Question

In: Biology

1. Which of the following is true about muscle protein? A. In a contracting muscle cell,...

1. Which of the following is true about muscle protein?

A. In a contracting muscle cell, troponin binds to calcium, and tropomyosin changes conformation and uncovers the myosin binding sites on actin

B. In a relaxed muscle cell, tropomyosin binds to calcium, and troponin covers the myosin binding sites on actin

C. In a contracting muscle cell, tropomyosin binds to calcium, and troponin changes conformation and uncovers the myosin binding sites on actin.

D. In a relaxed muscle cell, troponin binds to calcium, and tropomyosin covers the myosin binding sites on actin

2.

Which of the following represents the CORRECT order of events in the muscle cell when I decide that I want to wiggle my pinkie toe?

A. The influx of positive charge causes the opening of ligand-gated sodium channels causing an action potential that propagates down the sarcoplasmic reticulum membrane which causes the release of calcium from the T-tubules.

B. The influx of positive charge causes the opening of voltage-gated sodium channels causing an action potential that propagates down the T-tubule leading to the release of calcium from the sarcoplasmic reticulum

C. The influx of positive charge causes the opening of ligand-gated sodium channels causing an action potential that propagates down the T-tubule leading to the release of calcium from the sarcoplasmic reticulum

D. The influx of positive charge causes the opening of voltage-gated sodium channels causing an action potential that propagates down the sarcoplasmic reticulum membrane which causes the release of calcium from the T-tubules.

Expert Solution

Ans 1: Correct option (A) In a contracting muscle cell, troponin binds to calcium, and tropomyosin changes conformation and uncovers the myosin-binding sites on actin

Explanation: Muscle sarcomere is made up of thick and thin filaments. Thick filaments are made up of myosin protein whereas thin filaments are made up of actin protein. Two regulatory proteins named troponin and tropomyosin are present on the actin filament.

High Ca++ ion concentration cause muscle contraction. The following are the sequences during the muscle contraction.

Binding of Ca++ ion on troponin
Conformational change in tropomyosin
The site where myosin head binds to the actin is exposed
Myosin head binds to the actin filament and actin filament is pulled cause muscle contraction
ATP is hydrolyzed in this process and provide energy for the contraction

Incorrect options:

(B) In a relaxed muscle cell, tropomyosin binds to calcium, and troponin covers the myosin-binding sites on actin

Explanation: In relaxed muscle tropomyosin (not troponin) covers the myosin-binding site on actin and troponin, (not tropomyosin) binds to calcium ion.

(C) In a contracting muscle cell, tropomyosin binds to calcium, and troponin changes conformation and uncovers the myosin-binding sites on actin.

Explanation: In contracting muscle cell troponin (not tropomyosin) binds to calcium, and tropomyosin (not troponin) changes conformation to expose the myosin binding site.

(D) In a relaxed muscle cell, troponin binds to calcium, and tropomyosin covers the myosin-binding sites on actin

Explanation: In a relaxed muscle calcium does not bind with troponin but myosin-binding sites on the actin filament are covered by tropomyosin.

Ans 2: Correct option(B) The influx of positive charge causes the opening of voltage-gated sodium channels causing an action potential that propagates down the T-tubule leading to the release of calcium from the sarcoplasmic reticulum

Explanation: At the neuromuscular junction, the axon terminal of the neuron is very close to the muscle cell. The synaptic cleft is present between the muscle fiber and the axon terminal.

After receiving the nerve impulse at the axon terminal it causes the release of the neurotransmitters that is acetylcholine in the synaptic cleft.

These neurotransmitters then bind to the receptors that are present on the muscle fiber. This will cause the opening of the sodium ion channel. More sodium ions enter the muscle cell and comparatively fewer potassium ions are released. Thus the potential difference is maintained across the membrane. This will cause the opening of the voltage-gated sodium ion channel.

The action potential is generated that will travel down the T-tubule and cause the release of the calcium ions that are stored in the sarcoplasmic reticulum.

Incorrect options: (A) The influx of positive charge causes the opening of ligand-gated sodium channels causing an action potential that propagates down the sarcoplasmic reticulum membrane which causes the release of calcium from the T-tubules.

Explanation: The channels that open due to the influx of positive charge are voltage-gated and not ligand-gated.

The action potential travels down the T-tubule and calcium ions are released from the sarcoplasmic reticulum.

(C) The influx of positive charge causes the opening of ligand-gated sodium channels causing an action potential that propagates down the T-tubule leading to the release of calcium from the sarcoplasmic reticulum

Explanation: The channel is voltage-gated, not ligand-gated.

(D) The influx of positive charge causes the opening of voltage-gated sodium channels causing an action potential that propagates down the sarcoplasmic reticulum membrane which causes the release of calcium from the T-tubules.

Explanation: The action potential travels down the T-tubule (not through the sarcoplasmic reticulum) and causes the release of calcium ions from the sarcoplasmic reticulum (not from T-tubules).

gladiator answered 1 year ago

21 Which of the following statements about the cell cycle is TRUE? a. A cell has...

21 Which of the following statements about the cell cycle is TRUE? a. A cell has more DNA during G1 than it does in G2 b. Cytokinesis is the phase of the cell cycle where DNA is replicated. c. Cells in the G0 state are actively dividing. d. Normal cells do not enter S phase unless there are sufficient nutrients and resources to complete an entire cell cycle. 23 Cancers that arise due to proto-oncogenes turning into oncogenes require that:...

1. Which of the following statements is NOT true about cell size? Larger cells require more...

1. Which of the following statements is NOT true about cell size? Larger cells require more materials to survive. Material needs are tied to Volume. Maximum cell size is limited by the surface area to volume ratio When cell volume is doubled, the surface area is also doubled. As a cell increases in size, the volume increases faster than its surface area The amount of surface area of a cell determines how much material can be absorbed through the membrane...

1.Which is true about sickle-cell anemia? Choose all that are true. The allele that causes the...

1.Which is true about sickle-cell anemia? Choose all that are true. The allele that causes the disease is recessive. Natural selection favors the heterozygote in areas with malaria. The mutation that causes it is a SNP. People homozygous for the sickling allele experience episodes of severe pain that may permanently damage their vital organs. 2.What was probably a selective pressure against dark skin in the our earliest ancestors to leave Africa? Spina bifida from excessive ultraviolet light. Rickets from a...

Questions 1. Which of the following is true for the omega angle in the protein backbone?...

Questions 1. Which of the following is true for the omega angle in the protein backbone? a. it equals 180 degrees. b. the orientation of the bonds around the peptide bonds is Cis. c. it may have any value between 0 to 180. d. the most common values of omega angel are 60 to 120. 2. Which of the following can not apply to heat shock protein? a. They are proteins found only in eukaryotes. b. They form complexes with...

Which of the following is true about fringe benefits? Which of the following is true about...

Which of the following is true about fringe benefits? Which of the following is true about fringe benefits? They represent additional compensation given for services performed They are only available for employees. The amount of the fringe benefit is never subject to income tax. They represent additional cash paid directly to employees.

which of the following about eukaryotic flagella/cilia is NOT true? a. cell membrane covering the outside...

which of the following about eukaryotic flagella/cilia is NOT true? a. cell membrane covering the outside of the flagella b. 9+2 arrangement of microtuble c. A cylinder basal body with a rotating filament d. some eukaryotic flagella are adapted for sensory functions e. about 10 times thicker than bacteria flagella

During the excitation phase of the skeletal muscle cell contraction, the following occurs: 1) the muscle...

During the excitation phase of the skeletal muscle cell contraction, the following occurs: 1) the muscle fiber develops tension and shortens 2) the muscle fiber relaxes and returns to its original length 3) nerve action potentials lead to muscle action potentials A growing long bone in a child has only two types of cartilage at the epiphysis. These two areas are 1) elastic cartilage and epiphyseal plate 2) epiphyseal plate and epiphyseal line 3) primary and secondary ossification centers 4)...

1. Which of the following statements are true regarding muscle glycogen. There are multiple correct answers....

1. Which of the following statements are true regarding muscle glycogen. There are multiple correct answers. If exercise is not to be repeated within 12 hours, then glycogen restoration does not have to be immediately following exercise The most rapid repletion of glycogen following exercise occurs in the first few hours post exercise. Consuming some protein along with carbohydrate during immediate recovery from exercise is beneficial. Higher glycemic index foods enhance glycogen restoration following exercise It is best to always...

Which of the following is NOT true of the relaxation of a muscle fiber? Multiple Choice...

Which of the following is NOT true of the relaxation of a muscle fiber? Multiple Choice calcium release channels open allowing Ca to leave SR ATP is needed to fuel the calcium ATPase pumping Ca into SR Ca2+ moves from the sarcoplasm into the sarcoplasmic reticulum (SR) Action potentials must cease

Which statement is NOT true about the repressor protein, in regard to the lac operon: Group...

Which statement is NOT true about the repressor protein, in regard to the lac operon: Group of answer choices it blocks transcription when it is bound to the operator is only expressed when glucose is present it changes its three-dimensional shape (conformation) when it is bound to the inducer, allolactose All listed ARE true about the repressor binds to the operator region of the lac operon when glucose is being utilized