Lecture_-_4
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LECTURE - 4 Biological Macromolecules – Proteins Answers – High Fructose Corn Syrup https://www.sciencenews.org/article/sweet-confusion Answers – Trans fats Most naturally occurring fats have their hydrogen atoms arrainged in a cis configuration. Some debate as to whether or not they are any worse than naturally occurring saturated fats Un-saturated fats are easier to breakdown and metabolize. (the double bonds help facilitate oxidization) Trans fat synthesis requires extremely high heat and high temperatures that can not be replicated in a home kitchen Outline Nucleic Acids Cont. Form follows function Amino Acids Protein Structure Protein Folding #3 Nucleic Acid - refresh Polymers called polynucleotides A single nucleotide consists of: Nitrogenous base A pentose sugar One or more phosphate groups 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) #3 Nucleic Acids 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 In DNA, the sugar is deoxyribose; in RNA, the sugar is ribose Nucleotide = nucleoside + phosphate group Figure 5.26c Nitrogenous bases Pyrimidines Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA) Sugars Purines Adenine (A) (c) Nucleoside components Guanine (G) Deoxyribose (in DNA) Ribose (in RNA) #3 Nucleic Acids Nucleotides are joined by covalent bonds that form between the —OH group on the 3 carbon of one nucleotide and the phosphate on the 5 carbon on the next #3 Nucleic Acids These links create a backbone of sugarphosphate units with nitrogenous bases as appendages #3 Nucleic Acids The sequence of bases along a DNA or mRNA polymer is unique for each gene #3 Nucleic Acids RNA -single polypeptide chains DNA - double helix Two backbones run in opposite 5→ 3 direction antiparallel #3 Nucleic Acids Complementary base pairing #3 Nucleic Acids Can also occur between two RNA molecules or between parts of the same molecule In RNA, thymine is replaced by uracil (U) so A and U pair #3 Nucleic Acids One DNA molecule includes many genes ~40,000 genes in the human genome 23 chromosome pairs Each chromosome is a DNA polypeptide 60 – 150 million base pairs per chromosome. Figure 5.27 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 Review - Macromolecules Nucleic Acids DNA & RNA Lipids Fatty Acids Phospholipids Steroids Carbohydrates Monosaccharides Starch/Glycogen Cellulose/chitin and Disaccharides Proteins Account for more than 50% of the dry mass of most cells Functions include: Enzymes Structural support Storage Hormones Transport Cellular communications Movement Defense against foreign substances Proteins - Enzymes Enzymes - a type of protein that acts as a catalyst to speed up chemical reactions Can perform their functions repeatedly. They carry out the processes of life. Proteins - Enzymes Enzymatic proteins Function: Selective acceleration of chemical reactions Example: Digestive enzymes catalyze the hydrolysis of bonds in food molecules. Enzyme Figure 5.15a Proteins - Hormones Figure 5.15c Hormonal proteins Function: Coordination of an organism’s 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 Proteins - Structural Figure 5.15h 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 Proteins – Storage Figure 5.15b 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 Proteins – Transport/Cell communicaton Figure 5.15f 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 Proteins – Cell/Cell communication Figure 5.15g 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 Proteins - Movement Figure 5.15d Contractile and motor proteins Function: Movement Examples: Motor proteins are responsible for the undulations of cilia and flagella. Actin and myosin proteins are responsible for the contraction of muscles. Actin Muscle tissue 100 m Myosin Proteins - Defense Figure 5.15e Defensive proteins Function: Protection against disease Example: Antibodies inactivate and help destroy viruses and bacteria. Antibodies Virus Bacterium Proteins - Polypeptides Proteins are Polypeptides (biologically functional) Polypeptides: unbranched polymers built from the same set of 20 amino acids(Amino acids are linked by peptide bonds) Range in length from a few to more than a thousand monomers Each polypeptide has a unique linear sequence of amino acids, with a carboxyl end (C-terminus) and an amino end (N-terminus) Amino acids Organic molecules with carboxyl and amino groups Amino acids differ in their properties due to differing side chains, called R groups Side chain (R group) carbon Amino group Carboxyl group Figure 5.16a Nonpolar side chains; hydrophobic Side chain Glycine (Gly or G) Methionine (Met or M) Alanine (Ala or A) Phenylalanine (Phe or F) Valine (Val or V) Leucine (Leu or L) Tryptophan (Trp or W) Isoleucine (Ile or I) Proline (Pro or P) Figure 5.16b Polar side chains; hydrophilic Serine (Ser or S) Threonine (Thr or T) Cysteine (Cys or C) Tyrosine (Tyr or Y) Asparagine (Asn or N) Glutamine (Gln or Q) Figure 5.16c Electrically charged side chains; hydrophilic Basic (positively charged) Acidic (negatively charged) Aspartic acid (Asp or D) Glutamic acid (Glu or E) Lysine (Lys or K) Arginine (Arg or R) Histidine (His or H) Proteins = AA polymers Condensation reaction results in peptide bond Peptide bond New peptide bond forming Side chains Backbone Amino end (N-terminus) Peptide bond Carboxyl end (C-terminus) Proteins – Form and Function A functional protein – A polypeptide that is properly twisted, folded, and coiled into its unique shape AA sequence determines the three-dimensional structure Structure determines the function Protein – Form and Function Groove Groove (a) A ribbon model (b) A space-filling model Protein – Form and Function Antibody protein Protein from flu virus Proteins - Form Three levels of protein structure Primary Structure – The unique sequence of amino acids. Secondary structure - Coils and folds in the polypeptide chain. Tertiary structure - Determined by interactions among various side chains (R groups). Some have a fourth level Quaternary structure - Results when a protein consists of multiple polypeptide chains. Proteins – Form – Primary Structure The sequence of amino acids in a protein. Kinda like the order of letters in a long word Read left to right Starts with amino group – N-terminus Ends with carboxy group – C-terminus Figure 5.20a Primary structure Amino acids Amino end Primary structure of transthyretin Carboxyl end Proteins – Form – Secondary Structure Secondary structure – Regular, repeated folds and twists Stabilized by hydrogen bonds Determined by aa sequence (primary structure) Two main Secondary Structures: helix – Coils pleated sheet- folds Proteins – Secondary Structure Helix Proteins – Secondary Structure Helix Function follows form A helices DNA binding (transcription factors, hox proteins, chromatin proteins…) Membrane spanning proteins Proteins – Secondary Structure Pleated Sheets Proteins – Secondary Structure Pleated Sheets Usually part of Protein/Protein interactions Silk is an example of pleated sheets Made up of multiple polypeptides packed together Amyloid Proteins Implicated in Alzheimer's, Parkinson’s & Huntington’s disease Mad Cow’s disease (Transmissible spongiform encephalopathy) Rheumatoid arthritis Chronic traumatic encephalopathy Accumulation of Tau Protein & Beta Amyloid plaques Proteins – Tertiary Structure The 3 dimensional shape of the whole protein
