CHAMBERLAIN UNIVERSITY – BIOS 251 EXAM TEST
QUESTIONS AND CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2026 |INSTANT
DOWNLOAD PDF
1. Which organelle is primarily responsible for ATP
production?
A. Ribosome
B. Nucleus
C. Mitochondrion
D. Lysosome
Correct Answer: C
The mitochondrion is the site of oxidative phosphorylation,
where most cellular ATP is produced.
2. The plasma membrane is best described as:
A. A rigid barrier
B. A fluid mosaic
C. A solid wall
D. A carbohydrate layer
Correct Answer: B
The fluid mosaic model describes phospholipids and proteins
moving laterally within the membrane.
,3. Which ion is most abundant in extracellular fluid?
A. Potassium
B. Calcium
C. Sodium
D. Magnesium
Correct Answer: C
Sodium is the dominant extracellular cation and plays a key role
in nerve impulse transmission.
4. Diffusion requires which of the following?
A. ATP
B. Carrier proteins
C. Concentration gradient
D. Vesicles
Correct Answer: C
Diffusion occurs passively down a concentration gradient
without energy input.
5. Which process moves substances against their
concentration gradient?
A. Osmosis
B. Facilitated diffusion
,C. Active transport
D. Filtration
Correct Answer: C
Active transport requires ATP to move substances against their
gradient.
6. The resting membrane potential of a neuron is
approximately:
A. +30 mV
B. –70 mV
C. 0 mV
D. –90 mV
Correct Answer: B
The resting membrane potential reflects ion distribution across
the neuronal membrane.
7. Depolarization of a neuron is primarily caused by:
A. Potassium efflux
B. Sodium influx
C. Calcium efflux
D. Chloride influx
Correct Answer: B
Opening of sodium channels allows Na⁺ to enter the neuron,
making the membrane less negative.
, 8. Which neurotransmitter is most commonly excitatory in the
CNS?
A. GABA
B. Dopamine
C. Acetylcholine
D. Glutamate
Correct Answer: D
Glutamate is the primary excitatory neurotransmitter in the
central nervous system.
9. The sarcomere is the functional unit of:
A. Smooth muscle
B. Cardiac muscle
C. Skeletal muscle
D. Nervous tissue
Correct Answer: C
Skeletal muscle contraction occurs through sarcomere
shortening.
10. Muscle contraction begins when calcium binds to:
A. Actin
B. Myosin
QUESTIONS AND CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2026 |INSTANT
DOWNLOAD PDF
1. Which organelle is primarily responsible for ATP
production?
A. Ribosome
B. Nucleus
C. Mitochondrion
D. Lysosome
Correct Answer: C
The mitochondrion is the site of oxidative phosphorylation,
where most cellular ATP is produced.
2. The plasma membrane is best described as:
A. A rigid barrier
B. A fluid mosaic
C. A solid wall
D. A carbohydrate layer
Correct Answer: B
The fluid mosaic model describes phospholipids and proteins
moving laterally within the membrane.
,3. Which ion is most abundant in extracellular fluid?
A. Potassium
B. Calcium
C. Sodium
D. Magnesium
Correct Answer: C
Sodium is the dominant extracellular cation and plays a key role
in nerve impulse transmission.
4. Diffusion requires which of the following?
A. ATP
B. Carrier proteins
C. Concentration gradient
D. Vesicles
Correct Answer: C
Diffusion occurs passively down a concentration gradient
without energy input.
5. Which process moves substances against their
concentration gradient?
A. Osmosis
B. Facilitated diffusion
,C. Active transport
D. Filtration
Correct Answer: C
Active transport requires ATP to move substances against their
gradient.
6. The resting membrane potential of a neuron is
approximately:
A. +30 mV
B. –70 mV
C. 0 mV
D. –90 mV
Correct Answer: B
The resting membrane potential reflects ion distribution across
the neuronal membrane.
7. Depolarization of a neuron is primarily caused by:
A. Potassium efflux
B. Sodium influx
C. Calcium efflux
D. Chloride influx
Correct Answer: B
Opening of sodium channels allows Na⁺ to enter the neuron,
making the membrane less negative.
, 8. Which neurotransmitter is most commonly excitatory in the
CNS?
A. GABA
B. Dopamine
C. Acetylcholine
D. Glutamate
Correct Answer: D
Glutamate is the primary excitatory neurotransmitter in the
central nervous system.
9. The sarcomere is the functional unit of:
A. Smooth muscle
B. Cardiac muscle
C. Skeletal muscle
D. Nervous tissue
Correct Answer: C
Skeletal muscle contraction occurs through sarcomere
shortening.
10. Muscle contraction begins when calcium binds to:
A. Actin
B. Myosin
