B. Active Transport: Active transport is a process that requires energy and involves the movement of solutes across the membrane against their concentration gradient (they need to move “uphill”) Examples include:
2 Types of Active Transport:
i) Primary Active Transport : Energy derived from the hydrolysis of ATP changes the shape of a carrier protein, which “pumps” a substance across a plasma membrane against it’s concentration gradient (low concentration to high concentration) Example:
ii) Secondary Active Transport : Energy stored in a Na+ concentration gradient is used to drive other substances across the membrane against their concentration gradient (low concentration to high concentration). The energy was produced during Primary Active Transport (the hydrolysis of ATP).
2 Transport in Vesicles
Some substances are enclosed in vesicles to be transported from one structure to another within a cell, or between cells. Vesicles also import and release substances from the extracellular fluid. Transport in vesicles requires energy and are therefore classified as Active Transport.
3 types of vesicle transport:
i) Endocytosis: substances are transported into the cell.
a) Receptor-mediated endocytosis: A highly selective type of endocytosis by which cells take up (in) specific Ligands (molecules that bind to specific receptors) Examples: Cholesterol (LDL), transferring, some vitamins, certain hormones, and antibodies.
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