<span>There are numerous proteins in muscle. The main two are thin actin filaments and thick myosin filaments. Thin filaments form a scaffold that thick filaments crawl up. There are many regulatory proteins such as troponin I, troponin C, and tropomyosin. There are also proteins that stabilize the cells and anchor the filaments to other cellular structures. A prime example of this is dystrophin. This protein is thought to stabilize the cell membrane during contraction and prevent it from breaking. Those who lack completely lack dystrophin have a disorder known as Duchene muscular dystrophy. This disease is characterized by muscle wasting begininng in at a young age and usually results in death by the mid 20s. The sarcomere is the repeating unit of skeletal muscle.
Muscle cells contract by interactions of myosin heads on thick filament with actin monomers on thin filament. The myosin heads bind tightly to actin monomers until ATP binds to the myosin. This causes the release of the myosin head, which subsequently swings foward and associates with an actin monomer further up the thin filament. Hydrolysis and of ATP and the release of ADP and a phosphate allows the mysosin head to pull the thick filament up the thin filament. There are roughly 500 myosin heads on each thick filament and when they repeatedly move up the thin filament, the muscle contracts. There are many regulatory proteins of this contraction. For example, troponin I, troponin C, and tropomyosin form a regulatory switch that blocks myosin heads from binding to actin monomers until a nerve impulse stimulates an influx of calcium. This causes the switch to allow the myosin to bind to the actin and allows the muscle to contract. </span><span>
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Answer: I would go with B. Here’s why: An index fossil is usually easily recognizable, and underwent a wide geographic distribution. What leads me to believe B is the correct answer, is because it’s something that existed “ all over the world”.
Just like the bacteria, the archaea have evolved a diverse array of metabolic pathways. As extremophiles, their metabolism shows many adaptations to the extreme environments of their habitat. There are facultative and obligate anaerobes and aerobic organisms in this kingdom.
Answer:
1. Radiometric dating
2. Relative dating is used to determine the age of fossils or rock layers by by comparing it to similar rocks and fossils of known ages.
3. The youngest rock layers are at the top and the oldest are at the bottom, which is according to the law of superposition.
4. Tribolite and Pecten fossils
Fossils are used to determine the ages of rock layers. Index fossils are the most useful in determining relative aging. Index fossils are of organisms that lived for a short period of time. An index fossil allows a scientist to determine the age of the rock it is in. So if they are found in a particular age, it means they belong in that age.
5. Scientists commonly use radioactive dating methods by using radioactive decay cloak of certain elements such as potassium or carbon to date fossils or rocks.
6. Law of superposition because in terms of finding the age of the rock as an object, all that needs to be identified are the layers of the rock.
7. The nuclear decay of radioactive elements are a process that behaves in a clock-like fashion which makes it a useful tool for determining the exact age of fossils or rocks.
Answer:
<h2>A. G¹ phase</h2>
<u>Explanation:</u>
In G¹ phase - RNA and Proteins are synthesised and the volume of Cytoplasm increase.
