Chapter 5—The Structure and Function of Macromolecules...Chapter 5—The Structure and Function of...

Chapter 5—The Structure and

Function of Macromolecules

C, L, P, N—4 ―BIG‖ Things You

Oughta Know About

I. Polymer Principles

• Most macromolecules are polymers

– Carbohydrates, proteins, & nucleic acids

• Polymer—

– Long molecule made up of similar or identical

building blocks covalently bonded together

• Monomer—

– Subunit/building block of a polymer

Synthesis & Breakdown of Polymers

Condensation reaction

(dehydration)—two monomers

are connected and water is lost

Monomers are added one by

one

Requires energy & enzymes

Hydrolysis—reverse of the

dehydration reaction, water is

added to break up monomers

How does this apply to

digestion?

II. Carbohydrates—Fuel & Building

Material

Monosaccharides

Molecular formula =

(CH2O)n

3 to 7 C atoms long

Functional groups =

hydroxyl & carbonyl

Form rings in

aqueous solutions

Serve as fuel

(respiration) and as

carbon sources for

building other

molecules

Glucose

Disaccharides

Storage Polysaccharides

Polysaccharides:

Polymers with

100s

to 1,000s of

monosaccharides

joined by

glycosidic

linkages

i.e. starch &

glycogen

Serve as storage

material (can be

broken down and

used as an

energy source)

Polysaccharides

Function is determined by:

1.) type of monomer

2.) positions of glycosidic

linkages

Starch:

1-4 α glucose linkages

Cellulose:

1-4 β glucose linkages

Structural Polysaccharides

Serve a structural

role (cell walls of

plants)

Cellulose

Structural Polysaccharides

Chitin—used to build

exoskeletons of arthropods

Like cellulose, except

monomer contains nitrogen

appendage

III. Lipids—‖We hate H2O!‖

Not a true polymer, but

building blocks include

glycerol and fatty acids

Nonpolar C—H bonds of the

fatty acid chains make them

hydrophobic

Fatty acids vary in:

1.) length

2.) # & location of double

bonds

Saturated vs. Unsaturated Lipids

Saturated =

No double

bonds,

straight, solid

at room temp.

Unsaturated =

Presence of

double bonds,

bent, liquid at

room temp. Main Function = compact form of energy storage (2x as

many calories per gram as carbs)

Also used for membranes, steroids, hormones

Phospholipids—in Cell Membranes

Steroids—such as Cholesterol

Component of animal cell membranes

Precursor for building other steroids/hormones

IV. Proteins—Many Structures,

Many Functions

Protein Facts

• Proteins:

– the most structurally sophisticated molecules

known

– > 50% of dry weight of most cells

– each has a unique 3-D structure

Amino Acids

20 different amino acids make up proteins

Components of an amino acid:

• amino group

• carboxyl group

• hydrogen atom

• variable R group/side chain (all around a central carbon atom)

Amino Acids are grouped

according to side chains/R groups

Nonpolar, polar, and electrically charged (acidic & basic)

Polypeptide– a polymer of

amino acids linked by

peptide bonds

Peptide bond connects

carboxyl group of one A.A.

to the amino group of

another A.A.

What type of reaction forms

polypeptides?

Polypeptide →

twist, fold, coil into

unique shape →

Protein

(Long piece of yarn → Sweater)

Lysozyme

4 Levels of Protein Structure

• Primary Structure—

– Unique sequence of amino acids in a

polypeptide

• Secondary Structure—

• Tertiary Structure—

• Quaternary Structure—

Small changes in primary structure

can have serious consequences

i.e. Hemoglobin protein and sickle cell disease

Secondary Structure

Secondary

Structure—

repetitive coiling

or folding in

protein backbone

due to hydrogen

bonds

Examples:

- Alpha helix

- Beta pleated sheet

Tertiary Structure

Tertiary Structure—

Overall shape of a

polypeptide due to

interactions between

side chains

(hydrophobic

interactions, ionic

bonds, hydrogen

bonds, and disulfide

bridges)

Quaternary Structure

Quaternary

Structure—

Two or more

polypeptide

subunits associate

to form a

functional protein

Let‘s Review…

Exposure to heat or chemical

treatments

(Nonfunctional in this state)

Chaperonins—protein folding

‗chaperones‘

X-ray crystallography is used to

determine 3-D protein structures

Information Flow in a Cell

DNA → RNA → Protein → Trait

Nucleic Acids allow

reproduction of complex

organisms from generation

to generation

DNA = Software

Proteins = Hardware

V. Nucleic Acids—polymers of

nucleotides

Gene = specific

nucleotide sequence

(100s → 1,000s long)

The sequence of the 4

nitrogen bases gives

each gene its ―meaning‖

(i.e. Protein

sequence/structure)

Two strands of double

helix are

complementary due to

base pairing (copying

allows for inheritance)

DNA & Proteins = ―tape measures‖ of

evolution