AP Bio Midterm

Which of the following is not a polysaccharide important to living things?

Cholesterol

The carbohydrates glucose, galactose, and fructose have the same chemical formula (C6H12O6)(C6H12O6) but different structural formulas, as represented in the figure.

Which of the following statements about glucose, galactose, and fructose is most likely true?

The carbohydrates have different properties because they have different arrangements of carbon, hydrogen, and oxygen atoms.

Which of the following is responsible for the cohesive property of water?

Hydrogen bonds between the oxygen atom of one water molecule and a hydrogen atom of another water molecule

Water and ammonia interact to form hydrogen bonds, as represented in the figure.

Which statement best helps explain the formation of the hydrogen bond represented in the figure?

The nitrogen has a partial negative charge, and the hydrogen attached to the oxygen has a partial positive charge.

The diagram shows how water can adhere to the xylem in the stems of plants, which contributes to water movement in the plant. Which of the following best explains how water is able to move upward from the roots of a plant, through its xylem in the stem, and out to the leaves?

Water and the xylem are both polar. Water molecules have the ability to form hydrogen bonds with each other and with the walls of the xylem.

Humans produce sweat as a cooling mechanism to maintain a stable internal temperature. Which of the following best explains how the properties of water contribute to this physiological process?

The high heat of vaporization of water allows the body to remove excess heat through a phase change of water from liquid to gas.

Figure 1 is a diagram of water molecules at the air-water interface at the surface of a pond.

Figure 1. Alignment of water molecules at air-water interface

Based on Figure 1, which of the following best describes how the properties of water at an air-water interface enable an insect to walk on the water's surface?

Hydrogen bonds between molecules at the surface of the water provide surface tension, which allows the water surface to deform but not break under the insect.

Which of the following is most directly responsible for water’s unique properties?

It forms hydrogen bonds.

Scientists examined the folded structure of a purified protein resuspended in water and found that amino acids with nonpolar R groups were primarily buried in the middle of the protein, whereas amino acids with polar R groups were primarily on the surface of the protein. Which of the following best explains the location of the amino acids in the folded protein?

Nonpolar R groups that cannot form hydrogen bonds with water are pushed into the middle of the protein.

If 30% of the nucleotides in a single-stranded RNARNA molecule are adenine, then what percent are expected to be thymine?

0% \n

Amylase is an enzyme that converts carbohydrate polymers into monomers. Glycogen synthase is one of the enzymes involved in converting carbohydrate monomers into polymers.

Which of the following best explains the reactions of these enzymes?

Amylase aids in the addition of a water molecule to break covalent bonds whereas glycogen synthase aids in the removal of a water molecule to form covalent bonds.

Which of the following correctly illustrates a dipeptide and an amino acid in the optimal position to form a tripeptide?

DNADNA and RNARNA are nucleic acids that can store biological information based on the sequence of their nucleotide monomers. Figure 1 shows a short segment of each of the two types of nucleic acids.

Which of the following best describes a structural difference between DNA and RNA?

The backbone of DNA contains deoxyribose, whereas the backbone of RNA contains ribose.

The molecular structures of linoleic acid and palmitic acid, two naturally occurring substances, are shown in the figure.

Based on the molecular structures shown in the figure, which molecule is likely to be solid at room temperature?

Palmitic acid, because the absence of carbon-carbon double bonds allows the molecules to pack closely together.

This group of questions consists of five lettered headings followed by a list of phrases or sentences. For each phrase or sentence, select the one heading to which it is most closely related. Each heading may be used once, more than once, or not at all.

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This group of questions refers to the following groups of biological compounds.

\n (A) Proteins \n (B) Carbohydrates \n (C) Nucleic acids \n (D) Lipids \n (E) Steroids

Used to carry the genetic code

Nucleic acids

This group of questions consists of five lettered headings followed by a list of phrases or sentences. For each phrase or sentence, select the one heading to which it is most closely related. Each heading may be used once, more than once, or not at all.

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This group of questions refers to the following groups of biological compounds.

\n (A) Proteins \n (B) Carbohydrates \n (C) Nucleic acids \n (D) Lipids \n (E) Steroids

Synthesized at the ribosome

Proteins

Which of the following best describes the hydrolysis of carbohydrates?

The addition of a water molecule breaks a covalent bond between sugar monomers

A small protein is composed of 110 amino acids linked together in a chain. As shown in Figure 1, the first and last five amino acids in the chain are hydrophobic (have nonpolar and uncharged RR-groups), whereas the remaining 100 amino acids are hydrophilic (have charged or polar RR-groups). The nature of the RR-group determines if the amino acid is hydrophobic or hydrophilic.

A mutation results in the production of a version of the small protein that is only 105 amino acids long, as shown in Figure 2. Five of the hydrophobic amino acids are missing from one end of the chain.

Which of the following best depicts the tertiary structures of the two proteins in water? The diagrams in the options are not drawn to the same scale as those in Figure 1 and Figure 2.

Which of the following best explains why a cell’s plasma membrane is composed of two layers of phospholipids rather than just a single layer?

Having two oppositely oriented layers of phospholipids allows only the hydrophilic heads to interact with water inside and outside of the cell.

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Figure 1. An amino acid

The amino acid in Figure 1 is found in a region of a polypeptide that folds away from water. Which part of the amino acid most likely contributes to the hydrophobic behavior of this region of the polypeptide?

Methyl (CH3CH3) group

Figure 1 represents a common process that occurs in organisms.

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Which of the following is an accurate description of the process shown in Figure 1 ?

The formation of a covalent peptide bond in a dehydration synthesis reaction

Which of the following best describes the formation of the bond shown in Figure 1 ?

A covalent bond is formed between a carbon atom and a nitrogen atom along with the formation of H2O

Which of the following best describes the structures of carbohydrates?

They occur as monomers, chains of monomers, and branched structures.

The synthesis of protein or carbohydrate polymers always produces which of the following as a byproduct?

Water

Polypeptides are continuously being formed and degraded. One of these processes is shown.

Figure 1. Polypeptide reaction

Which statement is the most accurate description of the reaction shown in Figure 1?

It represents a polypeptide chain that is broken down through a hydrolysis reaction.

Which of the following best describes how amino acids affect the tertiary structure of a protein?

The interactions of the different RR-groups with other RR-groups and with their environment determine the tertiary structure of the protein.

Ultraviolet (UV) radiation can damage DNA by breaking weak bonds. Which of the following best explains how this occurs?

UV radiation disrupts the double helix structure by breaking the hydrogen bonds between the nitrogenous base pairs.

Which two cellular organelles in eukaryotes have both electron transport systems and chemiosmotic mechanisms?

Chloroplasts and mitochondria

The following questions refer to the following diagram. For each phrase or sentence, select the labeled part to which it is most closely related. Each option may be used once, more than once, or not at all for each group.

Site of glucose synthesis

B

Site of conversion of chemical energy of glucose to ATP

A

Site of modification and packaging of proteins and lipids prior to export from the cell

C

Which of the following is evidence that eukaryotes and prokaryotes share a common ancestor?

All eukaryotes and prokaryotes contain ribosomes.

Organelles such as mitochondria and the endoplasmic reticulum have membranes that compartmentalize reactions and other metabolic processes. To function properly, the organelles must move substances across their membranes.

Which of the following statements describes a feature shared by mitochondria and the endoplasmic reticulum that increases the efficiency of their basic functions?

They have highly folded membranes.

All eukaryotic cells contain at least one Golgi complex, typically located in the cytoplasm and near the endoplasmic reticulum.

Which of the following best describes a process that occurs within the Golgi complex?

Enzymatic modification of newly synthesized integral membrane proteins

Which of the following organelles modifies and packages for secretion the materials produced by the ribosomes?

The Golgi apparatus

Individuals with an inherited autosomal recessive disorder called primary ciliary dyskinesia (PCD) often have severe respiratory problems due to defective cilia. Males with PCD are often sterile because they produce sperm with defective flagella. Which of the following most likely explains the effect of the recessive allele?

The cells do not produce functional motor proteins in flagella and cilia.

Which of the following statements is true about the Krebs (citric acid) cycle and the Calvin (light-independent) cycle?

They both are carried out by enzymes located within an organelle matrix.

Contains hydrolytic enzymes associated with the intracellular digestion of macromolecules

Lysosome

The organelle that is a major producer of ATP and is found in both heterotrophs and autotrophs is the

mitochondrion

In a mesophyll cell of a leaf, the synthesis of ATP occurs in which of the following?

I. Ribosomes \n II. Mitochondria \n III. Chloroplasts

II and III only

Muscle cells have high ATPATP demands. Which of the following is a scientific claim about how the structure of the mitochondria in muscle cells should be different than it is in other cells because of the high energy demands of mitochondria?

The inner membrane of the mitochondria in muscle cells should have more folds to increase the surface area, allowing more ATPATP to be synthesized.

The function of which of the following organelles directly requires oxygen?

Mitochondrion

Prokaryotic and eukaryotic cells generally have which of the following features in common?

Ribosomes

The figure below illustrates a eukaryotic cell. Which of the following best describes how the three structures indicated by the arrows work together?

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To synthesize and isolate proteins for secretion or for use in the cell

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The figure above represents a rough endoplasmic reticulum. Which of the following best describes the role of the structure labeled *Y*?

Structure *Y* is the location where proteins are synthesized.

Researchers have proposed a model of the process by which a newly synthesized protein is transported to the plasma membrane and secreted into the extracellular space. The model is represented in Figure 1.

Figure 1. A model of the intracellular transport of a newly synthesized secreted protein

Based on the model, the newly synthesized protein is transported directly from the endoplasmic reticulum to which of the following?

The Golgi complex

The manner in which several different ions and molecules move through a cell membrane is shown in the diagram above. For each ion or molecule, the relative concentration on each side of the membrane is indicated. Which of the following accurately describes one of the movements taking place?

\n Na+ transport out of the cell requires ATP hydrolysis.

The illustration shows the active transport of hydrogen ions through a membrane protein.

Which of the following best predicts the effect of not having ATPATP available to supply energy to this process?

H+ ions will stop moving through the protein.

Which statement best describes the effect on water transport across the cell membrane if the aquaporin in the figure ceases to function?

Water molecules will still be able to move across the cell membrane but at a slower rate.

If ATP breakdown (hydrolysis) is inhibited, which of the following types of movement across cell membranes is also inhibited?

Passage of a solute against its concentration gradient

Which of the following components of the cell membrane is responsible for active transport?

Protein

Which of the following describes the most likely location of cholesterol in an animal cell?

Embedded in the plasma membrane

When a substance moves across the plasma membrane along a concentration gradient at a rate faster than would be expected by simple diffusion alone but without the expenditure of metabolic energy, the process is best described as

\n facilitated diffusion

Which of the following scientific questions is most relevant to the model represented in the figure above?

Which molecular substance is actively transported across the plasma membrane?

Carbon dioxide most likely enters a cell through which of the following processes?

Simple diffusion through the membrane

Which of the following best explains how molecules such as O2 and CO2 can move across the membrane of a cell?

The majority of the cell membrane is nonpolar, which allows small, nonpolar molecules to freely cross.

Which of the following statements is true regarding the movement of substances across cell membranes?

Ions are unable to move through the phospholipid bilayer because the nonpolar tail regions of the phospholipids are hydrophobic.

A team of biologists develop a new drug, and one team member hypothesizes that the drug is incapable of freely passing across the plasma membrane and requires the help of membrane proteins to enter cells. Alternatively, another biologist on the team hypothesizes that the drug can diffuse passively across the plasma membrane like O2O2 and CO2CO2 can.

Which of the following, if true about the drug, best supports the alternative hypothesis that the new drug will exhibit simple diffusion across plasma membranes?

The drug is a small nonpolar molecule.

The drug is a small nonpolar molecule.

Passive transport is the net movement of substances down a concentration gradient that does not require metabolic energy. Active transport is the movement of substances up a concentration gradient that requires energy.

A pathogenic bacterium has been engulfed by a phagocytic cell as part of the nonspecific (innate) immune response. Which of the following illustrations best represents the response?

Which of the following best describes the numbered areas?

Areas 1 and 3 are polar, since the membrane molecules are aligned with water molecules

The model below shows the structure of a portion of a plasma membrane in an animal cell.

Which statement best explains the orientation of the phospholipid molecules in this model?

The hydrophilic phosphate groups of the phospholipid molecules are attracted to the aqueous internal and external environments.

In an experiment, cells were isolated from an aquatic plant and suspended in pond water, a sucrose sugar solution, or distilled water. All of the cells were then viewed under a microscope. Compared with the cell in the pond water, the cell in the sugar solution appeared shriveled, and the cell in the distilled water appeared inflated. The results of the experiment are represented in Figure 1.

Which of the following statements best explains the observations represented in Figure 1 ?

There was a net movement of water out of the cell suspended in the sugar solution and a net movement of water into the cell suspended in the distilled water.

Simple diffusion and facilitated diffusion are related in that both

depend on a concentration gradient

For the following questions: Graphs I-IV depict the effect of pH on the activity of four different hydrolytic enzymes.

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Enzymes with their highest activity at an alkaline (basic) pH are represented by which of the following graphs?

II only

For the following questions: Graphs I-IV depict the effect of pH on the activity of four different hydrolytic enzymes.

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Graphs representing enzymes sensitive to changes in pH include which of the following?

I, II, and III only

The diagram below shows energy changes in a specific chemical reaction with and without the addition of an enzyme to the reaction.

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Which of the following questions can best be answered by the diagram?

Does the addition of an enzyme reduce the activation energy required for a reaction?

Figure 1. Change in energy over the course of four chemical reactions

Based on the data in Figure 1, which of the following most likely represents the change in energy that occurs when ATPATP hydrolysis is coupled with the phosphorylation of a substrate?

Line 1 represents ATP hydrolysis, and line 4 represents phosphorylation of a substrate.

Which of the following statements best helps explain the reaction specificity of an enzyme?

The shape and charge of the substrates are compatible with the active site of the enzyme.

The enzyme hexokinase catalyzes the conversion of glucose to glucose-6-phosphate, which is an important step in glycolysis. The reaction involves the transfer of a phosphate group from ATPATP to glucose.

Either a glucose molecule or a water molecule can fit in the active site of hexokinase. The presence of a water molecule in hexokinase’s active site would result in the hydrolysis of ATPATP to ADPADP instead of the conversion of glucose to glucose-6-phosphate.

Which of the following statements best helps explain the reaction specificity of hexokinase?

Glucose has the right shape and charge to cause hexokinase to undergo a structural change needed for catalysis, whereas water does not.

Pyruvate kinase, a key enzyme in the glycolysis pathway, is inhibited by the amino acid alanine. The ability of alanine to inhibit the enzyme is not affected by increasing the concentration of substrate.

Which of the following best explains the mechanism by which alanine inhibits pyruvate kinase activity?

Alanine binds to an allosteric site of the enzyme, changing the shape of the enzyme’s active site.

Trypsin and pepsin are enzymes that function in different areas of the digestive tract. One functions in the stomach, where the pH is between 1.51.5 and 3.53.5, while the other functions in the small intestines, where the pH is between 66 and 88.

Pepsin works in the stomach because the optimal pH for pepsin is acidic.

A researcher claims that different enzymes exhibit maximal function over different pHpH ranges. To test the claim, the researcher carries out an experiment that includes three different enzymes: pepsin, salivary amylase, and arginase. The results of the experiment are represented in Figure 1.

Figure 1. The effect of pHpH on three different enzymes

Which of the following actions will provide the most appropriate negative control for the experiment?

Repeating the experiment with denatured enzymes

The enzyme peroxidase is found in many organisms. It catalyzes the breakdown of hydrogen peroxide into water and oxygen gas. The rate of peroxidase activity at different pH values was assessed by students in the lab. The students’ results are shown in graph 1.

Graph 1. Effect of pH on peroxidase activity

If the experiment is repeated at pH 11, the observed activity level of the enzyme will most likely be

lower than the level at pH 9

Phosphofructokinase (PFK) is an enzyme that catalyzes the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate during glycolysis, as represented in Figure 1.

PFK can be allosterically inhibited by ATP at high concentrations. Which of the following is the benefit of regulating glycolysis by the concentration of ATP?

Glycolysis proceeds when the intracellular concentration of ATP is low, which provides ATP to drive cellular reactions.

A researcher claims that increased atmospheric carbon dioxide levels cause increased growth rates in plants.

Which of the following statements best supports the researcher’s claim?

Atmospheric carbon dioxide is the raw material for photosynthesis, which plants rely on for producing sugars and other organic compounds.

The energy required to run the Calvin cycle reactions of photosynthesis comes from which two substances produced during the light-dependent reactions?

ATP and NADPH

The carbon 'that makes up organic molecules in plants is derived __directly__ from

carbon fixed in photosynthesis

carbon fixed in photosynthesis

No ATP is synthesized when channel proteins that allow the free passage of protons are inserted into the thylakoid membrane.

Which of the following is an important difference between light-dependent and light-independent reactions of photosynthesis?

The light-dependent reactions produce ATP and NADPH; the light-independent reactions use energy stored in ATP and NADPH.

Carbohydrate-synthesizing reactions of photosynthesis directly require

products of the light reactions

It is estimated that oxygen production first evolved in photosynthetic prokaryotes approximately 2.7 billion years ago. The first photosynthetic prokaryotes are presumed to be similar to today’s cyanobacteria.

Which of the following best supports the claim that photosynthetic prokaryotes were responsible for the oxygen in Earth’s atmosphere?

The light reactions of photosynthesis split water into hydrogen ions and oxygen.

A scientist claims that *Elysia chlorotica,* a species of sea slug, is capable of photosynthesis.

Which of the following observations provides the best evidence to support the claim?

*Elysia chlorotica* grows when exposed to light in the absence of other food sources.

* This group of questions consists of five lettered headings followed by a list of phrases or sentences. For each phrase or sentence, select the one heading to which it is most closely related. Each heading may be used once, more than once, or not at all.

(A) Glysolysis \n (B) Krebs cycle (citric acid cycle) \n (C) Calvin cycle (light-independent reactions of photosynthesis) \n (D) Light-dependent reactions of photosynthesis \n (E) Chemiosmosis

Process in which O2 is released as a by-product of oxidation-reduction reactions

D

* This group of questions consists of five lettered headings followed by a list of phrases or sentences. For each phrase or sentence, select the one heading to which it is most closely related. Each heading may be used once, more than once, or not at all.

(A) Glycolysis \n (B) Krebs cycle (citric acid cycle) \n (C) Calvin cycle (light-independent reactions of photosynthesis) \n (D) Light-dependent reactions of photosynthesis \n (E) Chemiosmosis

Process in which carbon from CO2 is incorporated into organic molecules

C

Which of the following questions is most relevant to understanding the Calvin cycle?

How is ATP used in the formation of 3-carbon carbohydrates?

A researcher is investigating the effects of a chemical that makes thylakoid membranes permeable to hydrogen ions (H+H+). Which of the following is the most likely direct effect of adding the chemical to plant cells?

The chloroplasts will generate less ATP.

The O2 released during photosynthesis comes from

H2O

Which of the following best describes the role of water in photosynthesis?

Water molecules donate electrons to the electron transport chain.

This group of questions consists of five lettered headings followed by a list of phrases or sentences. For each phrase or sentence, select the one heading to which it is most closely related. Each heading may be used once, more than once, or not at all.

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This group of questions refers to molecules of the following substances.

\n (A) Cytochrome \n (B) FADH2 \n (C) NAD+ \n (D) NADP+ \n (E) Oxygen (O2)

An intermediate electron acceptor for oxidations that occur in both glycolysis and in Krebs cycle reactions

NAD+

ATP serves as a common energy source for organisms because

\n its energy can be easily transferred to do cellular work

During respiration, most ATP is formed as a direct result of the net movement of

protons down a concentration gradient

Which of the following statements about mitochondrial chemiosmosis is NOT true?

Heat energy is required to establish the electron transport chain.

Heat energy is required to establish the electron transport chain.

electrons flowing along the electron transport \n chain

Within the cell, many chemical reactions that, by themselves, require energy input (have a positive free-energy change) can occur because the reactions

may be coupled to the hydrolysis of ATP

Figure 1. Diagram of the electron transport chain and ATPATP synthase in the membrane of mitochondria

On average, more ATPATP can be produced from an NADH molecule than can be produced from a molecule of FADH2FADH2. Based on Figure 1, which of the following best explains the difference in ATPATP production between these two molecules?

The electrons of FADH2 are transferred through three complexes of the electron transport chain whereas those of NADH are transferred through all four complexes.

Newborn babies and hibernating animals contain a large amount of brown adipose (fat) tissue (BAT). Certain proteins in the BAT cells increase the permeability of the inner mitochondrial membrane to protons, disrupting the proton gradient.

Which of the following best predicts the effect of disrupting the proton gradient in BATBAT?

Electron transport and oxidative phosphorylation will be decoupled, generating more heat but less ATP.

Certain chemicals, including sodium fluoride (NaF), are capable of inhibiting specific steps of glycolysis. Figure 1 shows the steps of the glycolysis pathway, indicating where various macromolecules enter the pathway as well as the specific reaction inhibited by NaF.

based on Figure 1, the net number of ATPATP molecules produced during glycolysis from the metabolism of a single glucose molecule is closest to which of the following?

2

Which of the following questions will best direct an investigation of the mechanism of ATP synthase?

Is the phosphorylation of ADP by ATP synthase dependent on the formation of a proton gradient?

When hydrogen ions are pumped out of the mitochondrial matrix, across the inner mitochondrial membrane, and into the space between the inner and outer membranes, the result is

the creation of a proton gradient