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MCAT Cell Junctions, Extracellular Matrix and Epithelial Tissue Practice Questions

By StudyStore · Published 2026-11-04 · 8 original questions · about 12 min

Eight free MCAT-style practice questions on tight junctions, desmosomes, gap junctions, hemidesmosomes, collagen, integrins and epithelial tissue types, with explanations.

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Quick concept primer

Animal cells connect in four main ways. Tight junctions form a seal between adjacent cells that blocks paracellular leakage and keeps apical and basolateral membrane proteins separate. Desmosomes are spot welds anchoring intermediate filaments (keratin) of neighboring cells and give strength to skin and heart muscle. Gap junctions are channels made of connexins that let ions and small molecules pass directly between cytoplasms, coordinating cardiac muscle. Hemidesmosomes anchor a cell to the basement membrane through integrins.

The extracellular matrix (ECM) includes collagen for tensile strength, elastin for stretch and glycoproteins such as fibronectin. Integrins link the ECM to the cytoskeleton. Epithelial tissue covers surfaces and lines cavities and is classified by layers (simple, stratified) and cell shape (squamous, cuboidal, columnar). Connective tissue (bone, blood, cartilage, adipose) has cells in abundant matrix.

8 practice questions

Try each question before opening the explanation. Click "Show answer and explanation" to check yourself. All questions are original and written for study practice.

Question 1

Which junction forms a seal that prevents molecules from leaking between epithelial cells?

  1. Desmosome
  2. Gap junction
  3. Tight junction
  4. Hemidesmosome
Show answer and explanation

Answer: C. Tight junction

Tight junctions encircle the apical end of epithelial cells and seal the space between them, so substances must pass through the cells. They also keep apical and basolateral membrane proteins from mixing. Desmosomes provide mechanical strength rather than a seal.

Question 2

Which junction allows ions and small molecules to pass directly from the cytoplasm of one cell to the next?

  1. Gap junction
  2. Tight junction
  3. Desmosome
  4. Hemidesmosome
Show answer and explanation

Answer: A. Gap junction

Gap junctions are channels formed by connexin proteins that connect neighboring cytoplasms. They allow electrical coupling, which is important for synchronized contraction in cardiac muscle and smooth muscle. Tight junctions and desmosomes do not create cytoplasmic channels.

Question 3

Skin and cardiac muscle must resist mechanical stress. Which junction best supports this by linking intermediate filaments of adjacent cells?

  1. Gap junction
  2. Desmosome
  3. Tight junction
  4. Plasmodesma
Show answer and explanation

Answer: B. Desmosome

Desmosomes act like spot welds and anchor keratin intermediate filaments (desmin in cardiac muscle) between cells, spreading tensile stress through the tissue. Plasmodesmata are channels between plant cells, and gap junctions are channels, not anchors.

Question 4

Hemidesmosomes differ from desmosomes in that hemidesmosomes

  1. connect a cell to the basement membrane through integrins
  2. connect two adjacent cells
  3. form channels for small ions
  4. are made of tubulin
Show answer and explanation

Answer: A. connect a cell to the basement membrane through integrins

Hemidesmosomes attach the basal surface of epithelial cells to the extracellular matrix of the basement membrane using integrins, which connect to intermediate filaments inside the cell. Desmosomes connect two cells to each other through cadherins.

Question 5

Which ECM protein is the most abundant in animals and provides tensile strength?

  1. Elastin
  2. Fibronectin
  3. Keratin
  4. Collagen
Show answer and explanation

Answer: D. Collagen

Collagen forms strong fibers resisting stretching forces in skin, tendon and bone. Elastin lets tissues such as arteries and lung recoil. Fibronectin helps cells attach to the matrix through integrins, and keratin is an intracellular intermediate filament protein.

Question 6

The lining of the air sacs of the lungs needs to permit rapid gas exchange. Which epithelium best fits this function?

  1. Stratified squamous epithelium
  2. Simple columnar epithelium
  3. Simple squamous epithelium
  4. Stratified cuboidal epithelium
Show answer and explanation

Answer: C. Simple squamous epithelium

A single layer of thin, flat cells minimizes the diffusion distance for oxygen and carbon dioxide. Stratified squamous epithelium is used where protection from abrasion is needed, such as skin. Simple columnar cells are common in absorption, such as the intestine.

Question 7

Which of the following is classified as connective tissue?

  1. Epithelium of the small intestine
  2. Cardiac muscle
  3. Bone
  4. The lining of blood vessels
Show answer and explanation

Answer: C. Bone

Connective tissue is characterized by cells scattered in a large extracellular matrix. Bone, cartilage, blood, adipose tissue and tendon are examples. The intestinal lining and the lining of blood vessels are epithelial, and cardiac muscle is muscle tissue.

Question 8

A mutation prevents cells from making functional integrins. What is the most likely effect?

  1. Impaired attachment of cells to the extracellular matrix
  2. Loss of the sodium-potassium pump
  3. Failure to form gap junctions between neighboring cells
  4. Inability to synthesize collagen
Show answer and explanation

Answer: A. Impaired attachment of cells to the extracellular matrix

Integrins are transmembrane receptors that bind ECM proteins such as fibronectin and collagen and link to the cytoskeleton, so loss of function weakens cell adhesion and signaling. Gap junctions use connexins, and collagen synthesis does not depend on integrins.

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Written by StudyStore from standard scientific facts as a study aid. These are not official exam questions and are not affiliated with or endorsed by any testing organization. Always check values against the reference provided with your exam or course.

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