The Structure and Function of Macromolecules Part II:
The Structure and Function of Macromolecules Part II: Proteins & Nucleic Acids (Ch. 5-3 and Ch.5-4) 1 Learning Objectives Explain the 7 different types of proteins. Describe the components of an amino acid and how amino acids are bonded together to form a polypeptide. Explain how interactions between individual amino acids determine the primary and secondary structures of proteins
Explain how interactions between the R groups between amino acids determine the tertiary structure. Explain how interactions between multiple polypeptides determine the quaternary structure. Learning Objectives Explain how DNA & RNA have structural similarities and differences are related to their function. Describe the difference between a purine and a pyrimidine base. Explain how the antiparallel DNA strands results in a double helix.
Proteins Come In Many Varieties! Proteins (or polypeptides) are large macromolecules made up of repeating units of amino acids account for more than 50% of the dry mass of most cells Protein functions include structural support, storage, transport, cellular communications, movement, and defense against foreign substances 4
Types of Proteins: Enzymes Enzymatic proteins Function: proteins that acts as a catalyst to speed up chemical reactions Example: Digestive enzymes catalyze the hydrolysis of bonds in food molecules. Enzyme Enzyme
5 Types of Proteins: Storage Storage proteins Function: Storage of amino acids Examples: Casein, the protein of milk, is the major source of amino acids for baby mammals. Plants have storage proteins in their seeds. Ovalbumin is the protein of egg white, used as an amino acid source for the developing embryo.
Ovalbumin Amino acids for embryo 6 Types of Proteins: Hormonal Hormonal proteins Function: Coordination of an organisms activities Example: Insulin, a hormone secreted by the pancreas, causes other tissues to take up glucose,
thus regulating blood sugar concentration High blood sugar Insulin secreted Normal blood sugar 7
Types of Protiens: Defensive Defensive proteins Function: Protection against disease Example: Antibodies inactivate and help destroy viruses and bacteria. Antibodies Virus Bacterium
8 Types of Proteins: Transport Transport proteins Function: Transport of substances Examples: Hemoglobin, the iron-containing protein of vertebrate blood, transports oxygen from the lungs to other parts of the body. Other proteins transport molecules across cell membranes. Transport protein
Cell membrane 9 Types of Proteins: Receptor Receptor proteins Function: Response of cell to chemical stimuli Example: Receptors built into the membrane of a nerve cell detect signaling molecules released by other nerve cells.
Signaling molecules Receptor protein 10 Types of Proteins: Structural Structural proteins Function: Support
Examples: Keratin is the protein of hair, horns, feathers, and other skin appendages. Insects and spiders use silk fibers to make their cocoons and webs, respectively. Collagen and elastin proteins provide a fibrous framework in animal connective tissues. Collagen Connective tissue 60 m
Monomer of Proteins - Amino Acids Amino acids are organic molecules with carboxyl and amino groups They differ in their properties due to differing side chains, called R groups 20 different R groups results in 20 naturally
occurring amino acids Side chain (R group) carbon Amino group Carboxyl group 12
Hydrophobic: Therefore retreat from water! Nonpolar side chains; hydrophobic Side chain Glycine (Gly or G) Methionine (Met or M) Alanine
(Ala or A) Valine (Val or V) Phenylalanine (Phe or F) Leucine (Leu or L) Tryptophan
(Trp or W) Isoleucine (Ile or I) Proline (Pro or P) Hydrophilic: Therefore Are Attracted to Water 14
Hydrophilic: But Electrically Charged! 15 Polypeptides Polypeptides are unbranched polymers built by linking together amino acids through dehydration synthesis Amino acids are bonded together by the formation of peptide bonds. A string of amino acids is called a polypeptide
16 Peptide Bonds 17 18 Polypeptides A protein consists of one or more polypeptides
The sequence of amino acids determines a proteins three-dimensional structure A proteins structure determines its function 19 Protein Structure: 4 Levels Primary structure - unique sequence of amino acids Secondary structure - consists of coils and folds in the polypeptide chain due to hydrogen bonding between the amine and carboxyl groups neighboring strands of amino acids.
Tertiary structure - determined by interactions among various side chains (R groups) Quaternary structure - multiple polypeptide chains join together to form final protein product 20 Primary Structure Primary structure is the sequence of amino acids in a protein Primary structure is
determined by inherited genetic information and is produced during translation of protein synthesis Primary Structure Secondary Structure The coils and folds of secondary structure
result from hydrogen bonds between repeating constituents of the polypeptide backbone Typical secondary structures are a coil called an helix and a folded structure called a pleated sheet 23 Secondary Structure
Secondary Structure Tertiary Structure Tertiary structure is determined by interactions between R groups of neighboring amino acids. These interactions include: Ionic bonds between ionized R groups. Covalent bonds called disulfide bridges between R groups with sulfydryls. Hydrogen bonds between polar, hydrophilic R groups Hydrophobic interactions of nonpolar R groups
26 Tertiary Structure 27 Quaternary Structure Quaternary structure results when two or more polypeptide chains form one macromolecule
Ex. Collagen is a fibrous protein consisting of three polypeptides coiled like a rope Ex. Hemoglobin is a globular protein consisting of four polypeptides: two alpha and two beta chains 28 Four Levels of Protein Structure Revisited
29 Denaturation Physical and chemical conditions can affect structure Denaturation - the loss of a proteins native structure Due to alterations in: pH salt concentration Temperature
A denatured protein is biologically inactive and NOT functional Denatured proteins retain their primary structure 30 Denature: Break Bonds or Disrupt IMFs 31 Nucleic Acids Nucleic acids - store, transmit, and help
express hereditary information There are two types of nucleic acids Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA) 32 Nucleotides Each nucleic acid is made of monomers
called nucleotides Each nucleotide consists of a: nitrogenous base a pentose sugar (contains 5 carbons) one (or more) phosphate group(s) 33 Figure 5.26ab Sugar-phosphate backbone
5 end 5C 3C Nucleoside Nitrogenous base 5C 1C 5C 3C 3 end
(a) Polynucleotide, or nucleic acid Phosphate group (b) Nucleotide 3C Sugar (pentose) Differences between DNA & RNA
In DNA, the sugar is deoxyribose; in RNA, the sugar is ribose DNA is double stranded; RNA is single stranded Possible nitrogen bases in DNA: adenine, thymine, cytosine, guanine In RNA, the nitrogen base uracil replaces thymine
35 Nitrogenous Bases There are two families of nitrogenous bases Pyrimidines (cytosine, thymine, and uracil) have a single six-membered ring Purines (adenine and guanine) have a sixmembered ring fused to a five-membered ring 36 Figure 5.26c
Nitrogenous bases Pyrimidines Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA)
Ribose (in RNA) Two Types of Nucleic Acids DNA provides directions for its own replication DNA directs synthesis of messenger RNA (mRNA) and, through mRNA, controls protein synthesis Protein synthesis occurs
on ribosomes 38 40 Polynucleotides Polynucleotides - Polymers of nucleotides more often referred to simply as DNA or RNA. Phosphodiester bond covalent bond formed by dehydration
reactions that join the OH group on the 3 carbon of one nucleotide and the phosphate on the 5 carbon of the next nucleotide forming a covalent 41 Dehydration synthesis 42
Polynucleotides have Direction RNA molecules usually exist as single polypeptide chains DNA molecules have two polynucleotides spiraling around an imaginary axis, forming a double helix In the DNA double helix, the two backbones run in opposite 5 3 directions from each other, an arrangement referred to as antiparallel One DNA molecule includes many genes
43 44 Complementary Base Pairing The nitrogenous bases in DNA pair up and form hydrogen bonds: adenine (A) always with thymine (T) guanine (G) always with cytosine (C) In RNA, thymine is replaced by uracil (U), A and U pair in RNA pairing
Complementary pairing can also occur between RNA molecules (ex. mRNA & tRNA during protein synthesis) 45 5 3 Sugar-phosphate backbones
Hydrogen bonds Base pair joined by hydrogen bonding 3 5 (a) DNA
Base pair joined by hydrogen bonding (b) Transfer RNA Link to Evolution The linear sequences of nucleotides in DNA molecules are passed from parents to offspring Two closely related species are more similar in DNA than are more distantly related species Molecular biology can be used to assess evolutionary kinship
47 Review!!! Monomers (or components) Polymer (or Larger molecule) Type of Linkage Carbohydrates
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