Join thousands of students who trust us to help them ace their exams!Watch the first video
Multiple Choice
Which of the following substances would NOT transport readily in blood?
A
Glucose dissolved in plasma
B
Cholesterol in its free, unbound form
C
Carbon dioxide as bicarbonate ion ($\mathrm{HCO_3^-}$)
D
Oxygen bound to hemoglobin
Verified step by step guidance
1
Step 1: Understand the context of the question. Blood is a transport medium in the body, and substances are carried either dissolved in plasma, bound to proteins, or chemically modified. The question asks which substance would NOT transport readily in blood.
Step 2: Analyze the transport mechanisms for each substance listed. Glucose is a polar molecule and dissolves readily in plasma due to its hydrophilic nature. Carbon dioxide is transported primarily as bicarbonate ion ($\mathrm{HCO_3^-}$), which is highly soluble in plasma. Oxygen is transported bound to hemoglobin, a protein specialized for oxygen transport.
Step 3: Consider cholesterol. Cholesterol is a hydrophobic molecule and does not dissolve readily in plasma in its free, unbound form. Instead, it is typically transported in blood bound to lipoproteins, such as LDL and HDL, which help solubilize it.
Step 4: Compare the transport properties of the substances. Glucose, bicarbonate ion, and oxygen bound to hemoglobin are all efficiently transported in blood due to their solubility or binding mechanisms. Free, unbound cholesterol, however, does not transport readily because it is hydrophobic and lacks a solubilizing mechanism in plasma.
Step 5: Conclude that the correct answer is cholesterol in its free, unbound form, as it does not have a mechanism to transport readily in blood without being bound to lipoproteins.