Marvelous Macromolecules

Chapter 5

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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 CH2O Ex – Glucose C6H12O6

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 fungiI crunch when I get I crunch when I get stepped on because ofstepped on because ofChitinChitin

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

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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 QuickTime™ and a

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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)

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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 AcidAmino AcidAmino AcidAmino Acid Amino AcidAmino 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

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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

DNAmRNAprotein 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