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Oxygen is transferred from mom to fetus via the placenta through?
Active Transport
Passive (Simple) Diffusion
Facilitated Diffusion
Osmosis
The correct answer is: Passive (Simple) Diffusion
Oxygen transfer from the mother to the fetus occurs primarily through passive (simple) diffusion. This process relies on the concentration gradient of oxygen between the mother's blood and the fetal blood. The mother's blood has a higher concentration of oxygen, which allows oxygen molecules to move naturally across the placental barrier into the fetal circulation. This diffusion is a passive process, meaning it does not require energy expenditure from the body. Instead, it occurs based on the principle that substances tend to move from areas of higher concentration to areas of lower concentration until equilibrium is reached. In the case of oxygen, this natural movement is essential for meeting the fetus's metabolic needs, especially as the fetus develops and requires increasingly more oxygen. In contrast, active transport requires energy to move substances against their concentration gradient, which does not apply here as oxygen moves along its gradient. Facilitated diffusion typically involves carrier proteins to move substances across a membrane, but oxygen is small enough to pass through cell membranes directly without such assistance. Osmosis specifically refers to the movement of water across a semipermeable membrane, which is not the mechanism involved in oxygen transfer.