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HESI A2 Biology Twisted Quiz

Question 1 of 35

Which structure inside the nucleus helps produce ribosomal subunits?

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HESI A2 Biology Twisted Quiz Practice Questions

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

Question 1

Which structure inside the nucleus helps produce ribosomal subunits?

  1. Lysosome
  2. Centrosome
  3. Vacuole
  4. Nucleolus
View answer and explanation

Correct answer:

  1. Nucleolus

Explanation: The nucleolus produces ribosomal RNA and assembles ribosomal subunits.

Question 2

What is a major function of the cytoskeleton?

  1. Storing all genetic information
  2. Maintaining cell shape and supporting movement
  3. Producing glucose from sunlight
  4. Forming the phospholipid bilayer
View answer and explanation

Correct answer:

  1. Maintaining cell shape and supporting movement

Explanation: The cytoskeleton is a network of protein fibers that supports and organizes the cell.

Question 3

Which structures connect neighboring plant cells through their cell walls?

  1. Flagella
  2. Lysosomes
  3. Plasmodesmata
  4. Centrioles
View answer and explanation

Correct answer:

  1. Plasmodesmata

Explanation: Plasmodesmata are channels that allow communication and transport between plant cells.

Question 4

Which substance forms a major structural component of plant cell walls?

  1. Cellulose
  2. Glycogen
  3. Cholesterol
  4. Hemoglobin
View answer and explanation

Correct answer:

  1. Cellulose

Explanation: Cellulose fibers provide strength and support to plant cell walls.

Question 5

As a cell grows larger without changing shape, its surface-area-to-volume ratio generally:

  1. Increases continuously
  2. Remains the same
  3. Becomes zero immediately
  4. Decreases
View answer and explanation

Correct answer:

  1. Decreases

Explanation: Volume increases faster than surface area, making exchange less efficient relative to the cell’s needs.

Question 6

Oxygen moves directly through a cell membrane from a higher concentration to a lower concentration. This is:

  1. Active transport
  2. Simple diffusion
  3. Exocytosis
  4. Phagocytosis
View answer and explanation

Correct answer:

  1. Simple diffusion

Explanation: Small oxygen molecules can cross the lipid bilayer without transport proteins or ATP.

Question 7

How does facilitated diffusion differ from simple diffusion?

  1. It always moves substances against a gradient
  2. It always requires ATP
  3. It uses membrane transport proteins
  4. It occurs only in plant cells
View answer and explanation

Correct answer:

  1. It uses membrane transport proteins

Explanation: Facilitated diffusion uses channels or carriers while moving substances down their gradient.

Question 8

What is the function of aquaporins?

  1. To allow rapid movement of water across membranes
  2. To copy DNA
  3. To break down proteins
  4. To produce oxygen
View answer and explanation

Correct answer:

  1. To allow rapid movement of water across membranes

Explanation: Aquaporins are membrane channels specialized for water transport.

Question 9

What happens when a plant cell undergoes plasmolysis?

  1. Its chromosomes double
  2. Its cell wall dissolves
  3. Its chloroplasts become nuclei
  4. Its membrane pulls away from the wall as water is lost
View answer and explanation

Correct answer:

  1. Its membrane pulls away from the wall as water is lost

Explanation: A hypertonic environment draws water out, causing the cell contents to shrink.

Question 10

The sodium-potassium pump is an example of:

  1. Osmosis
  2. Active transport
  3. Simple diffusion
  4. Fermentation
View answer and explanation

Correct answer:

  1. Active transport

Explanation: The pump uses ATP to move sodium and potassium ions against their gradients.

Question 11

What are the basic building blocks of proteins?

  1. Fatty acids
  2. Nucleotides
  3. Amino acids
  4. Monosaccharides
View answer and explanation

Correct answer:

  1. Amino acids

Explanation: Proteins consist of amino acids joined by peptide bonds.

Question 12

In what form do humans store much of their carbohydrate reserve in the liver and muscles?

  1. Glycogen
  2. Cellulose
  3. DNA
  4. Collagen
View answer and explanation

Correct answer:

  1. Glycogen

Explanation: Glycogen is a branched glucose polymer used for carbohydrate storage in animals.

Question 13

Which class of biological molecules includes fats and oils?

  1. Proteins
  2. Nucleic acids
  3. Carbohydrates
  4. Lipids
View answer and explanation

Correct answer:

  1. Lipids

Explanation: Fats and oils are lipids used for energy storage and other functions.

Question 14

When an enzyme becomes denatured, what usually happens?

  1. It becomes a chromosome
  2. Its altered shape reduces or destroys its activity
  3. It gains an additional nucleus
  4. It can act on every possible substrate
View answer and explanation

Correct answer:

  1. Its altered shape reduces or destroys its activity

Explanation: Denaturation can change the active site so the enzyme no longer functions properly.

Question 15

Which pigment absorbs light energy for photosynthesis in green plants?

  1. Hemoglobin
  2. Melanin
  3. Chlorophyll
  4. Keratin
View answer and explanation

Correct answer:

  1. Chlorophyll

Explanation: Chlorophyll absorbs light that powers photosynthetic reactions.

Question 16

Where do the light-dependent reactions of photosynthesis occur?

  1. Thylakoid membranes
  2. Nuclear envelope
  3. Cell wall
  4. Cytosol
View answer and explanation

Correct answer:

  1. Thylakoid membranes

Explanation: These membranes contain chlorophyll, electron carriers, and ATP-producing machinery.

Question 17

Which gas supplies the carbon used to build sugars during photosynthesis?

  1. Oxygen
  2. Nitrogen
  3. Hydrogen
  4. Carbon dioxide
View answer and explanation

Correct answer:

  1. Carbon dioxide

Explanation: Plants incorporate carbon from carbon dioxide into organic molecules.

Question 18

Which statement about plant cells is correct?

  1. They carry out photosynthesis but never respiration
  2. They carry out cellular respiration during both day and night
  3. They respire only when they lose their chloroplasts
  4. They obtain all ATP directly from soil
View answer and explanation

Correct answer:

  1. They carry out cellular respiration during both day and night

Explanation: Plant cells need ATP continuously, whether or not light is available.

Question 19

Where is the electron transport chain of aerobic respiration located in human cells?

  1. Outer nuclear membrane
  2. Cell membrane
  3. Inner mitochondrial membrane
  4. Golgi membrane
View answer and explanation

Correct answer:

  1. Inner mitochondrial membrane

Explanation: Electron carriers in this membrane establish the proton gradient used to produce ATP.

Question 20

What directly powers ATP synthase during oxidative phosphorylation?

  1. Hydrogen ions flowing down their electrochemical gradient
  2. Chromosomes separating
  3. Carbon dioxide entering the nucleus
  4. Ribosomes joining amino acids
View answer and explanation

Correct answer:

  1. Hydrogen ions flowing down their electrochemical gradient

Explanation: The flow of hydrogen ions through ATP synthase drives ATP formation.

Question 21

Which nitrogenous base is found in RNA instead of thymine?

  1. Guanine
  2. Cytosine
  3. Adenine
  4. Uracil
View answer and explanation

Correct answer:

  1. Uracil

Explanation: RNA uses uracil, whereas DNA normally uses thymine.

Question 22

What is transcription?

  1. Making a protein from an RNA message
  2. Making RNA using a DNA template
  3. Dividing the cytoplasm
  4. Joining two gametes
View answer and explanation

Correct answer:

  1. Making RNA using a DNA template

Explanation: Transcription copies information from a DNA sequence into RNA.

Question 23

What is translation?

  1. Copying DNA before cell division
  2. Moving water across a membrane
  3. Making a protein using information in messenger RNA
  4. Separating homologous chromosomes
View answer and explanation

Correct answer:

  1. Making a protein using information in messenger RNA

Explanation: Ribosomes read mRNA and assemble the corresponding amino acid sequence.

Question 24

What is a mutation?

  1. A change in the DNA sequence
  2. Any movement of a cell
  3. The release of ATP
  4. A normal pairing of complementary bases
View answer and explanation

Correct answer:

  1. A change in the DNA sequence

Explanation: Mutations alter genetic information and may have harmful, beneficial, or neutral effects.

Question 25

Red-flowered and white-flowered plants produce pink-flowered offspring. What inheritance pattern does this illustrate?

  1. Complete dominance
  2. Sex linkage
  3. Codominance
  4. Incomplete dominance
View answer and explanation

Correct answer:

  1. Incomplete dominance

Explanation: The heterozygous offspring have a phenotype intermediate between the two parental phenotypes.

Question 26

A person with blood group AB expresses both A and B antigens. This is an example of:

  1. Incomplete dominance
  2. Codominance
  3. Recessive inheritance
  4. Asexual reproduction
View answer and explanation

Correct answer:

  1. Codominance

Explanation: Both alleles are expressed in the heterozygous individual.

Question 27

During meiosis, crossing over occurs between:

  1. Two unrelated body cells
  2. A chromosome and a ribosome
  3. Nonsister chromatids of homologous chromosomes
  4. A sperm cell and an egg cell
View answer and explanation

Correct answer:

  1. Nonsister chromatids of homologous chromosomes

Explanation: They exchange corresponding DNA segments, increasing genetic variation.

Question 28

How many daughter cells are normally produced by one complete meiotic division of a diploid cell?

  1. Four haploid cells
  2. Two diploid cells
  3. Four diploid cells
  4. Two haploid cells
View answer and explanation

Correct answer:

  1. Four haploid cells

Explanation: Two successive divisions usually produce four cells with half the original chromosome number.

Question 29

What is nondisjunction?

  1. The normal copying of DNA
  2. The joining of amino acids
  3. The formation of a cell wall
  4. Failure of chromosomes or chromatids to separate properly
View answer and explanation

Correct answer:

  1. Failure of chromosomes or chromatids to separate properly

Explanation: Nondisjunction can produce cells with extra or missing chromosomes.

Question 30

Why is a stain often added to a specimen before light-microscope observation?

  1. To increase the objective lens’s magnification
  2. To increase contrast between structures
  3. To turn every cell into a living cell
  4. To replace the light source
View answer and explanation

Correct answer:

  1. To increase contrast between structures

Explanation: Stains make otherwise transparent structures easier to distinguish.

Question 31

Which part of a microscope holds the objective lenses and rotates to change magnification?

  1. Stage
  2. Eyepiece
  3. Revolving nosepiece
  4. Base
View answer and explanation

Correct answer:

  1. Revolving nosepiece

Explanation: Rotating the nosepiece brings a different objective into position.

Question 32

What is the protective protein coat surrounding a virus’s genetic material called?

  1. Capsid
  2. Cell wall
  3. Nucleolus
  4. Cytoskeleton
View answer and explanation

Correct answer:

  1. Capsid

Explanation: The capsid encloses and protects the viral genome.

Question 33

What is the usual method of reproduction in bacteria?

  1. Meiosis
  2. Fertilization
  3. Mitosis
  4. Binary fission
View answer and explanation

Correct answer:

  1. Binary fission

Explanation: A bacterium copies its DNA and divides into two daughter cells.

Question 34

Which tissue covers body surfaces and lines many internal cavities?

  1. Muscle tissue
  2. Epithelial tissue
  3. Nervous tissue
  4. Bone tissue
View answer and explanation

Correct answer:

  1. Epithelial tissue

Explanation: Epithelial tissue forms coverings and linings and may perform absorption or secretion.

Question 35

What is homeostasis?

  1. Continuous growth without regulation
  2. Production of identical offspring
  3. Maintenance of relatively stable internal conditions
  4. Classification of organisms into species
View answer and explanation

Correct answer:

  1. Maintenance of relatively stable internal conditions

Explanation: Homeostasis regulates conditions such as temperature, blood glucose, and water balance.