04 Macromolecules-1

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MCB 181R Sec 3/4H

(August 24 September 16)

The Science of Biology

Review of Chemistry

Organic Chemistry Macromolecules

Cells

Functions of Cell Membranes Review for Exam 1

Exam 1 -- Study Sessions 1-6 (September 16)

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(polynucleotides)

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Polymers are made by condensation (dehydration)

reactions and broken down by hydrolysis.

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Todaywe will consider the four classes oflarge

(macro) molecules found in allliving things.

Proteins provide structure, catalysis, regulation,movement, transport, and recognition in cells.

Polysaccharides are used for energy storage and

building materials.

Nucleic Acids store and transmit hereditary

information.

Lipids are diverse hydrophobic molecules which

function as hormones (steroids), as part of

biological membranes (phospholipids) and in

energy storage (fats).

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Proteins provide structure, catalysis, regulation,

movement, transport, and recognition in cells.

Aprotein consists of one or more polypeptide

chains folded into a specific conformation (shape).

Apolypeptide is a long chain or polymer of amino

acids connected in a specific sequence.

The information that specifies the sequences of

amino acids in the thousands of different kinds of

proteins in cells is stored in genes (DNA ofchromosomes).

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Cells build proteins with 20 different amino acids!

All amino acids have an

amino and a carboxyl

group linked to an alpha

() carbon atom.

The 20 different amino

acids have the same

general structure but

have different R groups(side chains) that impart

unique characteristics.

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In neutral conditions (pH 7), the amino and carboxyl

groups ionize to NH3+ and COO, respectively

this helps amino acids stay in solution and makes

them more reactive.

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The twenty amino acids of proteins are grouped

according to chemical properties of the side chain!


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(hydrophobic)

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*

(hydrophylic)

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*has a special role


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(hydrophylic)

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A protein (one or more polypeptides) consists of

amino acids linked together by peptide bonds!

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Within the polypeptide, the peptide bonds form a backbone with threekey characteristics:

R-group orientation: Side chains can interact with each other or water.

Directionality: Free amino group, on the left, is called the N-terminus.

Free carboxyl group, on the right, is called the C-terminus.

Flexibility: Single bonds on either side of the peptide bond can rotate,making the entire structure flexible.

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A functional protein has up to four levels of structure:

Primary and Secondary structures

Primary structure refersto the sequence or order

of the 20 different amino

acids in the polypeptide

chain.

As a result of hydrogen

bonding, the polypeptide

can coil ( helix) or fold

(-pleated sheet) to give

the secondary structure.

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Tertiary structure

Polar, nonpolar and ionic side chains of the variousamino acids can interact to superimpose a threedimensional shape on the polypeptide referred to asthe tertiary structure.

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A functional protein has up to four levels of

structure!

Polar, nonpolar and ionic side chains of the variousamino acids can interact to superimpose a threedimensional shape on the polypeptide referred to asthe tertiary structure.

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Hydrophobic and van der Waals interactions within

proteins

Hydrophobic Interactions: interactions of nonpolar Rgroups within protein in the presence of a polar

solvent (water). Hydrophobic side chains tend to form

globular masses. Weaker than hydrogen bonds.

van der Waals Interactions: interactions of electrons

of nonpolar R groups within protein. Weakest type of

interactions. But a large number of van der Waals

interactions tend to occur within a polypeptide withmany hydrophobic residues. Many interactions add

up to a significant increase in stability of the

polypeptide.

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A functional protein has up to four levels of structure!

Quaternary structure isthe overall protein

structure resulting from

aggregation of more than

one polypeptide. The

hemoglobin protein in

human red blood cells

consists of four

polypeptides.

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Primary Structure: Amino acid monomers are joined,

Figure 3.7 The Four Levels ofProtein Structure

Amino acid monomers Peptide bond

forming polypeptide chains.


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Secondary Structure: Polypeptide chains may form a helices

-Helix

Hydrogen bond


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-Pleated sheet

or -pleated sheets.

Hydrogen bond


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Tertiary Structure: Polypeptides fold, forming specific shapes.

Folds are stabilized by bonds and disulfide bridges.

-Pleated sheet

-Helix

Hydrogen bond

Disulfide bridge


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Quaternary Structure: Twoor more polypeptides assemble to form larger protein

molecules. The hypothetical molecule here is a tetramer, made up of four polypeptide

subunits.


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One-minute-break slide!

My office hours:Tues & Thurs 1-2 pm

Wed 9-11 am

or by appointment.Location: Marley 441D

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building materials.


information.





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Polysaccharides (carbohydrates) are used for

energy storage and building materials.

Apolysaccharide consists of a long chain orpolymer of monosaccharides (simple sugars) such

as glucose.

Cells make polysaccharides by using catalyticproteins called enzymes which perform a

condensation (dehydration) reaction to link simple

sugars together.

Polysaccharides are carbohydrates that contain

carbon, hydrogen and oxygen in the proportion

CH2O.

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Sugars exist inlinear and ring forms


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Monosaccharides Are Simple Sugars

These hexoseshave the same

molecular formulaas glucose(C6H12O6), but theyhave a differentarrangement ofatoms resulting inisomerswithdifferent

properties.

Glyceraldehyde isthe smallestmonosaccharideand exists only as alinear-chain form. Ribose and

deoxyribose eachhave five carbons,but they have verydifferent chemicalproperties andbiological roles.


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Cells build polysaccharides bylinking

monosaccharides together by a glycosidic bond!

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Cellulose, starch and glycogen are all

polysaccharides made of glucose!

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Cellulose, starch and glycogen are all

polysaccharides made of glucose!

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Plant cellwall Starch granules in plant

cells

Glycogen deposits in

humanliver


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building materials.


information.





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Nucleic acids store and transmit hereditary

information!

Nucleic acids consists of a long chain or polymer

of nucleotides.

There are two types of nucleic acids:Deoxyribonucleic Acid (DNA) and Ribonucleic Acid

(RNA)

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A nucleotide consist of a nitrogen-containing base,

a pentose sugar and one or more phosphate

groups!

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Nucleotides are joined by a dehydration

(condensation) reaction to form a phosphodiester

linkage.

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The sugar-phosphatebackbone of a nucleic acidis directionalone end hasan unlinked 5carbon, andthe other end has anunlinked 3carbon.

The nucleotide sequence iswritten in the 5p 3direction. This reflects thesequence in whichnucleotides are added to agrowing molecule.

This nucleotide sequencecomprises the nucleic acidsprimary structure.

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A DNA molecule consists of two polynucleotide strands held

together by hydrogen bonds between the nitrogenous

bases!

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The secondary structure ofDNA is a double helix.

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building materials.


information.





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Fats store large amounts of energy!

Fats (triglycerides) are made from two kinds of molecules (glycerol and

fatty acids) by a condensation (dehydration reaction).

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These fatty acid chains

can have different

hydrocarbon chain

length or structure,

some saturated and

some unsaturated.


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Fatty acids vary inlength and they may be saturated or

unsaturated!

Saturated fatty acids: nodouble bonds betweencarbonsit is saturatedwith H atoms.

Unsaturated fatty acids:some double bonds incarbon chain.

monounsaturated: one

double bond

polyunsaturated: morethan one

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Phospholipids are building blocks of cell membranes!

Phospholipids have 2rather than 3 fatty acidswith a phosphate group onthe third position on theglycerol molecule.

Additionally, small chargedor polar molecules (e.g.choline) are linked to thephosphate group.

The resulting phospholipid

is amphipathic with bothhydrophobic andhydrophilic portion of themolecule.

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Phospholipids spontaneously form a bilayer

structure inwater

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Phospholipids spontaneously form a bilayer structure inwater with their hydrophobic hydrocarbon tailsclustered together and the polar phosphate head

groups associated with water molecules.

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Lipid bilayers show selective permeability

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S id li id h l f


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Steroids are lipids that regulate many aspects of

growth! Steroids are characterized by a carbon skeleton consisting of four fused

rings. Cholesterol is a common component of human cell membranes and is

essential for synthesis of other sterols.

Sex hormones like testosterone are made from cholesterol.

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Bonds, bonds and more bonds!

Covalent shared pair of electrons

Ionic electrostatic attraction between anions and cations

Hydrogen attraction between hydrogen and oxygen ornitrogen

Peptide links amino acids together in polypeptides

Disulfide bond between two S atoms stabilizing tertiarystructure of polypeptides

Ester linkage between fatty acids and glycerol oftriglycerides

Glycosidic linkage between sugars in polysaccharides

Phosphodiester linkage between nucleotides inpolynucleotides (DNA and RNA)

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04 Macromolecules-1