The structure and function of large biological molecules
Four classes of biological molecules
• Carbohydrates
• Lipids
• Proteins
• Nucleic acids
Key concepts
• Macromolecules are polymers built from monomers
• Carbohydrates serve as fuel and building material
• Lipids are a diverse group of hydrophobic molecules
• Proteins have many structures, resulting a wide range of functions
• Nucleic acids store and transmit hereditary information
Macromolecules are polymers, built from monomers
Macromolecules are polymers, built from monomersWhat is a macromolecule?
Macromolecules are polymers, built from monomersWhat is a macromolecule?
•Large and complex molecules, often chainlike
Macromolecules are polymers, built from monomersWhat is a macromolecule?
•Large and complex molecules, often chainlike•Monomer (simple subunits) building blocks form the chains
Monomer
Macromolecules are polymers, built from monomersWhat is a macromolecule?
•Large and complex molecules, often chainlike•Monomer (simple subunits) building blocks form the chains•Chains are called polymers
MonomerPolymer
Macromolecules are polymers, built from monomersWhat is a macromolecule?
•Large and complex molecules, often chainlike•Monomer (simple subunits) building blocks form the chains•Chains are called polymers•Monomers are connected via dehydration reactions
Macromolecules are polymers, built from monomersWhat is a macromolecule?
•Large and complex molecules, often chainlike•Monomer (simple subunits) building blocks form the chains•Chains are called polymers•Monomers are connected via dehydration reactions
What’s a dehydration reaction?
Macromolecules are polymers, built from monomers
Dehydration removes a watermolecule, forming a new bond
Short polymer Unlinked monomer
Longer polymer
HO
HO
HO
H2O
H
HH
4321
1 2 3
Macromolecules are polymers, built from monomers
Dehydration removes a watermolecule, forming a new bond
Short polymer Unlinked monomer
Longer polymer
HO
HO
HO
H2O
H
HH
4321
1 2 3
This process can also be reversed
Macromolecules are polymers, built from monomers
HO
H2O
H
4321
1 2 3
Hydrolysis adds a watermolecule, breaking a bond
HO
HO HO
H2O
H
H
H321
1 2 3 4
Hydrolysis
Macromolecules are polymers, built from monomers
H2O
4321
1 2 3• Carbohydrates
• Lipids
• Proteins
• Nucleic acids
Which of these is NOT a polymer?
Macromolecules are polymers, built from monomers
Carbohydrates serve as fuel and building material
Carbohydrates serve as fuel and building material
What is a carbohydrate?
Carbohydrates serve as fuel and building material
Carbohydrates include:• Sugars • Polymers of sugars
Carbohydrates serve as fuel and building material
Carbohydrates include:• Sugars (monosaccharides and disaccharides)
Carbohydrates serve as fuel and building material
Carbohydrates include:• Sugars (monosaccharides and disaccharides)
•Molecular formula is generally some multiple of CH2O•Glucose is a common monosaccharide (C6H12O6)•Glucose is a source of cellular energy
Carbohydrates serve as fuel and building material
Carbohydrates include:• Sugars (monosaccharides and disaccharides)
•Two monosaccharides joined by a covalent bond (glycosidic linkage)•Examples are sucrose and maltose
Dehydration reaction in the synthesis of maltose
Carbohydrates serve as fuel and building material
Carbohydrates include:• Sugars (monosaccharides and disaccharides)
•Two monosaccharides joined by a covalent bond (glycosidic linkage)•Examples are sucrose and maltose•Transport sugars in plants
Carbohydrates serve as fuel and building material
Carbohydrates include:• Sugars (monosaccharides and disaccharides)
•Two monosaccharides joined by a covalent bond (glycosidic linkage)•Examples are sucrose and maltose•Transport sugars in plants•Often found in energy supplements
Carbohydrates serve as fuel and building material
Carbohydrates include:• Sugars (monosaccharides and disaccharides)• Polymers of sugars (polysaccharides)
Polymers of a few hundred to a few thousand monosaccharides joined by glycosidic linkages
Carbohydrates serve as fuel and building material
Carbohydrates include:• Sugars (monosaccharides and disaccharides)• Polymers of sugars (polysaccharides)
Polymers of a few hundred to a few thousand monosaccharides joined by glycosidic linkages
•Energy storage polysaccharides •Structural polysaccharides
Carbohydrates serve as fuel and building material
Carbohydrates include:• Sugars (monosaccharides and disaccharides)• Polymers of sugars (polysaccharides)
Polymers of a few hundred to a few thousand monosaccharides joined by glycosidic linkages
•Energy storage polysaccharides •Structural polysaccharides
Different forms in plants and animals
Carbohydrates serve as fuel and building material
(b) Glycogen: an animal polysaccharide
Starch
GlycogenAmylose
Chloroplast
(a) Starch: a plant polysaccharide
Amylopectin
MitochondriaGlycogen granules
0.5 µm
1 µm
Energy storage polysaccharides (both polymers of glucose)
Carbohydrates serve as fuel and building material
(b) Glycogen: an animal polysaccharide
Starch
GlycogenAmylose
Chloroplast
(a) Starch: a plant polysaccharide
Amylopectin
MitochondriaGlycogen granules
0.5 µm
1 µm
Energy storage polysaccharides (both polymers of glucose)
How does an organism get energy from these molecules?
Carbohydrates serve as fuel and building material
Carbohydrates include:• Sugars (monosaccharides and disaccharides)• Polymers of sugars (polysaccharides)
Polymers of a few hundred to a few thousand monosaccharides joined by glycosidic linkages
•Energy storage polysaccharides •Structural polysaccharides
Carbohydrates serve as fuel and building material
Carbohydrates include:• Sugars (monosaccharides and disaccharides)• Polymers of sugars (polysaccharides)
Polymers of a few hundred to a few thousand monosaccharides joined by glycosidic linkages
•Energy storage polysaccharides •Structural polysaccharides
i.e. cellulose
Carbohydrates serve as fuel and building material
Structural polysaccharidesCellulose•The most abundant organic molecule on Earth•Major component of plant cell walls •Made of glucose monomers (Beta linkages)
Carbohydrates serve as fuel and building material
Structural polysaccharidesi.e. Cellulose•The most abundant organic molecule on Earth•Major component of plant cell walls •Made of glucose monomers (Beta linkages)•Unbranching•Forms microfibrils•Very strong building material
Glucosemonomer
Cellulosemolecules
Microfibril
Cellulosemicrofibrilsin a plantcell wall
0.5 µm
10 µm
Cell walls
Carbohydrates serve as fuel and building material
Lipids are a diverse group of hydrophobic molecules
Lipids are a diverse group of hydrophobic molecules
This group includes:•Fats•Phospholipids•Steroids
**All are hydrophobic (they do not mix well with water)
Lipids are a diverse group of hydrophobic molecules
Fats•Constructed from glycerol (an alcohol) and fatty acids (long hydrocarbon chains with a carboxyl group)•Form by dehydration reactions
Fatty acid(palmitic acid)
Glycerol(a) Dehydration rxn in fat synthesis
Ester linkage
(b) Fat molecule (triacylglycerol)
Lipids are a diverse group of hydrophobic molecules
Fats•Constructed from glycerol (an alcohol) and fatty acids (long hydrocarbon chains with a carboxyl group)•Form by dehydration reactions•Can be saturated or unsaturated
Structuralformula of asaturated fatmolecule
Stearic acid, asaturated fattyacid(a) Saturated fat
Structural formulaof an unsaturatedfat molecule
Oleic acid, anunsaturatedfatty acid
(b) Unsaturated fat
cis doublebond causesbending
Lipids are a diverse group of hydrophobic molecules
Fats•Constructed from glycerol (an alcohol) and fatty acids (long hydrocarbon chains with a carboxyl group)•Form by dehydration reactions•Can be saturated or unsaturated•Their function is energy storage (they store twice as much energy as starch)
Biodiesel
Lipids are a diverse group of hydrophobic molecules
Phospholipids•Major component of cell membranes•Consist of a glycerol with two fatty acids and a phosphate group
Lipids are a diverse group of hydrophobic molecules
Phospholipids•Major component of cell membranes•Consist of a glycerol with two fatty acids and a phosphate group•Polar nature of the molecule causes self-assembling of membranes
Lipids are a diverse group of hydrophobic molecules
Steroids•Lipids with a carbon skeleton that contains four fused rings
Lipids are a diverse group of hydrophobic molecules
Steroids•Lipids with a carbon skeleton that contains four fused rings•Includes hormones-Secreted chemicals that that travel through the body to act on a target
Lipids are a diverse group of hydrophobic molecules
Steroids•Lipids with a carbon skeleton that contains four fused rings•Includes hormones-Secreted chemicals that that travel through the body to act on a target•Also includes cholesterol-common component of animal cell membranes and a precursor from which other steroids are synthesized
Lipids are a diverse group of hydrophobic molecules
Proteins have many structures resulting in a wide range of functions
Proteins have many structures resulting in a wide range of functionsProtein structureProteins are made from
amino acid monomers• All amino acids have a
carboxyl group, an amino group, and an R group (variable)
Proteins have many structures resulting in a wide range of functionsProtein structure
Proteins are made from amino acid monomers
• All amino acids have a carboxyl group, an amino group, and an R group (variable)
• The R group determines the properties of the amino acid
Nonpolar
Glycine(Gly or G)
Alanine(Ala or A)
Valine(Val or V)
Leucine(Leu or L)
Isoleucine(Ile or I)
Methionine(Met or M)
Phenylalanine(Phe or F)
Trypotphan(Trp or W)
Proline(Pro or P)
Polar
Serine(Ser or S)
Threonine(Thr or T)
Cysteine(Cys or C)
Tyrosine(Tyr or Y)
Asparagine(Asn or N)
Glutamine(Gln or Q)
Electricallycharged
Acidic Basic
Aspartic acid(Asp or D)
Glutamic acid(Glu or E)
Lysine(Lys or K)
Arginine(Arg or R)
Histidine(His or H)
Proteins have many structures resulting in a wide range of functionsProtein structureProteins are made from amino
acid monomers• All amino acids have a
carboxyl group, an amino group, and an R group (variable)
• The R group determines the properties of the amino acid
• Polypeptide polymers form when the carboxyl end is adjacent to an amino end (dehydration reaction forms a peptide bond)
Peptidebond
Amino end(N-terminus)
Peptidebond
Side chains
Backbone
Carboxyl end(C-terminus)
(a)
(b)
Proteins have many structures resulting in a wide range of functionsProtein structure• The amino acid sequence represents the proteins
primary structure
Proteins have many structures resulting in a wide range of functionsProtein structure• The amino acid sequence represents the protein’s primary
structure• Secondary structure includes coils (alpha helices) and
pleats (beta pleated sheets). Both result from H-bonds between amino and carbonyl group of nearby amino acids.
pleated sheet
Examples ofamino acidsubunits
helix
Proteins have many structures resulting in a wide range of functionsProtein structure• Tertiary structure results
from interactions between R-groups. Interactions include: hydrophobic interactions (leading to hydrophobic cores), hydrogen and ionic bonds, disulfide bridges
Disulfide bridge
Ionic bond
Hydrogenbond
Proteins have many structures resulting in a wide range of functionsProtein structure• Quaternary structure results from aggregation of
multiple polypeptide subunits
Proteins have many structures resulting in a wide range of functionsProtein function•Proteins serve many important functions. Act as enzymes, cell signaling, movement, immune functions, etc.•Protein structure is often critical to their function (it often depends on the ability to recognize or bind other molecules)
Antibody protein Protein from flu virus
Proteins have many structures resulting in a wide range of functionsProtein function•Proteins serve many important functions. Act as enzymes, cell signaling, movement, immune functions, etc.•Protein structure is often critical to their function (it often depends on the ability to recognize or bind other molecules)•Environmental conditions can lead to protein denaturation (hence protein dysfunction)
Proteins have many structures resulting in a wide range of functionsProtein function•Proteins serve many important functions. Act as enzymes, cell signaling, movement, immune functions, etc.•Protein structure is often critical to their function (it often depends on the ability to recognize or bind other molecules)•Environmental conditions can lead to protein denaturation (hence protein dysfunction)
Proteins have many structures resulting in a wide range of functions
Nucleic acids store and transmit hereditary information
Nucleic acids store and transmit hereditary information
The role of nucleic acids• RNA and DNA are nucleic acids• DNA is the genetic material inherited from
parents• DNA contains the information that programs
all of life’s activities (RNA helps relay the information)
• DNA to RNA to proteins
Nucleic acids store and transmit hereditary information
The structure of nucleic acids• Nucleotide monomers link to
form polynucleotides (or nucleic acids)
5' end
5'C
3'C
5'C
3'C
3' end
Nitrogenousbase
3'C
5'C
Phosphategroup
Sugar
Nucleic acids store and transmit hereditary information
The structure of nucleic acids• Nucleotide monomers link to
form polynucleotides (or nucleic acids)
• Nucleotides contain three parts:– Nitrogenous base
• Purines (Adenine and Guanine)• Pyrimidines (Cytosine, Thymine,
Uracil)– 5-C sugar (Deoxyribose in DNA,
Ribose in RNA)– Phosphate group
5' end
5'C
3'C
5'C
3'C
3' end
Nitrogenousbase
3'C
5'C
Phosphategroup
Sugar
Nucleic acids store and transmit hereditary information
The structure of nucleic acids• Nucleotide monomers link to form
polynucleotides (or nucleic acids) • Nucleotides contain three parts:
– Nitrogenous base • Purines (Adenine and Guanine)• Pyrimidines (Cytosine, Thymine, Uracil)
– 5-C sugar (Deoxyribise in DNA, Ribose in RNA)
– Phosphate group
• Adjacent nucleotides are joined by a phosphodiester linkage (phosphate group that links the sugars of two nucleotides)
5' end
5'C
3'C
5'C
3'C
3' end
Nitrogenousbase
3'C
5'C
Phosphategroup
Sugar
Nucleic acids store and transmit hereditary information
The structure of nucleic acids• Nucleotide monomers link to form
polynucleotides (or nucleic acids) • Nucleotides contain three parts:
– Nitrogenous base • Purines (Adenine and Guanine)• Pyrimidines (Cytosine, Thymine, Uracil)
– 5-C sugar (Deoxyribise in DNA, Ribose in RNA)
– Phosphate group
• Adjacent nucleotides are joined by a phosphodiester linkage (phosphate group that links the sugars of two nucleotides)
5' end
5'C
3'C
5'C
3'C
3' end
Nitrogenousbase
3'C
5'C
Phosphategroup
Sugar
Notice the distinct 5’ and 3’ ends
Nucleic acids store and transmit hereditary information
The DNA double helix• Unlike RNA, DNA consists of
two polynucleotides that form a double helix
5' end
5' end
3' end
3' end
Nucleic acids store and transmit hereditary information
The DNA double helix• Unlike RNA, DNA consists of
two polynucleotides that form a double helix
• The two polynucleotides run in opposite 5 → 3 directions (antiparallel)
5' end
5' end
3' end
3' end
Nucleic acids store and transmit hereditary information
The DNA double helix• Unlike RNA, DNA consists of
two polynucleotides that form a double helix
• The two polynucelotides run in opposite 5 → 3 directions (antiparallel)
• The nitrogenous bases pair up and form hydrogen bonds: adenine (A) always with thymine (T), and guanine (G) always with cytosine (C)
5' end
5' end
3' end
3' end
Nucleic acids store and transmit hereditary information
The DNA double helix• Unlike RNA, DNA consists of
two polynucleotides that form a double helix
• The two polynucelotides run in opposite 5 → 3 directions (antiparallel)
• The nitrogenous bases pair up and form hydrogen bonds: adenine (A) always with thymine (T), and guanine (G) always with cytosine (C)
• The strands are complimentary!
5' end
5' end
3' end
3' end
Nucleic acids store and transmit hereditary information
The DNA double helix• Unlike RNA, DNA consists of
two polynucleotides that form a double helix
• The two polynucelotides run in opposite 5 → 3 directions (antiparallel)
• The nitrogenous bases pair up and form hydrogen bonds: adenine (A) always with thymine (T), and guanine (G) always with cytosine (C)
• The strands are complimentary!
5' end
5' end
3' end
3' end
How would an RNA molecule look different?
Nucleic acids store and transmit hereditary information
Key concepts
• Macromolecules are polymers built from monomers
• Carbohydrates serve as fuel and building material
• Lipids are a diverse group of hydrophobic molecules
• Proteins have many structures, resulting a wide range of functions
• Nucleic acids store and transmit hereditary information