In fetal circulation, the ductus venosus bypasses the liver and the ductus arteriousus bypasses the lungs. Ductus arteriosus also called ductus botalli is a blood vessel connecting the main pulmonary artery to the proximal ascending aorta. It does allow most of the blood from right ventricle to bypass the fetus's fluid-filled non-functioning lungs. Ductus venosus on the hand allows oxygenated blood from the placenta to bypass the liver.
Proteins help with acting as structural components in the body, speeding up chemical reactions, and transporting substances around the body. Proteins are made up of amino acids, which create enzymes. Enzymes are often affected by environmental factors in the body such as concentration, temperature, and pH.
Proteins are very important for DNA and RNA. (ribonucleic acid)
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D. Bacteria because “bacteria” is actually a domain itself
