Listen 98 74 Endocytosis Key Idea: Endocytosis is an active transport process in which the cell engulfs material and draws it in. Endocytosis is a type of active transport in which the plasma membrane folds around a substance to transport it across the plasma membrane into the cell. The ability of cells to do this is a function of the flexibility of the plasma membrane. Material (solids or fluids) that are to be brought into the cell are engulled by an infolding of the plasma membrane. Plasma membrane Vesicle buds inwards from The vesicle carries molecules into the cell. the plasma membrane The contents may then be digested by enzymes delivered to the vacuole by lysosomes. Receptors and pit beginning to form HIV particle Phagocytosis (or 'cell-eating') involves the cell engulfing solid material to form large phagosomes or vacuoles (e.g. food vacuoles). It may be non-specific or receptor- receptor proteins on the membrane so that mediated. Examples: Feeding in Amoeba, phagocytosis of foreign material and cell debris by neutrophils and macrophages. Receptor mediated endocytosis is triggered when certain metabolites, hormones, or viral particles bind to specific Pinocytosis (or 'cell-drinking") involves the non-specific uptake of liquids or fine suspensions into the cell to form small pinocylic vesicles. Pinocytosis is used primarily for absorbing extracellular fluid. Examples: Uptake in many protozoa, scme cells of the liver, and some plant cells. the material can be engulfed. Examples: The uptake of lipoproteins by mammalian cells and endocytosis of viruses (above). ? 1. What is the purpose on endocytosis? 2. Is endocytosis active or passive transport? 3. Describe the following types of endocytosis: (a) Phagocytosis: (b) Receptor mediated endocytosis: (c) Pinocytosis: ? 4. Explain how the plasma membrane can form a vesicle:

Integral membrane proteins... Choose all that could apply are bound to the membrane by only interacting with the phospholipid's polar head O contain many amino acids with hydrophobic residues O contain alpha-helical membrane spanning domains O would not be digested by trypsin in a permeabilized cell O interact with the phospholipid core of the phospholipid bilayer

Part C - Facilitated diffusion via channels and carrier proteins The majority of solutes that diffuse across the plasma membrane cannot move directly through the lipid bilayer. The passive movement of such solutes (down their concentration gradients without the input of cellular energy) requires the presence of specific transport proteins, either channels or carrier proteins. Diffusion through a transport protein in the plasma membrane is called facilitated diffusion. outside cell channel protein inside cell carrier protein' Adapted from Biology by Campbell and Reece ©2008 Pearson Education, Inc. Sort the phrases into the appropriate bins depending on whether they are true only for channels, true only for carrier proteins, or true for both channels and carriers. ▸ View Available Hint(s) only channels transport primarily small polar organic molecules provide a continuous path across the membrane provide a hydrophilic path across the membrane allow water molecules and small ions to flow…

Match the following statement related to membrane transport processes to the appropriate term or terms: passive transport, facilitated transport, active transport. A transporter (or carrier) protein is necessary. (Select all that apply.) passive transport facilitated transport active transport O O

Transportation by transporters and channels are similar in that they both can occur with passive transport but yet one (transport by transporters) sometimes requires energy in order to happen, does the use of energy provide something special to the cell?

During exocytosis, integral proteins facing the outside of a vesicle are O released into the surrounding medium. O incorporated into the plasma membrane so that they face the cytoplasm. O released back into the cytoplasm.

Draw out protein transport in the cell. Make sure to include all steps involved in transport through the secretory and endocytic pathways (including ER resident protein retrieval, transport to lysosome), transport in and out of the nucleus, and import into mitochondria. Include all details of vesicle transport (protein coat, SNARES, Rab) in your drawing

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