<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:
3 criteria used to determine whether is REAL SCIENCE are temperature, precipitation and atmospheric pressure
Explanation:
Temperature forms the basis of a weather condition, it depicts the role of some other criteria, other factors are precipitation and atmospheric pressure
The birth rate was greater than the death rate and the immigration rate was greater than the emigration rate. Options B and D are correct.
<h3>Population growth</h3>
From the illustrated image, the world experienced an upward growth in population between 1950 and 2010.
In order for population growth to occur:
- the birth rate must exceed the death rate
- immigration must exceed emigration
Either or both of the above conditions will lead to a growth in the population.
Thus, options B and D are correct.
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The part of a DNA molecule responsible for the direct coding of specific traits in an organism is the nucleotide sequence.
<h3>How is a DNA molecule structured?</h3>
The DNA molecule is the biological molecule that stores genetic information in living organisms.
The DNA molecule is made up of three major components in its structure:
- Five carbon sugar
- Nucleotide bases
- Phosphate group
The five carbon sugar is deoxyribose while the nucleotide bases are four in number as follows:
- Adenine
- Guanine
- Thymine
- Cytosine
These nucleotides are responsible for the direct coding of specific traits in an organism.
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