Biology Ch. 6 HW
Beginning within the nucleus, the first step leading to the synthesis of a polypeptide is _____.
transferring of information from DNA to messenger RNA
Sites of protein synthesis All proteins are synthesized by ribosomes in the cell. Some ribosomes float freely in the cytosol, while others are bound to the surface of the endoplasmic reticulum. Most proteins made by free ribosomes function in the cytosol. Proteins made by bound ribosomes either function within the endomembrane system or pass through it and are secreted from the cell. Which of the following proteins are synthesized by bound ribosomes? Select all that apply.
ER protein insulin lysosomal enzyme
_____ aid in the coordination of the activities of adjacent animal cells.
Gap (communicating) junctions
Which of the following are common traits of chloroplasts and mitochondria?
Both have their own DNA.
The structure of a chloroplast is closely tied to its function as the site of photosynthesis. Diagram showing chloroplast structure. Some of the following statements are true for chloroplasts; others are true for mitochondria. Which statements are true for chloroplasts? Select the three that apply.
They contain the green pigment chlorophyll. They are the sites of reactions that convert solar energy into chemical energy. They have membranous sacs called thylakoids that are surrounded by a fluid called stroma.
The nuclear pore complex regulates molecular traffic in and out of the nucleus. Which molecules and cellular components pass through the nuclear pore during normal cellular activity? Select all that apply.
ribosomal subunits mRNA
Motor proteins are responsible for moving vesicles and organelles within the cell. Motor proteins move along protein "tracks." In the example shown in the Visualizing figure, what are those tracks made of?
actin
The primary role of _____ is to bind animal cells together.
desmosomes
Which of these cell junctions form a barrier to the passage of materials?
tight junctions
Pulse-chase experiments and protein location Scientists can track the movement of proteins through the endomembrane system using an approach known as a pulse-chase experiment. This experiment involves the "pulse" phase: Cells are exposed to a high concentration of a radioactively labeled amino acid for a short period to tag proteins that are being synthesized. the "chase" phase: Any unincorporated radioactively labeled amino acids are washed away and large amounts of the same, but unlabeled, amino acid are added. Only those proteins synthesized during the brief pulse phase are radioactively tagged. These tagged proteins can be tracked through the chase period to determine their location in the cell. The data below were obtained from a pulse-chase experiment in which cells were examined at different times during the chase period. The numbers represent the radioactivity (measured in counts per minute) recorded at each of the indicated sites. The higher the number, the greater the radioactivity. Based on these data, what is the most likely function of the cells in this experiment?
phagocytosis
