AP Biology Midterm

Which of the following best describes what causes water molecules to exhibit properties such as cohesive and adhesive behavior?

Water molecules are polar, having partially positive and partially negative ends.

Which statement correctly compares the pH of water to that of other substances?

The pH of water is neutral; it is higher than the pH of acids and lower than the pH of bases.

The slight negative charge at one end of one water molecule is attracted to the slight positive charge of another water molecule. What is this attraction called?

A hydrogen bond

Which of the following best explains how water is able to dissolve ionic substances?

The positive and negative charges of the water molecule pull on the negative and positive ends of the ionic molecule to break them apart.

During winter's freezing temperatures, some plants can remove water from their cells to reduce the amount of water that will freeze inside them. Why would plants need to do this?

The expansion of excess water as it turns to ice inside the cells would break the cells apart.

Which of the following best describes how the density of water differs from that of other substances?

The density of water depends on its temperature, unlike other substances.

Carbon atoms are able to

bond with other carbon atoms to form long chains

What is true of carbon atoms?

They can form up to four covalent bonds.

Carbon atoms can form

four single covalent bonds

Why should farmers plant crops that improve the levels of nitrogen in the soil during the winter?

These crops have root nodules that contain bacteria.

Bacteria in the soil convert ammonia into a form that can be reabsorbed by a plant. Which geochemical cycle does this sequence describe?

Nitrogen cycle

Why are bacteria an essential part of the nitrogen cycle?

Bacteria are responsible for fixing nitrogen into usable forms for other organisms.

Carbohydrates are polymers composed of linked monosaccharides. Which of the following is a true statement about polymers?

Proteins, carbohydrates, and nucleic acids are all polymers.

What process links monomers of carbohydrates?

Spontaneous glycosidic links

What are the functional units of a monosaccharide?

Carbonyl and hydroxyl groups

Suppose you have an unknown chemical reaction involving carbohydrates. What is one way to test whether the reaction is dehydration synthesis or hydrolysis reaction?

Determine whether water is formed.

Which of the following correctly lists the functions lipids serve in the body?

Energy storage, cell structure, signaling

One of the properties of cellulose is that it is not soluble in water. What would happen if cellulose was water-soluble?

Cell walls of plants would no longer maintain their rigid form.

Why is the sequence of nucleotides important to the properties of a nucleic acid?

It retains and transmits important biological information.

Why is the sequence of amino acids important to the properties of a protein and determination of the protein produced?

It determines how the biochemical folds into a three-dimensional structure.

Why is the sequence of monosaccharides important to the properties of a carbohydrate?

It stores energy and provides structural support for cells.

How do components of a DNA molecule influence its physical properties?

Deoxyribose and phosphate, linked by phosphodiester bonds, form repeating units to make up the backbone of DNA.

How do RNA's subcomponents affect its properties?

Base pairing occurs within an RNA molecule to give RNA the three-dimensional shape needed for specific functions.

What is the relationship between the sequence of DNA's subcomponents and the properties of DNA?

The nitrogenous base sequence along a segment of DNA determines the amino acid sequence that will be produced.

Which of the following organelles contributes to cell functions by processing proteins?

Golgi Apparatus

Which of the following organelles helps to carry out the light-dependent reactions?

Chloroplast

Which of the following organelles is responsible for detoxifying poisons in a cell?

Smooth endoplasmic reticulum

Which of the following best describes how ribosomes will interact with other organelles within a cell?

They will synthesize proteins that can become components or other organelles.

In the unicellular organism Euglena, the greatest concentration of mitochondria is found surrounding basal bodies. Which of the following best explains this phenomenon?

The basal body is part of the organism's flagella, which use large amounts of ATP.

Through electron microscopy, scientists have observed the fusion of lysosomes with vacuoles. Which of the following statements best explains this observation?

The fusion allows enzymes contained in the lysosomes to digest the contents of the vacuoles.

Which of the following best compares the role of structural features in producing energy and in using energy in a cell?

Electron transport takes place in the thylakoid membrane during photosynthesis and in the inner mitochondrial membrane during cellular respiration.

Which of the following best describes the activities that occur within the chloroplast of a cell?

Chlorophyll contained in the thylakoids captures sunlight to be used in photosynthesis.

Which of the following best compares the structural features involved in obtaining energy and in using energy in a cell?

The thylakoid membrane absorbs solar energy, and glycolysis occurs in the cytosol.

Which of the following accurately describe how a change in the surface-area-to-volume ratio of a cell would affect the rate at which it exchanges materials with its environment through diffusion?

If the ratio increases, it will obtain nutrients and eliminate wastes more quickly.

Which of the following statements correctly describes how a change in a cell's dimensions would most likely affect how it obtains nutrients from its surroundings through diffusion?

If the cell's surface-area-to-volume ratio increases, it will obtain nutrients more quickly.

Which of the following best explains how a change in the size or shape of a cell would most likely impact how it eliminates wastes through diffusion?

If the cell decreases in size, it will be able to eliminate wastes more quickly.

How do large, mature plant cells compensate for inefficient import and export associated with a lower surface-area-to-volume ratio?

Large plant cells have a large water-filled vacuole in the center, decreasing the active cytoplasm volume.

Root hairs are thin outgrowths from certain plant roots that enhance water and nutrient absorption from the soil. Which of the following best describes how root hairs are specialized for this function?

Root hairs have an elongated shape that increases the surface-area-to-volume ratio.

Which of the following explains why some bacteria are flattened in shape?

To increase surface-area-to-volume ratio

Scientific research has shown there are at least four different types of phospholipids in cell membranes. Which of the following best explains these variations?

Different types of the same basic structure of membranes provide the cell with a wider range of functions.

Think about the structure of the cell membrane. Why do lipids spontaneously form the following arrangement when placed in water?

The hydrophobic nature of the lipid chains drives them together, away from the water, while the polar-head groups form favorable electrostatic interactions with water.

Which of the following describes why phospholipids are better suited to forming the cell membrane than regular fats or steroids?

Their phosphate group gives them a hydrophilic end.

Which of the following describes the fluid mosaic model of the cell membrane?

It is selectively permeable, allowing some molecules to enter and leave more easily than others.

According to the fluid mosaic model, the plasma membrane allows some substances to enter the cell more easily than others. Based on the molecular structure of the membrane, which of the following substances would you expect to dissolve in the lipid bilayer and quickly enter the cell?

Hydrocarbons

In the fluid mosaic model, where would you most likely find the transport proteins?

Embedded within the hydrophobic and hydrophilic regions of the bilayer

What is the best explanation of how the fluid mosaic model helps explain the selective permeability of cell membranes?

The phospholipid bilayer provides the cell's protection, while embedded proteins allow passage of some molecules.

The diagram below represents the structure of the plasma membrane. How would the exchange of molecules between an organism and its environment be affected if the membrane were less permeable?

Molecules needed for growth would have more difficulty diffusing across the membrane.

The plasma membrane of a cell consists of a phospholipid bilayer with embedded proteins. The membrane of a mitochondrion also contains embedded proteins; however, the proteins found in these types of membranes differ. Which of the following can you infer about the proteins found in the mitochondrial membrane?

They are specific to mitochondrial function, and they transport materials necessary for cellular respiration.

What is the function of the cell wall in plants, prokaryotes, and fungi?

It provides a structural boundary.

What is the role of the cell wall?

It creates a permeable barrier for some substances to enter or leave the cell.

Which describes the components of the cell wall?

It is composed of complex carbohydrates.

In which of the following examples is homeostasis being maintained through passive transport?

Oxygen dissolves in the lipid bilayer and enters the cell.

The movement of a solute across a plasma membrane without energy and from high to low concentration is best described as

passive diffusion

Which of the following describes pockets in the cell membrane that form vesicles around extracellular material during endocytosis?

Active transport

If you construct a model that places a cell in an aqueous solution, which of the following would result in the cell gaining pressure?

There is a greater salt concentration inside, compared to outside, of the cell.

A cell is placed in an environment that results in the cell having an increased internal pressure. What membrane model could explain this observation?

Initially, the cell's internal salt concentration is greater than the environment; water passes through the membrane into the cell.

If you construct a model that places a cell with an internal salt concentration of 0.02 M in an aqueous solution that has a salt concentration of 0.015 M, what would cause the cell to lower internal pressure?

Active transport of water against the gradient

Which of the following best describes how a channel protein moves materials across the membrane?

They provide a passage for specific molecules to cross the membrane via passive transport.

Through which of the following processes do eukaryotic cells transport large polar molecules through a membrane protein?

Facilitated diffusion

Which of the following explains how carrier proteins function in transporting molecules across the membrane of the cell during facilitated diffusion?

They change shape to move molecules in or out of the cell.

Proton pumps embedded in the cell membrane use ATP to move hydrogen ions across the membrane. Which of the following best describes a function of the proton pump?

It generates a voltage across the membrane as a way to store energy.

The diagram below shows the movement of substances A and B into a cell:

Based on this model, which of the following statements is true?

ATP is required to move Substance B into the cell.

Which of the following is needed to maintain concentration gradients across the plasma membrane?

Molecular energy is required for the maintenance of the concentration gradients.

A cell is placed in a solution that contains a higher solute concentration than the interior of the cell. What effect would this have on the cell?

The cell would shrivel.

What happens to a cell when it is placed in a hypotonic solution that has a decreased solute concentration?

The cell would swell.

A plant cell is placed in a salt solution and the following observation is recorded:

Which answer choice describes the most likely concentration of the solution?

Hypertonic

If a plant cell is placed in a salt solution and the following observation is observed, what is the probable explanation of the net movement of molecules?

Water is moving at equal rates both in and out of the cell.

Analyze the following observation of a plant cell. What is the best explanation of the movement of molecules?

Water is moving out of the cell at a faster rate than into the cell.

You construct a plasma membrane that forms a cell. Inside the cell you place a 1 M salt solution. You place the cell in a flask filled with a 1 M sugar solution. Which of the following would you expect to happen?

Water would enter and exit the cell at the same rate because the solute concentrations inside and outside the cell are the same.

Which of the following describes an example of molecular movement across a membrane through active transport?

Proton pumps move hydrogen ions out of the cell against a concentration gradient.

The sodium potassium pump moves Na and K ions across the plasma membrane. What mechanism of transport is this an example of?

Active transport

Which of the following describes movement of ions and other molecules into a cell through active transport?

Pockets in the cell membrane form vesicles around extracellular material during endocytosis.

The following images depict the calcium ion concentrations of two different cell types and the solution each is placed in at 0 minutes and 5 minutes:

Which cell used active transport to move calcium ions?

Cell A, because the calcium ions were moved up their concentration gradient

The following chart shows the amount of four different minerals found in lake water and in the cytoplasm of algae:

Which mineral(s) did the algae uptake through active transport?

Calcium and sodium

The following image depicts the calcium ion concentration of a cell and the solution it is placed in at 0 minutes and 5 minutes:

Which of the following statements best explains how calcium ions moved across the cell membrane?

Calcium ions moved into the cell by active transport.

Which of the following best describes how the rough endoplasmic reticulum and the Golgi apparatus interact in a cell?

Proteins are formed by ribosomes on the rough endoplasmic reticulum and are then transported by vesicles to the Golgi apparatus for processing.

Which of the following best describes the relationship between the nucleolus and ribosomes within a cell?

Proteins and rRNA assemble into ribosome subunits inside the nucleolus, after which the subunits leave the nucleus and combine to form ribosomes.

Which of the following best describes the relationship between lysosomes and the Golgi apparatus within a cell?

Some lysosomes are formed by budding from one face of the Golgi apparatus.

Which of the following best describes the activities that occur within the chloroplast of a cell?

Chlorophyll contained in the thylakoids captures sunlight to be used in photosynthesis.

Which of the following best describes how vacuoles and lysosomes interact in a plant cell?

Lysosomes contain hydrolytic enzymes that break down materials stored in vacuoles.

Which of the following accurately describes a subcellular organelle that functions in providing energy for the cell?

Cristae divide mitochondria into the intermembrane space and the mitochondrial matrix, which contains mitochondrial DNA, enzymes, and ribosomes.

The diagram below depicts a prokaryotic cell and a eukaryotic cell during cellular division. In which of the following ways does this differ in prokaryotic and eukaryotic cells?

Eukaryotic cells can undergo meiosis, and prokaryotic cells cannot.

The diagram below shows cross-sections of a prokaryotic cell and a eukaryotic cell. Which of the following is a key difference between prokaryotic and eukaryotic cells?

Eukaryotic cells have membrane-bound organelles, and prokaryotic cells do not.

Magnified images of a prokaryotic cell and a eukaryotic cell are represented in the diagram below. Which of the following describes a difference between prokaryotic and eukaryotic cells?

Eukaryotic cells are typically much larger than prokaryotic cells.

Which of the following best describes the main idea of the endosymbiotic theory?

Modern-day mitochondria evolved from simple prokaryotic cells taken up by larger prokaryotes.

Which of the following does not provide evidence for endosymbiotic theory?

Mitochondria and chloroplasts reproduce without the use of binary fission.

Which of the following is not supported by the endosymbiotic theory?

Ancient prokaryotes ingested the smaller prokaryotes in a parasitic relationship.

The binding of a compound to an enzyme is observed to slow down or stop the rate of the reaction catalyzed by the enzyme. Increasing the substrate concentration reduces the inhibitory effects of this compound. Which of the following could account for this observation?

The compound

is a competitive inhibitor

Which of the following can best be attributed to the specific function of enzymes?

An increase in reaction speed and the shape of the active site

A series of enzymes catalyze the reaction X → Y → Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme. With respect to the enzyme that converts X to Y, substance A functions as

an allosteric inhibitor

Enzymes are biological catalysts. Ammonia, NH3, is used in numerous industrial processes, including the production of pharmaceuticals such as sulfonamide and antimalarials and vitamins such as the B vitamins. The equilibrium equation for the synthesis of ammonia (sometimes known as the Haber process) is

N2(g) + 3H2(g) ↔ 2NH3(g)

What will happen to the rates of the forward and reverse reactions when a catalyst is added?

Both forward and reverse rates increase.

Which of the following best describes what happens to an enzyme after it catalyzes a chemical reaction?

It is unchanged and can be used again for the same chemical reaction.

Under which of the following conditions would a chemical reaction most likely proceed at the fastest rate?

Adding an enzyme to decrease the activation energy of the reaction

Which curves on the graphs in the figure may represent the temperature and pH profiles of an enzyme taken from an organism that lives in an acidic environment with high temperatures?

Curves 3 and 4

Which curves on the graphs in the figure may represent the temperature and pH profiles of an enzyme taken from a bacterium that lives in a mildly alkaline hot spring at temperatures of 70°C or higher?

Curves 3 and 5

Which temperature and pH profile curves on the graphs in the figure were most likely generated from analysis of an enzyme from the human stomach, where conditions are strongly acidic?

Curves 1 and 4

The activity of many cellular enzymes is regulated by activators and inhibitors. Enzyme activity is also regulated in eukaryotic cells by which of the following mechanisms?

Compartmentalization and restricting enzymes to specific organelles or membranes

The binding of a compound to an enzyme is observed to slow down or stop the rate of the reaction catalyzed by the enzyme. Increasing the substrate concentration reduces the inhibitory effects of this compound. Which of the following could account for this observation?

The compound is a competitive inhibitor.

The binding of an allosteric inhibitor to an enzyme causes the rate of product formation by the enzyme to decrease. Which best explains why this decrease occurs?

The allosteric inhibitor causes a structural change in the enzyme that prevents the substrate from binding at the active site.

Choose the correct statement.

Loss of energy flow results in death.