1. Membrane Structure and Transport through cell membranes

2. Plasma Membrane
Is the boundary that separates the living cell from its nonliving surroundings
Selectively Permeable (chooses what may cross the membrane)
Fluid mosaic of lipids and proteins
Lipid bilayer
Contains embedded proteins

4. Phospholipids Are the most abundant lipid in the plasma membrane
Are amphipathic, containing both hydrophilic (head) and hydrophobic regions (tails)
Head composed of phosphate group attached to one carbon of glycerol is hydrophilic
Two fatty acid tails are hydrophobic

5. Phospholipid Bilayer
Hydrophilic
head
Hydrophobic tail
WATER

6. Hydrophobic region of protein
Singer and Nicolson
In 1972, Singer and Nicolson, Proposed that membrane proteins are dispersed and individually inserted into the phospholipid bilayer of the plasma membrane
Phospholipid
bilayer
Hydrophilic region
of protein
Hydrophobic region of protein

7. Fluid Mosaic Model
A membrane is a fluid structure with a “mosaic” of various proteins embedded in it when viewed from the top
Phospholipids can move laterally a small amount and can “flex” their tails
Membrane proteins also move side to side or laterally making the membrane fluid

8. Freeze-fracture studies of the plasma membrane support the fluid mosaic model of membrane structure
A cell is frozen and fractured with a knife. The fracture plane often follows the hydrophobic interior of a membrane, splitting the phospholipid bilayer into two separated layers. The membrane proteins go wholly with one of the layers.

9. The Fluidity of Membranes
Phospholipids in the plasma membrane Can move within the bilayer two ways
Lateral movement
(~107 times per second)
Flip-flop
(~ once per month)

10. The Fluidity of Membranes
The type of hydrocarbon tails in phospholipids Affects the fluidity of the plasma membrane
Fluid
Viscous
Unsaturated hydrocarbon
tails with kinks
Saturated hydro-
Carbon tails

11. The Fluidity of Membranes
The steroid cholesterol Has different effects on membrane fluidity at different temperatures
Figure 7.5
Cholesterol

12. Membrane Proteins and Their Functions
A membrane is a collage of different proteins embedded in the fluid matrix of the lipid bilayer
Fibers of
extracellular
matrix (ECM)

13. Types of Membrane Proteins
Integral proteins
Penetrate the hydrophobic core of the lipid bilayer
Are often transmembrane proteins, completely spanning the membrane
EXTRACELLULAR
SIDE

14. Transport Proteins Transport proteins
Allow passage of hydrophilic substances across the membrane

15. Types of Membrane Proteins
Peripheral proteins
Are appendages loosely bound to the surface of the membrane

16. The Role of Membrane Carbohydrates in Cell-Cell Recognition
Is a cell’s ability to distinguish one type of neighboring cell from another
Membrane carbohydrates
Interact with the surface molecules of other cells, facilitating cell-cell recognition

17. Transport through cell membranes
The phospholipid bilayer is a good barrier around cells, especially to water soluble molecules. However, for the cell to survive some materials need to be able to enter and leave the cell.
There are 2 basic ways:
Passive Transport – uses no cellular energy and goes down the concentration gradient
Active Transport – uses cellular energy and goes against the concentration gradient

18. Diffusion of liquids

19. Diffusion is the net movement of molecules (or ions) from a region of their high concentration to a region of their lower concentration. The molecules move down a concentration gradient. Molecules have kinetic energy, which makes them move about randomly. As a result of diffusion molecules reach an equilibrium where they are evenly spread out. This is when there is no net movement of molecules from either side.

20. AS Biology, Cell membranes and Transport
DIFFUSION
Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural kinetic energy.
AS Biology, Cell membranes and Transport

21. Diffusion of Bromine

22. Diffusion of Bromine

23. Diffusion through a membrane
Cell membrane
Outside cell
Inside cell

24. Diffusion through a membrane
Cell membrane
diffusion
Outside cell
Inside cell

25. Diffusion through a membrane
Cell membrane
Outside cell
Inside cell
EQUILIBRIUM

27. AS Biology, Cell membranes and Transport``
AS Biology, Cell membranes and Transport

28. Osmosis
‘The diffusion of water from an area of high concentration of water molecules to an area of low concentration of water across a partially permeable membrane.’

29. Molecules that diffuse through cell membranes
Oxygen – Non-polar so diffuses very quickly.
Carbon dioxide – Polar but very small so diffuses quickly.
Water – Polar but also very small so diffuses quickly.

30. Osmosis CONCENTRATED SOLUTION DILUTE SOLUTION
Cell membrane partially permeable.
Sugar molecule
VERY Low conc. of water molecules. High water potential.
VERY High conc. of water molecules. High water potential.
Outside cell
Inside cell

31. Osmosis Cell membrane partially permeable.
Low conc. of water molecules. High water potential.
OSMOSIS
High conc. of water molecules. High water potential.
Outside cell
Inside cell

32. AS Biology, Cell membranes and Transport
Osmosis
Cell membrane partially permeable.
OSMOSIS
Outside cell
Inside cell
EQUILIBRIUM. Equal water concentration on each side. Equal water potential has been reached. There is no net movement of water
AS Biology, Cell membranes and Transport

34. AS Biology, Cell membranes and Transport

35. 3 types of solutions
Isotonic – concentrations of solute and water are the same
Hypertonic – where there is a greater concentration of solute (sugar, salt) and less water
Hypotonic – where there is less solute and more water.

36. Two parts to a solution
Solute – What is dissolved
Solvent – what the solute is being dissolved in (usually water)

39. Which picture shows RBCs in a hypertonic, isotonic and hypotonic solution?
A B C D E

40. What determines the rate of diffusion? There 4 factors:
The steepness of the concentration gradient. The bigger the difference between the two sides of the membrane the quicker the rate of diffusion.
Temperature. Higher temperatures give molecules or ions more kinetic energy. Molecules move around faster, so diffusion is faster.
The surface area. The greater the surface area the faster the diffusion can take place. This is because the more molecules or ions can cross the membrane at any one moment.
The type of molecule or ion diffusing. Large molecules need more energy to get them to move so they tend to diffuse more slowly. Non-polar molecules diffuse more easily than polar molecules because they are soluble in the non polar phospholipid tails.

41. Facilitated diffusion
Large polar molecules such as glucose and amino acids, cannot diffuse across the phospholipid bilayer. Also ions such as Na+ or Cl- cannot pass.
These molecules pass through protein channels instead. Diffusion through these channels is called FACILITATED DIFFUSION.
Movement of molecules is still PASSIVE just like ordinary diffusion, the only difference is, the molecules go through a protein channel instead of passing between the phospholipids.

43. Facilitated Diffusion through a membrane
Cell membrane
Protein channel
Outside cell
Inside cell

44. Facilitated Diffusion through a membrane
Cell membrane
diffusion
Protein channel
Outside cell
Inside cell

45. Facilitated Diffusion through a membrane
Cell membrane
diffusion
Protein channel
Outside cell
Inside cell
EQUILIBRIUM

46. Facilitated Diffusion: Molecules will randomly move through the opening like pore, by diffusion. This requires no energy, it is a PASSIVE process. Molecules move from an area of high concentration to an area of low conc.

47. Facilitated diffusion

48. Dialysis
Dialysis is transport of a solute. This process is extremely important in the human kidneys for filtering out waste products.

55. Endocytosis is the case when a molecule causes the cell membrane to bulge inward, forming a vesicle. Phagocytosis is the type of endocytosis where an entire cell is engulfed. Pinocytosis is when the external fluid is engulfed. Receptor-mediated endocytosis occurs when the material to be transported binds to certain specific molecules in the membrane. Examples include the transport of insulin and cholesterol into animal cells.

56. Endocytosis

57. Cell Membrane - Function - Endocytosis The cell membrane can also engulf structures that are much too large to fit through the pores in the membrane proteins this process is known as endocytosis. In this process the membrane itself wraps around the particle and pinches off a vesicle inside the cell. In this animation an amoeba engulfs a food particle.

58. Three Types of Endocytosis
In phagocytosis, a cell
engulfs a particle by
Wrapping pseudopodia
around it and packaging
it within a membrane-
enclosed sac large
enough to be classified
as a vacuole. The
particle is digested after
the vacuole fuses with a
lysosome containing
hydrolytic enzymes.
PHAGOCYTOSIS
In pinocytosis, the cell
“gulps” droplets of
extracellular fluid into tiny
vesicles. It is not the fluid
itself that is needed by the
cell, but the molecules
dissolved in the droplet.
Because any and all
included solutes are taken
into the cell, pinocytosis is nonspecific in the substances it transports.

59. RECEPTOR-MEDIATED ENDOCYTOSIS
Ligand
Coat protein
Coated
pit
vesicle
A coated pit
and a coated
vesicle formed
during
receptor-
mediated
endocytosis
(TEMs).
Plasma
membrane
Coat
protein

61. Exocytosis The opposite of endocytosis is exocytosis
Exocytosis The opposite of endocytosis is exocytosis. Large molecules that are manufactured in the cell are released through the cell membrane.

62. Vesicle-mediated transport Vesicles and vacuoles that fuse with the cell membrane may be utilized to release or transport chemicals out of the cell or to allow them to enter a cell. Exocytosis is the term applied when transport is out of the cell.

63. Active Transport The sodium-potassium pump
Is one type of active transport system (page 212)
Na+ binding stimulates
phosphorylation by ATP.
Na+
Cytoplasmic Na+ binds to
the sodium-potassium pump. 1
K+ is released and Na+
sites are receptive again;
the cycle repeats.
Phosphorylation causes the
protein to change its conformation, expelling Na+ to the outside.
Extracellular K+ binds to the
protein, triggering release of the
Phosphate group.
Loss of the phosphate
restores the protein’s
original conformation.
CYTOPLASM
[Na+] low
[K+] high P
ATP
ADP K+
[Na+] high
[K+] low
EXTRACELLULAR
FLUID P
P i

64. Bulk Transport
Bulk transport across the plasma membrane occurs by exocytosis and endocytosis
Large proteins
Cross the membrane by different mechanisms

65. To construct a cell membrane: http://www. wisc-online

67. In the human body…
Kidney (page 870)

68. Lungs (page 877) http://health. howstuffworks

69. Neuron (page 877) http://people. eku. edu/ritchisong/301notes2

70. Human Respiratory System Diagram
Title Page
Human Respiratory System Diagram
Nasal Passage
Pharynx
Trachea
Bronchus
Bronchiole
Alveoli

71. Respiratory Overview Review
CO2
Air Passing over the mucus membrane of the nasal cavity is moistened, warmed, and filtered
Inside the lungs the Bronchi branch into small tubes called bronchioles
The Pharynx, or throat, is located where passages from the nose and mouth came together.
Respiratory Overview Review
At the end of the bronchioles are bunches of alveoli, air sacs, arranged like grapes on a stem
Air enters the trachea, or wind pipe which leads to and from the lungs
If one lobe is injured or diseased, the other lobes may be able to function normally
The trachea divides into two tubes called bronchi JH

72. Alveoli Picture Carbon Dioxide is dropped off Wall of the air sac
Here is a close
up picture of
your Alveoli
and a Capillary
surrounding it.
Capillary
Red Blood Cell
Oxygen is picked up
Carbon Dioxide is dropped off
Wall of the air sac MB

73. Fun Facts * The right lung is slightly larger than the left.
* At rest, the body takes in and breathes out about 10 liters of air each minute.
* The right lung is slightly larger than the left.
* The highest recorded "sneeze speed" is 165 km per hour.
* The surface area of the lungs is roughly the same size as a tennis court.
* The capillaries in the lungs would extend 1,600 kilometers if placed end to end.
* We lose half a liter of water a day through breathing. This is the water vapor we see when we breathe onto glass.
* A person at rest usually breathes between 12 and 15 times a minute.
* The breathing rate is faster in children and women than in men.