Chapter 6 Proteins Flashcards
What monomer makes up protein? What is another word for protein?
- amino acids
- polypeptide
What 5 elements do they contain? What elements set it apart from carbs/lipids?
C, H, O, N (some S > disulfide bonds)
what are proteins determined by?
sequence of aa
What are the 10 functions of proteins?
proteins are the most diverse macromolecule
- enzymes
- lower activation energy and speed up chemical reactions - structural
- makeup cell membranes, bones, muscle, ligaments, tendons, hair, nails, skin - transport
- hemoglobin carry O2 in RBC, Na/K pump nutrients across membranes, aquaporins regulate fluid/electrolyte balance - hormonal
- regulate physiological processes (ex insulin)
- can be lipid-based (cholesterol) or protein-based (insulin) - defensive
- antibodies - contractile
- movement (ex actin and myosin) - receptor
- membrane-bound & receive chemical receptors - blood clotting
- gene expression
- regulate formation of other proteins - energy
- dont want this
How many amino acids are there? What are the 9 essential aa? Why are they essential?
20
- Histidine, Isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine
- cannot be made and need to be consumed
Desribe the structure of an amino acid - 5 components
- central carbon
- amino group (NH2)
- carboxylic acid group (COOH)
- hydrogen
- R group (side chain)
What differentiates amino acids from each other? What is it? What are its properties?
- R group
- chain of C with other elements (N,O,S)
- hydrophobic, hydrophilic, positive, or negative charges
What bonds binds amino acids together? What kind of bond is it? How are they created?
- peptide bond (formed first, then other bonds)
- covalent bond
- bond between carboxyl group of one aa and amine group of another aa
- aa can be 50 to 50k aa in length!
what is a conditionally essential aa
have period in life where non-essential but not making enough during certain periods so have to consume more of it. ex. pregnancy, puberty
What is the central dogma of biology and its process?
DNA > RNA > Protein
Duplication > transcription > translation
What are gene sequences?
specific sequences of DNA that codes for a specific protein
What are the 4 levels of protein structure?
- Primary: linear sequence of aa in order
- Secondary: how primary acids interact with each other
- alpha helix like coils of a spring
- beta-pleated sheets like accordion ribbons
- H bonds, ionic, R group interactions
- more bonds formed as protein grows - Tertiary: secondary structure interacts to form a more compact structure
- some proteins functional at this stage - Quaternary: 2 or more different polypeptides ineteract with each other
Ex. hemaglobin made of 4 different proteins, each non-functional by itself
What can one aa change do to a protein?
- render it inactive
- change in structure = change in function
Ex. sickle cell anemia one aa difference
-glutamate (hydrophilic) replaces valine (hydrophobic)
What is insulin so important to study as a protein? How many aa does it have? What is its structure? What disease is caused without it?
- first protein to be sequenced
- composed of 51 aa
- quaternary structure with 2 chains
- absence results in diabetes mellitus
Fibrous vs Globular proteins
What is its shape, solubility in water, and stability? What is the function of a fibrous protein? What do globular proteins have? What tissues are fibrous proteins found in? What are some specific examples of both?
What 2 proteins cross the boundary of both types of proteins?
Fibrous (structural)
-strand-like
-water-insoluble
-stable
-provide mechanical support and tensile strength
-components of skin, CT, blood vessel walls, parts of the eye
Ex. keratin (skin, hair, nails), elastin, collagen (most abundant protein in body), SOME contractile fibers
Globular (functional)
-compact
-spherical
-water-soluble
-sensitive to environmental changes
-specific functional regions (active sites)
Ex. antibodies, hormones, molecular chaperones, enzymes
Actin/myosin crosses boundary of both classes
What are molecular chaperones?
help guide things from point A to B, ex vitamins/fat terrible at transport and needs help of an enzyme
what are the characteristics of an enzyme? (10)
- globular proteins
- specific for specific reactions
- names end in -ase and named for the reaction they catalyze
- lower activation energy
- increase speed of reactions
- cannot force reactions to occur/would not react on their own
- make or break bonds
- reactants anything going into reaction
- products anything coming out
- not used up
What are the 3 steps in an enzymatic reaction?
- substrate binds to enzyme’s active site, temporarily forming the enzyme-substrate complex
- complex undergoes rearrangement of substrate, resulting in the final product
- product is released from the enzyme
what is protein denaturation? what causes it? (4) Are they reversible?
-unfolding of the protein (making compact structure linear)
- drop in pH (acidic)
- increase in pH
- increase in temp
- salts of heavy metals binds to the aa (ex lead poisoning)
- sometimes reversible under normal conditions
- sometimes irversible
What is allosteric regulation? What is an example? What does it allow cells to do?
How else is enzyme activity regulated?
-molecules binding at sites other than active site that produces a positive or negative regulation of an enzyme
Ex. feedback inhibition: too much of a product is made
-allows cell to control how much metabolism is needed
Ex. enzyme abundance (synthesis and degradation)
What are the 2 types of enzymes that adds/removes phosphates? What is the process called and what does it do?
- Kinase: transfer of a phosphoryl group using ATP as donor
- Phosphatase: remove phosphate group
- phosphorylation: can change enzyme activity to make it more or less active
What is the statin family of cholesterol drugs an example of? What does it do? (2) What is it also called? What is the enzyme, competitive inhibitor, and substrate named?
- competitive inhibitor
- inhibit the first comitted step in cholesterol biosynthesis (lower cholesterol)
- binds to the active site of an enzyme so substrate cannot bind there
- anti-hyperlipidemic agent
- competitive inhibitor: pravastin
- substrate: HMG-CoA
- enzyme: HMG CoA-reductase
What is the step-by-step process of protein digestion? (8) Where does the majority of protein digestion/absorption take place?
- Unike lipid/carbs, chemical breakdown in oral cavity does not occur
- travels esophagus
- Hydrochloric acid denatures proteins (uncoils strands) & starts digestion by converting pepsinogen into pepsin. Pepsin cleaves peptide bonds. More pepsin activates more pepsins.
- Pancreatic protease breaks down protein. Enteropeptidase lines the SI and activates trypsinogen into trypsin. More trypsin makes trypsin. Also activates all other pancreatic protease.
- Brush border enzymes digests proteins into monomers.
- absorbed via the Na/K pump in same mechanisms as carbs. Primary active transport on basal surface, and secondary active transport on apical surface. Different aa have different absorption sites.
- aa enters bloodstream
- carried to the liver
Majority of digestion/absorption takes place in the SI
zymogens
inactive form of enzyme (pepsinogen & trypsinogen)
