(Question)
Answer the following question given this paragraph: Potassium Concentration Glial cells, especially astrocytes, are responsible for maintaining the chemical environment of the CNS tissue. The concentrations of ions in the extracellular fluid are the basis for how the membrane potential is established and changes in electrochemical signaling. If the balance of ions is upset, drastic outcomes are possible. Normally the concentration of K+ is higher inside the neuron than outside. After the repolarizing phase of the action potential, K+ leakage channels and the Na+/K+ pump ensure that the ions return to their original locations. Following a stroke or other ischemic event, extracellular K+ levels are elevated. The astrocytes in the area are equipped to clear excess K+ to aid the pump. But when the level is far out of balance, the effects can be irreversible. Astrocytes can become reactive in cases such as these, which impairs their ability to maintain the local chemical environment. The glial cells enlarge and their processes swell. They lose their K+ buffering ability and the function of the pump is affected, or even reversed. One of the early signs of cell disease is this "leaking" of sodium ions into the body cells. This sodium/potassium imbalance negatively affects the internal chemistry of cells, preventing them from functioning normally. Q: One of the early signs of cell disease is this "leaking" of what into the body cells? Choices: - proteins - potassium ions - glucose - sodium ions A:
(Answer)
sodium ions

(Question)
Answer the following question given this paragraph: Each protein has its own unique sequence and shape held together by chemical interactions. If the protein is subject to changes in temperature, pH, or exposure to chemicals, the protein structure may change, losing its shape in what is known as denaturation as discussed earlier. Denaturation is often reversible because the primary structure is preserved if the denaturing agent is removed, allowing the protein to resume its function. Sometimes denaturation is irreversible, leading to a loss of function. One example of protein denaturation can be seen when an egg is fried or boiled. The albumin protein in the liquid egg white is denatured when placed in a hot pan, changing from a clear substance to an opaque white substance. Not all proteins are denatured at high temperatures; for instance, bacteria that survive in hot springs have proteins that are adapted to function at those temperatures. Q: Each protein has its own unique sequence and shape held together by chemical interactions. if the protein is subject to changes in temperature, ph, or exposure to chemicals, the protein structure may change, losing its shape in what is known as this? Choices: - extraction - fermentation - gastrulation - denaturation A:
(Answer)
denaturation

(Question)
Answer the following question given this paragraph: A tight junction is a watertight seal between two adjacent animal cells (Figure 3.17b). Proteins hold the cells tightly against each other. This tight adhesion prevents materials from leaking between the cells. Tight junctions are typically found in the epithelial tissue that lines internal organs and cavities, and composes most of the skin. For example, the tight junctions of the epithelial cells lining the urinary bladder prevent urine from leaking into the extracellular space. Also found only in animal cells are desmosomes, which act like spot welds between adjacent epithelial cells (Figure 3.17c). They keep cells together in a sheet-like formation in organs and tissues that stretch, like the skin, heart, and muscles. Gap junctions in animal cells are like plasmodesmata in plant cells in that they are channels between adjacent cells that allow for the transport of ions, nutrients, and other substances that enable cells to communicate (Figure 3.17d). Structurally, however, gap junctions and plasmodesmata differ. Q: What is the term for a watertight seal between two adjacent animal cells? Choices: - cell membrane - cell wall - placental barrier - tight junction A:
(Answer)
tight junction