Unit 4 Test

1. Cancer cells behave differently than normal body cells. For example, they ignore signals that tell them to stop dividing. 

Which of the following conditions will most likely cause a normal body cell to become a cancer cell?

• The environment already contains cancer cells.

• 1. The environment has an abundance of nutrients.

• 1. The environment has signals that tells the cell to stop dividing.

• 1. The environment contains mutagens that induce mutations that affect cell-cycle regulator proteins.

1. In flowering plants, plasmodesmata are narrow channels through cell walls that connect the cytoplasms of adjacent cells.

An explanation of how plant cells communicate across cell walls will most likely refer to the diffusion through plasmodesmata of which of the following?

• 1. Membrane-bound organelles

• 1. Condensed, duplicated chromosomes

• 1. Branched polysaccharides

• 1. Small, water-soluble molecules

The epinephrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. A simplified model of the epinephrine signaling pathway is represented in Figure below.

Which of the following statements best describes the role of adenylyl cyclase in the epinephrine signaling pathway?

• 1. It converts a polymer to its monomer subunits.

• 1. It moves substances across the plasma membrane.

• 1. It accelerates the production of a second messenger.

• 1. It transfers phosphate groups from ATP to protein substrates.

The epinephrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. A simplified model of the epinephrine signaling pathway is represented in Figure below.

Which of the following statements best describes the epinephrine signaling pathway?

• 1. It involves the opening and closing of ion channels.

• 1. It involves enzymes activating other enzymes too.

• 1. It involves changes in the expression of target genes.

• 1. It involves protons moving down a concentration gradient.

1. Ethylene causes fruits to ripen. In a signaling pathway, receptors activate transcription factors, which ultimately leads to ripening.

Which of the following best supports the claim that ethylene initiates the signal transduction pathway that leads to ripening of fruit?

• 1. Ethylene is a simple gaseous molecule, which makes it easily detected by receptors.

• 1. Fruit will ripen in closed containers without exposure to air.

• Ethylene synthesis is under both positive and negative feedback regulation.

• Loss-of-function mutations in ethylene receptors result in changes to the ripening process.

Which of the following steps in a signaling pathway typically occurs first once a chemical messenger reaches a target cell?

• 1. Specific genes are activated.

• 1. A second messenger molecule is produced.

• 1. A ligand binds to a receptor.

• 1. Specific proteins are synthesized.

1. G proteins are a family of receptor proteins that are involved in transmitting signals from outside a cell to inside a cell. When a signaling molecule binds to a G protein, the G protein is activated. The G protein then activates an enzyme that produces a second messenger called cAMP.

Which of the following describes a critical role of cAMP here?

• 1. It carries the signal to the nucleus of the cell and results in new sequences of nucleotides being added to the cell’s DNA.

• 1. It binds the extracellular signal molecule and carries it to the intracellular target specified by the signal.

• 1. It modifies a specific monomer so that it can be added to an elongating structural macromolecule.

• 1. It results in the activation of an enzyme that amplifies the signal by acting on many substrate molecules.

 During a fight-or-flight response, epinephrine is released into the body and  is transported throughout the body. Which of the following justifies the claim that differences in components of cell signaling pathways explain the different responses to epinephrine?

• 1. Cell signaling depends on the ability to detect a signal molecule. 

• 1. Cell signaling depends on the transduction of a received signal by the nervous system. 

• 1. Cell signaling depends on the signal being able to diffuse through the cell membrane. 

• 1. Cell signaling requires reception, transduction, and response. 

1. In which step the message is translated in to response.

• Step 1

• Step 2

• Step 3

When a chromosome divides into two except the centromere is called______________

• Chromosomes

• 1. Sister chromatids.

• 1. Non sister chromatids.

• 1. Daughter chromatids.