Textbook Question
Mark the following statements as true or false. If a statement is false, correct it to make a true statement.
Increased amounts of blood flowing through the dermis lead to pallor in the skin.
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5. Integumentary System
The Epidermis: Layers
Problem L3.B5b
Textbook Question
Many antiaging skin creams contain collagen and hyaluronic acid. Manufacturers claim that the collagen and hyaluronic acid applied to the surface of the skin will be absorbed into the dermis, where they will be incorporated into dermal tissue.
Are these substances polar or nonpolar?
Verified step by step guidance1
Understand the chemical nature of collagen and hyaluronic acid: Collagen is a protein made up of amino acids, which are polar molecules due to the presence of functional groups like -NH2 (amino) and -COOH (carboxyl). Hyaluronic acid is a polysaccharide with repeating disaccharide units containing carboxyl and hydroxyl groups, making it highly polar as well.
Recall the properties of polar and nonpolar substances: Polar molecules have an uneven distribution of charge, allowing them to interact with water and other polar substances. Nonpolar molecules, on the other hand, lack this charge distribution and are hydrophobic.
Consider the structure of the skin: The outermost layer of the skin, the stratum corneum, is composed of dead keratinized cells and lipids, forming a barrier that is hydrophobic and nonpolar in nature. This layer is designed to prevent the penetration of polar substances.
Analyze the compatibility of polar substances with the skin barrier: Since collagen and hyaluronic acid are polar, they are unlikely to penetrate the nonpolar, hydrophobic stratum corneum without assistance from specialized delivery systems or chemical modifications.
Conclude the absorption potential: Based on their polar nature and the skin's barrier properties, collagen and hyaluronic acid applied topically are unlikely to be absorbed into the dermis in their natural forms. Instead, they may remain on the surface or require alternative methods to enhance penetration.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Polarity of Molecules
Polarity refers to the distribution of electrical charge over the atoms in a molecule. Polar molecules have a significant difference in electronegativity between their atoms, leading to a partial positive charge on one end and a partial negative charge on the other. This property affects how substances interact with each other, particularly in biological systems.
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Collagen
Collagen is a structural protein found in the skin, bones, and connective tissues. It is a large, fibrous protein that provides strength and elasticity. Collagen molecules are generally polar due to the presence of amino acids with polar side chains, which allows them to interact with water and other polar substances in the dermis.
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Hyaluronic Acid
Hyaluronic acid is a glycosaminoglycan, a type of carbohydrate that is highly polar due to its numerous hydroxyl (-OH) groups. This polarity allows it to attract and retain water, making it an essential component in maintaining skin hydration and elasticity. Its ability to form hydrogen bonds with water contributes to its effectiveness in anti-aging skin creams.
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