Question
ADH plays a key role in osmoregulation. When the blood’s solute concentration is above normal, the pituitary gland releases ADH.
Which statement explains how ADH helps to reduce the solute concentration of blood?
A. It increases ultrafiltration of solutes in the glomerulus, so blood becomes more diluted.
B. It increases reabsorption of sodium ions in the loop of Henle, so less water is excreted.
C. It causes selective reabsorption of some solutes in the distal convoluted tubule.
D. It changes the collecting duct’s permeability to water to produce more concentrated urine.
▶️Answer/Explanation
Answer: D. It changes the collecting duct’s permeability to water to produce more concentrated urine.
Explanation:
What is ADH and its role in osmoregulation?
ADH (antidiuretic hormone), also called vasopressin, is released by the pituitary gland when the blood has too little water (i.e. high solute concentration). Its main function is to increase the reabsorption of water in the kidneys specifically in the collecting ducts making the urine more concentrated and the blood more diluted.
Evaluation of Each Option:
A. Incorrect – Ultrafiltration happens in the glomerulus, but ADH does not affect this process. Ultrafiltration is a pressure-based process, not regulated by ADH.
B. Incorrect – ADH does not affect sodium ion reabsorption in the loop of Henle. That’s mainly controlled by aldosterone, another hormone.
C. Incorrect – ADH mainly acts on the collecting duct, not on selective solute reabsorption in the distal convoluted tubule.
D. Correct – ADH increases the permeability of the collecting duct walls to water by triggering insertion of aquaporins. This causes more water to be reabsorbed into the blood, concentrating the urine and diluting the blood (reducing its solute concentration).
Question
What sequence shows the route taken by nitrogenous wastes in insects from their production in body cells to their removal from the insect’s body?
A. Hemolymph → Malpighian tubule → hindgut → rectum
B. Hindgut → hemolymph → kidney tubule → bladder
C. Malpighian corpuscle → nephron → ureter → bladder
D. Neonicotinoid → rectum → antagonistic muscles → anus
▶️Answer/Explanation
Answer: A. Hemolymph → Malpighian tubule → hindgut → rectum
Explanation:
How do insects excrete nitrogenous waste?
Insects excrete nitrogenous waste (like uric acid) through a specialized excretory system involving Malpighian tubules. These tubules remove waste from the hemolymph (insect blood) and pass it into the hindgut, where water and useful solutes may be reabsorbed. The remaining waste is excreted through the rectum.
Evaluation of Each Option:
A. Correct: Hemolymph → Malpighian tubule → hindgut → rectum
This is the correct pathway for nitrogenous waste in insects. The Malpighian tubules extract waste from hemolymph and deliver it to the hindgut, where final excretion occurs via the rectum.
B. Incorrect: Mentions kidney tubule and bladder, which are vertebrate (human) structures, not found in insects.
C. Incorrect: This option references Malpighian corpuscle, nephron, and ureter, all human/vertebrate kidney structures not relevant to insect excretion.
D. Incorrect: “Neonicotinoid” is a pesticide, not a waste product or anatomical structure. This answer is nonsensical in the context of insect excretion.
Question
Where in the nephron is most glucose reabsorbed?
▶️Answer/Explanation
Answer: B
Explanation:
A. Bowman’s Capsule (and Glomerulus)
- Function: This is the site of filtration. Blood enters through the afferent arteriole and is filtered in the glomerulus. Water, glucose, salts, amino acids, and urea are filtered into the Bowman’s capsule.
- Important note: No reabsorption occurs here this is the starting point of the filtrate in the nephron.
B. Proximal Convoluted Tubule (PCT)
- Function: This is where most reabsorption occurs, including:
- ~100% of glucose and amino acids
- A significant amount of water and salts (e.g., Na⁺, Cl⁻)
- Why it matters: This is the correct answer to your original question—glucose is mainly reabsorbed here through active transport.
C. Loop of Henle
- Function:
- Descending limb: Reabsorbs water.
- Ascending limb: Reabsorbs salts (Na⁺, Cl⁻) but is impermeable to water.
- Role: Creates a concentration gradient in the medulla to help concentrate urine.
- Not involved in glucose reabsorption.
D. Distal Convoluted Tubule (DCT)
- Function:
- Fine-tunes salt and pH balance
- Controlled reabsorption of Na⁺ and Ca²⁺ under hormonal influence (e.g., aldosterone)
- Minor role in water and salt reabsorption compared to the PCT.
- No glucose reabsorption here.
Question
Glucose moves from the filtrate in the nephron into the bloodstream during normal kidney function. Which location and method describe this movement of glucose?
▶️Answer/Explanation
Answer: D
Explanation:
Glucose is reabsorbed from the filtrate back into the blood in the proximal convoluted tubule of the nephron by active transport, which requires energy.
Option Evaluation:
A. Incorrect – This is where glucose is filtered out of the blood, not reabsorbed.
B. Incorrect – Correct location, but the process is wrong. Reabsorption here uses active transport, not ultrafiltration.
C. Incorrect – The glomerulus uses ultrafiltration, not active transport.
D. Correct – Glucose is reabsorbed here using active transport.