1. Chapter 3 Lecture Outline See PowerPoint Image Slides
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2. Modern Cell Theory All organisms composed of cells and cell products.
Cell is the simplest structural and functional unit of life.
Organism’s structure and functions are due to the activities of its cells.
Cells come only from preexisting cells.
Cells of all species have many fundamental similarities.

3. General Cell Structure
Light microscope reveals plasma membrane, nucleus and cytoplasm
Resolution of electron microscopes reveals ultrastructure
organelles, cytoskeleton and cytosol

4. Plasma Membrane Cell membrane Cytosol/cytoplasm Nuclear envelope
Nucleus
Plasma
Membrane
Cell membrane
Smooth endoplasmic
reticulum
Cytosol/cytoplasm
Secretion being released
from cell by exocytosis
Microvilli
Figure 3.2

5. Plasma Membrane
Oily film of lipids with diverse proteins embedded in it

6. Plasma Membrane - Fluid Mosaic Model
Separates intracellular fluids from extracellular fluids
Semipermeable membrane
Figure 3.3

7. Lysosome 1.Cytosol/cytoplasm Chromatin Nuclear envelope 2.Nucleus
Nucleolus
2.Nucleus
Plasma
membrane
3. Smooth endoplasmic
reticulum
1.Cytosol/cytoplasm
Lysosome
4. Mitochondrion
Centrioles
5.Centrosome
matrix
Rough
endoplasmic
reticulum
Ribosomes
Golgi apparatus
Secretion being released
from cell by exocytosis
Microtubule
Figure 3.2

8. Membrane Protein Functions
Receptors, enzymes, channel proteins (gates), cell-identity markers, cell-adhesion molecules

9. Cystic Fibrosis Hereditary disease
chloride pumps fail to create adequate saline layer under mucus
Thick mucus plugs pancreatic ducts and respiratory tract
life expectancy of 30

10. Extensions of membrane (1-2m) Function
Microvilli
(brush border)
Extensions of membrane (1-2m)
Function
increase surface area for absorption

11. Simple diffusion – nonpolar and lipid-soluble substances
Passive vs Active Processes Thermal Agitation/Brownian movement Passive Membrane Transport: Diffusion
Simple diffusion – nonpolar and lipid-soluble substances
Diffuse directly through the lipid bilayer
Diffuse through channel proteins

12. Diffusion Through the Plasma Membrane
Extracellular fluid
Small lipid-
insoluble
solutes
Lipid-
soluble
solutes
Lipid-insoluble
solutes
Water
molecules
Lipid
bilayer
Cytoplasm
(a) Simple diffusion
directly through the
phospholipid bilayer
(b) Carrier-mediated facilitated
diffusion via protein carrier
specific for one chemical; binding
of substrate causes shape change
in transport protein
(c) Channel-mediated
facilitated diffusion
through a channel
protein; mostly ions
selected on basis of
size and charge
(d) Osmosis, diffusion
through a specific
channel protein
(aquaporin) or
through the lipid
bilayer
Figure 3.7

13. Diffusion Through the Plasma Membrane
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

14. Facilitated Diffusion
Transport of solute across membrane down its concentration gradient
No ATP used
Solute binds to carrier, it changes shape then releases solute on other side of membrane

15. Passive Membrane Transport: Osmosis
Occurs when the concentration of a solvent is different on opposite sides of a membrane
Diffusion of water across a semipermeable membrane
Osmolarity – total concentration of solute particles in a solution
Tonicity – how a solution affects cell volume

16. Diffusion Through the Plasma Membrane
Water
molecules
Lipid
bilayer
(d) Osmosis, diffusion through
a specific channel protein
(aquaporin) or through the
lipid bilayer
Figure 3.7

17. Diffusion of water through a membrane
Osmosis
Diffusion of water through a membrane
from area of more water to area of less water
Aquaporins = channel proteins specialized for osmosis

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

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

20. Effects of Solutions of Varying Tonicity
Isotonic – solutions with the same solute concentration as that of the cytosol
Hypertonic – solutions having greater solute concentration than that of the cytosol
Hypotonic – solutions having lesser solute concentration than that of the cytosol

21. Effects of Tonicity on RBCs
Hypotonic, isotonic and hypertonic solutions affect the fluid volume of a red blood cell. Notice the crenated and swollen cells.

22. Passive Membrane Transport: Filtration
The passage of water and solutes through a membrane by hydrostatic pressure
Pressure gradient pushes solute-containing fluid from a higher-pressure area to a lower-pressure area

23. ACTIVE PROCESSES require ATP utilization by cell
ACTIVE TRANSPORT – moving against the concentration gradient
atom/ion/molecule moves from lower concentration to higher
EXAMPLE: Na+/K+ PUMP establishes excitable/polarized membrane
Exterior of cell has higher concentration of Na+
Interior of cell has higher concentration of K+

24. Sodium-Potassium Pump
Needed because Na+ and K+ constantly leak through membrane
half of daily calories utilized for pump
One ATP utilized to exchange three Na+ pushed out for two K+ brought in to cell

25. Figure 3.10 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
Figure 3.10

26. Functions of Na+ -K+ Pump
Regulation of cell volume
“fixed anions” attract cations causing osmosis
cell swelling stimulates the Na+- K+ pump to  ion concentration,  osmolarity and cell swelling
Heat production (thyroid hormone increase # of pumps; heat a by-product)
Maintenance of a membrane potential in all cells
pump keeps inside negative, outside positive
Secondary active transport (No ATP used)
steep concentration gradient of Na+ and K+ maintained across the cell membrane
carriers move Na+ with 2nd solute easily into cell
SGLT saves glucose in kidney

27. Exocytosis –transport out of cell Endocytosis –transport into cell
Vesicular Transport
Transport large particles or fluid droplets through membrane in vesicles
uses ATP
Exocytosis –transport out of cell
Endocytosis –transport into cell
phagocytosis – engulfing large particles
pinocytosis – taking in fluid droplets
receptor mediated endocytosis – taking in specific molecules bound to receptors

28. Phagocytosis or “Cell-Eating”
Keeps tissues free of debris and infectious microorganisms.

29. Pinocytosis or “Cell-Drinking”
Taking in droplets of ECF
occurs in all human cells
Membrane caves in, then pinches off into the cytoplasm as pinocytotic vesicle

30. Transcytosis Transport of a substance across a cell
Receptor mediated endocytosis moves it into cell and exocytosis moves it out the other side
insulin

31. Receptor Mediated Endocytosis

32. Exocytosis
Secreting material or replacement of plasma membrane