1 Place your homework (just the review assignment) in the black basket. Pick up a copy of the powerpoint notes (2 sheets) Sit down and for the love, sharpen pencils before I’m ready to speak.

2 The Plasma Membrane The Plasma Membrane - Gateway to the Cell

3 Please pick up a copy of the homeostasis and transport notes.

4 Photograph of a Cell Membrane

5 Cell Membrane flexible The cell membrane is flexible and allows a unicellular organism to move

6 Homeostasis Balanced internal condition of cells Also called equilibrium Maintained by plasma (or cell) membrane controlling what enters & leaves the cell

7 Functions of Cell Membrane Protective barrier Regulate transport in & out of cell (selectively permeable) Allow cell recognition Provide anchoring sites for filaments of cytoskeleton

8 Functions of Plasma Membrane Provide a binding site for enzymes Interlocking surfaces bind cells together (junctions) Interlocking surfaces bind cells together (junctions) Contains the cytoplasm (fluid in cell) Contains the cytoplasm (fluid in cell)

9 Structure of the Cell Membrane Peripheral protein Integral Protein Lipid Bilayer

10 Phospholipids Make up the cell membrane Contains 2 fatty acid chains that are nonpolar Head is polar & contains a –PO 4 group

11 Fluid mosaic model FLUID- because individual phospholipids and proteins can move around freely within the layer, like it’s a liquid. MOSAIC- because of the pattern produced by the scattered protein molecules when the membrane is viewed from above. FLUID MOSAIC MODEL

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13 hydrophilic Polar heads are hydrophilic “water loving ” hydrophobic Nonpolar tails are hydrophobic “water fearing” Cell Membrane Makes membrane “Selective” in what crosses

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15 Cell Membrane Hydrophobic molecules pass easily; hydrophillic DO NOT The cell membrane is made of 2 layers of phospholipids called the lipid bilayer

16 Solubility Materials that are soluble in lipids can pass through the cell membrane easily

17 Small molecules and larger hydrophobic molecules move through easily. e.g. O 2, CO 2, H 2 O Selectively Permeable Membrane

18 Ions, hydrophilic molecules larger than water, and large molecules such as proteins do not move through the membrane on their own. Semipermeable Membrane

19 Types of Transport Across Cell Membranes

20 Please pick up a copy of the notes and do the following warmup: –Sketch a picture of a phospholipid and label the phosphate and fatty acids and identify which part of the molecule is polar, nonpolar, hydrophilic, and hydrophobic.

21 Passive Transport Movement of substances across the cell membrane without any input of energy on the part of the cell.

22 Simple Diffusion NORequires NO energy HIGH to LOWMolecules move from area of HIGH to LOW concentration or down the concentration gradient.

23 Simple Diffusion Concentration Gradient is the difference in the concentration of a substance from one location to another.

24 DIFFUSION PASSIVE Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY

25 Diffusion of Liquids

26 Diffusion through a Membrane Cell membrane Solute moves DOWN concentration gradient (HIGH to LOW) until equilibrium is reached

27 Osmosis Diffusion of water across a membraneDiffusion of water across a membrane Moves from HIGH water potential (low solute) to LOW water potential (high solute)Moves from HIGH water potential (low solute) to LOW water potential (high solute) Diffusion across a membrane Semipermeable membrane

28 A Hypertonic solution has a higher concentration of dissolved particles than the cell. A Hypotonic solution has a lower concentration of dissolved particles than the cell. An Isotonic solution has the same concentration of dissolved particles as the cell.

29 Diffusion of H 2 O Across A Membrane High H 2 O potential Low solute concentration Low H 2 O potential High solute concentration

30 Cell in Isotonic Solution CELL 10% NaCL 90% H 2 O 10% NaCL 90% H 2 O What is the direction of water movement? The cell is at _______________. equilibrium ENVIRONMENT NO NET MOVEMENT

31 Cell in Hypotonic Solution CELL 10% NaCL 90% H 2 O 20% NaCL 80% H 2 O What is the direction of water movement?

32 Cell in Hypertonic Solution CELL 15% NaCL 85% H 2 O 5% NaCL 95% H 2 O What is the direction of water movement? ENVIRONMENT

33 Cells in Solutions

34 Isotonic Solution NO NET MOVEMENT OF H 2 O (equal amounts entering & leaving) Hypotonic Solution CYTOLYSIS (cell rupture) Hypertonic Solution PLASMOLYSIS (cell shrinkage)

35 Osmosis in Red Blood Cells Isotonic Hypotonic Hypertonic

36 In plant cells, plasmolysis results in wilting and osmotic pressure results in turgor pressure. Osmosis in plant cells

37 Facilitated diffusion  Doesn’t require energy  Uses transport proteins to move high to low concentration Examples: Glucose or amino acids moving from blood into a cell.

38 Proteins Are Critical to Membrane Function

39 Types of Transport Proteins Channel proteins are embedded in the cell membrane & have a pore for materials to cross Carrier proteins can change shape to move material from one side of the membrane to the other

40 Facilitated Diffusion Molecules will randomly move through the pores in Channel Proteins.

41 Facilitated Diffusion Some Carrier proteins do not extend through the membrane.Some Carrier proteins do not extend through the membrane. They bond and drag molecules through the lipid bilayer and release them on the opposite side.They bond and drag molecules through the lipid bilayer and release them on the opposite side.

42 Carrier Proteins Other carrier proteins change shape to move materials across the cell membraneOther carrier proteins change shape to move materials across the cell membrane

43 Please get out your notes from yesterday and answer the following question:

44 What would happen to an egg (in terms of osmosis) if it were placed in a saltwater solution?

45 Pick up a copy of the notes. Pick up the study guide. Sharpen pencils.

46 Passive Transport Review Movement of particles across the cell membrane without energy input on the part of the cell is passive transport. Moves particles with/down the concentration gradient.

47 Three major types: 1)Diffusion 2)Osmosis 3)Facilitated Diffusion Passive Transport Review

48 Active Transport

49 Active Transport  Requires energy or ATP  Moves materials from LOW to HIGH concentration  AGAINST concentration gradient

50 Major Types Endocytosis (including pinocytosis and phagocytosis) Exocytosis Pumps ( including proton pump and sodium-potassium pump)

51 Endocytosis

52 Endocytosis Endocytosis is the process of taking liquids or larger molecules into a cell by engulfing them in a membrane. This is done when the cell membrane makes a pocket around the substance that breaks off inside the cell. This pocket is called a vesicle.

53 Moving the “Big Stuff” Large molecules move materials into the cell by one of three forms of endocytosis Large molecules move materials into the cell by one of three forms of endocytosis.

54 Pinocytosis Endocytosis that involves movement of liquids.Endocytosis that involves movement of liquids. Called “Cell Drinking”Called “Cell Drinking”

55Pinocytosis Most common form of endocytosis Most common form of endocytosis. Takes in dissolved molecules as a vesicle Takes in dissolved molecules as a vesicle.

56 Example of Pinocytosis pinocytic vesicles forming mature transport vesicle Transport across a capillary cell (blue).

57 Endocytosis – Phagocytosis Endocytosis that involves taking in large particles such as food, bacteria, etc. into vesicles Called “Cell Eating”

58 Phagocytosis About to Occur

59 Phagocytosis Phagocytosis - Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue)

60 Exocytosis moving things out essentially the opposite of endocytosis Molecules are moved out of the cell by vesicles that fuse with the plasma membrane. This is how many hormones are secreted and how nerve cells communicate with one another

61 Exocytosis

62 Exocytosis Exocytic vesicle immediately after fusion with plasma membrane.

63 Exocytosis The opposite of endocytosis is exocytosis. Large molecules that are manufactured in the cell are released through the cell membrane. Inside Cell Cell environment

64 Pumps Pumps are similar to facilitated diffusion in that they use transport proteins. Pumps use proteins to move materials against the concentration gradient.

65 Three Types of Pumps Sodium-Potassium Pump (3 Na out, 2 K in) Proton Pump Contractile Vacuole (pumps excess water out of single-cell organisms)

66 Sodium-Potassium Pump 3 Na+ pumped out for every 2 K+ pumped in; creates a membrane potential

67 uk.org.uk/mag/indexmag.html? uk.org.uk/mag/artjun99/vidjuna.html

68 Three Forms of Transport Across the Membrane