Brain size has increased nearly 3x in 4 million years.
Answer:
<u>Option- D: </u>Is the best choice to choose from the given options.
Now, let us explain the term Cell cycle in a more comprehensive way.
<u>As the cell cycle is controlled at three checkpoints.</u>
- The integrity of the DNA is assessed at the G₁ checkpoint.
- Proper chromosome duplication is assessed at the G₂ checkpoint.
- Attachment of each kinetochore to a spindle fiber is assessed at the M checkpoint.
Explanation:
The cell cycle is controlled by three internal checkpoints that evaluate the condition of the genetic information.
- <u>The G₁ Checkpoint</u>:This stage determines whether all conditions are favorable for cell division to proceed. The cell can halt the cycle and attempt to remedy the problematic condition, or the cell can advance into G₀ (inactive) phase and await further signals when conditions improve.
- <u>The G₂ Checkpoint:</u> The most important role of the G₂ checkpoint is to ensure that all of the chromosomes have been accurately replicated without mistakes or damage.
- <u>The M Checkpoint:</u>It occurs near the end of the meta-phase stage of mitosis. it determines whether all the sister chromatids are correctly attached to the spindle micro-tubules
Answer:
When a muscle cell contracts, the myosin heads each produce a single power stroke.
Explanation:
In rest, attraction strengths between myosin and actin filaments are inhibited by the tropomyosin. When the muscle fiber membrane depolarizes, the action potential caused by this depolarization enters the t-tubules depolarizing the inner portion of the muscle fiber. This activates calcium channels in the T tubules membrane and releases calcium into the sarcolemma. At this point, <em>tropomyosin is obstructing binding sites for myosin on the thin filament</em>. When calcium binds to the troponin C, the troponin T alters the tropomyosin by moving it and then unblocks the binding sites. Myosin heads bind to the uncovered actin-binding sites forming cross-bridges, and while doing it ATP is transformed into ADP and inorganic phosphate which is liberated. Myofilaments slide impulsed by chemical energy collected in myosin heads, <u>producing a power stroke</u>. The power stroke initiates when the myosin cross-bridge binds to actin. As they slide, ADP molecules are released. A new ATP links to myosin heads and breaks the bindings to the actin filament. Then ATP splits into ADP and phosphate, and the energy produced is accumulated in the myosin heads, which starts a new binding cycle to actin. Z-bands are then pulled toward each other, thus shortening the sarcomere and the I-band, and producing muscle fiber contraction.
During a myocardial infarction, proteins that are normally inside the cells leak into the plasma, due to loss of plasma membrane integrity.
<h3>Cardiac disorders and it's effects:</h3>
There are different types of cardiac or heart disorders that occurs due to different etiological origins.
Example of a cardiac disorder is the myocardial infarction.
Myocardial infarction is defined as the blockage of blood flow to the heart by the presence of blood clot.
This hinders the delivery of oxygen carried by the blood to tissue cells leading to apoptosis (which is a programmed cell death).
This will cause the plasma membrane of cells to lose its integrity leading to leaking of proteins into the plasma.
Learn more about myocardial infarction here:
brainly.com/question/1373449
Anything can come out of that but I think type b might be more possible to happen.
