Question 1

Cell signaling

Accepted Answer

Cell signaling can be both fast or slow, depending on the type of signal and the mechanisms involved. Some signaling pathways are very rapid, while others involve more complex processes and may be slower.

Question 2

Short-lived signaling molecules are most effective for

Accepted Answer

Short-lived signaling molecules are most effective for local cell-to-cell communication because they have a short lifespan and cannot travel long distances. This type of communication is important for coordinating cellular activities within a specific area or tissue.

Question 3

Elevated cholesterol and LDL (the particles that transport cholesterol)have been strongly associated with vascular disease; what process(es)lead to the elevated levels?

Accepted Answer

Elevated cholesterol and LDL levels are often due to excessive absorption of cholesterol from the diet by the gastrointestinal tract.

Answer: B 
 Reduced production of cholesterol by the liver can also result in elevated cholesterol and LDL levels.

Answer: C 
 Increased acceptance of cholesterol by body cells can lead to elevated levels in the bloodstream.

Answer: D 
 Reduced conversion of cholesterol into sex hormone receptor molecules is not a known cause of elevated cholesterol and LDL levels.

Question 4

Which of the following signaling molecules would NOT be found in animals?

Accepted Answer

Auxin is a plant hormone and would not be found in animals. Insulin, adrenaline, and testosterone are all hormones found in animals.

Question 5

After a sex hormone enters a target cell,it

Accepted Answer

Sex hormones, like other steroid hormones, are hydrophobic molecules that can diffuse through the cell membrane and bind to an internal receptor protein in the cytoplasm or nucleus. Once bound, this hormone-receptor complex can enter the nucleus and bind directly to specific regions of DNA, thereby regulating the expression of target genes. This process is known as gene transcription, which ultimately leads to changes in the cellular function and behavior of the target cell.

Question 6

Elevated HDL (high-density lipoprotein)levels seem to provide positive cardiovascular health effects,even for individuals with abnormally high blood cholesterol.What best describes the beneficial action of HDL?

Accepted Answer

HDL collects surplus cholesterol from peripheral tissues and transports it to the liver, reproductive, and adrenal glands where it is converted to bile or hormones. This helps to lower the levels of LDL (low-density lipoprotein) or "bad" cholesterol in the blood, and reduces the risk of plaque buildup in the arteries. HDL also has anti-inflammatory properties and may help to prevent oxidative damage to blood vessels.

Question 7

Muscle cells require high concentrations of calcium to function properly.As a result,these cells use ________ transport to move calcium from areas of low concentration outside the cell into the cytoplasm.

Accepted Answer

The answer of Muscle cells require high concentrations of calcium...

Question 8

Water moves across a membrane from a hypotonic solution to a ________ solution.

Accepted Answer

The answer of Water moves across a membrane from a...

Question 9

Which of the following statements about hormones is FALSE?

Accepted Answer

Hormones are used by multicellular organisms as long-range signaling molecules that are transported in the body by fluids. Option A, B, and D are all true statements about hormones.

Question 10

Hydrophilic signaling molecules

Accepted Answer

Hydrophilic signaling molecules are incapable of passing through the hydrophobic interior of the plasma membrane. Therefore, they bind to the extracellular domain of membrane-bound receptors, triggering a signaling cascade within the cell without entering the cell itself. Examples of hydrophilic signaling molecules include peptide hormones, cytokines, and neurotransmitters.

Question 11

Signaling molecules can be "tagged" by attaching glow-in-the-dark molecules to them.After adding tagged signaling molecules to the fluid around several cells,you observe the cells with a microscope designed to see the glow-in-the-dark molecules.After a few minutes,you notice that the plasma membrane of some of the cells begins to glow.This observation indicates that some cells

Accepted Answer

The glow-in-the-dark molecules are attached to the signaling molecules, allowing them to be detected by the microscope. If the plasma membrane of some cells begins to glow, it indicates that the cells have receptors for the tagged signaling molecule and are responding to it. This would not be possible if the cells had no active carrier proteins or were blocking the signaling molecules. The density of the plasma membrane is not relevant to this observation.

Question 12

Soon after a certain molecule enters a cell,the cell begins producing a new type of protein.The molecule was probably a

Accepted Answer

Hydrophobic hormones are able to cross the cell membrane and bind to intracellular receptors, which then lead to the production of specific proteins. Therefore, the presence of a new protein suggests that a hydrophobic hormone was involved.

Question 13

The concentration of solutes is higher within the mitochondria than it is in the cytosol.Therefore,the cytosol is ________ to the inside of the mitochondrion.

Accepted Answer

The answer of The concentration of solutes is higher within...

Question 14

A concentration ________ is said to exist when a molecule is more abundant in one area than it is in another.

Accepted Answer

The answer of A concentration ________ is said to exist...

Question 15

Some hormones,like thyroxine,affect most or all body cells,while others only affect a single organ or type of cell.This is because of variations in

Accepted Answer

The distribution of receptors for a hormone determines which organs or cells will be affected. All cells or organs with receptors for the hormone will respond to its signal.

Question 16

The passive movement of water across a selectively permeable membrane is called ________.

Accepted Answer

The answer of The passive movement of water across a...

Question 17

The human hormone insulin is produced only by a single organ,the pancreas,yet insulin is used to move glucose from the bloodstream into cells all over the body.What aspect of hormones makes it possible for insulin to work throughout the body?

Accepted Answer

Hormones are long-range signaling molecules that can travel through the bloodstream to reach target cells throughout the body. Insulin is able to work throughout the body because it is released into the bloodstream by the pancreas and can then travel to target cells in various tissues and organs.

Question 18

For a cell to be a target for a particular hormone,it must usually

Accepted Answer

For a hormone to have an effect on a cell, it needs to bind to a specific receptor on the surface of the cell membrane or within the cell. Without a receptor for that hormone, the cell cannot be a target for its action. The other options do not necessarily relate to the ability of the cell to respond to a hormone.

Question 19

Lipids often move within the body in complexes known as lipoproteins; what advantage does this strategy provide?

Accepted Answer

Lipoproteins provide a means of regulating the delivery of lipids to cells by allowing for specific receptors on the cell membrane to recognize and selectively take up the lipids as needed. Additionally, lipoproteins can be removed from circulation and metabolized by the liver or excreted by the kidneys, preventing an excess buildup of lipids in tissues.

Question 20

Many hormones are large and hydrophilic.Where would you expect the receptor proteins for these hormones to be located?

Accepted Answer

If the hormones are hydrophilic, they cannot pass through the hydrophobic interior of the cell membrane, so the receptor proteins for these hormones need to be located on the cell membrane with the hormone-binding site exposed to the cell exterior. In this way, the hormone can bind to the receptor on the extracellular surface and trigger a cascade of intracellular signaling events to produce a response. Choice A cannot be correct as the hydrophilic hormone cannot bind to a receptor located on the interior of the cell, and choice B is unlikely as the hydrophilic hormone cannot pass through the hydrophobic portion of the cell membrane. Choice C cannot be correct as the hydrophilic hormone cannot enter the cytoplasm directly.

Quiz 4: Cell Membranes, Transport, and Communication