Answer and 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, tropomyosin is obstructing binding sites for myosin on the thin filament. 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 released. Myofilaments slide impulsed by chemical energy collected in myosin heads, producing a power stroke. 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.
Bones of snakes are very loosely fused together like in humans. Hence these bones can move individually allowing the snakes to be really flexible. The ribs of snakes do not join like those of humans but instead, have free ends and do not have a sternum.
Answer:
Facilitated Transport.
Explanation: In facilitated transport, also called facilitated diffusion, materials diffuse across the plasma membrane with the help of membrane proteins. Hopefully this helps!
The right answer is B and C.
For proposal C, I will give you an example, that of an autosomal recessive disease. If a parent is heterozygous for an allele causing an autosomal recessive disease (due to a mutation), it may be that it transmits the allele to its descendence, as it may not be able to transmit it (since in one heterozygous subject, not all of its gametes carry the mutated allele) and thus the mutation will no longer be copied through the generaitons.
Each individual is genetically unique. Its genes are distributed along chromosomes contained in the nucleus. Mutations can lead to the appearance of different versions of genes: alleles. A diploid individual has two copies of each gene, which may be identical or different alleles. Mixing during sexual reproduction partly explains the genetic diversity of individuals.
