4.3 Bio Content

Question 1

Extracellular matrix (ECM)

Answer 1

A network outside animal cells providing structural and biochemical support. Composed of collagen fibers for tensile strength and proteoglycans for compression resistance.

Question 2

Primary cell wall

Answer 2

A flexible wall formed in young plant cells made of cellulose microfibrils and pectin. Defines cell shape and resists turgor pressure.

Question 3

Secondary cell wall

Answer 3

A rigid layer deposited inside the primary cell wall in mature plant cells. Contains lignin for strength or wax for protection, depending on cell function.

Question 4

Tight junction

Answer 4

A waterproof seal formed by proteins between adjacent animal cells, preventing leakage of extracellular fluid. Found in epithelial tissue such as intestines.

Question 5

Desmosome

Answer 5

A strong anchoring junction connecting animal cells via cadherins. Links intermediate filaments, providing tissue stability, especially in muscles and skin.

Question 6

Gap junction

Answer 6

A channel between adjacent animal cells made of connexon proteins, allowing direct passage of ions and small molecules for coordination and communication.

Question 7

Plasmodesmata

Answer 7

Cytoplasmic channels through plant cell walls that connect cytoplasm of neighboring cells. Allow movement of water, solutes, proteins, and RNA.

Question 8

Integrins

Answer 8

Transmembrane proteins linking the ECM to the cytoskeleton. Bind to ECM proteins like laminin and transmit signals for cell adhesion and movement.

Question 9

Middle lamella

Answer 9

A pectin-rich layer between adjacent plant cell walls. Glues cells together and maintains plant tissue integrity.

Question 10

Expansins

Answer 10

Plant proteins that loosen cross-links between cellulose microfibrils in the primary cell wall, enabling cell expansion and growth.

Question 11

Collagen

Answer 11

Main fibrous component of animal ECM. Consists of triple-helix fibrils that provide tensile strength and structure to connective tissues.

Question 12

Proteoglycans

Answer 12

Gel-like ground substance of the ECM composed of proteins with attached polysaccharides. Provide cushioning and resist compression.

Question 13

Integrin–Laminin connection

Answer 13

Integrins bind to laminins in the ECM to anchor the cell’s cytoskeleton to external structures, ensuring mechanical stability and signal transmission.

Question 14

Cadherins

Answer 14

Cell adhesion proteins in desmosomes. Bind only to the same type (e.g., E-cadherin in epithelial cells, N-cadherin in nerve cells), allowing tissue-specific adhesion.

Question 15

Middle lamella composition

Answer 15

Composed mainly of pectin, the gelatinous material that helps stick adjacent plant cells together.

Question 16

Symplast

Answer 16

Continuous network of cytoplasm interconnected by plasmodesmata, allowing direct exchange of materials between plant cells.

Question 17

Apoplast

Answer 17

The extracellular space in plant tissues, including cell walls and intercellular spaces. Allows water and solute movement outside membranes.

Question 18

Integrins function

Answer 18

Connect the cytoskeleton inside the cell to ECM proteins outside, playing a role in cell movement, structure, and signaling.

Question 19

Tissues

Answer 19

Groups of similar cells that work together to perform a specific function, such as epithelial, connective, muscle, and nervous tissues.

Question 20

ECM variation

Answer 20

Different tissues have different ECM compositions. Example: elastin in lungs allows stretch, while bone ECM is mineralized for rigidity.