1. Chapter 7: Warm-Up 1
Is the plasma membrane symmetrical? Why or why not?
What types of substances cross the membrane the fastest? Why?
Explain the concept of water potential. (Hint: Refer to Lab 1)

2. Chapter 7: Warm-Up 2
What are glycoproteins and glycolipids and what is their function?
How do hydrophilic substances cross the cell membrane?
Why does water move through the bi-layer quickly?

3. Chapter 7: Warm-Up 3
Explain membrane potential and how it affects the cell.
In a U-tube, side A has 4 M glucose and 2 M NaCl. Side B has 2M glucose and 6 M NaCl. Initially, side A is ____ to side B
and side B is ____ to side A. What happens if the membrane is permeable to both solutes? Only permeable to water and NaCl?

4. Chapter 7: Warm-Up 4
Side A in a U tube has 5M sucrose and 3 M glucose. Side B has 2 M sucrose and 1 M glucose. The membrane is permeable to glucose and water only. What happens to each side?

5. Chapter 7: Warm-Up 5
Side A in a U tube has 3 M sucrose and 1 M glucose. Side B has 1 M sucrose and 3 M glucose. The membrane is permeable to glucose and water only. What happens to each side?

6. Membrane Structure and Function
Chapter 7
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Membrane Structure and Function

7. Correlations of text and Big Ideas
7.1 Cellular membranes are fluid mosaics of lipids and proteins
2.B.1 Cell membranes are selectively permeable due to their structure pages
7.2 Membranes structure results in selective permeability
2.B.1 Cell membranes are selectively permeable due to their structure pages

8. What You Must Know: Why membranes are selectively permeable.
The role of phospholipids, proteins, and carbohydrates in membranes.
How water will move if a cell is placed in an isotonic, hypertonic, or hypotonic solution.
How electrochemical gradients are formed.

9. 11/16/2018
Cell Membrane
Plasma membrane is selectively permeable
Allows some substances to cross more easily than others
Fluid Mosaic Model
Fluid: membrane held together by weak interactions
Mosaic: phospholipids, proteins, carbs
Cell Membrane manipulatives help you visualize all of the parts of the cell.
Use the manipulatives as each component is explained

10. Part 1 of Osmosis Diffusion Lab
Review: Cell Size
Why is the size of the cell so very important?
What is the relationship of surface area to volume of the cell so important?
How do cells utilize this relationship?
Part 1 of Osmosis Diffusion Lab

11. Early membrane model (1935) Davson/Danielli – Sandwich model
phospholipid bilayer between 2 protein layers
Problems: varying chemical composition of membrane, hydrophobic protein parts

12. The freeze-fracture method: revealed the structure of membrane’s interior

13. Fluid Mosaic Model

14. 11/16/2018

15. Phospholipids Bilayer Amphipathic = hydrophilic head, hydrophobic tail
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Phospholipids
Bilayer
Amphipathic = hydrophilic head, hydrophobic tail
Hydrophobic barrier: keeps hydrophilic molecules out
Amphipathic means on both (or 2) sides
membrane animation

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Membrane fluidity
Low temps: phospholipids w/unsaturated tails (kinks prevent close packing)
Cholesterol resists changes by:
limit fluidity at high temps
hinder close packing at low temps
Adaptations: bacteria in hot springs (unusual lipids); winter wheat ( unsaturated phospholipids)
What causes the kinks/bends in the HC tails? What does unsaturated tail refer to?

17. Student Question: How does Cholesterol control the membrane fluidity at different temperatures?
Bilipid layer is held by weak hydrophobic interactions and in constant motion
More Saturated = Single bonds = tightly packed = solid at lower temperatures
Unsaturated = less H = double bonds = kinks in hydrophobic tails = less tightly packed = less solid at lower temperatures
Cholesterol interrupts the hydrophobic alignment causing less tight packing = less solid at lower temps but also stabilizes the kinks at higher temps allowing saturated to not liquify at high temps
Summary: Cholesteral minimizes changes in fluidity of the membrane at temperature changes, This maintains membrane fluidity and movement maintaining the cells permeability and enzyme action.

18. Membrane Proteins Integral Proteins Peripheral Proteins
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Membrane Proteins
Integral Proteins
Peripheral Proteins
Embedded in hydrophobic core of membrane
Transmembrane with hydrophilic heads/tails and hydrophobic middles
Determined by freeze fracture
Hydrophobic region consists of stretches of nonpolar amino acids often coiled into apha helices
NOT embedded
Bound to the extracellular or cytoplasmic sides of membrane
Held in place by the cytoskeleton or ECM
Provides stronger framework
extracellular matrix (ECM) is a collection of extracellular molecules secreted by cells that provides structural and biochemical support to the surrounding cells

19. Integral & Peripheral proteins

20. Transmembrane protein structure
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Transmembrane protein structure
Hydrophobic interior
Hydrophilic ends
Do you see the alpha helices of the amino acids? What causes alpha helix in proteins?

21. Some functions of membrane proteins

22. Carbohydrates Function: cell-cell recognition; developing organisms
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Function: cell-cell recognition; developing organisms
Glycolipids, glycoproteins (more GP than GL)
Glyco means of carbohydrates = short sugar chains covalently bonded
Lots of variety of CH ends, location of ECM = cell recognition
Eg. blood transfusions are type-specific:
Blood Type A, B, AB, and O are due to different Glycoproteins on
the outside of the cell
Rejection of transfused
blood is non recognition
of the CH portion of the GP
on the outside of the
transfused blood cells
Membrane carbohydrates may be covalently bonded to lipids (forming glycolipids) or more commonly to proteins (forming glycoproteins)

23. Synthesis and sidedness of membranes Fig 7.10
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Synthesis and sidedness of membranes Fig 7.10
Sidedness (often caused by asymmetric distribution of proteins) of membrane is determined when the membrane is built by the ER and Golgi apparatus

24. 7.2 Selective Permeability
Plasma membrane regulates the cells molecular traffic
through selective permeability.
Small molecules (polar or nonpolar) cross easily (hydrocarbons, hydrophobic molecules, CO2, O2)
Hydrophobic core prevents passage of ions, large polar molecules

25. The Permeability of the Lipid Bilayer
Hydrophobic (nonpolar) molecules, such as hydrocarbons, can dissolve in the lipid bilayer and pass through the membrane rapidly
Polar molecules, such as sugars, do not cross the membrane easily
Makes sense other wises what would happen with the polar matrix the cell is siting
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

26. Transport Proteins Transport proteins allow passage
of hydrophilic substances across the
membrane
Some transport proteins, called channel proteins, have a hydrophilic channel that certain molecules or ions can use as a tunnel
Channel proteins called aquaporins
facilitate the passage of water
Discovered in late 1990s
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

27. Transport Proteins
Other transport proteins, called carrier proteins, bind to molecules and change shape to shuttle them across the membrane
A transport protein is specific for the substance it moves
FORM=FUNCTION
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

28. 7.3 Passive Transport (Fig 7.11)
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7.3 Passive Transport (Fig 7.11)
NO ENERGY needed! (no work done to move substances)
Diffusion down concentration gradient (high  low concentration)
Eg. hydrocarbons, CO2, O2, H2O
Clarify that water molecules in animation don’t just pass through the membrane.
Begin talking about each step of Part 2-4 of the Osmosis Diffusion Lab as each concept is taught.

29. Passive Transport

30. Osmosis: diffusion of H2O across a selectively permeable membrane
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Osmosis: diffusion of H2O across a selectively permeable membrane
How is water moving along its own concentration gradient
Only water can pass
“solute sucks” water to equalize the concentrations
Water diffuses accros a membrane from
down waters own concentration gradient
from high water conc to lower water conc
region of lower solute concentration to higher concentration

31. External environments can be hypotonic, isotonic or hypertonic to internal environments of cell
Less solute in external soln = H2O in
More solute in external soln = H2O out
same
Tonicity = the ability of surrounding soln to cause the cell to gain or loose water.

32. Turgor Pressure flaccid cell turgid cell
How does this relate to blood cell of last slide?

33. In a hypertonic environment, plant cells lose water; eventually, the membrane pulls away from the wall, a usually lethal effect called plasmolysis
Draw this:
Osmotic control in Plant and Animal Cells
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

34. Osmoregulation Control solute & water balance
Most species create an isotonic environment with surroundings: extracellular coating, in correct pond M, etc
Osmoregulation
Control solute & water balance
Contractile vacuole: “bilge pump” forces out fresh water as it enters by osmosis
Eg. paramecium caudatum – freshwater protist

35. Lab: Short-Distance Transport of Water Across Plasma Membranes
To survive, plants must balance water uptake and loss
Osmosis determines the net uptake or water loss by a cell and is affected by solute concentration and pressure
Water potential is a measurement that combines the effects of solute concentration and pressure
Water potential determines the direction of movement of water
Water flows from regions of higher water potential to regions of lower water potential
Potential refers to water’s capacity to perform work
© 2011 Pearson Education, Inc.

36. Ψ = 0 MPa for pure water at sea level and at room temperature
Water potential is abbreviated as Ψ and measured in a unit of pressure called the megapascal (MPa)
Ψ = 0 MPa for pure water at sea level and at room temperature
Consider a U-shaped tube where the two arms are separated by a membrane permeable only to water
Water moves in the direction from higher water potential to lower water potential
Adding solute decreases the water potential
© 2011 Pearson Education, Inc.

37. © 2011 Pearson Education, Inc.

38. Osmosis Diffusion Lab
Water Potential – This is commonly a FRQ

39. Facilitated Diffusion= Passive transport aided by proteins
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Facilitated Diffusion= Passive transport aided by proteins
Transport proteins (channel or carrier proteins) help hydrophilic substance cross
(1) Provide hydrophilic channel or (2) loosely bind/carry molecule across
Ions: (Ca+2) = ion channels
polar molecules (H2O, glucose)
= carrier proteins
Solute moving down its concentration gradient = no E required = passive transport

40. Glucose Transport Protein (carrier protein)

41. 11/16/2018
7.4 Active Transport
Requires ENERGY (ATP)
All by carrier proteins not channel
Proteins transport substances against concentration gradient (low  high conc.)
ex. Na+/K+ pump, proton pump

42. Electrogenic Pumps: generate voltage (net charge flow) across membrane
Na+/K+ Pump
Pump Na+ out, K+ into cell
Nerve transmission +
3 Na+ transported out of the cell For every 2 K+ transported into the cell
Creates a + outer charge

43. Electrogenic Pumps: generate voltage (net charge flow) across membrane all cells have a –cytoplasmic membrane, + ECM = membrane potential
Proton Pump
Pump Na+ out, K+ into cell
Nerve transmission
Push protons (H+) across membrane
Eg. mitochondria (ATP production)
All moves down its concentration gradient
Ions also move down their electrochemical gradient

44. This is coupled transport by a membrane protein
Cotransport: occurs when active transport of a solute drives transport of another solute membrane protein enables “downhill” diffusion of one solute to drive “uphill” transport of other
Eg. sucrose-H+ cotransporter (sugar-loading in plants)
This is coupled transport by a membrane protein

45. Passive vs. Active Transport
Little or no Energy
High  low concentrations
DOWN the concentration gradient
eg. diffusion, osmosis, facilitated diffusion (w/transport protein)
Requires Energy (ATP)
Low  high concentrations
AGAINST the concentration gradient
eg. pumps, exo/endocytosis

47. 7.5 Bulk Transport
Transport of proteins, polysaccharides, large molecules across a membrane
Endocytosis: take in macromolecules, form new vesicles
Exocytosis: vesicles fuse with cell membrane, expel contents

48. Exocytosis Endo/exocytosis
In exocytosis, transport vesicles migrate to the membrane, fuse with it, and release their contents
Many secretory cells use exocytosis to export their products
Endo/exocytosis

49. Types of Endocytosis Endo=enter “pinch” Phagocytosis:
“cellular eating” - solids
Pinocytosis:
“cellular drinking” - fluids
Receptor-Mediated Endocytosis:
Ligands bind to specific receptors on cell surface
“pinch”

50. Fig. 7-20 Figure 7.20 Endocytosis in animal cells PHAGOCYTOSIS
EXTRACELLULAR
FLUID
CYTOPLASM
1 µm
Pseudopodium
Pseudopodium
of amoeba
“Food”or
other particle
Bacterium
Food
vacuole
Food vacuole
An amoeba engulfing a bacterium
via phagocytosis (TEM)
PINOCYTOSIS
0.5 µm
Plasma
membrane
Pinocytosis vesicles
forming (arrows) in
a cell lining a small
blood vessel (TEM)
Vesicle
RECEPTOR-MEDIATED ENDOCYTOSIS
Coat protein
Receptor
Coated
vesicle
Figure 7.20 Endocytosis in animal cells
Coated
pit
Ligand
A coated pit
and a coated
vesicle formed
during
receptor-
mediated
endocytosis
(TEMs)
Coat
protein
Plasma
membrane
0.25 µm

51. You should now be able to: Turn in a full explanation of each item bellow
Define the following terms: amphipathic molecules, aquaporins, diffusion
Explain how membrane fluidity is influenced by temperature and membrane composition
Distinguish between the following pairs or sets of terms: peripheral and integral membrane proteins; channel and carrier proteins; osmosis, facilitated diffusion, and active transport; hypertonic, hypotonic, and isotonic solutions
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

52. Explain how transport proteins facilitate diffusion
Explain how an electrogenic pump creates voltage across a membrane, and name two electrogenic pumps
Explain how large molecules are transported across a cell membrane
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

53. BioFlix Animation Membrane Transport Watch the video
Watch the video
Create an outline for the full animation including all structural and molecular names

54. Create a mind map of the chapter
Place central ideas in the center of the paper
Organize each topic’s detail on a section of the paper near the central idea they relate to. Use boarders, drawings, and color to show separation of topics
Illustrate how central ideas and topics relate with arrows
Fully explain each topic with illustrations
Include detailed molecular and structural names you are required to recall