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HESI A2 Biology Twisted Set 2

Question 1 of 35

Which structure regulates movement between the nucleus and cytoplasm?

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HESI A2 Biology Twisted Set 2 Practice Questions

Review these HESI A2 Biology Twisted Set 2 nursing practice questions with answer choices and explanations.

Question 1

Which structure regulates movement between the nucleus and cytoplasm?

  1. Nuclear pores
  2. Ribosomes
  3. Lysosomes
  4. Centrioles
View answer and explanation

Correct answer:

  1. Nuclear pores

Explanation: Nuclear pores control the passage of substances such as RNA and proteins through the nuclear envelope.

Question 2

Which organelle helps break down fatty acids and contains enzymes that convert hydrogen peroxide into water and oxygen?

  1. Golgi apparatus
  2. Nucleolus
  3. Peroxisome
  4. Ribosome
View answer and explanation

Correct answer:

  1. Peroxisome

Explanation: Peroxisomes participate in fatty acid breakdown and use catalase to break down hydrogen peroxide.

Question 3

What is the main function of cholesterol in an animal cell membrane?

  1. Carrying genetic information
  2. Helping regulate membrane fluidity
  3. Producing proteins
  4. Digesting cellular waste
View answer and explanation

Correct answer:

  1. Helping regulate membrane fluidity

Explanation: Cholesterol helps stabilize membranes and moderates changes in fluidity.

Question 4

A chemical messenger binds to a receptor on a cell. What is the receptor’s main role?

  1. To copy the cell’s DNA
  2. To digest the messenger
  3. To form a new chromosome
  4. To recognize the signal and initiate a response
View answer and explanation

Correct answer:

  1. To recognize the signal and initiate a response

Explanation: Receptors allow cells to detect particular signals and respond to them.

Question 5

Which junction allows small molecules and ions to pass directly between neighboring animal cells?

  1. Gap junction
  2. Tight junction
  3. Cell wall
  4. Nuclear pore
View answer and explanation

Correct answer:

  1. Gap junction

Explanation: Gap junctions form communication channels between adjacent animal cells.

Question 6

What is the main function of tight junctions between epithelial cells?

  1. Producing ATP
  2. Moving chromosomes
  3. Limiting leakage between neighboring cells
  4. Making antibodies
View answer and explanation

Correct answer:

  1. Limiting leakage between neighboring cells

Explanation: Tight junctions seal spaces between cells, helping control passage across an epithelial layer.

Question 7

What is apoptosis?

  1. Uncontrolled cell swelling
  2. Programmed cell death
  3. DNA replication
  4. Cell fusion
View answer and explanation

Correct answer:

  1. Programmed cell death

Explanation: Apoptosis removes unwanted or damaged cells through a controlled process.

Question 8

What is the main purpose of cell-cycle checkpoints?

  1. To ensure every cell divides immediately
  2. To prevent protein synthesis
  3. To remove all chromosomes
  4. To check whether a cell is ready to proceed with division
View answer and explanation

Correct answer:

  1. To check whether a cell is ready to proceed with division

Explanation: Checkpoints can halt progression when DNA is damaged or other requirements are unmet. OpenStax

Question 9

What makes a stem cell different from many specialized cells?

  1. It can self-renew and develop into specialized cell types
  2. It contains no DNA
  3. It cannot divide
  4. It is always a bacterial cell
View answer and explanation

Correct answer:

  1. It can self-renew and develop into specialized cell types

Explanation: Stem cells can produce more stem cells and differentiate into other cell types.

Question 10

Why can nerve cells and muscle cells have different functions despite containing largely the same DNA?

  1. They use different genetic codes
  2. Muscle cells have no genes
  3. They express different combinations of genes
  4. Nerve cells contain only RNA
View answer and explanation

Correct answer:

  1. They express different combinations of genes

Explanation: Different patterns of gene expression produce different proteins and cell functions.

Question 11

DNA wrapped around proteins called histones forms part of which material?

  1. Cytoplasm
  2. Chromatin
  3. Cellulose
  4. Plasma
View answer and explanation

Correct answer:

  1. Chromatin

Explanation: Chromatin consists of DNA and associated proteins that help package it.

Question 12

Which statement correctly describes homologous chromosomes?

  1. They are always identical copies produced by DNA replication
  2. They occur only in bacteria
  3. They contain no genes
  4. They carry corresponding genes at matching positions
View answer and explanation

Correct answer:

  1. They carry corresponding genes at matching positions

Explanation: Homologous chromosomes carry the same kinds of genes but may contain different alleles.

Question 13

What are autosomes?

  1. Chromosomes other than sex chromosomes
  2. Chromosomes found only in sperm
  3. Structures that produce ATP
  4. Genes found only in mitochondria
View answer and explanation

Correct answer:

  1. Chromosomes other than sex chromosomes

Explanation: Humans normally have 22 pairs of autosomes and one pair of sex chromosomes.

Question 14

Which enzyme adds nucleotides to a growing DNA strand during replication?

  1. Amylase
  2. Lipase
  3. DNA polymerase
  4. Pepsin
View answer and explanation

Correct answer:

  1. DNA polymerase

Explanation: DNA polymerase builds a new strand using an existing DNA strand as a template.

Question 15

What does “semiconservative DNA replication” mean?

  1. Only half the DNA molecule is copied
  2. Each resulting DNA molecule contains one original strand and one new strand
  3. Both original strands are destroyed
  4. DNA is copied into protein
View answer and explanation

Correct answer:

  1. Each resulting DNA molecule contains one original strand and one new strand

Explanation: The original strands separate and each guides the formation of a complementary strand. OpenStax

Question 16

How many nucleotide bases make up one codon in messenger RNA?

  1. One
  2. Two
  3. Four
  4. Three
View answer and explanation

Correct answer:

  1. Three

Explanation: Each three-base codon specifies an amino acid or a stop signal.

Question 17

What is the main role of transfer RNA during protein synthesis?

  1. Carrying amino acids to the ribosome
  2. Copying chromosomes
  3. Breaking down glucose
  4. Producing lipids
View answer and explanation

Correct answer:

  1. Carrying amino acids to the ribosome

Explanation: Transfer RNA matches its anticodon to an mRNA codon and delivers the appropriate amino acid.

Question 18

A DNA sample contains 20% adenine. Approximately what percentage is guanine if the DNA is double-stranded?

  1. 20%
  2. 40%
  3. 30%
  4. 60%
View answer and explanation

Correct answer:

  1. 30%

Explanation: Thymine is also 20%, leaving 60% shared equally between guanine and cytosine.

Question 19

A plant with genotype Aa is crossed with a plant with genotype aa. What fraction of offspring is expected to have genotype aa?

  1. One-quarter
  2. One-half
  3. Three-quarters
  4. All offspring
View answer and explanation

Correct answer:

  1. One-half

Explanation: The possible offspring are Aa and aa in equal proportions.

Question 20

What is the purpose of a test cross in basic genetics?

  1. To produce only dominant offspring
  2. To change an organism’s species
  3. To double its chromosomes
  4. To help determine the genotype of an organism showing a dominant trait
View answer and explanation

Correct answer:

  1. To help determine the genotype of an organism showing a dominant trait

Explanation: Crossing it with a homozygous recessive organism can reveal whether it carries a recessive allele.

Question 21

Which microscope part concentrates light onto the specimen?

  1. Condenser
  2. Arm
  3. Stage clip
  4. Nosepiece
View answer and explanation

Correct answer:

  1. Condenser

Explanation: The condenser focuses illumination onto the specimen.

Question 22

When first locating a specimen under a microscope, which objective should usually be selected?

  1. The highest-power objective
  2. The oil-immersion objective
  3. The lowest-power objective
  4. Any objective without adjustment
View answer and explanation

Correct answer:

  1. The lowest-power objective

Explanation: Low power provides a wider field of view and makes the specimen easier to locate.

Question 23

What generally happens to the field of view as microscope magnification increases?

  1. It becomes larger
  2. It becomes smaller
  3. It remains exactly the same
  4. It disappears completely
View answer and explanation

Correct answer:

  1. It becomes smaller

Explanation: Higher magnification displays a smaller area of the specimen.

Question 24

Why is immersion oil used with an appropriate oil-immersion objective?

  1. To stain the nucleus
  2. To keep cells alive
  3. To dissolve the slide
  4. To reduce light refraction and improve resolution
View answer and explanation

Correct answer:

  1. To reduce light refraction and improve resolution

Explanation: Oil helps more light enter the objective, allowing finer details to be resolved.

Question 25

Which plant tissue transports water and dissolved minerals from the roots?

  1. Xylem
  2. Phloem
  3. Epidermis
  4. Meristem
View answer and explanation

Correct answer:

  1. Xylem

Explanation: Xylem conducts water and minerals through the plant. OpenStax

Question 26

Which plant tissue transports sugars from sources to areas where they are used or stored?

  1. Xylem
  2. Root cap
  3. Phloem
  4. Cork
View answer and explanation

Correct answer:

  1. Phloem

Explanation: Phloem distributes sugars and other organic substances around the plant. OpenStax

Question 27

What is transpiration?

  1. Formation of seeds
  2. Loss of water vapor from a plant
  3. Breakdown of glucose
  4. Movement of pollen between flowers
View answer and explanation

Correct answer:

  1. Loss of water vapor from a plant

Explanation: Most transpiration occurs through stomata in leaves.

Question 28

Which cells control the opening and closing of stomata?

  1. Red blood cells
  2. Root-hair cells
  3. Sieve-tube cells
  4. Guard cells
View answer and explanation

Correct answer:

  1. Guard cells

Explanation: Changes in guard-cell turgor regulate the stomatal opening.

Question 29

How do root hairs improve water and mineral absorption?

  1. They increase the root’s surface area
  2. They produce flowers
  3. They prevent all osmosis
  4. They replace the xylem
View answer and explanation

Correct answer:

  1. They increase the root’s surface area

Explanation: Their extensions provide more contact with the soil.

Question 30

Which plant tissue contains actively dividing cells responsible for growth?

  1. Mature xylem vessels
  2. Cork tissue
  3. Meristematic tissue
  4. Mature leaf epidermis only
View answer and explanation

Correct answer:

  1. Meristematic tissue

Explanation: Meristems produce new cells that contribute to plant growth. OpenStax

Question 31

Which protein in red blood cells binds and carries oxygen?

  1. Insulin
  2. Hemoglobin
  3. Collagen
  4. Keratin
View answer and explanation

Correct answer:

  1. Hemoglobin

Explanation: Hemoglobin binds oxygen in the lungs and releases it to body tissues.

Question 32

Which blood components are cell fragments that help form clots?

  1. Red blood cells
  2. Antibodies
  3. Plasma proteins only
  4. Platelets
View answer and explanation

Correct answer:

  1. Platelets

Explanation: Platelets gather at damaged blood vessels and help initiate clot formation.

Question 33

Which blood vessels carry blood away from the heart?

  1. Arteries
  2. Veins
  3. Capillaries
  4. Lymphatic vessels
View answer and explanation

Correct answer:

  1. Arteries

Explanation: Arteries carry blood away from the heart, regardless of its oxygen content.

Question 34

Where does most exchange of gases and nutrients between blood and tissues occur?

  1. Large arteries
  2. Large veins
  3. Capillaries
  4. Heart valves
View answer and explanation

Correct answer:

  1. Capillaries

Explanation: Their thin walls allow substances to move between blood and surrounding tissues.

Question 35

Which air sacs are the main sites of gas exchange in human lungs?

  1. Bronchi
  2. Alveoli
  3. Tracheal rings
  4. Vocal cords
View answer and explanation

Correct answer:

  1. Alveoli

Explanation: Oxygen and carbon dioxide diffuse across the thin walls of alveoli and nearby capillaries.