Biology 2382B Lecture Notes - Lecture 15: Sarcolemma, Stress Fiber, Leading Edge

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rosewolf498

14 Mar 2017

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Recap: in skeletal muscle there"s a structure called sarcomere, involved in contraction (cid:523)myosin binding to actin(cid:524) Atp binds to myosin, it lets go of actin, moves to + end, with release of adp+pi there"s a power stroke. Thick filaments of myosin ii sit between the z disks and bring them together during contraction. Myosin/actin binding is regulated by calcium: calcium comes from sarcoplasmic reticulum (variation of endoplasmic reticulum) Calcium needs to be separate from phosphate: calcium and phosphate make a mineral (bone, thus little calcium in the cytoplasm. Calcium is tightly regulated by being bound in the sarcoplasmic reticulum. Transverse tubules come from plasma membrane (sarcolemma) and go deep into the cell where it contacts sarcoplasmic reticulum. In the sarcoplasmic reticulum there"s calcium stores: don"t want continuous muscle contraction. Nerve depolarization causes change in membrane potential which reaches the transverse (t) tubules. T tubule passes it to sarcoplasmic reticulum and triggers release of calcium.

Related Questions

The vesicles that transport materials from donor membranes to acceptor membranes include:

	1.	COP-II coated vesicles
	2.	COP-III coated vesicles
	3.	COP-I coated vesicles
	4.	Clathrin coated vesicles

2.5 points

QUESTION 11

During skeletal muscle contraction, the roles of ATP include:

	1.	ATP is not required for forming the crossbridges between myosin and actin filaments.
	2.	ATP is utilized as a structural linker to mediate the interaction between myosin and actin filaments
	3.	Hydrolysis of ATP provides energy for myosin head to move along actin filaments and the binding of ATP to myosin head allows the detachment of myosin fromactin filaments.
	4.	ATP binds to actin filaments to drive the power stroke of myosin head.

2.5 points

QUESTION 12

One of the functions of smooth endoplasmic reticulum is

	1.	Synthesizing steroid hormone in the endocrine cells of the gonad and adrenal cortex
	2.	Serves as the starting point of the biosynthetic pathway
	3.	Synthesizing secretory proteins
	4.	Degrading cell debris

2.5 points

QUESTION 13

The function of COP-II coated vesicles is mainly:

	1.	Transporting materials from endosomes to Golgi complex
	2.	Moving materials from the ER to the ERGIC and Golgi complex.
	3.	Transporting materials from Golgi complex back to endoplasmic reticulum.
	4.	Involved in receptor-mediated endocytosis.

2.5 points

QUESTION 14

Which of the following processes is completed in rough endoplasmic reticulum?

	1.	Chaperones help misfolded proteins fold correctly.
	2.	Proteins that target to nucleus are synthesized in rough endoplasmic reticulum.
	3.	O-linked glycosylation occurs in rough endoplasmic reticulum.
	4.	Misfolded proteins are destructed in rough endoplamic reticulum.

2.5 points

QUESTION 15

Kinesin is the motor protein that coorporates with microtubules. It has the following functions:

	1.	It uses GTP as energy source.
	2.	It can hydrolyze ATP and use the energy to drive cargo along microtubules from minus end to plus end.
	3.	It has a globular head that can act as GTPase
	4.	The tail of kinesin is more diverse and binds to cargo

2.5 points

QUESTION 16

For correct segregation and trafficking, lysosomal proteins are tagged in the cis-Golgi with phosphorylated mannose residues, and then the tagged lysosomal enzymes are recruited to clathrin coated vesicles by mannose 6-phosphate receptors.

True

False

2.5 points

QUESTION 17

The process that specialized cells, such macrophages, engulf relatively large particles is:

	1.	Called pinocytosis
	2.	Called phagocytosis
	3.	Mediated by COP-II coated vesicles
	4.	Called autophagy

2.5 points

QUESTION 18

Proteins synthesized on rough endoplasmic reticulum and smooth endoplasmic reticulum are imported co-translationally to their destinations

True

False

2.5 points

QUESTION 19

Treatment of cells with a drug that promotes microtubule disassembly disperses Golgi complex into separate stacks of membrane compartments, suggesting that:

	1.	Golgi complex is made of microtubules.
	2.	Microtubules are important for the organization of Golgi complex.
	3.	Microtubules are transported into Golgi complex
	4.	Golgi complex is composed of tubulin proteins

2.5 points

QUESTION 20

Which of the following is correct about signal sequence of a secretory protein?

	1.	It is an âaddress codesâ for protein trafficking pathways
	2.	It is usually located at the C-terminus.
	3.	It targets the ribosome and the protein that is being synthesized to endoplasmic reticulum.
	4.	It is removed in Golgi complex.

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Biology 2382B Lecture Notes - Lecture 15: Sarcolemma, Stress Fiber, Leading Edge

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