Week # 9 Lecture – pp 129-133

1. Lecture Presentations for Integrated Biology and Skills for Success in ScienceBanks, Montoya, Johns, & Eveslage Week # 9 Lecture – pp 129-133

2. Expectations for the course • Community • Working with others—in class, in lab, in study groups • Learning • Complete all assignments for deep comprehension • Respect • Fellow students, instructors and self

3. Guiding Principles for the Course • Looking at seemingly simple things deeply • Conceptual understanding • Practical Applications • Contextualized

4. Transport Mechanisms, Organelles, • By the end of the lecture today, students will be able to: • Explain the importance of and describe the processes of diffusion, osmosis, facilitated diffusion and active transport. • Describe which types of membrane transports require energy and which do not require energy. • List the major organelles in a eukaryotic cell and describe their major roles in the cell.

5. Membrane Transport • plasma membrane – a barrier and a gateway between the cytoplasm and ECF • selectively permeable – allows some things through, and prevents other things from entering and leaving the cell • passive transport mechanisms requires no ATP • random molecular motion of particles provides the necessary energy • diffusion, osmosis, facilitated diffusion • active transport mechanisms consumes ATP • active transport and vesicular transport

7. Simple Diffusion • Simple Diffusion – the net movement of particles from area of high concentration to area of low concentration • due to their constant, spontaneous motion • Also known as movement down the concentration gradient – concentration of a substance differs from one point to another Cy. Downgradient Upgradient

9. Osmosis • Osmosis - flow of water from one side of a selectively permeable membrane to the other • from side with higher water concentration to the side with lower water concentration • reversible attraction of water to solute particles forms hydration spheres • makes those water molecules less available to diffuse back to the side from which they came • Aquaporins- channel proteins specialized for passage of water . Side A Side B (a) Start

10. Facilitated Diffusion • facilitated diffusion – passive transport of solute through a membrane down its concentration gradient • does not consume ATP • solute attaches to binding site on carrier, carrier changes confirmation, then releases solute on other side of membrane . ECF ICF The solute binds to a receptor site on the carrier and the carrier changes conformation. The carrier releases the solute on the other side of the membrane. 1 A solute particle enters the channel of a membrane protein (carrier). 2 3

11. Active Transport • active transport – carrier-mediated transport of solute through a membrane up (against) its concentration gradient • ATP energy consumed to change carrier • Examples of uses: • sodium-potassium pump keeps K+ concentration higher inside the cell • bring amino acids into cell • pump Ca2+ out of cell

12. Sodium-Potassium Pump • each pump cycle consumes one ATP and exchanges three Na+ for two K+ • keeps the K+ concentration higher and the Na+ concentration lower with in the cell than in ECF • necessary because Na+ and K+constantly leak through membrane • half of daily calories utilized for Na+ - K+ pump . 3 Na+ out Extracellularfluid ATP Intracellular fluid 2 K+ in ADP + + P i

13. http://www.youtube.com/watch?v=RPAZvs4hvGA

14. The Cell Interior • structures in the cytoplasm • organelles, cytoskeleton, and inclusions • all embedded in a clear gelatinous cytosol • Organelles – internal structures of a cell that carry out specialized metabolic tasks • membranous organelles – those surrounded by one or two layers of unit membrane • nucleus, mitochondria, lysosome, peroxisome, endoplasmic reticulum, and Golgi complex • organelles not surrounded by membranes • ribosome, centrosome, centriole, basal bodies

15. Nucleus • Largest organelle (5 m in diameter) • most cells have one nucleus • a few cells are anuclear or multinucleate • nuclear envelope - two unit membranes surround nucleus • perforated by nuclear pores formed by rings of protein • regulate molecular traffic through envelope • hold two unit membranes together • nucleoplasm – material in nucleus • chromatin (thread-like matter) composed of DNA and protein • nucleoli – one or more dark masses where ribosomes are produced

16. Endoplasmic Reticulum • endoplasmic reticulum - system of interconnected channels called cisternae enclosed by unit membrane • rough endoplasmic reticulum – composed of parallel, flattened sacs covered with ribosomes • continuous with outer membrane of nuclear envelope • produces the phospholipids and proteins of the plasma membrane • synthesizes proteins that are packaged in other organelles or secreted from cell

17. Endoplasmic Reticulum • smooth endoplasmic reticulum • lack ribosomes • cisternae more tubular and branching • cisternae are thought to be continuous with those of rough ER • synthesizes steroids and other lipids • detoxifies alcohol and other drugs • manufactures all membranes of the cell • rough and smooth ER are functionally different parts of the same network

19. Ribosomes • Ribosomes - small granules of protein and RNA • found in nucleoli, in cytosol, and on outer surfaces of rough ER, and nuclear envelope • they ‘read’ coded genetic messages (messenger RNA) and assemble amino acids into proteins specified by the code

20. Golgi Complex • Golgi complex - a small system of cisternae that synthesize carbohydrates and put the finishing touches on protein and glycoprotein synthesis • receives newly synthesized proteins from rough ER • sorts them, cuts and splices some of them, adds carbohydrate moieties to some, and packages the protein into membrane-bound Golgi vesicles • some become lysosomes • some migrate to plasma membrane and fuse to it • some become secretory vesicles for later release

22. Lysosomes • Lysosomes - package of enzymes bound by a single unit membrane • extremely variable in shape • Functions • intracellular hydrolytic digestion of proteins, nucleic acids, complex carbohydrates, phospholipids, and other substances • autophagy – digest and dispose of worn out mitochondria and other organelles • autolysis – ‘cell suicide’ – some cells are meant to do a certain job and then destroy themselves

24. Mitochondrion • mitochondria – organelles specialized for synthesizing ATP • variety of shapes – spheroid, rod-shaped, kidney bean-shaped, or threadlike • surrounded by a double unit membrane • inner membrane has folds called cristae • spaces between cristae are called matrix • matrix contains ribosomes, enzymes used for ATP synthesis, small circular DNA molecule – mitochondrial DNA (mtDNA) • “Powerhouses” of the cell • energy is extracted from organic molecules and transferred to ATP . Matrix Outer membrane Inner membrane Mitochondrial ribosome Intermembrane space Crista

25. Mitochondrion Matrix Outer membrane Inner membrane Mitochondrialribosome Intermembranespace Crista 1 µm

26. http://www.youtube.com/watch?v=aczbMlSMr8U

27. Exit Quiz • 1). What transport mechanism is responsible for moving water molecules from an area of high concentration to low concentration? • 2). In order for active transport mechanism to work there must be an input of what molecule? Why this molecule? • 3). What part of the nucleus is responsible for producing rRNA (ribosomes)? • 4). What organelle is responsible for modifying proteins after they are synthesized? • 5). Why is the mitochondria known as the “powerhouse of the cell”?