The side chain is the variable region of amino acids.  It gives each amino acid the physical and chemical properties that distinguish it from the other 19. All other answers minus ketones make up the generic structure of amino acids.

An individual with two different alleles at a given locus has one allele on one chromosome and the other allele on its homologous partner.  Option B is not possible and option A is highly unlikely. Options C and E have nothing to do with the individual in question and thus can be eliminated

Apoptosis (programmed cell death), hox and homeotic genes (genes that control differentiation), and inductive effects (a tissue affecting the differentiation of another tissue) play a role in cell differentiation. Operons are sets of multiple genes regulated by a single regulatory unit in bacteria.

All of the following are methods of genetic exchange via  lateral gene transfer methods for Eubacteria not Arcaebacteria,

Blood is the only option that forms from the mesoderm germ layer. All other options form from the ectoderm germ layer

Correct Answer: Monera (The kingdom Monera, includes the current domain bacteria which contain cyanobacteria. These organisms photosynthesize and have a peptidoglycan cell wall)

Incorrect Answer: Animalia (The kingdom Animalia have no cell wall and do not photosynthesize)

Incorrect Answer: Plantae (The kingdom Plantae do photosynthesize, but have a cell wall made of cellulose)

Incorrect Answer: Fungi (The kingdom Fungi have a cell wall made of Chitin)

Incorrect Answer Protista (Some protists can photosynthesize, such as algae, however, they do not have a peptidoglycan cell wall)

When a DNA solution is heated enough, the double-stranded DNA unwinds and the hydrogen bonds that hold the two strands together weaken and finally break. This is known as denaturization. Adenine bonded to Thymine contains two hydrogen bonds while Guanine bonded to Cytosine contains three. This means that the DNA strand with the fewest number of Guanines and Cytosines will denature first.

Correct Answer: Increase (Lowering activation energy reduces the energy required to achieve a transition state. The more transition states the reactants are able to form, the more products are produced, and the more rapidly the rate of the reaction)

Incorrect Answer: Decrease (See correct answer)

Incorrect Answer: Stay the Same (See correct answer)

Incorrect Answer: May either increase or decrease (See correct answer)

Incorrect Answer: Cannot be determined (See correct answer)

Correct Answer: The crossing over of homologous chromosomes (The pairing of homologous chromosomes only occurs in meiosis. This process results in genetic variation during sexual reproduction)

Incorrect Answer: One round of replication of the genome before division (Both mitosis and meiosis are preceded by one round of replication of the genome; S phase)

Incorrect Answer: Chromosomes condense (In both prophase of mitosis and meiosis chromosomes condense)

Incorrect Answer: Starts with a diploid cell (Both mitosis and meiosis start with diploid cells. However, meiosis ends with haploid cells while mitosis ends with diploid cells)

Incorrect Answer: Prophase In both prophase of mitosis and meiosis chromosomes condense)

The trait is only passed on to the male descendants of this pedigree chart. This indicates that the trait is encoded by genes on the Y-chromosome.

heterotroph obtains its energy from organic molecules. An autotroph obtains energy from sunlight utilizing pigments such as chlorophyll, and uses CO₂ and water to make organic molecules. Therefore, (A) and (C) can be eliminated. Heterotrophs can obtain their energy from ingesting autotrophs, but they can also consume other heterotrophs. So you can eliminate (D and E), leaving (B) as your answer.

The purines on one strand of DNA form hydrogen bonds with the corresponding pyrimidines on the opposite strand of DNA, and vice versa, to hold the two strands together. Within DNA molecules, this is their most important function and is known as base pairing.

Correct Answer: Sexual Selection (When animals use elaborate rituals and physical displays as a key role in attracting and choose a mate)

Incorrect Answer: Directional Selection (When natural selection removes one extreme and the population average over time move in the other direction)

Incorrect Answer: Divergent Selection (When natural selection removes members of the average, leaving those at either end)

Incorrect Answer: Stabilizing Selection (When both extremes of a trait are selected against, resulting in a population closer to average)

Incorrect Answer: Artificial Selection (When humans intervene in the mating of animals and plants to achieve desired traits)

Correct Answer: The energy of the universe is constant (This is the first law of thermodynamics. The law of conservation of energy states that the total energy of an isolated system is constant)

Incorrect Answer: The energy of the universe tends to decrease (This goes against the first law of thermodynamics)

Incorrect Answer: The disorder of the universe tends to increase (This is the second law of thermodynamics. This law states that the entropy, or disorder of the universe, will always be increasing over time)

Incorrect Answer: The disorder of the universe tends to decrease (This goes against the second law of thermodynamics)

Incorrect Answer: The disorder of the universe is constant (This goes against the second law of thermodynamics)

The resting potential depends on active transport (the Na⁺K⁺-ATPase pump) and the selective permeability of the axon membrane to K⁺ than to Na⁺, which leads to a differential distribution of ions across the axonal membrane.

To make multiple copies of a plasmid (a small circular DNA), it should be inserted into a bacterium. A plasmid would not replicate if it were inserted into a virus or plant, so eliminate (A) and (E). If a plasmid were treated with a restriction enzyme, it would be cut into smaller fragments. This would not give us cloned versions of the plasmid, so (B) is incorrect. If the plasmid were run on a gel (using gel electrophoresis), this would only tell us the size of the plasmid; therefore, (D) is also incorrect.

According to the semiconservative replication model, two original DNA strands (i.e., the two complementary halves of the double helix) separate during replication; each strand then serves as a template for a new DNA strand. This is the way that we know DNA to be replicated. All other answers are either models that have been known to be proven incorrect or are made up

Correct Answer: Cholesterol (All steroids have a basic ring system based on the structure of cholesterol)

Incorrect: Glucose (Not relevant to steroid structure)

Incorrect: Phospholipid Bilayer (Steroid cholesterol is an important component of the phospholipid bilayer)

Incorrect: Carbohydrates (Not relevant to steroid production

Incorrect: Testosterone (Testosterone is an example of a steroid)

Correct Answer: Depict crossing between individuals (The purpose of punnet square is to depict a cross between two individuals of a species to find the probability of each genotype and phenotype after reproduction)

Incorrect Answer: Determine the number of organisms in a certain area (This can be determined using a quadrat)

Determine the density of organisms in a certain area (This can be determined using a quadrat)

Disprove Mendelian genetics (This is incorrect. Punnet squares help to visualise Mendelian genetics)

Depict the process of allopatric speciation (The two topics are unrelated. Allopatric speciation is speciation that occurs due to geographical changes)

Populations can be described as the evolutionary unit because changes in the genetic makeup of populations can be measured over time. Eliminate (A), as genetic changes occur only at the individual level. Only under Hardy-Weinberg equilibrium does the gene pool remain fixed over time in a population. However, this statement does not explain why the population is the evolving unit, so (B) is incorrect. Choice (C) is true but does not address the question. Choice (E) is false and the opposite of our answer.

Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division. This occurs during Anaphase of Meiosis I when homologous chromosomes are being pulled apart.

This statement is false because an individual with two identical alleles is said to be homozygous, not heterozygous, with respect to that gene. Alleles are different forms of the same gene found on corresponding positions of homologous chromosomes, so (A) and (B) are incorrect. More than two alleles can exist for a gene, but a person can have only two alleles for each trait, so (C) and (E) are incorrect.

Correct Answer: Energy is stored (Energy storage occurs when insulin is released by the pancreas, causing the liver to convert glucose into glycogen for storage)

Incorrect Answer: A catabolic reaction has occurred (The conversion of glucose to glycogen is an anabolic process. Anabolic reactions involve the joining of smaller molecules into larger ones.)

Incorrect Answer: Entropy increases (Entropy is a measure of disorder. Since Glycogen is the storage if Glucose Entropy is decreasing)

Incorrect Answer: Glucagon has been released (Glucagon is produced in the pancreas and released when blood glucose levels are low. It causes the liver's Glycogen stores to be converted to Glucose. This is the opposite of what occurs in the question)

Incorrect Answer: ΔG less than 0 (When ΔG is less than 0 this indicates that the reaction is exergonic. The addition of glucose to glycogen is an endergonic process that requires energy.)

Oxaloacetate is an intermediate of the citric acid cycle, where it reacts with acetyl-CoA to form citrate, catalyzed by citrate synthase. Oxaloacetate is regenerated every cycle and is therefore the correct answer. Glucose is involved in glycolysis and is a precursor to the citric acid cycle. All other answers are involved in the citric acid cycle but are either used up or go on to be expelled from the body or used in the electron transport chain. See the photo below for more information:

Correct Answer: Phenotype (Phenotypes are the physical expression of genotype)

Incorrect Answer: Genotype (Genotypes are the DNA sequence of alleles that a person carries)

Incorrect Answer: Heterozygous (When two different alleles are found at a given locus)

Incorrect Answer: Homozygous (When the same alleles are found at a given locus)

Incorrect Answer: Dominant Alele (If an allele is the one expressed in a phenotype regardless of what the second allele carried is)

Legume plants are able to live in nitrogen-poor soil because they obtain nitrogen from nitrogen-fixing bacteria. These plants cannot make their own proteins without nitrogen from nitrogen-fixing bacteria, so eliminate (A), (C), (D),  and (E).

The main challenge for organisms residing in hot arid environments is water loss. Long loops of Henle and storage of water in fatty tissues conserve water resources and large ears help disperse heat. Short loops of Henle would result in more secretion of water kidneys, which would not be advantageous for an organism in a dry environment.

Correct Answer: Rough Endoplasmic Reticulum (This organelle has the function of synthesizing porteins)

Incorrect Answer: Smooth Endoplasmic Reticulum (Function in detoxification and glycogen breakdown in the liver as well as steroid synthesis in the gonads)

Incorrect Answer: Golgi Apparatus (Modifies and sorts proteins)

Incorrect Answer: Peroxisome (Metabolizes lipids and toxins using H2O2)

Incorrect Answer: Lysosome (Contains acid hydrolases which digest various substances)

Pepsin works in the stomach (not the small intestine) to break down proteins to peptides. Complete digestion occurs in the small intestine. Pancreatic lipase breaks down fats into three fatty acids and glycerol, so eliminate (A). Pancreatic amylase breaks down carbohydrates into simple sugars, so (C) can also be eliminated. Bile emulsifies lipids and makes them more accessible to lipase, so get rid of (D). Trypsin converts Chymotrypsinogen to Chymotrypsin for the breakdown of proteins, so eliminate (E).

Correct Answer: Exocytosis (This is the process in which cells transport materials outside of their cell wall)

Incorrect Answer: Endocytosis (The opposite of exocytosis; when cells transport materials inside of their cell wall)

Incorrect Answer: Phagocytosis (This is a type of endocytosis when a large particular matter is endocytosed)

Pinocytosis (This is a type of endocytosis when small particular matter and fluid is endocytosed)

Receptor-mediated endocytosis (This is a type of endocytosis where specific particles are endocytosed)

Reduction is a chemical reaction that involves the gaining of electrons by one of the atoms involved in the reaction between two chemicals. All of the following will result in the gaining of electrons by an atom

Amino acids are organic molecules that contain carbon, hydrogen, oxygen, and nitrogen. Carbohydrates are organic molecules that contain carbon, hydrogen, and oxygen. So eliminate (A), (B), and (D). Carbohydrates do not have Nitrogen. Don't forget to associate amino acids with nitrogen because of the amino group (NH₂).

The egg yolk provides food for the embryo. The amnion protects the embryo, so (A) is incorrect. The chorion is the outermost layer that surrounds the embryo, so eliminate (B). Choice (C) can also be eliminated because the placenta provides nourishment for the embryo in mammals, not in birds. Choice (D) can be eliminated because the allantois stores fetal secretion.

Ribosomes are the site of protein synthesis. Therefore, the correct answer should start with the ribosome. So eliminate (A) and (C). The polypeptide then moves through the rough ER to the Golgi apparatus, where it is modified and packaged into a vesicle. The vesicle then floats to the plasma membrane and is secreted. Choice (D) is your answer.

Correct Answer: Lysosomes (This is the function of the Lysosome)

Incorrect Answer: Peroxisomes (Metabolizes lipid and toxins using H2O2)

Incorrect Answer: Golgi Apparatus (Modification and Sorting of proteins)

Incorrect Answer: Nucleus (Contains and protects DNA and it integral to transcription and assembly of ribosomes)

Incorrect Answer: Phospholipid Bilayer (Makes up the membranes of cells)

Bryophytes are nonvascular seedless plants that lack xylem and phloem. They reproduce in one of two ways. Asexual reproduction occurs when a sporophyte releases spores, and sexual reproduction happens when gametes fuse and form a zygote. Bryophytes have no seeds nor flowers. All the above options are correct.

An organism auxotrophic for arginine will be unable to produce arginine even though it is vital for its growth. This means it must obtain it from somewhere else. Minimal growth mediums only contain only the basic nutrients needed for growth (inorganic salts, a carbon source, and water). Thus an organism auxotrophic for arginine will be unable to grow in a minimal growth medium.

Normal cells can become cancerous when a virus invades the cell and takes over the replicative machinery. A pilus forms between two bacteria and conjugation occurs between to bacteria, so (A) and (E) are wrong. Also, eliminate (C) because the host's genome is not converted to the viral genome. Choice (D) is incorrect because spores are released by fungi, not viruses.