AP BIOLOGY MIDTERM REVIEW Unit 4

Prophase

Nuclear membrane dissolves and chromatin is coiled into discreet chromosomes. Spindle fibers begin to extend from the centrosomes.

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

After a meal, blood glucose levels become elevated, stimulating beta cells of the pancreas to release insulin into the blood. Excess glucose is then converted to glycogen in the liver, reducing blood glucose levels.

G1 phase of Interphase

Cell grows while carrying out unique cell functions.

G2 phase of Interphase

Continues to grow and carry out functions.

Cytokinesis

Cytoplasm is divided, cleavage furrow forms in animal cells, cell plate forms in plant cells.

Epinephrine is a protein hormone found in many animals. Epinephrine stimulates a signaling pathway that results in the breakdown of glycogen to glucose in the liver cells. Which of the following describes the initial steps in the process whereby epinephrine stimulates glycogen breakdown?

Epinephrine binds to a cell-surface receptor; the activated receptor stimulates production of the second messenger, cAMP .

Which of the following is true of mitosis? a. It maintains the same chromosome number in the daughter cells as in the parent cell. b. It is the last phase of interphase. c. It regulates the transfer of genetic information from one daughter cell to another. b. It is also known as cytokinesis.

It maintains the same chromosome number in the daughter cells as in the parent cell.

A researcher examining a root tip observes a plant cell with condensed sister chromatids, kinetochores with attached microtubules, and individual chromosomes that are aligned at the equatorial plate of the cell. Which of the following best describes what the next process will be in the cell?

Paired chromatids will separate, and the new daughter chromosomes will move toward opposite poles of the cell.

Cell communication is critical for the function of both unicellular and multicellular eukaryotes. Which of the following is likely true of cell signaling?

Similar cell signaling pathways in diverse eukaryotes are evidence of conserved evolutionary processes.

Anaphase

Sister chromatids come apart, pulled by spindle fibers so opposite ends of the cell contain complete and equal sets of DNA.

DNA replication occurs

during the S phase of the cell cycle

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

exiting of both cells from the cell cycle and into the G0 phase

Researchers investigating the regulation of neurotransmitter release from presynaptic neurons proposed a model (Figure 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 fluorescent protein (GFP*). In slightly alkaline conditions, GFP* exhibits a bright green fluorescence. In acidic conditions, GFP* exhibits no fluorescence. 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 fluorescence was exhibited only when a presynaptic neuron was given a certain stimulus. Based on the model, which of the following best explains how regulation of neurotransmitter release might increase the range of responses to a stimulus in the nervous system?

Different neurons in the same neural network can release different amounts of neurotransmitter.

Antidiuretic hormone (ADH) is important in maintaining homeostasis in mammals. ADH is released from the hypothalamus in response to high tissue osmolarity. In response to ADH, the collecting duct and distal tubule in the kidney become more permeable to water, which increases water reabsorption into the capillaries. The amount of hormone released is controlled by a negative feedback loop. Based on the model presented, which of the following statements expresses the proper relationship between osmolarity, ADH release, and urine production?

As tissue osmolarity rises, more ADH is released, causing less water to be excreted as urine.

Stages of Interphase

G1, S, G2

S phase of Interphase

Duplicates chromosomes by replication. 92 DNA

Ethylene is an organic compound produced by ripening fruits. In a controlled experiment, researchers found that ethylene gas stimulated the ripening process in newly harvested fruits. Which of the following describes the most likely connection between natural ethylene production and fruit ripening?

Ethylene gas is a chemical signal through which ripening fruits trigger the ripening process in other fruits.

Researchers investigating the regulation of neurotransmitter release from presynaptic neurons proposed a model (Figure 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 fluorescent protein (GFP*) . In slightly alkaline conditions, GFP* exhibits a bright green fluorescence. In acidic conditions, GFP* exhibits no fluorescence. 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 fluorescence was exhibited only when a presynaptic neuron was given a certain stimulus. Which of the following observations best supports the hypothesis that CDK5 negatively regulates neurotransmitter release?

Inhibition of CDK5 activity in neurons increases the movement of synaptic vesicles to the plasma membrane in response to a specific stimulus.

Metaphase

Microtubles move chromosomes to the equator of the cell. Spindles attach to chromatids in the middle.

Telophase

Nuclear envelopes reform around the sets of chromosomes. Chromatin fibers less condensed and the nucleus divides.

During mitosis, which of the following normally occurs?

Replicated chromosomes line up on the equatorial plate.

Most cells that have become transformed into cancer cells have which of the following characteristics when compared to normal, healthy cells?

Shorter cell cycle