Final Exam True/False

Talking to people at a party is similar to paracrine signaling while a radio announcement is similar to autocrine signaling.

False; Talking to people at a party is similar to paracrine signaling because the cell communicates with cells close to it in paracrine signaling. The second part is false because autocrine signaling is intracellular signaling, so it is more similar to talking to yourself.

All cells respond to the same signal in the same way.

False; Different cells respond to signals in different ways. Even though they may receive the same signal, each cell type will respond differently

Actin filaments, microtubules, and immediate filaments have ends with defined polarity.

False; actin filaments and microtubules have ends with defined polarity. Intermediate filaments have structures on their tales that make them nonpolar.

Tight junctions have one function.

False; they have two functions. One is to restrict flow of molecules between barriers and the other is to restrict diffusion from apical to basolateral and vice versa.

ER-bound and free ribosomes are structurally and functionally different.

False; they are structurally and functionally the same. The only difference is the proteins that they are making.

Like the lumen of the ER, the interior of the nucleus is topologically equivalent to the outside of the cell.

False; Because of nuclear pores, the interior of the nucleus is topologically equivalent to the interior of the cell. The lumen of the ER is topologically equivalent to the outside of the cell.

Yeast cells growing anaerobically consume glucose at the same rate after addition of oxygen

False; In the presence of oxygen, yeast cells consume glucose at a slower rate. Anaerobically, they consume consume glucose faster and produce less ATP.

All cells have similar mechanisms.

True; All cells use ATP, have transcriptional regulators, use RNA as an intermediate. These illustrate that they have similar mechanisms.

Continual addition and removal of phosphates by protein kinases and protein phosphatases in an unnecessary waste of energy.

False; Addition and removal of phsophates are important for regulation and are necessary.

Nucleosomes bind DNA so tightly that they cannot move from the positions where they are first assembled

This statement is false because chromatin remodeling complexes are able to utilize ATP hydrolysis to move nucleosomes up and down a gene sequence. They also have the ability to completely degrade nucleosomes

not all cells are replaced at the same rate; neurons are rarely replaced while gut cells are