cell transport mechanisms and permeability Flashcards
facilitated diffusion
the movement of a substance from high to low with the aid of a carrier molecule
carrier proteins
- transport hydrophilic or large molecules
- can move more than one substance (cotransport)
- can move more than one substance in opposite directions (countertransport)
primary active transport
- requires ATP
- moves from low to high concentration
secondary active transport
movement for one of two substances to follow the concentration gradient (cell uses ATP)
vesicular transport & types
- materials move in sacs called vesicles, uses ATP
- endocytosis & exocytosis
endocytosis
import extracellular substances into vesicles called endosomes
exocytosis
movement of waste or secretory products from intracellular vesicle to outside the cell
step 1 in receptor-mediated endocytosis
materials bind to receptors on the membrane surface
step 2 in receptor-mediated endocytosis
saturated areas of receptors from pockets that pinch off to form an endosome
step 3 in receptor-mediated endocytosis
clathrin-coated vesicles form
step 4 in receptor-mediated endocytosis
the endosome fuses with a lysosome filled with digestive enzymes
step 5 in receptor-mediated endocytosis
ligands are released from their receptors, and enter the cytoplasm
step 6 in receptor-mediated endocytosis
the endosomal membrane detaches from the secondary lysosome
step 7 in receptor-mediated endocytosis
the endosomal membrane returns to the cell surface, where its receptors become available to bind more ligands
pinocytosis
brings fluid and small molecules into cell “cell drinking”
phagocytosis
cytoplasmic extensions surround the object and bring it into the cell “cell eating”
exocytosis
vesicle contents are releases into extracellular environment
