4B. Which group of organelles is directly responsible for the production of new molecules within a cell?

4B. The cellular process known as the sodium-potassium pump was discovered in the 1950s by Jens Christian Skou, a Danish scientist.  This process is a form of active transport that moves three sodium ions to the outside of a cell for every two potassium ions that it moves into the cell.  Which of these best explains why energy is needed for active transport?

4B. Which of these statements best explains the process of energy conversion that takes place in the mitochondria?

4B. Which cellular process takes place in the ribosomes that are bound to the endoplasmic reticulum?

4B. In the early 1900s a scientist hypothesized a link between DNA and the production of proteins in the cytoplasm. However, the fact that DNA could not be found outside the nucleus led scientists to believe that another substance was also involved in the synthesis of protein in the cytoplasm. In the 1940s scientists performed an experiment that ultimately identified the site of protein synthesis. They also identified the molecule responsible for transporting information from the nucleus to the site of protein synthesis. What was this newly identified molecule?

9A.  Carbohydrates are more easily metabolized than lipids.  However, on a gram-for-gram basis lipids provide cells with more --

9A.  Which of the following biomolecules typically contain both nitrogen and phosphate?

9A. Proteins and polysaccharides are polymers. These polymers are formed by dehydration synthesis. Which statement correctly identifies a difference in the structure of proteins and polysaccharides?

9A. The complex carbohydrates pictured below are made by linking molecules of glucose. 
In all three complex carbohydrates, the subunits of glucose are bonded together differently. Because they have different structures, they most likely-

9A. Four different nucleotides are used as building blocks of DNA. Which of the following can be used to distinguish one nucleotide from another?

6A. A segment of DNA is represented in the illustration. How is information for a specific protein carried on the DNA molecule?

6A. A student builds a model of a DNA strand. Which of the models of a DNA strand shows bases that are complementary to the ones on the student's DNA model?

6B. Organisms can be classified based on homology, which is shared characteristics inherited from a common ancestor. In the past, homologies were based on studies of anatomical structures and patterns of embryonic development. In more recent years, the use of molecular biology techniques has allowed homologies to be compared at the level of nucleotide sequences. Nucleotide sequence comparisons are possible because all organisms share which of the following?

6B. In the early 1980s scientists were able to produce two biomolecules by splicing a human gene into the bacterium E. coli to make recombinant human insulin and growth hormone. Which statement best explains why this experiment was successful?

6A. Each strand of a DNA molecule contains nitrogenous bases that pair with other nitrogenous bases in very specific ways. A diagram of a section of DNA is shown.
Which DNA strand is complementary to the one shown above?

6A. Nitrogenous bases are located on both strands of the DNA double helix. What is the significance of the nitrogenous bases?

6B. The fact that a strain of yeast with a certain defective gene can use the human version of the gene to repair itself is evidence that yeast and humans-

6A. How does DNA in cells determine an organism's complex traits?

6A. Characteristics such as a widow's peak or attached earlobes are determined by the genetic code. Which components of DNA are referred to as the genetic code?

6A. The sequence of nitrogenous bases in DNA varies widely.  The sequence of the bases in DNA is most important for which of the following?

6A. In 1952 Rosalind Franklin took the x-ray photograph shown below, which gave the world its first look at DNA.  By studying this photograph, scientists gained knowledge about the --

6B. Four different types of cell are shown below.  Which characteristic is shared by all four cells?

9A.  The differences between two molecules include the type of sugar that forms a section of the molecules and the identity of one of the four nitrogenous bases that make up another section of the molecules.  These two molecules are -

9A. Four different nucleotides are used as building blocks of DNA. Which of the following can be used to distinguish one nucleotide from another?

9A.  Carbohydrates are more easily metabolized than lipids.  However, on a gram-for-gram basis lipids provide cells with more --

9A.  Which of the following biomolecules typically contain both nitrogen and phosphate?

9A. Proteins and polysaccharides are polymers. These polymers are formed by dehydration synthesis. Which statement correctly identifies a difference in the structure of proteins and polysaccharides?

6A. A segment of DNA is represented in the illustration. How is information for a specific protein carried on the DNA molecule?

6A. A student builds a model of a DNA strand. Which of the models of a DNA strand shows bases that are complementary to the ones on the student's DNA model?

6E. A segment of  DNA produces methionine, histidine, apartate, and glycine when translated.  A substitution mutation occurs and causes the synthesis of the segment as shown.
New DNA strand: 3'-TACAGGGTGCTACCCACT-5'
Which is the new peptide chain when the new DNA segment is translated?

6E. In the 1960s the molecular biologist George Streisinger developed the strand-slippage hypothesis.  Streisinger noticed that mutations occurred in areas of DNA that contained many repeated sequences.  When a strand-slippage error occurs, an insertion mutation can result.  How does the insertion mutation affect the DNA?

6E. The table shows a DNA sequence and three types of mutations that can change the DNA sequence.
Which mutation will cause translation to stop?

6E. The survival of a species depends on its ability to adapt to changes in the environment. A species must be capable of surviving and reproducing despite changes to food sources, climate, or threats from predators. Which statement correctly describes a way that mutations increase the likelihood that a species will survive in a changing environment?

6A. Each strand of a DNA molecule contains nitrogenous bases that pair with other nitrogenous bases in very specific ways. A diagram of a section of DNA is shown.
Which DNA strand is complementary to the one shown above?

6A. A model of a DNA molecule is shown in the picture. The arrow indicates-

6E. A mutation that occurs in the gametes of an organism will most likely be transferred to which of the following?

6E. Sickle-shaped red blood cells result from a mutation in the gene that codes for hemoglobin.  This mutation results in sickle-cell anemia. A partial sequence of bases from a normal hemoglobin gene and a sequence that results in sickle-cell anemia  are shown below.  What type of mutation is depicted in this sequence?

6C. Part of an important cellular process involving a DNA strand is modeled below. What is the purpose of this cellular process?

6D. At birth Himalayan rabbits are usually white over their entire bodies. But when parts of their bodies reach temperatures below 35⁰C, a pigment that causes these parts to turn black is produced. Which of the following is most likely the cause of this phenomenon?

6C. The initial steps in gene expression are modeled below. Double-stranded DNA first unwinds into two strands.
Which process and product are represented in Diagram 2?

6D. Human bone, muscle, and nerve cells contain the same number of chromosomes with the same complement of genes. What enables these cells to perform specialized activities?

6C. Which of the following polypeptides is coded for by the mRNA sequence ^5'AUGGUUAAACGACAAUCC^3'?

6D.  In 1917 the biologist Thomas Hunt Morgan conducted studies in which he kept some caterpillars in the dark and placed some others under red, green, or blue lights.  Exposure to red light produced butterflies with brightly colored wings.  Exposure to  green light resulted in dark-colored wings.  Exposure to blue light or no light in pale-colored wings.  What was the most likely conclusion of Morgan's research?

6B. The fact that a strain of yeast with a certain defective gene can use the human version of the gene to repair itself is evidence that yeast and humans-

6C. A section of a nucleic acid is shown in the diagram. The process represented in the diagram produces a molecule that is complementary to the template strand of DNA. What types of molecule is produced?

5C. As a fertilized egg divides, the cells differentiate because they-

5C. Cell differentiation is critical during embryonic development. The process of cell differentiation results in the production of many types of cells, including germ, somatic, and stem cells. Cell differentiation is most directly regulated by-

6E. A codon chart is shown below. Which of these changes to the DNA triplet 3' GCT 5' will affect the protein produced?

6E. A mutation that occurs in the gametes of an organism will most likely be transferred to which of the following?

5C. Researchers Robert Briggs and Thomas King used ultraviolet radiation to destroy the nuclear DNA of frog eggs.  Nuclei from adult skin cells and from tadpole-gut epithelial cells were cultured and then injected into eggs that had their nuclei destroyed.  The results were tadpoles.  Which conclusion is supported by the data from this investigation?

6E. Early-onset Alzheimer's disease affects people under the age of 65.  Less than five percent of people who are diagnosed with Alzheimers's disease have this type.  Many cases of early-onset Alzheimer's disease are inherited, a type known as familial Alzheimer's disease (FAD).  Which statement is best supported by this information?

5A. The model represents the change in the DNA content of a cell during the cell cycle. Which part of the model represents the S phase?

5A. Scientists can bioengineer skin in a laboratory to treat severe burns and other types of skin injuries. This bioengineered tissue is grown from living cells. The cellular process that enables the cells to grow and develop into tissue is-

5D. Cells typically respond to DNA damage in three ways: by ceasing to grow and divide until the damage is repaired, by permanently ceasing to grow and divide, or by dying. In 2010 a group of scientists reported that a certain kind of immune reaction can cause DNA damage that leads to a fourth response. DNA damage can turn off genes involved in cell-signaling pathways. Turning off these genes can cause less-mature cells to divide too rapidly, often leading to the development of-

5D. Oncogenes are mutated forms of genes. Oncogenes can transform a cell into a tumor cell. Some tumor cells are benign, while others are malignant. How does the presence of an oncogene lead to the formation of a tumor?

5A. Cells pass through a G₂ checkpoint before entering mitosis. Ideally, if DNA damage is detected, the cells do not enter mitosis until the damage is repaired. Why is DNA damage repaired before cells enter mitosis?

5A. The diagram shows cells in different phases of mitosis. A student is trying to find a cell in a particular phase of mitosis. The student is looking for evidence that spindle fibers are separating the chromosomes to ensure that each new nucleus has one copy of each chromosome.
Which cell is in the phase of mitosis that the student is searching for?

5D. The diagram below represents the cell cycle. When cells leave the cell cycle, they exit during G₁ phase and then enter G₀ phase, a resting period. Most normal cells can leave G₀ phase and reenter the cell cycle at G₁ phase before entering S phase. Cancer cells are different because they cannot enter G₀ phase and are likely to do which of the following?

5A. Which of these must occur during S phase of the cell cycle so that two daughter cells can be produced during M phase?

5A. Checkpoints occur between the stages of the cell cycle.  If a cell does not meet certain criteria at the end of a stage, it will not move to the next stage.  Which of these occurs just before the cell enters the G₂ stage of the cell cycle?

5A. Telophase is a stage of a cellular process that begins after the chromosome have moved to opposite poles of the cell.  During which cellular process does telophase occur?

5D. Atherosclerosis is a disease that obstructs blood flow and, therefore, oxygen supply to target organs.  A major component of atherosclerosis is the excessive reproduction of smooth muscle cells of the blood vessels.  Certain drugs may have the potential to reverse or prevent the unregulated reproduction of the diseased blood-vessel cells.  Which of these processes is the most likely target of these drugs?

10B.  Structures represented in the illustration below are found in the lower epidermis of a plant leaf.  The illustration at right shows the response to a certain environmental condition.  The response represented in the illustration would most likely be caused by-

10B.  The internal transport of water and minerals in plants requires that two systems work together.  Which diagram correctly describes how the two systems accomplish this?

10B.  the diagram shows the reproductive system of a plant.  Which of the following best describes the interaction that occurs between a plant's reproductive part during self-fertilization?

5B. Most plants have hair-like cells called trichomes that project from the surface and help the plants in many ways.  In some plants trichomes secrete toxic substances that most likely perform which function?

10B.  Some students are instructed to put a celery stalk in a red dye solution for a lab activity.  First the students carefully cut the bottom of the stalk with a scalpel.  Then they put the stalk in the beaker with the solution and place the beaker on a shelf in the lab room.  The next day they check the stalk and make observations.  The students cut across the celery stalk and use a hand lens to see that the small tube openings along the edge of the celery stalk are also red.  The cross section is shown below.  How do the plant systems work together to make this movement of liquid possible?

10B.  The outermost layer of plant stems in dictoyledons consists of epidermal cells and guard cells that surround openings called stomata.  The epidermal cells are usually covered with a waterproof layer that provides protection from injury and water loss.  The stomata allow gas exchange.  The epidermal cells and stomata have functions similar to those of which two human body systems?

10B.  An animal can wound a tree by scratching away the bark.  The tree can respond to the wound in many ways.  Usually sap quickly covers the wound, and then the tree covers the wound with new growth.  The diagram shows a cross section of a tree with a healed wound.

10B. Leaves are part of a plant's shoot system. The xylem tissue in leaves transports-

10B. Plant hormones serve as chemical messengers between cells and tissues. Auxin is a plant hormone that causes the cells on the shady side of a plant shoot to elongate. The response enabled by auxin is known as - 

10B. Copper is a micronutrient that can be found in soil. Copper is important for reproductive growth in plants and plays an indirect role in chlorophyll production. Which statement correctly describes the interaction that occurs between the root and the shoot systems of plants to allow reproduction to occur?

10B. Cytokinins are a class of plant hormones that help regulate growth by promoting cell division. Cytokinins are produced mainly in meristematic tissue, where most plant growth occurs. Which system carries cytokinins produced in the roots to the rest of the plant?

10B. Several structures work together to allow flowering plants to reproduce. The diagram shows a typical flower.
Which of the following correctly identifies the function of each structure or group of structures in the reproduction of the plant?

10B. Plants called sundews have rounded green leaves with many hair-like structures. The ends of these structures contain enzymes in a sticky liquid that looks like nectar or moisture, as shown in the picture. The hairs do not react to dust or nonliving material but will bend inward when insects get caught in the sticky liquid. Sundews digest trapped insects over a period of a few days.
Based on this information, what functions do the specialized leaves of sundews perform?

9B.  Diatoms are one of the most common types of phytoplankton in marine habitats.  Like plants, diatoms contain chlorophyll and produce glucose from which of the following?

9B.  Most plants take in more carbon dioxide as light increases.  They give off carbon dioxide if light intensity is too low.  The graph shows a plant's carbon dioxide levels at different light intensities.  At point X, the rate of which process is equal to the rate of photosynthesis?

4B. Which of these statements best explains the process of energy conversion that takes place in the mitochondria?

9B. Which of the following correctly describes how a diagram of cellular respiration would differ from a diagram of photosynthesis?

9B. Which statement best describes the relationship between the products of photosynthesis and the reactants in cellular respiration?