Using the equation pH = -log [H+], a solution with a [H+] = 10-9 M has a pH of which of the following?

A. Methane molecule (CH4) consists of one carbon atom forming four covalent bonds with four hydrogen atoms.

B. Ammonia molecule (NH3) involves one nitrogen atom forming three covalent bonds with three hydrogen atoms.

C. Chlorine molecule (Cl2) is made up of two chlorine atoms sharing a single covalent bond between them.

D. Water molecule (H2O) has one oxygen atom forming two covalent bonds with two hydrogen atoms.

A. The excretory system is responsible for the removal of waste products from the body's metabolism, including the filtration and excretion of waste material from the blood by the kidneys.

B. The digestive system breaks down proteins into amino acids through the action of enzymes. Proteins are first denatured by stomach acid, then enzymes like pepsin begin the breakdown, which is continued in the small intestine by other enzymes such as trypsin and chymotrypsin.

C. The endocrine system consists of glands that secrete hormones into the bloodstream, which regulate processes such as growth, metabolism, and sexual development. It does not play a direct role in the breakdown of proteins into amino acids.

D. The circulatory system is responsible for the transportation of blood throughout the body, which includes nutrients, gases, and waste products, but it does not break down proteins into amino acids. This process is solely the function of the digestive system.

A. Histones are proteins that provide structural support to chromosomes. They act as spools around which DNA winds, and play a role in gene regulation.

B. Chromatin is a complex of DNA and protein found in eukaryotic cells. Its primary function is packaging long DNA molecules into more compact, dense structures. This packaging allows for DNA to fit within the cell nucleus and protects DNA structure and sequence. Chromatin also plays an essential role in regulating gene expression and DNA replication. The hereditary information of humans is encoded in the DNA.

C. ATP, or adenosine triphosphate, is the energy currency of the cell. It is used to power various biochemical reactions within the cell and is not involved in storing genetic information.

D. Plasmids are small DNA molecules within a cell that are physically separated from chromosomal DNA and can replicate independently. They are most commonly found in bacteria and are not typically involved in the storage of hereditary information in humans. Plasmids are used in biotechnology to manipulate genes and are important tools in genetic engineering.

A. Potassium, with an atomic number of 19, has one electron in its outermost shell. This makes it more likely to lose that electron to achieve a stable electron configuration, resulting in a positively charged ion or cation.

B. Oxygen, with an atomic number of 8, has six electrons in its outer shell. It is more likely to gain two electrons to fill its outer shell and become an anion, not a cation.

C. Helium, with an atomic number of 2, has a full outer shell of electrons, making it very stable and unlikely to form ions under normal conditions.

D. Fluorine, with an atomic number of 9, has seven electrons in its outer shell. It tends to gain one electron to complete its outer shell and become an anion, not a cation.

A. Centrosomes are the microtubule-organizing centers in cells, playing a critical role in the spatial arrangement of cell structures and in cell division.

B. Ribosomes are the molecular machines within the cell that facilitate the production of proteins by translating messenger RNA into polypeptide chains.

C. Mitochondria are known as the powerhouses of the cell, generating most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy.

D. Lysosomes are membrane-bound organelles that contain enzymes capable of breaking down all types of biological polymers—proteins, nucleic acids, carbohydrates, and lipids. They are essential for intracellular digestion, the recycling of a cell's organic materials, and programmed cell death (apoptosis).

A. A pivot joint allows for rotational movement around a single axis. An example of a pivot joint is the atlantoaxial joint in the neck, which allows for the rotation of the head.

B. A hinge joint permits movement in one plane, much like the opening and closing of a door.

C. The elbow and knee joints are classic examples of hinge joints, allowing for flexion and extension.

D. Gliding joints, also known as plane joints, allow for sliding movements in multiple directions within a plane. These are found in areas like the carpals of the wrist, where small bones slide against each other to allow for a range of movements.

The hip joint is a ball-and-socket joint, which is characterized by a spherical end of one bone fitting into a cup-like depression of another bone. This structure allows for a wide range of motion, including flexion, extension, abduction, adduction, and rotation. The hip joint, specifically, is formed by the articulation of the head of the femur and the acetabulum of the pelvis. It is designed for stability and weight-bearing, making it one of the most stable joints in the human body. This type of joint is also found in the shoulder, where the humerus fits into the glenoid fossa of the scapula.

A. This plate represents good antibiotic activity against Escherichia.

B. This is the plate that represents the highest number of bacteria. The bacteria that grow on this plate are the most resistant to the antibiotic because they can survive in a high concentration of the substance. In the other plates, the antibiotic inhibits the growth of the bacteria to a greater or lesser extent, depending on their sensitivity.

C. This plate represents partial antibiotic activity against Escherichia.

D. This represents no activity that may be due to inappropriate media.

A. This option is incorrect because correlation does not specify the type of relationship, only that there is a relationship. Therefore, a study could indicate a negative relationship if one exists.

B. Correlation does not imply causation; it only suggests that as one process occurs, the other process tends to occur as well. However, this does not mean one process causes the other to happen.

C. This option is incorrect because, while a study can indicate a positive relationship if one exists, the term 'correlated' alone does not specify the direction of the relationship.

D. The study indicates that Process A causes Process B. This option is incorrect because, as stated earlier, correlation does not imply causation. Without further experimental or longitudinal data to suggest a directional influence, one cannot conclude that one process causes the other.

A. Brucellosis is an infectious disease caused by the bacteria Brucella, which is transmitted from animals to humans, primarily through the consumption of unpasteurized dairy products or undercooked meat from infected animals.

B. Psoriasis is a noninfectious disease. It is a chronic autoimmune condition that results in the rapid buildup of skin cells, leading to scaling on the skin's surface. Psoriasis is believed to result from an abnormal immune response and is not contagious.

C. Chikungunya is an infectious disease caused by the Chikungunya virus, which is transmitted to humans by mosquitoes. It is characterized by fever and severe joint pain but is not classified as a noninfectious disease.

D. Dengue is an infectious disease caused by the Dengue virus, spread by mosquitoes.

Symptoms include high fever, headache, and joint pains. It is not a noninfectious disease.

A. Both endocrine and exocrine glands produce secretions that affect target cells, but the way they deliver these secretions to the target cells is different. Endocrine glands release hormones directly into the bloodstream, which then travel to the target cells, while exocrine glands secrete their products into ducts that lead directly to the target areas.

B. Nerve innervation refers to the supply of nerves to a particular part of the body or organ.

While nerve innervation can influence the activity of glands, it is not the primary distinguishing feature between endocrine and exocrine glands.

C. The biochemical nature of the secretions can vary widely among different glands, but this is not the main characteristic that differentiates endocrine from exocrine glands. Both can produce a variety of biochemical substances, including enzymes, hormones, and other compounds.

D. This is the key difference between endocrine and exocrine glands. Endocrine glands are ductless and release their hormones directly into the bloodstream, allowing them to be transported throughout the body. In contrast, exocrine glands have ducts through which they release their secretions to the surface of an organ or tissue, or to the outside of the body.