Which of the following describes one difference between skeletal muscles and cardiac muscles?

The correct answer is D. Cardiac muscles contain intercalated discs, whereas skeletal muscles do not. Intercalated discs are unique features of cardiac muscle cells, providing a structural and functional connection between adjacent cells. Skeletal muscles lack intercalated discs.

The correct answer is C. 9. The pH is determined by taking the negative logarithm (base 10) of the hydrogen ion concentration ([H+]). In this case, -log(10^(-9)) equals 9, so the pH of the solution is 9.

To find the pH of a solution with a hydrogen ion concentration ([H+]) of \(10^{-9}\) M using the equation \(pH = -\log[H^+]\):

\[ pH = -\log(10^{-9}) \]

Now, since \( \log(10^{-9}) = -9 \), the negative sign before the logarithm makes the value positive:

\[ pH = -(-9) = 9 \]

Therefore, the solution has a pH of 9

The correct answer is B. Atoms become cations by losing electrons. Potassium has one electron in its outermost shell, and it is more likely to lose that electron to achieve a stable, cationic state. Fluorine, helium, and oxygen are more likely to gain electrons and form anions.

The correct answer is C. A spectrophotometer measures the amount of light absorbed or transmitted by a substance in a liquid. Turbidity, caused by suspended particles, can be assessed by measuring the reduction in light transmission through the sample. The other tools listed are not specifically designed for measuring turbidity.

The pharynx is primarily composed of muscle tissue. It plays a role in swallowing and is part of both the respiratory and digestive systems, which requires coordinated muscular activity.

The correct answer is A. This option describes a chemical reaction known as the reaction of water with sodium, producing hydrogen gas. Chemical reactions involve the breaking and forming of chemical bonds, and in this case, sodium reacts with water to produce hydrogen gas and sodium hydroxide.

Phosphates are found in both DNA and cell membranes. In DNA, they form part of the backbone structure, linking the nucleotides together. In cell membranes, phosphates are a component of phospholipids, which are critical to the membrane's structure and function.

Independent assortment occurs during metaphase I when homologous chromosome pairs line up randomly at the cell’s equator. This randomness contributes to genetic variation because the distribution of maternal and paternal chromosomes into gametes is different each time meiosis occurs.

When a proton is emitted from the nucleus of an atom, the atomic number (Z) decreases by 1 because a proton has a positive charge, and it's effectively removing one positive charge from the nucleus. However, the atomic mass (A) remains the same because protons and neutrons contribute to the atomic mass, and the emission of a proton does not affect the number of neutrons.

The correct answer is C. Biological macromolecules are large, complex molecules essential for life. Nucleic acids, such as DNA and RNA, are examples of biological macromolecules. They are composed of nucleotides and play a crucial role in genetic information storage and transfer.

Nucleic acid, is also an example of a biological macromolecule. Nucleic acids are large molecules made up of nucleotides, which consist of a nitrogenous base, a sugar molecule, and a phosphate group. DNA and RNA are examples of nucleic acids, and they play crucial roles in storing and transmitting genetic information within cells. Therefore, both Protein) and Nucleic acidare correct examples of biological macromolecules.