Physiology is the science of life

1. Physiology of cells and body
tissues
Dr. Ramadan Saad
PHSL222 Principles of

2. How Substances Enter and Leave the
Cell

3. How Substances Enter and Leave the
Cell

4. Plasma membrane is used to maintain homeostasis (maintain a
constant internal environment)
Plasma Membrane = “selectivelypermeable” (letscertain things in &
keeps othersout)
Made up a phospholipidbilayer and proteins
Phospholipidshavehydrophilicheadsandhydrophobictails
Proteinshelpmovelargemoleculesor aidincellrecognition

5. Peripheral proteins that are attached on the
surface of the membrane(inner or outer)
Integral proteins are embedded in the
membrane but do not completely cross
through the membrane
Transmembrane proteins that completely
cross the membrane and can serve as
transport or channel proteins
Three types of membrane proteins

6. Types of CellTransport
2 MainTypes:
Passive Transport – movement of a substance througha cell
membrane without using any energy
Active Transport - using energy to transport particles through
a membrane against a concentration gradient (lesser
concentration to greater concentration)

7. Types of Passive Transport
1. Simple Diffusion= movement of particlesfromhighconcentrationto lowconcentration
•differenceinconcentrationiscalleda concentrationgradient
•diffusionoccursuntilequilibriumis reached.
•Fat solublemoleculesandionsaretransportedby thismechanism.
2. Facilitated Diffusion = transportof particlesthrougha membrane by a channelprotein(Noenergyneeded!)
•Typesof transportProteins
Channelproteinsare embeddedin the cellmembrane & have a pore for materialsto cross
Carrierproteins can change shape to move materialfromone sideof themembrane to theother
Examples: Glucose or amino acids moving from blood into a cell.

8. Passive Transport Processes (No cellular energy
expended)

9. Facilitated diffusion

10. Diffusion through a Membrane
10
Cell membrane
Solute moves DOWN concentration gradient
(HIGH to LOW)

13. The rate of diffusion of a substance
depends on :
1) Concentration gradient of the substance across
the membrane.
2) Surface area of the membrane.
3) ↑ surface area over which diffusion can take
place, ↑ diffusion rate
4) Permeability of the membrane: Increased
permeability increase diffusion rate.
5) Temperature
– ↑ solution temperature, ↑ diffusion rate

14. Types of Passive Transport
3) Osmosis= diffusion of water through a selectively
permeable membrane from an area of high water
concentration to an area of lowwater concentration
Solute= a substancedissolvedinanothersubstance(ex.Kool-Aid)
Solvent= a substancethatdoesthedissolving(ex.Water)
Solution= mixtureof solutes& solvents

15. Diffusion of H2O Across A Membrane
15
High H2O potential
Low solute concentration
Low H2O potential
High solute concentration

16. Isotonic
Hypotonic
Hypertonic
Types of
Solutions

17. Isotonic Solutions
Concentration of solute is equal on both sides of the membrane
No water net water movement

18. Hypertonic Solution
Solute concentration is greater outside the cell
Therefore more water inside the cell
Water moves out of the cell
PLASMOLYSIS (shrivels)

19. Hypotonic Solution
Solute concentration is less outside the cell.
Therefore more water outside the cell
Water moves into the cell
CYTOLYSIS (blows up)

20. 20
Isotonic Solution
NO NET MOVEMENT OF
H2O (equal amounts
entering & leaving)
Hypotonic
Solution
CYTOLYSIS
Hypertonic
Solution
PLASMOLYSIS

21. Active Transport
Cell uses energy
Against concentration
gradient
From low to high
Carrier Proteins
Molecule binds with carrier
protein
Energy then used to change shape
Molecule released on other side
Carrier protein returns to original
shape

22. Types of Active Transport
Sodium/Potassium (NA+/K+) Pump
Moves 3 Na+ out of a cell and 2 K+ into the
cell against (up) the concentration gradient
Requires ATP
Exocytosis
•Molecules are moved out of the cell by
vesicles that fuse with the plasma
membrane.
•This is how many hormones are secreted
and how nerve cells communicate with one
another.
Endocytosis – Movement of large molecules into
the cell
Two forms
1. Pinocytosis
2. Phagocytosis

23. Active Transport Processes
(Require ATP or other energy
sources)
Active transport: Use
career protein
Na+K-pumps3 Na+out and2K+insidethe cell

24. •Pinocytosis –
Cellformsan invagination
Materialsdissolve in water to be brought into cell
Called“CellDrinking”
•Phagocytosis
Usedto engulflarge particlessuchas food,bacteria,etc.intovesicles
Called“CellEating”

25. Active Transport Processes
(Require ATP or other energy
sources)
Formvesicle

26. Facilitated diffusion:
a- needs energy
b- needs a carrier
c- transport substances from low to high conc. gradient
d- is responsible for movement of water into the cell
e- is responsible for transport of gases
Osmosis:
a.occurs against a concentration gradient
b.needs a carrier
c. needs energy
d.does not need a carrier
e.it is an active process

27. Carry Home
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