Biology MCQs

Question #1501

In plant anatomy, the 'Vascular cambium' is a lateral meristem responsible for secondary growth (increase in girth) in dicots and gymnosperms. It produces secondary xylem (wood) towards the:

A. Both inside and outside equally

B. Upwards only

C. Outside (periphery)

D. Inside (center)

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
The vascular cambium is a thin layer of meristematic cells located between the primary xylem and primary phloem in the vascular bundles of dicot stems and roots, and in the secondary vascular tissue. It is a lateral meristem that divides periclinally (parallel to the surface). It produces secondary xylem (wood) cells towards the inside (center) of the stem or root, and secondary phloem (inner bark) cells towards the outside (periphery). Since it produces xylem much faster than phloem, the secondary xylem accumulates and forms the bulk of the wood.

This question belongs to: Science Biology

Question #1502

Share Report

The 'Hormone Motilin' is secreted by the M cells of the duodenum and jejunum. Its primary function is to:

A. Stimulate gastric emptying and initiate the migrating motor complex (MMC) in the interdigestive state

B. Inhibit gastric emptying

C. Stimulate insulin release

D. Inhibit pancreatic enzyme secretion

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
Motilin is a peptide hormone secreted by the Mo cells (or M cells) in the crypts of the duodenum and jejunum. Its secretion occurs in cycles during the fasting (interdigestive) state. Its primary function is to stimulate gastric motility and emptying, and to initiate and regulate the Migrating Motor Complex (MMC). The MMC is a pattern of electromechanical activity observed in the gastrointestinal tract during fasting, characterized by waves of contraction that sweep undigested material, bacteria, and sloughed cells from the stomach and small intestine towards the colon, acting as a 'housekeeper'.

This question belongs to: Science Biology

Question #1503

Share Report

In the human body, the 'Cerebrospinal Fluid' (CSF) is a clear, colorless body fluid found in the brain and spinal cord. It is primarily produced by the:

A. Dura mater

B. Pia mater

C. Choroid plexus in the ventricles

D. Arachnoid mater

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option C

Explanation:
Cerebrospinal Fluid (CSF) is a clear, watery fluid that circulates through the ventricles of the brain, the central canal of the spinal cord, and the subarachnoid space. It provides mechanical protection (cushioning), chemical stability, and waste removal for the central nervous system. CSF is primarily produced by the choroid plexus, which is a network of highly vascularized, specialized ependymal cells located within the ventricles of the brain (lateral, third, and fourth ventricles).

This question belongs to: Science Biology

Question #1504

Share Report

The 'Hormone Peptide YY' (PYY) is secreted by the L cells of the distal gastrointestinal tract (ileum and colon) in response to food intake. Its primary function is to:

A. Stimulate gastric acid secretion

B. Inhibit gastric emptying and pancreatic secretion, and reduce appetite (satiety signal)

C. Increase intestinal motility

D. Stimulate appetite

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option B

Explanation:
Peptide YY (PYY) is a gut hormone secreted by the L cells in the mucosa of the distal small intestine (ileum) and colon, primarily in response to food ingestion, especially fats. Its primary functions are related to the 'ileal brake' mechanism: it inhibits gastric emptying and pancreatic exocrine secretion, slowing down the transit of food through the upper GI tract to allow more time for digestion and absorption in the ileum. It also acts on the hypothalamus to reduce appetite, serving as a satiety signal.

This question belongs to: Science Biology

Question #1505

Share Report

In plant physiology, the 'Imbibition' is a special type of diffusion where water is absorbed by solid particles (colloids), causing them to increase in volume. This process is crucial for:

A. The translocation of sugars in the phloem

B. The ascent of sap in tall trees

C. The opening and closing of stomata

D. The initial absorption of water by dry seeds, leading to germination

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
Imbibition is a physical process where solid, hydrophilic (water-loving) colloidal materials (like cellulose, pectin, proteins, and starch) adsorb water, causing a tremendous increase in their volume and generating significant imbibitional pressure. This process is the very first step in seed germination. When a dry seed is exposed to water, its cell walls and storage materials imbibe water, causing the seed to swell, rupturing the seed coat, and initiating the metabolic activities required for the seedling to grow. It is also responsible for the splitting of rocks by plant roots.

This question belongs to: Science Biology

Question #1506

Share Report

The 'Hormone Pancreatic Polypeptide' (PP) is secreted by the F cells (or gamma cells) of the pancreatic islets. Its primary function is to:

A. Increase intestinal motility

B. Inhibit pancreatic enzyme secretion, gall bladder contraction, and gastric emptying

C. Stimulate insulin and glucagon release

D. Stimulate gastric acid secretion

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option B

Explanation:
Pancreatic Polypeptide (PP) is a hormone secreted by the F cells (also known as gamma cells), which are scattered throughout the islets of Langerhans in the pancreas, primarily in the head of the pancreas. Its secretion is stimulated by the ingestion of a meal, particularly one rich in protein. Its primary functions are inhibitory: it inhibits the secretion of pancreatic digestive enzymes, inhibits gall bladder contraction, and slows down gastric emptying. It is thought to regulate the rate of nutrient absorption and prevent over-digestion.

This question belongs to: Science Biology

Question #1507

Share Report

In the human body, the 'Blood-Brain Barrier' (BBB) is highly selective. Which of the following substances can easily cross the BBB?

A. Bacteria and viruses

B. Glucose, oxygen, and carbon dioxide

C. Most water-soluble drugs

D. Large proteins and peptides

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option B

Explanation:
The Blood-Brain Barrier (BBB) is formed by tight junctions between endothelial cells in brain capillaries, making it highly selective. It allows the free diffusion of small, lipid-soluble molecules and essential gases. Therefore, oxygen, carbon dioxide, and lipid-soluble substances (like alcohol, nicotine, and some anesthetics) easily cross. Glucose, a water-soluble molecule essential for brain energy, crosses via specific carrier-mediated transport (GLUT1 transporters). Large proteins, peptides, most water-soluble drugs, and pathogens like bacteria and viruses are generally blocked from entering the brain parenchyma.

This question belongs to: Science Biology

Question #1508

Share Report

The 'Hormone Neurotensin' is a peptide found in the central nervous system and the gastrointestinal tract. In the gut, its primary functions include:

A. Stimulating gastric acid secretion

B. Stimulating insulin release

C. Increasing intestinal absorption of water

D. Inhibiting gastric motility and acid secretion, and stimulating the release of histamine and glucagon

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
Neurotensin is a 13-amino acid peptide that functions as both a neuromodulator in the central nervous system and a hormone in the gastrointestinal tract. In the gut, it is secreted by the N cells in the ileum in response to fat ingestion. Its primary gastrointestinal functions are to inhibit gastric motility and gastric acid secretion (contributing to the 'ileal brake'), and to stimulate the release of histamine from mast cells and glucagon from the pancreas. It also causes vasodilation in the intestinal mucosa.

This question belongs to: Science Biology

Question #1509

Share Report

In plant anatomy, the 'Casparian strip' is a key feature of the endodermis in roots. It is primarily composed of:

A. Suberin and lignin

B. Chitin and peptidoglycan

C. Silica and calcium carbonate

D. Cellulose and pectin

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
The Casparian strip is a band of cell wall material that runs radially and transversely through the cell walls of the endodermal cells in plant roots, but is absent from the tangential walls. It is primarily composed of suberin (a waxy, waterproof substance) and lignin (a complex polymer). This strip acts as a physical and chemical barrier, blocking the passive, apoplastic flow of water and dissolved minerals between the cells. It forces these substances to cross the selectively permeable plasma membrane and enter the symplastic pathway, allowing the plant to control what enters the vascular cylinder.

This question belongs to: Science Biology

Question #1510

Share Report

The 'Hormone Galanin' is a neuropeptide widely distributed in the central nervous system and the gastrointestinal tract. Its functions include:

A. Inhibiting insulin and glucagon release, and inhibiting gastric emptying and intestinal motility

B. Increasing appetite

C. Stimulating gastric acid secretion

D. Stimulating insulin release

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
Galanin is a 29-amino acid neuropeptide that is co-localized with several other neurotransmitters and hormones. In the central nervous system, it is involved in various functions, including the inhibition of acetylcholine release and modulation of pain. In the gastrointestinal tract and pancreas, its primary functions are inhibitory: it inhibits the release of both insulin and glucagon from the pancreatic islets, inhibits gastric emptying and gastric acid secretion, and generally inhibits intestinal motility and secretion. It acts to slow down digestion and nutrient absorption.

This question belongs to: Science Biology

Question #1511

Share Report

In the human body, the 'Pineal gland' is a small endocrine gland located in the epithalamus. It is often referred to as the 'third eye' in some lower vertebrates because:

A. It is photosensitive and regulates circadian rhythms in response to light, and in some reptiles and amphibians, it has a parietal eye structure

B. It produces tears

C. It controls eye movement

D. It can literally see light

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
The pineal gland is a small, pinecone-shaped gland located in the epithalamus, near the center of the brain. In humans, it is not a true eye, but it is photosensitive; it receives information about the light-dark cycle from the retina via the suprachiasmatic nucleus and the sympathetic nervous system, and uses this to regulate the secretion of melatonin, thus controlling circadian rhythms. In some lower vertebrates (like certain reptiles, amphibians, and fish), the pineal complex includes a parietal eye (or 'third eye'), a light-sensitive organ on the top of the head that can literally detect light and shadows, helping with camouflage and predator detection.

This question belongs to: Science Biology

Question #1512

Share Report

The 'Hormone Somatostatin' is a universal inhibitor. In the gastrointestinal tract, it inhibits the release of almost all other GI hormones. It is secreted by the:

A. Delta (D) cells of the pancreatic islets and the D cells of the GI mucosa

B. G cells of the stomach

C. I cells of the duodenum

D. S cells of the duodenum

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
Somatostatin is a powerful, universal inhibitory peptide hormone. In the gastrointestinal tract and pancreas, it is secreted by the Delta (D) cells of the pancreatic islets and the D cells of the gastric and intestinal mucosa. Its primary role in the GI tract is to act as a paracrine inhibitor, suppressing the release of almost all other gastrointestinal hormones, including gastrin, secretin, cholecystokinin (CCK), vasoactive intestinal peptide (VIP), and gastric inhibitory peptide (GIP). It also inhibits gastric acid secretion, pancreatic enzyme secretion, and intestinal motility, acting as a 'brake' on the digestive system.

This question belongs to: Science Biology

Question #1513

Share Report

In plant physiology, the 'Root pressure' is a positive pressure that develops in the roots due to the active absorption of minerals and the subsequent osmotic entry of water. It is most evident during:

A. Early morning or night when transpiration is low and soil moisture is high

B. Mid-day when transpiration is high

C. Drought conditions

D. Winter when the ground is frozen

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
Root pressure is a positive hydrostatic pressure generated in the xylem of roots due to the active secretion of ions into the xylem, which lowers the water potential and causes water to enter osmotically from the soil. This pressure can push water up the stem. Root pressure is most evident and measurable during the early morning or at night, when the rate of transpiration from the leaves is very low (or zero) and the soil moisture is high, allowing for maximum water absorption. It is responsible for phenomena like guttation and the exudation of sap from cut stems.

This question belongs to: Science Biology

Question #1514

Share Report

The 'Hormone Vasoactive Intestinal Peptide' (VIP) is a neuropeptide found in the central nervous system and the gut. Its primary functions in the gut include:

A. Stimulating gall bladder contraction

B. Stimulating gastric acid secretion

C. Inhibiting intestinal motility

D. Stimulating intestinal water and electrolyte secretion, relaxing intestinal smooth muscle, and stimulating pancreatic bicarbonate secretion

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
Vasoactive Intestinal Peptide (VIP) is a 28-amino acid neuropeptide that acts as a neurotransmitter and a hormone. In the gastrointestinal tract, its primary functions are stimulatory and relaxant: it stimulates the secretion of water and electrolytes into the intestinal lumen (acting as a secretagogue), relaxes the smooth muscle of the gut (including the lower esophageal sphincter, stomach, and gall bladder), and stimulates the pancreas to secrete a bicarbonate-rich juice. It also causes vasodilation in the gut. Excessive VIP secretion can lead to severe watery diarrhea (as in VIPoma).

This question belongs to: Science Biology

Question #1515

Share Report

The 'Hormone Glucagon-like Peptide-1' (GLP-1) is an incretin hormone secreted by the L cells of the distal intestine. Its primary functions include:

A. Stimulating glucose-dependent insulin release, inhibiting glucagon release, slowing gastric emptying, and promoting satiety

B. Increasing intestinal motility

C. Stimulating gastric acid secretion

D. Inhibiting insulin release

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
Glucagon-like Peptide-1 (GLP-1) is a powerful incretin hormone secreted by the L cells of the distal small intestine (ileum) and colon in response to food ingestion. Its primary functions are highly beneficial for glucose homeostasis: it stimulates insulin secretion from the pancreas in a glucose-dependent manner (only when blood glucose is high), inhibits glucagon secretion, slows down gastric emptying (allowing more time for nutrient absorption), and acts on the brain to promote satiety and reduce food intake. GLP-1 analogs (like exenatide) are used as drugs to treat type 2 diabetes.

This question belongs to: Science Biology

Question #1516

Share Report

The 'Hormone Amylin' (Islet Amyloid Polypeptide) is co-secreted with insulin by the beta cells of the pancreas. Its primary functions include:

A. Stimulating intestinal motility

B. Increasing gastric acid secretion

C. Slowing gastric emptying, suppressing glucagon secretion, and promoting satiety

D. Stimulating insulin release

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option C

Explanation:
Amylin, also known as Islet Amyloid Polypeptide (IAPP), is a 37-amino acid peptide hormone that is co-secreted with insulin from the pancreatic beta cells in response to meals (in a ratio of about 1:100 to insulin). Its primary functions are to complement the actions of insulin in regulating postprandial (after-meal) glucose levels. It does this by slowing gastric emptying (preventing a rapid spike in blood glucose), suppressing the secretion of glucagon (preventing the liver from releasing glucose), and acting on the brain to promote satiety and reduce food intake.

This question belongs to: Science Biology

Question #1517

Share Report

In the human body, the 'Blood-Brain Barrier' (BBB) is crucial for protecting the brain. However, in certain areas, the BBB is absent or 'leaky' to allow the brain to monitor the composition of the blood. These areas are called:

A. Basal ganglia

B. Circumventricular organs

C. Thalamic nuclei

D. Corpus callosum

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option B

Explanation:
While the Blood-Brain Barrier (BBB) protects most of the brain, there are specific areas where the BBB is absent or highly permeable. These are the circumventricular organs (CVOs), which are located around the third and fourth ventricles. Because they lack a typical BBB, they can directly sample the chemical composition of the blood and cerebrospinal fluid. This is essential for their functions, which include neuroendocrine regulation (e.g., the area postrema for vomiting, the organum vasculosum of the lamina terminalis for osmoregulation, and the median eminence for hormone release).

This question belongs to: Science Biology

Question #1518

Share Report

The 'Hormone Fibroblast Growth Factor 21' (FGF21) is primarily produced by the liver in response to various metabolic stresses. Its primary function is to:

A. Stimulate bone growth

B. Regulate glucose and lipid metabolism, improving insulin sensitivity and promoting fat breakdown

C. Inhibit protein synthesis

D. Stimulate cell division

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option B

Explanation:
Fibroblast Growth Factor 21 (FGF21) is a hormone primarily secreted by the liver (and to a lesser extent by adipose tissue and pancreas) in response to metabolic stresses like fasting, a high-carbohydrate diet, or mitochondrial dysfunction. Its primary functions are to regulate glucose and lipid metabolism. It improves insulin sensitivity, promotes the uptake of glucose by adipose tissue, stimulates the breakdown of fats (lipolysis) and ketogenesis in the liver, and reduces triglyceride levels. It is considered a 'starvation hormone' and a potential therapeutic target for metabolic diseases like diabetes and obesity.

This question belongs to: Science Biology

Question #1519

Share Report

In plant physiology, the 'Osmotic pressure' is the pressure that must be applied to a solution to prevent the inward flow of water across a semipermeable membrane. It is directly proportional to the:

A. Concentration of solute particles

B. Temperature only

C. Volume of the solution

D. Size of the solute molecules

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option A

Explanation:
Osmotic pressure (OP) is a colligative property of a solution, meaning it depends on the number of solute particles dissolved in a given volume of solvent, not on the nature or size of the particles. It is defined as the hydrostatic pressure that must be applied to a solution to prevent the net flow of water (osmosis) into the solution across a semipermeable membrane. According to the van't Hoff equation, osmotic pressure is directly proportional to the molar concentration of solute particles and the absolute temperature. The more concentrated the solution, the higher its osmotic pressure.

This question belongs to: Science Biology

Question #1520

Share Report

The 'Hormone Adiponectin' is a protein hormone secreted exclusively by adipose (fat) tissue. Unlike most other adipokines, its levels are inversely related to body fat. Its primary functions include:

A. Inhibiting glucose uptake

B. Promoting insulin resistance and inflammation

C. Stimulating appetite

D. Enhancing insulin sensitivity, promoting fatty acid oxidation, and having anti-inflammatory effects

View Answer & Solution Discuss

Get Complete Subject PDF for Science

Correct Answer: Option D

Explanation:
Adiponectin is an abundant protein hormone secreted by adipose tissue. Uniquely, its plasma levels are inversely correlated with body fat percentage; obese individuals have lower levels. Its primary functions are highly beneficial for metabolic health: it enhances insulin sensitivity in the liver and muscles, promotes the oxidation of fatty acids (reducing fat accumulation), inhibits glucose production by the liver, and has potent anti-inflammatory and anti-atherogenic effects on the blood vessels. Low levels of adiponectin are associated with insulin resistance, type 2 diabetes, and cardiovascular disease.

This question belongs to: Science Biology

Practice Questions

More Science Topics