macromolecules lecture
TRANSCRIPT
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CHAPTER 5The Structure and Function of
Macromolecules
“You are what you eat!”
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What does it mean to be a MACROmolecule?
You must be a Large molecule You have a complex structure
“little” moleculeMacromolecule
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I. Most macromolecules are polymers, built from monomers
What is a polymer?• Poly = many; mer = part. • A long molecule made of monomers
bonded together What is a monomer?
• A monomer is a sub-unit of a polymer.
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Three of the classes of life’s organic molecules are polymers• Carbohydrates, Proteins, Nucleic acids
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A. Making and Breaking Polymers
How do monomers bind to form polymers?• condensation reactions called
dehydration synthesis (removal of water)
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How can polymers break down when monomers are needed?
Hydrolysis reaction• Hydro = water; lysis = break• Water is added and the lysis of the
polymer occurs.
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Hydrolysis
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II. Classes of Organic Molecules:
• Carbohydrates• Lipids• Proteins• Nucleic Acids
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A. CARBOHYDRATES
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What are Carbohydrates?• Sugars and their polymers• Carbo = carbon, hydrate = water;
carbohydrates have the molecular formula (CH2O)n
Functions of Carbohydrates in living things:• Major fuel/energy source• Can be used as raw materials for other
Macromolecules• Complex sugars = building material in
plants What is the Carbohydrate Monomer?
• Monosaccharide (“mono” = one; “saccharide” = sugar)
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1. Structure of Monosaccharides Contain only C, H, O Hydroxyl group is attached to each carbon One carbon contains a carbonyl group
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• Classified according to the size of their carbon chains and location of Carbonyl group
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In aqueous solutions many monosaccharides form rings:
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2. Structure of Disaccharides
Consist of two monosaccharides Are joined by a glycosidic linkage What reaction forms the glycosidic linkage?
• Dehydration synthesis
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3. Polysaccharides
Structure: Polymers of a few hundred or a few thousand monosaccharides.
Functions: energy storage molecules or for structural support:
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Starch is a plant storage form of energy, easily hydrolyzed to glucose units
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Cellulose is a fiber-like structural material made of glucose monomers used in plant cell walls
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Why is Cellulose so strong? Glucose monomers are flipped to expose equal
Hydroxyl groups on either side of the chain When Cellulose chains are lined up next to each other,
they Hydrogen Bond making a strong material that’s difficult to break!
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Glycogen is the animal short-term storage form of energy
Glucose monomers
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Chitin is a polysaccharide used as a structural material in arthropod exoskeleton and fungal cell walls.
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B. LIPIDS What are Lipids?• Fats, phospholipids, steroids, waxes, pigments• Hydrophobic (“hydro”=water; “phobic” = fearing)• Consist mostly of hydrocarbons• Do NOT consist of polymers
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Functions of Lipids in living things:• Energy storage • membrane structure• Protecting against desiccation
(drying out). • Insulating against cold.• Absorbing shocks. • Regulating cell activities by
hormone actions.
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1. Structure of Fats (Triglycerides) Consist of a single glycerol and usually three
fatty acids Glycerol – an alcohol with three carbons Fatty Acid - Long Hydrocarbon chains with a
Carboxyl group at one end.
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Saturated and Unsaturated Fats
Unsaturated fats :• one or more double bonds
between carbons in the fatty acids allows for “kinks” in the tails
• liquid at room temp• most plant fats
Saturated fats:• No double bonds in fatty
acid tails• solid at room temp• most animal fats
(a) Saturated fat and fatty acid
Stearic acid
(b) Unsaturated fat and fatty acidcis double bondcauses bending
Oleic acid
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Saturated fatty acid
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Saturated fatty acid
Unsaturated fatty acid
Why are Unsaturated Fats better for you than Saturated Fats?
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3. Phospholipids Structure: Glycerol + 2 fatty acids +
phosphate group. Function: Main structural component of
membranes, where they arrange in bilayers.
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Phospholipids in Water
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4. Waxes
Function:• Lipids that serve as coatings for
plant parts and as animal coverings.
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5. Steroids Structure: Four carbon rings with no fatty acid
tails Functions:
• Component of animal cell membranes (Ex: Cholesterol)
• Modified to form sex hormones
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PROTEINS
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C. Proteins
What are Proteins?• Chains of amino acid monomers connected
by peptide bonds• Have a 3 dimensional globular shape
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Examples of Protein Functions Immune System
• Binding of antibodies (proteins) to foreign substances
Transport• Membrane transport proteins that move substances
across cell membranes• Hemoglobin carries oxygen, iron, and other
substances through the body. Muscle Contraction
• actin and myosin fibers that interact in muscle tissue.
Signaling• Hormones such as insulin regulate sugar levels in
blood.
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Amino Acids
Monomers of polypeptides• Molecules with carboxyl and amino
groups• Differ in their properties due to differing
side chains, called R groups
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20 different amino
acids existThe sequence of amino acids and the interactions of the different amino acids determine a proteins shape
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Peptide bonds connect amino acids to form polypeptide chains
One or more polypeptide chains make up a protein
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Proteins are very complex! Their specific structure determines their
function.
HEMOGLOBIN: Transport of gases and iron in blood ACTIN: Filament involved in
muscle contraction
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Four Levels of Protein Structure
Primary structure• Is the unique
sequence of amino acids in a polypeptide
Figure 5.20–
Amino acid subunits
+H3NAmino end
oCarboxyl end
oc
GlyProThrGlyThr
Gly
GluSeuLysCysProLeu
MetVal
Lys
ValLeu
AspAlaVal ArgGly
SerPro
Ala
Gly
lle
SerProPheHisGluHis
Ala
GluVal
ValPheThrAlaAsn
AspSer
GlyProArg
ArgTyrThr
lleAla
Ala
Leu
LeuSer
ProTyrSerTyrSerThr
Thr
Ala
ValVal
ThrAsnProLysGlu
ThrLys
SerTyrTrpLysAlaLeu
GluLle Asp
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O C α helix
β pleated sheet
Amino acidsubunits NC
H
C
O
C NH
CO
H
R
C N
H
C
O H
C
R
NH
H
R C
O
R
C
H
N
H
C
OHN
CO
R
C
H
N
H
HC
R
C
O
C
O
C
N
HH
R
C
C
O
NH
H
C
R
C
O
N
H
R
C
HC
ONH
H
C
R
C
O
N
H
R
C
H C
ONH
H
C
R
C
O
N H
H C R
N H O
O C N
C
RC
HO
CH R
N H
O C
RC H
N H
O C
H C R
N H
CC
N
RH
O C
H C R
N H
O C
RC H
HC
RNH
CO
C
N
H
R
C
HC
O
NH
C
Secondary structure• Is the folding or coiling of the polypeptide
into a repeating configuration resulting from hydrogen bonding of amino with carboxyl groups
• Includes the α helix and the β pleated sheet
H H
Figure 5.20
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Tertiary structure• Is the overall three-dimensional shape
of a polypeptide• Results from interactions between
amino acids and R groups
CH2CH
OH
O
CHO
CH2
CH2 NH3+ C-O CH2
O
CH2SSCH2
CH
CH3
CH3
H3C
H3C
Hydrophobic interactions and van der Waalsinteractions
Polypeptidebackbone
Hydrogenbond
Ionic bond
CH2
Disulfide bridge
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Quaternary structure• Is the overall protein structure that results
from the aggregation of two or more polypeptide subunits
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Chaperonins• Are protein molecules that assist in the
proper folding of other proteins
Hollowcylinder
Cap
Chaperonin(fully assembled)
Steps of ChaperoninAction: An unfolded poly- peptide enters the cylinder from one end.
The cap attaches, causing the cylinder to change shape insuch a way that it creates a hydrophilic environment for the folding of the polypeptide.
The cap comesoff, and the properlyfolded protein is released.
Correctlyfoldedprotein
Polypeptide
2
1
3
Figure 5.23
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Sickle Cell Disease: A simple change in Primary Structure
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Enzymes Are a type of protein that acts as a catalyst,
speeding up chemical reactions up to 10 billion times faster than they would spontaneously occur.
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Environmental Factors That Determine Protein Conformation
Change in environment may lead to denaturation of protein (pH, temperature, salinity, etc.)
Denatured protein is biologically inactive Can renature if primary structure is not lost
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NUCLEIC ACIDS
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D. Nucleic Acids : The stuff of Genes
Nucleic acids store and transmit hereditary information
Genes• Are the units of inheritance• Program the amino acid sequence of
polypeptides• Are made of nucleic acids
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Two Kinds of Nucleic Acids DNA (Deoxyribonucleic acid)
• double stranded• can self replicate• makes up genes which code for
proteins is passed from one generation to another
RNA (Ribonucleic acid)
• single stranded • functions in actual synthesis of
proteins coded for by DNA• is made from the DNA template
molecule
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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
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2. Building the Polymer Phosphate group of one nucleotide forms
strong covalent bond with the #3 carbon of the sugar of the other nucleotide.
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DNA:
• Double helix
• 2 polynucleotide chains wound into the double helix
• Base pairing between chains with H bonds
• A - T
• C - G
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Summary of the Organic Molecules: