1. 09_10 Sliding filament theory Slide number: 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Tropomyosin Troponin complex Actin monomers Actin filament Myosin filament ADP + P

2. 09_10 Sliding filament theory Slide number: 2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Tropomyosin Troponin complex Actin monomers Actin filament Myosin filament Ca +2 Muscle contraction Release of Ca +2 from sarcoplasmic reticulum exposes binding sites on thin filament: Ca +2 binds to troponin complex Tropomyosin pulled aside Binding sites on actin filament exposed 1Exposed binding sites on actin allow the muscle contraction cycle to occur Ca +2 ADP + P

3. 09_10 Sliding filament theory Slide number: 3 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2Cross-bridge binds actin to myosin ADP + P Contraction cycle

4. 09_10 Sliding filament theory Slide number: 4 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3Cross-bridge pulls actin filament (power stroke), ADP and P released from myosin ADP + P Contraction cycle

5. 09_10 Sliding filament theory Slide number: 5 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ATP 4New ATP binds to myosin, causing linkage to release

6. 09_10 Sliding filament theory Slide number: 6 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 5ATP splits, which provides power to “cock” the myosin cross-bridge ADP + P Contraction cycle

7. 09_10 Sliding filament theory Slide number: 7 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ADP + P Contraction cycle

8. 09_10 Sliding filament theory Slide number: 8 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ca +2 ATP Active transport of Ca +2 into sarcoplasmic reticulum, which requires ATP, makes myosin binding sites unavailable. Muscle relaxation ADP + P

9. 09_10 Sliding filament theory Slide number: 9 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1Exposed binding sites on actin allow the muscle contraction cycle to occur Ca +2 ADP + P Contraction cycle 2Cross-bridge binds actin to myosin ADP + P P P ADP 3 ADP + P Cross-bridge pulls actin filament (power stroke), ADP and P released from myosin ATP 4New ATP binds to myosin, causing linkage to release ADP + P 5ATP splits, which provides power to “cock” the myosin cross-bridge

10. 09_10 Sliding filament theory Slide number: 10 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Tropomyosin Troponin complex Actin monomers Actin filament Myosin filament ADP + P Ca +2 Muscle contraction Release of Ca +2 from sarcoplasmic reticulum exposes binding sites on thin filament: Ca +2 binds to troponin complex Tropomyosin pulled aside Binding sites on actin filament exposed 1 Ca +2 ADP + P Ca +2 ATP Active transport of Ca +2 into sarcoplasmic reticulum, which requires ATP, makes myosin binding sites unavailable. Muscle relaxation