Unit 2: Cell Structure, function, and membrane transport AP biology

If the cell is placed in a hypotonic solution, what will happen?

The cell will gain water because water will travel into the cell due to osmosis.

The passive movement of particles from a region of higher concentration to a region of lower concentration is known as...

diffusion

All eukaryotic cells contain at least one Golgi complex, typically located in the cytoplasm and near the endoplasmic reticulum. Which of the following best describes a process that occurs within the Golgi complex? a. Enzymatic modification of newly synthesized integral membrane proteins b. Synthesis of cytosolic proteins based on the nucleotide sequences of mRNAs c. Degradation of proteins by hydrolytic enzymes contained within the complex d. Synthesis of various types of lipids

a. Enzymatic modification of newly synthesized integral membrane proteins

The movement of a substance against its concentration gradient (from low concentration to high concentration) through a carrier protein is called...

active transport

The movement of a substance down its concentration gradient through a channel protein is called...

facilitated diffusion

If the concentration of oxygen in a body tissue cell is 5% and the concentration of oxygen in the blood surrounding the cell is 10%, which direction will oxygen diffuse?

Oxygen will diffuse into the body tissue cell.

A team of biologists develop a new drug, and one team member hypothesizes that the drug is incapable of freely passing across the plasma membrane and requires the help of membrane proteins to enter cells. Alternatively, another biologist on the team hypothesizes that the drug can diffuse passively across the plasma membrane like O2 and CO2 can. Which of the following, if true about the drug, best supports the alternative hypothesis that the new drug will exhibit simple diffusion across plasma membranes? a. the drug is a small, nonpolar molecule b. the drug is a small, charged molecule c. the drug is a large, polar molecule d. the drug is a large, charged molecule

A. the drug is a small, nonpolar molecule

A scientist discovers a freshwater species, Acanthamoeba polyphaga, in a local pong. Acanthamoeba polyphaga are single-celled organisms known to use endocytosis to eat smaller single-celled organisms, like bacteria. The scientist takes a water sample from the pond to study the feeding behaviors of Acanthamoeba polyphaga. Several bacteria are added to the water containing Acanthamoeba polyphaga. The initial number of bacteria added and the final number of bacteria remaining after 30 minutes were counted. What could the scientist propose as a next investigation to help determine whether Acanthamoeba polyphaga used endocytosis to eat the bacteria? a. Count the number of ribosomes inside an Acanthamoeba polyphaga cell before and after bacteria are added to a new water sample b. Count the number of vesicles inside an Acanthamoeba polyphaga cell before and after bacteria are added to a new water sample c. Count the number of bacteria that swim away from Acanthamoeba polyphaga after the bacteria are added to a new water sample. d. Count the number of Acanthamoeba polyphaga present before and after bacteria are added to a new water sample

B. Count the number of vesicles inside an Acanthamoeba polyphaga cell before and after bacteria are added to a new water sample

Organelles such as mitochondria and the endoplasmic reticulum have membranes that compartmentalize reactions and other metabolic processes. To function properly, the organelles must move substances across their membranes. Which of the following statements describes a feature shared by mitochondria and the endoplasmic reticulum that increases the efficiency of their basic functions? a. They have rigid, non fluid membranes b. They have highly folded membranes c. They have membranes composed of many carbohydrates d. They have double membranes, with one membrane enclosed within the other

B. They have highly folded membranes

A human kidney filters about 200 liters of blood each day. Approximately two liters of liquid and nutrient waste are excreted as urine. The remaining fluid and dissolved substances are reabsorbed and continue to circulate throughout the body. Antidiuretic hormone (ADH) is secreted in response to reduced plasma volume. ADH targets the collecting ducts in the kidney, stimulating the insertion of aquaporins into their plasma membranes and an increased reabsorption of water. If ADH secretion is inhibited, which of the following would initially result? a. The number of aquaporins would increase in response to the inhibition of ADH. b. The person would decrease oral water intake to compensate for the inhibition of ADH. c. Blood filtration would increase to compensate for the lack of aquaporins. d. The person would produce greater amount of dilute urine.

D. The person would produce greater amount of dilute urine.

Mitochondria are found in most eukaryotic cells and contain their own DNA and ribosomes that are similar to those typical of many prokaryotic cells. What of the following statements is justified by these observations? a. The mitochondrion is the only location in which eukaryotic cells can synthesize ATP. b. An ancestral cell most likely engulfed anaerobic prokaryote in a relationship that proved beneficial for both cells. c. Mitochondrial membranes provide abundant surface are a for reactions because of infoldings called cristae. d. The mitochondria play a role in respiration, but it also stores the cell's extra mRNA.

B. An ancestral cell most likely engulfed anaerobic prokaryote in a relationship that proved beneficial for both cells.

Plant cell walls are composed of cellulose, while fungal cell walls are composed of chitin. A group of scientists hypothesize that this difference means the cell wall has largely different functions in plant cells and fungal cells. Alternatively, another group of scientists hypothesize that despite their biochemical differences, plant and fungal cell walls serve similar functions. Which of the following observations would best support the alternative hypothesis described above? a. Plant cell walls are found just outside the plasma membrane, while fungal cell walls are found just beneath the plasma membrane. b. In both plant cells and fungal cells, the cell wall surrounds the outside of the cell membrane. c. Some plant cells have secondary cell walls that confer additional rigidity, while fungal cells do not. d. Photosynthesis occurs in plant cells, but it does not occur in fungal cells.

B. In both plant cells and fungal cells, the cell wall surrounds the outside of the cell membrane.

Why is it important for IV solutions to have salt in them? What would happen if the IV solution was pure water?

It is important for an IV solution to have salts in it because it prevents the blood cells from exploding and failing to deliver oxygen to the rest of the body. If an IV solution was pure water, it would create a hypotonic environment and the blood cells would burst, preventing them from delivering oxygen to the rest of the body.

If the sugar concentration in a cell is 3% and the concentration in the cell's environment is 5%, how can the cell obtain more sugar? (note: sugar is polar and does not pass through the phospholipid bilayer easily)

Sugar can undergo facilitated diffusion through a challed protein and no energy is required.

If the sugar concentration in a cell is 4% and the concentration in the cell's environment is 2%, how can the cell obtain more sugar?

The cell must use active transport to pump the sugar in. Energy is required.

If a cell is placed in a hypertonic solution, what will happen?

The cell will lose water to its environment because water will travel out of the cell due to osmosis.

Muscle cells have high ATP demands. Which of the following is a scientific claim about how the structure of the mitochondria in muscle cells should be different than it is in other cells because of the high energy demands of mitochondria? a. The inner membrane of the mitochondria in muscle cells should have more folds to increase the surface area, allowing more ATP to be synthesized. b. The inner membrane of the mitochondria in muscle cells should be more permeable to large enzymes, allowing the same reactions to occur in both compartments of the mitochondria. c. The outer membrane of the mitochondria in muscle cells should be thicker, allowing more rapid diffusion of molecules into the mitochondria. d. The outer membrane of the mitochondria of muscle cells should have more folds, increasing the surface area for faster diffusion of molecules from the cytoplasm.

The inner membrane of the mitochondria in muscle cells should have more folds to increase the surface area, allowing more ATP to be synthesized.

Why shouldn't you put salt on a snail?

Water leaves the slugs tissues and moves into the surrounding environment because the addition of salt onto the slug decreases the water potential on the surface of the slug. That creates areas where the water potential inside the slug is higher than on the surface and because water moves from areas of high potential to low potential, the slug loses water.

Why does water move from the roots to the tips of treetops?

Water moves up from the roots to the tips of the treetops because the roots have a water potential of about -2, but as you move up from the roots to the stems and leaves, their water potential is even lower. Therefore, the water moves up the tree because it will move from areas of high water potential to lower water potential.

A freshwater paramecium is a single celled organism. The environment the cell lives in is hypotonic to the paramecium. Water enters the cell via osmosis. To prevent lysis, excess water collect in the contractile vacuole and is pumped out. What would happen if the freshwater Paramecium was placed in salt water?

Water would begin to diffuse of the paramecium because the cell is now hypotonic to the saltwater environment and the contractile vacuole would not fill. The cell is at risk of shriveling.

Which of the following claims is scientifically accurate and consistent with an observation that a decrease in lysosome production within a cell leads to a decline in mitochondrial activity? a. A lack of lysosomes will cause a decrease in the synthesis of enzymes necessary for cellular respiration b. Fewer lysosomes will be available to break down macromolecules to provide the necessary nutrients for cellular respiration. c. Fewer lysosomes will be available to store materials required for the functioning of the mitochondria. d. Lysosomes will not be available to modify proteins so that they are targeted to the mitochondria.

b. Fewer lysosomes will be available to break down macromolecules to provide the necessary nutrients for cellular respiration.

Aquaporins are channel proteins that facilitate the transport of water across the cell membrane. One group of researchers hypothesizes that without functional aquaporins, no water will be able to enter the cell. A different group proposes an alternative hypothesis, stating that even with nonfunctional aquaporins, a small amount of water will still cross the cell membrane. An experiment is set up in which plant cells with mutated (nonfunctional) aquaporins and plant cells with normally functioning aquaporins are both placed in distilled water. Which of the following data would support the alternative hypothesis? a. Cells with functional aquaporins exhibit low turgor pressure and are hypertonic b. Cells with functional aquaporins exhibit high turgor pressure and are hypotonic c. Cells with mutated aquaporins exhibit an absence of turgor pressure and are completely plasmolyzed. d. Cells with mutated aquaporins exhibit moderate turgor pressure and are hypertonic.

d. Cells with mutated aquaporins exhibit moderate turgor pressure and are hypertonic.

Cells contain smaller components called organelles that are necessary for a cell's survival. Organelle functions have often been compared to components of larger systems. Which of the following functional differences between the rough and smooth endoplasmic reticulum (ER) is explained by the structural differences between them? a. Rough ER breaks down toxic substances, and smooth ER only transports them out of the cell b. Rough ER can synthesize and package lipids for export, and smooth ER cannot c. Rough ER can produce ATP, and smooth ER cannot. d. Rough ER can synthesize and package proteins for export, and smooth ER cannot.

d. Rough ER can synthesize and package proteins for export, and smooth ER cannot