Post on 18-Dec-2015
Biochemistry VIBiochemistry VI
Proteins & EnzymesProteins & Enzymes
ProteinsProteins
Large, complex organic moleculesLarge, complex organic molecules
Made of smaller monomers: Amino AcidsMade of smaller monomers: Amino Acids
Categories of proteins:Categories of proteins:– Structural ProteinsStructural Proteins– Storage ProteinsStorage Proteins– Transport ProteinsTransport Proteins– Defensive ProteinsDefensive Proteins– EnzymesEnzymes
Structural ProteinsStructural Proteins
Used to provide structure and support for Used to provide structure and support for certain parts of organismscertain parts of organisms
Examples:Examples:– Keratin in hair/horns of animalsKeratin in hair/horns of animals– Collagen in connective tissuesCollagen in connective tissues– Silk in spider websSilk in spider webs
Storage ProteinsStorage Proteins
Used to store other molecules for later useUsed to store other molecules for later use
Examples:Examples:– Casein in milkCasein in milk– Ovalbumin in egg whitesOvalbumin in egg whites– Zein in corn seedsZein in corn seeds
Transport ProteinsTransport Proteins
Used to assist in the transport of Used to assist in the transport of molecules into and out of a cell or other molecules into and out of a cell or other membranemembrane
Examples:Examples:– Hemoglobin (OHemoglobin (O22 carrier) in red blood cells carrier) in red blood cells
– Integral membrane proteinsIntegral membrane proteins
Defensive ProteinsDefensive Proteins
Used to protect cells and organisms Used to protect cells and organisms against foreign substances or life formsagainst foreign substances or life forms
Examples:Examples:– AntibodiesAntibodies– Cell surface recognition proteinsCell surface recognition proteins– Poisons made by plants, insects, snakes, etc.Poisons made by plants, insects, snakes, etc.
EnzymesEnzymes
Regulate the rate of chemical reactionsRegulate the rate of chemical reactions
Examples:Examples:– DNA polymerase and helicaseDNA polymerase and helicase– LactaseLactase– PeroxidasePeroxidase– SucraseSucrase
Amino AcidsAmino Acids
The building blocks of proteinsThe building blocks of proteins20 total amino acids20 total amino acidsSome can be synthesized by humans, Some can be synthesized by humans, others must be consumedothers must be consumed
Carbon w/ 4 groups:Carbon w/ 4 groups:
AmineAmine
Carboxyl (acid)Carboxyl (acid)
HydrogenHydrogen
R group (varies)R group (varies)
Amino Acid R GroupsAmino Acid R Groups
R Groups determine the physical and R Groups determine the physical and chemical properties of the proteinchemical properties of the proteinThey can be polar, nonpolar, acidic, or They can be polar, nonpolar, acidic, or basic (importance?)basic (importance?)They can also be used for the attachment They can also be used for the attachment of other inorganic groups that are essential of other inorganic groups that are essential for the functioning of the proteinfor the functioning of the protein– Heme group on hemoglobin bonds to FeHeme group on hemoglobin bonds to Fe2+2+
– Other organic co-enzymes from our diet Other organic co-enzymes from our diet (vitamins)(vitamins)
Putting Amino Acids TogetherPutting Amino Acids Together
To build a protein, the amino acids must To build a protein, the amino acids must be connected by peptide bondsbe connected by peptide bondsPeptide bonds connect the amine group of Peptide bonds connect the amine group of one amino acid to the carboxyl group of one amino acid to the carboxyl group of the nextthe nextThis bond is caused by a dehydration This bond is caused by a dehydration reactionreactionA chain of connected amino acids is called A chain of connected amino acids is called a polypeptidea polypeptide
Where Do A.A.s Come From?Where Do A.A.s Come From?
Many foods contain amino acids in the Many foods contain amino acids in the form of proteinform of protein
When we digest protein, we recycle the When we digest protein, we recycle the amino acids and re-assemble them into amino acids and re-assemble them into our proteinsour proteins
Types of Amino AcidsTypes of Amino Acids
Structure of a ProteinStructure of a Protein
The code in the DNA recipe is a sequence The code in the DNA recipe is a sequence of A’s, T’s, C’s and G’sof A’s, T’s, C’s and G’sThe corresponding RNA copy of the recipe The corresponding RNA copy of the recipe contains this code, which is read in 3’scontains this code, which is read in 3’s– AUG, GGC, CUA, AAU, GCC, etc…AUG, GGC, CUA, AAU, GCC, etc…
Every 3 letter combination translates into 1 Every 3 letter combination translates into 1 specific amino acidspecific amino acidThe chain of amino acids has a specific The chain of amino acids has a specific sequencesequence
Structure of ProteinStructure of Protein
Primary StructurePrimary Structure– A unique sequence of amino acids in a polypeptide A unique sequence of amino acids in a polypeptide
chainchain
Secondary StructureSecondary Structure– Repeated folds and coils of a polypeptide chainRepeated folds and coils of a polypeptide chain
Tertiary StructureTertiary Structure– Irregular contortions from bonding of the side chains Irregular contortions from bonding of the side chains
of the various amino acidsof the various amino acids
Quaternary StructureQuaternary Structure– overall protein structure that results from the overall protein structure that results from the
aggregation of tertiary subunits aggregation of tertiary subunits
Fibrous ProteinsFibrous Proteins
Found only in animalsFound only in animals
Rod or wire-like shapesRod or wire-like shapes
Usually structural/storageUsually structural/storage
Water insoluble (hydrophobic R-groups)Water insoluble (hydrophobic R-groups)
Common in connective tissues, tendons, Common in connective tissues, tendons, bone matrix, and muscle fiberbone matrix, and muscle fiber
Examples: keratins, collagens, elastinsExamples: keratins, collagens, elastins
Globular ProteinsGlobular Proteins
Soluble in aqueous solutions (water)Soluble in aqueous solutions (water)
Apolar amino acids are oriented toward Apolar amino acids are oriented toward the center of the globe-like structurethe center of the globe-like structure
Used as enzymes, messengers Used as enzymes, messengers (hormones), transporters(hormones), transporters
Examples: hemoglobin, Examples: hemoglobin,
immunoglobulins, insulinimmunoglobulins, insulin
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EnzymesEnzymes
Enzymes speed up metabolic reactions Enzymes speed up metabolic reactions
Enzymes: catalytic proteins Enzymes: catalytic proteins
Catalyst: reduces the activation energy Catalyst: reduces the activation energy
Activation energy (EActivation energy (Eaa): energy required to ): energy required to
start a reaction start a reaction
EnzymesEnzymesSubstrate: reactant an enzyme works on Substrate: reactant an enzyme works on Active site: pocket where substrate is Active site: pocket where substrate is worked on worked on Induced fit: brings chemical groups into Induced fit: brings chemical groups into positions that enhance their ability to work positions that enhance their ability to work between the enzyme and substrate between the enzyme and substrate Effects of temperature and pH: enzymes Effects of temperature and pH: enzymes have an optimal temperature and pH they have an optimal temperature and pH they work withinwork withinMetabolic pathways consist of chains or Metabolic pathways consist of chains or cycles of enzymescycles of enzymes
Induced-Fit ModelInduced-Fit Model
EnzymesEnzymes
Cofactors: helpers bound into active site Cofactors: helpers bound into active site
Coenzyme: an organic cofactor Coenzyme: an organic cofactor
Competitive inhibitors: block the active site Competitive inhibitors: block the active site
Non-competitive inhibitors: bind to another Non-competitive inhibitors: bind to another part of the enzyme, inhibiting work part of the enzyme, inhibiting work
Allosteric site: receptor site away from the Allosteric site: receptor site away from the active site, where other molecules regulate active site, where other molecules regulate activityactivity
EnzymesEnzymes
Feedback (end-product) Inhibition: Feedback (end-product) Inhibition: metabolic pathway is switched off by its metabolic pathway is switched off by its end productend product
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