Most Repeated MDCAT Biology: Homeostasis MCQs

Explanation

Deamination is the removal of an amino group from a molecule. Enzymes that catalyze this reaction are called deaminases. In the human body, deamination takes place primarily in the liver. The amino group is removed from the amino acid and converted to ammonia.

Explanation

A nephron is a unit of structure and function in a kidney. A kidney contains about a million nephrons, each approximately 3 cm long. A nephron is a long tubule differentiated into four regions having different anatomical features and physiological role : Bowman’s capsule, proximal convoluted tubule (PCT), loop of Henle, and distal convoluted tubule (DCT). The latter opens into one of the collecting ducts. Nephridia are the excretory organs of annelids.

Explanation

Option B is correct.Ureter is the tube that brings urine from kidney to the urinary bladder.So, Option B is correct.Option A: Urethra tube through which urine leaves the body. It empties urine from the bladder.So,Option A is incorrect.Option C: Your uterus is a pear-shaped organ in the female reproductive system. It's where a fertilized egg implants during pregnancy and where the baby develops until birth.

Explanation

Aldosterone is a hormone produced by the adrenal cortex that promotes the reabsorption of sodium ions (Na+) in the distal convoluted tubule and collecting ducts of the nephron. This reabsorption of sodium leads to the retention of water, increasing blood volume and blood pressure. While aldosterone primarily acts on the distal tubule and collecting ducts, it also plays a role in regulating sodium reabsorption in the ascending limb of the Loop of Henle.

Explanation

Sunken stomata are typically found in xerophytes, which are plants adapted to survive in dry, arid environments with limited water availability. These stomata are located in pits or depressions in the epidermis of the plant, which helps to reduce water loss due to evapotranspiration. Xerophytes have evolved various adaptations like thick cuticles and reduced leaf surface area to conserve water. The other options, mesophytes, halophytes, and hydrophytes, are adapted to different environmental conditions and do not typically have sunken stomata.

Explanation

Option C is correct.The correct answer is uric acid, which is the least toxic excretory product. It is excreted in a solid or semi-solid form and conserves water, making it ideal for animals like birds and reptiles living in arid environments. Ammonia, on the other hand, is highly toxic and requires a significant amount of water to be safely excreted, which is why it is typically excreted by aquatic animals. Urea is less toxic than ammonia and is excreted by mammals and amphibians, requiring moderate amounts of water. Fatty acids are not directly involved in nitrogenous waste excretion.

Explanation

Option D is correct.Water excretion by the kidney is regulated by the peptide hormone vasopressin. Vasopressin increases the water permeability of the renal collecting duct cells, allowing more water to be reabsorbed from collecting duct urine to blood.

Explanation

Most of the glucose entering the tubular system is reabsorbed along the nephron segments, primarily in the proximal tubule, such that urine is almost free of glucose. This is different in diabetes, where the filtered glucose exceeds the transport capacity of the tubular system for glucose and glucosuria occurs.

Explanation

On a cold day, the body must maintain a stable core temperature to function properly. The hypothalamus is crucial for this task as it senses changes in body temperature and triggers responses like shivering and vasoconstriction to conserve heat. This makes the hypothalamus the correct answer. In contrast, the kidneys focus on fluid balance, the posterior pituitary on hormone release, and the brainstem on other automatic functions, none of which directly involve temperature regulation.

Explanation

E is the renal cortex. It has the greatest blood flow in the following options. The cortex requires about 80% of blood flow to achieve its excretory and regulatory functions, and the outer medulla receives 15%. The inner medulla receives a small percent of blood flow; a higher flow would wash out solutes responsible for the high tonicity of the inner medulla.