Ost proteins that function in the cytosol (such as actin) or in the nucleus (such as DNA polymerase) are synthesized by free ribosomes. Proteins that function within the endomembrane system (such as lysosomal enzymes) or those that are destined for secretion from the cell (such as insulin) are synthesized by bound ribosomes.
<span>As a protein destined for the endomembrane system is being synthesized by a ribosome, the first amino acids in the growing polypeptide chain act as a signal sequence. That signal sequence ensures that the ribosome binds to the outer membrane of the ER and that the protein enters the ER lumen.</span>
Answer: movement is always voluntary
Explanation:
Muscles are contractile:
- Contractility is the ability of muscle cells to forcefully shorten. Think of having the ability to flex a muscle.
Muscles are excitable:
- Excitable tissue can conduct or transmit electrical impulses. Basically, it can react to stimulus, which may be delivered from a motor neuron or a hormone. For example, the hormone epinephrine helps muscles to produce force.
Muscles respond to stimulus:
- well since muscles are an excitable tissue, they can react to stimulus. (see answer above)
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Muscle movement is NOT always voluntary:
- Some muscle movement is voluntary, which means it is under conscious control. For example, a person decides to open a book and read. Other movements are involuntary, meaning they are not under conscious control, such as the contraction of your pupil in bright light, breathing, blinking, your heart beating, etc.
- Therefore, the correct answer is:
movement is always voluntary
hope this helps :)
