Chapter 5 Study Guide - Study Guide 5 UNIT II: - Cell...

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Study Guide 5 UNIT II: - Cell Structure & Function - Inside the Cell, Cell-Cell Interactions - Respiration and Fermentation - Photosynthesis - Cell division VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV VVVVVVVVVVVVVV. Overview: Organelles and the division of cellular labors; As cells increase in volume, their surface area increases more slowly. This limits the size that cells can reach, since after a certain amount of growth, a cell’s membrane may not have enough surface area to absorb enough nutrients to “feed” its volume. 1. Prokaryotic cells are the smallest (around 1 micron in diameter). 2. Eukaryotic cells can exceed 10 microns in diameter. This is possible because they increase their effective surface area by generating membrane-bound organelles . Organelles are sub-cellular compartments that partition the chemical reactions of the cell. Compartmentalization decreases distances that molecules have to travel before they take part in reactions, thus increasing the efficiency of cellular metabolism. B. Prokaryotes : general structure: The typical bacterium ( Figs. 7.1, 7.2 ): note absence of organelles (e.g., a nucleoid that contains DNA but has no membrane). Note also the cell wall (typical of most prokaryotes) and the flagellum (plural, flagella) for motility. C. Eukaryotes: organelles mean a division of cellular labors; Typical animal, plant cells ( Fig. 7.6 ): note common structures, and those unique to plant vs animal cells. The parts of a cell can be separated by differential centrifugation ( Box 7.1 ). 1) The nucleus ( Fig. 7.7 ): largest organelle; contains genes (in form of DNA). Information in genes flows from the nucleus to the cytoplasm: Transcription (in nucleus) Translation (in cytoplasm) DNA--------------------------------------> RNA ------------------------------------->protein a) Even the information to make the ‘machines’ that make proteins (ribosomes, Fig. 7.8 ) is stored as genes on DNA; the assembly of ribosomes from RNA and proteins begins in the nucleus. Thus, some pretty big molecules, and even structures, must get back and forth across the nuclear membrane. The nuclear envelope is a double membrane with pores ( Fig. 7.23 ). Pores are one solution to moving large molecules across membranes ( Fig. 7.24 ); there are others! To enter the nucleus, proteins have evolved to contain nuclear localization signals ( Fig. 7.25 ) b) The space enclosed by the 2 membranes of the nuclear envelope ( Fig. 7.22 ) is
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continuous with the rough endoplasmic reticulum (i.e., it is functionally the same space!).
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This note was uploaded on 11/22/2009 for the course BIO SCI 150 taught by Professor Geraldbergstrom during the Spring '08 term at Wisconsin Milwaukee.

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Chapter 5 Study Guide - Study Guide 5 UNIT II: - Cell...

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