Chapter 7 Study Questions PDF

Preview

Summary

Chapter 7 Study Questions...

Description

Ashley Batista Biology discussion –section 6 Biology 141

Biology 141 Study Questions Chapter 7 1. Components found in both prokaryotic and eukaryotic cells include: a. Cell walls which provide protection and structural support. b. Chromosomes which store information. c. Cytoskeletons which provide structural support and movement of materials. d. Plasma membranes which maintains intracellular environments through selective permeability. e. Ribosomes which aids in protein synthesis. f. Organelles which perform several tasks ranging from storage and organization to isolating certain enzymes that interact with toxic chemicals. 2. Major differences between prokaryotic and eukaryotic cells include: a. Position of DNA: nucleoid vs. nucleus. b. Cytoskeleton: much more limited in prokaryotes related to eukaryotes which can be found throughout the whole cell. c. Organelles: restricted amounts and kinds of organelles in prokaryotes related to eukaryotes. d. Membranes: wide-ranging membranes in photosynthetic species of prokaryotes. e. Size: prokaryotes are typically small when compared to eukaryotes. 3. Compartmentalization allows unharmonious chemical reactions to be separated which increases overall efficiency of the cell and decreases possible errors. Isolation of these reactions is good when the substrates for one organelle is all gone and it can send for more that only have to go a short distance to get there. Also, clustering decreases distance between specific substrates and enzymes and increases the speed of chemical reactions. 4. The “diffusion problem” is the conflict of diffusing and sending materials within the cell and it is solved through several components such as compartmentalization, localization signals, and movement regulation to control traffic and collisions. 5. Components that are found only in eukaryotic cells include: a. Chloroplasts which help in the manufacturing of sugars through photosynthesis. b. Mitochondria which are very important for ATP manufacturing. c. Peroxisomes which oxidizes fatty acids and other compounds. d. Vacuoles which specialize as storage depots but can vary among specialization based on the type of large enzyme concentration carrying inside of it (e.g. color, toxins, carbs, etc.).

e. Lysosomes which help with digestion and recycling materials for either waste or reuse. f. Golgi apparatus which performs lipid, protein, and carbohydrate processing. g. Smooth endoplasmic reticulum which specializes in the processing and synthesis of lipids. h. Rough endoplasmic reticulum which specializes in the processing and synthesis of proteins. i. A nucleus which holds DNA, helps with structural support, and hold the ribosomal subunits that aid with protein synthesis. 6. The difference between the nuclear envelope and the plasma membrane is that the inside surface of the envelope is connected to proteins which form a lattice-like sheet called the nuclear lamina. Within the envelope, there are elaborate nuclear pore complexes which are highly selective to proteins and nucleotides needed for DNA and RNA construction. 7. An experiment including nucleoplasmin opened up new discoveries of nuclear import. The proposed questions was “Does the nucleoplasmin protein contain a ‘send to nucleus’ signal?”. If the answer were yes, the protein would contain a signal either in the tail or core region. Both were labeled with radioactive atoms and injected into cells. The result was that the labeled tail parts of the protein were found in the nucleus while the core parts were not. The uptake of the tails into the nucleus is active transport because the “zip code” allows the pore complex to open in a way that allows only that protein to enter freely but it is still an energy-demanding mechanism when it comes to large molecules that have to be assisted by special transport proteins. 8. Signal sequences are not unique to nuclear proteins because proteins can also be sent to peroxisomes, mitochondria, and chloroplasts. The signal sequences on proteins targeted to these areas are different because they are all at different locations and have different specializations which force the signals to make the correct sequence. 9. The main components of the endomembrane system is the rough endoplasmic reticulum and the Golgi apparatus. 10. The secretory pathways hypothesis said that proteins that were made for secretion out of the cell were mainly found in the endomembrane system. This hypothesis was confirmed through an experiment called the Pulse-Chase experiment where cells were exposed to a high concentration of an amino acid for a short time and then replacing that amino with the normal version of it. The meaning of the pulse-chase experiment was to track the proteins movement through the cell to discover a secretory pathway. The pulse was meant to mark a population of molecules during a specific time frame while the chase was meant to allow that specifically marked group to be identified easily. 11. The signal hypothesis is “Nucleoplasmin contains a discrete ‘send to nucleus’ signal that resides in either the tail or core region”. To test this hypothesis, researchers separated the tail and core regions of this molecule, labeled each with a radioactive atom so that

they could be detected in the cells, and injected them into two separate cells. When the tails entered the nucleus, researchers discovered the nucleus localization signal that acted as a zip code for materials that would be sent to the nucleus. This hypothesis also showed how proteins sent to other organelles consisted of signal sequences similar to the NLS. Proteins that are made in the ER are transported to the Golgi through membranous vesicles. 12. Receptor-mediated endocytosis is when macromolecules outside of the cell binds to receptors on the membrane in order to catalyze uptake of material from outside of the cell. This kind of endocytosis relates to lysosomes because the endocytic vesicle merges with the early endosomes. Its lumen is then acidified through proton pumps and soon it matures into a late endosome which receives digestive enzymes from the Golgi apparatus and then becomes a full lysosome....