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level: cell membrane

Questions and Answers List

level questions: cell membrane

Question	Answer
- phospholipid bi-layer - proteins, cholesterol and other molecules are embedded in the membrane - semi-permeable: selectively permeable and only allows some substance to pass through and not other - hydrophilic head - hydrophobic tails - fatty, most water soluble substance cannot diffuse through it: exceptions include oxygen and carbon dioxide	cell membrane
- embedded in the bi-layer - allows the movement of substances in and out of the cell - act as receptor sites for hormones - channel proteins: open channels that allow simple diffusion - carrier proteins: allow facilitated diffusion and active transport	proteins
- physical barrier: separates cell cytoplasm form extracellular fluid - regulation of passage of materials: controls movement of materials in and out of the cells - maintains homeostasis	functions
- passive process of movement from high to low concentration - spreads out particles so that they are evenly spread - gases and liquids	diffusion
- diffusion of water across a permeable membrane form a region of higher water concentration to a region of lower water concentration	osmosis
- requires special protein in membrane to carry substances across - can be active or passive - proteins in cell membrane bind to the molecule to be transported and help their passage across the membrane - are specific - become specific - activity is regulated by hormones	carrier-mediated trransport
- active process where materials are move in membrane bound sacs - endocytosis: taking liquids and solids into cell by vesicular transport - pinocytosis: liquids - phagocytsis: solids - exocytosis: contents of a vesicle inside cell are passed to outside	vesicular transport