Photoreceptor proteins are light-sensitive proteins involved in the sensing and response to light in a variety of organisms. Some examples are rhodopsin in the photoreceptor cells of the vertebrate retina,phytochrome in plants, and bacteriorhodopsin<span> and bacteriophytochromes in some bacteria.
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The answer is <span>B. contains enzymes that begin the breakdown of proteins.
Saliva is watery substance secreted by salivatory glands. <em>It cleanses the mouth</em> and maintenance oral hygiene. <em>It moistens the food</em>, so the created food bolus could easier pass into the esophagus. It also <em>carries food chemicals to taste receptors</em> so they can be tested. It contains enzymes involved in the food digestions. Some of them are amylase, which begins the breakdown of the starch, and lipase, which begins the breakdown of triglycerides. <u>There are no enzymes in the saliva that break down proteins</u>.</span>
Speciation is not a mechanism of microevolution.
Enzymes are regulated by more than the binding of small molecules. A second method that is used all the time by eucaryotic cells to regulate a protein's function is the covalent addition of a phosphate group to one of its amino acid side chains. These phosphorylation events can affect the protein in two important ways.
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There are two types of cell, prokaryotic (bacteria) and eukaryotic (animal, plant, fungi and protoctista (unicellular organisms)). Prokaryotes have no nucleolus – the DNA is in the cytoplasm, and it can from small circular strands of DNA called plasmids. Eukaryotic cells all have their DNA enclosed in a nucleus.
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