Biochem

Question 1

Which hormone increases water absorption in the kidneys? A. Aldosterone B. Androgens C. Cortisol D. PTH E. Calcitonin

Answer 1

Aldosterone

Question 2

ACTH stimulates the secretion of which of the following? A. Glucocorticoids B. Epinephrine C. Thyroxine D. Luteinizing hormone

Answer 2

Glucocorticoids

Question 3

Which of the following is false information about growth hormone? A. Acts on the liver, stimulating it to release several polypeptide hormones B. Stimulates amino acid uptake and protein synthesis in target cells C. Stimulates cell growth (cell size and number), especially in muscle and bone D. It has no role in fat breakdown E. Stimulates protein synthesis

Answer 3

has no role in fat breakdown

Question 4

Steroid hormone precursors are converted to active hormones and diffuse out of the parent cell by which of the following pathways? A. Simple diffusion B. Facilitated diffusion C. Exocytosis D. Carrier proteins E. Na+-K+ ion channels

Answer 4

Simple diffusion

Question 5

Increased reabsorption of water from the kidney is the major consequence of which of the following hormones? A. Cortisol B. Insulin C. Vasopressin
D. Aldosterone E. Glucagon

Answer 5

Vasopressin

Question 6

Which of the following is the pituitary hormone that triggers the release of thyroid hormone from the thyroid gland? A. Thyroid stimulating hormone (TSH) B. Adrenocorticotropic hormone (ACTH) C. Follicle stimulating hormone (FSH) D. Luteinizing hormone (LH) E. Growth hormone (GH)

Answer 6

Thyroid stimulating hormone (TSH)

Question 7

Growth hormone is released by which of the following? A. Somatostatin B. Growth hormone releasing hormone C. Prolactin release inhibiting hormone D. Luteinizing releasing hormone

Answer 7

Growth hormone releasing hormone

Question 8

ACTH stimulates the secretion of which of the following? A. Glucocorticoids B. Epinephrine C. Thyroxine D. Luteinizing hormone

Answer 8

Glucocorticoids

Question 9

Beta-cells of islet of Langerhans of the pancreas secrete which hormone? A. Insulin B. Glucagon C. Somatostatin D. Pancreatic polypeptide

Answer 9

Insulin

Question 10

Which is the target tissue of insulin? A. Red blood cells B. Renal tubular cells C. GI tract epithelial cells D. Liver

Answer 10

D. Liver

Question 11

Untreated diabetes mellitus results in what condition? A. Rapid uptake of sugar B. Low blood glucose level C. Decrease urine output D. Presence of glucose in urine

Answer 11

Presence of glucose in urine

Question 12

Changes in what condition increase the primary stimulus for insulin secretion? A. Blood level of epinephrine B. Blood level of glucagon C. Blood level of glucose D. Water intake

Answer 12

Blood level of glucose

Question 13

Hormone receptors possess all the following properties except which one? A. All of them are proteins B. They possess a recognition domain C. They bind hormones with a high degree of specificity D. Number of receptors in a target cell is constant

Answer 13

D. Number of receptors in a target cell is constant

Question 14

Melatonin is synthesized in which part of the body? A. Hypothalamus B. Posterior pituitary gland C. Pineal gland D. Melanocytes

Answer 14

Pineal gland

Question 15

Which hormone is secreted from anterior pituitary? A. Growth hormone B. Vasopressin C. Oxytocin D. Epinephrine E. Glucagon

Answer 15

Growth hormone

Question 16

Which of the following is not one of the anterior pituitary hormones? A. Growth hormone B. Thyroid stimulating hormone C. Adrenocorticotropic hormone
D. Antidiuretic hormone E. Gonadotropins

Answer 16

Antidiuretic hormone

Question 17

Acromegaly results due to excessive release of which of the following? A. Thyroxine B. Growth hormone C. Insulin D. Glucagon E. Noradrenaline

Answer 17

Growth hormone

Question 18

ACTH stimulates the secretion of which of the following? A. Glucocorticoids B. Prolactin C. Thyroxine D. Luteinizing hormone E. Oxytocin

Answer 18

Glucocorticoids

Question 19

Epinephrine stimulates glycogenolysis in which organ? A. Liver B. Muscle C. Liver and muscle D. Kidney E. Brain

Answer 19

Liver and muscle

Question 20

Excess secretion of thyroid hormones causes what disease state? A. Hyperthyroidism B. Myxoedema C. Cretinism D. Cushing syndrome E. Dwarfism

Answer 20

Hyperthyroidism

Question 21

-cells of islet of Langerhans of the pancreas secrete which hormone? A. Insulin B. Glucagon C. Somatostatin
D. Pancreatic polypeptide E. Triiodotronine

Answer 21

Insulin

Question 22

A 43-year-old man comes to the emergency room with a headache and blurred vision. He complains that his wedding ring no longer fits him, and that his favorite hat no longer fits on his head. His wife feels that his nose has become wider, and he is diagnosed acromegaly. Which of the following metabolic effects would you expect in this patient? A. Decreased protein synthesis B. Inhibition of gluconeogenesis C. Inhibition of lipolysis D. Increased protein synthesis E. Gigantism

Answer 22

Increased protein synthesis

Question 23

A 13-year-old boy has developed polydipsia, polyuria, polyphagia, and weight loss over the past few weeks. He was brought to the emer- gency room by his parents because he woke up this morning very lethargic. His blood glucose was found to be 600 mg/dL, and he was immediately placed on an insulin drip. Insulin works primarily by which one of the following mechanisms? A. Activating adenylate cyclase B. Binding to an intracellular receptor C. Activating caspases D. Producing cGMP A. Causing phosphorylation of tyrosine residues

Answer 23

Causing phosphorylation of tyrosine residues

Question 24

What molecules enable cells to respond to a specific extracellular signalling molecule? A. Specific receptor carbohydrates localized to the inner plasma membrane surface B. Plasma lipid bilayer C. Ion channels D. Receptors that specifically recognize and bind that particular messenger molecule E. Intact nuclear membranes

Answer 24

Receptors that specifically recognize and bind that particular messenger molecule

Question 25

Indicate the term generally applies to the extracellular messenger molecules that bind to transmembrane receptor proteins. A. Competitive inhibitor B. Ligand C. Scatchard curve D. Substrate E. Cofactor

Answer 25

Ligand

Question 26

Regardless of how a signal is initiated, the ligand-binding event is propagated via second messengers or protein recruitment. What is the ultimate, or final biochemical outcome of these binding events? A. A protein in the middle of an intracellular signaling pathway is activated B. A protein at the bottom of an intracellular signaling pathway is activated C. A protein at the top of an extracellular signaling pathway is activated D. A protein at the top of an intracellular signaling pathway is deactivated E. A protein at the top of an intracellular signaling pathway is activated

Answer 26

A protein at the bottom of an intracellular signaling pathway is activated

Question 27

What features of the nuclear receptor superfamily suggest that these proteins have evolved from a common ancestor? A. They all bind the same ligand with high affinity B. They all function within the nucleus C. They are all subject to regulatory phosphorylation. D. They all contain regions of high amino acid sequence similarity/identity E. They all bind DNA

Answer 27

They all contain regions of high amino acid sequence similarity/identity

Question 28

What effect does degradation of receptor-ligand complexes after internalization have upon the ability of a cell to respond if immediately re-exposed to the same hormone? A. The cellular response is attenuated due to a decrease in cellular receptor number B. Cellular response is enhanced due to reduced receptor-ligand competition. C. The cellular response is unchanged to subsequent stimuli D. Cell hormone response is now bimodal; enhanced for a short time and thereafter inactivated

Answer 28

The cellular response is attenuated due to a decrease in cellular receptor number

Question 29

Typically, what is the first reaction after most receptor protein-tyrosine kinases (RTKs) bind their ligand? A. Receptor trimerization B. Receptor degradation C. Receptor denaturation D. Receptor dissociation E. Receptor dimerization

Answer 29

Receptor dimerization

Question 30

Where is the kinase catalytic domain of the receptor protein-tyrosine kinases found? A. On the extracellular surface of the receptor, immediately adjacent to the ligand-binding domain B. On the cytoplasmic domain of the receptor C. On an independent protein that rapidly binds the receptor upon ligand binding D. Within the transmembrane spanning portion of the receptor

Answer 30

On the cytoplasmic domain of the receptor

Question 31

The subunits of the heterotrimeric G-proteins are called the __, __, and__ subunits. A. α, β, and χ B. α, β, and δ C. α, γ, and δ D. α, β, and γ E. γ, δ, and η

Answer 31

α, β, and γ

Question 32

Of the receptors listed below, which can directly conduct a flow of ions across the plasma membrane when bound to their cognate ligand? A. Receptor tyrosine kinases (RTKs) B. G-protein–coupled receptors (GPCRs) C. G-protein gamma α subunit. D. Steroid hormone receptors E. Ligand-gated channels

Answer 32

Ligand-gated channels

Question 33

Which of the following is not a natural ligand that binds to G protein–coupled receptors? A. Hormones B. Steroid hormones C. Chemo attractants D. Opium derivatives E. Neurotransmitters

Answer 33

Steroid hormones

Question 34

Place the events of signalling listed below in the correct order. 1. G-protein binds to activated receptor forming a receptor–G-protein complex 2. Release of GDP by the G-protein 3. Change in conformation of the cytoplasmic loops of the receptor 4. Binding of GTP by the G-protein 5. Increase in the affinity of the receptor for a G-protein on the cytoplasmic surface of the membrane 6. Binding of a hormone or neurotransmitter to a G-protein–coupled receptor 7. Conformational shift in the α subunit of the G-protein A. 6 – 3 – 5 – 1 – 2 – 4 – 7 B. 6 – 5 – 4 – 1 – 7 – 2 – 3 C. 6 – 3 – 5 – 1 – 7 – 2 – 4 D. 6 – 7 – 3 – 5 – 1 – 2 – 4 E. 6 – 3 – 5 – 4 – 7 – 2 – 1

Answer 34

6 – 3 – 5 – 1 – 7 – 2 – 4

Question 35

Which heterotrimeric G-proteins couple receptors to adenylyl cyclase via the activation of GTP-bound Gα subunits? A. Gs family B. Gq family C. Gi family D. G12/13 family E. Gx family

Answer 35

Gs family

Question 36

What must happen to prevent overstimulation by a hormone? A. Hormones must be degraded B. G-proteins must be recycled and then degraded C. Receptors must be blocked from continuing to activate G-proteins D. Receptors must dimerize

Answer 36

Receptors must be blocked from continuing to activate G-proteins

Question 37

Which hormone is secreted by α cells in the pancreas in response to low blood glucose levels? A. Insulin B. Glucagon C. Estradiol D. Epinephrine E. Somatostatin

Answer 37

Glucagon

Question 38

In liver cells, the expression of genes encoding gluconeogenic enzymes such as phosphoenolpyruvate carboxykinase is induced in response to which of the following molecules? A. cGMP B. Insulin C. ATP D. cAMP E. Cholesterol

Answer 38

cAMP

Question 39

What happens to protein kinase A (PKA) following the binding of cAMP? A. The regulatory subunits of PKA dissociate, thereby activating the catalytic subunits B. PKA catalytic subunits then bind to two regulatory subunits, thereby activating the catalytic subunits. C. The inhibitory regulatory subunits dissociate from the catalytic subunits, completely inactivating the enzyme D. The stimulatory regulatory subunits dissociate from the catalytic subunits, inhibiting the enzyme E. Phosphodiesterase binds to the catalytic subunits, which results in enzyme inactivation

Answer 39

The regulatory subunits of PKA dissociate, thereby activating the catalytic subunits

Question 40

Thyroid hormones are intimately involved in regulating the basal metabolic rate. Choose the wrong statement. A. Excess thyroxine shows an increased rate of O2 consumption. B. Excess thyroxine shows increased heat output (thermogenesis) C. Excess thyroxine decreases the ATP concentration in the tissue D. Excess thyroxine causes uncoupling of oxidative phosphorylation in mitochondria E. Thermogenesis is due to an increased rate of ATP utilization by the thyroxine-stimulated tissue

Answer 40

Excess thyroxine decreases the ATP concentration in the tissue

Question 41

If a single gene contains information for synthesis of more than one hormone molecule which statement is correct? A. All the hormones are produced by any tissue that expresses the gene B. All hormone molecules are identical C. Cleavage sites in the gene product are typically pairs of basic amino acids D. All peptides of the gene product have well-defined biological activity E. Hormones all have similar function

Answer 41

Cleavage sites in the gene product are typically pairs of basic amino acids

Question 42

In the interaction of a hormone with its receptor, all of the following are true except which one? A. More than one polypeptide chain of the hormone may be necessary B. More than one second messenger may be generated C. An array of transmembrane helices may form the binding site for the hormone D. Receptors have a greater affinity for hormones than for synthetic agonists or antagonists E. Hormones released from their receptor after endocytosis could theoretically interact with a nuclear receptor.

Answer 42

Receptors have a greater affinity for hormones than for synthetic agonists or antagonists

Question 43

Some hormone-receptor complexes are internalized by endocytosis. This process may involve which of the following? A. Binding of hormone-receptor complex to a clathrin coated pit B. Recycling of receptor to cell surface C. Degradation of receptor and hormone in lysosomes D. Formation of a receptosome E. All of the above

Answer 43

All of the above

Question 44

Binding of insulin to its receptor occurs on/results in which of the following? A. Occurs on the β-subunit B. Induces autophosphorylation C. Reduces binding of cytosolic substrate proteins D. Leads only to phosphorylation of proteins E. Does not lead to release of a second messenger

Answer 44

Induces autophosphorylation

Question 45

All the following are normal events leading to secretion of aldosterone from the adrenal gland except which one? A. Renin is released by the kidney in hypovolemia B. Angiotensinogen binds to membrane receptors C. The PI cycle is activated producing IP3 and DAG D. Ca2+ levels in the cell rise E. Aldosterone is secreted into the blood

Answer 45

Angiotensinogen binds to membrane receptors

Question 46

In hypopituitarism the ovarian cycle would be affected because of the following events? A. FSH and LH are synthesized in the anterior pituitary B. Gonadotropin-releasing hormone (GnRH) from the hypothalamus stimulates the release of FSH and LH C. Inhibins would be secreted in much larger than normal amounts D. The corpus luteum would be maintained E. GnRH would bind co receptors to activate protein kinase A

Answer 46

FSH and LH are synthesized in the anterior pituitary

Question 47

The PI cycle begins with activation of phospholipase C; this initiates a sequence of events including all of the following except which one? A. Activation of IP3 by action of a phosphatase B. Increase in intracellular Ca2+ concentration C. Release of diacylglycerol (DAG) D. Activation of protein kinase C E. Phosphorylation of certain cytoplasmic proteins

Answer 47

Activation of IP3 by action of a phosphatase