In which type of tissue would you find a fibrous protein that provides strength and protection to the body, particularly in the skin, hair, and nails?

A. It increases the activation energy required for the reaction.

B. It decreases the activation energy required for the reaction.

C. It has no effect on the activation energy required for the reaction.

D. It increases the rate of reaction but has no effect on the activation energy.

The correct answer is choice B.

It decreases the activation energy required for the reaction.

A catalyst provides a new reaction pathway in which a lower activation energy is offered.

This allows more reactant molecules to collide with enough energy to surmount the smaller energy barrier, increasing the rate of reaction 2.

Choice A, It increases the activation energy required for the reaction, is not the correct answer because it describes the opposite effect of a catalyst.

Choice C, It has no effect on the activation energy required for the reaction, is not the correct answer because a catalyst does have an effect on activation energy.

Choice D, It increases the rate of reaction but has no effect on the activation energy, is not the correct answer because a catalyst increases the rate of reaction by decreasing the activation energy.

A. Estrogen

B. Progestin

C. Thyroxine

D. Androgen

The correct answer is choice C. Thyroxine.

Thyroxine (T4) is a hormone produced by the thyroid gland that controls your body’s metabolism, the process in which your body transforms the food you eat into energy.

Choice A, Estrogen, is not the correct answer because it is a hormone responsible for the development of female secondary sexual characteristics.

Choice B, Progestin, is not the correct answer because it is a synthetic form of progesterone used in hormonal birth control and hormone replacement therapy.

Choice D, Androgen, is not the correct answer because it is a hormone responsible for the development of male secondary sexual characteristics.

A. A short piece of double-stranded DNA that binds to the template DNA and acts as a "starter" for the polymerase.

B. A short piece of double-stranded DNA that binds to the primer and acts as a "starter" for the template.

C. A short piece of single-stranded DNA that binds to the template DNA and acts as a "starter" for the polymerase.

D. A short piece of single-stranded DNA that binds to the polymerase and acts as a "starter" for the template.

A primer is a short single-stranded DNA fragment used in certain laboratory techniques, such as the polymerase chain reaction (PCR).

In the PCR method, a pair of primers hybridizes with the sample DNA and defines the region that will be amplified.

Choice A) A short piece of double-stranded DNA that binds to the template DNA and acts as a “starter” for the polymerase is incorrect because primers are single-stranded, not double-stranded.

Choice B) A short piece of double-stranded DNA that binds to the primer and acts as a “starter” for the template is incorrect because it does not make sense for a primer to bind to itself.

Choice D) A short piece of single-stranded DNA that binds to the polymerase and acts as a “starter” for the template is incorrect because primers bind to the template DNA, not to the polymerase.

Note: DNA primers are used instead of RNA primers in DNA sequencing and PCR because DNA is more stable, specific, and compatible with the enzymes and processes involved in these techniques.

A. The attraction between the relatively positive areas of one molecule and the relatively negative areas of another molecule.

B. The repulsion between the positive and negative charges of two molecules.

C. The attraction between two nonpolar molecules.

D. The attraction between two ionic molecules.

Hydrogen bonding is an interaction involving a hydrogen atom located between a pair of other atoms having a high affinity for electrons.

One atom of the pair (the donor), generally a fluorine, nitrogen, or oxygen atom, is covalently bonded to a hydrogen atom, whose electrons it shares unequally; its high electron affinity causes the hydrogen to take on a slight positive charge.

The other atom of the pair (the acceptor), also typically F, N, or O, has an unshared electron pair, which gives it a slight negative charge.

Mainly through electrostatic attraction, the donor atom effectively shares its hydrogen with the acceptor atom, forming a bond.

Choice B) The repulsion between the positive and negative charges of two molecules is incorrect because hydrogen bonding involves attraction, not repulsion.

Choice C) The attraction between two nonpolar molecules is incorrect because hydrogen bonding involves polar molecules.

Choice D) The attraction between two ionic molecules is incorrect because hydrogen bonding involves polar molecules and not ionic molecules.

A. To separate DNA fragments by size.

B. To amplify specific regions of DNA.

C. To sequence DNA fragments.

D. To analyze protein expression levels.

The correct answer is choice B.

To amplify specific regions of DNA.

PCR (polymerase chain reaction) is a laboratory technique used to make many copies of a specific region of DNA.

The goal of PCR is to make enough of the target DNA region that it can be analyzed or used in some other way.

PCR has many research and practical applications, including DNA cloning, medical diagnostics, and forensic analysis of DNA.

Choice A is incorrect because PCR does not separate DNA fragments by size. Choice C is incorrect because PCR does not sequence DNA fragments.

Choice D is incorrect because PCR does not analyze protein expression levels.

A. Adaptive immunity

B. Antibodies

C. Innate immunity

D. T cells .

Innate immunity represents the first line of defense to an intruding pathogen.

The innate immune system is a series of nonspecific defenses that make up the innate immune system.

These defenses are not directed against any one pathogen but instead provide a guard against all infection.

Choice A is incorrect because adaptive immunity is activated when pathogens are able to bypass innate immune defenses.

Choice B is incorrect because antibodies are part of the adaptive immune system and are produced by B cells.

Choice D is incorrect because T cells are part of the adaptive immune system and assist B cells or directly kill infected cells.

A. Ribosome

B. Nucleus

C. Mitochondria

D. Plasma membrane.

The plasma membrane is the organelle that encapsulates the contents of the cell and plays a vital role in regulating the movement of substances in and out of the cell.

It is a selectively permeable barrier that separates the internal environment of the cell from the external environment.

Choice A is incorrect because ribosomes are organelles involved in protein synthesis, not in regulating the movement of substances in and out of the cell.

Choice B is incorrect because the nucleus is an organelle that contains the cell’s genetic material, not in regulating the movement of substances in and out of the cell.

Choice C is incorrect because mitochondria are organelles involved in energy production, not in regulating the movement of substances in and out of the cell.

A. Thymus

B. Parathyroid

C. Adrenal

D. Pituitary

The correct answer is choice A. Thymus.

The thymus is a primary lymphoid organ located in the mediastinum.

It plays a key role in the maturation and differentiation of T-lymphocytes.

Choice B.

Parathyroid is incorrect because the parathyroid glands are small endocrine glands located in the neck that produce parathyroid hormone, which regulates calcium levels in the blood.

Choice C.

Adrenal is incorrect because the adrenal glands are endocrine glands located above the kidneys that produce hormones such as cortisol and adrenaline.

Choice D.

Pituitary is incorrect because the pituitary gland is an endocrine gland located at the base of the brain that produces hormones that regulate growth, metabolism, and reproductive functions.

A. Perforins.

B. Cytokines.

C. Granzymes.

D. Interferons.

Granzymes.

Granzymes are a family of serine proteases that are stored in and secreted from the cytotoxic granules of cytotoxic T lymphocytes (CTL) and natural killer (NK) cells.

They work in synergy with perforin, a pore-forming toxin, to induce apoptosis in target cells.

Perforin is necessary for the delivery of granzyme B to the target cell cytosol where caspase-dependent and -independent pathways to apoptosis are activated.

Perforins (choice A) are pore-forming toxins that work in synergy with granzymes to induce apoptosis in target cells.

Cytokines (choice B) are signaling molecules that regulate immune responses but do not directly induce apoptosis in target cells.

Interferons (choice D) are a type of cytokine that play a role in immune responses but do not directly induce apoptosis in target cells.

A. They are the same.

B. Atomic mass is always greater than mass number.

C. Atomic mass and mass number are not related.

D. Atomic mass is very close to mass number but with some deviation in the decimal places.

Atomic mass is very close to mass number but with some deviation in the decimal places.

Atomic mass is also known as atomic weight and is the weighted average mass of an atom of an element based on the relative natural abundance of that element’s isotopes.

The mass number, on the other hand, is a count of the total number of protons and neutrons in an atom’s nucleus.

Choice A is incorrect because atomic mass and mass number do not mean the same thing.

Choice B is incorrect because atomic mass is not always greater than mass number.

Choice C is incorrect because atomic mass and mass number are related.