Transcript The Structure and Function of Macromolecules

The Structure and
Function of
Macromolecules
I. Polymers
• What is a polymer?
• Poly = many; mer = part. A polymer is
a large molecule consisting of many
smaller sub-units bonded together.
• What is a monomer?
• A monomer is a sub-unit of a polymer.
A. Making and Breaking
Polymers
• How are covalent linkages between
monomers formed in the creation of
organic polymers?
• Condensation or dehydration synthesis
reactions.
• Monomers are covalently linked to one
another through the removal of water.
Condensation Synthesis
Hydrolysis
• What is a hydrolysis reaction?
• Polymers are broken down into
monomers.
• Hydro = water; lysis = loosening/
• Water is added and the lysis of the
polymer occurs.
Hydrolysis
II. Classes of Organic
Molecules:
• What are the four classes of organic
molecules?
• Carbohydrates
• Lipids
• Proteins
• Nucleic Acids
A. Carbohydrates
• Sugars
• Carbo = carbon, hydrate = water;
carbohydrates have the molecular
formula (CH2O)n
• Functions:
• Store energy in chemical bonds
• Glucose is the most common
monosaccharide
• Glucose is produced by photosynthetic
autotrophs
1. Structure of
Monosaccharides
• An OH group is attached to each carbon
except one, which is double bonded to
an oxygen (carbonyl).
• Classified according to the size of their
carbon chains, varies from 3 to 7
carbons.
Triose = 3 carbons
Pentose = 5 carbons
Hexose = 6 carbons
• In aqueous solutions many
monosaccharides form rings:
2. Structure of Disaccharides
• Double sugar that consists of 2
monosaccharides, joined by a glycosidic
linkage.
• What reaction forms the glycosidic
linkage?
• Condensation synthesis
Examples of Disaccharides:
Lactose = glucose + galactose
Sucrose = glucose + fructose
3. Polysaccharides
• Structure: Polymers of a few hundred or a few
thousand monosaccharides.
• Functions: energy storage molecules or for structural
support:
• Starch is a plant storage from of energy,
easily hydrolyzed to glucose units
• Cellulose is a fiber-like structureal
material - tough and insoluble - used in
plant cell walls
• Glycogen is a highly branched chain
used by animals to store energy in
muscles and the liver.
• Chitin is a polysaccharide used as a
structural material in arthropod
exoskeleton and fungal cell walls.
B. Lipids
• Structure: Greasy or oily nonpolar
compounds
• Functions:
• Energy storage
• membrane structure
• Protecting against desiccation (drying out).
• Insulating against cold.
• Absorbing shocks.
• Regulating cell activities by hormone
actions.
1. Structure of Fatty Acids
• Long chains of mostly carbon and hydrogen
atoms with a -COOH group at one end.
• When they are part of lipids, the fatty acids
resemble long flexible tails.
Saturated and Unsaturated
Fats
• Unsaturated fats :
– liquid at room temp
– one or more double bonds between carbons in the
fatty acids allows for “kinks” in the tails
– most plant fats
• Saturated fats:
– have only single C-C bonds in fatty acid tails
– solid at room temp
– most animal fats
Saturated fatty
acid
Saturated fatty
acid
Unsaturated
fatty acid
2. Structure of Triglycerides
• Glycerol + 3 fatty acids
• 3 ester linkages are formed between a
hydroxyl group of the glycerol and a
carboxyl group of the fatty acid.
3. Phospholipids
• Structure: Glycerol + 2 fatty acids + phosphate group.
• Function: Main structural component of membranes, where
they arrange in bilayers.
Phospholipids in Water
4. Waxes
• Function:
• Lipids that serve as coatings for plant
parts and as animal coverings.
5. Steroids
•
•
•
•
Structure: Four carbon rings with no fatty acid tails
Functions:
Component of animal cell membranes
Modified to form sex hormones
C. Proteins
• Structure:
• Polypeptide chains
• Consist of peptide bonds between 20
possible amino acid monomers
• Have a 3 dimensional globular shape
1. Functions of Proteins
• Enzymes which accelerate specific
chemical reactions up to 10 billion times
faster than they would spontaneously
occur.
• Structural materials, including keratin
(the protein found in hair and nails) and
collagen (the protein found in
connective tissue).
• Specific binding, such as antibodies that
bind specifically to foreign substances
to identify them to the body's immune
system.
• Specific carriers, including membrane
transport proteins that move substances
across cell membranes, and blood
proteins, such as hemoglobin, that carry
oxygen, iron, and other substances
through the body.
• Contraction, such as actin and myosin
fibers that interact in muscle tissue.
• Signaling, including hormones such as
insulin that regulate sugar levels in
blood.
2. Structure of Amino Acid Monomers
• Consist of an asymmetric carbon covalently
bonded to:
• Hydrogen
• Amino group
• Carboxyl (acid) group
• Variable R group specific to each amino acid
Properties of Amino Acids
• Grouped by polarity
• Variable R groups (side chains) confer different
properties to each amino acid:
• polar, water soluble.
• non-polar, water insoluble
• positively charged
•
negatively charged.
4 levels of protein structure:
• primary
• secondary
• tertiary
•quaternary
3. Primary Structure
•
•
•
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Unique sequence of amino acids in a protein
Slight change in primary structure can alter function
Determined by genes
Condensation synthesis reactions form the peptide
bonds between amino acids
4. Secondary Structure
• Repeated folding of protein’s polypeptide
backbone
• stabilized by H bonds between peptide
linkages in the protein’s backbone
• 2 types, alpha helix, beta pleated sheets
5. Tertiary Structure
• Irregular contortions of a protein due to
bonding between R groups
• Weak bonds:
– H bonding between polar side chains
– ionic bonding between charged side chains
– hydrophobic and van der Waals interactions
• Strong bonds:
– disulfide bridges form strong covalent linkages
5. Quaternary Structure
• Results from interactions among 2 or more
polypeptides
Factors That Determine Protein Conformation
• Occurs during protein synthesis within cell
• Depends on physical conditions of environment
– pH, temperature, salinity, etc.
• Change in environment may lead to denaturation of
protein
• Denatured protein is biologically inactive
• Can renature if primary structure is not lost
D. Nucleic Acids
• Two kinds:
– DNA:
double stranded
can self replicate
makes up genes which code for proteins
is passed from one generation to another
– RNA:
single stranded
functions in actual synthesis of proteins coded for by
DNA
is made from the DNA template molecule
1. Nucleotide Monomer
Structure
• Both DNA and RNA are composed of
nucleotide monomers.
• Nucleotide = 5 carbon sugar,
phosphate, and nitrogenous base
Deoxyribose in DNA
Ribose in RNA
2. Building the Polymer
• Phosphate group of one nucleotide forms
strong covalent bond with the #3 carbon of the
sugar of the other nucleotide.
3. Functions of Nucleotides
• Monomers for Nucleic Acids
• Transfer chemical energy from one
molecule to another (e.g. ATP)
DNA:
• Double helix
• 2 polynucleotide chains
wound into the double helix
• Base pairing between
chains with H bonds
•A-T
•C-G
Summary of the Organic
Molecules: