Mitochondria ,ER and golgi App Flashcards
What is the number of mitochondria?How they increase in number?
- More in active cell as liver cell (1000/cell).
* Increase in number by simple division as they have DNA.
Define mitochondria with reference to its site in the cell giving 2 examples of cells rich in these structures.
- Membranous organelles,
- containing enzymes responsible for
- aerobic respiration and energy production.
- They are the power-house of the cell.
- Accumulate in cytoplasm at sites of most activity, where energy is needed.
- Muscle, liver cell.
Describe LM and EM of mitochondria:
LM:
eosinophilic structures.
rods or granules dark blue with iron H and green with Janus green stain.
EM:
oval or rounded membranous vesicles.
0.5-1 µm in diameter and 10 µm in length.
surrounded with two unit membranes separated by an inter-membranous space:
The outer membrane:
smooth
contains transmembrane proteins called porins
permeable to small molecules.
The inner membrane:
less permeable (selective).
It projects into the matrix forming shelf-like folds called cristae.
Their number corresponds to energy needs.
They increase the surface area for attachment of Elementary particles
which are globular structures connected to the inner membrane by cylindrical stalks.
They represent a protein complex with ATP synthetase activity (forms ATP in oxidative phosphorylation).
Mitochondrial Matrix: composed of:
Oxidative enzymes of citric acid cycle.
A circular molecule of DNA.
mRNA, tRNA and rRNA.
Electron-dense granules rich in Ca2+ that act as catalysts for mitochondrial enzymes.
Mention the Functions of mitochondria.
Cell respiration:
Obtaining energy from the metabolites present in cytoplasm by Kreb’s cycle.
Most of this energy is stored as ATP molecules by oxidative phosphorylation and some is liberated as heat to maintain body temperature.
Name one disease that results from mutation of mitochondrial DNA. Mention the source of inheritance of this disease.
Muscular dysfunction
Maternal source.
mention the site of the following in mitochondria: Kreb’s cycle enzymes. DNA RNA Elementary particles. Electron dense granules.
Matrix Matrix Matrix Cristae Matrix
Define and classify endoplasmic reticulum.
network of intercommunicating channels and sacs formed by continuous membrane enclosing a space called cisterna.
According to presence/absence of ribosomes on the cytosolic side. 2 types;Rough with ribosomes and smooth without ribosomes
In a table form compare and contrast the two types of endoplasmic reticulum.
site
LM
EM
Functions
What are porin and ribophorins
Porins are proteins in the outer membrane of mitochondria the make this membrane permeable.
Ribophorins are specific receptors on the membranes of rER where the ribosomes are attached by their large subunits. Under the receptor is a pore that allows newly synthesized proteins to enter and to be stored in the rER cisternae.
List the functions of Golgi apparatus.
1- Packing, concentration & storage of proteins received from rER .
2- Chemical modification of proteins by addition of carbohydrates and sulfates.
3- Formation of secretory vesicles, coated vesicles and lysosomes.
4- Discharge of secretory products as hormones and enzymes in secretory vesicles.
5- Renewal and maintenance of cell membrane by providing it with integral proteins from membrane of secretory vesicles.
Describe EM picture of Golgi apparatus.
3-10 parallel flat curved membranous saccules arranged one above the other forming stacks.
Each saccule has a narrow lumen with expanded ends.
It is filled with low electron-dense material.
Saccules are inter-connected with each other.
Each stack has 2 faces:
Entry (Cis) Face: It receives transfer vesicles from rER carrying proteins, into the saccules to reach the trans face.
Exit (Trans) Face: The vesicles that bud off from this face are either: (1) Secretory vesicles that discharge their contents to the outside (exocytosis), or (2) Lysosomes, which are membranous organelles retained in the cytoplasm.
Describe LM picture of Golgi apparatus.
LM:
Does not appear in H & E stained sections. In protein synthesizing cells (plasma cells) characterized by deeply basophilic cytoplasm, it can be seen as a pale unstained area near the nucleus called “negative Golgi image”.
With silver stain (Ag), it can be demonstrated as a network of brown granules & fibrils, either
Apical: Between the nucleus and the pole of the cell, in secretory cells.
Perinuclear: Completely surrounds the nucleus, in nerve cells.
Define and explain –ve Golgi image.
It is a pale area in the basophilic cytoplasm near the nucleus.
Golgi apparatus has no ribosomes so it will appear pale in cells with abundant rER or ribosomes as plasma cell since the cytoplasm will be blue except the area of Golgi.
List the steps by which enzyme lipase is produced by the pancreatic cell.
1-Protein formation occurs in attached ribosome
2- Protein enters the tubules of rER where it is packed in membranous vesicles that bud off from the cisternae as transfer vesicles.
3- In Golgi apparatus, concentration and accumulation of the products received from rER.
4-Formation of secretory vesicles that comes out of cis face.
5-Discharge of secretory vesicle by exocytosis.
Plasma cell produces antibodies. suggest and explain how would be the appearance of the cytoplasm under light and electron microscope
LM: basophilic cytoplasm , rich in rER ,
/negative Golgi image, well developed Golgi
EM: rich in rER, GA (formation of antibodies), secretory granules and mitochondria (energy production, active cell).
