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10 Terms
1
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transport by proteins
reminder... proteins are imbedded in the cell membrane
2
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facilitated transport/diffusion
- facilitate = "to help" - some molecules easily cross the membrane because carrier proteins facilitate their passage - carrier proteins help only specific molecule ie glucose can enter cells much faster than other sugars - more with the concentration gradient (from higher to lower concentration) therefore no ATP energy required - channel and carrier proteins both do this - AKA "passive transport"
3
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active transport
- hint: activity requires energy so this type of transport requires ATP (energy giving molecule) - ions or molecules moved against the concentration gradient using a protein (channel proteins don't do this type of transport) - egs include: a) absorption of nutrients by cells in digestive tract b) Na+/K+ pump in nerve cells - up to 40% of a cell's energy may be used for active transport
4
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transport by vesicles
- molecules too large for proteins are brought in and out by vesicles eg. proteins (hormone secretion) - always requires ATP energy - can move both with and against the concentration gradient
5
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exocytosis
- exo = exit - vesicles from the golgi body, etc contain molecules for body's use - vesicles move to and fuse with membrane during secretion eg. digestive enzyme amylase from pancreas or human growth hormone from anterior pituitary - fusing with membrane adds to it (increases total area of cell membrane)
6
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endocytosis
- take in substances by vesicles - membrane "lost" by endocytosis is balanced by membrane gained by exocytosis - occurs in one of 3 ways
- "cell eating" - large material is taken in such as a food particle or invader - common in some human white blood cells - when an endocytic vesicle fuses with a lysosome, digestion occurs
9
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pinocytosis
- "cell drinking" - vesicles form around liquid or very small particles - performed by blood cells or cells lining the kidney tubule
10
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receptor-mediated endocytosis
- form of pinocytosis - specific receptor sites on outer membrane surface binds with a particular peptide hormone, vitamin, or lipoprotein - involved in intercellular exchange (transport between cells) - commonly occurs across the membranes of the placenta between fetal and maternal blood