ex16h

Question 1

What is phosphorylation/dephosphorylation?

Answer 1

A mechanism where kinases add phosphate groups to proteins to activate/inhibit them, and phosphatases remove phosphate groups to reverse the effect.

Question 2

How can transcription regulators be controlled in response to cellular stimuli?

Answer 2

Through phosphorylation, nuclear-cytoplasmic transport, ligand binding, ubiquitination, and protein-protein interactions.

Question 3

What is epigenetic modification and its role in cell identity?

Answer 3

Changes like DNA methylation and histone modifications maintain gene expression patterns and are heritable across cell divisions.

Question 4

How do transcriptional feedback loops maintain cell identity?

Answer 4

Self-reinforcing circuits ensure continued expression of lineage-specific genes, stabilizing cell identity.

Question 5

What features make microRNA effective gene regulators?

Answer 5

Specificity, versatility, post-transcriptional regulation, fine-tuning, efficiency, and stability.

Question 6

Why has phosphorylation become a prominent signaling mechanism?

Answer 6

It provides reversibility, speed, specificity, and allows for signal integration.

Question 7

How does a single photon activate the rhodopsin receptor?

Answer 7

The photon causes rhodopsin to change conformation, activate transducin, reduce cGMP levels, and close cation channels.

Question 8

How is rhodopsin returned to its resting state?

Answer 8

Through phosphorylation, arrestin binding, and restoration of cGMP by guanylyl cyclase.

Question 9

What is actin treadmilling?

Answer 9

A process where actin filaments add ATP-actin at the plus end and lose ADP-actin at the minus end, maintaining a constant length.

Question 10

What is a sarcomere, and how does it regulate muscle contraction?

Answer 10

The sarcomere is the functional unit of muscle contraction, with myosin sliding along actin filaments using ATP hydrolysis.

Question 11

What steps are required for cell movement?

Answer 11

Protrusion of lamellipodia, adhesion via integrins, traction by myosin, and retraction of the rear.

Question 12

What is Rac’s role in cell movement?

Answer 12

Rac promotes lamellipodia formation by regulating actin polymerization.

Question 13

What is Rho’s role in cell movement?

Answer 13

Rho drives stress fiber formation and increases contractility for retraction.

Question 14

What are the functions of caspases during apoptosis?

Answer 14

Initiator caspases activate executioner caspases, which cleave cellular components for controlled cell death.

Question 15

How does the intrinsic apoptosis pathway operate?

Answer 15

It is triggered by mitochondrial cytochrome c release, forming the apoptosome and activating caspase-9.

Question 16

How does DNA damage lead to apoptosis?

Answer 16

p53 activates pro-apoptotic proteins (Bax/Bak), which permeabilize mitochondria and trigger caspase activation.

Question 17

What is cohesin and its function?

Answer 17

A protein complex that holds sister chromatids together, ensuring proper chromosome segregation.

Question 18

What is the Ras oncogene?

Answer 18

A gene encoding a GTPase involved in cell signaling. Mutations cause constitutive activation, promoting cancer.

Question 19

What is a tumor suppressor gene?

Answer 19

A gene that inhibits uncontrolled cell proliferation. Loss of function leads to tumorigenesis.

Question 20

What is a morphogen?

Answer 20

A signaling molecule that forms gradients, directing cell fate during development.

Question 21

What is lateral inhibition, and how is it mediated by Notch signaling?

Answer 21

A process where Notch signaling ensures neighboring cells adopt different fates, crucial for tissue patterning.