Correct answer: (2) excretory system-remove potentially dangerous materials from the body

The primary organ of the excretory system is the kidney, which filers the blood to remove wastes, thereby maintaining homeostasis. The basic unit of the kidney is a nephron, which serves as a filtering unit. As blood flows through the nephron and then to the capillaries of the glomerulus in high pressure, water, glucose, vitamins, amino acids, protein waste products, salts, and ions from the blood pass out of the capillaries into the Bowman's capsule. Since blood cells and most proteins are too large to pass through the walls of the capillaries, these components are retained in the blood vessels.

From the Bowman's capsule, the filtered liquid passes through a u-shaped tubule where most of the ions and water, and all of the glucose and amino acids are reabsorbed into the bloodstream to maintain homeostasis. Thus, excess water, waste molecules, and excess ions become urine, which flows out of the kidneys through the ureter, then into the urinary bladder, and, after which, exits the body through the urethra.

Incorrect answers:

(1) immune system-intake and distribution of oxygen to cells of the body

The immune system protects the body against invasion of disease-producing agents such as bacteria, fungi, and viruses. The body system in charge of intake and distribution of oxygen to the cells of the body is the respiratory system.

(3) digestive system-transport energy-rich molecules to cells

The main function of the digestive system is to disassemble ingested food into its simpler form so that it can be used as energy for the body. The transport of energy-rich molecules to cells is a function of the circulatory system.

(4) circulatory system-produce building blocks of complex compounds

Correct answers: (2) active transport, recognition of chemical messages, protection

The cell membrane is a semi-permeable membrane that separates and protects the cell from the outside environment. It controls the passage of molecules and ions in and out of the cell through passive or active transport. During passive transport, substances move through diffusion, while in active transport, energy and transport molecules are used to move substance through the cell membrane against concentration or electrochemical gradient.

Incorrect answers:

(1) protein synthesis, respiration, digestion of food molecules

Ribosomes are the sites where cell assembles proteins. On the other hand, respiration occurs in the mitochondria and digestion of molecules is a function of lysosomes.

(3) enzyme production, elimination of chemical messages, duplication of DNA codes

Lysosomes are membrane-enclosed sacs of hydrolytic enzymes that the cell uses to eliminate macromolecules. These enzymes can hydrolyze proteins, complex sugars, fats, and nucleic acids. DNA replication or duplication of DNA codes occurs in the nucleus.

(4) release of ATP molecules, regulation of cell reproduction, food production

Correct answer: (3) weakened viruses associated with the infection

Vaccines are harmless variants or derivatives of pathogenic microbes that stimulate the immune system to mount defenses against the actual pathogen. The term vaccine came from the word "vacca" which means cow in Latin. Edward Jenner, an English physician, formulated the first vaccine against smallpox virus in 1796. He learned from his patients in farm country that milkmaids who had slight cowpox (a milder disease that usually infect cows) were resistant to subsequent smallpox infections. He did his experiment by scratching a boy with a needle that contains a fluid from a sore of a milkmaid who had cowpox. The boy was later exposed to smallpox and he resisted the disease.

Incorrect answers:

(1) live bacteria that ingest viruses

Vaccines may contain weaker versions of pathogenic bacteria, but these will not ingest viruses. The bacteria will turn on the defense system of the body so that when the stronger bacteria invade the system, it has already formed the resistance against them.

(2) white blood cells from an infected individual

White blood cells are naturally occurring components of the blood produced by the hematopoietic stem cell that are involved in the defense against pathogens.

(4) a variety of microbes that will attack the virus

Correct answer: (2) have the same genetic information but perform different specialized functions

Almost all cells in the body contain the same DNA or genetic information. However, not all genes in the DNA are expressed in all body parts. Expression of the genes is dependent of the function of the cells. For example, only the genes that code for the function of the heart are expressed in the cells of the cardiac muscles.

Incorrect answers:

(1) produce a hormone involved in respiration

The heart is an organ of the circulatory system which pumps blood all throughout the body. Thus, the statement is only true for lungs, which is the primary organ for respiration.

(3) use one part of the genetic code to synthesize all enzymes needed by the cell

Genetic codes are represented by nucleic acids that code for the formation of proteins like enzymes. Thus, different genetic codes are needed to form various types of enzymes depending on their structure and function.

(4) contain different numbers of DNA molecules

Correct answer: (1) four types of base subunits

Each cell has a nucleus, where most of the genetic information is stored. In the nucleus, there are chromosomes, composed of coiled DNA molecules. Each segment of the DNA corresponds to a gene. Genes are made up of four types of nitrogenous bases-adenine, guanine, thymine, and cytosine. The combination of these bases will dictate which amino acids will be formed, which in turn will compose a protein (Kindly confirm).

The four macromolecules of life are protein, carbohydrate, lipids, and nucleic acids. Each of these is entirely different from the other, with different structures and functions.

Incorrect answers:

(2) folded chains of glucose molecules

A glucose unit is an example of a monosaccharide, which is a simple sugar or carbohydrate. A gene is a portion of the DNA, which is a nucleic acid.

(3) twenty different kinds of amino acids

Amino acid is the basic unit of a protein. Genes, which code (The word "code" seems awkward. Kindly explain this jargon further.) for the expression of proteins, are composed of nucleic acids which is an entirely different kind of macromolecule.

(4) complex, energy-rich inorganic molecules

Correct answer: (1) foreign antigens

Antigens are foreign molecules that do not belong to the host organism and that elicit an immune response. Pathogens, such as viruses and bacteria, are the usual antigens encountered by the body. When an organ is transplanted from another individual (donor), some of the molecules in that organ may be recognized as foreign and harmful by the host's immune system. Thus, drugs are necessary to suppress the immune system from recognizing the components of the new organ as antigen.

Incorrect answers:

(2) foreign antibodies

Antibodies are antigen-binding immunoglobulins produced by the B cells that function as the effectors in an immune response. Antibodies are formed after the immune system recognizes the presence of an antigen. The immune system will only form antibodies in the donated organ once the system recognizes the presence of antigens.

(3) DNA molecules

The organ is composed of body cells that contain the DNA. However, the expression (the term "expression" seems awkward. Is this a jargon?) of the genes in the DNA do not elicit an immune response.

(4) pathogenic microbes

Correct answer: (2) Blood flow throughout the entire body is suddenly reduced.

When blood flow is suddenly reduced, the individual encounters cardiac arrest, which is caused by the failure of the heart (an organ) to contract. Since the blood carries oxygen to the other parts of the body, such as the brain, this may also cause loss of consciousness and abnormal breathing. If this lasts for several minutes, it may cause brain injury.

Incorrect answers:

(1) The ovary releases estrogen, which quickly binds to cell receptors.

This is a normal biological condition. Ovary releases estrogen that binds to its receptors.

(3) White blood cells release enzymes in response to the proteins on inhaled pollen.

White blood cells are blood components responsible for fighting infections, such as allergy-causing pollens.

(4) Mitochondria stop functioning in unicellular organism exposed to pollutants

Correct answer: (2) A-glucose, B-O₂, C-enzymes, D-CO₂

The biological process illustrated is called respiration, a process that occurs in all eukaryotes. Through this process, glucose (C₆H₁₂O₆) and oxygen (O₂) are converted into carbon dioxide (CO₂), water, and energy by the use of specific enzymes. This is important in living organisms because through this process, stored energy (in the form of adenosine triphosphate or ATP) is made available to carry out significant biological processes such as locomotion and cellular transport.

Incorrect answers:

(1) A-O₂, B-CO₂, C-glucose, D-enzymes

This formula does not represent cellular respiration. Oxygen and carbon dioxide cannot produce glucose and water because hydrogen is absent in the reactant.

(3) A-enzymes, B-O₂, C-CO₂, D-glucose

This formula does not represent cellular respiration. Enzymes are proteins that serve as catalysts in reactions. Catalysts are chemical agents that change the rate of reaction but are not consumed during the reaction. Thus, an enzyme cannot be used as a reactant; it is only an agent in the rate of the reaction.

(4) A-glucose, B-CO₂, C-enzymes, D-O₂

Cell structure number: 3

The cell structure represented by number 3 is called the mitochondrion (mitochondria, plural). This organelle serves as the site of cellular respiration, the process where sugar is broken down to form chemical energy in the form of adenosine triphosphate (ATP). ATP is important in various activities that occur in the nucleus (structure 2), such as DNA transcription.

The initial breakdown of protein occurs in the stomach through the action of pepsin. The environment is highly acidic to facilitate the conversion of pepsinogen into pepsin. Pepsin digests proteins and converts them into peptides or amino acids. However, this pH level (the pH level of which? The flow of the argument seems incomplete. Could you explain the sentence further?) is no longer needed to activate the next enzyme that will act on the amino acids and peptides. Trypsinogen is converted into trypsin with the use of another enzyme (enterokinase) in the duodenum.

When fever strikes an individual, the activities of the enzymes are increased. Thus, protein digestion would occur at an abnormal rate.