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2 Solns prob set 1

2 Solns prob set 1 - BILD 2, Multicellular Life ­...

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Unformatted text preview: BILD 2, Multicellular Life ­ ­Problem set #1 solutions Page 1 1. Just look carefully at the two diagrams. Here are some similarities: Both kinds of cells include a plasma membrane, a nucleus; mitochondria; rough endoplasmic reticulum; smooth endoplasmic reticulum; cytoskeleton that includes microfilaments, microtubules, and intermediate filaments; Golgi apparatus. In addition, animal cells contain centrosomes and lysosomes; they may have a flagellum. In addition, plant cells contain chloroplasts, a central vacuole, and each is surrounded by an extracellular cell wall that is interrupted by plasmodesmata. 2. i. The bones in your skeleton are rigid because they provide the structural basis for upright posture. Teleological. ii. Homeostasis is maintained by negative feedback control because a negative feedback loop tends to resist change in the state of the loop's components. Teleological. iii. The nervous system plays a critical role in coordinating different organs because you would die if each organ functioned on its own. Teleological. iv. Functions within multicellular plants and animals can be more complicated than in unicellular organisms because cells can be differentiated into specialized tissues. Mechanistic. v. In the condition called osteoporosis, bones become weaker because Ca2+ salts are removed from the extracellular space in the bones. Mechanistic. 3. a. A tissue is a group of cells that are specialized to carry out a particular function or a particular set of functions. (Or you can look in the glossary at the end of your textbook.) b. Organs are generally made up of one or more tissues. c. i. Bone ­ ­Bone consists of living cells (osteoblasts), extracellular proteins called collagen, and a mineral deposit that consists largely of calcium, carbonate, and phosphate. Bone is relatively rigid, but not brittle, and it provides support for the body. ii. Intestinal epithelial lining ­ ­This epithelium is made of a single layer of columnar epithelial cells (and their associated basal lamina). These cells secrete digestive enzymes, and they play a major role in absorbing nutrients from the lumen (that is, the hollow interior) of the intestinal tract. iii. Blood ­ ­Blood consists primarily of an aqueous salt solution (called plasma) and red blood cells, which play a major role in respiration. In addition, there is a smaller number of cells (called white blood cells) that belong to the immune system. Blood BILD 2, Multicellular Life ­ ­Problem set #1 solutions Page 2 is the transport medium by which respiratory gasses and many other chemical species are moved from one part of the body to other parts of the body. iv. Adipose tissue ­ ­Also called "depot fat." This tissue consists of cells called adipocytes that are specialized to synthesize lipid molecules called triacylglycerols from glycerol and fatty acids. Fat is a highly efficient way to store excess calories acquired from the diet, so depot fat is like having an energy savings account. Adipose tissue also provides thermal insulation and padding that reduces the likelihood of mechanical damag. v. Skeletal muscle ­ ­Skeletal muscles consist primarily of skeletal muscle fibers, and their primary function is to generate force that move body parts with respect to one another and with respect to the surrounding environment. vi. Cardiac muscle ­ ­Cardiac muscle also consists primarily of muscle fibers, but these fibers have properties that are somewhat different from skeletal muscle. Cardiac muscle produces force that generates pressure on the blood, pushing it around the body. 4. a. The central nervous system (CNS ­ ­it's OK to use this abbreviation) consists of the brain and the spinal cord. The peripheral nervous system refers to all of the nervous system that is outside of the CNS, and it consists of nerves (that is, collections of axons) and ganglia (that is, collections of cell bodies). b. The two major cell types in the nervous system are the glial cells (aka "glia") and neurons. The neurons gather, process, and transmit information by way of chemical and electrical signals. Glial cells provide a number of functions that provide support for neurons. c. The three fundamental processes of information flow are: Acquiring information (accomplished by sensory neurons), Processing information (largely accomplished by interneurons; "processing" information means analyzing it, integrating it with other information, and producing an appropriate output signal), and Transmitting the results of processing to effectors (particularly muscles and glands, but not necessarily limited to those tissues). This part of the process is accomplished by motor neurons. d. The three fundamental processes of information flow are: Acquiring information (accomplished at dendrites and in some neurons also at the membrane of the soma) BILD 2, Multicellular Life ­ ­Problem set #1 solutions Page 3 Processing information (accomplished by dendrites, the membrane of the soma, and the spike ­initiating zone of the axon ­ ­why didn't I say "the axon hillock"?), and' Transmitting information (accomplished by the axon and the axon terminals). 5. a. The resting potential (expressed as Vrest) is the staable electrical potential difference that is produced across the plasma membrane as a result of the (typically, but not always) outward diffusion of K+ ions through K+ ion channels, driven by the electrochemical gradient across the membrane. All cells have a resting membrane potential, although the magnitude of Vrest varies among cell types. Next week's solutions will include the answer to "What is an action potential?" etc. ...
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