Biochem MCQ 2018 Flashcards
Which are the Enzymes that Produce NADPH in the Pantose Phosphate Pathway?
1) Glucose-6-Phosphate Dehydrogenase
2) 6-Phosphogluconate Dehydrogenase
vWF Active form - Multimeric or Monomeric?
Multimeric
Structure of Arachidonic Acid and what is it produced from?
20:4 fatty acid chain
Produced from phospholipids ; phosphatidylethanolamine , phosphatidylcholine and phosphatidylinositol.
Which blood (components) cells are involved in the Dissolution of Fibrin to D-Dimers ?
Leukocytes: Monocytes and Neutrophills have Receptors that co-activate Plasmin and other Fibrinolytic agents.
3 ways Insulin regulates Lipolysis:
1) Activates PP1 that dephosphorylates HSL
2) Activates PDE
3) Inhibits Adenylate Cyclase
3 common Proteins on the ER Surface?
1) SERCA
2) IP3 Receptor
3) Ryanodine Receptor
Is there ketone bodies production under physiological conditions?
No
What regulates the Activity of ACC in a working Skeletal Muscle?
AMPK
How does the Work of Na/K pumps influence the Extracellular Concentration of Potassium?
Decrease it.
Sucrose Structure: Bond and Components
Glucose and Fructose linked by Alpha 1-2 Glycosidic Bond
AA with 4 carbons
Asp , Asn ,Thr
vWF Functions
1) Factor 8 binding
2) Platelet to sub-endothelial tissue binding upon injury
In the Neurons we have a reaction allowing Acetyl-CoA groups transfer to Oligodendroglia for FA Synthesis. Say it:
Acetyl-CoA+ Aspartate=> N-Acetylaspartate
Catalyzed by N-Acetylaspartate Synthase
What is the Aim of the Ornithine Cycle?
Formation of Urea in order to release Ammonia (2 Ammnonia groups) from the body in the urinary system.
Beta -Oxidation of 1 mole of Palmitate:
What are the Products and Additional Substrates?
Additional Substrates: 1 ATP, 7 FAD+, 7 NAD+ . Products: AMP, Pyrophosphate , 7 FADH2 , 7 NADH And 8 Acetyl-CoA.
Where is Carnitine Produced?
Liver (Mostly)
2 Enzymes that are needed in order to form Serotonin from Tryptophan (Cofactors as well) :
1) Trp Hydroxylase - with Tetrahydrobiopterin
2) Aromatic Amino acids Decarboxylase - with PLP
Why is Glycine the only Prorteogenic amino acid which is not Optically active?
It’s side chain is a Hydrogen atom.
What are the 5 Cofactors for PDH ?
1) TPP
2) Lipoic Acid
3) FAD
4) NAD
5) Coenzyme A
Lupus Anticoagulant:
Antibodies that attack phospholipid Membrane, thus increasing inappropriate coagulation and Platlet Aggregation.
Aspirin Activity - Reversible or Irreversible?
Irreversible
Which cells use Scavenger Receptors in an Artherosclerotic lesion?
What transition occurs in them?
Macrophages expressing scavenger receptors take up oxidized LDL deposited in Blood vessle walls.
Develop to Foam cells.
Amino Acid without chiral Center
Glycine
How many 2,3 BPG Molecules bind to the Tetramer Hemoglobin?
1
Conversion of Ornithine to Citruline -
Enzyme and Defect Results :
Ornithine Carbamoyl Transferase.
Defect leads to Hyperammonemia and Mental Retardation.
Order of the Enzymes of Beta-Oxidation:
1) Acyl-CoA Dehydrogenase
2) Enoyl-CoA Hydratase
3) Hydroxy-Acyl Dehydrogenase
4) Thiolase
Substrates and Products of Glutaminase Reaction:
S: Glutamine and Water
P: Glutamate and Ammonia/Ammonium
SRB1 Job:
Uptake of HDL in the Liver
What is the cause of K+ Ion Channel Saturation?
Diffusion Limit
Glutamate Dehydrogenase Reaction:
Glutamate + NADP (or NAD)+ H2O Will Give off:
NH4 + Alpha-KG + NADPH (or NADH)
Insulin receptor Subunits:
2xAlpha
2xBeta
If an Enzyme stops working at pH 6.4 Which AA is on its side chain?
Histidine
What are 3 the Enzymes needed to convert Propionyl-CoA to Succinyl-CoA?
Mention an Important Co-factor and a related Condition.
1) Propionyl-CoA Carboxylase (PCC)
2) Methmalonyl-CoA Racemase
3) Methmalonyl-CoA Mutase - Cofactor: Vit-B12.
without it - Secondary Carnitine Deficiency.
Conversion of UTP to CTP:
Enzyme and Nitrogen Donor?
CTP Synthetase
Glutamine
Where does LCAT and ACAT each act? What are they catalyzing?
Cholesteryl-Esters formation:
ACAT - in Tissue Cells
LCAT - in Plasma
Choose the Essential Amino Acids:
1) Ile
2) Ser
3) Cys
4) Phe
5) Trp
1, 4, 5
Isoleucine, Phenylalanine and Tryptophan.
Which enzyme deficiency leads to decrease in Urate and Ammonia level in serum after exercise?
AMP Deaminase Deficiency
PCC reaction:
Substrates, Products, Coenzyme.
Substrates : Propionyl-CoA, Bicarbonate and ATP
Products: Methmalonyl-CoA, ADP and Pi
Coenzyme: Biotin, as a Carboxyl group Carrier.
Functional Group of Serine?
CH2-OH
What factors are required in order to find the turnover number?
Vmax / Et
Which of the Following is involved in the De-novo synthesis of AMP? (Substrates and Enzymes)
1) Ribose-5-P
2) Orotate
3) Aspartate Carbamoyl Transferase
4) Phosphoribosyl-formylglycine Synthetase
5) IMP
1) Ribose-5-P
4) Phosphoribosyl-formylglycine Synthetase
5) IMP
Anticoagulants produced by Endothelial cells
1) tPA
2) NO
3) Prostacyclin
4) uPA
5) Heparan Sulfate
6) Thrombomodulin
7) TFPI
Enzymes requiring ATP in the Glycolytic Pathway?
Phosphofructokinase-1 (PFK1) and Hexokinase
Definition of Turnover Number
Maximum Number of Substrate converted to Product per second by each active site (unit s-1)
What happens when an LDL is binding to a SRA?
Ligand-Receptor Complex is Internalized
Which of the Following Amino acids are both Gluconeogenic and Ketogenic:
1) Ile
2) Val
3) His
4) Arg
5) Tyr
Isoleucine and Tyrosine
Prostethtic Group of Homocystiene Methyltransferase:
B12
What Enzyme Regulates the Insulin Secretion in the Beta Pancreatic Cells?
Glucokinase
What is SAM?
S-Adenosyl-Methionine, it is a Methyl group donor in multiple Methyl transferases Reactions
Name two Enzymes that can produce Arachidonic Acid? From which Substrates?
1) Delta-6-Desaturase Using Linoleic Acid , Leading to Cascade of Formation of Arachidonic Acid.
2) Phospholipase A2 from Membrane Phospholipids (Single Reaction).
Reaction of Aspartate transcarbmoylase:
Carbamoyl Phosphate +Asp will give
Aspartate Carbamoyl+ Pi
GLUTs of Astrocytes and Neurons?
Astrocytes: GLUT1
Neurons: GLUT3
Which are the 3 Amino Acids that participates in the formation of a Purine?
1)Glutamine - N3, N9
2)Glycine - C5, C4 and N7
3)Aspartate - N1
(also Bicarbonate + 2xTetrahydrofolate)
Heparin Anticoagulant activity:
Binds to Antithrombin causes conformational change leading to AT activation, AT will inactivate Thrombin and Factor Xa.
Non Polar Amino Acids
Leu, Ile , Val , Met , Phe , Trp , Ala , Pro
High Phosphoryl transfer potential compounds of Glycolytic pathway:
- Phosphoenolpyruvate
- 1,3 Bisphosphoglycerate
What are the 2 NADPH sources for Fatty Acid Synthesis?
1) Malic Enzyme
2) Pentose Phosphate Pathway (2 Dehydrogenases)
Name at least 4 Cellular effects of Muscarinic Ach receptors:
1) [Ca2+] Intracellularly elevates
2) Activation of Phospholipase C
3) Activation of K+ Channels
4) G-Protein Activation
On which side the K+ Ion Channel gate is located?
Intracellular side
Which Enzyme deficiency leads to High Arg Concentrations in Serum and Blood?
Arginase
What are compounds of the respiratory chain? (by their order)
1) NADH
2) Cytochrome C
3) Ubiquinone
Which amino acids have 2 chiral centers?
Isoleucine and Threonine
WRONG for Regulation of Plasma Cholesterol Level:
1) LDLR are under transcriptional Control based on SREBP
2) SREBP is Released following cholesterol-dependent proteolysis
3) SREBP is a nuclear receptor that binds Sterols.
4) LXR is a nuclear receptor that binds Sterols.
5) CYP7A1 is under transcriptional control based on LXR
3)!
SREBP is activated by proteolytic cleavage of SP1. SREBP precursors are retained in the ER membranes through a tight association with SCAP and a protein of the INSIG family
In the SAM Cycle, The Reaction between Homocysteine and N5-Methyl-Tetrahydrofolate :
Enzyme and Cofactor?
Which two products are formed?
Methionine synthase (aka Homocysteine methyl transferase) with cofactor Vit B12, catalyzes this reaction. Homocysteine + N5-Methyl-Tetrahydrofolate => Methionine + Tetrahydrofolate
Regulatory Enzyme for Deoxynucleutide Reaction:
rNTP + R(SH)2=>dNTP + R-S2
Ribonucleutide Reducatse
What metabolic intermediate will be present in high concentration in the plasma after prolonged Fasting?
( Under physiological Conditions)
Free Fatty Acids
Name 2 Secondary Bile Acids?
What is their Common structural trait? (In contrast to Primary ones)
Deoxycholic Acid and Lithocholic Acid
They have no Hydroxyl Group on 7’.
Acyl-CoA Cholesterol Acyltransferase Reaction (ACAT)?
Location?
Cholesterol + Acyl-CoA -> Cholesteryl-Ester
Happens in ER
How can Thrombin act as an Anticoagulant?
In Complex with Thrombomodulin and Protein C and S it Activates Protein C -> Inactivation of FV, FVIII
3 Most Important Precursors of Gluconeogenesis:
1) Lactate
2) Glycerol
3) Alanine
Amino Acids that are part of the Conjugation of Bile Acids:
Taurine and Glycine
Regulation of PFK1:
Positive:
F2,6BP ,ADP, AMP (Insulin-PP1)
Negative:
ATP , H+ and Citrate (Glucagon-PKA)
Which statement is NOT valid for FXIII?
1) It’s a substrate for Thrombin.
2) It catalyzes peptide bonds in fibrinogen and fibrin.
3) It’s activity facilitates the incorporation of Alpha-2-Plasmin inhibitor in the Thrombi.
4) It’s deficiency causes Hemorrhage.
2)X It catalyzes peptide bonds in fibrinogen and fibrin. X
Wrong!
It is a Transglutaminase creating an Isopeptide between Lys and Gln Residues of Antiparallel Fibrins.
True!
Which enzyme deficiency leads to Orotic Aciduria?
UMP Synthase : Converts Orotic Acid to UMP
What is the Glucose Transporter in the Glucose sensory cells Pancreas?
GLUT2
What Enzyme Deficiency causes Essential Fructoseuria ?
Fructokinase Deficiency
Maltose Structure: Bond and Components
Two Glucose Molecules linked by Alpha 1-4 Glycosidic Bond
3 Proteins (at least) Participating in Reverse Cholesterol Transport:
1) ABCA1
2) Apoprotein A1
3) LCAT
2) SRB1
S-Adenosyl-Methionine (SAM) donating a Methyl Group will be called afterwards: (full name)
S-Adenosyl-Homocysteine (SAH)
3 Co-Enzymes of Bile Acids Synthesis:
1) NADPH
2) NADH
3) CoA
Name at least 3 Molecules participating the vesicular transport of Ach Neurotransmitter;
1) ATP
2) H+
3) Ca2+
Unit of specific activity?
U/milligram
Why does Aspirin causes gastric bleeding?
Inhibits COX-1 in GI which Role in Gastric Mucosa secretion. Protection Declines.
How much ATP is produced from the conversion of 1 Mole of Glucose to 2 Moles of Lactate?
2 ATP
What are the 3 Main Ketone Bodies? (Know the Struc)
Acetone, Acetoacetate, beta-Hydroxybutyrate
Streptokinase Action:
Forms a Complex with Plasmin and Plasminogen leading to Zymogen Self activation.
What will regulate the activity Ribonucleotide Reductase?
ATP and dATP
What it the target of the Anticancer Drug 5’ Flurouracil ?
Thymidylate Synthase (Deoxynucleotide Synthesis)
What is the purpose of the LDH reaction in the Hard* working skeletal Muscle?
Elevating of NAD+ amount in order to allow more Electron carrying in Mitochondria for Oxidation and ATP production.
Ketoacidosis could be formed by a Deficiency of which enzyme (common in DM1)?
Pyruvate Carboxylase Deficiency - Enhanced PDH Substrate.
Cause for Systemic Primary Carnitine Deficiency:
OCTN2 Transporter Impaired
Other than Ketoacidosis what other outcomes arise from Pyruvate Carboxylase Deficiency?
Lactic Acidosis - Enhanced LDH Substrate
What are the 6 Basic Enzyme Classes?
1) Transferases
2) Ligases
3) Oxidoreductases
4) Isomerases
5) Lyases
6) Hydrolases
L-DOPA is an intermediate of which Conversion?
Might be a treatment for which patients?
Tyrosine to Epinephrine.
Coma Patients.
Name 2 Primary Bile Acids:
Where are they synthesized?
1)Cholic Acid
2)Chenodeoxycholic Acid
In the Liver
In Enzyme kinetics what is the name of an Effector protein that:
- Give rise to a Sigmoidal V0 to [S] Plot.
- Composed of Several Subunits.
- Can Activate or Inhibit an Enzyme by binding and creating a confrontational change.
Allosteric Regulator
What is the function of 5’ Nucleotidase Enzyme?
Catabolism of Pyrimidines:
Nucleotide to Nucleoside.
True for Dissolution of Fibrin :
1) Plasmin hydrolyzes the bonds converting the fibrin monomers.
2) Leukocytes participate in this process
3) cleavage of the Lys-Gln isopeptide bond is Prequisite for dissolution
4) Multiple peptide bonds within the fibrin monomers are hydrolyzed.
5) a possible FDP is D-Dimers.
2 , 4 , 5
In the SAM Cycle, SAH will be hydrolyzed to which 2 components?
Homocysteine and Adenosine
Enzymes for Synthesis of Estrogen from Cholesterol (by order):
1) CYP11 Hydroxylase
2) CYP17 Hydroxylase
3) Sulfonyltransferase
4) Aromatase
Precursors of the Biosynthesis of Pyrimidine Ring:
1) Aspartate
2) Glutamine
3) CO2 from respiration
Gilbert syndrome: Causes and symptoms
Unconjugated Bilirubin in Blood caused by deficiency in UDP glucuronosyl transferase (UGT)
Acyl-CoA Dehydrogenase:
Location, Coenzyme, Activity, Deficiency
Mitochondria
FAD
Trans-Double Bond Formation on FA
No Ketone bodies Production
What stabilizes the T state of hemoglobin?
2,3 BPG
Molecular Background of APC Resistance:
FV and FXIIIa inactivation by APC is Impaired due to mutation amino acid sequence change.
Lactose structure : Bond and Components
Galactose and Glucose Connected by Beta 1-4 Glycosidic Bond
Enzyme that produce GTP in the TCA Cycle?
Succinyl-CoA Synthetase
Definition of Michaelis-Menten constant:
Km shows the concentration of the substrate when the reaction velocity is equal to one half of the maximal velocity for the reaction. It can also be thought of as a measure of how well a substrate complexes with a given enzyme, otherwise known as its binding affinity.
UDP-Glucose Phosphorylase Reaction:
Glucose-1-P + UTP -> UDP-Glucose + PPi
Enzymes of Glycolysis catalyzing the formation of ATP:
Pyruvate Kinase and Phosphoglycerate Kinase
Phenylketonuria: Which Enzyme Deficiency?
Phenylalanine Hydroxylase (Dihydrobiopterine is the cofactor). Produces Tyrosine.
Which of the Following Enzymes: A)Hormone Sensitive Lipase B)Pancreatic Lipase C)Lipoprotein Lipase is active in Adipocytes while working-out? What activates it?
Hormone Sensitive Lipase (HSL) .
Activated by Beta-2-adrenergic Receptor ligand binding.
Name at least 3 elements of the Microsomal drug system?
1) Cytochrome B5
2) NADPH
3) Cytochrome p450 Isoenzymes
Malonyl-CoA inhibits…
Carnitine Palmitoyl Transferase 1 (CPT1)
Aka
Carnitine Acyl Transferase 1 (CAT1)
What is the Chemotherapeutic agent that inhibits Dihydrofolate Reductase?
Methotrexate (MTX)
3 Targets Against Artherosclerosis
1) HMG-CoA Reductase
2) NPC1L1
3) CETP
Inhibitors of PDH:
1) Acetyl-CoA
2) NADH
3) ATP
4) Glucagon
5) FA and Ketone Bodies
Enzyme Catalyzing Glucuronidation?
Cofactor?
UDP- Glucoronosyl Transferase (UGT)
Coenzyme UDP glucoronidate
Catalytic Triad of Serine Porteases Contains:
1) Asp
2) Glu
3) His
4) Ser
5) Tyr
Catalytic triangle Amino acids:
Ser-His-Asp
What are the two states of Hemoglobin?
Relaxed and Tensed - R= Oxy and T =Deoxy
Which of the Following Enzymes: A)Hormone Sensitive Lipase B)Pancreatic Lipase C)Lipoprotein Lipase is active in capillaries of a working Skeletal Muscle? What activates it?
Lipoprotein Lipase - Activated by Epinephrine
What is the Enzyme missing for TAG synthesis in Adipocytes which is present in the Liver?
What are the key Enzymes helps avoiding the need of the First one?
Glycerol Kinase (in Liver). PEPCK and Glycerol-3-Phosphate Dehydrogenase - They are the most important points in Glyceroneogenesis.
Common amino acids of the beta turn?
Proline and Glycine
How is SAM formed in the SAM Cycle?
Methionine + ATP give off:
S-Adenosyl-Methionine + Pyrophosphate +Pi
Enzyme: SAM Synthase (aka Methionine Adenosyltransferase)
What is the Cori Cycle pathway?
Lactate(Muscle) -> Lactate(Liver) -> Glucose(Liver) -> Glucose(Muscle) -> Lactate(Muscle) again and again…
Pyruvate Kinase Activators and Inhibitors
Activator: Fructose-1,6-Bisphosphate
Inhibitors: ATP, cAMP, Phosphorylation (PKA - Glucagon) and Alanine
Isoelectric Point Defenition:
The pH at which a particular molecule carries no net electrical charge or is electrically neutral in the statistical mean
How do Endothelial Cells inhibit Platelet Activation:
1) PGI2
2) Ecto-ADPase on their surface
3) NO
True for the initiation of Blood coagulation:
1) TF in contact with blood
2) by conversion of Prothrombin to Thrombin
3) Activation of FXII
4) by conversion of FX to FXa by FVIIa
All
Total Oxidation of 1 mole of Palmitate - Amount of ATP?
108 ATPs
