This document discusses the structure and function of cell membranes. It outlines the cell theory that cells are the basic unit of structure in organisms and that new cells are formed from existing cells. It describes the key parts of cells, including the cell membrane that defines boundaries, the nucleus that acts as the control center, and protoplasm that contains functional structures. The document discusses theories of cell membrane arrangement and molecular composition. It explains that cell membranes maintain structural integrity, control movement of substances in and out of cells, and act as an interface between the cytoplasm and external environment. The membrane uses various transport proteins like channels and carriers to regulate passage of substances.

1. CELL STRUCTURE
Prof. Redem C. Deligero, MATMRS;MSES

2. THE CELL THEORY
1. All organism consist of one or more cells
2. Cell is the basic unit of structure for all
organism.
3. All cells arise only from preexisting cell

3. BASIC PARTS OF A CELL
1. Cell Membrane – This is the structure that separates
the cell from it external environment which defines its
boundary and serves as a limiting membrane that
regulates the entrance and exit of substances from cell
and its environment.
2. Nucleus – This is the rounded structure usually at the
center of the cell enclosed by another membrane
called nuclear envelope. This structure is considered
as the control center of the cell for most of it metabolic
activities.
3. Protoplasm – This is known as the living substance
within the cell because it contains the functional
structure making the cell an independent structure.

4. THEORY OF CELL MEMBRANE
ARRANGEMENT
1. Fluid-Mosaic Model – This model of cell
membrane arrangement were proposed by S.
Jonathan Singer and Garth Nicholson (1972)
which states that the cell membrane is like an
ocean or sea in which there are many
substances that floats like an icebergs.
2. Tripartite Arrangement – This is proposed by
Danielle and Dawson (1935) which states that
the cell membrane is like a railroad truck with
two outer dark bands and a lighter middle core
or layer.

5. MOLECULAR ARRANGEMENT OF A CELL MEMBRANE

6. CELL MEMBRANE FUNCTION
1. Maintain structural integrity of the cell.
2. Control movement of substances in and out of the cell.
3. Regulating cell-cell reactions.
4. Recognition, via receptors, antigens and foreign cells
as well as altered cells.
5. Acting as an interface between the cytoplasm and the
external milieu.
6. Establishing transport systems for specific molecules.
7. Transducing extracellular physical or chemical signals
into intracellular events.

7. CELL MEMBRANE COMPONENT
1. Phospholipids – Third class of lipids
similar to triacylglycerols.
2. Cholesterol – A subclass of lipids in
animals.
3. Proteins – Linear polymer of amino acids.
4. Charbohydrates – Sugar group.

8. GLYCOCALYX
1. Protection of cell from interaction with
inappropriate proteins.
2. Protection from chemical physical injury.
3. Cell-cell recognition and adhesion.
4. In blood clotting and inflammatory
reaction.

9. MEMBRANE TRANSPORT PROTIENS
1. Channel Proteins – Gated or ungated
and incapable of transporting substances
against concentration gradient.
2. Carrier Proteins – utilize ATP-driven
transport mechanism to ferry specific
substances across the plasmalemma
against the concentration gradient.

10. VOLTAGE GATED CHANNEL

11. LIGAND-GATED CHANNEL

12. MECHANICALLY GATED CHANNEL

13. G PROTEIN-GATED CHANNEL

14. POTASSIUM LEAK CHANNEL

15. PRIMARY ACTIVE TRANSPORT

16. SECONDARY ACTIVE TRANSPORT