Proteins (CH 3.4) Flashcards
What are the 7 job categories that proteins can fill?
- Enzyme Catalysis
- Defense
- Transport
- Support
- Motion
- Regulation
- Storage
How will the protein complete it’s duty as Enzyme Catalysis?
- Facilitate specific chemical reactions by stressing particular chemical bonds
- They’re 3D, globular & fit snuggly around the molecules they act on
How will the protein complete its duty in Defense?
- They will be globular shaped
- Use their shapes to “recognize” foreign microbes & cancer cells
- Form the core of the body’s endocrine & immune systems
How will the protein complete its duty in Transport?
- They will be Globular shaped
- Transport small molecules & ions
- membrane transport proteins will help move ions & molecules across the membrane
How will the protein complete its duty in Support?
- Will be protein fibers= keratin in hair, fibrin in blood clots, collagen
- If its collagen= will serve as matrix of skin/ ligaments/ tendons/ bones, Will be most abundant protein in vertebrate body
How will the protein complete its duty in Motion?
- Help in muscle contraction bc Actin & Myosin out here slidin
- Contractile proteins= play key roles in cell’s cytoskeleton & moving materials within cells
How will the protein complete its duty in Regulation?
- Will be smaller proteins= hormones= intercellular messenger in animals
- Turning genes off/on during development
- Receive info= actin like surface cell receptors
How will the protein complete its duty in Storage?
-Calcium & iron are stored in the body by binding as ions to storage proteins
What are proteins?
- Linear polymers made w/ 20 different amino acids which contains an amino group & acidic carboxyl group
- Composed of 1 or more unbranched chain (polypeptide)
What determines the protein’s structure & function?
-The specific order of amino acids
How do R groups effect Amino Acids?
-R groups determine the unique characteristic of each amino acid & the chemistry of them
What are the 5 Chemical Classes that the 20 amino acids are grouped into based on their R group?
- NONPOLAR amino acids often have R groups that contain -CH2 or -CH3
- POLAR charged amino acids have R groups that contain oxygen/ -OH
- CHARGED amino acids have R groups that contain acids or bases that can ionize
- AROMATIC amino acids are nonpolar, they contain R groups that have an organic (carbon) ring w/ alternating double & single bond
- SPECIAL FUNCTIONS= SPECIAL PROPERTIES
What does an Amino Acid have once it’s ionized?
- R group
- Positive amino (NH3+) group at one end & a negative (COO-) group at the other
- Both of these groups on a pair of amino acids have undergone dehydration reaction to form a covalent bond
What is a Peptide bond?
- Covalent bond that links 2 amino acids via dehydration reaction
- Has partial double bond character which prevents amino acids to rotate around N-C linkage
What is a Polypeptide?
- Composed of amino acids linked by peptide bonds
- An unbranched chain that when added with more forms a protein
- A protein=polypeptide ONLY WHEN theres only 1 chain in a protein
What kind of amino acids are inside nearly every protein?
-Nonpolar amino acids bc they’re shoved by water’s hydrophobic tendency to exclude nonpolar molecules
What kind of amino acids are outside the protein?
-Polar & Charged amino acids
What are the 4 Hierarchical levels of structure for a protein?
- Primary
- Secondary
- Tertiary
- Quaternary
What is the Primary level of the structure of a protein?
- Amino acid sequence
- Any of the 20 amino acids might appear at any position= great diversity
- A change to just one amino acid in a sequence will have drastic effects
What is the Secondary level of the structure of a protein?
- Hydrogen bonds forming between nearby amino acids
- Produces 2 different structures= Alpha-Helices & Beta-pleated sheets
What is the Tertiary level of the structure of a protein?
- Final folded shape via hydrophobic exclusion
- But folding is determined by the chemical nature of its side groups
- Determines how regions of 2ndary structure are further folded in space to form the final shape of the protein
- Last step for proteins with only a single peptide chain
How is the Tertiary structure stabilized?
- By forces including H bonding between R groups of different amino acids
- Electrostatic attraction between R groups w/ opposite charge (salt bridges)
- Hydrophobic exclusion of nonpolar R groups
- Covalent bonds in the form of disfulfides
- Also strongly influenced by how well it fits together
What are Disfulfides bonds?
-Covalent links between 2 cysteine R groups
What is the Quaternary level of the structure of a protein?
- Only found in proteins w/ 2 or more polypeptides
- Final structure of the protein is the arrangement of the multiple polypeptides in space
What are Motifs?
- Similar structures between dissimilar proteins
- Useful in detemining the function of unknown proteins
- “Words/ phrases”
What are the 3 common Motifs?
- Beta-Alpha-Beta= creates a fold/ crease= Rossmann fold at the core of nucleotide-binding sites in a wide variety of proteins
- Beta Barrel= Beta-Sheet folded around to form a tube
- Helix-Turn-Helix= 2 Alpha helices separated by a bend =used to bind to the DNA double helix
What are Domains?
-(of proteins) Are functional units within a larger
structure
-Can be thought of as substructure within the tertiary structure= “Paragraphs”
-Multiple Domains that make up most proteins perform different parts of the protein’s function
-Can be physically separated
-Can help proteins fold into its proper shape
-Correspond to the structure of genes & encode them
What are Chaperone Proteins?
- Located inside cells & helps other proteins fold correctly
- Many= Heat shock proteins which are produced in large amounts in response to elevated temperature bc high temp causes proteins to unfold
- Chaperonin= a class= super flexible, folding process within harnesses hydolysis of ATP to power these changes in structure necessary for function
What would happen if there are Chaperone Protein deficiencies?
-Can be implicated in diseases bc key proteins aren’t folded correctly
What is Denaturation?
-The protein’s shape changing or unfolding completely as a result of the protein’s environment being altered
How can proteins be denatured?
-When the pH, temperature, or ionic concentration of the surrounding solution changes
What are do denatured proteins do?
-Are usually biologically inactive= significant in the case of enzymes
What is Renaturation?
-When a protein’s normal environment is reestablished after denaturation, a small protein may spontaneously refold into its natural shape
What is Dissociation?
-When the subunits of proteins of the 4tnary structure separate WITHOUT losing their 3tiary structure
What is the general structure of an Amino Acid?
- Has central carbon= C-alpha
- Has an amino group on one side of c-alpha
- Has carboxylic acid on the other side of c-alpha
- And has a side chain/ R group attached to c-alpha
- This structure serves as the backbone for all 20 amino acids
