CELL MEMBRANE AND TRANSPORT

Transcription

1 CELL MEMBRANE AND TRANSPORT

2 Objectives Describe how the structure of the plasma membrane allows it to function as a regulatory structure and/or protective barrier for a cell Compare the mechanisms that transport materials across the plasma membrane Describe how membrane-bound organelles facilitate the transport of materials within a cell

3 Why are cells so small? Relates to need to exchange materials across the plasma membrane Must be large enough to house DNA, proteins, and structures needed to survive and reproduce Remain small enough to allow for a surface-tovolume ratio that will allow adequate exchange with the environment

4 3 units 1 unit 1 unit 3 units Total volume 27 units 3 27 units 3 Total surface area Surface-tovolume ratio 54 units units 3 2 6

5 Examples from Your Body Respiratory system Function: exchange CO 2 and O 2 with blood stream Alveoli in lungs provide more surface area so these gases can be exchanged at a faster rate By United States National Institute of Health: National Heart, Lung and Blood Institute [Public domain], via Wikimedia Commons

6 Examples from Your Body Digestive System Function: absorb nutrients from the food you eat Villi and microvilli in the small intestine increase surface area for maximum absorption By Olek Remesz (wiki-pl: Orem, commons: Orem) (Own work) [CC BY-SA ( via Wikimedia Commons By BallenaBlanca [CC BY-SA 4.0 ( via Wikimedia Commons

7 Plasma Membrane The plasma membrane forms a flexible boundary between the living cell and its surroundings. Phospholipids form a two-layer sheet called a phospholipid bilayer hydrophilic heads face outward, exposed to water, and hydrophobic tails point inward, shielded from water By Juancoronado1974 (Own work) [CC BY-SA 3.0 ( via Wikimedia Commons

8 Components of Plasma Membrane Phospholipids Hydrophobic tails Hydrophilic head Cholesterol Proteins Other stuff By derivative work: Dhatfield (talk) Cell_membrane_detailed_diagram_3.svg: *derivative work: Dhatfield (talk) Cell_membrane_detailed_diagram.svg: LadyofHats Mariana Ruiz (Cell_membrane_detailed_diagram_3.svg) [CC BY-SA 3.0 ( via Wikimedia Commons

9 By derivative work: Dhatfield (talk) Cell_membrane_detailed_diagram_3.svg: *derivative work: Dhatfield (talk) Cell_membrane_detailed_diagram.svg: LadyofHats Mariana Ruiz (Cell_membrane_detailed_diagram_3.svg) [CC BY-SA 3.0 ( via Wikimedia Commons

10 New Membrane Phospholipids are produced in the smooth ER Vesicle pinches off ER and migrates to the Golgi Vesicle pinches off Golgi and moves to the plasma membrane Inside of vesicle becomes outside of the cell By Mariana Ruiz LadyofHats [Public domain], via Wikimedia Commons

11 Membrane Proteins Transport Enzymes Communication Intercellular junctions Cell-to-cell recognition

12 By LadyofHats Mariana Ruiz [Public domain], via Wikimedia Commons

13 Diffusion Passive transport of a substance across a membrane without using energy Particles move from an area of high concentration to an area of low concentration DOWN its concentration gradient

14 By LadyofHats Mariana Ruiz Villarreal [Public domain], via Wikimedia Commons Equilibrium

15 Selective Permeability Membranes only allow certain molecules to pass through Smaller molecules have an easier time moving through the membrane By Pidalka44 [Public domain], via Wikimedia Commons

16 Facilitated Diffusion A molecule is allowed to move across the cell membrane with the help of a transmembrane protein channel By LadyofHats Mariana Ruiz Villarreal [Public domain], via Wikimedia Commons

17 Water The most important substance to cross the semipermeable membrane This process is called osmosis

18 Osmosis If a membrane is permeable to water but not a solute and you separate two solutions with different concentrations of the solute: water will cross the membrane moving down its concentration gradient until the solute concentration on both sides is equal (equilibrium)

19 Hans Hillewaert / CC BY-SA 4.0, via Wikimedia Commons

20 Importance of Osmosis Water balance between cells and their environment is important for an organism What happens to cells when placed in solutions with different concentrations?

21 Solution Concentrations Isotonic solution the concentration of solute is the same on both sides of a membrane, and the cell volume will not change Hypotonic solution the solute concentration is lower outside the cell, water molecules move into the cell, and the cell will expand and may burst Hypertonic solution the solute concentration is higher outside the cell, water molecules move out of the cell, and the cell will shrink.

22 By LadyofHats (did it myself based on [1], [2],[3] and [4].) [Public domain], via Wikimedia Commons

23 WHAT ABOUT PLANTS?

24 By LadyofHats (did it myself based on [1], [2],[3] and [4].) [Public domain], via Wikimedia Commons

25 CONTRACTILE VACUOLES PUMP OUT EXCESS WATER A. Contractile vacuole is full of water. The canals are closed. B. The vacuole starts losing water. A pore appears on the vacuole, and water moves from inside of the vacuole to outside the cell C. The vacuole is empty. Canals are ready to open for taking up water. D. Contractile vacuole gains water from cytoplasm. Water moves from canals to vacuole, which makes vacuole become much bigger By Katyddd (Own work) [CC BY-SA 4.0 ( via Wikimedia Commons

26 Active Transport vs. Passive Active movement of substance against concentration gradient (requires ATP/ENERGY) Passive movement down a concentration gradient Simple diffusion Facilitated diffusion

27 By LadyofHats Mariana Ruiz Villarreal [Public domain], via Wikimedia Commons

28 Other ways of moving in and out of Cells Phagocytosis engulfing food Pinocytosis engulfing fluid Endocytosis engulfing targeted molecules Exocytosis releasing molecules from the cell

29 PHAGOCYTOSIS Cell eating CELL EATING 1. Cell extends plasma membrane around particle and it becomes enclosed in a vacuole inside the cell 2. The vacuole merges with a lysosome containing enzymes 3. Enzymes break down particle into useable materials or energy for the cell By Mango Slices (Own work) [CC BY-SA 4.0 ( via Wikimedia Commons

30 By Jacek FH [Public domain], via Wikimedia Commons PINOCYTOSIS CELL DRINKING

31 ENDOCYTOSIS By Mariana Ruiz LadyofHats (Own work) [Public domain], via Wikimedia Commons

32 By すじにくシチュー (Own work) [CC0], via Wikimedia Commons EXOCYTOSIS