Biology Homework Chapter 4: Cell Cytoplasm and Internal Structure
Textbook assignment: Chapter 4: A Tour of the Cell, sections 14-19. Read through the end-of-chapter summary and do a mental self-test using the multiple choice questions.
- 4.13-4.15 Mitochondria and chloroplasts are the energy converters of the cell. We will spend an entire chapter on the function of each one: chapter 6 describes cellular respiration in the mitochondria, and chapter 7 describes photosynthesis in the chloroplasts. For now: what is the function of each of these two organelles? Where are they found in the cell? Are both found in plant and animal cells? In prokaryotic or eukaryotic cells? How do biologists explain the double membranes that surround both organelles?
- 4.16 The microfilaments, intermediate filaments, and microtubules serve several purposes: these structures hold the shape of the cell, and hold the components inside the cell in place. They also help rearrange organelles during cell reproduction.
- 4.17 The same components that hold the cell together and regulate transport of materials across the membranes also separate the cell into compartments. The cytoskeleton is a web of microfilaments, intermediate filaments, microtubules, and centrioles that hold cell organelles in place. New methods of staining different molecules allow us to identify specific structures in the cytoskeleton.
- 4.18 Similar structures form the flagellum and cilia that enable single-celled organisms to move through fluids.
- 4.19 Cells excrete materials, including glycoproteins and collagen fibers, that extend above the cellular membrane and interact with fluids and solutes outside the cell to form an extra-cellular matrix. Note: the fact that we describe this as a matrix means it, too, has some structure; it is not just a random mash of proteins and fats.
- 4.20 The surfaces of eukaryotic animal cells can join the cells in three major ways (tight junctions, anchoring junctions, and gap junctions), allowing cells to exchange materials, or to stick together to form complex tissues.
- 4.21 Plant cell walls provide support as well as filters for nutrients and barriers to infection. Special channels called plasmodesmata allow plant cells to pass materials from one cell to another.
- 4.22 We can group organelles by the functions that they perform in the cell. This helps us identify and understand why some organelles are similar: they perform similar functions across different kinds of organisms. It also helps us compare differences in cell structure between different kinds of organisms, such as the differences in cell surfaces in plants and animals. (Think about categories again: what might happen to our groupings if we changed from functional processes to structural components?)
Read the following weblecture before chat: Cell Structure 2
Take notes on any questions you have, and be prepared to discuss the lecture in chat.
Rather than making you suffer through trying to figure out my drawings of cell structure, I figured it was time for a web tour, especially since some of the information and pictures available now are really amazing. As you study these, keep in mind the four fundamental parts of the cell and the organelles you will find in eukaryotic cells.
The best introductory level website on cell structure and variety is (in my opinion) Cells Alive! One of the problems with static pictures in you book is that it is hard to imagine the cells carrying out their individual tasks. After you click on the link above, explore the following locations on the site:
- Under "Interactive" on the left navigation menu, click on "Cell Models" and start the Animation.
- Select Plant Cell.
- Move around the cell to identify different structures.
- Look up the description of each structure by clicking on the links in the list at the bottom of the page. Return to the diagram by clicking on the red link in the bottom right corner of the picture area.
- Repeat your investigations for the animal cell.
Chat Preparation Activities
- Essay question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
- Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.
- Required: Complete the Mastery Exercise with a score of 85% or better.
- Optional: Test yourself with the textbook multiple choice questions and note any that you miss that still don't make sense. Bring questions to chat!
- Go to the Moodle and take the quiz for this chapter.
Read through the lab for this week; bring questions to chat on any aspect of the lab, whether you intend not perform it or not. If you decide to perform the lab, be sure to submit your report by the posted due date.
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