Which of the following is the main function of centrosomes in animal cells?

 

The corpus luteum is a structure that develops in the ovary after an egg has been released.

It secretes the hormone progesterone, which prepares the uterus for a fertilized egg to implant and helps maintain the uterine lining during pregnancy1.

Choice A.

Umbilical cord is not correct because it is a structure that connects the developing fetus to the placenta and provides nutrients and oxygen to the fetus, but does not secrete hormones.

Choice C.

Oviduct is not correct because it is a tube that transports eggs from the ovary to the uterus, but does not secrete hormones.

Choice D.

Oocyte is not correct because it is an immature egg cell, but does not secrete hormones.

In DNA, the nitrogenous bases adenine (A) and thymine (T) pair together, while cytosine (C) and guanine (G) pair together.

Therefore, the complementary strand of the given DNA sequence 3' TCGATCGCA 5' would have the complementary nitrogenous bases as:

5’ AGCTAGCGT 3’

NOTE: The 5’ to 3’ direction of the complementary strand is opposite to that of the given strand.

Choice A.

3’ AGCTAGCGT 5’ is not correct because it is not complementary to the given strand.

Choice C.

5’ UCGAUCGCA 3’ is not correct because it contains uracil (U), which is a nitrogenous base found in RNA, not DNA.

Choice D.

3’ TCGUTCGCU 3’ is not correct because it also contains uracil (U), which is a nitrogenous base found in RNA, not DNA.

The best reason for the prolonged preservation of the body is that it was frozen in the cold temperature of the Alps shortly after he died and remained frozen until it was found.

Freezing can preserve a body by slowing down or stopping the decomposition process.

Choice A is not correct because the food that the person ate would not have contained toxins that killed the bacteria that would have otherwise destroyed the body.

Choice B is not correct because the arrow wound would not have caused blood to flow out of the body in a way that would have cleared enzymes that break down tissue from the body.

Choice D is not correct because ultraviolet rays at high altitude would not have caused all of the body’s molecules to be preserved.

A catalyst is a substance that increases the rate of a chemical reaction without being consumed by the reaction.

As a result, the reaction is completed in a shorter amount of time.

Choice B is not correct because using a catalyst does not necessarily result in the formation of a more desirable product.

Choice C is not correct because using a catalyst does not necessarily result in the release of a greater amount of heat energy by the reaction.

Choice D is not correct because using a catalyst does not necessarily increase the yield of product.

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.

A myocardial infarction affects the coronary blood vessels of the heart.

A myocardial infarction, commonly known as a heart attack, occurs when blood flow decreases or stops in the coronary artery of the heart, causing damage to the heart muscle 1.

Choice B is incorrect because the aorta is not a blood vessel of the heart.

The aorta is the main artery that carries oxygenated blood from the heart to the rest of the body.

Choice C is incorrect because the pulmonary blood vessels are not affected by a myocardial infarction.

The pulmonary blood vessels carry deoxygenated blood from the heart to the lungs.

Choice D is incorrect because the vena cava is not a blood vessel of the heart.

The vena cava is a large vein that carries deoxygenated blood from the body to the heart.

A totipotent cellcan self-renew by dividing and develop into the three primary germ cell layers of the early embryo and into extra-embryonic tissues such as the placenta.

A fertilized egg is a totipotent stem cell and as such can develop into any specialized cell found in the organism.

Choice A is not correct because totipotent cells do not fight infectious diseases.

Choice B is not correct because totipotent cells do not aid in the maturation of sex cells.

Choice C is not correct because totipotent cells do not carry electrical impulses.

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.

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.

The cytoskeleton of a cell is comprised of protein fibers that provide structural support and help maintain the shape of the cell.

These protein fibers include microfilaments, intermediate filaments, and microtubules.

Choice A.

Carbohydrates is not the correct answer because carbohydrates are a type of macromolecule that provides energy to cells and are not a component of the cytoskeleton.

Choice B.

Nucleic acids is not the correct answer because nucleic acids are macromolecules that store and transmit genetic information and are not a component of the cytoskeleton.

Choice C.

Lipids is not the correct answer because lipids are a type of macromolecule that makes up cell membranes and are not a component of the cytoskeleton.