Quiz 3 - Biochem (pro, enzy) Flashcards
What are some functions of proteins? (7)
-enzymes (DNA)
-structure
-carriers & transport
-cell communication (signals, receptors)
-defense
-movement
-storage
What is the structure of an amino acid?
-has a central asymmetric carbon
-attatched to 4 diff groups (exception of glycine ; R group is H)
-Amino group
-Carboxyl group
-Hydrogen
-R-group (varies for each acid)
What is the structure of proteins? (monomer)
= amino acids
-20 diff amino acids (9 are essential, and must come form diet)
What is the structure of proteins? (polymer)
= polypeptide
-one or more polypeptide chains folded n bonded together
-large and complex molecules
-complex 3d shape
How does the effect of diff R groups make a POLAR amino acid?
How does the effect of diff R groups make a NONPOLAR amino acid?
What does amino acids containing sulfur do?
-Forms disulfide bridges
-Covalent cross links between sulfhydryls
-Stabilizes 3-d structure
How do you build a protein?
-dehy syn, joins amino acids to form peptides
-covalent bond likes amino acids in a peptide is a PEPTIDE BOND
how do you form a polypeptide
-multiple peptide bonds result in a polypeptide
What are the names for the ends of polypeptide chains? (whats the end?)
- N-Terminus = NH2 end
- C-Terminus = COOH end
How do polypeptide chains grow?
Repeated sequence:
-N-C-C backbone
-can only grow in one direction
What is a proteins structure and function?
- FUNCTION DEPENDS ON STRUCTURE
- 3-D, twisted, folded.
-4 lvls of protein structure
Explain the Primary structure of a protein (3)
- Order of amino acids in chain
- sequence determined by genes (DNA)
- slight change can affect a lot; sickle cell anemia
Explain the Secondary structure of a protein (3)
- LOCAL FOLDING
- folding along short sections of polypep
- interactions between adjacent amino acids; H-BONDS, weak bonds
What does Local Folding form?
a(alpha) helix –> one helix
OR
B(beta)–> pleated sheet
a protein can have both!
Explain the Tertiary structure of a protein (5)
-WHOLE MOLECULE FOLDING
-interactions between DISTANT amino acids
-HYDROPHOBIC int.
-HBONDS n IONIC
-DISULFIDE BRIDGES, S-H
anchors 3D shape
Explain the Quaternary structure of a protein (3)
-MORE THAN ONE POLYPEP CHAIN bonded together
-only some proteins have quaternary
-HYDROPHOBIC int.
What is the smallest and largest protein? How many possible amino acid seq are there?
- Insulin (small)
- Titin (large)
For a polypeptide of “n” amino acids there are 20^n possible amino acid sequences
What does it mean to “denature” a protein?
- To UNFOLD it
- Conditions that disrupt H-bonds, ionic, & disulfide bridges
- Ex; temp, pH, salinity
- ALTERS 2nd n 3rd structure; 3D shape
What happens when you denature a protein
It destroys its functionality.
-Some can return to their functional shape, many cannot.
How can we visualize a protein
-x-ray crystallography
-extrapolating from amino acid sequence
What are the two reactions for Metabolism
ANABOLIC
- FORM bonds between molecules
- eg. dehy syn
CATABOLIC
-BREAK bonds between mols
-eg. hydrolisis
**both require ENZYMES to work
What chemical reactions RELEASE energy?
EXERGONIC
- digesting polymers
- hydrolisis reac (catabolic)
What chemical reactions require the INPUT of energy?
ENDERGONIC
- Building polymers
-Dehy syn (anabolic) reac
What is the difference between exergonic and endergonic reactions?
Exergonic : energy released, digestion (–delta G)
Endergonic : energy invested, synthesis (++delta G)
What is delta G?
Change in free energy, ability to do work
What is energy’s role in enzymes?
-Organisms require energy to live
-Comes from COUPLING exergonic + endergonic.
explanation: digestion produces products + energy
syn reactants r two things + energy to create one protein.
What drives reactions?
Covalent bonds are so stable; therefore reactions don’t just happen spontaneously
What is Activation energy?
- The initial input of energy requires to break down large mol
-must absorb energy to break bonds
How do you reduce activation energy?
- CATALYSTS
- reduce the amt of Ea needed to start a reaction (flattens hill)
So.. what are catalysts?
- Reduces activation energy
- ENZYMES are biological catalysts
- enzymes lower activation energy without affecting deltaG
Give 5 points on explaining enzymes
- For proteins (& RNA)
- Facilitate chemical reactions
- Required for most bio reac
- Highly specific (thousands of diff enzymes in cells)
- Control reactions of life
What is a substrate?
- Reactant which binds to and enzyme
(the bonded together mol)
What is a Enzyme-Substrate complex?
Temporary molecule formed when enzyme bonds with substrate
What is the Active site?
Enzyme’s catalytic site; substrate fits into active site
What are the products?
the end result of a reaction
What are the three properties of enzymes?
- REACTION SPECIFIC; only works w/ specific substrate; HBONDS , IONIC BONDS
- Not consumed in reaction; enzymes unaffected
- Affected by Cellular Conditions; any condition that affects protein structure affects enzyme function; eg temp pH salinity
How are enzymes named?
named for reaction they catalyze
Sucrase -> sucrose
Proteases -> proteins
Lipases -> Lipids
DNA polymerase -> builds DNA
Pepsin -> breaks down proteins
What are the two types of models for enzymes?
- Lock and Key; substrate fits into 3D structure of active site, Hbonds
- Induced fit model; more accurate, substrate binding cause enzyme to change shape leading to tighter fit
.. Conformational change
How does this whole enzyme process work?
SYNTHESIS
- active site orients substrates in correct position for reaction
DIGESTION
- active site binds substrate and puts stress on bonds that must be broken
What factors affect enzyme function?
-Enzyme concentration
-Substrate concentration
-Temperature
-pH
-Salinity
-Activators
-Inhibitors
Explain how enzyme concen affects enzyme function (reac rate); and whats the limiting factors?
as enzyme inc, so does R.R
-LF: substrate, not all enzyme mols can find substrate
Explain how substrate concen affects enzyme function (reac rate); and whats the limiting factors?
as sub inc, so does R.R
-LF: all enzymes already have active site engaged, SATURATED
how does temperature affect enzyme function?
-Optimum Temp
-Heat: disrupts bonds
-Cold: mol move slower
how does pH affect enzyme function?
-Changes in pH; adds or remove H+
-Has optimal pH
How does salinity affect enzyme function?
-adds or removes cations n anions
-disrupts bonds
-enzymes intolerant of extreme salinity
