The Working Cell

2. The Working Cell • Cells “work”by • Moving substance into and out of the cell. • Doing chemical reactions which utilize enzymes.

3. Membranes are fluid mosaics of lipids and proteins with many functions ATP Glycoprotein CYTOPLASM

4. Membranes are fluid mosaics of lipids and proteins with many functions Membrane proteins perform many functions. Some proteins help maintain cell shape and coordinate changes inside and outside the cell through their attachment to the cytoskeleton and extracellular matrix. Some proteins function as receptors for chemical messengers from other cells. Some membrane proteins function as enzymes.

5. Membranes are fluid mosaics of lipids and proteins with many functions Some membrane glycoproteins are involved in cell-cell recognition. Membrane proteins may participate in the intercellular junctions that attach adjacent cells to each other. Membrane proteins transport substances across the membrane.

6. EVOLUTION CONNECTION: Membranes form spontaneously, a critical step in the origin of life Phospholipids, the key ingredient of biological membranes, spontaneously self-assemble into simple membranes. The formation of membrane-enclosed collections of molecules was a critical step in the evolution of the first cells.

7. Types of transportation possible across membrane…. Diffusion- Simple diffusion- Osmosis- Facilitated Diffusion- Active Transport- Bulk Flow/Exocytosis/Endocytosis-

8. Membrane Molecules of dye Pores Net diffusion Net diffusion Equilibrium

10. Diffusion-overview • Substances move down the concentration gradient • Passive, requires no energy • Speed dependent on: • Concentration difference, steepness • Temperature • Size of molecules • Presence of electric charge • Pressure

11. Osmosis is the diffusion of water across a membrane One of the most important substances that crosses membranes is water. The diffusion of water across a selectively permeable membrane is called osmosis.

12. Lowerconcentrationof solute Equalconcentrationsof solute Higherconcentrationof solute H2O Solutemolecule Selectivelypermeablemembrane Watermolecule Solute moleculewith cluster ofwater molecules Osmosis

13. Water balance between cells and their surroundings is crucial to organisms Tonicity is a term that describes the ability of a solution to cause a cell to gain or lose water. Tonicity mostly depends on the concentration of a solute on both sides of the membrane. Hypotonic- _______________ Hypertonic- _______________ Isotonic- __________________

14. Water balance between cells and their surroundings is crucial to organisms RBC Most animal cells lack the ability to prevent lysis if placed in a hypotonic solution. Human cells are about 0.9% saline (salt water). So cells are isotonic to a 0.9% saline solution. Ocean water is about 3.5 % salt. SO…now you know why you can’t drink salt water!

15. 2% sucrose solution 1 liter of 10% sucrose solution 1 liter of 2% sucrose solution 1 liter of distilled water Hypotonic Conditions Hypertonic Conditions Isotonic Conditions

16. Water balance between cells and their surroundings is crucial to organisms For an animal cell to survive in a hypotonic or hypertonic environment, it must engage in osmoregulation, the control of water balance. The cell walls of plant cells, prokaryotes, and fungi make water balance issues somewhat different. The cell wall prevents the cell from taking in too much water but pressure builds up! This is called turgor pressure.

17. Turgor Pressure

18. Transport proteins can facilitate diffusion across membranes Solutemolecule Membrane proteins can be channels or carriers (facilitated diffusion) Transportprotein

19. Example of Facilitative Diffusion: glucose transporter (channel)

20. SCIENTIFIC DISCOVERY: Research on another membrane protein led to the discovery of aquaporins Dr. Peter Agre received the 2003 Nobel Prize in chemistry for his discovery of aquaporins. Because water is polar, its diffusion through a membrane’s hydrophobic interior is relatively slow. The very rapid diffusion of water into and out of certain cells is made possible by a protein channel called an aquaporin. His research on the Rh protein used in blood typing led to this discovery.

21. 1 2 3 4 Cells expend energy in the active transport of a solute Transportprotein P P Phosphatedetaches. Proteinchanges shape. P ATP Solute ADP Phosphateattaching Transport Proteinreversion Solute binding

22. Example of Active Transport: Calcium Pump

23. Moves 2 kinds of ions in opposite directions. • Requires ATP • 3 Na+ move out of cell, 2 K+ ions move in • Important in nerve cell impulse transmission Example of ActiveTransport/ Pump/Cotransport: Sodium-Potassium Pump

24. Move in response to gradient Uses energy to move against gradient High Concentration gradient across cell membrane ATP Low SimpleDiffusion of lipid-soluble Substances across bilayer Passive transport of water- soluble substances through channel protein; no energy input needed Active transport through ATPase; requires energy input from ATP aka Facilitated Diffusion

25. Exocytosis and endocytosis transport large molecules across membranes There are three kinds of endocytosis. Phagocytosis Pinocytosis Receptor-mediated endocytosis

26. Endocytosis (vesicles in) Exocytosis (vesicles out)

27. Receptor-mediated Endocytosis

28. Type of WBC, defensive function parasite macrophage

29. Membrane Cycling Proteins that will become part of the cell membrane are shipped in vesicles that fuse with the Golgi body. They are modified and sent off in other vesicles that fuse with the plasma membrane. In this way the cell membrane can be replaced and repaired as needed.

30. Why is movement across a membrane important? • Cells need raw materials • _____________________ • _____________________ • _____________________ • Cells need to get rid of waste: • ____________________ • ____________________ • Cells need to maintain water balance: • __________________________ • __________________________ • ___________________

31. Cystic Fibrosis • CFTR is a protein channel which allow for the movement of Cl-, followed by water • Thin, slippery film is produced on surface of cell/tissue • Single amino acid change in protein causes the CFTR to be destroyed before reaching cell membrane • No film causes mucus to dry out and become sticky

32. Internet sites Diffusion, Osmosis, and Movement Across a Membrane: Summary Info • http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect09.htm

33. The Working Cell • Cells “work”by • Moving substance into and out of the cell. • Doing chemical reactions which utilize enzymes.

34. Energy Flows • Energy is not created or destroyed, there is a finite amount of energy in the universe (1st law of thermodynamics) • Energy is converted from one form to another. It flows in one direction, spontaneously, from a concentrated (ordered) form to a less concentrated form. Energy disperses. (2nd law of thermodynamics) • Example: photosynthesis converts solar energy to chemical energy

35. Cells transform energy as they perform work Cells are small units, a chemical factory, housing thousands of chemical reactions. Cells use these chemical reactions for cell maintenance, manufacture of cellular parts, and cell replication.

36. Cells transform energy as they perform work Energy is the capacity to cause change or to perform work. There are two kinds of energy. Kinetic energy is the energy of motion. Potential energy is energy that matter possesses or stores as a result of its location or structure.

37. Waste products Energy conversion Fuel Heatenergy Carbon dioxide Gasoline   Combustion Kinetic energyof movement Water Oxygen Energy conversion in a car Heatenergy Cellular respiration Glucose Carbon dioxide   ATP ATP Oxygen Water Energy for cellular work Energy conversion in a cell

38. Cells transform energy as they perform work Chemical reactions are either: • Endergonic • Requires input of energy • Products are high in potential energy • Ex. Photosynthesis • Exergonic • Releases energy • More energy in reactants than products • Ex. Cellular Respiration

39. Chemical reactions either release or store energy Photosynthesis is a type of endergonic process. Energy-poor reactants, carbon dioxide, and water are used. Energy is absorbed from sunlight. Energy-rich sugar molecules are produced.

40. ATP,adenosine triphosphate, powers nearly all forms of cellular work. ATP consists of __________________________, ___________________________, ________________________. ATP drives cellular work by coupling exergonic and endergonic reactions

41. ATP drives cellular work by coupling exergonic and endergonic reactions Hydrolysis of ATP releases energy by transferring its third phosphate from ATP to some other molecule in a process called phosphorylation. Most cellular work depends on ATP energizing molecules by phosphorylating them.

42. Triphosphate ATP: Adenosine Phosphategroup P P P Adenine Ribose H2O Hydrolysis Energy P P P Diphosphate ADP: Adenosine

43. Enzymes speed up the cell’s chemical reactions by lowering energy barriers Although biological molecules possess much potential energy, it is not released spontaneously. An energy barrier must be overcome before a chemical reaction can begin. This energy is called the activation energy (EA).

44. Role of ENZYMES… • ENZYMES ARE PROTEINS • Shape determines function, Specific • Lowers activation energy(energy needed to run a reaction) • Catalysts(make enzymes occur faster, millions of times faster) Energy “in” This reaction is binding A and B together Energy “out”

45. A specific enzyme catalyzes each cellular reaction • Larger than substrates( reactants that bind to the enzyme) • Take reactants apart OR put reactants together

46. Binding of substrate to enzyme is… • Temporary • Weak • Changes the enzyme’s shape very slightly (induced-fit)

47. 1 2 3 4 Enzyme availablewith empty activesite Active site Substrate(sucrose) Substrate bindsto enzyme withinduced fit Enzyme(sucrase) Glucose Fructose H2O Products arereleased Substrate isconverted toproducts

48. A specific enzyme catalyzes each cellular reaction Enzyme activity is affected by: Temperature pH Cofactors (inorganic) Coenzymes (organic) Competitive inhibitors Noncompetitive inhibitors

49. Enzyme inhibitors can regulate enzyme activity in a cell Substrate Active site Enzyme Allosteric site Normal binding of substrate Competitiveinhibitor Noncompetitiveinhibitor Enzyme inhibition

50. Enzyme inhibitors can regulate enzyme activity in a cell Enzyme inhibitors are important in regulating cell metabolism.