In the following data table of an experiment carried out at 4°C (39.2 F) over 4 hours 

Solution in bag	Solution outside bag	Bag mass change (g):
water	Water	-0.2
20% sucrose	Water	+2.4
, 40% sucrose	Water	+4.3
, 60% sucrose	water	+5.8

 

Which of the following options represents the dependent variable? 

Diameter.

The diameter is the measurement of a straight line passing through the center of a circle and connecting two points on its circumference.

In this case, the line across the center of the cell represents the diameter of the cell.

Choice A, Area, is not the correct answer because area refers to the amount of space inside a two-dimensional shape.

Choice C, Volume, is not the correct answer because volume refers to the amount of space occupied by a three-dimensional object.

Choice D, Radius, is not the correct answer because radius refers to the distance from the center of a circle to its circumference and is half the length of the diameter.

Plasma B cells.

Antibodies are produced by specialized white blood cells called B lymphocytes (or B cells).

When an antigen binds to the B-cell surface, it stimulates the B cell to divide and mature into a group of identical cells called a clone.

The mature B cells, called plasma cells, secrete millions of antibodies into the bloodstream and lymphatic system.

Choice A, Natural killer cells, is not the correct answer because natural killer cells are a type of white blood cell that play a major role in the host-rejection of both tumors and virally infected cells.

Choice B, Cytotoxic T-cells, is not the correct answer because cytotoxic T-cells are a type of white blood cell that kills cancer cells, cells that are infected (particularly with viruses), or cells that are damaged in other ways.

Choice D, Helper T-cells, is not the correct answer because helper T-cells are a type of white blood cell that play an important role in the immune system by helping other white blood cells fight infections.

The two major parts of the nervous system are the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).

The CNS is made up of the brain and spinal cord and acts as the integration and command center of the body.

The PNS represents the conduit between the CNS and the body and is further subdivided into the somatic nervous system (SNS) and the autonomic nervous system (ANS).

Choice A is incorrect because it only mentions two subdivisions of the PNS, which are the autonomic nervous system (ANS) and somatic nervous system (SNS).

Choice B is incorrect because it only mentions one major part of the nervous system, which is the PNS, and one subdivision of it, which is the SNS.

Choice D is incorrect because it only mentions one major part of the nervous system, which is the CNS, and one subdivision of the PNS, which is the ANS.

Heavier objects fall faster than lighter objects.

The data in the table shows that as the number of filters (and therefore the mass) increases, the terminal velocity also increases.

This means that the heavier objects (with more filters) are falling faster than the lighter objects (with fewer filters).

Choice A is not supported by the data in the table as much as it is true.

Terminal velocity is indeed when the force of gravity is equal to air resistance, but this definition does not provide any information about the relationship between mass and terminal velocity.

Choice B is also not supported by the data in the table.

The data does not provide any information about the time it takes for an object to reach terminal velocity.

Choice D is not supported by the data in the table.

The data shows that as the number of filters increases, the terminal velocity also increases.

This means that the greater the number of filters, the greater (not smaller) the terminal velocity.

A decline in osteoblast activity while osteoclast activity continues at expected levels results in osteoporosis.

Osteoporosis is caused by an imbalance between the functioning of osteoclast and osteoblast cells.

Osteoblasts are responsible for forming new bone, while osteoclasts break down old bone.

If osteoblast activity declines while osteoclast activity continues at expected levels, this means that more bone is being broken down than is being formed, leading to a loss of bone density and an increased risk of osteoporosis.

Choice A is incorrect because an increase in osteocyte activity would not result in osteoporosis.

Osteocytes are mature bone cells that maintain the mineral concentration of the bone matrix.

Choice B is incorrect because a decline in osteoclast activity would not result in osteoporosis.

Osteoclasts break down old bone, so a decline in their activity would mean that less bone is being broken down.

Choice C is incorrect because an increase in osteocyte activity would not result in osteoporosis.

As mentioned earlier, osteocytes are mature bone cells that maintain the mineral concentration of the bone matrix.

Triple covalent bonds.

Nitrogen gas (N2) is an extremely stable molecule because it consists of two nitrogen atoms bonded together by a triple covalent bond.

A covalent bond is a type of chemical bond where atoms share electrons to form a molecule.

In a triple covalent bond, three pairs of electrons are shared between the two atoms, resulting in a very strong bond that makes the molecule extremely stable.

Choice A.

Ionic bonds is not correct because ionic bonds involve the transfer of electrons from one atom to another to form ions, which are then attracted to each other due to their opposite charges.

Nitrogen gas does not contain ions and is not held together by ionic bonds.

Choice B.

Hydrogen bonds is not correct because hydrogen bonds are weak electrostatic attractions between molecules that contain hydrogen atoms bonded to highly electronegative atoms such as oxygen or nitrogen.

Nitrogen gas does not contain hydrogen atoms and is not held together by hydrogen bonds.

Choice C.

Resonance bonds is not correct because resonance refers to the delocalization of electrons in a molecule where multiple Lewis structures can be drawn to represent the molecule.

Nitrogen gas has a single Lewis structure and does not exhibit resonance.

Calcium ions play a crucial role in initiating muscle contraction.

When a muscle cell is stimulated to contract by an action potential, calcium channels open in the sarcoplasmic membrane and release calcium into the sarcoplasm.

Some of this calcium attaches to troponin, which causes it to change shape.

This shape change exposes binding sites for myosin on the actin filaments.

Myosin’s binding to actin causes crossbridge formation, and contraction of the muscle begins.

The other ions mentioned in the question do not have this specific role in muscle contraction.

Potassium ions are important for maintaining the resting membrane potential of cells, but they do not bind to the troponin complex.

Phosphorus ions are important for energy metabolism, but they do not bind to the troponin complex.

Sodium ions are important for generating action potentials, but they do not bind to the troponin complex.

Genes that regulate cell division are found in some viruses.

When viruses cause an infection, they spread their DNA, affecting healthy cells’ genetic makeup and potentially causing them to turn into cancer.

For instance, HPV infections cause the virus’ DNA to combine with the host’s DNA, disrupting the normal function of cells.

Choice A is not correct because cancerous and normal cells sharing genetic sequences does not support the hypothesis that viruses can cause cancer.

Choice B is not correct because cellular DNA having sequences related to viral sequences does not support the hypothesis that viruses can cause cancer.

Choice C is not correct because viruses and cancer cells both replicating rapidly does not support the hypothesis that viruses can cause cancer.

Diffusion down a concentration gradient causes most of the carbon dioxide from the blood to move into the alveoli.

The alveoli are tiny air sacs in the lungs where gas exchange occurs.

Carbon dioxide is a waste product of cellular respiration and is carried by the blood to the lungs to be exhaled.

In the lungs, carbon dioxide diffuses from the blood (where its concentration is high) into the alveoli (where its concentration is lower) down its concentration gradient.

Choice A is incorrect because carbon dioxide is not converted to carbon monoxide in the body.

Choice C is incorrect because passive transport using carrier proteins is not the primary mechanism by which carbon dioxide moves from the blood into the alveoli.

Choice D is incorrect because active transport using energy is not involved in the movement of carbon dioxide from the blood into the alveoli.

A tsunami is a catastrophic ocean wave that is usually caused by a submarine earthquake.

It can also be caused by an underwater or coastal landslide, the eruption of a volcano, or the impact of a meteor or comet in a body of water.

Choice A is not correct because sunspot activity does not cause tsunamis.

Choice B is not correct because lightning strikes do not cause tsunamis.

Choice D is not correct because flooding does not cause tsunamis.