1. Which sentence best defines signal transduction in a
a. Alteration of cell functions in response to the environment
b. Generation of a chemical change in response to information
c. Induction of cell death upon nutrient starvation
d. Responses to stimuli
2. Which statement is correct?
a. G protein-coupled receptors produce second messengers indirectly while receptor enzymes catalyse second messenger generation
b. Second messengers stimulate the activity of G protein-coupled receptors.
c. Receptor enzymes produce second messengers through activation of G protein-coupled receptors.
d. Receptor enzymes do not catalyse second messenger generation
3. What second messenger is bound by calmodulin?
4. cAMP is degraded by:
a. Adenylate cyclase
c. Cyclic nucleotide phosphodiesterase
d. Protein kinase C
5. G-protein coupled receptors contain:
a. Tyrosine kinase activity
b. Adenylate cyclase activity
c. No cell surface receptor domain
d. 7 transmembrane helices
6. How can G-protein coupled receptor signalling be turned off?
a. Hydrolysis of GTP bound to Gs
b. Activation of adenylate cyclase
c. Formation of cAMP
d. Hydrolysis of GTP bound to Gi
7. Phosphatidylinositol 4,5-bisphosphate is converted into inositol 1,4,5-trisphosphate and diacylglycerol by:
b. Protein kinase C
d. Phospholipase C
8. Pertussis toxin:
a. Prevents GDP release from Gi, causing increased cAMP synthesis
b. Prevents GDP release from Gi, inhibiting adenylate cyclase
c. Decreases Gs binding of GTP, causing increased cAMP synthesis
d. Degrades adenylate cyclase
9. The β subunit of the insulin receptor:
a. Is located on the extracellular side of the membrane
b. Binds to insulin
c. Contains a tyrosine kinase domain
d. Activates Gs binding of GTP
10. Which of the following statements is true?
a. Intracellular [K+] > extracellular [K+]
b. Intracellular [Na+] > extracellular [Na+]
c. Intracellular [Ca2+] > extracellular [Ca2+]
d. Intracellular [Cl-] > extracellular [Cl-]
11. Which statement is incorrect?
a. Na+K+ ATPase maintains a transmembrane electrical potential
b. Binding of acetylcholine to its receptor allows the allosteric gating of a Na+ channel
c. Binding of acetylcholine to its receptor blocks the opening of a voltage-gated Na+ channels.
d. The direction of spontaneous Na+ movement is into the cell
12. Where is the ligand-binding domain of receptor tyrosine kinases found?
a. Within the endoplasmic reticulum
b. On the extracellular side of the plasma membrane
c. On the cytosolic side of the plasma membrane
d. In the nucleus
13. Activated IRS-1 is bound
a. By activated adenylate cyclase
b. By the SH2 domain on GRB2
c. By insulin
d. By GTP-bound Ras.
14. Which symptoms are not characteristic of diabetes mellitus?
a. Excessive thirst, frequent urination
b. Overproduction of ketone bodies
c. Inefficient uptake of blood glucose
d. Massive fluid and Na+ electrolyte efflux
15. Type I (insulin-dependent) diabetes mellitus:
a. Is caused by mutations in the gene that encodes the insulin receptor
b. Is caused by impaired insulin receptor signalling
c. Is caused by insufficient insulin production by the pancreatic β cells
d. Is caused by mutations in the gene that encodes IRS-1.
16. Which reactions take place during photosynthesis?
a. Water is oxidized to produce O2 and to form NADH + H+
b. The light reaction in Photosystem II takes place to produce luminescence in chloroplast of plants.
c. Photolysis of water to produce O2 and NADP+ is reduced to form NADPH + H+
d. NADPH + H+ is photolysed to form NADH + H+ and inorganic phosphate.
17. Which chemical group and ions are required for the activity of Chlorophyll?
a. Chlorophyll contains Porphyrin and Fe2+.
b. Chlorophyll contains Porphyrin and Mg2+.
c. Chlorophyll contains a iron-sulfur group and Mg2+.
d. Chlorophyll contains Heme and Fe3+.
18. The formation of Citrate from Oxaloacetate and Acetyl CoA is regulated by:
a. Malate, NADH and FAD
b. ATP, NADH and Citrate
c. Glucose, Acetic Acid and ATP
d. This step is regulated by none of the above.
19. The conversion of succinyl-CoA to succinate produces:
a. One ATP and one NADH and H+.
b. One ATP plus one CoASH.
c. One GTP plus one CoASH.
d. No ATP at all but requires the activation through ATP hydrolysis.
20. What does the term ‘chemiosmotic coupling’ mean?
a. A pH gradient across the endoplasmatic reticulum exists and is used for protein transport.
b. A pH gradient across the inner mitochondrial membrane exists and is used to synthesise ATP.
c. A voltage gradient across the outer mitochondrial membrane exists and is used to synthesise NADPH.
d. The photosynthesis in chloroplast and the ATP synthesis in mitochondria are coupled by a voltage gradient.
21. The cofactor cytochrome C of the mitochondrial electron transfer system consists of:
a. DNA and iron
b. RNA and amino acids
c. Iron and amino acids
d. Amino acids and ribose
22. The oxidation of succinate forms:
a. Fumarate plus NADH + H+
b. Oxaloacetate plus NADH + H+
d. Citrate plus FADH2
c. Fumarate plus FADH2
23. How many ATP molecules are generated during oxidative phosphorylation per FADH2 molecule?
a. 1 molecule of ATP
b. 1.5 molecules of ATP
c. 2.5 molecules of ATP
d. 1.5 molecules of GTP
24. In the Citric Acid Cycle NAD+ is:
a. Oxidised to form NADPH + H+
b. Oxidised to form NADH + H+
c. Oxidised to form FADH2
d. Reduced to form NADH + H+
25. Which of the following enzymes is active in the ‘Oxidative Phosphorylation’ process?
a. Glucose oxidase
b. Pyruvate dehydrogenase
c. NADH-CoQ oxidoreductase
26. What is the role of mitochondrial ATP synthase?
a. It hydrolyses ATP during gluconeogenesis
b. It produces ATP using the electrochemical potential of the plasma membrane.
c. It synthesises ATP using the electrochemical potential of mitochondria, ADP and inorganic phosphate.
d. It phosphorylates glucose using GTP as a substrate.
27. During photosynthesis the light harvesting reactions takes place …
a. in two steps using two different photosystems, photosystem I and II.
b. in chloroplast using the ATP synthase and light.
c. in chloroplasts using photosystem I, mitochondrial ATP synthase plus light for its reactions.
d. in chloroplast using photosystem I alone but not photosystem II.
28. What is important for the structure of iron-sulfur proteins?
a. amino acids, heme and ribose
b. iron, amino acids and sulfur but no heme
c. iron, ribose and sulfur but no heme
d. iron, amino acids and sulfur plus heme
29. The oxidation of Succinate to Fumarate produces:
a. the same amount ATP as the oxidation of Malate to Oxaloacetate.
b. more ATP than the oxidation of Malate to Oxaloacetate.
c. no ATP at all but requires the activation through ATP hydrolysis.
d. less ATP than the oxidation of Malate to Oxaloacetate.
30. How many ATP equivalents in total are produced per Acetyl CoA during Citric Acid Cycle including the oxidative phosphorylation and mitochondrial ATP synthase reactions?
a. 10 ATP
b. 9 ATP
c. 8 ATP
d. No ATP at all, only one GTP
30 questions can’t be asked in a single post. I am committed to answer the first four questions. Kindly ask rest in the next post.
Response to stimulus best defines signal transduction. Receptors activate the downstream messengers on identifying the stimulus.
G-protein coupled receptors get activated and in turn use receptor enzymes for production of second messengers.
Calmodulin function with calcium as its second messenger.
Cyclic nucleotide phosphodiesterase catalyzes degradation of cAMP.
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