Behrouz Mahmoudi Cell organelles2 1 Golgi apparatus 2 Golgi apparatus sometime called the Golgi body It was identified in 1897 by the Italian physician Camillo Golgi and named after him in 1898 ID: 531625
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Slide1
Cell and Molecular Biology
Behrouz Mahmoudi
Cell organelles-2
1Slide2
Golgi apparatus
2Slide3
Golgi apparatus (sometime called the Golgi body).
It was identified in 1897 by the Italian physician Camillo Golgi and named after him in 1898
Golgi apparatus consists of sacs (with a single membrane) which are stacked like pancakes. The sacs or folds of the Golgi apparatus are called cisternae
The cisternae stack has five functional regions:
the
cis
-Golgi network
,
cis-Golgi, medial-Golgi, trans-Golgi, and trans-Golgi network
3Slide4
Cells synthesize a large number of different macromolecules. The Golgi apparatus is integral in modifying, sorting, and packaging these macromolecules for cell secretion
(exocytosis) or use within the cell
4Slide5
The Golgi processes proteins made by the endoplasmic reticulum (ER) before sending them out to the cell. Proteins enter the Golgi on the side facing the ER (
cis side), and exit on the opposite side of the stack, facing the plasma membrane of the cell (trans side).
Each cisterna
contains
different protein modification enzymes.
It is also involved in the transport of lipids around the cell, and the creation of
lysosomes.
Lysosomes are membrane-enclosed organelles that contain an array of enzymes capable of breaking down all types of biological polymers—proteins, nucleic acids, carbohydrates, and lipids.
Lysosomes are
the cell's waste disposal system
5Slide6
What do these Enzymes within the cisternae do?
1- catalyze the addition or removal of sugars from cargo proteins (glycosylation): glycosaminoglycans(GAGs).
2- addition of sulfate groups (
tyrosin sulfation) like heavy chain of
immunoglobulinM
3-
addition of phosphate groups (phosphorylation). One molecule that is phosphorylated in the Golgi is
Apolipoprotein
, which forms a molecule known as VLDL that is a constituent of blood serum.
6Slide7
The Golgi plays an important role in the synthesis of proteoglycans, which are molecules present in the extracellular matrix of animals
. It is also a major site of carbohydrate synthesis.This includes the production of
long unbranched polysaccharides .
Enzymes in the Golgi
polymerize several
of these GAGs via a
xylose link
onto the core
protein.
glycosylation mainly refers in particular to the enzymatic process that attaches glycans to proteins, lipids, or other organic molecules
The majority of proteins synthesized in the rough ER undergo glycosylation.
7Slide8
1- N-linked
glycans attached to a nitrogen of asparagine or arginine side-chains.
2- N-linked glycosylation requires participation of a special lipid called dolichol phosphate
.3- O-linked glycans attached to the
hydroxy
oxygen of serine, threonine, tyrosine,
hydroxylysine
, or
hydroxyproline
side-chains, or to oxygens on lipids such as ceramide.4- C-linked glycans, a rare form of glycosylation where a sugar is added to a carbon on a tryptophan side-chain.5- Glypiation, which is the addition of a GPI anchor that links proteins to lipids through glycan linkages.
8Slide9
The Cell Nucleus
The nucleus is a highly specialized organelle that serves as the
information processing
and administrative center of the cell.
has two major
functions;
1-
stores
the cell's
hereditary material or DNA2- coordinates the cell's activities, which include growth, intermediary metabolism
,
protein synthesis,
and
reproduction
(cell division)
The semifluid matrix found inside the nucleus is called
nucleoplasm
9Slide10
Chromatin and chromosome
In the nucleus, the DNA double helix is packaged by special proteins (
histones
) to form a complex called chromatin. The chromatin undergoes
further condensation
to form the
chromosom
e. Chromosomes are condensed Chromatin Fibers
10Slide11
The nucleolus
The nucleolus is a
membrane-less organelle
within the nucleus that manufactures ribosomes, the cell's protein-producing structures.
After a cell divides, a nucleolus is formed when chromosomes are brought together into
nucleolar
organizing regions.
During cell division,
the
nucleolus disappears11Slide12
Ribosomal RNA Genes
12Slide13
The nuclear envelope
The nuclear envelope is a double-layered membrane that encloses the contents of the nucleus. The space between the layers is called the
perinuclear space and appears to connect
with the rough endoplasmic reticulum
The
inner surface
has a protein lining called the
nuclear lamina
, which
binds to chromatin and other nuclear components.
13Slide14
nuclear pores
These pores regulate the passage of molecules between the nucleus and cytoplasm,
All transport between the nucleus and the cytoplasm passes through the nuclear pore complex (NPC)
The
nuclear pore
complex is made of
thirty different proteins
known as
nucleoporins
; there are about 500-1000 proteins in the NPC because the NPC has internal symmetry and each
nucleoporin
repeats many times
.
14