Protein Structure and Function Flashcards
The standard amino acids have the same general structure (primary amino group) with the exception of?
Proline (secondary amino group)
In proteins, almost all the carbonyl and amino groups are combined through
Peptide linkages/amide bond
Amino acids can behave as an acid or base
Amphoteric property
When PH > PkA this is ? D
- Acidic
- Protonated
- Amphoteric
- Deprotonated
Deprotonated (hydrogen has been removed)
PkA>PH
Protonated (hydrogen)
What are the four classes of amino acids
- Non polar
- Uncharged polar
- Acidic
- Basic
Non polar amino acid with two Hydrogen groups
Glycine (Gly)
Non polar amino acid with sulfur
Methionine (Met)
Non polar amino acid where the R group interacts with the amino acid
Proline (Pro)
- Non polar amino acid
- Forms a rigid ring structure because the R group interacts with the amino group, this geometry contributes to the formation of the extended fibroid structure of collagen
- Interrupts the alpha helices in more compact proteins
Proline
* This is caused by the substitution of the polar glutamate by non polar valine at the 6th position of the beta subunit of hemoglobin A
* replaces acidic amino acid with a non polar amino acid
Sickle cell anemia
Uncharged Amino Acids will have hydroxyl (OH), Amide ( C=O NH2), or sulfhydryl groups (SH)
STT
Serine (Ser)
Threorine (Thr)
Tyrosine (Tyr)
Uncharged polar amino acids that serve as attachment site for structures like phosphate groups
Hydroxyl
Uncharged polar amino acids that serve as attachment sites for oligosaccharide chains in glycoproteins
Amide and hydroxyl groups
Uncharged polar amino acids that serve as important components of the active site of enzymes
Sulfhydryl groups
AA - Methionine & Cysteine
What are the two acidic amino acids, contain a negatively charged (COO-) group. Proton donors
GA
Aspartate (Asp)
Glutamate (Glu)
What are the basic amino acids?
Side chains are fully ionized and positively charged
Proton acceptors
LAH
Lysine (Lys)
Arginine (Arg)
Histidine (His)
Amino Acid abbreviations
Amino acids not produced by the body
Essential - ACGPST
Amino acids produced by the body
Nonessential
Pair of compounds with exactly the same connectivity but opposite three-dimensional shapes
Enantiomers
- Rotate a plane of polarized light in the opposite direction
- Mirror images (cannot be superimposed on each other)
Optical isomers
Brønsted-Lowry acid
Proton donor
Brønsted-Lowry base
Proton acceptor
The larger the Ka, smaller the pKa
Strong acid
The smaller the Ka and larger the pKa
The weaker the acid
Formulas
Ka= [H+] [A-]/[HA] PkA = -log Ka Ph = -log [H+]
Henderson-Hasselbalch equation
PH = pKa + log [A-]/[HA]
PH>pKa
Log of >1 is positive
Deprotonated species (A-) dominates
PH less than pKa
Protonated (HA) dominates
What is the charge on the AA arginine at physiologic pH? D
- -2
- -1
- 0
- +1
- +2
+1
At physiologic pH, the amino group and carboxyl group of the AA form what charges? A
- +1, -1 respectively
- -1, +1 respectively
- 0, 0
- 0, -1 respectively
- -1, 0 respectively
+1, -1 respectively
T or F: The general structure of an AA contains a chiral carbon with a carboxyl group, secondary amine, hydrogen, and R group attached. F because it’s a primary amine
False, because it is a primary amine
Which of the following AA will you NOT likely find in an alpha-helix?B
- Cysteine
- Proline
- Methionine
- Valine
- Glutamine
Proline
The pH at which a molecule possesses no net charge is called: A
- Isoelectric Point
- Optimal pH
- Maximum Buffering Capacity
- Physiologic pH
- Extreme pH
Isoelectric Point
T or F Ka is defined as the dissociation constant of an acid. Therefore, the higher the Ka, the stronger the acid; the higher the pKa, the weaker the acid. T
True
When does maximum buffering capacity occur? B
- When the molecule has no net charge?
- When pH=pKa
- When the molecule has a positive charge
- When pH>pKa
- None of the above
When pH=pKa
Which of the following is the most abundant protein in the body? A
- Collagen
- Elastin
- a-Ketain
- Hemoglobin
- Myoglobin
Collagen
Which of the following is the correct order of collagen synthesis? A
- Procollagen, Tropocollagen, Collagen
- Tropocollagen, Procollagen, Collagen
- Collagen, Tropocollagen, Procollagen
- Procollagen, Collagen, Tropocollagen
- None of the above
Procollagen, Tropocollagen, Collagen
Where would you find Tropocollagen? D
- Golgi
- Rough Endoplasmic Reticulum
- Nucleus
- Extracellular Matrix
- Lysosomes
Extracellular Matrix
Which of the following ligands increases the affinity of hemoglobin for oxygen? D
- H+
- 2,3-BPG
- CO2
- CO
- All of the above
CO - carbon monoxide
Which bonds are found in the primary structure of proteins? D
- Amide
- Peptide
- Hydrogen bonds
- A, B
- A, B, C
Amide & Peptide
Which bonds are found in the secondary structure of proteins? C
- Amide
- Peptide
- Hydrogen bonds
- A, B
- A, B, C
Hydrogen Bonds
Which bonds/interactions are are found between the side chains (R groups) in the tertiary structure of proteins? E
- Hydrogen bonds
- Disulfide bonds
- Ionic Interactions
- Hydrophobic Interactions
- All of the above
All of the above
Which of the following diseases are caused by the prion protein (PrP)? C
- Alzheimer disease
- Parkinson disease
- Creutzfeldt-Jakob disease
- A, B
- Proteins don’t cause diseases
Creutzfeldt-Jakob disease
Amyloids (tau protein affected in the beta-pleated sheets) have been implicated in neurodegenerative disorders such as: D
- Alzheimer disease
- Parkinson disease
- Creutzfeldt-Jakob disease
- A, B
- Proteins don’t cause diseases
A & B
How many molecules of O2 can be transported by hemoglobin? D D
- 1
- 2
- 3
- 4
- 5
4
How many molecules of O2 can be transported by myoglobin? D D
- 1
- 2
- 3
- 4
- 5
1
Decreased production of normal hemoglobin is characterized by: D
- sickle-cell anemia (Hb S)
- Hemoglobin C disease
- Hemoglobin SC disease
- Thallassemia syndromes
- None of the above
Thallassemia syndrome
When a substrate itself serves as an effector, it is referred to as a: C
- Negative effector
- Positive effector
- Homotropic effector
- Heterotropic effector
- All of the above
Homotropic effector
Which of the following AA would likely serve as an attachment site for a phosphate group? D
- Serine
- Threonine
- Tyrosine
- All of the above
- None of the above
All of the above
what enzyme adds a phosphate group?
Kinase
What enzyme hydrolyzes peptide bonds?
Peptidases (Proteases)
proteins that perform the same function but have different primary structures
Isoforms
protein isoforms that function as enzymes
Isozymes
- Reservoir for oxygen
- oxygen carrier that increases the rate of transport of oxygen within the muscle cell
Myoglobin
- Transports oxygen from the lungs to the capillaries of tissues
- It can also transport hydrogen and carbon dioxide from the tissues to the lungs
Hemoglobin
These ligands stabilize the taut state (deoxygenated form) of hemoglobin and this leads to a decreased affinity for oxygen (right shift)
- increased H+ (low pH)
- Increased 2,3-bisphosphoglycerate
- Increased carbon dioxide
- increased carbon monoxide
- increased H+ (pH)
- Increased 2,3-bisphosphoglycerate
- Increased carbon dioxide
Most abundant protein in the body, composed of 3 polypeptide helices
Collagen
What are the markers of collagen that are not present in other proteins
- Glycine
- Hydroxyproline
- Hydroxylysine
- two of the options
- Hydroxyproline
- Hydroxylysine
Where would you find Procollagen? D
- Golgi
- Rough Endoplasmic Reticulum
- Nucleus
- Extracellular Matrix
- Lysosomes
Rough Endoplasmic Reticulum
This collagen genetic mutation results in fragile stretchy skin and loose joints
- Osteogenesis imperfects
- Ehlers-Danlos syndeom (EDS)
- Sickle Cell disease
- Alzheimer’s disease
Ehlers-Danlos syndeom (EDS)
Protein catalysts that increase the rate of reactions without being changed in the overall process
Enzymes
RNAs with catalytic activity , much less encountered than protein catalysts
Ribozymes
enzyme that requires ATP
Synthetase
Enzyme that does not require ATP
Synthase
Enzyme that removes a phosphate group
Phopshatase
Enzyme that breaks bonds by using inorganic phosphate
Phyosphorlyase
Adds a phosphate group form a high energy molecules such as ATP
Kinase
Enzyme that catalyzes oxidation - reduction reactions using oxygen as the electron acceptor but oxygen atoms are not incorporated into substrate
Oxidase
Enzyme that oxidizes a sub substrate by transferring oxygens to it
Oxygenase
This contains the AA side chains that participate in substrate binding and catalysis
Active site
Enzyme that interacts with one or a few substrates and catalyzing only one type of reaction
specific
Enzyme with its nonprotein component (active)
Holoenzyme
Enzyme without its nonprotein component (active) - magensium/zinc
Apoenzyme
Nonprotein moeity (inorganic or organic) of the enzyme
cofactor
nonprotein moeity (small inorganic molecule). Frequently derived from vitamins (i.e. NAD+ from niacin and FAD from riboflavin)
Coenzyme
Coenzymes that are permanently associated with the enzyme
Prosthetic group
Coenzymes that are only transiently associated with the enzyme
Cosubstrate
Enzymes that change their conformation when bound by an effector at a site other than actives site
- Cosubstrate enzymes
- Prosthetic enzymes
- Allosteric Enzymes
- Apoenzyme
Allosteric Enzymes
Which factors affect reaction velocity (speed of a reaction)
- Substrate concentration
- Temperatirs
- pH
- Acid/base
- three of the above
Increasing
- Substrate concentration
- Temperatirs
- pH
What will reflect a low affinity of enzyme for the substrate
- Large Km
- Small Km
Large Km
What is related order of reaction with respect to the substrate when:
- When [S] is much less than Km
- V is proportional to [S]
First Order
What is related order of reaction with respect to the substrate when:
- When [S] is greater Km
- V is constant and independent of [S]
Zero Order
Any substance that can diminish the velocity of an enzyme-catalyzed reaction is called an
- Apoenzyme
- Inhibitor
- Holoenzyme
- coenzyme
Inhibitor
Reversible inhibitors typically bind to enzymes through
- covalent bonds
- hydrogen bonds
- noncovalent bonds
- Hydrophobic bonds
noncovalent bonds
Irreversible inhibitors typically bind to enzymes through
- covalent bonds
- hydrogen bonds
- noncovalent bonds
- Hydrophobic bonds
covalent bonds
In competitive inhibition, what happens?
- Km increases, Vmax is unchanged and affinity decreases
- Km decreases, Vmax increases and affinity decreaes
- Km is unchanged, Vmax is decreases and affinity increases
- All the above
Km increases, Vmax is unchanged and affinity decreases
In noncompetitive inhibition, what happens?
- Km increases, Vmax is unchanged and affinity decreases
- Km decreases, Vmax increases and affinity decrease
- Km is unchanged, Vmax is decreases and affinity increases
- All the above
Km is unchanged, Vmax is decreases and affinity increases
EffEffCE
- Negative effector
- Positive effector
- Homotropic effector
- Heterotropic effector
- All of the above