CLEP Biology Organismal Biology & Physiology 2 — Questions and Answers
Question 1: Which structure in the human kidney is responsible for filtering blood to form the initial filtrate?
- Loop of Henle
- Glomerulus (Correct answer)
- Collecting duct
- Distal convoluted tubule
Correct answer: Glomerulus
The glomerulus is the capillary network where blood pressure drives water and small solutes into the Bowman's capsule to form the glomerular filtrate.
Question 2: What is the primary function of the loop of Henle in the nephron?
- Secreting hydrogen ions into the filtrate
- Creating an osmotic gradient in the renal medulla (Correct answer)
- Reabsorbing glucose into the bloodstream
- Producing erythropoietin
Correct answer: Creating an osmotic gradient in the renal medulla
The loop of Henle establishes a hyperosmotic gradient in the renal medulla that allows the collecting duct to concentrate urine.
Question 3: In flowering plants, which tissue transports sugars produced by photosynthesis from leaves to other parts of the plant?
- Xylem
- Phloem (Correct answer)
- Epidermis
- Cortex
Correct answer: Phloem
Phloem conducts organic compounds such as sucrose from source tissues (leaves) to sink tissues (roots, fruits) via pressure-flow.
Question 4: Which type of muscle tissue is under involuntary control and found in the walls of the digestive tract?
- Cardiac muscle
- Skeletal muscle
- Smooth muscle (Correct answer)
- Striated muscle
Correct answer: Smooth muscle
Smooth muscle is non-striated, involuntary, and lines hollow organs such as the intestines where it drives peristalsis.
Question 5: What hormone do chief cells of the stomach secrete, and what is its function?
- Pepsin; digests carbohydrates
- Pepsinogen; is activated to pepsin which digests proteins (Correct answer)
- Gastrin; stimulates HCl secretion by parietal cells
- Lipase; digests fats in the stomach
Correct answer: Pepsinogen; is activated to pepsin which digests proteins
Chief cells secrete pepsinogen, an inactive zymogen that hydrochloric acid converts to pepsin, which cleaves dietary proteins.
Question 6: Which layer of the skin contains the melanocytes that produce melanin?
- Stratum corneum
- Stratum granulosum
- Stratum basale (Correct answer)
- Dermis
Correct answer: Stratum basale
Melanocytes reside in the stratum basale (deepest epidermal layer) and transfer melanin granules to surrounding keratinocytes.
Question 7: During a sympathetic 'fight-or-flight' response, which effect on the heart would you expect?
- Decreased heart rate and decreased contractility
- Increased heart rate and increased contractility (Correct answer)
- Decreased heart rate and increased stroke volume only
- No change in heart rate but vasodilation of coronary vessels
Correct answer: Increased heart rate and increased contractility
Norepinephrine released by sympathetic neurons binds β1 receptors, increasing both heart rate (chronotropy) and contractility (inotropy).
CLEP Biology Organismal Biology & Physiology 2
Which structure in the human kidney is responsible for filtering blood to form the initial filtrate?