Introduction to Membrane Transport quiz #1 Flashcards
Introduction to Membrane Transport quiz #1
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What does it mean when a biological membrane is described as selectively permeable?
A selectively permeable membrane allows only certain molecules to cross based on their size, charge, and polarity, acting as a barrier to others. Which types of molecules can freely diffuse across biological membranes without protein facilitation?
Small, uncharged, nonpolar molecules such as oxygen, carbon dioxide, and nitrogen gases can freely diffuse across membranes. Why can't large macromolecules like proteins and polysaccharides freely cross the cell membrane?
Large macromolecules cannot freely cross the membrane because their size prevents them from passing through the lipid bilayer without assistance. How do charged or polar molecules typically cross biological membranes?
Charged or polar molecules require facilitation from membrane proteins to cross biological membranes because they cannot diffuse freely. What are the two main categories of membrane transport, and what distinguishes them?
The two main categories are molecular transport (for small molecules) and bulk transport (for large molecules). What are the subtypes of molecular transport across membranes?
Molecular transport includes passive transport (osmosis, simple diffusion, facilitated diffusion) and active transport (primary and secondary). What is bulk transport, and what processes does it include?
Bulk transport is the movement of large molecules across membranes and includes endocytosis (phagocytosis, pinocytosis, receptor-mediated endocytosis) and exocytosis. How does the polarity of a molecule affect its ability to cross the cell membrane?
Nonpolar molecules cross membranes easily, while polar molecules have more difficulty and may require protein facilitation. What is the difference between passive and active transport across membranes?
Passive transport does not require energy and moves molecules down their concentration gradient, while active transport requires energy to move molecules against their gradient. Give an example of a small, uncharged, polar molecule and describe its ability to cross the membrane.
Water is a small, uncharged, polar molecule that can cross the membrane, but not as easily as nonpolar molecules. What is the role of membrane proteins in facilitated diffusion?
Membrane proteins assist the movement of molecules that cannot freely diffuse across the membrane, such as charged or polar substances. Why are biological membranes considered barriers to some molecules but not others?
Biological membranes are barriers because their structure allows selective passage based on molecular size, charge, and polarity, preventing some molecules from diffusing freely.
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