Biology 152 1st Edition Lecture 13Outline of Last LectureI.Types of Skeletons a.Hydrostatic Skeletons b.Exoskeletons c.Endoskeletons II. Muscle Cell StructureIII. Sliding Filament ModelOutline of Current LectureIV. Initiating Muscle ContractionV. Respiration and Circulation a. Partial Pressure and Diffusion b. Gas ExchangeCurrent LectureInitiating Muscle Contraction**Clicker Question**Loss of function mutations in the protein would lead to what sort of problems?A. There’d be no way to transfer force of the myofibril to the muscle fiber membrane B. The z-lines wouldn’t move towards one another C. The link between the muscle fiber and the skeleton would be impaired D. ATP hydrolysis would be impaired • z lines are the myosin and actin lines, and dystrophan has nothing to do with this interaction • you’re seeing the link between the actin and the sarcolemma (protein directly to the membrane) — the point that wouldn’t be connected would be the sarcomere, and the myofibril, the skeleton is not involved • A is correct sarcomere is one unit of z-lines made of myosin and actin• Muscle excitation—contraction coupling These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.• a nerve cell sends the signal to the muscle • this is propagated to the sarcoplasmic reticulum which releases calcium into the cell • calcium binds to troponin which pulls tropomyosin away from the actin. (holds onto actin and moves it out of the way) Actin can bind, and as long as there is ATP around you can have a cycle of contractions • many proteins that bind to calcium change their shape, kept at low levels so a small amount of calcium can have a large effect • in each different type of muscle cell will be a different variant of tropomyosin **Clicker Question**Rattlesnakes contract their tail shaker muscles at frequencies up to 80 Hz. They move body muscles more slowly. What contractile differences do you expect to find in the tail shaker muscles that result in their high contraction rate?A. other proteins, not actin and myosin, probably form the bulk of the muscle B. Less sarcoplasmic reticulum, which will increase the speed of calcium release C. Calcium probably binds directly to tropomyosin feather than troponin D. Myosin molecules will have a high rate of ATP hydrolysis,which allows for a faster rate of cross-bridge cycling E. There is probably no structural difference between the shaker and slithering muscles, only a physiological difference • if more ATP, it will work faster, and the muscles will contract more quickly • E is okay, but because D actually explains it, then it is a better response TAKE HOMES*do not need to memorize the steps of how myosin and actin interactRespiration CirculationPartial Pressure and Diffusion**Clicker Question**Sponges, cnidarians, and flatworms lack a specialized gas exchange surface. This is not a disadvantage to them because:A. They are too large for a circulatory system to operate well. B. They live without need for oxygen C. They do not produce carbon dioxide D. Countercurrent exchange mechanisms cannot function well in their living environment E. Nearly all of their cells are in direct contact with their external environment • Answer = E • Flatworm picture — they have both male and female body parts• reproduction: they fight over who gets to be the male (female is the loser) because incubating the eggs is a huge energy cost, so throne who does this has a disadvantage and maynot live as long Partial Pressure and Diffusion• diffusion of gases works like the diffusion of solutes • gases go from high concentration to low, but you figure out the concentration using “partial pressure” • the sum of the partial pressures of a mixture of gases equals the total atmospheric pressure **Clicker Question**When the air in a testing chamber is specially mixed so that its oxygen content is 10% and its overall air pressure is 400 mmHg, then partial pressure of O2 = ?40 mmHg*getting down to cellular level, need to get gases from one compartment into anotherWhat should happen in this situation?C. O2 should leave the blood and go into the alveolar space, and the CO2 should go into the blood from the alveolar space• getting oxygen into cells relies on diffusion • gas goes from where its own partial pressure is higher to where its own partial pressure is lower **Clicker Question**This flatworm relies only on diffusion. Compare the partial pressure of CO2 and O2 in cells A andB so that the organism can existA. Cell A should have higher pCO2 but lower O2 than cell B B. Cell A should have higher pCO2 and )w than cell B C. Cell A should have lower pCO2 and O2 than cell B D. Cell A should have a • if A was right, CO2 would go into the organism, which would be bad (want CO2 to be lower in A and the O2 higher) • so E = the right answer • as you go deeper into organism O2 concentration goes down, so those cells will rely more on diffusion for getting oxygen limitation is good for the organism (bad for cancer cells for example) TAKE HOMESGas Exchange4 different kinds4 part system for respiration and circulation Respiration step:• ventilation = bulk flow, or movement of a gas or a liquid using pressure• in case of mammal, using diaphragm, using negative pressure and drawing air into the lungs • diffusion = gases move from the lung into the capillaries • Circulation step: • bulk flow — in a mammal, bulk flow gets positive pressure from the heart • diffusion — gases move from circulation into the cells • pressure and concentration of the gases in the medium organisms lives in will affect the way an organism extracts those gases in water, the concentration of oxygen in air at sea level is much higher than in water• fish must deal with this somehow so they can feed their mitochondria and live • So which kind of current exchange system would give fish the most advantage given the concentration of oxygen in the water viscosity • Answer = countercurrent • countercurrent is the way the whales keep their tongues cold and not allowing heat to escape into water • its effective because when you run two gas or water by each other, you get a really good exchange efficiency —would give the fish really good exchange of oxygen • fish open mouth, bring in water and pump it across the gills — the
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