Cellular Biology - AP Biology

The cleavage furrow is the start of physical cell splitting, occurs during telophase, and is called cytokinesis. The cleavage furrow is mediated by motor proteins such as actin and myosin. They tighten a "ring" around the cell until it pinches off into two daughter cells. Note that plant cells also exhibit cytokinesis, but they do so without the formation of a cleavage furrow. Rather, they form a cell plate, which is made of the same material as their cell wall, cellulose.

The correct answer to this question is ATP.

Fermentation is the metabolic process that takes place in anaerobic environments to regenerate for glycolysis. ATP is the main product of cellular respiration and the molecular energy of the cell. The aerobic metabolism results in a very high yield of these energies because it can use oxygen as the final electron acceptor in the electron transport chain.

Oxygen is neither a product nor reactant in glycolysis. Glycolysis is unique in that it takes place within the cytoplasm of the cell and does not require oxygen. It is an anaerobic reaction that produces pyruvate, NAD, and ATP. Know the products and reactants of glycolysis.

The Krebs cycle takes place within the mitochondrial matrix of mitochondria. Glycolysis occurs in the cell's cytosol. The stroma is part of plant chloroplasts, thus it is not the site of the Krebs cycle.

Fermentation is a catabolic process which does not require oxygen. In contrast, Krebs cycle (citric acid cycle) and oxidative phosphorylation (chemiosmosis and electron transport) do use oxygen. Aerobic respiration is much more efficient than anaerobic respiration in producing ATP.

The correct answer is metaphase because this is the stage of mitosis where the chromosomes come together and line up in the middle forming the metaphase plate. These chromosomes then get pulled to either side in the anaphase stage.

The nucleolus is a structure found inside the nucleus. It is responsible for the production of rRNA, and also constructs the subunits of ribosomes.

Mitochondria are responsible for ATP production, and various chaperone proteins are responsible for directing substance transport within a cell. Several classes of proteins in the nucleus are involved in mRNA transcription and post-transcription modification, but these processes do not involve the nucleolus.

Desmosomes are the primary junction that helps keep tissues that are under a lot of stress, like skin, intact. Although tight junctions typically accompany desmosomes, their primary function is to prevent substances from passing between cells. Gap junctions are used for communication between cells, and intercalated discs are only found in cardiac muscle tissue.

The simple answer here is that all of these organelles have a membrane, except for ribosomes. Nuclei, mitochondria, chloroplasts, and cells as a whole have transmembrane proteins spanning the lipid bilayer, which can be used for transport or other purposes. Ribosomes are mostly comprised of rRNA and do not have membranes; thus, they will not bear transmembrane proteins.

The lysosome is an organelle that is used to digest broken cellular machinery or foreign particles. It maintains an acidic environment inside by pumping hydrogen ions in, not out. This environment helps denature the things it needs to digest, and is the most effective pH for the digestive enzymes that are inside.

The other structures do not maintain acidic environments, and would need the capability of removing protons.

The rough endoplasmic reticulum is given its name due to the ribosomes present within its membrane. These ribosomes are able to translate proteins, which are then modified within the endoplasmic reticulum and sent to the Golgi apparatus.

Ribosomes are the only cellular machinery capable of translating RNA into proteins.

The Golgi apparatus is a series of flattened membrane sacs found in the cell. It receives vesicles filled with proteins from the rough endoplasmic reticulum. The Golgi apparatus is responsible for recognizing proteins based on their signal sequences and sending concentrations of similar proteins to various parts of the cell. It can also deliver proteins out of the cell using secretory vesicles. The membrane sacs of the Golgi apparatus are constantly used and regenerated to create vesicles of packaged proteins.

Muscle contraction is accomplished using the function of microfilaments, namely actin and myosin. Microtubules are not a key player in muscle contraction, but are used to create the mitotic spindles, flagella, and cilia. Microtubules are a key element of the cytoskeleton, and are generally involved in structural aspects of the cell.

The mitochondria are membrane-bound organelles involved in the process of cellular respiration. Specifically, the Krebs cycle takes place in the matrix of the mitochondria and the electron transport chain takes place along the inner mitochondrial membrane. During aerobic respiration, oxygen is used as the final electron receptor of the electron transport chain and generates water as a byproduct. Without oxygen, the mitochondria cannot perform oxidative phosphorylation, and the cell must rely on glycolysis for energy.

Oxygen serves as the terminal electron acceptor for the electron transport chain. Electrons are donated by NADH molecules and passed through several different proteins to generate the proton gradient in the intermembrane space. Upon reaching the final protein, the electron is bonded to an oxygen molecule to create water. Without oxygen, there would be nowhere for the electrons to go after being pumped through the electron transport chain, and aerobic cellular respiration would be impossible.

At metaphase the spindle microtubules that are attached to the kinetochores of the chromosomes move them to the metaphase plate, an imaginary structure at the midway point between the two poles of the cell.

Prophase is the first phase of mitosis in which chromatin coils and forms chromosomes, the spindle apparatus begins to form, and the nuclear membrane breaks down. The second, third, and fourth phases are metaphase, anaphase, and telophase, respectively.

Metaphase is the second phase of mitosis in which spindle fibers move the chromosomes to the center of the cell where they are aligned. Prophase is the first phase of mitosis, anaphase is the third phase, and telophase is the fourth and final phase.

Anaphase is the third phase of mitosis in which each sister chromatids of each chromosome toward the opposite poles of the cell. Prophase is the first phase of mitosis, metaphase is the second phase, and telophase is the fourth and final phase.