Bio Exam 2- (Ch. 1, 3, 5, 6.4)

Which of the following is a difference between active transport and facilitated diffusion?

Active transport requires the expenditure of cellular energy, and facilitated diffusion does not. (Active transport can move substances against the concentration gradient, but it requires energy, usually in the form of ATP.)

Using the data from the graphs and what you know about membranes and metabolic pathways, predict which of the following is the likely reason why actions of aquaporins in a membrane can change so rapidly.

Aquaporins are inserted into the membrane as needed.

Cells A and B are the same size and shape, but cell A is metabolically quiet and cell B is actively consuming oxygen. Oxygen will diffuse more quickly into cell _____ because _____.

B ... the diffusion gradient there is steeper (As long as a metabolically active cell consumes oxygen as it enters, diffusion into the cell will continue because the concentration gradient favors movement in that direction. Cell A is using less oxygen than cell B.)

Green olives may be preserved in brine, which is a 20-30% salt solution. How does this method prevent contamination by microorganisms?

Bacteria can't survive in a hypertonic solution because they lose water. (If a cell is placed in a hypertonic solution, it will lose water to its environment, shrivel, and probably die.)

How do the data in Figure A relate to the data in Figures B and C?

Figure C is essentially a summary of the data in Figure A.

A group of single cell organisms collected from the ocean was brought into the lab for examination. The lab assistant was concerned that the water had become full of toxic waste products and so added clean water to the culture. All of the organisms died, and when she looked at them under the microscope, all she could see were bits and pieces of them scattered throughout the water. What likely happened?

She added water that was hypotonic to the cell and they ruptured.

In the lab, you use a special balloon that is permeable to water but not sucrose to make an "artificial cell." The balloon is filled with a solution of 20% sucrose and 80% water and is immersed in a beaker containing a solution of 40% sucrose and 60% water. Which of the following will occur?

Water will leave the balloon

When in solution, a molecule that moves slowly across an artificial membrane moves rapidly across a plasma membrane. This molecule rapidly enters the cell regardless of whether its concentration is higher inside or outside the cell. Using this information, which transport mechanism is most likely to be responsible for the movement of the molecule across a plasma membrane?

active transport (Some transport proteins can move molecules against their concentration gradient in a process called active transport.)

Utah's Great Salt Lake has an average salinity seven times higher than that of the oceans. Very few multicellular organisms live in this harsh environment. An example is the brine shrimp, which must devote a large portion of its metabolic energy to osmoregulation. These brine shrimp must _____.

actively pump water back into their cells to counter its loss due to osmosis

You have isolated a cell that is unable to produce cholesterol for its cell membranes. Which of the following defects is the cell most likely to have?

cell wouldn't have the right fluidity

Phagocytosis is to eating as pinocytosis is to

drinking

A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. These molecules probably enter the cells lining the baby's digestive tract via _____.

endocytosis (Endocytosis is the procedure that cells use to import large molecules across their membranes.)

Certain cells that line the stomach synthesize a digestive enzyme and secrete it into the stomach. This enzyme is a protein. Which of the following processes could be responsible for its secretion?

exocytosis

Imagine beaker A has 10% sucrose solution and B has 8%. Beaker A would be considered ___

hypertonic

New drugs are being developed to lower levels of circulating cholesterol. A successful drug would be one that _____.

increases the rate of LDL receptor-mediated endocytosis (Because cholesterol levels in the blood reflect the balance of, addition to, and removal of cholesterol, anything that tips the balance in favor of removal will lower the concentration of circulating cholesterol. Increasing LDL receptor-mediated endocytosis will have exactly this effect.)

Some protozoans have special organelles called contractile vacuoles that continually eliminate excess water from the cell. The presence of these organelles tells you that the environment

is hypotonic to the protozoan.

If you were to add olive oil to your food as part of a diet to lower your risk of atherosclerotic disease, you would use olive oil that

is liquid at room temperature

Which compound would you couple with a drug for better uptake by a cell?

lipids

A diet high in animal products and hydrogenated vegetable margarine may increase the risk for atherosclerosis. This is because

most animal fats are saturated and many hydrogenated vegetable margarines contain high levels of trans fats.

Below are the structures of three fatty acids, palmitic acid, stearic acid, and oleic acid. What combination of these fatty acids could you use to make a fat that is liquid at room temperature?

one palmitic acid, one stearic acid, and one oleic acid

The process of a white blood cell engulfing a bacterium is

phagocytosis