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Chapter 5: Structure and Function of Macromolecules

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Pyrimidine six-membered ring made up of carbon and nitrogen atoms. Cytosine (C) ... Purine 5 membered ring fused to a 6 membered ring. Adenine (A) Guanine ... – PowerPoint PPT presentation

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Title: Chapter 5: Structure and Function of Macromolecules


1
Chapter 5Structure and Functionof
Macromolecules
2
Polymers Most macromolecules are polymers
  • Definition Large molecule consisting of many
    identical or similar subunits connected together
  • Monomer Subunit or building block molecule of a
    polymer
  • Macromolecule Large organic polymer 4
    classes carbohydrates, lipids, proteins, nucleic
    acid

3
D. Making and breaking polymers
4
1. Polymerization reactions
  • Chemical reactions that link two or more small
    molecules to form larger molecules with repeating
    structural units

5
2. Condensation reactions (dehydration synthesis)
  • polymerization reactions during which monomers
    are covalently linked, producing a net removal of
    a water molecule for each covalent linkage
  • One monomer losses OH, the other one loses H
  • Requires energy and enzymes

6
3. Hydrolysis
  • A reaction that breaks covalent bonds between
    monomers by the addition of water molecules
  • One monomer gains OH, the other gains H
  • Digestive enzymes catalyze hydrolytic reactions

7
Linking Molecules Together
8
Carbohydrates
  • Organic molecules made of sugars and their
    polymers

9
A. Monosaccharide - Simple sugar in which C, H, O
occur in ratios of CH2O, carbons 3-7
  • Major nutrient for cells, especially glucose
  • Produced through photosynthesis store energy
    from the sun
  • Aldehyde terminal carbon forms a double bond
    with oxygen
  • Ketone carbonyl group within the carbon
    skeleton
  • Ring and linear forms in aqueous solutions,
    many monosaccharides form rings. Chemical
    equilibrium favors ring structure

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B. Disaccharides - Double sugar that consists of
two monosaccharides joined by a glycosidic linkage
  • Glycosidic linkage Covalent bond formed by a
    condensation reaction btwn 2 sugar monomers
  • Maltose (glucose glucose)
  • Lactose (glucose galactose)
  • Sucrose (glucose fructose)

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C. Polysaccharides- Polymers of a few hundred or
thousand monosaccharides
  • Storage Polysaccharides cells hydrolyze storage
    polysaccharides into sugars as needed, alpha 1,4
    linkages
  • Starch Glucose polymer, plant storage
  • Stored in granules in plastids
  • Amylase, unbranched
  • Amylopectin, branched
  • Glycogen glucose polymer, animal storage
  • Large polymer, highly branched
  • Stored in muscle and liver vertebrates

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Polysaccharides cont.
  • Structural polysaccharides
  • Cellulose linear unbranched polymer of
    D-glucose in beta 1,4 linkages (-OH of C1 in up
    position)
  • Major structural component of plant cell walls
  • Chitin amino sugar polymer
  • Exoskeleton in arthropods
  • Found in cell walls of some fungi

17
Lipids Nonpolar
18
A. Fats - Macromolecules constructed from
  • Glycerol 3 carbon alcohol
  • Fatty Acid (carboxylic acid)
  • Carboxyl group (head) at one end functions as
    an acid
  • Hydrocarbon carbon (tail) at other end,
    nonpolar, usually 16-18 Cs long
  • Ester linkage Bond formed between the hydroxyl
    of glycerol and the carboxyl of fatty acid by
    condensation
  • Triacylglycerol A fat composed of three fatty
    acids bonded to one glycerol by ester linkages
    (triglyceride)

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5. Characteristics of fat
  • Insoluble in water due to hydrophobic fatty acid
    chains
  • Variation among fat molecules due to fatty acid
    composition
  • Fatty acids may all be the same or different
  • Fatty acids vary in length

21
Characteristics of fat cont.
  • Saturated fat
  • No double bonds between Cs in the tail
  • Cs bonded to maximum number of Hs (saturated)
  • Usually solid at room temperature
  • Most animal fats
  • Unsaturated fat
  • One or more double bonds between Cs in tail
  • Tail kinks at each CC. So molecules do not pack
    closely enough to solidify at room temperature
  • Usually liquid at room temperature
  • Most plant fats (oils)

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Characteristics of fat cont.
  • Functions
  • Energy storage (9 Cal/g)
  • Cushions vital organs in mammals (kidneys)
  • Insulates against heat loss

24
6. Phospholipids - glycerol, 2 fatty acids,
phosphate group
  • Hydrophilic head (phosphate group)
  • Hydrophobic tail (fatty acids)
  • Major constituents of cell membranes

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Phospholipid bilayer separates the inside of
the cell from the outside of the cell, only water
and small ions can pass through
27
7. Steroids - four fused carbon rings with
various functional groups attached
  • Cholesterol
  • Precursor to many other steroids including
    vertebrate sex hormones and bile acids
  • Component of animal cell membranes
    stabilization and rigidity
  • Can contribute to atherosclerosis

28
Proteins
  • Molecular tools for most cellular function
    Consists of one or more polypeptide chains folded
    and coiled into specific conformations

29
Polypeptide Chains polymers of amino acids
that are arranged in a specific linear sequence
and are linked by peptide bonds
30
B. Function
  • Structural Support
  • Storage (of amino acids)
  • Transport (e.g. hemoglobin)
  • Signaling (chemical messengers)
  • Cellular response to chemical stimuli (receptor
    proteins)
  • Movement (contractile proteins)
  • Defense against foreign substances and disease
    causing organisms (antibodies)
  • Catalysis of biochemical reactions (enzymes)

31
C. Properties
  • Abundant 50 or more of cellular dry weight
  • Vary extensively in structure unique 3D shape
    (conformation)
  • Made up of 20 amino acid monomers in different
    amounts and combinations

32
D. Amino Acids - building block molecules of a
protein
  • Structure Asymmetric carbon, alpha carbon,
    bonded to
  • Hydrogen atom
  • Amino group
  • Carboxyl group
  • Variable R group (side chain) specific to each aa

33
  • Grouped by properties of side chains
  • Nonpolar side groups hydrophobic
  • Polar side groups hydrophilic
  • Uncharged polar
  • Charged polar
  • Acidic side groups dissociated carboxyl group
    negative charge
  • Basic side groups amino group w/extra proton
    positive charge

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E. Polypeptide Chains - polymers formed when
amino acids polymerize
  • Peptide bond Covalent bond formed by a
    condensation reaction that links the carboxyl
    group of one amino acid to the amino acid group
    of another
  • Backbone - N C C N C C N -

37
F. Protein Conformation 3D shape of a protein
function is dependent on structure
  • Protein Structure
  • Primary
  • Secondary
  • Tertiary
  • Quarterary

38
Primary structure - Unique sequence of amino
acids
  • Determined by genes
  • Slight change can significantly affect
    conformation

39
b. Secondary structure - Regular, repeated
coiling and folding of a proteins polypeptide
backbone
  • Contributes to overall structure
  • Stabilized by H bonds between peptide linkages in
    the protein backbone
  • Alpha Helix helical coil stabilized by
    H-bonding between every 4th peptide bond
  • Found in fibrous proteins (keratin, collagen) for
    most of their length and some portions of
    globular proteins
  • Beta Pleated Sheets sheets of antiparallel
    chains folded into accordion pleats
  • Make up dense core of globular protein and major
    portion of some fibrous proteins

40
Hydrogen bonds
41
c. Tertiary structure - Irregular contortions of
a protein due to bonding between side chains (R
groups) third level of protein structure
superimposed upon primary and secondary structure
  • Weak interactions
  • H-bonding between polar side chains
  • Ionic bonds between charged side chains
  • Hydrophobic interactions between nonpolar side
    chains in proteins interior
  • Covalent linkages Disulfide bridges form
    between two cysteine monomers strong bond

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d. Quaternary structure - Structure that results
from the interaction among polypeptides in a
single protein
44
Folding due to hydrophilic and hydrophobic amino
acids
45
G. Denaturation - A process that alters a
proteins native conformation and biological
activity caused by
  • Transfer to an organic solvent (nonpolar)
  • Chemical agents can disrupt H bonds, ionic bonds,
    and disulfide bridges
  • Excessive heat
  • Inappropriate pH

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V. Nucleic Acids - Protein conformation is
determined by primary structure. Primary
structure is determined by genes (DNA sequences)
48
A. DNA Deoxyribonucleic Acid
  • Contains coded info that programs all cell
    activity
  • Contains directions for its own replication
  • Is copied and passed from 1 generation of cells
    to another
  • In eukaryotic cells, found primarily in the
    nucleus
  • Genes direct the synthesis of RNA

49
B. RNA Ribonucleic Acid
  • Functions in the actual synthesis of proteins
    coded for by DNA
  • Sites of protein synthesis are on ribosomes in
    the cytoplasm
  • mRNA carries genetic message from nucleus to
    cytoplasm

50
C. Nucleotides building blocks of a nucleic
acid
  • Pentose 5-carbon sugar (RNA/ribose
    DNA/deoxyribose)
  • Phosphate group attached to a number 5 carbon of
    the sugar
  • Nitrogenous base
  • Pyrimidine six-membered ring made up of carbon
    and nitrogen atoms
  • Cytosine (C)
  • Thymine (T) found only in DNA
  • Uracil (U) found only in RNA
  • Purine 5 membered ring fused to a 6 membered
    ring
  • Adenine (A)
  • Guanine (G)

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Nucleotides cont.
  • Function
  • Monomers for nucleic acids
  • Transfer chemical energy from one molecules to
    another (ATP)
  • Are electron acceptors in enzyme controlled redox
    reactions (NAD)
  • Phosphodiester linkages between phosphate of one
    nucleotide and sugar of the next

53
DNA Structure
  • Two nucleotide chains wound in a double helix
  • Sugar-phosphate backbones are on the outside of
    the helix
  • Nitrogenous bases are paired in the interior of
    the helix and held together by H bonds
  • A-T and C-G pairing

54
What You Need to Know About Ch.5
55
The Principles of Polymers
  • List the four major classes of macromolecules.
  • Distinguish between monomers and polymers.
  • Draw diagrams to illustrate condensation and
    hydrolysis reactions.

56
Carbohydrates Serve as Fuel and Building Material
  • Distinguish between monosaccharides,
    disaccharides, and polysaccharides.
  • Describe the formation of a glycosidic linkage.
  • Distinguish between the glycosidic linkages found
    in starch and cellulose. Explain why the
    difference is biologically important.
  • Describe the role of symbiosis in cellulose
    digestion.

57
Lipids are a Diverse Group of Hydrophobic
Molecules
  • Describe the building-block molecules, structure,
    and biological importance of fats, phospholipids,
    and steroids.
  • Identify an ester linkage and describe how it is
    formed.
  • Distinguish between saturated and unsaturated
    fats.
  • Name the principal energy storage molecules of
    plants and animals.

58
Proteins have Many Structures and Many Functions
  • Distinguish between a protein and a polypeptide.
  • Explain how a peptide bond forms between two
    amino acids.
  • List and describe the four major components of an
    amino acid. Explain how amino acids may be
    grouped according to the physical and chemical
    properties of the R group.
  • Explain what determines protein conformation and
    why it is important.
  • Explain how the primary structure of a protein is
    determined.
  • Name two types of secondary protein structure.
    Explain the role of hydrogen bonds in maintaining
    secondary structure.
  • Explain how weak interactions and disulfide
    bridges contribute to tertiary protein structure.
  • List four conditions under which proteins may be
    denatured.

59
Nucleic Acids Store and Transmit Hereditary
Information
  • List the major components of a nucleotide, and
    describe how these monomers are linked to form a
    nucleic acid.
  • Distinguish between
  • pyrimidine and purine
  • nucleotide and nucleoside
  • ribose and deoxyribose
  • 5 end and 3 end of a nucleotide
  • Briefly describe the three-dimensional structure
    of DNA.
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