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Pre AP Biology -CELLS 4.1 Organ/Tissue Systems- FRQ Exam Style Questions -New Syllabus

Pre AP Biology -CELLS 4.1 Organ/Tissue Systems- FRQ Exam Style Questions – New Syllabus 2025-2026

Pre AP Biology -CELLS 4.1 Organ/Tissue Systems- FRQ Exam Style Questions – Pre AP Biology – per latest Pre AP Biology Syllabus.

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Question

Diabetes is a disease that occurs when your blood glucose, also called blood sugar, is too high. Glucose is your body’s main source of energy. Your body can make glucose, but glucose also comes from the food you eat.
Insulin is a hormone made by the pancreas that helps glucose get into your cells to be used for energy. If you have diabetes, your body does not make enough—or any—insulin, or does not use insulin properly. Glucose then stays in your blood and does not reach your cells.
Diabetes raises the risk of damage to the eyes, kidneys, nerves, and heart.
(a) Explain how the structure of the kidney links to its functions. ($3$ marks)
(b) Explain how diabetes causes high blood glucose levels and justify how uncontrolled diabetes can lead to chronic kidney failure.
A patient visited the nephrologist after being suspected to have Chronic Kidney Failure. They demonstrate symptoms including high blood pressure, less frequent urination and swelling of feet and ankles (oedema).
(c) Explain how a loss of kidney function can lead to one symptom experienced by the patient.

Most-appropriate topic codes (Pre-AP Biology):

• TOPIC: CELLS 4.1 — Organ/Tissue Systems: Animals have organ systems that work together to transport nutrients and excrete waste, including the excretory system for water balance — parts (a), (c)
• TOPIC: CELLS 3.2 — Cell Transport: Movement of materials (like glucose) across the cell membrane to maintain homeostasis — part (b)
• TOPIC: CELLS 1.1 — Biomolecules: Carbohydrates serve as the primary source of energy for organisms — part (b)
• TOPIC: CELLS 4.1 — Organ/Tissue Systems: Predict the consequence of a disruption in homeostasis — parts (b), (c)
▶️ Answer/Explanation
Detailed solution

(a)
The structure of the kidney is intricately linked to its function of filtration and reabsorption through the nephron:

  • Glomerulus and Bowman’s Capsule: The glomerulus is a network of capillaries with high hydrostatic pressure, and the Bowman’s capsule is cup-shaped to collect filtrate. This structure facilitates ultrafiltration of small molecules from the blood.
  • Proximal Convoluted Tubule (PCT): The cells lining the PCT have microvilli which significantly increase the surface area. They are also packed with mitochondria to provide ATP. This structure allows for efficient selective reabsorption of glucose, ions (like $Na^+$), and water back into the blood.
  • Loop of Henle: This long loop extends into the medulla, creating a salt concentration gradient (high osmolarity). This structural arrangement allows for water reabsorption from the collecting duct, ensuring urine concentration.

(b)
High Blood Glucose: Diabetes causes high blood glucose because the body either fails to produce sufficient insulin (Type 1) or the cells become resistant to insulin (Type 2). Since insulin is the “key” that allows glucose to enter cells from the bloodstream, a lack of effective insulin function results in glucose accumulating in the blood (hyperglycemia).

Link to Kidney Failure: The kidneys contain millions of tiny blood vessel clusters called glomeruli that filter waste. High levels of blood sugar can damage these blood vessels and the kidney’s filtration units. Over time, the high workload and direct damage cause the filters to leak (often releasing protein/albumin into urine) and scar (glomerulosclerosis). This damage eventually destroys the kidney’s ability to filter waste from the blood, leading to Chronic Kidney Failure.

(c)
The patient is experiencing swelling of feet and ankles (oedema).
Explanation: One of the primary functions of the kidney is osmoregulation—balancing fluid and salt levels in the body. When kidney function is lost, the kidneys cannot effectively remove excess fluid and sodium ($Na^+$) from the bloodstream. This leads to fluid retention. The excess fluid builds up in the circulatory system and leaks into surrounding tissues. Due to gravity, this fluid accumulation is most visible as swelling in the lowest parts of the body, such as the feet and ankles.

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