Muscle Fiber Question

[ThreeMartini]

When the SR release Ca++ to activate the muscle fiber, does the Ca++ bind to troponin or tropomyosin on the thin filament?

Principles of Neural Science. Kandel, Eric. 4th Ed. pp679-681

The text is not clear on this.

Thanks In Advance

[vhawk01]

[ QUOTE ]
When the SR release Ca++ to activate the muscle fiber, does the Ca++ bind to troponin or tropomyosin on the thin filament?

Principles of Neural Science. Kandel, Eric. 4th Ed. pp679-681

The text is not clear on this.

Thanks In Advance

[/ QUOTE ]

Ca++ binds to the C-unit of the troponin, causing a conformational shift that exposes the tropomyosin, which binds the myosin head.

[arahant]

[ QUOTE ]
[ QUOTE ]
When the SR release Ca++ to activate the muscle fiber, does the Ca++ bind to troponin or tropomyosin on the thin filament?

Principles of Neural Science. Kandel, Eric. 4th Ed. pp679-681

The text is not clear on this.

Thanks In Advance

[/ QUOTE ]

Ca++ binds to the C-unit of the troponin, causing a conformational shift that exposes the tropomyosin, which binds the myosin head.

[/ QUOTE ]

please tell me you had to look that up, or are currently a bio major...

[madnak]

Even worse - he's a med student.

[vhawk01]

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
When the SR release Ca++ to activate the muscle fiber, does the Ca++ bind to troponin or tropomyosin on the thin filament?

Principles of Neural Science. Kandel, Eric. 4th Ed. pp679-681

The text is not clear on this.

Thanks In Advance

[/ QUOTE ]

Ca++ binds to the C-unit of the troponin, causing a conformational shift that exposes the tropomyosin, which binds the myosin head.

[/ QUOTE ]

please tell me you had to look that up, or are currently a bio major...

[/ QUOTE ]

/images/graemlins/grin.gif If I had had to look it up, I would have gotten #46 wrong on my last physiology exam.

[ThreeMartini]

[ QUOTE ]
[ QUOTE ]
When the SR release Ca++ to activate the muscle fiber, does the Ca++ bind to troponin or tropomyosin on the thin filament?

Principles of Neural Science. Kandel, Eric. 4th Ed. pp679-681

The text is not clear on this.

Thanks In Advance

[/ QUOTE ]

Ca++ binds to the C-unit of the troponin, causing a conformational shift that exposes the tropomyosin, which binds the myosin head.

[/ QUOTE ]

As I understood it, the tropomyosin underwent the conformational change (via Ca++) exposing binding sites on the ACTIN, with which the myosin heads attached.

I'm still unclear as to whether the myosin heads attach to actin or the tropomyosin.

[vhawk01]

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
When the SR release Ca++ to activate the muscle fiber, does the Ca++ bind to troponin or tropomyosin on the thin filament?

Principles of Neural Science. Kandel, Eric. 4th Ed. pp679-681

The text is not clear on this.

Thanks In Advance

[/ QUOTE ]

Ca++ binds to the C-unit of the troponin, causing a conformational shift that exposes the tropomyosin, which binds the myosin head.

[/ QUOTE ]

As I understood it, the tropomyosin underwent the conformational change (via Ca++) exposing binding sites on the ACTIN, with which the myosin heads attached.

I'm still unclear as to whether the myosin heads attach to actin or the tropomyosin.

[/ QUOTE ]

Yep, you are right, I misspoke slightly. The calcium binds to the C unit of the troponin, as I said, which causes a conformational shift in the troponin molecule. This shift pulls the tropomyosin down deeper into the groove on the actin, exposing the active sight.

The myosin binds to the actin. Sorry for being wrong.

FWIW, my Guyton text says the mechanism isn't 100% known, and this is just the most popular suggestion.

[SitNHit]

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
When the SR release Ca++ to activate the muscle fiber, does the Ca++ bind to troponin or tropomyosin on the thin filament?

Principles of Neural Science. Kandel, Eric. 4th Ed. pp679-681

The text is not clear on this.

Thanks In Advance

[/ QUOTE ]

Ca++ binds to the C-unit of the troponin, causing a conformational shift that exposes the tropomyosin, which binds the myosin head.

[/ QUOTE ]

please tell me you had to look that up, or are currently a bio major...

[/ QUOTE ]

/images/graemlins/grin.gif If I had had to look it up, I would have gotten #46 wrong on my last physiology exam.

[/ QUOTE ]

Things are now becoming clear to me hawk about ya. /images/graemlins/grin.gif

[vhawk01]

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
When the SR release Ca++ to activate the muscle fiber, does the Ca++ bind to troponin or tropomyosin on the thin filament?

Principles of Neural Science. Kandel, Eric. 4th Ed. pp679-681

The text is not clear on this.

Thanks In Advance

[/ QUOTE ]

Ca++ binds to the C-unit of the troponin, causing a conformational shift that exposes the tropomyosin, which binds the myosin head.

[/ QUOTE ]

please tell me you had to look that up, or are currently a bio major...

[/ QUOTE ]

/images/graemlins/grin.gif If I had had to look it up, I would have gotten #46 wrong on my last physiology exam.

[/ QUOTE ]

Things are now becoming clear to me hawk about ya. /images/graemlins/grin.gif

[/ QUOTE ]


Hey, I still got the question right. It just asked me where the Ca++ binds to! /images/graemlins/grin.gif

[ThreeMartini]

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
When the SR release Ca++ to activate the muscle fiber, does the Ca++ bind to troponin or tropomyosin on the thin filament?

Principles of Neural Science. Kandel, Eric. 4th Ed. pp679-681

The text is not clear on this.

Thanks In Advance

[/ QUOTE ]

Ca++ binds to the C-unit of the troponin, causing a conformational shift that exposes the tropomyosin, which binds the myosin head.

[/ QUOTE ]

As I understood it, the tropomyosin underwent the conformational change (via Ca++) exposing binding sites on the ACTIN, with which the myosin heads attached.

I'm still unclear as to whether the myosin heads attach to actin or the tropomyosin.

[/ QUOTE ]

Yep, you are right, I misspoke slightly. The calcium binds to the C unit of the troponin, as I said, which causes a conformational shift in the troponin molecule. This shift pulls the tropomyosin down deeper into the groove on the actin, exposing the active sight.

The myosin binds to the actin. Sorry for being wrong.

FWIW, my Guyton text says the mechanism isn't 100% known, and this is just the most popular suggestion.

[/ QUOTE ]

I think Kandel says something similar..along the lines of...'for reasons that are not fully yet understood'...A none to uncommon phrase in these types of texts.

[vhawk01]

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
When the SR release Ca++ to activate the muscle fiber, does the Ca++ bind to troponin or tropomyosin on the thin filament?

Principles of Neural Science. Kandel, Eric. 4th Ed. pp679-681

The text is not clear on this.

Thanks In Advance

[/ QUOTE ]

Ca++ binds to the C-unit of the troponin, causing a conformational shift that exposes the tropomyosin, which binds the myosin head.

[/ QUOTE ]

As I understood it, the tropomyosin underwent the conformational change (via Ca++) exposing binding sites on the ACTIN, with which the myosin heads attached.

I'm still unclear as to whether the myosin heads attach to actin or the tropomyosin.

[/ QUOTE ]

Yep, you are right, I misspoke slightly. The calcium binds to the C unit of the troponin, as I said, which causes a conformational shift in the troponin molecule. This shift pulls the tropomyosin down deeper into the groove on the actin, exposing the active sight.

The myosin binds to the actin. Sorry for being wrong.

FWIW, my Guyton text says the mechanism isn't 100% known, and this is just the most popular suggestion.

[/ QUOTE ]

I think Kandel says something similar..along the lines of...'for reasons that are not fully yet understood'...A none to uncommon phrase in these types of texts.

[/ QUOTE ]

I don't know about that. Its less common in physiology than it is in, say, biochemistry or genetics, but its not that rare. Exact mechanisms are found for the things that cause disorders first, and I don't know of any disorder in the binding of calcium to the troponin-tropomyosin complex. The problems with muscle contraction usually revolve around a lack of glycolysis or oxidative respiration in cells, a lack or excess of calcium ions, membrane depolarization, that sort of thing. Even the building of actin and myosin filaments seems to be pretty errorproof, at least compared to, say, collagen fibrils.