Signal Basics
What is the term for the specific cell that a signaling molecule affects?
Target Cell
What is the role of a G protein in a signal transduction pathway?
To relay the signal by binding GTP and activating an enzyme.
What type of feedback loop returns a system to its set point?
Negative feedback
What are the two main phases of the cell cycle?
Interphase and M phase
During which phase do sister chromatids separate?
Anaphase
Which type of signaling occurs between adjacent cells connected by gap junctions or plasmodesmata?
Direct contact signaling
What is a second messenger? Give an example.
A small molecule that amplifies the signal inside the cell; examples: cAMP, Ca²⁺, IP₃.
Give an example of positive feedback in humans.
Oxytocin during childbirth; blood clotting.
What occurs during the G1 checkpoint?
Cell checks for DNA damage and proper size before S phase.
What structure forms during prophase to help move chromosomes?
Mitotic spindle (made of microtubules)
Which type of signaling uses hormones that travel through the bloodstream?
Endocrine signaling
In a phosphorylation cascade, which enzyme adds phosphate groups?
Kinase
How does insulin regulate blood glucose levels?
Lowers blood sugar by promoting glucose uptake by cells.
What is the function of cyclins and CDKs?
They regulate progression through checkpoints by phosphorylating target proteins.
What is the difference between cytokinesis in plant and animal cells?
Plant cells form a cell plate; animal cells form a cleavage furrow.
What is the first step in any signal transduction pathway?
Reception — ligand binds to receptor protein.
What happens to a receptor tyrosine kinase (RTK) when its ligand binds?
It dimerizes and auto-phosphorylates.
What would happen if glucagon signaling was blocked?
Blood glucose would not increase when low — hypoglycemia.
What happens if the tumor suppressor p53 is nonfunctional?
Damaged cells continue dividing, increasing cancer risk.
If a cell begins mitosis with 24 chromosomes, how many chromosomes will each daughter cell have at the end?
24 (identical to parent cell)
Explain the difference between short-distance and long-distance signaling.
Short-distance uses local regulators; long-distance uses hormones or systemic signals.
Explain how signal amplification occurs in a cascade.
Each activated protein can activate multiple targets, multiplying the response.
Compare and contrast positive and negative feedback in terms of stability.
Negative stabilizes the system; positive amplifies until a cutoff point.
Explain how external growth factors influence the cell cycle.
They trigger signaling pathways (e.g., RTKs) that activate cyclin production to drive division.
Describe how mitosis and cytokinesis ensure genetic continuity.
Mitosis evenly separates replicated chromosomes; cytokinesis divides cytoplasm to form two identical diploid cells.