1. Lesson 1: Cell Structures Involved in Cell Transport

2.  Describe the structure and function of the plasma membrane in relation to cell transport.  Identify the types of membrane proteins involved in cell transport.  Identify the roles of the cytoplasm and cytoskeleton in cell transport.  Identify the role of the endomembrane system in eukaryotic organisms in cell transport.  Discuss special transport structure of plant cells.  Outline the role of cell transport in homeostasis.

3.  Barrier between cytoplasm inside and environment outside the cell  Protects, supports the cell  Controls what goes in and what goes out ◦ Selective permeability  allows only certain substances to pass through  Water most important substance; most essential molecules for life are soluble  Inorganic ions: sodium (Na + ), potassium (K + ), calcium (Ca 2+ ), and chlorine (Cl - )  Gases: oxygen helps release energy that powers cellular reactions  Hormones: transmit messages

4.  Consists of two layers of phospholipids ◦ hydrophobic, or water-hating, interior (tails) ◦ hydrophilic, or water-loving, exterior (heads)  Proteins embedded within have a variety of functions  Hydrophobic molecules are nonpolar, easily cross; if small enough  Hydrophilic molecules are polar, need help to cross; usually through embedded proteins

5.  NOT INVOLVED IN TRANSPORT ◦ Peripheral proteins  loosely bound to membrane surface or to part of a integral protein  INVOLVED IN TRANSPORT ◦ Integral proteins  transmembrane protein; extend into and usually span interior of membrane

6.  Transport proteins  ions, polar molecules  Types of transport proteins: ◦ Channel proteins  hydrophilic channel  Water passes through aquaporin channel proteins  Ions pass through ion channels  Other ions pass through gated channels; open and close in response to a stimulus ◦ Carrier proteins  hold molecules and change shape as they pass them through  Sodium-potassium pump

7.  Contains enzymes, salts, organelles, and a variety of organic molecules ◦ Enzymes help dissolve cellular waste for export ◦ Salts are conductors of electricity  Movement generated through churning of cytoplasmic streaming  speeds up distribution of nutrients, proteins, and organelles within cell  http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter4/animation_- _cytoplasmic_streaming.html http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter4/animation_- _cytoplasmic_streaming.html

8.  Consists of three different threadlike structures: microfilaments, intermediate filaments, microtubules ◦ Microfilaments and microtubules both components of intracellular transport  Microfilaments  composed of protein called actin; act like tracks within cells for myosin molecules  Microtubules  tracks for vesicle intracellular transport

9.  Separates and compartmentalizes interrelated functions of variety of organelles ◦ Equates to a division of labor  Organelles involved: ◦ Nuclear envelope, smooth endoplasmic reticulum, rough ER, Golgi, lysosomes, endosomes, vesicles, vacuoles, and plasma membrane  Some through direct connection; others through vesicular transport ◦ Vesicles bud off of sending organelles; fuse with receiving organelles

10.  Helps make and transport proteins and lipids  Connected to the pores of the nuclear envelope  Two types of endoplasmic reticulum: ◦ Rough endoplasmic reticulum (RER) ◦ Smooth endoplasmic reticulum (SER).  Rough Endoplasmic Reticulum (RER) ◦ Studded with ribosomes; involved in protein synthesis, the production and transport of new membrane, and the modification and transport of newly formed proteins within the cell ◦ Proteins synthesized on the RER are transported to other locations through vesicles formed in the SER.  Smooth Endoplasmic Reticulum (SER) ◦ Not studded with ribosomes ◦ Contains enzymes for lipid biosynthesis (change to phospholipids and steroids) ◦ Forms transition vesicles that travel along microtubular tracks in the cytoplasm  Transport molecules made in the RER to the Golgi apparatus

11.  Processes proteins and prepares them for use both inside and outside the cell  Receives proteins from the ER that have been transported in vesicles, packages and labels them  Sends them on to their next destinations in another set of vesicles  Also involved in the transport of lipids around the cell http://www.johnkyrk.com/golgiAlone.html

12.  Sac-like organelles  Store and transport large molecules  Pinch off ER and Golgi ◦ Transport to plasma membrane; fuse with it ◦ Going out = exocytosis  Pinch inward at plasma membrane ◦ Transport to destinations inside the cell ◦ Going in = endocytosis

13.  Lysosomes bud off of the Golgi apparatus; infused with hydrolytic enzymes ◦ Digestive vesicles of the cell; contain enzymes called hydrolases  Digest proteins, nucleic acids, lipids, and complex sugars. ◦ Vesicles enter the cell through endocytosis; sent to lysosomes contents processed  Break down and disarm many potentially pathogenic and foreign materials; expel them outside the cell through exocytosis  Endosomes formed during endocytosis allow materials from outside the cell to enter the cell ◦ Formed when the cell’s plasma membrane folds inward to surround macromolecules, encircles them, brings them into the cell by pinching off the membrane at their point of entry  Vesicles larger than 100 nanometers in size are referred to as vacuoles.

14.  Structure not found in animal cells, cell wall ◦ Rigid layer that surrounds the plasma membrane ◦ Supports and protects the cell  Tiny holes, or pores, in the cell wall called plasmodesmata (singular, plasmodesma) ◦ Form open channels through which strands of cytosol connect between adjacent cells ◦ Allow water, nutrients, and other substances to move into and out of the cells

15.  Cell to function normally=> stable state must be maintained inside the cell ◦ Example: concentration of salts, nutrients, and other substances must be kept within a certain range  Process of maintaining stable conditions inside a cell (or an entire organism) is homeostasis ◦ Homeostasis requires constant adjustments, because conditions are always changing both inside and outside the cell ◦ Structures and processes described in this lesson and the next lesson play important roles in homeostasis and are consider homeostatic mechanisms ◦ By moving substances into and out of cells, they keep conditions within normal ranges and maintain homeostatic regulation inside the cells and the organism as a whole  If homeostatic mechanisms fail to maintain homeostatic regulation disease or death of a cell or organism may follow.

16.  A major role of the plasma membrane is transporting substances into and out of the cell.  The plasma membrane is selectively permeable, allowing only certain substances to pass through.  Proteins embedded within the plasma membrane help to move hydrophilic, polar molecules into the cell.  The cytoplasm is the internal medium for cell transport.  Vesicle aids in the import and export of macromolecules.  Plant cells have a special transport structures that are not found in animal cells, called plasmodesmata.  Cell transport helps cells maintain homeostasis by keeping conditions within normal ranges inside all of an organism’s cells.  If homeostatic mechanisms fail, homeostatic regulation may fluctuate and disease or death of a cell or organism can follow.