HESI A2 Biology practice Exam with Multiple Choice
Questions and Rationalized Answers 2025 Updated
1. Which of the following is NOT a part of the body's chemical defense system against
infection?
a. Urine
b. Hydrochloric acid
c. Agranulocyte
d. Lysozyme: - Agranulocytes
Agranulocytes are a type of white blood cell and therefore are not a part of the body's chemical
defense system.
2. Which of the following is considered an example of naturally acquired passive
immunity?
a. Attenuated (live) vaccine injection
b. Breastfeeding
c. Inactivated (killed) vaccine injection
d. Exposure to a disease and subsequent immunity: - breastfeeding Natural passive
immunity occurs when live antibodies are transferred from one
individual to another, such as when anti-bodies are transferred from a mother to her baby via
breast milk.
3. Worms lack which of the following?
a. Eyes and brain
b. Brain
,c. Eyes
d. Nerve centers: - eyes and brain
Worms lack both eyes and a brain, but they do have nerve centers.
4. Which organelle is responsible for generating ATP that is used for chemical energy?
a. Mitochondria
b. Vesicle
c. Ribosome
d. Golgi apparatus: - mitochondria
The mitochondrion is often referred to as the "power plant" of the cell, because it generates
ATP, the cell's source of chemical energy.
5. Which of the following is true with regard to eukaryotic and prokaryotic cells?
a. Prokaryotic cells can contain lysosomes.
b. Eukaryotic cells have mitochondria.
,c. Prokaryotic cells can contain lysosomes and eukaryotic cells have mito- chondria.
d. Prokaryotic cells have a nucleus.: - Eukaryotic cells have mitochondria.
One of the major differences between eukaryotic cells and prokaryotic cells is that
eukaryotic cells contain organelles, such as mitochondria, whereas prokaryotic cells do not.
6. Positive feedback is a mechanism used by the body that results in amplifi- cation or
enhancement of a signal that has already been activated. An example of this would be:
a. Slowing metabolism in response to starvation
b. Shivering to increase temperature
c. Blood vessels regulating blood pressure
d. The release of oxytocin to increase contractions during childbirth: - The release of
oxytocin to increase contractions during childbirth
Contractions in childbirth are considered a positive feedback loop because each contraction
stimulates the brain to release more Oxytocin, which in turn stimulates more contractions.
7. When placed in a hypotonic solution, a cell will do which of the following?
a. Remain the same
b. Disintegrate
c. Swell
d. Shrink: - swell
Water always moves from areas of higher concentration to lower concentration. A hypotonic
solution contains less solutes and more water then the contents inside of the cell, so water wi
move from outside of the cell to inside, causing it to swell.
8. Which is NOT an effect of photo-oxidation?
, a. Increase in tensile strength
b. Discoloration
c. Increase in brittleness
d. Loss of surface smoothness: - Increase in tensile strength
Photo-oxidation occurs when UV light and ozone break down the surface of poly- mers.The
result is the material becoming more brittle and discolored and less strong and smooth.
9. The movement of a substance across a cell membrane from low to high
concentration is known as what?
Questions and Rationalized Answers 2025 Updated
1. Which of the following is NOT a part of the body's chemical defense system against
infection?
a. Urine
b. Hydrochloric acid
c. Agranulocyte
d. Lysozyme: - Agranulocytes
Agranulocytes are a type of white blood cell and therefore are not a part of the body's chemical
defense system.
2. Which of the following is considered an example of naturally acquired passive
immunity?
a. Attenuated (live) vaccine injection
b. Breastfeeding
c. Inactivated (killed) vaccine injection
d. Exposure to a disease and subsequent immunity: - breastfeeding Natural passive
immunity occurs when live antibodies are transferred from one
individual to another, such as when anti-bodies are transferred from a mother to her baby via
breast milk.
3. Worms lack which of the following?
a. Eyes and brain
b. Brain
,c. Eyes
d. Nerve centers: - eyes and brain
Worms lack both eyes and a brain, but they do have nerve centers.
4. Which organelle is responsible for generating ATP that is used for chemical energy?
a. Mitochondria
b. Vesicle
c. Ribosome
d. Golgi apparatus: - mitochondria
The mitochondrion is often referred to as the "power plant" of the cell, because it generates
ATP, the cell's source of chemical energy.
5. Which of the following is true with regard to eukaryotic and prokaryotic cells?
a. Prokaryotic cells can contain lysosomes.
b. Eukaryotic cells have mitochondria.
,c. Prokaryotic cells can contain lysosomes and eukaryotic cells have mito- chondria.
d. Prokaryotic cells have a nucleus.: - Eukaryotic cells have mitochondria.
One of the major differences between eukaryotic cells and prokaryotic cells is that
eukaryotic cells contain organelles, such as mitochondria, whereas prokaryotic cells do not.
6. Positive feedback is a mechanism used by the body that results in amplifi- cation or
enhancement of a signal that has already been activated. An example of this would be:
a. Slowing metabolism in response to starvation
b. Shivering to increase temperature
c. Blood vessels regulating blood pressure
d. The release of oxytocin to increase contractions during childbirth: - The release of
oxytocin to increase contractions during childbirth
Contractions in childbirth are considered a positive feedback loop because each contraction
stimulates the brain to release more Oxytocin, which in turn stimulates more contractions.
7. When placed in a hypotonic solution, a cell will do which of the following?
a. Remain the same
b. Disintegrate
c. Swell
d. Shrink: - swell
Water always moves from areas of higher concentration to lower concentration. A hypotonic
solution contains less solutes and more water then the contents inside of the cell, so water wi
move from outside of the cell to inside, causing it to swell.
8. Which is NOT an effect of photo-oxidation?
, a. Increase in tensile strength
b. Discoloration
c. Increase in brittleness
d. Loss of surface smoothness: - Increase in tensile strength
Photo-oxidation occurs when UV light and ozone break down the surface of poly- mers.The
result is the material becoming more brittle and discolored and less strong and smooth.
9. The movement of a substance across a cell membrane from low to high
concentration is known as what?
