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Practice Questions Basic knowlede questions: 1. Some molecules require active ...

Mar 18, 2024

Practice Questions Basic knowlede questions: 1. Some molecules require active transport while others can use some form of diffusion. Create a chart to show which molecules use which form of transport. What proteins are involved?

Answer

Molecules use different forms of transport across the cell membrane, including active transport and diffusion. Proteins such as transporters, channels, and pumps are involved in these processes.

Solution

Molecule Types: - Oxygen and carbon dioxide typically use simple diffusion due to their small size and nonpolar nature. - Water uses facilitated diffusion through aquaporins. - Ions like Na⁺, K⁺, Ca²⁺, and Cl⁻ use facilitated diffusion through ion channels or active transport via pumps. - Glucose uses facilitated diffusion through GLUT transporters. - Larger molecules like amino acids and nucleotides require active transport through various carrier proteins

Transport Proteins: - Aquaporins for water. - Ion channels for ions (specific for each ion). - Sodium-potassium pump (Na⁺/K⁺-ATPase) for active transport of Na⁺ and K⁺ against their concentration gradients. - GLUT transporters for glucose. - Various carrier proteins for amino acids and nucleotides, such as the SLC family of transporters

Key Concept

Transport across cell membranes

Explanation

Molecules move across cell membranes via different mechanisms depending on their size, polarity, and concentration gradients. Small nonpolar molecules diffuse directly through the lipid bilayer, while polar or charged molecules require specific proteins to facilitate their movement. Active transport is used when molecules need to be moved against their concentration gradient, which requires energy.