1. Body Fluids & Membrane Transport
Intracellular
Extracellular:
Interstitial (intercellular): derived from blood
Plasma: blood component found within vessels
Cerebrospinal fluid: bathing brain & spinal cord
Body cells are bathed in the interstitial fluid
Interstitial fluid contains substances needed by cells
Substances have to be moved selectively across the cell membrane

2. Two main ways of transport:
Types of Transport
Two main ways of transport:
Passive processes:
No energy input needed form the cell
Active processes:
The cell provide metabolic energy (ATP)

3. Passive Transport Two main types of passive transport: Diffusion:
Particles move along concentration gradient
Driven by kinetic energy of moving molecules
In a closed system, equilibrium (equal movement) is reached
Filtration:
Occurs only across capillary walls
Filtrate (containing solute) moves along pressure gradient
Driven by hydrostatic (fluid) pressure

4. Passive Transport: Diffusion
Two types :
Simple diffusion
Facilitated diffusion
Simple diffusion:
Direct substance diffusion through the lipid bilayer:
Nonpolar and lipid soluble substances
They include O2, CO2, and fat soluble vitamins
Simple diffusion of water is called osmosis

5. Complete and explain why?
O2 always diffuses from ____ to ______. (blood, tissue)
CO2 always diffuses from ____ to _____. (blood, tissue)

6. Simple Diffusion Through the Plasma Membrane
Extracellular fluid
Lipid-
soluble
solutes
Cytoplasm
(a) Simple diffusion
directly through the
phospholipid bilayer
Figure 3.7

7. Passive Transport: Facilitated Diffusion
For molecules unable to pass thru the lipid bilayer
Facilitated passage is thru one of the following:
Specific binding to a protein carrier (shape change)
Ex: amino acids and glucose
Water-filled protein channels (size & charge)
Ex: water and ions

8. Facilitated Diffusion: Carrier Mediated “specific binding”
Lipid-insoluble
solutes
(b) Carrier-mediated facilitated
diffusion via protein carrier
specific for one chemical; binding
of substrate causes shape change
in transport protein
Figure 3.7

9. Facilitated Diffusion: Channel Mediated
Small lipid-
insoluble
solutes
(c) Channel-mediated facilitated
diffusion through a channel
protein; mostly ions selected
on basis of size and charge
Figure 3.7

10. Passive Membrane Transport: Osmosis
Occurs when water concentration is different on opposite sides of a semipermeable membrane
Water molecules pass:
Thru transmembrane protein (aquaporins) channels
Directly thru bilayer lipid (???)
Osmolarity:
The total concentration of all solute particles in a solution
Tonicity
Ability of a solution to change the shape or tone of cells by changing their internal water volume

11. Simple Diffusion: Osmosis
Water
molecules
Lipid
bilayer
(d) Osmosis, diffusion of water through a specific channel protein (aquaporin) or through the lipid bilayer
Figure 3.7

12. Effect of Membrane Permeability on Diffusion and Osmosis
Figure 3.8a

13. Effect of Membrane Permeability on Diffusion and Osmosis
Figure 3.8b

14. Passive Membrane Transport: Filtration
Passage of water and solutes through a membrane
Driving force is hydrostatic (fluid) pressure
Pressure gradient pushes solute & fluid from:
High pressure area to low pressure area
Occurs only across capillary walls
Ex. Transport in kidneys

15. Effects of Solutions of Varying Tonicity
Isotonic solution:
A solution with the same concentrations of nonpenetrating solutes as those of the cytosol (0.9% saline or 5% glucose)
Hypertonic solution:
A solution with a greater concentration of nonpenetrating solutes than that in the cytosol
Hypotonic solution:
A solution having lesser nonpenetrating solute concentration than that in the cytosol

16. Uses ATP to move solutes across a membrane Two types:
Active Transport
Uses ATP to move solutes across a membrane
Two types:
Active transport:
Requires carrier proteins
Vesicular transport:
Vesicle formation
Used for macromolecules and fluid transport
Uses ATP (sometimes GTP)
Ex: Exocytosis, endocytosis, transcytosis, vesicular trafficking

17. Types of Active Transport
Primary active transport:
Hydrolysis of ATP
Phosphorylation of the transport protein
Conformational change of protein
Bound solute pumped across membrane
Secondary active transport
Indirect use of an active pump (Na+-K+ pump) to drive the transport of other solutes
Energy is stored in ionic gradient created by the pump

18. Active Transport (Primary)
Cytoplasm
Extracellular fluid
K+ is released and
Na+ sites are ready to
bind Na+ again; the
cycle repeats.
Cell
ADP
Phosphorylation
causes the
protein to
change its shape.
Concentration gradients
of K+ and Na+
The shape change
expels Na+ to the
outside, and
extracellular K+ binds.
Loss of phosphate
restores the original
conformation of the
pump protein.
K+ binding triggers
release of the
phosphate group.
Binding of cytoplasmic
Na+ to the pump protein
stimulates phosphorylation
by ATP.
Na+ K+
ATP P Pi
Note that:
[Na+] is higher extracellularly than intracellularly
[K+] is higher intracellularly than extracellularly
Na+ has three binding sites
K+ has two binding sites
Figure 3.10

19. Active Transport (Secondary)
Figure 3.11

20. Vesicular Transport
Transport of large particles and macromolecules across plasma membranes
Exocytosis
Moves substance from the cell interior to the extracellular space
Endocytosis
Enables large particles and macromolecules to enter the cell

21. Exocytosis
Figure 3.12a

22. Vesicular trafficking
Vesicular Transport
Transcytosis
Moving substances:
Into the cell,
Across the cell, and
Then out of a cell
Vesicular trafficking
Moving substances from one area in the cell to another

23. Vesicular Transport: Types of Endocytosis
There are three types of endocytosis; all use protein (clathrin)-coated vesicles
Phagocytosis (cell eating):
Pseudopods engulf and internalize solid substances into the cell
Fluid-phase endocytosis (pinocytosis “cell drinking”):
Plasma membrane infolds, bringing extracellular fluid containing dissolved solutes into the cell
Receptor-mediated endocytosis:
Specific endocytosis using special membrane proteins

24. Phagocytosis
Figure 3.13b

25. The
Cell Cycle

26. Cell Cycle Interphase Mitotic phase
Growth (G1), synthesis (S), growth (G2)
Mitotic phase
Mitosis and cytokinesis
Figure 3.30

27. Interphase G0: G1 (gap 1): S (synthetic): G2 (gap 2):
Cells that permanently cease dividing
G1 (gap 1):
Metabolic activity and vigorous growth
S (synthetic):
DNA replication
G2 (gap 2):
Preparation for division

28. DNA Replication Means synthesis of new DNA (duplication)
Occurs during the interphase of the cell cycle
DNA helices begin unwinding
Helicase exposes complementary strands
Each nucleotide strand serves as a template
DNA polymerase III is the enzyme for synthesis
It adds complementary nucleotides to the template

29. DNA Replication
Figure 3.31

30. Cell Division Essential for: Mitosis: Cytokinesis: Body growth
Tissue repair
Mitosis:
Nuclear division
Cytokinesis:
Division of the cytoplasm

31. Types of Cell Division Mitotic: Meitic: Body growth Tissue repair
Daughter cells have parental chromosome number (dipoid )
Meitic:
Gamete formation
Daughter cells have half the parental chromosome number (haploid)

32. The phases of mitosis are:
Prophase
Metaphase
Anaphase
Telophase

33. Cytoplasm is pinched into two parts after mitosis ends
Cytokinesis
Cleavage furrow:
formed in late anaphase by contractile ring
Cytoplasm is pinched into two parts after mitosis ends

34. Early and Late Prophase
Asters:
Seen as chromatin condenses into chromosomes
Anchors spindle to cell membrane
Nucleoli:
Disappear
Centriole Pairs:
Separate and migrate to the poles
Organize the mitotic spindle

35. Early &Late Prophase
Figure

36. Metaphase
Centromeres aligned at the exacte quator of the cell
Chromosomes arrange along a plane midway between the poles
This arrangement is called the metaphase plate

37. Anaphase
Centromeres of the chromosomes split
Proteins pull chromosomes toward poles

38. Telophase and Cytokinesis
New sets of chromosomes extend into chromatin
New nuclear membrane forms
Nucleoli reappear
Generally cytokinesis completes cell division

39. Break Slide
Fri, Sep. 14,’12