1.Structure and functions The cytoplasmic membrane, also called a cell membrane or plasmamembrane. It lies internal to the cell wall and encloses the cytoplasmof the bacterium A. Structure and Composition Like all biological membranes in nature, the bacterial cytoplasmicmembrane is composed phospholipid and protein molecules The phospholipid bilayer is arranged so that the polar ends of themolecules (the phosphate and glycerol portion of the phospholipidthat is soluble in water) form the outermost and innermostsurface of the membrane while the non-polar ends (the fatty acidportions of the phospholipids that are insoluble in water) formthe center of the membrane

2. B. FunctionsThe cytoplasmic membrane is a selectively permeable membranethat determines what goes in and out of the organism . All othermolecules require carrier molecules to transport them through themembrane.Materials move across the bacterial cytoplasmic membrane by passivediffusion and active transport 3. The Plasma Membrane Phospholipid bilayer Peripheral proteins Integral proteins Transmembrane Proteins Figure 4.14b 4. The Plasma MembraneFigure 4.14a 5. Movement of Substances Across MembranesPassive Transport:1. Simple Diffusion2. Facilitated Diffusion3. OsmosisActive Transport:1. Antiporters2. Symporters3. ATP-binding cassette (ABC) system4. Group translocation 6. 1. Passive Diffusion Passive diffusion is the net movement of gases or small uncharge polar molecules across a phospholipid bilayer membrane from an area of higher concentration to an area of lower concentration 7. a) Simple diffusion:Movement of a solutefrom an area of highconcentration to an areaof low concentration Figure 4.17a 8. b. Osmosis the diffusion of water across a membrane from an area of higher water concentration(lower solute concentration) to lower water concentration (higher solute concentration). Osmosis is powered by the potential energy of a concentration gradient and does not require the expenditure (belanjawan) of metabolic energy 9. The Principle of Osmosis Figure 4.18ce 10. c. Facilitated Diffusion transport of substances across a membrane by transport proteins, Facilitated diffusion is powered by the potential energy of a concentration gradient and does not require the expenditure (belanjawan) of metabolic energy. 11. Facilitated Diffusion: Carrier proteinmolecules aid in the movement ofsubstances through cell membranefrom high to low concentration 12. Facilitated diffusion: Solute combines with a transporterprotein in the membraneFigure 4.17b-c 13. Through lipid layer Aquaporins (water channels)Figure 4.17d 14. Movement of Materials acrossMembranes Active transport: Requires a transporter protein and ATP Group translocation: Requires a transporter protein and PEP 15. 2. Active Transport Active transport is a process whereby the cell uses bothtransport proteins and metabolic energy to transportsubstances across the membrane against the concentrationgradient. In this way, active transport allows cells to accumulate(mengumpulkan) needed substances even when theconcentration is lower outside. The energy is provided by proton motive force, the hydrolysisof ATP, or the breakdown of some other high-energycompound such as phosphoenolpyruvate (PEP). Proton motive force is an energy gradient resulting fromhydrogen ions (protons) moving across the membrane fromgreater to lesser hydrogen ion concentration. ATP is the form ofenergy cells most commonly use to do cellular work. PEP is oneof the intermediate high-energy phosphate compoundsproduced during glycolysis. 16. Active Transport: Carrier Protein molecules aid inmovement of molecules against a concentration gradient 17. For the majority of substances a cell needs formetabolism to cross the cytoplasmicmembrane, specific transport proteins (carrierproteins) are required. This is because theconcentration of nutrients in most naturalenvironments is typically quite low. Transport proteinsallow cells to accumulate nutrients from even a spaceenvironment. Transport proteins involved in active transport includeantiporters, symporters, the proteins of the ATP-binding cassette (ABC) system, and the proteinsinvolved in group translocation . 18. Antiporter Antiporters are transport proteins that simultaneously transport two substances across the membrane in opposite directions; one against the concentration gradient and one with the concentration gradient. Metabolic energy is required for this type of transport 19. Symporter Symporters are transport proteins that simultaneously transport two substances across the membrane in the same direction. Symporters use the potential energy of electrochemical gradients from protons (H+), that is, proton motive force to co-transport ions, glucose, and amino acids against their concentration gradient 20. ATP-binding cassette (ABC) system An example of an ATP-dependent active transport found in various gram-negative bacteria is the ATP- binding cassette (ABC) system. This involves substrate-specific binding proteins located in the bacterial periplasm, the gel-like substance between the bacterial cell wall and cytoplasmic membrane 21. Step 1 . The periplasmic-binding protein picks up the substance to be transported and carries it to a membrane- spanning transport protein 22. Step 2 The molecule to be transported across the membrane enters the transporter protein system and a molecule of ATP enters the ATP binding site of the ATP-hydrolyzing protein. 23. Step 3 Energy provided by the hydrolysis of ATP into ADP, phosphate, and energy moves the molecule across the membrane 24. Step 4 The carrier protein releases the molecule being transported and the transporter system is ready to be used again. 25. Group translocation another form of active transport that can occur in prokaryotes. In this case, a substance is chemically altered during its transport across a membrane so that once inside, the cytoplasmic membrane becomes impermeable to that substance and it remains within the cell. 26. Step 1 When bacteria use the process of group translocation to transport glucose across their membrane, a high-energy phosphate group from phosphoenolpyruvate (PEP) is transferred to the glucose molecule to form glucose-6- phosphate. 27. Step 2 A high-energy phosphate group from PEP is transferred to the glucose molecule to form glucose-6-phosphate. 28. Step 3 The glucose-6-phosphate is transported across the membrane. 29. Step 4 Once the glucose has been converted to glucose-6- phosphate and transported across the membrane, it can no longer be transported back out.