Marvelous Macromolecules Chapter 5

Macromolecules Large molecules formed by joining smaller organic molecules Four Major Classes Carbohydrates Lipids Proteins Nucleic Acids

Polymers Many similar or identical building blocks linked by covalent bonds

Monomers Small units that join together to make polymers Connected by covalent bonds using a condensation (dehydration) reaction One monomer gives a hydroxyl group, the other gives a hydrogen to form water Process requires ENERGY and ENZYMES

Let’s Get Together… Yah, Yah, Yah

Breakdown Polymers are disassembled by hydrolysis The covalent bond between the monomers is broken splitting the hydrogen atom from the hydroxyl group Example – digestion breaks down polymers in your food into monomers your body can use

Breakin’ Up is Hard to Do…

Variety Each cell has thousands of different macromolecules These vary among cells of the same individual; they vary more among unrelated individuals in the same species; and vary even more in different species 40 to 50 monomers combine to make the huge variety of polymers

Carbohydrates Used for fuel (energy) and building material Includes sugars and their polymers Monosaccharides – simple sugars Disaccharides – double sugars (two monosaccharides joined by condensation reaction Polysaccharides – polymers of monosaccharides (many sugars joined together)

Monosaccharides Molecular formula is usually a multiple of CH 2 O Ex – Glucose C 6 H 12 O 6

Classification of Monosaccharides ALWAYS HAVE A CARBONYL GRP. and HYDROXYL GRPS. Location of carbonyl group If carbonyl is on end – aldose If carbonyl is in middle – ketose Number of carbons in backbone Six carbons – hexose Five carbons - pentose Three carbons - triose

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Characteristics of Monosaccharides Major fuel for cellular work – especially glucose – makes ATP In aqueous solutions – form rings Joined by glycosidic linkage through a dehydration reaction

Disaccharides Two monosaccharides joined together with a glycosidic linkage Maltose – formed when 2 glucose molecules are joined Sucrose (table sugar) formed by joining glucose and fructose Used to transport sugar in plants

Polysaccharides Polymers of sugar Can be hundreds to thousands of monosaccharides joined together by glycosidic linkages Used in energy storage then broken down as needed in the cell Also used to maintain structure in cells

Examples of Polysaccharides Starch – storage polysaccharide made entirely of glucose monomers Plants store starch in plastids Plants can use glucose stored in starch when they need energy or carbon When animals eat plants, they use the starch as an energy source Made of ALPHA glucose rings

Examples of Polysaccharides Cellulose Polymer of glucose monomers Made of BETA glucose rings Found in Cell Walls of plants (very tough) Animals can’t digest cellulose (passes through making digestion easier) Herbivores have special microbes in their stomachs that can digest cellulose (that’s why they can survive on only plants)

Examples of Polysaccharides Glycogen – polysaccharide of glucose used for sugar storage in ANIMALS Humans and vertebrates store glycogen in liver and muscles

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Examples of Polysaccharides Chitin Structural polysaccharide Used in exoskeletons of arthropods (insects, spiders, crustaceans) Forms the structural support for cell walls of fungi I crunch when I get stepped on because of Chitin

Lipids Hydrophobic molecules Nonpolar bonds making them have little or no affinity for water Store large amounts of energy Not “polymers”, but are large molecules made from smaller ones

Fats Made of glycerol (3 Carbons with hydroxyl attached) and 3 fatty acids (long carbon skeleton) Joined by ester linkage in dehydration reaction Used in energy storage, cushion organs, and for insulation

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Saturated Fats Fatty acids with no carbon-carbon double bonds Pack tightly together making SOLIDS at room temperature Most animal fats are saturated Eating too much can block arteries

Unsaturated Fats Fatty acid has one or more carbon- carbon double bonds Kinks from double bonds prevent tight packing Liquid at room temperature Plant and fish fats - oils

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Phospholipids Glycerol joins with 2 fatty acids and 1 phosphate group Phosphate group carries negative charge making heads that are hydrophilic Fatty acids are nonpolar, making tails that are hydrophobic Major components of cell membranes – phospholipid bilayer

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Steroids Carbon skeleton with four fused carbon rings Functional groups attached to rings make different steroids Cholesterol – used in animal cell membranes Precursor for all other steroids Many hormones are steroids

Proteins Function in Storage Transport Intercellular signals Movement Defense Structural Support Speeding up reactions (enzymes)

Polypeptide Polymer of amino acids (monomer) joined by peptide bonds One or more polypeptides come together to make protein Each protein has complex 3-D shape Amino Acid

Amino Acids Made of Hydrogen Carboxyl group Amino group R-group – varies from one amino acid to the next 20 amino acid monomers make thousands of proteins Joined together by dehydration reaction that removes hydroxyl group from one and amino group of another to make a peptide bond

Structure determines function Polypeptides must be folded into a unique shape before becoming proteins Order of amino acids determines shape Shape of protein determines its function Ex. – antibodies bind to foreign substances based on shape Folding occurs spontaneously

Levels of Protein Structure Primary – determined by unique sequence of amino acids Order of amino acids comes from DNA Changing primary structure can change the shape of a protein and could cause it to be inactive Ex – sickle cell caused by one amino acid change

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Levels of Protein Structure Secondary – comes from hydrogen bonds at regular intervals along the polypeptide backbone Alpha helix – coils Beta pleated sheets - folds

Levels of Protein Structure Tertiary – determined by interactions among R-groups on amino acids Hydrogen bonds Hydrophobic/hydrophilic interactions Van der Waals interactions Ionic bonds (charged R groups) Disulfide bridges between sulfhydryl groups of cysteine amino acids (stabilize structure)

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Levels of Protein Structure Quaternary – occurs with two or more polypeptide subunits Collagen – three polypeptides coiled like a rope – good for structure Hemoglobin – four polypeptide (two different types) – carries oxygen

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Changing Protein Structure Physical and Chemical conditions can change the shape of a protein pH Salt concentration Temperature Others Changes can disrupt secondary or tertiary structures Some proteins can return to original shape, but others are permanently denatured

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Nucleic Acids Polymers formed by joining Nucleotide monomers with phosphodiester linkages Store and transmit hereditary information Inherited from one cell to the next during cell division Program the primary structure of proteins through instructions in the genes of DNA Information travels from DNA  mRNA  protein Examples – DNA, RNA, ATP

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Nucleotides Made of 3 parts Pentose sugar (usually deoxyribose or ribose) Phosphate group Nitrogen Base Backbone – sugar and phosphate (phosphodiester link) Steps – Nitrogen base Make a Double Helix

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Nitrogen Bases Rings of Carbon and nitrogen Purines – two rings Adenine (A) Guanine (G) Pyrimidines – one ring Cytosine (C) Thymine (T) Uracil (U) A always pairs with T, C pairs with G in DNA Bases are connected in middle of ladder by HYDROGEN BONDS

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Polynucleotides Connect Sugar of one nucleotide to phosphate of next making a backbone Nitrogen bases in the middle vary from one organism to the next creating a unique sequence of DNA DNA creates proteins in cells therefore different organisms create different proteins based on the order of bases in DNA