BIPN 100 Lecture Notes - Lecture 20: Caldesmon, Myosin Light-Chain Kinase, Skeletal Muscle

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silvercod749

11 Jun 2017

School

UCSD

Department

Biology/Animal Physiol & Neurosc

Course

BIPN 100

Professor

James Edward Cooke

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Document Summary

The reason why smooth muscles don"t have striated muscles is because there"s actin and myosin but they are not organized into sarcomeres. They still slide over each other there just no organization into neat lines. Onset of contractions are very slow and the contractions last a very long time. If it takes a while to start and eventually stop this can lead us to conclude that smooth muscle have type 1 fibers or slow fibers. And because of this it means atpase is very slow. The actin and myosin are arranged differently than skeletal muscle cells. Instead of sarcomere we have thin filament attached to the cell membrane with dense bodies that anchor the thin filament on different portions of the cell membrane. We also have thick filaments in the middle of the cell. When muscle cells are relaxed there aren"t any cross bridges forming. Shortening is in 3d and the whole muscle caves in on itself.

Related Questions

1. Each muscle fiber is a bundle of myofibrils. Eachmyofibril is a series of sarcomeres. Thus, a muscle fiber contractswhen each sarcomere within a series contracts simultaneously. Suchcoincidence is mirrored by each myobril within the muscle fiber.What enables the extent to which molecular motors contractsimultaneously within an innervated muscle fiber?

a. the frequency of acetylcholine secretion within theneuromuscular synapse

b. the frequency of Ca²⁺ oscillations within themuscle fiber

2. A living muscle fiber experiences dynamic frequencies ofCa²⁺ oscillations. In effect, Ca²⁺ acts as asecond messenger when it disperses throughout the fluid-filledspaces between actin and myosin filaments. What is the source ofthis second message?

a. extracellular fluid b.sarcoplasmic reticulum

3. Why might a muscle fiber need an ample amount ofNa⁺,K⁺-ATPase on itssurface?

a. as evident by the value of the cellâs membrane potential,muscle fibers are leaky to Na⁺

b. to counter the effect of numerous action potentials persecond

4. Assume that you could âseeâ nicotinic acetylcholine receptorswithin the musculature. How would they be arranged spatially?

a. evenly distributed on the cellâs surface like voltage-gatedNa⁺ and K⁺ channels

b. in dense arrays within the motor end plate

5. Assume that you could âseeâ neurosecretion fromÎ±-motor neurons within the musculature of an animal standing still.What would this âlookâ like?

a. uniform, baseline secretion throughout the musculature

b. enhanced acetylcholine secretion within antigravity muscles,baseline secretion elsewhere

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QUESTION 30

The function of centrosome is:

	1.	Microtubule initiation and organization in animal cells
	2.	Organization of thin filaments
	3.	Depolymerization of microtubules
	4.	Organization of intermediate filaments

2.5 points

QUESTION 31

The destinations of proteins synthesized on "free" ribomsomes include:

	1.	Endoplasmic reticulum
	2.	Nucleus
	3.	Mitochondria
	4.	Lysosomes

2.5 points

QUESTION 32

Microtubules can be assembled and disassembled quickly in response to the cellular changes is because:

	1.	Cells synthesize tubulin proteins very fast.
	2.	Cells can turn other cytoskeletal filaments into microtubules
	3.	Microtubules have an instable plus end and microtubules are probably organized by weak non-covalent interactions
	4.	The motor proteins of microtubules can organize the microtubules in response to the cellular changes

2.5 points

QUESTION 33

Both signal recognition particle and a translocon in rough endoplasmic reticulum membrane can recognize and bind to the signal sequence of a secretory protein, so they play the exact same role during protein co-translational translocation.

True

False

2.5 points

QUESTION 34

Rough endoplasmic reticulum is so named is because:

	1.	It has many proteins associated with its surface.
	2.	It has ribosomes associated with its cytosolic surface.
	3.	It is associated with nuclear membrane.
	4.	It has vesicles budding off its surface.

2.5 points

QUESTION 35

The membrane vesicles that transport materials between membrane compartments have a protein coat. The protein coat has similar functions in different vesicles. These functions include:

	1.	Help the enclosed material fold correctly.
	2.	Help degrade the protein in the vesicles
	3.	Maintain the internal pH of the vesicles
	4.	Function as mechanical device to form a vesicle and select the components to be carried by a vesicle.

2.5 points

QUESTION 36

Lysosomes are important for:

	1.	Receptor-mediated endocytosis.
	2.	Breaking down foreign particles brought into the cells by endosomes
	3.	Regulating the process of organelle turnover.
	4.	Protein trafficking between membrane compartments

2.5 points

QUESTION 37

Which of the following is correct about membrane biosynthesis?

	1.	Membranes are synthesized in Golgi Complex.
	2.	Membranes arise from preexisting endoplasmic reticulum membranes.
	3.	Membranes are synthesized on ribosomes.
	4.	Membranes of all organelles have the same composition of proteins and lipids, since they all originate from endoplasmic reticulum.

2.5 points

QUESTION 38

During skeletal muscle contractions, the shortening of the muscle fibers is because of:

		The shortening of the thin and thick myofilaments.
		The shortening of the cytoskeletal filaments.
		The kinesin proteins moving over microtubules.
		The actin and myosin filaments sliding over each other.

2.5 points

QUESTION 39

The assembly and disassembly of microtubules is regulated by rate of growth and shrinkage of the plus end.

True

False

2.5 points

QUESTION 40

The functions of Golgi complex include:

	1.	O-linked oligosaccharides and most of a cellâs complex polysaccharides are assembled in Golgi complex
	2.	Cis Golgi complex sorts proteins
	3.	Trans Golgi complex segregates proteins in different types of vesicles for dilevery.
	4.	N-linked oligosaccharides are further processed in Golgi complex

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BIPN 100 Lecture Notes - Lecture 20: Caldesmon, Myosin Light-Chain Kinase, Skeletal Muscle

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