2 macromolecules 2015 ss
TRANSCRIPT
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PowerPoint Lecture prepared by Dr. Judi Roux,
University of Minnesota Duluth
Chapter 2
Hydrocarbons & Macromolecules
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Learning Outcomes
• Discuss the importance of carbon in living organisms.
• Describe the structure of carbohydrates, proteins, lipids, and nucleic acids and the roles these macromolecules play in cells.
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Carbon, hydrogen, oxygen, and nitrogen make up the bulk of living matter, because they form
MOLECULES
“CHNOPS”CarbonHydrogenNitrogenOxygen
PhosphorusSulfur
P is a major atom in DNA, RNA
S is found in two amino acids that are found in all proteins
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Atoms: the fundamental units of an element
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Covalent bonds = join atoms into molecules through electron sharing
In covalent bonds, two atoms share one or more pairs of outer shell electrons, forming molecules
Molecule = specific number of atoms sharing electrons in covalent bonds
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MolecularFormula
Electron DistributionDiagram
StructuralFormula
Space-FillingModel
O2
Oxygen
CH4
Methane
H2OWater
Polar covalent bondsin a water molecule
Single bond
Double bond
Nonpolar covalentbonds
Polar covalentbonds
(slightly −)
(slightly +) (slightly +)
H H
H
H
H
H
H H
O O
O
C
O
H H
H2
Hydrogen
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Unequal electron sharing creates
polar molecules• A molecule is nonpolar when its covalently bonded
atoms share electrons equally• A molecule is polar when one atom captures more
electrons, most of the time• Atoms gain a partial ionic charge, but• NO atom gains a complete +1 or -1 charge -
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Molecules behave as discrete units in water
- Atoms in molecules do not usually dissociate in water -Molecular bonds do not form ions – electrons shared equally
Small molecules dissolve in water when –They contain polar covalent bonds, &/or
They contain an ionic bond
IONIC AND COVALENT BONDS, REVISITED
caffeine glucose aspirinleucine
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Large molecules form stable structures in water
Lysozyme, a protein
DNA, a nucleic acid
tRNA bound to a protein
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INTRODUCTION TO ORGANIC COMPOUNDS
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INTRODUCTION TO ORGANIC COMPOUNDSLife’s molecular diversity is based on the properties of carbonA carbon atom can form four covalent bonds
• Allowing it to build large and diverse organic compounds
Structuralformula
Methane
H H
H
H H H
H
H
Ball-and-stickmodel
Space-fillingmodel
CC
The 4 single bonds of carbon point to the corners of a tetrahedron.
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Carbon atoms
bond covalently to build an infinite number of small to very large molecules
and even “molecular crystals” !
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Chemistry for Biology StudentsOrganic chemistry
Chemistry of biological systems
Concerns carbon-containing molecules• Interaction with other elements • E.g., hydrogen
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Life’s molecular diversity is based on the properties of carbon
• Methane and other compounds composed of only carbon and hydrogen are called hydrocarbons.
• Carbon, with attached hydrogens, can form chains of various lengths.
H
H
H
HC
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• Electrons sharedequally
• No partial charges• Hydrocarbons arenonpolar
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Hydrocarbons are composed of only hydrogen and carbon
There are an infinite variety of hydrocarbons!Molecules with the same molecular formula but different structures = isomersCan be any lengthCan be branched / unbranched
Can form ringsCan be rigid, flexible, or both- Hydrocarbon chains can bend at single bonds, but are rigid at double & triple bonds
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Figure 3.1b-0
Butane
Length: Carbon skeletons varyin length.
Propane 1-Butene 2-Butene
Double bonds: Carbon skeletons may havedouble bonds, which can vary in location.
Double bond
Isobutane Cyclohexane Benzene
Branching: Carbon skeletons maybe unbranched or branched.
Rings: Carbon skeletons may be arranged inrings. (In the abbreviated ring structures, eachcorner represents a carbon and its attachedhydrogens.)
Ethane
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A few chemical groups are key to the functioning of biological moleculesThe unique properties of an organic compound depend on
• the size and shape of its carbon skeleton and• the groups of atoms “functional groups” that are
attached to that skeleton.
• Functional groups are particular groupings of atoms that give organic molecules particular properties
For example:
The sex hormones testosterone and estradiol (a type of estrogen) differ only in the groups of atoms highlighted in the following figure:
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Testosterone Estradiol
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Functional Groups - Attached to hydrocarbon backbones
- Groups of atoms that react
H
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Cells make a huge number of large molecules from a particular set of small molecules
The four main classes of biological molecules:
lipids carbohydrates
proteins and nucleic acids
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LIPIDS
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Lipids• are water insoluble (hydrophobic, or water-fearing)
compounds,• are important in long-term energy storage,• consist mainly of carbon and hydrogen atoms linked
by nonpolar covalent bonds.• form aggregates.
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Any hydrocarbon is a “lipid” if it is hydrophobic
Lipids vary a great deal in structure and function.
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Biological MacromoleculesLipids
• Composed mostly of carbon and hydrogen
• Hydrophobic molecules
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Biological Macromolecules
Three types of lipids:
Fats: glycerol and three fatty acid tails• Store energy
Steroids: four fused carbon rings • Cholesterol and sex hormones
Phospholipids: glycerol molecule, two fatty acid tails, and a phosphate group
• Component of cell membranes
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Fats, also called triglycerides
• Are lipids whose main function is energy storage
• Consist of glycerol linked to three fatty acids
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
H2O
H HHH
OHOH OH
H
HOC O
C C C
Fatty acid
Glycerol
H HH
H H
CH2
O O O
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
CH2
CH2
CH2
CH2
CH2
CH2
CH
CH
CH2
CH2
CH2
CH2
CH2
CH2
CH3
C C C OOO
C C C
H
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3.1 Nutrients: MacronutrientsFats• Energy storage molecules
• Act as a cushion and insulator for skin & other organs
• Consist of a glycerol attached to fatty acid tails• Essential fatty acids: cannot be made in the body
(e.g., omega-3 and omega-6)
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Saturated fats Unsaturated fats
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3.1 Nutrients: Macronutrients
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3.1 Nutrients: Macronutrients
Saturated fats• Fatty acid carbons
bound to as much hydrogen as possible
• Lack double bonds
• Solid at room temperature
• Most animal fats are saturated
Unsaturated fats• Fewer hydrogens bound
to carbons
• Contain double bonds• Kinks in the tails
• Liquid at room temperature
• Most plant fats (oils) are unsaturated or polyunsaturated
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3.1 Nutrients: MacronutrientsFats
• Hydrogenation • Process of adding hydrogen atoms to unsaturated fat
to make it a solid
• Trans fats • Produced by incomplete hydrogenation
• Double bonds are flat and not kinked
• May be linked to increased health risks• Clogged arteries• Heart disease • Diabetes
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3.10 Phospholipids and steroids are important lipids with a variety of functions
• Phospholipids are the major component of all cell membranes.
• Phospholipids are structurally similar to fats.• Fats contain three fatty acids attached to glycerol.• Phospholipids contain two fatty acids attached to
glycerol.
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Phosphategroup
Glycerol
Hydrophilic heads
Hydrophobic tails
Symbol for phospholipid
Water
Water
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3.10 Phospholipids and steroids are important lipids with a variety of functions
• Phospholipids cluster into a bilayer of phospholipids.
• The hydrophilic heads are in contact with• the water of the environment and • the internal part of the cell.
• The hydrophobic tails cluster together in the center of the bilayer.
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3.10 Phospholipids and steroids are important lipids with a variety of functions
• Steroids are lipids in which the carbon skeleton contains four fused rings.
• Cholesterol is• a common component in animal cell membranes
and• a starting material for making steroids, including sex
hormones.
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Figure 3.10c
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Biological Macromolecules:Carbohydrates Proteins Nucleic Acids
Macromolecules
Large organic molecules comprise living organisms:
They are made by linking together smaller molecules called monomer subunits
In organic chemistry, such a larger molecule is called a polymer of these smaller monomers
Living systems make macromolecules = polymers of certain types of monomers
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Cells make most of their large molecules by joining smaller organic molecules into chains called polymers
H
OH H
OH
H OH
Unlinked monomer
Dehydration reaction
Longer polymer
Short polymer
OH H
H OH
Unlinked monomer
Dehydration reaction
Short polymer
H2O
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Polymers are broken down to monomers by the reverse process, hydrolysis
H
H2O
OH
H OHOH H
Hydrolysis
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CARBOHYDRATES
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Biological Macromolecules
Carbohydrates
• Molecules of carbon,oxygen, and hydrogen(CH2O)
• Major source of energyfor cells
• Made of sugar subunits• Monosaccharide: 1 sugar• Disaccharides: 2 sugars• Polysaccharide: many sugars
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The monosaccharides glucose and fructose are isomers
• That contain the same atoms but in different arrangements
• Both form rings when dissolved in water
C
C
C
C
C
C
C
C
C
C
H
H
H
H
H
H
H H
H
H
H
HO
H
H
H
C
O
HO
OH
OH
OH
OH OH
OH
OH
C O
OH
Glucose Fructose
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Figure 3.4c
Structuralformula
Abbreviatedstructure
Simplifiedstructure
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Polysaccharides are long chains of sugar units
Polysaccharides are macromolecules, polymers composed of thousands of monosaccharides.
• Polysaccharides may function as• storage molecules or• structural compounds.
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Starch granules ina potato tuber cell Starch
Glycogen granulesin muscletissue
Cellulose microfibrilsin a plant cell wall
Cellulosemolecules Hydrogen bonds
Cellulose
Glycogen
Glucosemonomer
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PROTEINS
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Proteins have a wide range of functions and structuresProteins are
• involved in nearly every dynamic function in your body and
• very diverse, with tens of thousands of different proteins, each with a specific structure and function, in the human body.
The types of proteins made by a cell determine what type of organism is made – goldfish, mushroom, rabbit, pine tree, snake, etc.
Genes determine what types of proteins a particular living system can make.
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Proteins have a wide range of functions and structures
Probably the most important role for proteins is as enzymes, proteins that
• serve as catalysts – “speed up” reactions and• regulate virtually all chemical reactions within cells.
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Proteins have a wide range of functions and structures
Other types of proteins include• transport proteins embedded in cell membranes,
which move sugar molecules and other nutrients into your cells,
• defensive proteins, such as antibodies of the immune system,
• signal proteins such as many hormones and other chemical messengers that help coordinate body activities,
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Proteins have a wide range of functions and structures
Other types of proteins include (continued)• receptor proteins, built into cell membranes, which
receive and transmit signals into your cells,• contractile proteins found within muscle cells,• structural proteins such as collagen, which form the
long, strong fibers of connective tissues, and• storage proteins, which serve as a source of amino
acids for developing embryos in eggs and seeds.
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Biological MacromoleculesProteins
• Made of carbon, oxygen, hydrogen, and nitrogen and some sulfur
Amino acid subunits• 20 different amino acids• Joined by peptide bonds• Different amino acid
combinations = different properties for proteins
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Aminoacids
+H3NAmino end
Peptide bondsconnect aminoacids.
Alphahelix
Secondary structuresare maintained byhydrogen bondsbetween atoms
of thebackbone.
Beta pleated sheet
Tertiary structure isstabilized by interactionsbetween R groups.
Polypeptides are associatedinto a functional protein.
TERTIARY STRUCTURE
PRIMARY STRUCTURE
QUATERNARYSTRUCTURE
Two types ofSECONDARY STRUCTURES
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At the molecular level
Form = Function
Protein shape determinesall its functions = 3o &/or 4o structure
Note:Primary Structure – type &position of amino acids inthe chain – determinesprotein shape!
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Tertiary & Quaternary Structure aligns functional groups on amino acid side chains,
- allowing the protein to interact with other chemicals and proteins
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NUCLEIC ACIDS
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NUCLEIC ACIDS
Nucleic acids are information-rich polymers of nucleotides
• Nucleic acids such as DNA and RNA encode the types of proteins made by a cell, and thus control the metabolism and functions performed by a cell
• Stretches of a DNA molecule called genes program the amino acid sequences of proteins
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Nucleic acids are polymers of nucleotides
DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are composed of monomers called nucleotides.
Nucleotides have three parts:1. a five-carbon sugar called ribose in RNA and
deoxyribose in DNA,2. a phosphate group, and3. a nitrogenous base.
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Sugar
Phosphategroup
Nitrogenousbase
(adenine)
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Nucleic acids are polymers of nucleotides
A nucleic acid polymer, a polynucleotide, forms from the nucleotide monomers when the phosphate of one nucleotide bonds to the sugar of the next nucleotide by dehydration reactions.
This produces a repeating sugar-phosphate backbone with protruding nitrogenous bases.
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DNA polynucleotide
A
C
T
G
T
Sugar-phosphate backbone
Phosphate groupNitrogenous base
SugarA
C
T
G
T
Phosphategroup
O
O–
OO P CH2
H3C C
C
C
CN
C
N
H
H
O
O
C
O
O
H
C H H
H
C
H
Nitrogenous base(A, G, C, or T)
Thymine (T)
Sugar(deoxyribose)
DNA nucleotide
DNA nucleotide
DNA and RNA are polymers of nucleotidesDNA is a nucleic acid made of long chains of nucleotide monomers
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DNA has four kinds of nitrogenous bases• A, T, C, and G
CC
C
CC
C
O
N
C
H
H
ONH
H3C
H H
H
H
N
N
N
H
OC
H HN
H C
N
N N
N
C
CC
C
H
H
N
N
H
C
CN
C HN
CN
H C
O
H
H
Thymine (T) Cytosine (C) Adenine (A) Guanine (G)
PurinesPyrimidines
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DNA and RNA are the two types of nucleic acids
The amino acid sequence of a polypeptide is programmed by a discrete unit of inheritance known as a gene.
Genes consist of DNA (deoxyribonucleic acid), a type of nucleic acid.
DNA is inherited from an organism’s parents.
DNA provides directions for its own replication.
DNA programs a cell’s activities by directing the synthesis of proteins.
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DNA forms a “double helix”Hydrogen bonds between bases hold two strands togetherEach base pairs with a complementary partner
• A with T, and G with C
G C
T A
A T
G
G
C
C
A T
GC
T A
T A
A T
A T
G C
A T
O
O
OH–O
P
O O–O
PO
OO
P– O
– O OP
OO
O
OH
H2C
H2C
H2C
H2C
O
O
O
O
O
O
O
O
PO–
O–
O–
O–
OH
HO
O
O
O
P
P
P
O
O
O
O
O
O
O
O
T A
G C
C G
A T
CH2
CH2
CH2
CH2
Hydrogen bond
Basepair
Ribbon model Partial chemical structure Computer model
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RNA, by contrast is a single-stranded polynucleotide
and contains uracil rather than thymine
Nitrogenous base (A, G, C, or U)
Phosphategroup
O
O–
OO P CH2
HC
C
C
CN
C
N
H
H
O
O
C
O
O
H
C H H
OH
C
H
Uracil (U)
Sugar(ribose)
KeyHydrogen atomCarbon atomNitrogen atomOxygen atom
Phosphorus atom
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Biological Macromolecules
Types of nucleic acids
RNA • For protein synthesis• Ribose sugar & uracil bas
DNA• Stores genetic information• Deoxyribose sugar & thymine base• Double helix structure
• Sugar-phosphate backbone• Rungs of nitrogen base pairs
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Recap:
Monomers & Polymers:
• Carbohydrates
• Proteins
• Nucleic Acids
Aggregates:
Lipids – any hydrophobic hydrocarbon
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Macromolecules act like “machines” as well as “building blocks”
Protein binding: Interleukin Receptor http://www.youtube.com/watch?feature=player_detailpage&v=Ms_ehUVvKKk 2014 Fall YouTube
Virus infecting bacterium YouTube http://www.youtube.com/watch?feature=player_detailpage&v=41aqxcxsX2w
Kinesin motor protein carrying a lysosome along a microtubule https://www.youtube.com/watch?feature=player_embedded&v=y-uuk4Pr2i8