Question 1

Examine the figure below.Assume each sugar molecule represents a percentage point of sugar dissolved in the solution.Over time,the solution level on the left side of the figure would ________,while the solution level on the right side of the figure would ________.This is because the solution on the left side of the figure is ________,while the solution on the right side of the figure is ________.

Accepted Answer

A

Question 2

If the concentration of sugar molecules in water on side "A" of a selectively permeable membrane is 5 percent,and the concentration of sugar molecules in water on side "B" of a selectively permeable membrane is 15 percent,the water will

Accepted Answer

Water moves from an area of higher water concentration to an area of lower water concentration, which in this case is from side "A" (5% sugar concentration) to side "B" (15% sugar concentration). This is because the sugar molecules on side "B" effectively decrease the water concentration, creating a concentration gradient.

Question 3

The selective permeability of a phospholipid bilayer membrane can be increased with help from ________ proteins.

Accepted Answer

Transport proteins, channel proteins, and passive carrier proteins all have the ability to increase the selective permeability of a phospholipid bilayer membrane by facilitating the transport of specific molecules across the membrane. Transport proteins can actively transport molecules across the membrane, while channel proteins form pores that allow certain molecules to pass freely. Passive carrier proteins bind to a specific molecule and change shape to transport it across the membrane without using energy. Therefore, all three types of proteins can increase the selective permeability of a membrane.

Question 4

During the process of ________,water diffuses across a semipermeable membrane from an area where water is more concentrated to an area where water is less concentrated (it moves along the water concentration gradient).

Accepted Answer

The definition given in the question is of osmosis, which is the movement of water across a semipermeable membrane from a region with a high concentration of water to a region with a low concentration of water. Simple diffusion and facilitated diffusion both involve the movement of molecules across a membrane, but they do not specifically refer to the movement of water. Pinocytosis is a process in which a cell engulfs extracellular fluid to form a vesicle, and does not involve the movement of water across a membrane.

Question 5

A screen door allows breezes to enter and aromas to exit but keeps out insects.Its function most resembles

Accepted Answer

The plasma membrane of a cell serves a similar function to a screen door by allowing certain substances to pass through while keeping out unwanted ones. This is achieved through selective permeability of the membrane.

Question 6

Some antibiotics used to treat bacterial infections kill the bacteria by chemically punching holes in the cell wall of the bacteria,by preventing the bacteria from replicating their DNA,or by many other actions that ultimately cause cell death.Why do these antibiotics not work to kill viruses and cure people of viral infections?

Accepted Answer

Antibiotics are designed to target and kill bacteria by attacking their unique cell walls or DNA replication mechanisms. However, viruses are not living cells and do not have cell walls or organelles to attack. Therefore, antibiotics cannot kill viruses and are not effective in treating viral infections.

Question 7

Adenine (A),thymine (T),guanine (G),and cytosine (C)are the ________ building blocks for DNA; they are organized in different combinations to code for all of the proteins needed to accomplish everything the cell does.

Accepted Answer

Adenine, thymine, guanine, and cytosine are the four nucleotide building blocks for DNA. Carbohydrates, proteins, and lipids are not the building blocks for DNA.

Question 8

Cheryl is in a lab attempting to prepare a slide of cow blood for observation in a wet mount.She places a small drop of the blood on a slide,adds a drop of strong saline (salt)solution,and then covers all of it with a coverslip.After returning to her desk,she observes the slide with her microscope and notices that all of the red blood cells (RBCs)do not look like the nice round donut-shaped cells in her lab manual.Instead,the RBCs look very shriveled up.Her lab partner,Derek,has also made a slide,but the RBCs on his slide do look like the ones in the lab manual.Derek used a more dilute solution of saline but the same vial of blood. The most plausible explanation for the appearance of the blood cells on Cheryl's slide is that the

Accepted Answer

The shriveled appearance of the RBCs on Cheryl's slide indicates that they have lost water, which suggests that the saline solution she used was hypertonic to the RBCs. In a hypertonic solution, water moves from an area of higher concentration (inside the cell) to an area of lower concentration (outside the cell). Therefore, water would move out of the RBCs, causing them to shrink and shrivel up. Derek's use of a more dilute solution of saline would result in a solution closer to isotonicity with the RBCs, allowing water to move into and out of the cells at a relatively equal rate, resulting in the proper appearance of RBCs on his slide.

Question 9

Dialysis tubing is a selectively permeable membrane that can be filled with a solution to simulate a cell.A piece of dialysis tubing has been filled with a cloudy white solution of 5 percent starch,5 percent egg albumin (protein),and 5 percent glucose (a small sugar)dissolved in water to simulate a cell.This simulated cell is weighed and then placed in a beaker of water.After soaking in the water for one hour,the simulated cell is once again weighed. Over time,the weight of the simulated cell can be expected to

Accepted Answer

The simulated cell contains a higher concentration of solutes (starch, egg albumin, and glucose) compared to the pure water in the beaker, making the cell hypertonic relative to the beaker's hypotonic solution. Therefore, water will move into the cell through osmosis to try to equalize the solute concentration on both sides of the membrane, causing the cell to increase in weight.

Question 10

Cells naturally,without using energy,respond to changes in water concentration through the process of

Accepted Answer

Osmosis is the passive movement of water molecules from an area of higher concentration to an area of lower concentration across a selectively permeable membrane. This process doesn't require any energy, and cells naturally respond to changes in water concentration through it. Facilitated diffusion and active transport, on the other hand, require energy to move substances across the membrane against the concentration gradient, and phagocytosis is a process of engulfing large particles that also requires energy.

Question 11

Scientists repeat their experiments over and over again because they

Accepted Answer

Scientists repeat their experiments over and over again to ensure that the results were not accidental and that they are repeatable, as this is a critical part of the scientific method.

Question 12

The plasma membrane of some white blood cells contain ________ proteins that bind with proteins of cells such as bacteria that have invaded the human body.

Accepted Answer

The receptors on a white blood cell's plasma membrane are specialized proteins that can bind with proteins on the surface of invading cells, such as bacteria. This binding is an important step in the immune response. Channels, diffusion, and carriers are not typically involved in this process.

Question 13

Liposomes form spontaneously from ________ and are important because ________.

Accepted Answer

Liposomes form spontaneously from phospholipid bilayers and are important because they provide a barrier between an external environment and an internal environment. This allows for the encapsulation of drugs, DNA, or other therapeutic agents to be delivered to specific cells or tissues in the body.

Question 14

Which of the following types of organisms are single-celled (unicellular)?

Accepted Answer

Bacteria, yeast, and many protozoans are all examples of unicellular organisms, meaning they consist of a single cell. The other choices include multicellular organisms such as plants and animals.

Question 15

Phospholipids are large organic molecules with a hydrophilic,polar phosphate head connected to hydrophobic,nonpolar fatty acid tails.These molecules arrange themselves to form a mostly impermeable barrier between a liposome and its environment by lining up

Accepted Answer

Phospholipids arrange themselves in a bilayer with the hydrophobic tails facing each other in the center of the membrane and the hydrophilic heads facing outward, away from the center line of the membrane. This arrangement creates a mostly impermeable barrier between the liposome and its environment. Choice A is incorrect because hydrophobic tails cannot face outward. Choice C is incorrect because hydrophilic heads cannot face each other. Choice D is incorrect because every other tail facing outward would create an unstable, asymmetrical membrane.

Question 16

Which of the following is a part of accepted cell theory?

Accepted Answer

The accepted cell theory includes two main principles: 1) Every living organism is composed of one or more cells and 2) all living cells arise from preexisting cells. The theory also supports that cells are the basic unit of life and that all cells have membrane-enclosed organelles. However, the presence of organelles is not a defining principle of the theory. Therefore, the best choice is D which includes both principles of the cell theory.

Question 17

Which of the following accurately describes viruses?

Accepted Answer

This answer accurately describes viruses as small, non-cellular infectious agents that require a living cell to reproduce. They are typically a piece of genetic material encased in proteins and can infect a variety of hosts, including plants, animals, fungi, protozoans, and bacteria.

Question 18

Living cells have an intact phospholipid bilayer that separates the cell from its external environment; this structure is commonly referred to as the

Accepted Answer

The phospholipid bilayer is the main component of the plasma membrane, which separates the inside of the cell from the external environment. The other choices listed are organelles found within the cell and do not make up the structure of the plasma membrane.

Question 19

An experiment mixed oil (lipids),organophosphate-containing detergent in water,and copper ions to act as a catalyst for a chemical reaction.Membranes budded off of the oil in this mixture.Which of the following is a reasonable and possible explanation of the experimental results?

Accepted Answer

The chemical reaction caused the organophosphates from the detergent to chemically combine with lipids from the oil to form phospholipids with hydrophilic heads and hydrophobic tails. The hydrophobic tails lined up toward each other with their hydrophilic heads pointing out toward the water, forming a phospholipid bilayer that pulled into a spherical liposome. This is a reasonable and possible explanation of the experimental results.

Question 20

Which of the following statements best describes the differences between the nuclear envelope and the plasma membrane?

Accepted Answer

The nuclear envelope is composed of two concentric phospholipid bilayers, while the plasma membrane consists of only one. Both membranes are selectively permeable and have pores, but the difference in structure between the two results in some functional differences - for example, the nuclear envelope has specialized proteins that allow for selective transport of molecules between the nucleus and the cytoplasm.

Quiz 4: Life Is Cellular

If the concentration of sugar molecules in water on side "A" of a selectively permeable membrane is 5 percent,and the concentration of sugar molecules in water on side "B" of a selectively permeable membrane is 15 percent,the water will

The selective permeability of a phospholipid bilayer membrane can be increased with help from ________ proteins.

During the process of ________,water diffuses across a semipermeable membrane from an area where water is more concentrated to an area where water is less concentrated (it moves along the water concentration gradient) .

A screen door allows breezes to enter and aromas to exit but keeps out insects.Its function most resembles

Adenine (A) ,thymine (T) ,guanine (G) ,and cytosine (C) are the ________ building blocks for DNA; they are organized in different combinations to code for all of the proteins needed to accomplish everything the cell does.