1. Chapter 3 Cells Physiology
Membrane Transport
-Passive
-Active
Cell Cycle
Protein Synthesis

2. Cellular Physiology: Membrane Transport
Membrane Transport – movement of substance into and out of the cell
Transport is by two basic methods
Passive transport
No energy is required
Active transport
The cell must provide metabolic energy

3. Solutions and Transport
Solution – homogeneous mixture of two or more components
Solvent – dissolving medium
Solutes – components in smaller quantities within a solution

4. Intracellular fluid – nucleoplasm and cytosol
Extracellular fluid – fluid on the exterior of the cell
Interstitial fluid – only the fluid that surrounds the cells

5. Selective Permeability
The plasma membrane allows some materials to pass while excluding others
This permeability includes movement into and out of the cell

6. Passive Processes
What determines whether or not a substance can passively permeate a membrane?
Lipid solubility of substance
Channels of appropriate size
Carrier proteins
PLAY
Animation: Membrane Permeability

7. Passive Transport Processes
Diffusion
Particles tend to distribute themselves evenly within a solution (reach equilibrium)
Movement is from high concentration to low concentration, or down a concentration gradient
Figure 3.8

8. Passive Transport Processes
Types of diffusion
Simple diffusion
(Dialysis)
Unassisted process
Solutes are lipid-soluble materials or small enough to pass through membrane pores

9. Passive Transport Processes - Diffusion
Nonpolar lipid- soluble (hydrophobic) substances diffuse directly through the phospholipid bilayer
PLAY
Animation: Diffusion
(a) Simple diffusion of fat-soluble molecules
directly through the phospholipid bilayer

10. (a) Simple diffusion of fat-soluble molecules
Extracellular fluid
Lipid-
soluble
solutes
Cytoplasm
(a) Simple diffusion of fat-soluble molecules
directly through the phospholipid bilayer
Figure 3.7a

11. Passive Transport Processes
Facilitated diffusion
Substances require a protein carrier for passive transport.
Still moves with the concetration gradient.

12. Diffusion through the Plasma Membrane
Figure 3.9

13. PhysioEx Lab
Simple Diffusion
Facilitated Diffusion

14. Passive Transport Processes
Types of diffusion
Osmosis – simple diffusion of water across a semipermeable membrane

15. Passive Processes: Osmosis
Water diffuses through plasma membranes:
Through the lipid bilayer
Through protein channels

16. (d) Osmosis, diffusion of a solvent such as
Water
molecules
Lipid
billayer
Aquaporin
(d) Osmosis, diffusion of a solvent such as
water through a specific channel protein
(aquaporin) or through the lipid bilayer
Figure 3.7d

17. Passive Processes: Osmosis
Water concentration is determined indirectly by solute concentration because solute particles displace water molecules
Osmolarity: The measure of total concentration of solute particles
When solutions of different osmolarity are separated by a membrane, osmosis occurs until equilibrium is reached

18. Solute and water molecules move down their concentration gradients
(a) Membrane permeable to both solutes and water
Solute and water molecules move down their concentration gradients
in opposite directions. Fluid volume remains the same in both compartments.
Left
compartment:
Solution with
lower osmolarity
Right
compartment:
Solution with
greater osmolarity
Both solutions have the
same osmolarity: volume
unchanged
H2O
Solute
Solute
molecules
(sugar)
Membrane
Figure 3.8a

19. (b) Membrane permeable to water, impermeable to solutes
Solute molecules are prevented from moving but water moves by osmosis.
Volume increases in the compartment with the higher osmolarity.
Both solutions have identical
osmolarity, but volume of the
solution on the right is greater
because only water is
free to move
Left
compartment
Right
compartment
H2O
Solute
molecules
(sugar)
Membrane
Figure 3.8b

20. Importance of Osmosis
When osmosis occurs, water enters or leaves a cell
Change in cell volume disrupts cell function
PLAY
Animation: Osmosis

21. PhysioEx Lab
Osmosis

22. Get Laptops ready to go.

23. Tonicity
Tonicity: The ability of a solution to cause a cell to shrink or swell
Isotonic: A solution with the same solute concentration as that of the cytosol
Hypertonic: A solution having greater solute concentration than that of the cytosol
Hypotonic: A solution having lesser solute concentration than that of the cytosol

25. Figure 3.9 (a) Isotonic solutions (b) Hypertonic solutions
(c) Hypotonic solutions
Cells retain their normal size and
shape in isotonic solutions (same
solute/water concentration as inside
cells; water moves in and out).
Cells lose water by osmosis and
shrink in a hypertonic solution
(contains a higher concentration
of solutes than are present inside
the cells).
Cells take on water by osmosis until
they become bloated and burst (lyse)
in a hypotonic solution (contains a
lower concentration of solutes than
are present in cells).
Figure 3.9

26. Passive Transport Processes
Filtration
Water and solutes are forced through a membrane by fluid, or hydrostatic pressure
A pressure gradient must exist
Solute-containing fluid is pushed from a high pressure area to a lower pressure area

27. Active Transport Processes
Transport substances that are unable to pass by diffusion
They may be too large
They may not be able to dissolve in the fat core of the membrane
They may have to move against a concentration gradient
Two common forms of active transport
Solute pumping
Bulk transport

28. Active Transport Processes
Solute pumping
Amino acids, some sugars and ions are transported by solute pumps
ATP energizes protein carriers, and in most cases, moves substances against concentration gradients

29. Active Transport Processes
Figure 3.10

30. Active Transport Processes
Bulk transport
Exocytosis
Moves materials out of the cell
Material is carried in a membranous vesicle
Vesicle migrates to plasma membrane
Vesicle combines with plasma membrane
Material is emptied to the outside

31. Active Transport Processes
Figure 3.11

32. Active Transport Processes
Bulk transport
Endocytosis
Extracellular substances are engulfed by being enclosed in a membranous vesicle
Types of endocytosis
Phagocytosis – cell eating
Pinocytosis – cell drinking

33. Active Transport Processes
Figure 3.12

34. Passive Membrane Transport – Review
Process
Energy Source
Example
Simple diffusion
Kinetic energy
Movement of O2 through membrane
Facilitated diffusion
Movement of glucose into cells
Osmosis
Movement of H2O in & out of cells
Filtration
Hydrostatic pressure
Formation of kidney filtrate

35. Active Membrane Transport – Review
Process
Energy Source
Example
Active transport of solutes
ATP
Movement of ions across membranes
Exocytosis
Neurotransmitter secretion
Endocytosis
White blood cell phagocytosis
Pinocytosis
Absorption by intestinal cells

36. Osmosis Lab

37. Osmosis Lab
Complete the lab calculations, graph and questions at home. Formal report due Wednesday, 9/26

38. Cell Life Cycle Cells have two major periods Interphase Cell grows
Cell carries on metabolic processes
Cell division
Cell replicates itself
Function is to produce more cells for growth and repair processes

39. Events of Cell Division
Mitosis
Division of the nucleus
Results in the formation of two daughter nuclei
Cytokinesis
Division of the cytoplasm
Begins when mitosis is near completion
Results in the formation of two daughter cells

40. Preparations for DNA Replication
Interphase
No cell division occurs
The cell carries out normal metabolic activity and growth

41. DNA Replication
Genetic material duplicated and readies a cell for division into two cells
Occurs toward the end of interphase
DNA uncoils and each side serves as a template
Figure 3.13

44. Stages of Mitosis Prophase Mitosis begins here
First part of cell division
Centrioles migrate to the poles

47. Stages of Mitosis Metaphase
Spindle from centrioles are attached to chromosomes at the centromeres that are aligned in the center of the cell

48. The chromatids appear to repell each other, taking the shape of an X.

51. Stages of Mitosis Anaphase
Daughter chromosomes are pulled toward the poles
The cell begins to elongate

52. Anaphase
The separated sister chromatids (daughter chromosomes) appear to be pulled apart by the centromeres.

55. Telophase Daughter nuclei begin forming
A cleavage furrow (for cell division) begins to form

56. Telophase
When the daughter chromosomes reach the end of the spindle.
new nucleus forms.

59. Cytokinesis
plasma membrane constricts (cleavage furrow) and the cytoplasm divides, called cytokinesis.
The two resulting cells are called daughter cells.

61. Stages of Mitosis
Figure 3.14; 1

62. Stages of Mitosis
Figure 3.14; 2

63. Online Mitosis Lab

64. Protein Synthesis
Gene – DNA segment that carries a blueprint for building one protein
Proteins have many functions
Building materials for cells
Act as enzymes (biological catalysts)
RNA is essential for protein synthesis

65. Role of RNA Messenger RNA (mRNA) Transfer RNA (tRNA)
Carries the instructions for building a protein from the nucleus to the ribosome
Has 3 base codons
Transfer RNA (tRNA)
Transfers appropriate amino acids to the ribosome for building the protein
Has 3 base anticodons
Ribosomal RNA (rRNA)
Helps form the ribosomes where proteins are built

66. Transcription and Translation
Transfer of information from DNA’s base sequence to the complimentary base sequence of mRNA. In the nucleus
Translation
Base sequence of nucleic acid is translated to an amino acid sequence outside the nucleus
Amino acids are the building blocks of proteins
More
Translation

67. Protein Synthesis
Figure 3.15