Answer:
The correct answer is 3: "<em>High levels of Ca2+ are expected to be found </em><em>within the sarcoplasmic reticulum</em>".
Explanation:
Muscular contraction is a highly regulated process that depends on free calcium concentration in the cytoplasm. Amounts of cytoplasmic calcium are regulated by <u>sarcoplasmic reticulum</u> that functions as a storage of the ion.
When a nerve impulse reaches the membrane of a muscle fiber, through acetylcholine release, the membrane depolarizes producing the entrance of calcium from <u>extracellular space</u>. The impulse is transmitted along the membrane to the sarcoplasmic reticulum, from where calcium is released. At this point, <em>tropomyosin is obstructing binding sites for myosin on the thin filament</em>. The calcium channel in the sarcoplasmic reticulum controls the ion release, that activates and regulates muscle contraction, by increasing its cytoplasmic levels. When <em>calcium binds to the troponin C</em>, <em>the troponin T alters the tropomyosin by moving it and then unblocks the binding sites,</em> making possible the formation of <em>cross-bridges between actin and myosin filaments.</em> When myosin binds to the uncovered actin-binding sites, ATP is transformed into ADP and inorganic phosphate.
Z-bands are then pulled toward each other, thus shortening the sarcomere and the I-band, and producing muscle fiber contraction.
Answer:
There is a need to transform the accumulation of acetyl-CoA into the ketone bodies, as one knows that acetyl-CoA is both labile and possess an enormous amount of energy. Hence, acetyl-CoA due to its unstable characteristic is not ideal for circulation within the tissues, and at the same time, the compound acetyl-CoA does not possess the tendency to pass through the cell membrane.
Due to these reasons, the conversion of acetyl-CoA into the ketone bodies is done, the ketone bodies also act as an alternative source of energy. The ketone bodies work as water-soluble correspondents of fatty acids. The production of ketone bodies generally takes place within the liver cells' mitochondrial matrix. The three forms of ketone bodies are beta-hydroxybutyrate, acetoacetate, and acetone.
The production of ketone bodies by the liver cells helps the cells of the brain at the time of starvation, as the brain cannot use fatty acids as an energy source, as the fatty acids cannot pass through the blood-brain barrier.
1) Chordata=A chordate is an animal of the phylum Chordata. All chordates possess 5 synapomorphies, or primary characteristics, at some point during their larval or adulthood stages that distinguish them from all other taxa
2) Vertebrates=vertebrate, also called Craniata, any animal of the subphylum Vertebrata, the predominant subphylum of the phylum Chordata. The vertebrates are also characterized by a muscular system consisting primarily of bilaterally paired masses and a central nervous system partly enclosed within the backbone.
3)Invertebrates=Invertebrates are animals that neither possess nor develop a vertebral column, derived from the notochord. This includes all animals apart from the chordate subphylum Vertebrata. Familiar examples of invertebrates include arthropods, mollusks, annelid, and cnidarians.
4) Poikilothermic animals=A poikilotherm is an animal whose internal temperature varies considerably. Poikilotherms have to survive and adapt to environmental stress.
5) Homeothermic animals=The term homeothermic refers to the warm-blooded animals which have constant and relatively higher temperature. They are animals which can maintain their internal body temperature. Complete answer: Homeothermic animals are warm-blooded and maintain a constant body temperature, for example birds and mammals.
6) Oviparous= producing young by means of eggs which are hatched after they have been laid by the parent, as in birds.
7)Vivaparous=bringing forth live young which have developed inside the body of the parent
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The reasons are:
- the blood is very low on nutrition
- the leech is not feeding itself regularly
The leech slows it metabolism a lot, so it can survive on very low nutrition. The blood is very low on nutrition, and it is the leech's food source, so the evolution made it preserve energy.
The leach doesn't have the opportunity to feed itself on regular basis, so it takes maximum advantage of any opportunity and consumes as much blood as possible so that it can survive long term when it will not have food at disposal.
