Myofibrils and Sarcomeres

Transcription

1 Myofibrils and Sarcomeres Purpose: To compare the size of electron micrographs of skeletal muscle fibers to given size information. Background: 1 muscle fiber can be up to cm in length 1 muscle fiber can have a diameter of between 10 m and 100 m. 1 millimeter (mm) is equal to 1000 micrometers (m) 1 actin molecule is angstroms in diameter 1 myosin molecule is 100 angstroms in diameter 1 angstrom is equal to 1.00 x meters You can convert magnified images by dividing the size measured in mm with a ruler by the magnification You can find the actual number of very small things by multiplying the number counted at magnification by the amount of magnification 1. Calculate the actual length of one sarcomere using the 1800x pictograph in units of millimeters and then in micrometers. Show your work.

2 2. Calculate the actual length of one sarcomere using the 7200x pictograph in units of millimeters and then in micrometers. Show your work. 3. Compare your answers from #1 and #2. Describe which one is more accurate. 4. Calculate the actual diameter of one muscle fiber using the 1800x pictograph in units of micrometers. Does its calculated size fall within the range of given data? Show your work and explain your answer. 5. Calculate the actual number of sarcomeres, in 1.00 cm of myofibril. Describe which micrograph you re getting your information from and show your work.

3 6. Using the pictographs given, count the number of myofibrils in one muscle fiber at 7200x magnification. 7. Calculate the number of sarcomeres, in 1.00 cm of muscle fiber. Describe where you are getting your information from and show your work. 8. If a sartorius muscle is 1.00 meter long, has 100 muscle fibers per bundle and ten muscle bundles total, how many sarcomeres are there in this muscle. Describe where you are getting your information from and show your work.

4 Myofibrils and Sarcomeres Key 1. Calculate the actual length of one sarcomere using the 1800x pictograph in units of millimeters and then in micrometers. Show your work. 1 sarcomere is 4mm = 4000μm so the actual size is 4000/1800 = 2.2μm 2. Calculate the actual length of one sarcomere using the 7200x pictograph in units of millimeters and then in micrometers. Show your work. 1 sarcomere is 12 mm = 12, 000μm so 12, 000/7200 = 1.7μm 3. Compare your answers from #1 and #2. Describe which one is more accurate. 4. Calculate the actual diameter of one muscle fiber using the 1800x pictograph in units of micrometers. Does its calculated size fall within the range of given data? Show your work and explain your answer. T he diameter is 35 mm = 35, 000μm so 35, 000/1800 = 19.44μm which falls within μm 5. Calculate the actual number of sarcomeres, in 1.00 cm of myofibril. Describe which micrograph you re getting your information from and show your work. 6. Using the pictographs given, count the number of myofibrils in one muscle fiber at 7200x magnification. 7. Calculate the number of sarcomeres, in 1.00 cm of muscle fiber. Describe where you are getting your information from and show your work. *This question does not take into consideration that muscle fibers are actually round

5 8. If a sartorius muscle is 1.00 meter long, has 100 muscle fibers per bundle and ten muscle bundles total, how many sarcomeres are there in this muscle. Describe where you are getting your information from and show your work. 300,000 sarcomere 100 fibers e xample : 300, 000 x100 cmx x 10 1 cm fiber 1m 1 bundle 1 sartorius bundles 10 = ~ 3x10 sarcomeres in one sartorius muscle

6 Rubric 1 2 Calculate actual length of one sarcomere 4.0 Length is correctly calculated in mm and micrometers showing work and including proper units 3.5 Length is correctly calculated in mm and micrometers showing work 2.5 Length is correctly calculated in mm and micrometers not showing work 1.5 an attempt to calculate length is made but is incomplete or incorrect 3 compare accuracy of 1 and Description of which on is more accurate is clear and complete 3.5 Description of which on is more accurate is complete 2.5 Description of which on is more accurate is complete but somewhat unclear 4 Calculate the diameter of one muscle fiber 4.0 Length is correctly calculated in mm and micrometers showing work and including proper units 3.5 Length is correctly calculated in mm and micrometers showing work 2.5 Length is correctly calculated in mm and micrometers not showing work 1.5 an attempt to calculate length is made but is incomplete or incorrect 5. Number of sarcomeres in 1 cm myofibril 4.0 width is converted to mm and multiplied by magnification with work shown 3.5 width is converted to mm and multiplied by magnification 2.5 length is multiplied by magnification but answer is off by a factor of length is multiplied by magnification but answer is off by a factor of Count number of myofibrils in 1 fiber 4.0 counted number is between myofibrils 3.5 counted number is lower than 25 or higher than totally didn't count correctly 1.5 were you looking at the correct image? 7 Calculate number of sarcomeres in 1 cm muscle fiber 4.0 answer is between 200,000 and 350,000 showing work and describing where info is from 3.5 answer is between 200,000 and 350,000 showing work but doesn't describe where info is from 2.5 answer is between 200,000 and 350,000 not showing work but describes where info is from 1.5 answer is not between 200,000 and 350,000 not showing work poor description where info is from

7 8 Calculate number of sarcomeres in 1 m of muscle 4.0 answer is ~1 x10^10 showing work and describing where info is from 3.5 answer is ~1 x10^10 showing work but doesn't describe where info is from 2.5 answer is ~1 x10^10 not showing work but describes where info is from 1.5 answer is not ~1 x10^10 not showing work poor description where info is from