Chapter 6: A Tour of the Cell Name: 1. Label the prokaryotic cell: cell wall, plasma membrane, chromosome, nucleoid, cytoplasm, flagella. 2. Explain the relationship of surface area to volume. 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. 3. Why does alcohol abuse increase tolerance to other drugs such as barbiturates? Barbiturates, alcohol, and many other drugs induce proliferation of smooth ER which are associated with detoxification enzymes, thus increasing rate of detoxification. 4. What is the pH of a lysosome? Why do you think it is that pH? The pH of lysosome is 5. The reason that is the pH is because the enzymes require an acidic environment in order to work properly. 5. Describe the process of phagocytosis? Phagocytosis begins when white cells called phagocytes recognize bacteria invading the body (pathogens). The cell membrane of one of these phagocytes then fuses around a single bacterium, engulfing it within a cellular compartment, which is then called the phagosome. This phagosome then fuses with a lysosome, which contains acidic enzymes and toxic chemicals, forming a phagolysosome. These enzymes and chemicals then break down and digest the bacterium, destroying it. After the bacterium has been destroyed, the macrophage absorbs any of the material that is useful and gets rid of the rest. 6. Explain the role of lysosomes in Tay-Sachs. A lipid digesting enzyme is missing or inactive, and the brain becomes impaired by an accumulation of lipids in the cells. This disorder is categorized as a lysosomal storage disease. 7. What organelles are involved with the endomembrane system? Explain how each functions in this system. In eukaryotes the organelles of the endomembrane system include: the nuclear membrane, the endoplasmic reticulum, the Golgi apparatus, lysosomes, vesicles, endosomes, among others. 8. Why is the inner membrane of the mitochondria highly folded? Because the cristae increase the surface area for chemical reactions. 9. Describe the organization of microtubules in a centriole. The microtubules in a centriole is arranged with nine sets of triplet microtubules arranged around a ring. 10. Explain how the cilia and flagella are alike and how they are different. In eukaryotes, cilia and flagella are similar in their internal structure (the 9+2 arrangement of microtubules). Both structures move, but they differ in their length and in how they move. Cilia are short and move in wave-like motions. Flagella are much longer and move with a whip-like motion. 11. How do motor proteins dyneins cause movement of cilia? Include the role of ATP in this movement. A dynein molecule passes through a complex cycle of movement caused by changes in shape of the protein. ATP provides energy. 12. Describe the composition of the ECM. Highly viscous proteoglycans (heparin sulfate, keratin sulfate, chondroitin sulfate), which cushion cells Insoluble collagen fibers, which provide strength and resilience. Soluble multi-adhesive extracellular matrix proteins (fibronectin, laminin), which bind proteoglycans and collagen fibers to receptors on the cell surface. 13. What are intercellular junctions in plants called? What is their function? Intercellular junctions are called plasmodesmata (little tunnels). It is a channel through the cell wall that allows molecules and substances to move back and forth as needed. 14. Summarize the role of the 3 types of intercellular junction seen in animal cells. Three intercellular junctions between animal cells are tight junction where proteins hold adjacent cell membranes tightly together, creating an impermeable seal across a layer of epithelial cells, Desmosomes (anchoring junctions) are reinforced by intermediate filaments and rivet cells into strong sheets, Gap junctions (communicating junctions) are cytoplasmic connections that allow for the exchange of ions and small molecules between cells through proteinlined pores. 15. Why was compartmentalization important to eukaryotic cells? Every part of the cell is trying to use as little energy as possible and to also not waste anything, so releasing a bunch of calcium or glucose and making sure it goes directly to where it needs to go is crucial. You want the right amount to be there to start the reaction and not to accidentally get involved in another reaction. Complete the following table with important information. Find TEMs of each organelle as well as diagrams. Be sure you know what each looks like and all of its functions. TEM Picture & diagram Organelle description & location Function Nucleus Inside its fully enclosed nuclear membrane, it contains the majority of the cell's genetic material. This material is organized as DNA molecules, along with a variety of proteins, to form chromosomes. Center for animals, and the periphery for plant cells. Stores the cell's hereditary material, or DNA, and it coordinates the cell's activities Ribosomes Ribosomes are a cell structure that makes protein. Ribosomes can be found floating within the cytoplasm or attached to the endoplasmic reticulum. Makes proteins from messenger RNA (mRNA) by linking amino acids together. Endomembrane system: Rough ER Rough ER is found throughout the cell but the density is higher near the nucleus and the Golgi apparatus. A series of connected flattened sacs, part of a continuous membrane organelle within the cytoplasm of eukaryotic cells, that plays a central role in the synthesis of proteins. Ribosomes on the rough endoplasmic reticulum are called 'membrane bound' and are responsible for the assembly of many proteins. This process is called translation. Smooth ER A meshwork of fine disk like tubular membrane vesicles, part of a continuous membrane organelle within the cytoplasm of eukaryotic cells, that is involved in the synthesis and storage of lipids. The smooth ER also regulates and releases calcium ions and processes toxins. Golgi apparatus A complex of vesicles and folded membranes within the cytoplasm of most eukaryotic cells, involved in secretion and intracellular transport. They are located very near the rough endoplasmic reticulum and hence near the nucleus. A major function is the modifying, sorting and packaging of proteins for secretion. It is also involved in the transport of lipids around the cell, and the creation of lysosomes. Lysosomes are organelles inside animal cells that are fully membrane-bound. It is scattered in the cytoplasm They digest and contain excess or worn out organelles, food particles, and engulfed viruses or bacteria. Lysosome Vacuole Vacuoles are distributed throughout the cell's cytoplasm. The largest organelle in the cell. It is surrounded by a membrane and functions to hold materials and wastes. Performing functions such as storage, ingestion, digestion, excretion, and expulsion of excess water. Mitochondrion The mitochondrion is a double-membrane-bound organelle found in most eukaryotic organisms. Mitochondria are located in the cytoplasm of cells along with other organelles of the cell. The main job of mitochondria is to perform cellular respiration. This means it takes in nutrients from the cell, breaks it down, and turns it into energy. Chloroplast A chloroplast is an organelle unique to plant cells that contains chlorophyll. The chloroplast is located throughout the cytoplasm of the cells of plant leaves and other parts depending on the type of plant. Chloroplasts work to convert light energy of the Sun into sugars that can be used by cells (photosynthesis). Peroxisome Membrane-bound organelle occurring in the cytoplasm of eukaryotic cells. Peroxisomes play a key role in the oxidation of specific biomolecules. They are scattered in the cytoplasm. Break down fatty acids to be used for forming membranes and as fuel for respiration; and transfer hydrogen from compounds to oxygen to create hydrogen peroxide and then convert hydrogen peroxide into water.
