How does exchange of nutrients, gases, and wastes occur during pregnancy if maternal and fetal blood never mix?
What will be an ideal response?
Maternal and embryonic bloodstreams never mix. The design of the placenta allows exchange to occur. Substances move between maternal and embryonic blood by diffusing across the walls of the embryonic vessels in the chorionic villi. Oxygen diffuses from maternal blood into embryonic blood, and carbon dioxide diffuses in the opposite direction. Transport proteins assist in the movement of essential nutrients from the maternal blood into embryonic blood vessels inside the villi.
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Which of the following most accurately describes a polar covalent bond?
A. the interaction of a hydrogen connected to an atom with a high electronegativity, and an electronegative atom of another molecule B. the interaction of an atom with very high electronegativity and an atom with very low electronegativity C. the unequal sharing of electrons between an atom with a partial positive charge and an atom with a partial negative charge D. the equal sharing of electrons between atoms of identical or similar electronegativities E. None of these choices accurately describe polar covalent bonds.
You are studying a diploid organism that has 14 sets of chromosomes. How many chromatids will a cell from this organism have in metaphase of meiosis II?
A. 7 B. 14 C. 28 D. 56
An atom in which the number of electrons is different from the number of protons is called a(n)
a. ion. b. molecule. c. compound. d. isotope. e. acid.
The first bacterium that was clearly identified as the cause of an infectious disease was:a
Legionella pneumophila, which causes Legionnaires' disease. b. Chlamydia sp., which causes pelvic inflammatory disease in women. c. Clostridium botulinum, which causes botulism. d. Vibrio cholerae, which causes cholera. e. Bacillus anthracis, which causes anthrax.