5.Cell Cycle and Cytoskeleton

Question 1

Anchored junction

Answer 1

A cell–cell or cell–matrix junction that connects to the cytoskeleton to provide mechanical stability.

Question 2

Adherent junction

Answer 2

A junction that links actin filaments between adjacent cells through cadherins for strong adhesion.

Question 3

Hemidesmosome

Answer 3

A junction that anchors epithelial cells to the basement membrane via integrins and intermediate filaments.

Question 4

Transmembrane protein

Answer 4

A protein that spans the lipid bilayer and enables signaling, transport, or adhesion.

Question 5

Extracellular matrix

Answer 5

A network of proteins and polysaccharides that provides structural and biochemical support to cells.

Question 6

Collagen

Answer 6

The main structural protein of ECM that provides tensile strength.

Question 7

Scurvy

Answer 7

A disease caused by vitamin C deficiency leading to defective collagen synthesis.

Question 8

Elastin

Answer 8

An ECM protein that provides elasticity and allows tissues to stretch and recoil.

Question 9

Fibrillin

Answer 9

A glycoprotein that forms microfibrils and provides scaffolding for elastin.

Question 10

Glucosaminoglycan

Answer 10

A long, negatively charged polysaccharide in ECM that attracts water and resists compression.

Question 11

Proteoglycan

Answer 11

A core protein with attached GAGs that provides hydration and cushioning in the ECM.

Question 12

Integrin

Answer 12

A transmembrane receptor that links the ECM to the cytoskeleton and mediates cell adhesion and signaling.

tructure and Location: Integrins exist as dimers of α and β integrins. They are crucial components of cell adhesion structures.
• Function in Cell Adhesion: Integrins are the most important constituents of focal complexes/adhesions. They mediate the adhesion of cells to the extracellular matrix (ECM). Their primary role is establishing a dynamic connection between the cell and the extracellular matrix.
• Connection to Cytoskeleton: Internally, integrins bind to the actin filaments via adapter proteins, such as vinculin and talin. These connections (focal complexes/adhesions) allow the cell to adhere to a substrate. In order for a cell to move forward (migrate), this cell-ECM connection must be broken.
• Role in Viral Entry: Integrins can also function as cellular receptors. The integrin family of cell surface heterodimers is a target for the penton base protein of Adenoviruses, and binding to these integrins allows the virus to be internalized via receptor-mediated endocytosis

Question 13

Cell adhesion

Answer 13

The process by which cells attach to each other or to the ECM using adhesion molecules.

Question 14

Tight junction

Answer 14

A junction that seals neighboring cells to prevent leakage of molecules between them.

Question 15

Communicating junction

Answer 15

A junction that allows direct exchange of ions and small molecules between cells.

Question 16

Gap junction

Answer 16

A channel formed by connexins that permits electrical and metabolic communication between cells.

Question 17

Duchenne muscular dystrophy

Answer 17

Genetic Linkage: It is an X-linked muscular dystrophy.
• Cause: Muscular dystrophies, including DMD, are caused by mutations in the genes encoding connecting proteins that form the muscle tissue-specific ECM (extracellular matrix)-cell membrane-cytoskeleton connection.
• Proteins Affected: The linker molecules involved in this connection include dystrophin, sarcoglycans, dystroglycans, and laminin. Specifically regarding Duchenne’s muscular dystrophy, the sources mention that it results from mutations in the genes encoding linker molecules such as laminin, dystroglycans, [and] dystrophin.

Question 18

Motor protein

Answer 18

A protein that converts chemical energy (ATP) into mechanical movement along cytoskeletal filaments.

Question 19

Dynein

Answer 19

A motor protein that moves toward the minus end of microtubules and drives ciliary/flagellar motion.

Question 20

Kinesin

Answer 20

A motor protein that moves toward the plus end of microtubules and transports cargo within cells.

Question 21

What are the components of ECM?

Answer 21

fibrous protein
- collagen,
- Proteoglycan (glycoprotein)

Question 22

WHat are the functions of ECM

Answer 22

• Holds cells together in tissues
• Contributes to properties of bone, cartilage, skin, etc.
• Orient cell movements in development and tissue repair
• Plays a role in chemical signaling

Question 23

What is cytoskeleton?
Also write their Function.

Answer 23

The three filament systems that make up the cytoskeleton: intermediate filaments, microfilaments &
microtubules.
The main functions of the cytoskeleton:
1. determination of cell shape/stiffness
2. cell migration (amoeboid, ciliated and flagellar movement)
3. cell division/segregation of chromosomes
4. intracellular transport processes: transport of cell organelles, proteins, RNAs, DNA.

Question 24

List two microtubule motors and their direction of moving

Answer 24

Dynine : towards - end of MT
Kinesine: Towards + end of MT

Question 25

What are the functions of Kinesine and Dynine?

Answer 25

- Transporting vesicles, organelles, proteins, RNAs - Transporting pigment granules - Positioning **ER** and **Golgi** - **Depolymerizing kinetochore microtubules in anaphase** - Participating in **spindle apparatus formation**

Question 26

What are the classification of Kinesine?

Answer 26

**Classification (based on motor domain location)** - **Kin-N:** N-terminal motor domain → **plus-end directed** - **Kin-I:** Internal motor domain → **microtubule depolymerases** - **Kin-C:** C-terminal motor domain → **minus-end directed kinesins**

Question 27

What is the function of CYTOPLASMIC DYNEINS?

Answer 27

**Main Functions** - Transport cargo **toward the cell center** (minus-end directed) - Organelles, vesicles, macromolecules - Participate in: - **Transport of chromatids/chromosomes** - **Spindle apparatus formation** during mitosis/meiosis