V1.1 - AP U4 2020

Researchers investigating the regulation of neurotransmitter release from presynaptic neurons proposed a model (Fig. 1) in which CDK5, a protein expressed in axon terminals, inhibits the movement of synaptic vesicles to the presynaptic membrane.

To test their model, the researchers used a modified version of green flourescent protein (GFP*). In slightly alkaline conditions, GFP* exhibits a bright green flourescence. In acidic conditions GFP* exhibits no flourescence. Using standard techniques, the gene encoding GFP* is easily introduced into living cells. By engineering the expression of GFP* in laboratory-cultured nerve cells, the researchers found that a bright green flourescence was exhibited only when a pre-synaptic neuron was given a certain stimulus.

Many human cells can be stimulated to divide by hormonelike growth factors that bind to receptor proteins (R) on the plasma membrane and trigger an internal signal-transduction cascade. In many cases, however, the process of contact inhibition prevents mitosis when cells are in direct contact with one another. Contact inhibition occurs when proteins called cell adhesion molecules (CAMs) interact, causing them to change shape so that the growth-factor signaling proteins that normally associate with CAMs are replaced by another protein, called M. Both pathways are depicted in the figures below.

Which of the following statements accurately uses the information presented to support the hypothesis that interruption of M function in a single body cell can result in cancer?

The following questions refer to the data in Figures 1 through 4 below, which were collected during a study of the growth of plant seedlings.

When the concentration of GA₁ is highest, the average height of the control seedlings is approximately

If chemical signals in the cytoplasm control the progression of a cell to the M phase of the cell cycle, then fusion of a cell in G1 with a cell in early M phase would most likely result in the

The endocrine system incorporates feedback mechanisms that maintain homeostasis. Which of the following demonstrates negative feedback by the endocrine system?

Which of the following diagrams best represents hormone-activated gene expression?

What happens during anaphase?

What part of cellular division is this cell going through?

Inflammatory responses may include which of the following?

An otherwise healthy student in your class is infected with EBV, the virus that causes infectious mononucleosis. The same student had already been infected when she was a child, and she had merely experienced a mild sore throat and swollen lymph nodes in her neck. This time, though infected, she does not get sick. Which cells were responsible for producing the antibodies the FIRST time she got sick?

Which of the following is true?

An individual’s humoral response to a particular antigen differs depending on whether or not the individual has been previously exposed to that antigen. Which of the following graphs properly represents the humoral immune response when an individual is exposed to the same antigen more than once?

Which of the following representations best shows a portion of an axon at rest (before or after an action potential)?

Information is transmitted through the nervous system when one neuron signals another neuron. The structure of neurons enables transmission to proceed quickly and efficiently. Which of the following diagrams correctly identifies both the structure of neurons and the direction of information flow between neurons?

What property would prevent the ligands of cell-surface receptors from entering the cell?

Human papillomavirus can cause cervical cancer. The virus itself produces a protein called E6. E6 is a protein that binds p53, which is a protein produced by a common tumor supressor gene.

Based on this fact and what you know about tumor suppressor genes, what effect do you think E6 binding has?

What is the main prerequisite for clearance at the G2 checkpoint?

Quorum sensing is triggered to begin when

___________.

When are CDKs PRESENT inside the cell during the cell cycle?

In the diagram above, notice that cyclin levels CYCLE (get the name now?), and MPF (maturation promoting factor, a specific name of a cyclin/CDK complex) follows the same pattern. When cyclin levels are high, MPF activity is high, and vice versa. The height of activity peaks at M phase. This tells us that the role of this active complex is to move through M phase, and then cyclin levels, and MPF activity levels, drop off quickly after that.

Given all this information, what do you know about associated CDK levels during the time shown on this graph?

What is your null hypothesis?

Write a formal statement about the results of the experiment.