AP Bio Unit 2 Test
Prokaryotes vs. Eukaryotes
- Prokaryotes have no nucleus or membrane bound organelles - Eukaryotes have a nucleus and membrane bound organelles - Both can reproduce and respond to the environment
Cell structure advances
- the development of a more complex cytoskeleton - the formation of ribosome-studded internal membranes, some of which surrounded the DNA - the enclosure of the cell's DNA in a nucleus - the formation of a flagellum from microtubules of the cytoskeleton - the evolution of digestive vacuoles
cholesterol
A lipid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids.
Aquaporin
A membrane protein, specifically a transport protein, that facilitates the passage of water through channel proteins.
Channel Protein
A membrane protein, specifically a transport protein, that has a hydrophilic channel that certain molecules or atomic ions use as a tunnel.
Fluid mosaic model
A molecular model for the structure of biological membranes consisting of a fluid phospholipid bilayer in which suspended proteins are free to move in the plane of the bilayer.
Glycoprotein
A protein with one or more carbohydrates covalently attached to it.
isotonic solution
A solution in which the concentration of solutes is essentially equal to that of the cell which resides in the solution
Hypertonic solution
A solution in which the concentration of solutes is greater than that of the cell that resides in the solution
Hypotonic solution
A solution in which the concentration of solutes is less than that of the cell that resides in the solution
Golgi apparatus
A system of concentrically folded membranes found in the cytoplasm of eukaryotic cells; functions in secretion from the cell by exocytosis.
Endomembrane System
A system of intracellular membranes that exchange material with one another, consisting of the Golgi apparatus, endoplasmic reticulum, and lysosomes when present.
Sodium-potassium pump
A transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell and potassium into the cell.
Phagocytosis
A type of endocytosis in which a cell engulfs large particles or whole cells
Cell theory
A widely accepted explanation of the relationship between cells and living things
A study was conducted to understand the factors controlling the rate at which molecules or ions travel across cell membranes. An artificial membrane was created that was composed of a phospholipid bilayer only. The speed at which various substances crossed this membrane was measured. Some substances can pass through an actual cell membrane much faster than they passed through the artificial membrane in this study. Which of the following statements best explains this finding?
Actual cell membranes have a variety of proteins embedded in the membrane that are absent in the artificial membrane.
A magnesium sulfate solution taken orally can cause a net movement of water into the large intestine, which results from water molecules diffusing through aquaporins embedded in the cells of the intestinal lining. By which of the following mechanisms do the water molecules most likely move into the large intestine?
By passive transport from an area of low osmolarity to an area of high osmolarity
Aldosterone (a steroid hormone) is a small, nonpolar, hydrophobic molecule that enters a target cell by moving across the plasma membrane, down a concentration gradient. Based on the information presented, how does aldosterone most likely enter target cells?
By simple diffusion
The cell membrane is selectively permeable due to its structure. Thus, the internal environment of the cell is distinct from the external environment of the cell. One biologist hypothesizes that small nonpolar molecules readily pass through the membrane. Another biologist alternatively hypothesizes that these types of molecules require channel and transport proteins that are embedded in the membrane in order to move across the membrane. Which of the following data would best refute this alternative hypothesis?
CO2 and N2 movement in and out of cells is unaffected when membrane protein activity is blocked.
Some cells, such as intestinal cells, exchange a lot of material with their surroundings. The surface-to-volume ratio of these cells affects the efficiency of material exchange. The table provides measurements of four different eukaryotic cells. Cell 1 2 3 4 Total surface area (μm2)40 60 80 100 Total volume (μm3)20 10 30 20 Based on the data, which cell is likely to be most effective in the exchange of materials?
Cell 2
Researchers have proposed a model of chloroplast evolution. According to the model, chloroplasts evolved from a small prokaryotic organism that was engulfed by an ancestral eukaryote. The engulfed prokaryote then formed an endosymbiotic relationship with the eukaryotic host. Which of the following observations best supports the model?
Chloroplasts and some prokaryotes share similar photosynthetic reactions.
Osmosis
Diffusion of water through a selectively permeable membrane
Membrane proteins
Embedded proteins that perform specific functions for the cell membrane.
Receptor endocytosis
Endocytosis initiated by macromolecular binding to a specific membrane receptor.
Some viral infections can lead to the rupture of the lysosome membrane. Which prediction of the effect of this disruption of cellular compartmentalization is most likely correct?
Hydrolytic enzymes will be released, which will cause cell death.
Hydrophobic vs. Hydrophilic
Hydrophobic- water fearing Hydrophilic- water loving
Researchers investigate the transport of a certain protein into cells by endocytosis. In an experiment, the researchers incubate the cells in the presence of the protein and measure the amount of the protein that is absorbed into the cells over a five-minute period. Based on their observations, what should the researchers do to further clarify how the availability of the protein outside the cells affects the rate of endocytosis of the protein?
Incubate the cells in the presence of several different concentrations of the protein.
In an experiment, researchers compared the growth of two different plants, plant X and plant Y. The researchers maintained the plants under nearly identical conditions and observed that plant X grew faster than plant Y. The researchers also observed that the inner mitochondrial membranes of plant X had more folds than did those of plant Y. Which of the following conclusions about increasing the number of folds in the inner mitochondrial membrane is best supported by the results of the experiment?
It increases the surface area available for ATP production, which results in faster cell growth.
Euglenids are single-cell eukaryotes that live in aquatic environments. The chloroplasts found inside euglenids are enveloped by three membranes, as represented in Figure 1. The inner membrane of euglenid chloroplasts resembles the thylakoid membrane. Figure 1. Simplified diagram of a euglenid, showing the structure of the chloroplast envelope Which of the following claims about the origin of the euglenid chloroplast is best supported by the three-membrane structure of the envelope?
It originated from the incorporation of a photosynthetic prokaryote into a eukaryotic cell by two endosymbiotic events.
In an experiment, researchers provided a radiolabeled amino acid to living plant cells. After one hour, the researchers determined the amount of the radiolabeled amino acid that was in each of several subcellular compartments. The results of the experiment are represented in the table. RELATIVE AMOUNTS OF RADIOLABELED AMINO ACID Nucleus Mitochondria Endoplasmic Reticulum Cytosol 2.1 2.7 1.9 1 Which of the following conclusions about the radiolabeled amino acid is best supported by the results of the experiment?
It was mostly incorporated into proteins that regulate and manage metabolic reactions.
Which of the following observations best supports the claim that mitochondria evolved from once-free-living prokaryotic cells by the process of endocytosis?
Mitochondria are surrounded by a double membrane.
Diffusion
Movement of molecules from an area of higher concentration to an area of lower concentration.
Facilitated diffusion
Movement of specific molecules across cell membranes through protein channels
plant vs animal cells
Plant - Chloroplast, cell wall, central vacuole; Animal - lysosomes, centrioles, and cholesterol.
Primary vs. Secondary Active Transport
Primary - transport directly coupled with ATP Secondary- ATP first used to create a gradient and the potential energy is used to drive something across membrane
Exocytosis
Process by which a cell releases large amounts of material
surface area to volume ratio
Ratio of a cell's outside area to its internal volume.
The figure shows a representation of a protein embedded in a cell membrane. The numbers indicate different structural regions of the protein. Based on the figure, which of the following statements best describes the relationship between regions 1 and 2 of the protein?
Region 1 is hydrophilic because it interacts with an aqueous environment, whereas region 2 is hydrophobic because it interacts with the interior of the membrane.
Intravenous (IV) therapy is used for fluid replacement in instances of dehydration in humans and other animals. One type of IV fluid is essentially a saltwater solution. To determine the best concentration for therapy in people, a team of students is researching the effects of solutions of different salt concentrations on red blood cells. The following observations were made from three different red blood cell samples viewed under a microscope. 0.3% Saline (Cells swell) 0.9% Saline (Cells unchanged) 1.5% Saline (Cells shrink) The team wants to extend the research project. What should the team of students do next to obtain data that are more conclusive?
Repeat the process with other salt concentrations.
Some membrane proteins help maintain the concentrations of ions inside a cell by transporting the ions across the cell's plasma membrane. Other membrane proteins form pores in the plasma membrane through which the ions can diffuse. A model showing the influence of membrane proteins on the movement of sodium (Na+) and potassium (K+) ions across a plasma membrane is presented in Figure 1. Figure 1. Section of a cell's plasma membrane, showing ion concentrations and membrane proteins Based on the model presented in Figure 1, which of the following changes will most likely result from a depletion of available ATPstores inside the cell?
The Na+concentration inside the cell will increase.
A group of mutations, known as MT-ND1, have been identified in mitochondrial DNA. These mutations are associated with a number of debilitating diseases stemming from the production of nonfunctional proteins in the mitochondria. Which of the following cellular deficiencies would most likely be related to these MT-ND1 mutations?
The cell is unable to complete reactions related to electron transport and ATP production.
How do the membranes of the endomembrane system work together?
The endomembrane system includes the nuclear envelope, lysosomes, vesicles, the ER, and Golgi apparatus, as well as the plasma membrane. These cellular components work together tomodify, package, tag, and transport proteins and lipids that form the membranes
Primary Endosymbiosis
The engulfment of a cyanobacterium by a larger eukaryotic cell that gave rise to the first photosynthetic eukaryotes with chloroplasts.
Secondary Endosymbiosis
The engulfment of a photosynthetic eukaryote by another eukaryotic cell that gave rise to certain groups of photosynthetic eukaryotes
cytosol
The fluid portion of the cytoplasm, excluding organelles and other solids.
Lysosomes digest food particles brought into a cell by endocytosis. After a vesicle containing food particles fuses with a lysosome, H+ ions are transported into the lysosome from the cytosol. This significantly lowers the pH of the lysosome relative to the cytosol and activates the enzymes that digest the particles. Which of the following best predicts what will happen to the lysosomal enzymes if the proteins that transport H+ ions from the cytosol into the lysosome are damaged?
The lysosomal enzymes will not become active, since there will be no active transport of H+ ions.
Gaucher disease is an inherited disorder in which cells of the body are unable to break down a particular type of lipid, resulting in a buildup of the lipid in some tissues and organs. Based on the information provided, Gaucher disease results most directly from a defect in the function of which of the following organelles?
The lysosome
Turgor pressure
The pressure inside of a cell as a cell pushes itself against the cell wall.
A certain type of specialized cell contains an unusually large amount of rough endoplasmic reticulum (ER). Which of the following functions is this cell type most likely specialized to perform?
The production and secretion of proteins
Stomata are pores on the surfaces of the leaves and stems of plants that regulate gas exchange between the plants and the atmosphere. Researchers found that the stomata density on the leaves of a species of plant change as the concentration of CO2 in the atmosphere changes. When grown at 350 ppm CO2 the plant has an average density of 300 stomata per mm2, but when grown at 400 ppm CO2 the plant has an average density of 250 stomata per mm2. Which of the following best describes how the ratio of the density of stomata (stomata per mm2) per CO2 concentration (ppm CO2) changes as the CO2 concentration increases?
The ratio decreases from 0.86 to 0.63, because fewer stomata are needed at higher CO2 concentrations.
Hereditary spherocytosis (HS) is a disorder of red blood cells that causes the cells to be smaller and spherical instead of having the usual flattened, biconcave shape. The average diameter of normal red blood cells is 7.2μm, and the average diameter of red blood cells in a person with HS was found to be 6.7μm. The normal red blood cell has an average surface area of 136μm2 and an average volume of 91μm3. Which of the following provides an accurate calculation of the surface area to volume ratio of an HS red blood cell, as well as a prediction of its effect on the efficient transferring of oxygen compared to a normal red blood cell?
The ratio is 0.89, and the cells are less efficient at transferring oxygen.
A scientist is studying the various prokaryotic and eukaryotic species found floating in a sample of water taken from a marine ecosystem. Which cellular component will be found in the widest range of organisms in the sample?
The ribosome, since all organisms need to synthesize proteins.
Which of the following transport mechanisms will be affected most directly by a temporary shortage of ATP molecules inside the cell?
The transport of glucose molecules against a concentration gradient
Researchers conducted an experiment to investigate the effects of a valinomycin treatment on skeletal muscle cells. Valinomycin is a naturally occurring substance that can be used as a drug. The results of the experiment are presented in the table. Relative Rates of ATP ProductionTime after Treatment Untreated CellsValinomycin-Treated Cells 5 minutes 1.00.310 minutes 7.72.7 Which of the following claims about the effects of the valinomycin treatment is best supported by the data presented in the table?
The valinomycin treatment caused a decrease in the activity of the mitochondria.
Solute potential
This measurement has a maximum value of 0; it decreases as the concentration of a solute increases.
Pressure potential
This measurement has a minimum value of 0 (when the solution is open to the environment); it increases as pressure increases.
Transmembrane proteins
Transmembrane proteins are integral proteins that do not extend all the way through the membrane.
Certain bacteria can use both ethyl alcohol and acetate as sources of nutrients. In an experiment where both nutrients are available to a bacterial population, the following results were obtained and graphed. What additional procedure would best help determine whether these movements are due to active transport or to passive transport?
Use two additional treatments, one containing only ethyl alcohol and one containing only acetate. Include a substance known to block ATP use by the plasma membrane. Compare the graphs of these two treatments to the original graph.
Beetroot cells contain a family of dark red pigments called betalains. The selectively permeable nature of the beetroot cells keeps the internal environment of the cell separate from the external environment of the cell. Researchers are interested in determining whether the selective permeability of beetroot cells is due to the cell membrane or if it is due to the cell wall. Exposure to cellulase is known to damage the structure of the cell wall. An experiment is set up in which beetroot cells are placed in an aqueous solution with cellulase and in one without cellulase. Which of the following results best refutes the alternative hypothesis that selective permeability is a consequence of the cell wall?
When beetroot cells are placed in a solution with cellulase, the solution remains clear.
How does surface area to volume area affect rates of diffusion?
When the cell increases in size, the volume increases faster than the surface area, because volume is cubed where surface area is squared. When there is more volume and less surface area, diffusion takes longer and is less effective
Ion channel
a complex of protein molecules in a cell membrane that form a pore through which ions can pass
Glycolipid
a lipid with one or more covalently attached carbohydrates
Lysosome
a membrane enclosed organelle originating from the golgi apparatus and containing hydrolytic enzymes
cell wall
a relatively rigid structure that encloses cells of plants, fungi, many protists, and most prokaryotes, and which gives these cells their shape and limits their expansion in hypotonic media
ribosome
a small particle in the cell that is the site of protein synthesis.
Nucleolus
a small, generally spherical body found within the nucleus of eukaryotic cells. The site of synthesis of ribosomal RNA
Chloroplast
an organelle bounded by a double membrane containing the enzymes and pigments that perform photosynthesis. Chloroplasts occur only in eukaryotes.
Mitochondria
an organelle in eukaryotic cells that contains the enzymes of the citric acid cycle, the respiratory chain, and oxidative phosphorylation
organelle
any of the membrane-enclosed structures within a eukaryotic cell. Examples include the nucleus, endoplasmic reticulum, and mitochondria
Flexible cell surface
as a cell grows larger, its surface area to volume ratio decreases. Unless the surface area can be increased, the cell volume will reach an upper limit. If the cell's surface is flexible, however, it can fold inward and become more elaborate, creating more surface area for gas and nutrient exchange
Figure 1. Testosterone movement across the cellular membrane Testosterone is a small steroid hormone that is important in cell signaling. Which of the following indicates where testosterone enters a cell and why it is able to cross at that point?
because testosterone is nonpolar and can diffuse through the membrane.
What factors affect diffusion?
membrane thickness surface area pressure differences coefficient of the gas
Vacuole
membrane-enclosed organelle in plant cells that can function for storage, water concentration for turgor, or hydrolysis of stored macromolecules
Simple diffusion
movement of a solute from an area of high concentration to an area of low concentration
Passive vs. active transport
passive: high to low, no energy, diffusion; active: low to high, energy, endocytosis
Cell membrane structure
phopholipid bilayer with embedded proteins
smooth er
portion of the endoplasmic reticulum that lacks ribosomes and has a tubular appearance
osmotic pressure
pressure that must be applied to prevent osmotic movement across a selectively permeable membrane
endocytosis
process by which a cell takes material into the cell by infolding of the cell membrane
Selectively permeable
property of biological membranes that allows some substances to pass across it while others cannot; also called semipermeable membrane
Peripheral membrane proteins
proteins associated with but not embedded within the plasma membrane
Integral membrane proteins
proteins that are at least partially embedded in the plasma membrane
Why are cells so small?
smaller cells have more surface area across which to pass oxygen, nutrients and waste materials
Nucleus
the centrally located compartment of eukaryotic cells that is bounded by a double membrane and contains the chromosomes.
Cytoplasm
the contents of the cell, excluding the nucleus
Origin of eukaryotes
the loss of a rigid cell wall allowed the cell membrane to fold inward and create more surface area, which facilitated the evolution of larger cells. As cells grew larger, cytoskeletal complexity increased, and the cell becamee increasing compartmentalized. endosymbiosis involving bacteria gave rise to mitochondria and (in photosynthetic eukaryotes) to chloroplasts.
Rough ER
the portion of the endoplasmic reticulum whose outer surface has attached ribosomes.
Water potential
the potential energy of a volume of water, expressed as a pressure
Vesicle
within the cytoplasm, a membrane enclosed compartment that is associated with other organelles; the golgi complex is one example