cell membrane retake

Which mechanism requires energy? (1.) facilitated diffusion (2.) osmosis (3.) diffusion (4.) active transport

4- active transport. Pretty much a definition of active transport, that it requires energy.

In pond water, protozoans pump out excess water by means of their (1.) pellicle (2.) trichocyst (3.) cell membrane (4.) contractile vacuole (5.) pseudopodia

4. (from the osmoregulatory strategies lecture)

Which substance would have normally have the LEAST difficulty crossing a cell membrane? (1.) water (2.) protein (3.) carbohydrate (4.) salt (5.) there would be little difference in any of the above

4. Salt. Salt dissociates into ions. Ions slip in between the phospholipids. (I also accepted water, which has little trouble crossing because of aquaporins.)

A plant cell has a water potential of -0.8 bars and a solute potential of -1 bars. What is the pressure potential? (If you show your work circle your answer.)

0.2, because -1 plus 0.2 = -.8

If a solution outside a cell is more concentrated so that the cell loses water to its environment, the external solution is said to be __________ to the cell contents. (1.) hypertonic (2.) in equilibrium (3.) isotonic (4.) hypotonic

1- hypertonic. The solution outside has more. More = hyper

Each student in a biology laboratory received two solutions. One solution was distilled water. The other was a salt solution with concentrations of salts slightly greater than that of a living cell. The solutions were labeled X and Y, respectively. The students were instructed to place some fresh-water protozoans in each of the solutions and to identify the solutions on the basis of their observations. The protozoans in solution X shriveled. Those in solution Y swelled up and burst. 5. These results indicate that (1.) solution X was salt water (2.) solution Y contained killer protozoans (3.) solution Y was salt water (4.) solution X was distilled water (5.) solution X was tap water

1- x was salt water, so it drew water out of the protozoan just like salt draws water out of a slug

The rate of transport of a substance into a cell is drastically reduced when the formation of ATP is blocked. The transport system must be a form of (1.) active transport (2.) simple diffusion (3.) facilitated diffusion (4.) both active transport and simple diffusion (5.) both simple and facilitated diffusion

1. If blocking the formation of ATP slows it down, it must have been active transport, because only active transport relies on ATP

In osmosis, water always moves toward the ____ solution: that is, toward the solution with the ____ solute concentration. (1.) isotonic ... greater (2.) hypertonic ... greater (3.) hypertonic ... lesser (4.) hypotonic ... greater (5.) hypotonic ... lesser

2 - hypertonic (greater) Because the solution with the highest solute concentration has the lowest water concentration, so water will move there by diffusion.

The current theory of the structure of the plasma membrane includes freely moving phospholipids with embedded proteins, and is best described by the _______ model. (1.) sandwich (2.) fluid-mosaic (3.) unit membrane (4.) electrochemical (5.) unipermeable

2- fluid mosaic. (fluid because the phospholipids are freely moving. Mosaic because the embedded proteins form a mosaic.)

Phospholipid molecules in a membrane are arranged with their ____ on the exterior and their ____ on the interior. (1.) hydrophobic heads ... hydrophilic tails (2.) hydrophilic heads ... hydrophobic tails (3.) nonpolar heads ... polar tails (4.) hydrophobic tails ... hydrophilic heads (5.) hydrophilic tails ... hydrophobic heads

2. Hydrophilic heads on the outside because there's water out there Hydrophobic tails on the inside, away from the water

11. The concentration of calcium in a cell is 0.3%. The concentration of calcium in the surrounding fluid is 0.1%. How could the cell obtain more calcium? (1.) passive transport (2.) diffusion (3.) active transport (4.) osmosis (5.) any of the prior methods could be used

3- active transport. The calcium would be moving toward the area of higher concentration (uphill) which always requires energy

Pinching in of fluids by a unicellular organism is the process of (1.) phagocytosis (2.) osmosis (3.) endocytosis (4.) exocytosis (5.) facilitated diffusion

3- endocytosis. (endo = in) Phagocytosis would be taking in a large solid particle.

Certain types of lymphocytes (white blood cells) in the lymph nodes ingest bacteria and debris. This function most likely occurs by (1.) exocytosis (2.) passive transport (3.) phagocytosis (4.) pinocytosis (5.) facilitated transport

3- phagocytosis - taking in a solid (the bacterium)

Each student in a biology laboratory received two solutions. One solution was distilled water. The other was a salt solution with concentrations of salts slightly greater than that of a living cell. The solutions were labeled X and Y, respectively. The students were instructed to place some fresh-water protozoans in each of the solutions and to identify the solutions on the basis of their observations. The protozoans in solution X shriveled. Those in solution Y swelled up and burst. The protozoans in solution X shriveled because (1.) an antagonistic substance was placed into the solution (2.) their membranes were more permeable to the passage of water than the organisms in Y (3.) osmotic pressure failed to operate (4.) there was a net movement of water from the protozoans (5.) golgi bodies in the test organisms lost their function

4. there was a net movement of water from the protozoans

A ______ protein allows a particular molecule or ion to freely cross the plasma membrane as it enters or exits the cell. (1.) cell-recognition (2.) glycoprotein (3.) receptor (4.) enzymatic (5.) transport or channel

5- transport. (Transport refers to transporting across the membrane.)

A beaker of distilled water sits on a lab counter. What is the solute potential, pressure potential, . and water potential (in that order) of the beaker of water? a. 0, 0, and 0 b. 0, 1, and 1 c. 1, 1, and 1 d. 1, 1, and 2

A, All zeros, by definition.

Which of these byproducts of protein breakdown must be excreted along with the largest amount of water? a. ammonia b. urea c. uric acid d. aquaporin

A. ammonia. Which is why freshwater fish are the only ones to use this strategy. They need to get rid of a lot of water anyway.

An Na/K pump is an example of both a. cotransport and active transport c. sodium transport and phosphorus transport b. osmoregulation and exocytosis d. the glory and the futility of life

A. cotransport because the ions have to be transported together. Active transport because it requires energy.

A protein which extends all the way from the outside to the inside of a cell membrane a. integral b. peripheral c. plasma d. exoskeletal

A. integral, because it is "integrated" into the membrane.

A selectively permeable membrane is permeable a. to some molecules, but not all of them b. in hypotonic, but not hypertonic solutions c. to water only when water is needed d. when no molecules can pass through it

A. it "selects" which molecules to be permeable to

A protein on the outer surface of a cell membrane, with a chain of a dozen or so sugars attached. a. integral protein b. glycoprotein c. motor protein d. dystrophin

B, glycoprotein. (the "glycol" refers to the sugar chain)

Production of uric acid from ammonia wastes takes a lot of energy to produce. What's the benefit . of excreting wastes in this form? a. it is a hilarious form of revenge against the car-driving public b. it requires very little water c. uric acid enables an animal to osmoconform with terrestrial environments d. uric acid raises the water potential of an animals blood as it is excreted

B. Requires little water. Which is why this strategy is favored by flying organisms - they don't have to be weighed down by a lot of water to use for excretory purposes.

Seabirds concentrate salt for excretion from their salt glands using the same mechanism moose use for concentrating heat in their core, and the same mechanism a kidney uses for concentrating urea. It's called a. facilitated diffusion b. countercurrent system c. hyperloop system d. osmoconformity

B. countercurrent system. Osmoregulatory strategies lecture.

Molecules of a glucose will diffuse a. toward areas of highest total solute concentration b. with energy input from ATP c. down the glucose concentration gradient d. to areas with low pressure potential

C. down the glucose gradient. (the presence of other solutes doesn't matter)

What was the point of the experiment in which scientists fused a human cell and a mouse cell? a. it was part of a paternity test ordered by lawyers representing Tom Cruise b. It demonstrated that both species' cell had the same types of glycoproteins c. it demonstrated that many membrane proteins can drift laterally d. it demonstrated that humans and mice have phospholipids adapted to temperate climates

C. from the membrane structure lecture.

What is the primary source of water for a kangaroo rat? a. only filtered bottled waters, never tap. b. atmospheric water that condenses on their respiratory membranes c. metabolic water, produced in dehydration synthesis reactions such as the building of proteins d. water gained in the conversion of ammonia wastes to urea

C. same lecture

Which substance is important to the structure of the cell membrane because it helps the cell membrane maintain its fluidity? (1.) cellulose (2.) cholesterol (3.) lipid bilayer (4.) protein

Cholesterol. (from the membrane structure notes and the membrane POGIL)

What would you (correctly) use Benedict's solution for? a. keeping a tissue sample alive so it can be studied b. testing for the presence of starch or other polysaccharides c. measuring the rate of osmotic water loss through a membrane d. testing a sample for the presence of a sugar such as fructose

D. Test for sugar. (from the cellulose tubing lab)

Sharks live in the ocean (usually) and have no scales to prevent water loss. What is their unusual . adaptation to deal with this problem? a. staying angry b. they store the water produced by dehydration reactions c. they breathe with gills rather than lungs, to prevent additional water loss d. they store high amounts of urea in their tissues to make their fluid isotonic to the ocean

D. from the osmoregulatory strategies lecture

Osmoregulation is best defined as a. controlling the rate of osmosis by constricting or relaxing aquaporins b. a positive feedback system, since it helps to maintain life c. an exception to the rule of water potential d. maintaining a constant water or solute concentration regardless of environment

D. maintaining. (A might make sense, but it doesn't happen. Positive feedback systems don't sustain life. There are no exceptions to the rules of water potential.)

Does water always flow from areas of high solute potential to areas of low solute potential? Why or why not?

No. Pressure potential can "overpower" the influence of solute potential.

An aquarium is divided in half by a membrane that is permeable only to water. The left side of the aquarium is filled with 1 molar glucose solution. The right side is filled with 1 molar NaCl solution. Which way will water move? Left, right, or neither (equilibrium.) And why?

One point for the direction, one point for the reason. (If you said the wrong direction, but gave the reason that would support your wrong answer, you got one point.) Direction: to the right Reason: salt dissociates into 2 ions. Sugar doesn't. The "i" in the solute potential calculations for salt is 2. For sugar it is 1.

A high pressure potential in plant cells causes turgor pressure (crispness) in plants. What does it cause in animal cells, and why?

Swelling or explosion because animal cells don't have cell walls. (you have to answer the "why?" part to get credit)