Ch. 5 Cell Membrane and Transport

1. Ch. 5 Cell Membrane and Transport LIPID BILAYER cytoplasm extracellular fluid

2. Cell Membrane—thin, flexible membrane that surrounds all cells. • Selectively permeable - regulates what enters and exits the cell. • Made up of a phospholipid bilayer. • Double layer of phospholipids • Gives cells flexible but strong barrier between itself and its surroundings.

3. Phospholipids Hydrophilichead • Phospholipids are a lipid that have a • Glycerol • Phosphate • Two fatty acid chains Hydrophobictail

5. Hydrophilic Hydrophobic

7. PhospholipidBilayer hydrophilic head hydrophobic tails Water (outside of cell) hydrophilic head Water (inside of cell)

8. Fluid mosaic model

9. Fluid mosaic model Fibers of extracellular matrix Carbohydrate (of glycolipid) Glycolipid Glycolipid Phospholipid Microfilaments of cytoskeleton Protein Steroids

10. Membrane Proteins • > 50 kinds of proteins found in human red blood cells so far • Carry out many different functions • Structural, external, identification tags, form junctions between cells • Enzymes – catalytic teams for molecular assembly lines • Receptors – receive chemical messages from other cells • Message transfer is called signal transduction • Help move substances across membrane

11. Cell Transport: movement of substances across the cell membrane based on concentration gradient. Concentration Gradient: Difference in concentration over a distance. No Gradient HIGH concentration LOWconcentration Gradient

12. How the Cell Membrane does its thing… • Two categories of cell transport: • Passive transport – Requires NO energy • High to low concentration • Active transport – Requires energy • Low to high concentration

13. 3 types of passive transport: • Simple Diffusion • High to low concentration • Small, lipid soluble molecules like CO2 and O2 • Example: • Oxygen enters bloodstream from the lungs

14. 2) Facilitated Diffusion • Large, charged, or polar substances move across membrane in this way. • Always moves from high to low concentration • Requires a transport protein Transport Protein

15. 2) Facilitated Diffusion • Water can move through because it is small, buttransport is slow, aquaporins allow for faster diffusion Transport Protein

16. 3) Osmosis: • Diffusion of water through a selectively permeable membrane until equilibrium occurs. • High to low concentration • Water will cross membrane until solute concentrations(molecules/mL) are _______________on both sides of membrane

17. What words do you know that start with…… • Iso______________ • Definition: • Hyper___________ • Definition: • Hypo____________ • Definition:

18. Tonicity • A term used to describe the tendency of a cell in a given solution to lose or gain water.

19. Isotonic Solution—Concentration of solutes is equal in and out of the cell. • No net movement of water. • Cell maintains shape.

20. Hypertonic Solutions—Concentration of solutesis higher outside the cell. • Water exits the cell. • Animal Cell: shrinks which is known as crenation • Plant Cell: cell membrane collapses away from cell wall. This is known as plasmolysis.

21. D. Hypotonic Solution—Concentration of solutes is lower outside the cell. 1. Water enters the cell. 2. Animal cell swells and may burst which is known as Cytolysis. 3. Plant cell—cell wall prevents breaking. (Turgor Pressure)

22. Tonicity in animals • Osmoregulation: or an animal to survive changes in salinity it must have a method to prevent excessive uptake of water or excessive loss of water • Ex: freshwater fish live in hypotonic environment • Ex: saltwater fish live in a ___________________ environment

23. Have evolved to have kidneys and gills that constant work to flush water out of the body

24. Tonicity in plants • Turgidity: When a plant cell has a net inflow of water. • Plasmolysis: When a plant cell loses water, plasma membrane pulls away from cell wall. • Also happens in bacteria and fungi

27. HYPOTONIC HYPERTONIC ISOTONIC

29. What type of solution is each cell in? HYPERTONIC HYPOTONIC ISOTONIC

30. Ticket out Quiz 2M sucrose solution 1 liter of pure water 10M sucrose solution 2M sucrose solution 1) 2) 3) HYPOTONIC CONDITIONS HYPERTONIC CONDITIONS ISOTONIC CONDITIONS Fig. 5.14, p. 88

31. Active Transport • Substances move against concentration gradient -low to high concentration • Requires energy (ATP) • Requires a transport protein.

32. How do LARGE molecules enter and exit the cell? • BULK TRANSPORT: Movement of particles into or out of a cell without passing through the plasma membrane. • Requires energy!

33. Endocytosis – Large materials move into cell. • Cell engulfs large materials such as macromolecules.

34. Phagocytosis • Cell engulfs large particles, microbes, and cellular debris • “Cell eating”

35. Pinocytosis • Cells receive bulk amounts off liquid • “Cell drinking”

36. Exocytosis - vesicle fuses with the membrane and exits the cell. • Expels materials such waste and hormones.

37. Lorenzo’s Oil ALD Can not digest FAT Fat builds up and destroys his nerves Fat enters body in 2 ways – food and biosynthesis Oil stops biosynthesis! Oil keeps the body from building up the bad fat COMPETITIVE inhibition