Macromolecules

Molecules of Life

Learning Objectives

• know the difference between a

dehydration synthesis reaction and a

hydrolysis reaction

• know the different types of biological

macromolecules

• be able to identify them

• know the role they play in biology

Lecture Outline

1. macromolecules and the reactions used

to make and break them

2. the macromolecules

Macromolecules

• large molecules made up of smaller

building blocks or subunits

• polymer: a long molecule made by

repeating smaller units strung together

• monomer: the small units that make a

polymer

• (not all macromolecules are polymers. . .)

Making polymers:

dehydration synthesis

requires cellular energy

Breaking polymers:

hydrolysis

releases energy

Types of macromolecules

• Carbohydrates

• Lipids

• Proteins

• Nucleic acids

Carbohydrates

• ratio of atoms 1C : 1 H2O

– ex: glucose C6H12O6

• primary fuel for all cellular activity

• hydrophilic polar molecules

• types of carbohydrates

– monosaccharides

– polysaccharides

Monosaccharides

• the simplest of sugars; contain 3 -7 C atoms

• C skeletons are used as raw material for

manufacturing other organic molecules

• ex. glucose

Usually in

ring form in

solution

Glucose is . . .

• in humans, most forms of carbohydrates

converted to glucose in digestive tract

• glucose circulates in our blood and is. . .

– used immediately as energy for cellular activity

– stored temporarily as glycogen (in liver & muscle)

– converted to fat for long term storage

Polysaccharides

• polymers of monosaccharides made by

dehydration synthesis; “complex carbs”

• as many as 10,000 joined monosaccharides

• two functions

– energy storage

• glycogen; in animals

• starch; in plants

– structural support

• cellulose; in plant cell walls (“fiber”)

• chitin; in insects, crustaceans, & cell walls of fungi

Making a polysaccharide by

dehydration synthesis

Polysaccharides

Types of macromolecules

• Carbohydrates

• Lipids

• Proteins

• Nucleic acids

Lipids

• diverse group of compounds with one common

trait: they are hydrophobic

• many more C-H bonds than carbs & contain

significantly more energy

• *NOT a polymer, but a large molecule made up

of 2 smaller molecules linked by dehydration

synthesis

• types of lipids

– fats (triglycerides)

– phospholipids

– sterols/steroids

dehydration

synthesis between

2 molecules, a

fatty acid and a

glycerol

Fats

(triglycerides)

• 3 fatty acid chains linked

to a glycerol molecule

• main function: energy

storage

– also protection & insulation

• two kinds of fat

– unsaturated

– saturated

– (in reality, there is a range)

Monounsaturated & polyunsaturated fats

Phospholipids

• 1 glycerol, 2 fatty acids,

and a phosphate group

• hydrophilic end and

hydrophobic end on

same molecule

• major component of cell

membranes; controls the

flow of chemicals into &

out of cell

Phospholipid bilayer of a

cell membrane

Sterols/steroids

• help regulate growth & development

• carbon skeleton is 4 fused rings

• ex: cholesterol– component in animal cell

membranes

– starting material for other steroids, including sex hormones estrogen & testosterone

Steroids can

increase

muscularity,

but with

serious health

consequences;

extreme

aggression,

high

cholesterol,

cancer

Talk to your neighbor

• How are carbohydrates and lipids similar?

How are they different?

Types of macromolecules

• Carbohydrates

• Lipids

• Proteins

• Nucleic acids

Proteins

• chief building blocks of all life

• 1000s of different proteins– enzymes (speed up chemical reactions)

– structural (connective tissue, hair, feathers, webs)

– contractile (muscle)

– defensive (antibodies)

– signal (hormones)

– receptor (in cell membrane)

– transport (delivers O2 to muscles & tissues)

• all proteins are polymers of amino acid monomers

Amino acids

• central carbon atom w/ carboxyl group,

amino group & an R group (side chain)

– the R group determines the characteristics

Expanded amino acid structures

Amino acids, continued

• 20 AA make up all proteins

• peptide bond refers to a bond b/w 2 amino acids formed by dehydration synthesis – between the carboxyl group of one AA and the amine

group of another

• polypeptide = a chain of amino acids (which = a protein)

Making a protein by

dehydration synthesis

(or, break proteins down by removing an

amino acid by hydrolysis)

Protein structure and function

• most proteins are globular in shape,

structural proteins typically are fibrous

• shape is very specific to job

– if proteins lose their shape they cannot function

properly, called denaturation

– caused by

• changes in pH

• excessive heat

• excessive salt concentrations

Types of macromolecules

• Carbohydrates

• Lipids

• Proteins

• Nucleic acids

Nucleic acids

• DNA and RNA

– function: carry genetic information

• polymers of nucleotide monomers

• made by dehydration synthesis

Nucleotide structure

• three parts

– 5 carbon sugar

– phosphate group

– 1 nitrogenous base

• cytosine

• guanine

• adenine

• thymine

• uracil

Part of a polynucleotide

• dehydration synthesis

b/w the phosphate

group of one

nucleotide and the

sugar of another

• called the sugar-

phosphate backbone

Comparing DNA & RNA

• DNA

– deoxyribose nucleic acid

– double stranded (double

helix)

– bases C, G, A, & T

• RNA

– ribonucleic acid

– single stranded

– bases C, G, A, & U

Talk to your neighbor

• What is the difference between nucleic

acids and amino acids?