The correct answer is B. Cells move necessary material into and out of the cell via the cell membrane. If cell volume were too high, this exchange would be impaired. The plasma membrane is quite tough and does not limit cell size. There is no set ratio of the volume of cytoplasm to the volume of organelles in any cell. Cell size is unrelated to motility.

A is the correct answer. Phospholipids are a primary component of the cell membrane. ATP is the energy-giving molecule that allows cells to function. It is not a structural molecule in the cell membrane. The endoplasmic reticulum is an organelle within the cell. Actin filaments are part of the cytoskeleton, not the plasma membrane.

The correct answer is D. Microtubules extend through the plasma membrane of unicellular organisms to form the "backbone" of flagella and cilia. Intermediate fibers are part of the cytoskeleton but are distinct from microtubules. Permeases are transport proteins in the cell membrane. The hydroplasm is the colorless liquid part of the cytoplasm.

The correct answer is A. Transport proteins actively pump sodium and potassium against the concentration gradient into and out of the cell. Endocytosis involve moving large particles into the cell after they have been coated with protein and attached to the plasma membrane. This is not active transport. In facilitated diffusion, proteins assist in molecule transport, but because the molecules are moved with the concentration gradient, this is not active transport. Diffusion is the unassisted movement of molecules along the concentration gradient into and out of the cell.

B is the correct answer. Glycolysis is the breaking down of the carbon bonds in glucose in the anaerobic environment of the cytoplasm. Phosphorylation is the transfer of inorganic phosphate from one molecule (usually ATP) to another. Exocytosis is the process in which the cell rids itself of unwanted material by encasing it in a membrane, which attaches to the plasma membrane and then releases the material to the outside of the cell. Respiration is the oxidation of glucose that occurs in the mitochondria.

The correct answer is C. In the Krebs cycle, oxidation of carbon releases energy that transofrms ADP to ATP, and some remaining energy is used to turn NAD into the electron-carrying NADH. Though energy released in the Krebs cycle turns ADP into ATP, neither transports electrons. PGAL is an intermediate molecule produced during glycolysis. It is not part of the Krebs cycle and is not an electron carrier.

D is the correct answer. Photophosphorylation involves photons hitting pigments to cause an electron cascade that result in the transfer of phosphate to create ATP. Photosynthesis refers to the entire process of creating food and energy from sunlight, carbon dioxide, and water. It does not refer to this specific part of the process. Oxidation does not occur when photons strike plant pigments and phorphorylate ATP. Photolysis is the process in which an activated pigment splits a water molecule.

C is the correct answer. PEP has a greater affinity for carbon dioxide that would otherwise be lost during photorespiration, so it makes this form of photosynthesis more efficient. Carbon-12 is used in photosynthesis, but it is not a form of photosynthesis in plants. Photorespiration occurs in plants under stress and tends to release, or waste, large amounts of carbon dioxide. The Calvin cycle is the normal mode of plant photosynthesis, which does not use carbon dioxide most efficiently.

The correct answer is C. During metaphase, the centromeres attached to the duplicated chromosomes line up along the metaphase plate in the center of the cell. Replication of chromosomes occurs duing interphase. The spindle forms during prophase. The nuclear envelope begins to disintegrate also during prophase.

D is the correct answer. The cell plate forms after telophase in order to separate the two daughter cells. During interphase, the chromosomes are duplicated. Anaphase is the stage during which the spindle pulls apart the centromeres. Telophase sees the re-formation of the nuclear envelope and disappearance of the spindle.

The correct answer is A. Pili are tiny hairs on the outer surface of prokaryotes, which beat the pili rhythmically in order to move around. Budding and binary fission are forms of asexual reproduction, and are not involved in locomotion. Pili, which are exterior hairs on the cell, are not involved in ATP creation within the cell.

B is the correct answer. The non-sulfur eubacteria, particularly the cyanobacteria, engage in photosynthesis that adds oxygen to the atmosphere. Methanogens are archaebacteria, not prokaryotes. Euglenas are protists (eukaryotes), not prokaryotes. Chemotrophs are prokaryotes that derive energy from inorganic materials. Some release nitrogen to the atmosphere, but not oxygen.

The correct answer is D. Protists are eukaryotes, which are characterized by their nuclear envelope and membrane-bound organelles. Only some protists are marine. Prokaryotes, in the Kingdom Monera, have naked DNA. Relatively few protists are exclusively parasitic.

The correct answer is A. The Phaeophyta contain the kelps, which are large, multicellular, plant-like algae that live in "forests" in cool, shallow seawater. Division Chrysophyta consists of the single-celled diatoms. The Chlorophyta are the green algae that may be either uni- or multicellular. Division Rhodophyta contains the red algae, seaweeds that occur in warm, tropical ocean waters.

B is the correct answer. Viruses are genetic material (RNA or DNA) wrapped in a protein coat. A virus is not a cell, as it lacks all cell components and cannot perform any cell functions on its own. The Kingdom Monera contains prokaryotic cells, and viruses are not cells. Parasitic protozoans are also cells, even though viruses are the ultimate parasites.

C is the correct answer. Mycorrhizae is the mutually beneficial relationship between plant roots and the fungi that live in or on them. Ascii are the sacs produced by Ascomycota during sexual reproduction. Hyphae are the filamentous components of the mycelium. Rhizoids are the structures that anchor members of the Division Chytridiomycota to their substrate.

The correct answer is D. Retroviruses use RNA as a template for synthesizing DNA. Retroviruses are not simpler. All viruses reproduce inside living cells. Most viruses use DNA as a template for synthesizing RNA.