Cell Communitcation Slideshow Questions

Why most some ligands bind to the membrane doesn’t while others can diffuse directly into the cytoplasm?

Small non-polar ligands pass through the hydrophobic bilayer, while ligands that can’t pass through need cell surface receptors. Small hydrophobic ligands diffuse easily through the membrane and bind to internal receptors.

If a receptors shape were mutated, how would that affect the cell’s ability to imitate a signal transduction pathway?

The ligand wouldn’t be able to bond, blocking signals and cause inactivity. The “lock and key” wouldn’t fit, so the signal wouldn’t be carried out correctly, affecting the cells ability to initate signal transduction pathway.

How does the structure of a G protein fit its function compared to a kinase?

It’s by the membrane since that’s were the receptors are located, acting as an on/off switch. Don’t directly change the shape of the effector proteins. Kinases phosphorites proteins. Directly changing the shape of it. It’s located in the cytoplasm.

Why is it a “resource management” benefit for the cell to use a multi-step transduction pathway instead of a one-step process?

It requires less energy and resources. 1 ligand triggers thousands of molecules in the cell. Less enzymes and still more activated molecules. The cell’s ability makes corrections if something goes wrong, if something does go wrong everything is messed up.

If a protein phosphatase was insinuated and could not remove phosphate groups, what would happen to the cellular response?

Proteins would stay phosphorylated (active). The signal pathway would never turn off. The cell would keep responding even without a signal. This could leads to problems like uncoupled cell growth (cancer).

How does a signal removes at the cell membrane eventually result in a change to the DNA inside the nucleus?

Signal activates a cascade of proteins. Protein kinases activate transcription factors. Transcription factors move into the nucleus. They bind to DNA and turns genes on/off. This changes proteins the cell makes.

Why is negative feedback more common than positive feedback in biological systems?

It’s essential for maintains homeostasis, which is required for life. It’s a corrective mechanism that prevents changes. where positive feedback increases changes, casting instability.

How does the body use two different hormones to regulate a single set point?

The pancreas regulates blood glucose levels by using insulin to lure high blood sugar and glucagon to raise low blood sugar. These work fed a part of the negative feedback system for as stable energy supply.

In the case of cholera, why does the inability to turn a signal “off” lead to a life-threatening medical emergency?

It permanently activates an enzyme that forces intestinal cells to continuously pump out massive amounts of water and electrolytes. The inability to turn this process off leads to rapid dehydration, diarrhea, and death within hours.

How can a mutation in a single relay protein lead to unregulated cell growth?

It turns a signaling pathway permanently on, sending continuous division commands to the nucleus. These mutations often convert proto-onocogens into active onocogens, causing RAS to remain active, leading to factors like cancer.

Why is it an evolutionary advantage for bacteria to use “quorum sensing” to coordinate group behavior?

Bacteria can synchronize gene expression, providing an advantage with the ability to become resistant to antibiotics quickly and release toxins. Allowing bacteria to have defensive and offensive advantages because of adaptability.

How does the chemical “ polarity” of a signaling molecule determine where it’s receptor must be located?

If a chemical is polar, then it cannot get through the cell membrane unassisted, so they bind to the outside and use a secondary Messenger to carry the signal to its destination.

How are growth factors and cyclins like a relay race?

A growth factor starts a pathway that eventually activates cyclins, which push the cell into division.

CdK vs cyclin?

CdKs stay at constant levels. Cyclins rise and fall during the cell cycle.

What happens if the G1 checkpoint is skipped?

The cell divides with damaged DNA, causing more mutations and possible cancer.