The structure and function of large biological molecules

1
The structure and function of large biological
molecules
2
Four classes of biological molecules

• Carbohydrates
• Lipids
• Proteins
• Nucleic acids

3
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

4
Macromolecules are polymers, built from monomers
5
Macromolecules are polymers, built from monomers
What is a macromolecule?
6
Macromolecules are polymers, built from monomers
What is a macromolecule?

• Large and complex molecules, often chainlike

7
Macromolecules are polymers, built from monomers
What is a macromolecule?

• Large and complex molecules, often chainlike
• Monomer (simple subunits) building blocks form
  the chains

Monomer
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Macromolecules are polymers, built from monomers
What is a macromolecule?

• Large and complex molecules, often chainlike
• Monomer (simple subunits) building blocks form
  the chains
• Chains are called polymers

Polymer
Monomer
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Macromolecules are polymers, built from monomers
What 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

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Macromolecules are polymers, built from monomers
What 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

Whats a dehydration reaction?
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Macromolecules are polymers, built from monomers
HO
HO
H
H
1
2
3
Short polymer
Unlinked monomer
Dehydration removes a water molecule, forming a
new bond
H2O
H
HO
4
2
1
3
Longer polymer
12
Macromolecules are polymers, built from monomers
HO
HO
H
H
1
2
3
Short polymer
Unlinked monomer
This process can also be reversed
Dehydration removes a water molecule, forming a
new bond
H2O
H
HO
4
2
1
3
Longer polymer
13
Macromolecules are polymers, built from monomers
Hydrolysis
HO
H
1
2
3
HO
H
1
2
3
4
Hydrolysis adds a water molecule, breaking a bond
H2O
H2O
4
2
1
3
HO
HO
H
H
3
2
1
14
Macromolecules are polymers, built from monomers
Which of these is NOT a polymer?

• Carbohydrates
• Lipids
• Proteins
• Nucleic acids

1
2
3
H2O
4
2
1
3
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Macromolecules are polymers, built from monomers
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Carbohydrates serve as fuel and building material
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Carbohydrates serve as fuel and building material
What is a carbohydrate?
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Carbohydrates serve as fuel and building material

• Carbohydrates include
• Sugars
• Polymers of sugars

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Carbohydrates serve as fuel and building material

• Carbohydrates include
• Sugars (monosaccharides and disaccharides)

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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

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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
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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

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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

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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
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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

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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
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Carbohydrates serve as fuel and building material
Energy storage polysaccharides (both polymers of
glucose)
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Carbohydrates serve as fuel and building material
Energy storage polysaccharides (both polymers of
glucose)
How does an organism get energy from these
molecules?
29
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

30
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
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Carbohydrates serve as fuel and building material

• Structural polysaccharides

• Cellulose
• The most abundant organic molecule on Earth
• Major component of plant cell walls
• Made of glucose monomers (Beta linkages)

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Carbohydrates serve as fuel and building material

• Structural polysaccharides

• i.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

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Carbohydrates serve as fuel and building material
34
Lipids are a diverse group of hydrophobic
molecules
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Lipids are a diverse group of hydrophobic
molecules

• This group includes
• Fats
• Phospholipids
• Steroids
• All are hydrophobic (they do not mix well with
  water)

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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)
37
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

38
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
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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

40
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

41
Lipids are a diverse group of hydrophobic
molecules

• Steroids
• Lipids with a carbon skeleton that contains four
  fused rings

42
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

43
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

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Lipids are a diverse group of hydrophobic
molecules
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Proteins have many structures resulting in a wide
range of functions
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Proteins have many structures resulting in a wide
range of functions

• Protein structure
• Proteins are made from amino acid monomers
• All amino acids have a carboxyl group, an amino
  group, and an R group (variable)

47
Proteins have many structures resulting in a wide
range of functions

• Protein 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

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Proteins have many structures resulting in a wide
range of functions

• Protein 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
• Polypeptide polymers form when the carboxyl end
  is adjacent to an amino end (dehydration reaction
  forms a peptide bond)

49
Proteins have many structures resulting in a wide
range of functions

• Protein structure
• The amino acid sequence represents the proteins
  primary structure

50
Proteins have many structures resulting in a wide
range of functions

• Protein structure
• The amino acid sequence represents the proteins
  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.

51
Proteins have many structures resulting in a wide
range of functions

• Protein structure
• Tertiary structure results from interactions
  between R-groups. Interactions include
  hydrophobic interactions (leading to hydrophobic
  cores), hydrogen and ionic bonds, disulfide
  bridges

Hydrogen bond
Disulfide bridge
Ionic bond
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Proteins have many structures resulting in a wide
range of functions

• Protein structure
• Quaternary structure results from aggregation of
  multiple polypeptide subunits

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Proteins have many structures resulting in a wide
range of functions

• Protein 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)

54
Proteins have many structures resulting in a wide
range of functions

• Protein 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)

55
Proteins have many structures resulting in a wide
range of functions

• Protein 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)

56
Proteins have many structures resulting in a wide
range of functions
57
Nucleic acids store and transmit hereditary
information
58
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
  lifes activities (RNA helps relay the
  information)
• DNA to RNA to proteins

59
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
Phosphate group
Nitrogenous base
5'C
3'C
5'C
Sugar
3'C
3' end
60
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
Phosphate group
Nitrogenous base
5'C
3'C
5'C
Sugar
3'C
3' end
61
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
Phosphate group
Nitrogenous base
5'C
3'C
5'C
Sugar
3'C
3' end
62
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
Phosphate group
Nitrogenous base
Notice the distinct 5 and 3 ends
5'C
3'C
5'C
Sugar
3'C
3' end
63
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
3' end
5' end
3' end
64
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
3' end
5' end
3' end
65
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
3' end
5' end
3' end
66
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
3' end
5' end
3' end
67
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
3' end
How would an RNA molecule look different?
5' end
3' end
68
Nucleic acids store and transmit hereditary
information
69
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