4 Biomolecules

7/27/2019 4 Biomolecules

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B I O 1 6 L E C T U R E 4

CARBON COMPOUNDS IN

CELLS


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IMPORTANCE OF CARBON

Carbon permeates the world of lifefrom theenergy-requiring activities and structural

organization of cells, to physical and chemicalconditions that span the globe and influenceecosystems everywhere.


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HUMANS AND GLOBAL WARMING

Fossil fuels are rich in carbon

Use of fossil fuels releases CO2 into atmosphere

Increased CO2 may contribute to global warming


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ORGANIC COMPOUNDS

Hydrogen and other elementscovalently bonded to carbon

CarbohydratesLipids

Proteins

Nucleic Acids


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CARBONS BONDING BEHAVIOR

Outer shell of carbonhas 4 electrons; canhold 8

Each carbon atomcan form covalentbonds with up to 4atoms


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METHANE: SIMPLEST ORGANIC

COMPOUND

Structural formula

Ball-and-stick

model

Space-filling

model

HH

H

H

C

Figure 3.2Page 36


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BONDING ARRANGEMENTS

Carbon atoms can formchains or rings

Other atoms projectfrom the carbonbackbone

Glucose

(ball-and-stick model)

In-text figurePage 36


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HEMOGLOBIN MOLECULAR MODELS

Ball-and-stick model Space-filling model

Ribbon modelFigure 3.3Page 37


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FUNCTIONAL GROUPS

Atoms or clusters of atoms that are covalentlybonded to carbon backbone

Give organic compounds their different properties


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EXAMPLES OF FUNCTIONAL GROUPS

Methyl group - CH3

Hydroxyl group - OHAmino group - NH3

+

Carboxyl group - COOH

Phosphate group - PO3-

Sulfhydryl group - SH


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TYPES OF REACTIONS

Functional group transfer

Electron transfer

Rearrangement

Condensation

Cleavage


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CONDENSATION REACTIONS

Form polymers from subunits

Enzymes remove -OH from one molecule, H from

another, form bond between two molecules

Discarded atoms can join to form water


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Figure 3.7aPage 39

enzyme action at functional groups

CONDENSATION


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HYDROLYSIS

A type of cleavage reaction

Breaks polymers into smaller units

Enzymes split molecules into two or more parts

An -OH group and an H atom derived from water

are attached at exposed sites


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enzyme action at functional groups

Figure 3.7bPage 39

Hydrolysis


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CARBOHYDRATES

Monosaccharides(simple sugars)

Oligosaccharides(short-chain carbohydrates)

Polysaccharides(complex carbohydrates)


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MONOSACCHARIDES

Simplest carbohydrates

Most are sweet tasting,

water soluble

Most have 5- or 6-carbon backbone

Structure of glucose


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DISACCHARIDES

Type of oligosaccharide

Two monosaccharidescovalently bonded

Formed by condensationreaction

+ H2O

glucose fructose

sucrose

Figure 3.8bPage 40


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POLYSACCHARIDES

Straight or branched

chains of many sugar

monomers

Most common are

composed entirely of

glucose

Starch chain

Figure 3.9Page 40


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CELLULOSE & STARCH

Differences in bonding patterns betweenmonomers yield different properties

amylose (a starch)cellulose

Figure 3.10Page 41


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GLYCOGEN

Sugar storage form in animals

Large stores in muscle and liver cells

Figure 3.10Page 41


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CHITIN

Polysaccharide

Nitrogen-containing groups attached to glucosemonomers

Structural material for hard parts of invertebrates,cell walls of many fungi


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LIPIDS

Most include fatty acids

Fats

Phospholipids

Waxes Sterols and their derivatives have no fatty acids

Tend to be insoluble in water


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FATTY ACIDS

Carboxyl group at one

end

Carbon backbone

Saturated or unsaturated

linolenic

acidstearic acid oleic acidFigure 3.12Page 42


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FATS

Fatty acid(s) attached to

glycerol

Triglycerides are most

common

Figure 3.13Page 42


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PHOSPHOLIPIDS

Main component of

cell membranes

Hydrophobic head

Hydrophilic tails

Fig. 3.14a,b

Page 43


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STEROLS AND DERIVATIVES

No fatty acids

Rigid backbone of four

fused-together carbon

rings

Cholesterol - most

common type in

animals

Figure 3.15aIn-text p43

Cholesterol


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WAXES

Long-chain fatty acids linked to long-

chain alcohols or carbon rings

Firm consistency, repel water

Important in water-proofing


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AMINO ACID STRUCTURE

Aminogroup

Carboxylgroup

R group

Figure 3.16

Page 44

Figure 3.17Page 44

tryptophan(trp)


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PROTEIN SYNTHESIS

Peptide bond

Condensation reaction links amino group of one amino

acid with carboxyl group of next

Water forms as a by-product

Fig. 3.18aPage 45


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PRIMARY STRUCTURE

Sequence of amino acids

Unique for each protein

Two linked amino acids = dipeptide

Three or more = polypeptide

Backbone of polypeptide has N atoms:

-N-C-C-N-C-C-N-C-C-N-


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SECOND AND THIRD

LEVELS

Hydrogen bonding

produces helix or

sheet

Domain formation

Secondarystructure

Tertiary structure

Figure 3.19aPage 46


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FOURTH LEVEL STRUCTURE

Some proteins are

made up of more

than onepolypeptide chain

HLA-A2 quaternary structureFigure 3.20Page 47


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HEMOGLOBIN

alpha chain

beta chain alpha chain

beta chain


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ONE WRONG AMINO ACID

Single amino acid change in beta chain can causesickle-cell anemia

HbS

valine histidine leucine proline threonine glutamatevaline

Fig. 3.21c,dPage 48


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SICKLE CELL ANEMIA

Caused by two mutated copies (HbS) of Hb gene

Low oxygen causes red blood cells to clump

Clumping prevents normal blood flow

Over time, may damage tissues and organsthroughout the body


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NUCLEOTIDE STRUCTURE

Sugar

At least one

phosphate group

Nitrogen-containing

base

ATP

Figure 3.23a

Page 50


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NUCLEOTIDE FUNCTIONS

Energy carriers

Coenzymes

Chemical messengers

Building blocks for nucleic

acids


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DNA

Double-stranded

Sugar-phosphatebackbone

Covalent bonds inbackbone

H bonds betweenbases

Figure 3.25

Page 51


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RNA

Usually single strands

Four types of nucleotides

Unlike DNA, contains the base uracil in place ofthymine

Three types are key players in protein synthesis

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