About cell membrane function and Cell cycle

2. Outline
•Fluid Mosaic Model
•Function of Cell membrane
•Membrane Proteins
•Cell junction
•Cell signaling
•Cell Cycle

4. •Protection
•Communication
•Selectively allow substances in
•Respond to environment
•Recognition

5. •Transport
•Receptors
•Enzymes
•Signal Transducers
•Support

7. Plasma Membrane Proteins

8. Permeability of the Cell Membrane

9. Diffusion
The passive movement of molecules from a
higher to a lower concentration until equilibrium
is reached.
It also called Passive transport

10. Active Transport

11. •Exocytosis---Cellular secretion
•Endocytosis—
Phagocytosis— “Cell eating”
Pinocytosis– “Cell drinking”
Receptor-mediated endocytosis-specific
particles, recognition.

12. EXOCYTOSIS

13. PHAGOCYTOSIS
Phagocytosis 1
Phagocytosis 2

14. PINOCYTOSIS

15. RECEPTOR-MEDIATED
ENDOCYTOSIS

16. Definition and Classification of cell
junction
Cell junction is the connection between the neighbouring
cells or the contact between the cell and extracellular
matrix.
It is also called membrane junction.
Cell junction are classified into three types
a-Occluding junction or Tight junction
b-Communicating junction or Gap junction
c-Anchoring junction.

17. Tight Junction
Tight Junction- occluding junctions / zonulae
occludens - zonula occludens), are the closely associated
areas of two cells whose membranes join together forming
a virtually impermeable barrier to fluid.
 A type of junctional complex present only in
vertebrates.
Gap Junction
Gap junctions are clusters of intercellular channels
that allow direct diffusion of ions and small molecules
between adjacent cells.
At gap junctions, the intercellular space narrows from
25 nm to 3 nm.

18. CELL SIGNALING
 General Principles of Cell Signaling
 signaling cell => signaling molecule binds to receptor molecule on target cell
Signaling Distances: => Four Types of Signaling F.16-3
 Endocrine
 Paracrine
 Autocrine
 Contact Dependent

20. Cell Division
The process of reproduction or formation of
new cell from pre-existing cell is referred to as cell
division
Cell cycle
The period in one cycle of cell division is
completed is called cell cycle

22. INTERPHASE
 Interphase can be subdivided into G1, S and G2
phases.
 In yeast “Start” is at the end of G1; at this point the cell
is committed to DNA synthesis.
 In mammals, this is called the “restriction point”. This
point late in G1 is a “checkpoint”; a cell will exit the cell
cycle if certain requirements to proceed to synthesis are
not met.
 A second restriction point occurs in G2 before entry into
mitosis.
Interphase M Interphase M Interphase
G1 S G2 M G1 S G2 M G1 S G2

23. INTERPHASE: G1
 Events during G1
 Cell growth
 Preparation of chromosomes for replication
 Duplication of cellular components
 G1 checkpoint (or restriction point); cell commits to
division or exits from cell cycle

24. INTERPHASE: S PHASE
 DNA replication
 Duplication of the centrosome
 The centrosome is located near the nucleus of the cell
and contains the microtubule organizing center MTOC
in animal cells. It contains two centrioles that migrate to
the poles before cell division and serve to organize the
spindle.

25. INTERPHASE: G2
 Cell growth
 Checkpoint (restriction point) for entry into M phase

26. M PHASE
 Cell division (mitosis or meiosis for germ cells)
 Can be subdivided into four subphases:
 Prophase
 Metaphase
 Anaphase
 Telophase
 Factors that influence M phase entry
 Cellular Mass
 Growth Rate
 Time (During early embryogenesis, divisions may
proceed rapidly, essentially alternating M and S phases,
with little growth between them.)
 Completion of DNA Replication