Question 1

In which stage of mitosis do the identical sets of chromosomes uncoil and resume their chromatin form?

Accepted Answer

Telophase is the last stage of mitosis where the identical sets of chromosomes reach the opposite poles of the cell, the nuclear envelope reforms around each set, and the chromosomes uncoil and resume their chromatin form.

Question 2

If active transport establishes a concentration gradient with the use of ATP, then the concentration gradient can be looked at as ________.

Accepted Answer

The concentration gradient established by active transport represents potential energy that can be harnessed when molecules passively diffuse down the gradient. This is the basis for many important physiological processes, such as respiration and photosynthesis. The other answer choices are incorrect because they do not accurately reflect the role of the concentration gradient in active transport.

Question 3

Which of the following is a principle of the fluid mosaic model of cell membrane structure?

Accepted Answer

The principle of the fluid mosaic model is that phospholipids form a bilayer that is largely impermeable to water-soluble molecules. This allows for the selective transport of molecules across the membrane. The model also states that proteins are embedded within and fluidly move throughout the lipid bilayer, rather than being contained in a layer on the outside of the cell. The phospholipid bilayer is also fluid, not solid, at body temperature. The structure of the phospholipid molecule consists of a polar head and a nonpolar tail made of two fatty acid chains, not three.

Question 4

Which of the following statements is most correct regarding the intracellular chemical signals known as "second messengers"?

Accepted Answer

Cyclic AMP and calcium are both examples of second messengers that transmit signals inside cells. They act as mediators between extracellular signals, such as hormones or neurotransmitters, and intracellular responses, like gene expression or modulating enzyme activity. Option A is incorrect because second messengers often activate protein kinase enzymes, which are involved in many intracellular signaling pathways. Option C is incorrect because there are no receptors called K-proteins; second messengers act through a variety of receptors, depending on the specific signaling pathway involved. Option D is incorrect because second messengers do not act to remove nitric oxide from the cell; nitric oxide can act as a second messenger itself, and is involved in many intracellular signaling pathways.

Question 5

The lungs deliver a regular supply of oxygen to the blood, which is in turn circulated to most all the cells of the body. At the same time oxygen is consumed during aerobic cellularrespiration within these cells. This implies that ________.

Accepted Answer

Oxygen will passively diffuse into the cells due to the concentration gradient created by the cells constantly consuming oxygen during aerobic cellular respiration. Active transport of oxygen is not required for the majority of cells in the body. The rate of oxygen diffusion is dependent on concentration, with a steeper gradient facilitating a faster rate of diffusion.

Question 6

If a human cell were to increase the amount of cholesterol embedded within its plasma membrane which of the following would most likely happen?

Accepted Answer

Increasing the amount of cholesterol in the plasma membrane would decrease its fluidity and increase stability. This is because cholesterol has a stabilizing effect on the phospholipid bilayer and decreases the movement of phospholipids, making the membrane less permeable. It would not directly cause the formation of a plaque, increase permeability to ions, or make the membrane more fluid and less stable.

Question 7

The main component of the cytosol is ________.

Accepted Answer

The main component of the cytosol is water, which makes up about 70-80% of its total volume. While proteins, salts, and sugars are present in the cytosol, they are not the main component.

Question 8

Which of the following will not speed up the net rate of diffusion for glucose into a cell?

Accepted Answer

Decreasing the number of phospholipids in the plasma membrane will likely decrease the rate of diffusion for glucose as it reduces the fluidity of the membrane and decreases the number of available transport channels. The other options will increase the net rate of diffusion for glucose into the cell.

Question 9

Some hormones enter cells via________.

Accepted Answer

Hormones often bind to specific receptors on the surface of target cells, triggering receptor-mediated endocytosis and allowing the hormone to enter the cell. Pinocytosis and exocytosis are not typically involved in hormone uptake, and primary active transport generally requires ATP and is not a common mechanism for hormone entry.

Question 10

Cancerous cells can divide so rapidly that they will often produce a glycocalyx that is different than the other cells in the body. This may result in ________.

Accepted Answer

The glycocalyx is a glycoprotein and glycolipid covering that surrounds the cell membranes, significantly influencing cell-cell recognition, communication, and immune response. A different glycocalyx on cancerous cells can lead to the immune system recognizing these cells as foreign, potentially leading to their destruction. This is because the immune system is designed to identify and eliminate cells that are not recognized as part of the body, including cells that have undergone malignant transformation and exhibit abnormal surface markers.

Question 11

A cell engulfing a relatively large particle will likely utilize ________.

Accepted Answer

Phagocytosis is the process by which a cell engulfs a relatively large particle such as a bacterium or a cell debris. Pinocytosis is the process by which a cell takes in small dissolved molecules and exocytosis is the process by which a cell releases materials outside of the cell. Receptor-mediated endocytosis is the process by which specific molecules are taken up by a cell using receptors on the cell membrane. None of these are specifically designed to engulf large particles like phagocytosis.

Question 12

The functions of centrioles include ________.

Accepted Answer

Centrioles are responsible for organizing the microtubules of the mitotic spindle during cell division. They play a crucial role in ensuring proper chromosome distribution during cell replication.

Question 13

Crenation (shrinking) is likely to occur in blood cells immersed in ________.

Accepted Answer

Crenation (shrinking) occurs in blood cells when they are immersed in a hypertonic solution, which means the solution has a higher concentration of solutes compared to the inside of the cell. This causes water to move out of the cell, leading to shrinkage or crenation.

Question 14

Bone is a connective tissue that provides support for the body with its strength and rigidity.Which of the following provides the best explanation for how this is so?

Accepted Answer

Bones are composed of a dense extracellular matrix made up of collagen fibers and minerals such as calcium and phosphate. This combination creates a hard and rigid structure that provides support for the body. The bone cells, or osteocytes, secrete this matrix and also help maintain it through their cytoplasmic extensions that connect to other osteocytes and allow for communication and nutrient exchange.

Question 15

The movement of water across the plasma membrane can be described by all of the followingexcept ________.

Accepted Answer

Carrier-mediated facilitated diffusion does not typically describe the movement of water across the plasma membrane. Water primarily moves through simple diffusion or facilitated diffusion via aquaporins, and both of these processes are types of passive membrane transport.

Question 16

If a cell is non-selectively engulfing samples of extracellular fluid, for example to absorb nutrients, it will likely utilize ________.

Accepted Answer

Non-selective engulfing of extracellular fluid is referred to as pinocytosis. This process involves the ingestion of small vesicles, which are formed from the plasma membrane. Pinocytosis does not require specific receptors and is an indiscriminate process. Phagocytosis, on the other hand, involves the ingestion of larger particles and typically requires specific receptors. Exocytosis is the process by which cells secrete substances out of the cell. Receptor-mediated endocytosis involves the specific uptake of molecules that bind to receptors on the cell surface.

Question 17

The myocardium (cardiac muscle tissue) undergoes a significant amount of physical stress due to its contractions. You would expect to see relatively large numbers of which of the following embedded within their plasma membrane?

Accepted Answer

Desmosomes are intercellular junctions that anchor adjacent cells together and distribute mechanical stress throughout the tissue. Given that the myocardium undergoes significant physical stress, it is likely that there would be a relatively large number of desmosomes present in the cardiac muscle tissue. Tight junctions are responsible for preventing the leakage of materials between cells and are not directly involved in distributing mechanical stress. Transport proteins and glycolipids are not specific to cardiac muscle tissue and would not be expected to be present in larger numbers than in other types of tissues.

Question 18

If a tRNA had an AGC anticodon, it could attach to a(n)________ mRNA codon.

Accepted Answer

The anticodon on tRNA pairs with a complementary codon on mRNA during translation. The AGC anticodon pairs with the UCG codon due to complementary base pairing rules (A-U, G-C).

Question 19

A gene can best be defined as________.

Accepted Answer

A gene is a segment of DNA that carries the instructions for one polypeptide chain. This definition is the most accurate as it encompasses the definition of a gene as a unit of inheritance that carries genetic information and guides the synthesis of a specific protein or RNA molecule. Option A is incorrect as noncoding segments of DNA are not necessarily genes. Option B is incorrect as a three-base triplet is a codon, not a gene. Option C is partially correct as RNA messenger molecules carry genetic information, but not all RNA molecules are messenger RNAs, and not all genes code for polypeptides through messenger RNA intermediates.

Question 20

Which of the following would not be restricted (limited) by low levels of ATP?

Accepted Answer

Osmosis is the passive movement of water molecules from an area of high concentration to an area of low concentration. This process does not require ATP as it occurs spontaneously due to the concentration gradient. Exocytosis, pinocytosis, and phagocytosis all require ATP as they are active processes that involve the movement of molecules or particles against their concentration gradient. Thus, low levels of ATP would restrict these processes but not osmosis.

Quiz 3: Cells: the Living Units