EmSAT Biology 5 — Questions and Answers
Question 1: A red blood cell is placed in a solution and it swells and bursts. What type of solution was it placed in?
- Hypertonic
- Isotonic
- Hypotonic (Correct answer)
- Saturated
Correct answer: Hypotonic
In a hypotonic solution (lower solute concentration than the cell), water enters the cell by osmosis causing it to swell and lyse.
Question 2: Which of the following correctly describes the lock-and-key model of enzyme action?
- The enzyme changes shape to fit any substrate
- Only a specific substrate fits the active site of an enzyme (Correct answer)
- Enzymes are permanently altered after each reaction
- Multiple enzymes share a single active site
Correct answer: Only a specific substrate fits the active site of an enzyme
The lock-and-key model proposes that only a substrate with a complementary shape can bind to the enzyme's specific active site.
Question 3: What is the role of the sinoatrial (SA) node in the human heart?
- It pumps oxygenated blood to the body
- It acts as the heart's natural pacemaker initiating electrical impulses (Correct answer)
- It prevents backflow of blood between chambers
- It filters waste products from the blood
Correct answer: It acts as the heart's natural pacemaker initiating electrical impulses
The SA node generates electrical impulses that spread across the atria, initiating each heartbeat and setting the heart rate.
Question 4: Which base pairs with adenine in a DNA molecule?
- Guanine
- Cytosine
- Uracil
- Thymine (Correct answer)
Correct answer: Thymine
In DNA, adenine (A) pairs with thymine (T) via two hydrogen bonds, following Chargaff's base-pairing rules.
Question 5: Which process converts light energy into chemical energy stored in glucose?
- Cellular respiration
- Fermentation
- Photosynthesis (Correct answer)
- Chemosynthesis
Correct answer: Photosynthesis
Photosynthesis occurs in chloroplasts and uses light energy to convert CO₂ and H₂O into glucose and O₂.
Question 6: A child has blood type O. Which of the following could be the genotypes of the parents?
- IAIA and IBIB
- IAi and IBi (Correct answer)
- IAIB and IAIB
- IAi and ii
Correct answer: IAi and IBi
Blood type O requires genotype ii; both parents must carry at least one i allele, so IAi × IBi can produce ii offspring.
Question 7: Which part of the nephron is primarily responsible for selective reabsorption of glucose and amino acids?
- Collecting duct
- Loop of Henle
- Proximal convoluted tubule (Correct answer)
- Distal convoluted tubule
Correct answer: Proximal convoluted tubule
The proximal convoluted tubule (PCT) reabsorbs nearly all filtered glucose, amino acids, and a large proportion of water and ions.
EmSAT Biology 5
A red blood cell is placed in a solution and it swells and bursts.
What type of solution was it placed in?