Biochemistry Flashcards
Water molecules are polar covalent molecules. There is a partial negative charge near the oxygen atom and partial positive charges near the hydrogen atoms due to the uneven distribution of electrons between the atoms, which results in the formation of hydrogen bonds between water molecules. The polarity of water molecules contributes to many properties of water that are important for biological processes.
Which of the following models best demonstrates the arrangement of hydrogen bonds between adjacent water molecules?
(image) H bonds with O
Figure 1 shows a short segment of a double-stranded nucleic acid molecule. Figure 1. A short segment of a double-stranded nucleic acid molecule (image)
Which of the following statements is correct about the molecule shown in Figure 1 ?
It is DNA because of the nucleotides present.
The figure shows the results of an experiment to investigate the effects of an enriched CO2 environment on plant growth. Identical plants were separated into different groups and grown either in a standard CO2 environment (400 ppm CO2) or in an enriched CO2 environment (700 ppm CO2). Of the plants in each environment, half were grown under ideal conditions and half were grown under stressed conditions. (image)
Based on the figure, which statement best describes the observed relationship between atmospheric CO2 enrichment and plant growth under ideal and stressed conditions?
The increase in atmospheric CO2 resulted in a greater increase in plant growth under stressed conditions than under ideal conditions.
In vascular plants, water flows from root to leaf via specialized cells called xylem. Xylem cells are hollow cells stacked together like a straw. A student explains that evaporation of water from the leaf pulls water up from the roots through the xylem, as shown in Figure 1. (image)
Figure 1. Model of water movement through the xylem, with magnified models of water movement in the stem and leaf.
Which statement describes how water is pulled up through the xylem to the leaves of the plant?
As water exits the leaf, hydrogen bonding between water molecules pulls more water up from below.
Which of the following describes a key difference among the 20 amino acids that are used to make proteins?
Some amino acids are hydrophobic
Phosphorous (P) is an important nutrient for plant growth. Figure 1 shows Arabidopsis thaliana plants grown under phosphorus‐sufficient (left) and phosphorus‐starved (right) conditions for six weeks. (image of thriving plant…phosphorus sufficient, image of weak plant…phosphorus starved)
Which of the following is the most likely reason for the difference in leaf growth?
The phosphorus starved plant was unable to synthesize both the required nucleic acids and lipids, limiting growth.
Which of the following best describes a structural similarity between the two molecules shown in Figure 1 that is relevant to their function? (model one is RNA and model two is DNA)
Both molecules contain nucleotides that form base pairs with other nucleotides, which allows each molecule to act as a template in the synthesis of other nucleic acid molecules.
A polypeptide is polymer of amino acids held together by peptide bonds. The process of dehydration synthesis creates these peptide bonds, as shown in Figure 1.
Figure 1. Amino acids are linked through the formation of peptide bonds. (image)
As shown in Figure 1, an amino acid must have which of the following properties in order to be incorporated into a polypeptide?
The ability to form a covalent bond with both its NH2 group and its COOH group.
Different polysaccharides are used by plants for energy storage and structural support. The molecular structures for two common polysaccharides are shown in Figure 1. Starch is used by plants for energy storage, and cellulose provides structural support for cell walls. The monomer used to construct both molecules is glucose.
Figure 1. (comparison of segments of starch and cellulose)
A study determined the effect of two different digestive enzymes, A and B, on these two polysaccharides. Table 1 presents the data from the study. (table)
Mammals do not produce digestive enzyme B. However, sheep and cattle are two types of mammals that contain microorganisms in their digestive tract that produce enzyme B.
Based on Figure 1, which of the following best compares the atomic structures of starch and cellulose?
Starch and cellulose are composed of repeating glucose monomers; however, in cellulose every other glucose monomer is rotated 180 degrees.
Different polysaccharides are used by plants for energy storage and structural support. The molecular structures for two common polysaccharides are shown in Figure 1. Starch is used by plants for energy storage, and cellulose provides structural support for cell walls. The monomer used to construct both molecules is glucose.
A study determined the effect of two different digestive enzymes, A and B, on these two polysaccharides. Table 1 presents the data from the study. (table)
Mammals do not produce digestive enzyme B. However, sheep and cattle are two types of mammals that contain microorganisms in their digestive tract that produce enzyme B.
Which of the following best describes the process that adds a monosaccharide to an existing polysaccharide?
A specific enzyme removes the hydrogen ( H ) from the monosaccharide and the hydroxide ( OH ) from the polysaccharide, creating a bond between the two and creating a water ( H2O ) molecule.
Different polysaccharides are used by plants for energy storage and structural support. The molecular structures for two common polysaccharides are shown in Figure 1. Starch is used by plants for energy storage, and cellulose provides structural support for cell walls. The monomer used to construct both molecules is glucose.
A study determined the effect of two different digestive enzymes, A and B, on these two polysaccharides. Table 1 presents the data from the study.
Mammals do not produce digestive enzyme B. However, sheep and cattle are two types of mammals that contain microorganisms in their digestive tract that produce enzyme B.
Which of the following statements best describes the different functions of starch and cellulose in plants?
The differences in the assembly and organization of the monomers of these two polymers result in different chemical properties.
Different polysaccharides are used by plants for energy storage and structural support. The molecular structures for two common polysaccharides are shown in Figure 1. Starch is used by plants for energy storage, and cellulose provides structural support for cell walls. The monomer used to construct both molecules is glucose.
A study determined the effect of two different digestive enzymes, A and B, on these two polysaccharides. Table 1 presents the data from the study. Mammals do not produce digestive enzyme B. However, sheep and cattle are two types of mammals that contain microorganisms in their digestive tract that produce enzyme B.
Which of the following would most likely occur if cattle lost the ability to maintain a colony of microorganisms in their digestive tract?
Cattle would no longer be able to use cellulose as a primary source of glucose.
Which of the following is common feature of the illustrated reactions showing the linking of monomers to form macromolecules?
(dehydration synthesis image)
Monomers are joined by a covalent bond, and a water molecule is produced.
A student wants to modify model 1 so that it represents an RNA double helix instead of a DNA double helix. Of the following possible changes, which would be most effective in making model 1 look more like RNA than DNA? (image)
Changing the deoxyriboses to riboses by adding −OH groups
Which feature of model 1 best illustrates how biological information is coded in a DNA molecule?
(image)
The linear sequence of the base pairs
