Cell Biology - SAT Subject Test in Biology

Plants, bacteria, and fungi have both a membrane as well as a cell wall. On the other hand, animal cells have only a membrane.

Plant cell walls are made of cellulose, a polysaccharide.

Bacterial cell walls are composed of peptidoglycan, a protein and sugar moiety.

Fungal cells have cell walls composed of chitin, a polysaccharide similar in structure to cellulose.

The endoplasmic reticulum is made up of membrane-enclosed spaces used for the trafficking of materials that will be secreted from the cell. Therefore it is involved in exocytosis, not endocytosis. The smooth ER is involved in metabolism and lipid synthesis. The rough ER contains ribosomes accounting for its rough appearance and allowing it to be involved in protein synthesis.

The Golgi aparatus does not synthesize lipids. Lipids are synthesized in the smooth ER.

The rough endoplasmic reticulum is described as "rough" because it is covered in ribosomes, which look like tiny beads along its surface. The smooth endoplasmic reticulum doesn't have these ribosomes all over its surface, so it appears flat and is described as "smooth" for this reason. The ribosomes function to make proteins.

A defining characteristic of prokaryotes is the lack of a true nucleus. Prokaryotic cells do contain ribosomes, DNA, and cell walls, and some but not all prokaryotes are capable of photosynthesis.

Microtubules are hollow tubes made up of polymerized tubulin that provide support throughout the cell.

Enzymes do not alter the equilibrium constant because enzymes are not consumed in the reaction.

Hint: Write out the equation for the equilibrium constant and notice that there is no variable for enzymes.

Enzymes are sensitive to temperature and pH, as high temperatures and very low pH can cause denaturation of an enzyme. Enzymes are only optimal at certain pH and temperature ranges.

G1 is considered to be the most important checkpoint in the cell cycle. G1 precedes S and G2, so it decides if the cell is ready to commit the resources to go through the S phase, G2 phase, M phase, and then finally division. S is crucial for the replication of cellular materials and the duplication of DNA, but if the cell cannot pass G1, then it will never reach S phase.

During interphase, you have G1, or gap 1, in which the cell grows. Then you have S phase, in which the cell synthesizes its DNA. Finally, you have G2, or gap 2, in which the cell continues to grow again.

The G2 checkpoint of cell division prevents the cell from entering the mitotic or dividing phase until all chromosomes have accurately been replicated. Other answers: "Prevents sister chromatids from separating before each chromatid is secured to a spindle microtubule" refers to the spindle or M checkpoint. "Initiates the cell division process if conditions are favorable" and "Ensures that the cell has matured to a sufficient state before beginning synthesis" refer to functions of the restrictive or G1 checkpoint. "Ensures that each daughter cell has received the correct number of chromatids after cell division" is incorrect since there is no checkpoint in cell division to error check the results of mitosis.

When a molecule binds to a receptor on a cell surface, it means that a signal has been received by that cell. In this case, the cell that sent the signal is the same cell that is receiving the signal. Autocrine signaling is the term that describes a cell sending a signal to itself ("auto" in this context means self). Exocrine signaling occurs when a substance is secreted through a gland or duct. Endocrine signaling occurs when a substance is secreted into the bloodstream. Paracrine signaling occurs when a cell sends a signal to nearby cells (often to change the behavior or properties of those cells).

Cellular respiration is NOTan anaerobic process. It is exactly the opposite! Cellular respiration uses oxygen as its final electron acceptor making it an aerobic process. Anaerobic process do not use oxygen.

Each molecule of glucose produces 2 pyruvate molecules. Each of these pyruvate molecules go through the citric acid cycle and produce 1 ATP each, resulting in 2 ATP total.

Anaerobic respiration takes place when oxygen is low, such as when lactic acid fermentation takes place in human muscle tissue. This can be painful and cause some of the cramps experienced during intense exercise. Anaerobic respiration is much less efficient at producing ATP than aerobic respiration; it only produces 2 ATP per glucose molecule vs. 36 net ATP in aerobic respiration.

The electron transport chain is found on the inside of the inner mitochondrial membrane. It is not used to transport proteins; instead, it generates ATP to be used as an energy source by the cell. The electron transport chain is found in plants and animals (though the one found in plants operates very differently than the one found in animals). Oxygen is the final electron acceptor, not glucose.

There are no homologous pairs in mitosis. Mitosis has sister chromatids that separate and result in two identical daughter cells. Meiosis has homologous pairs because it occurs in sex cells and has one chromosome from the father and the other from the mother. These chromosomes pair up in Metaphase I and then separate in Anaphase I. Mitosis occurs in somatic cells so there is only one chromosome made up of two sister chromatids that separate during Anaphase.

Crossing over occurs during Prophase I. During Prophase I, chromatin condenses and homologous chromosomes come together to form a tetrad. At this point, sometimes pieces of the chromatids within the chromosomes break off and exchange DNA. This process is known as "crossing over." This cannot occur in Prophase II because there are no homologous chromosomes in this stage, and therefore there isn't any different DNA to exchange.