Biology 1010C

LSSC

Dr. Joseph Silver

in this chapter we willlearn about the

chemical building blocksof life

there are many facets of chemistryanalytical, quantitative, forensic, industrial,

inorganic, organic, and many more

the chemistry of life involves organic chemistrywhich is

the chemistry of carbon containing compounds

life on earth is based on theelement carbon

you are carbon based life forms

carbon has 4 valence electrons

in order to become stable a carbon atomcan give away 4 electrons

can gain 4 electronsor can share 4 electrons

carbon compounds containingonly

carbon, and hydrogenare called hydrocarbons

when all the available valence electronsform single carbon to carbon bonds

the chemical is saturated (page 34)but

if some carbon to carbon bonds aredouble or triple bonds

the compound is unsaturated (fig 3.27)

hydrocarbons (C and H) are non polar

butmany organic compounds contain

carbon, hydrogen, oxygen,nitrogen, sulfur, and phosphorus

theseare polar compounds

look at page 35 fig 3.2many organic compounds have

a carbon and hydrogen backboneto which

are added functional groups

functional groups provide specific chemical

properties to the organic compounds

look at figure 3.8fructose and glucose and galactose

have the same chemical formulabut they are each different

they are structural isomersthey have the same

6 carbons12 hydrogen

6 oxygen

but they are arranged differently in the molecule

in living systems isomers can have different shapes

the correct shape is important becauseenzymes, hormones, and receptors, are very

specific to theshape of the chemicals they interact with

why is this important?

message to cell – membrane carries message to cytoplasm

- series of chemical changes take place in cytoplasm

- changes carry message to nucleus - in nucleus message cause 1 gene to unwind

- DNA of gene makes a copy of the gene- the copy is known as messenger RNA (mRNA)

-mRNA leaves the nucleus-mRNA stimulates RER to make a protein enzyme

- enzyme tells cell what work to do

at every step chemicals fit together like pieces of a puzzle

if the pieces do not fit the process stops

some molecules exist as a single moleculethese are known as monomers

but

many biologically active molecules exist as long chains of monomers

these are polymers

look at figure3.5and learn the difference

between a dehydration (condensation) reaction

and a hydrolysis reaction

these reactions are common inall living organisms

DEHYDRATIONwhen 2 molecule are joined together

to form a larger compound

a H is removed from 1 reactantand an OH is removed from the 2nd reactant

resulting inthe formation of a molecule of water

the reactants were dehydrated (water was removed)

HYDROLYSISwhen a large molecule is being

split by an enzymethen

water is split to H and OHthe H is added to one part

and OH is added to the other part

water was split and added to the subunits

the next section deals with the chemistry and biological role of

saccharides (sugars)proteins (amino acid polymers)

lipids (fats and oils)and nucleic acids (DNA and RNAs)

most biologically active simple saccharides (sugars)

have 3, 4, 5, and 6 carbonsbut

these monomers can be arrangedinto many complex polymer sugars

such asstarch, glycogen, chitin, and cellulose made up of 100s or 1000s of sugars

3, 4, 5, and 6 carbon sugars are important in many functions

5 carbon sugars are important in DNA & RNAs

3,4, and 6 carbon sugars as monomers – dimers – and polymers

are important for energy, storage, and support

sugar is often transportedas a disaccharide

glucose + glucose = maltoseglucose + fructose = sucroseglucose + galactose = lactose

in animals sugar is storedas a highly branched amylose complex

called glycogenamylose is a complex form of glucose

see fig 3.10

in plants sugar is storedas a maltose complex

which islinked together with many maltose

moleculesto form starch

one of the simplest starches is amylose

cellulose is a complex polymerof glucose where the side chains

of glucose are cross linkedin such a way that the most enzymes

which digest starch cannotbreak down cellulose

thuscellulose is a good structural material

providing support for plants

chitin is a polymerized of glucosewhich links up with a protein component

to form a strong cross linked toughvery resistant material

whichforms the exoskeleton of

crustaceans and others

step on a cockroach and listen to thebreaking of the bonds in chitin

proteins are very complexthey consist of a polymerized moleculemade up of 20 different amino acids

proteins can include as few as 3 amino acidsmost proteins are made up of 100s or 1000s of amino acids

linked together to formspecific shapes

proteins function-as enzymes-tell the cell what to do-defense-fight infection and disease

-transport-oxygen, hormones, through membranes

-support-hair, skin, bone, muscle-motion-muscles, tendons, ligaments,

mitosis, meiosis-regulation-hormones, as enzymes, gene

activation-storage- calcium, iron, oxygen

there are 20 naturally occurring amino acidssome are polar, and others nonpolar

every amino acid has a generalized structure as

R(?) l

H2N - C - COOHlH

there are 20 different Rs

the R(?) on the generalized amino acidare shown on page 47

you will see that there are 20different functional groups

which make each of theamino acids different

when amino acids link togetherit is a dehydration reaction

when an amino acid is split from a proteinit is a hydrolysis reaction

when amino acids join together to form apolypeptide the molecule goes througha series of structural or shape changes

Look on page 49 to see the changesin shape as a protein is constructed

the molecule goes through a primary – secondary – tertiary structure

this folds the protein into the correct shape

why do we keep talking about shape?

molecules cannot talk to each other!But

when they fit together like pieces of a puzzlethe new molecule is then able to fit into another

moleculeeach linkage causes something to happen

in the cell membrane, cytoplasm, or nucleuswhich results in the cell doing

work needed by the cell, or body

proteins with the correct tertiary structurecan link up to form many complex proteins

with a quaternary shape

just as there are homeodomain proteinsfound in every living organism

there aresimilar sequences of amino acids

resulting in similar shapes in all living organismsthese are

protein motifsand are

common patterns found again and again in proteins

homeodomain proteins were discussed in chapter 1

these arefunctional units of a proteinwhich have specific tasks

and are ubiquitous

if a protein has the wrong shapeit cannot get the cell to do what the cell or body needs

so

the cells have developed a method tomake sure the shape is correct

and if needed to correct the shape

chaperone proteinsare

a group of barrel-like proteinswhich

attach to forming proteinsand use energy to make the folds and

shapes correct

see page 51

lipids are known as fats, oils, waxes

lipids or fats are usuallylong chains of non polar hydrocarbons

and are hydrophobic

a true lipidis

a long chain hydrocarbonwith a carboxylic acid group at the end

many lipids are in the form ofa triglyceride (see page 54)

glycerol is a 3 carbon sugara triglyceride has a lipid chain

attached to each of the 3 carbons of glycerol

there are many different kinds of triglycerides

depending on the kinds of lipids attached

to the glycerol component

on pages 53 and 54 read aboutsaturated

un or monounsaturatedpolyunsaturatedcis and trans fats

proteins and sugars provide 4 calories per grambut

most fats provide 9 calories per gram

our bodies can only store a small amount of sugar as glycogen and excess sugar

becomes fat

one of the most important lipid structures in our body

is our cell membranes which controlwhat goes in and out of a cell

our cell membranes are composed of a double

or bilayer of a phospholipid

cell membrane phospholipids consist of- glycerol

-2 fatty acid chains- a phosphate group

see page 55

the phosphate is the polar endthe fatty acids are the non polar end

when in contact with waterthe

polar end is in contact with the waterand the

non polar end is forced inwards away from the water

the result is a bilayer membrane (page 56)

the last molecule whose structure you should understand are the nucleic acids

(DNA & RNA)we will leave these for a later chapter