediated condensation reactions

3. Types of Polysaccharides a.energy storage polysaccharides 1. starch – a storage polysaccharide in plants; stored as granules within plant organelles called plastids a. types 1. amylose – the simplest form 2. amylopectin – branched polymer b. most animals have digestive enzymes to hydrolyze starch c. major sources in humans diet are potatoes and grains

2. glycogen – glucose polymer that is a storage polysaccharide in animals. - stored in the muscle and liver of humans and other vertebrates b. structural support polysaccharides 1. cellulose – a major structural component of plant cell walls a. it reinforces plant cell walls b. cellulose can’t be digested by humans because they lack the enzyme that can hydrolyze the linkage 2. chitin – forms exoskeleton of arthropods and can be found in the cell walls of some fungi

III. Lipids A. Diverse group of organic compounds that are insoluble in water, but will dissolve in non-polar solvents B. Fats – macromolecules constructed from: 1. glycerol – a 3-carbon alcohol 2. fatty acid (carboxylic acid) a. composed of a carboxyl group(-COOH) at one end(“head”) and an attached hydrocarbon chain (“tail”) b. hydrocarbon chain has a long carbon backbone with an even number of carbon atoms

c. non-polar C-H bonds make the chain hydophobic and not water soluble d. triglyceride=a fat composed of three fatty acids bonded to one glycerol by ester linkage – bond formed between hydroxyl group and a carboxyl group 3. Characteristics of fats a. fats are insoluble in water b. the source of variation among fat molecules is the fatty acid composition c. fatty acids may vary in the number and location of carbon-to-carbon double bonds

d. characteristics of saturated fats 1. no double bonds between carbons in fatty acid tail 2. carbon backbone of fatty acid is bonded to maximum number of hydrogen (saturated with hydrogen) 3. usually solid at room temperature 4. most are animal fats (bacon grease, butter, lard)

e. characteristics of unsaturated fats 1. at least one double bonds between carbon in fatty acid tail 2. tail kinds, so molecules do not pack closely enough to solidify at room temperature 3. most are plant fats (corn, peanut and olive oil) *** Many commercially prepared food products, unsaturated fats are artificially hydrogenated to to prevent them from separating out as oil (peanut butter and margarine)

f. useful functions of fats 1. energy storage 2. more compact fuel reservoir than carbohydrate 3. cushions vital organs in mammals (kidneys) 4. insulates against heat loss in some mammals (whales and seals)

C. Phospholipids – glycerol, 2 fatty acids and a phosphate 1. has hydrocarbon tails that are hydrophobic and the polar head (phosphate) that is hydrophilic. 2. they cluster in water as their hydrophobic portions turn away from water and the hydrophilic heads arrange themselves facing toward the water *micelle – cluster of phospholipids 3. are major constituents of cell membranes; phospholipids form a bi-layer held together by hydrophobic interactions

D. Steroids – lipids which have four fused carbon rings with various functional groups attached 1. Cholesterol a. is the precursor to many other steroids including vertebrate sex hormones and bile acids b. is a common component of animal cell membranes c. can contribute to atherosclerosis E. Waxes – long chain fatty acids tightly packed and linked to long chain alcohols or carbon rings 1. covers the cuticles of plant, restricting water loss and fends off certain parasites 2. waxy secretions protect, lubricate, and impart pliability to hair and skin 3. birds secrete waxes to waterproof feathers 4. bees use beeswax to make honeycombs

IV. Proteins A. Gen Information 1. A macromolecule that consist of one or more polypeptide chains folded and coiled into specific conformations a. polypeptide – polymers of amino acids that are arranged in a specific linear sequence and are linked by peptide bonds. B. Protein functions 1. structural support and storage 2. transport(hemoglobin) and signaling(chemical messengers) 3. cellular response to chemical stimuli(receptor protein) 4. movement(contractile protein) 5. defense against foreign substances and disease-causing organisms(antibodies) 6. catalysis of biochemical reactions(enzymes)

C. Amino acids – building block molecule of a protein, most consist of an asymmetric carbon (alpha carbon) covalently bonded to a Hydrogen, carboxyl, amino group, and a variable R group(side chain) 1. Amino acids can exist in 3 ionic states a. cation –as the pH decreases from the dipolar ion b. dipolar ion – as the pH increase from the cation or decrease from the anion c. anion – as the pH increases from the dipolar ion 2. Properties of the side chains – amino acids with non-polar side groups are less soluble in water; amino acids with polar side groups are soluble in water

D. Polypeptide chains – polymers that are formed when amino acid monomers are linked by peptide bonds 1. peptide bonds – covalent bonds formed by condensation reaction that links the carboxyl group of on amino acid to amino group of another 2. the chain has polarity with an amino group on one end(n-terminus) and the carboxyl group on the other end(c-terminus) 3. the chain has a backbone of the repeating sequence -N-C-C-N-C-C

E. Protein Conformation – 3-dimensional shape that gives protein its functions 1. native conformation – functions of protein under normal biological conditions a. enables a protein to recognize and bind specifically with another molecule (enzyme/substrate) b. is produced when a newly formed polypeptide chain coils and folds spontaneously

F. 4 Levels of Protein Structure 1. Primary Structure – unique sequence of amino acids in a protein a. determined by genes; slight genetic changes can affect the protein’s function(sickle cell) b. can be sequenced in the lab 2. Secondary Structure – regular, repeated coiling and folding of a protein’s polypeptide backbone a. stabilized by hydrogen bonds between peptide linkages

b. types of secondary protein structure 1. alpha helix – a helical coil stabilized by hydrogen bonding between every 4th peptide bond; found in fibrous protein(alpha keratin and collagen) 2. Beta pleated sheet – a sheet of un- parallel chains folded into an accordion pleats; parallel regions are held together by either intrachain or interchainhydrogen bonds

3. Tertiary Structure – irregular contortions of a protein due to bonding between side chains, third level of protein structure superimposed upon primary and secondary structure a. Types of bonds that make tertiary structures 1. weak interactions that help stabilize the protein shape include: hydrogen bonding between polar side chains; ionic bonds charged side chains; hydrophobic interactions between non-polar side chains

2. covalent linkages – disulfide bridges form between monomers brought together by folding of the protein 4. Quaternary Structure – results from the interactions among several polypeptides(subunits) in a single protein (examples- collagen and hemoglobin) G. Problems That can Change Protein’s Shape 1. Denaturation- alters a protein’s native conformation and and biological activity

a. ways protein can be denatured 1. transfer to an organic solvent 2. chemical substance that disrupts the bonds 3. excessive heat 2. Protein –folding problems

Nucleic Acids – transmits hereditary information A. Two types of nucleic acids 1. DNA a. contains coded information for all cell activity b. contains information for its own replication c. is copied and passed from 1 generation to another d. in eukaryotic cells is found in the nucleus e. contains instruction for protein synthesis 2. RNA a. functions in the synthesis of proteins coded by DNA b. ribosomes – sites of protein synthesis c. mRNA carries encoded genetic message to ribosomes d. genetic information flows from DNA to RNA to proteins

Chapter 5 Macromolecules