NUCLEAR ENVELOPE
(NUCLEAR MEMBRANE)

• The nuclear envelope, like the cell membrane, is too thin to be
appreciated under the optical microscope, but it is visible in EM.
• It consists of two unit membranes;
• *Outer nuclear membranes
• *Inner nuclear membranes
• 7 to 8nm thick each, that are separated from each other by a 10 to
30nm fluid-filled space (perinuclear space; perinuclear cisterna;
intermembranous space).

The nuclear envelope is perforated by circular
openings (nuclear pores) that are 70 to 75nm in
diameter.
• Each nuclear pore is ringed by a nuclear pore
complex that is made up of electron-dense
protein molecules. Some of the proteins in the
nuclear pore complex form a thin film, called pore
diaphragm, which covers the nuclear pore.

Chromatin (Chromatin material; chromatin
threads)
• Chromatin – refers to the chromosomes at
interphase.
• The nucleus of all nucleated human cells contain
46 chromosomes (22 pairs of somatic and pair of
sex chromosomes).
Cells with 46 chromosomes are referred to as
diploid while those with only 23 are referred to as
haploid.

• Each chromosome consists of one very long
DEOXYRIBONUCLEIC ACID (DNA) MOLECULE and a
variety of associated proteins (nucleoproteins). The
nucleoproteins are of two major types, histones and
nonhistones.

HUMAN GENOME
-Refers to the total amount of DNA that is present
in a human cell.
- It consists of of a large chromosomal genome, which
refers to the DNA in chromosomes and much smaller
mitochondrial genome which refer, to the DNA in the
mitochondria. ( The only cellular structures aside from
the nucleus that contain DNA).

NUCLEAR MATRIX ( Nuclear sap;
Nucleoplasm)
• Nuclear matrix is composed of water, proteins,
metabolites, and ions. The proteins that are
present in the nuclear matrix are mostly
associated with DNA molecules.

NUCLEOLUS
• The nucleolus is a spherical, highly basophilic
structure that is usually eccentrically located in
the nucleus. It is not enveloped by unit membrane
and is present only in the cells that are at
interphase.

• IN ELECTRON MICROGRAPHS, THE NUCLEOLUS IS SEEN
TO CONSIST OF THREE AREAS:
*NUCLEOLAR ORGANZING REGION
*PARS FIBROSA
*PARS GRANULOSA

PROTEIN SYNTHESIS WITHIN THE CELL
One of the most important activities of a cell is the
production or synthesis of proteins. Proteins
comprise many essentials parts of cells and tissues.
They likewise make up the enzymes that catalyze
biochemical reactions, and hormones and hormone-
like substances that regulate the activity of cells.

MOVEMENT OF MATERIALS ACROSS THE CELL
MEMBRANE
• The cell membrane is a semi-permeable barrier, which
means that it allows certain materials to enter and leave
the cell while it constrains others.
• Simple molecules cross the cell membrane by a variety of
means : diffusion ; passage through ion channels :
carrier transport: and active transport with the aid of
pumps. These methods of transport are described in
physiology textbooks. Bigger substances such as
bacteria and secretory products, on the products, are
carried across the cell membrane via two mechanisms ;

• Endocytosis – refers to transport of substances from the
extracellular space into the cell. If the substance being
transported is solid such as a bacterium or dust particle,
the process is called phagocytosis, but if it is liquid, the
process is called pinocytosis.
• It simply involves invagination of the cell membrane to
enclose the fluid that needs to be ingested and then
pinching off of the membrane-bound pinocytic vesicle
from the inner surface of the cell membrane.
• Pinocytosis that involves intake of large amounts of
liquids is called macropinocytosis while pinocytic intake
of minute amounts of liquid is referred to as
micropinocytosis.

• EXOCYTOSIS
• - Exocytosis refers to the process of transporting
substances that are inside the cell, mostly secretory
products (secretions) which are in form of secretory
vesicles from the Golgi complex, across the cell membrane
and out of the cell. It involves fusion of the vesicular
membrane with the cell membrane followed by the release
of vesicular contents to the exterior of the cell.
• Exocytotic release of secretory products by cells occurs in
either one of two ways; regulated secretion or constitutive
secretion.