Cell Biology: Golgi Apparatus & Endoplasmic Reticulum

Study Notes

The Golgi apparatus processes a variety of cellular substances along the secretory pathway.
Rough endoplasmic reticulum (rough ER) synthesizes, folds, and modifies proteins for delivery to organelles or secretion.
Rough ER responds to unfolded proteins and is linked to apoptosis via interaction with mitochondria.
It is distinguished by membrane-bound ribosomes visible under a microscope.
Smooth endoplasmic reticulum (smooth ER) is tubular, lacking ribosomes, and primarily manufactures lipids.
In liver cells, smooth ER assists in breaking down glycogen into glucose.
Smooth ER also produces steroid hormones in adrenal cortex and endocrine glands.

The nucleus is a double-membraned organelle containing genetic material, regulating cellular activities such as metabolism and division.
It is crucial for categorizing cells as prokaryotic (no nucleus) or eukaryotic (true nucleus).
The nucleolus, found within the nucleus, produces and assembles ribosomes and does not contain chromosomes.
It accounts for approximately 25% of the nucleus's volume and consists of fibrillar centers where ribosomal proteins are formed.

Ribosomes are molecular machines for protein synthesis, composed of rRNA and proteins (ribonucleoprotein).
They consist of two subunits: smaller and larger, and can be free in the cytoplasm or attached to rough ER.
Essential for all living cells to produce proteins, ribosomes differ in size between prokaryotic (70S) and eukaryotic (80S) cells.

Mitochondria are membrane-bound organelles generating chemical energy for cellular reactions.
They contain their own small chromosomes, highlighting their role in energy metabolism.

Bacterial conjugation is a direct genetic transfer mechanism between bacterial cells requiring contact.
Eukaryotic cell division through meiosis reduces chromosome number in gametes, while prokaryotic cells divide via binary fission.

Prokaryotic cells range from 0.1 to 5.0 micrometers, lacking a true nucleus and membrane-bound organelles.
Eukaryotic cells range from 10 to 100 micrometers, which contain a true nucleus and various organelles.
Eukaryotic cell walls are complex (cellulose), while prokaryotic walls are simpler (peptidoglycan).
Eukaryotic cells possess a cytoskeleton, whereas prokaryotic cells do not.

Stem cells can differentiate into specialized cell types like muscle or nerve cells depending on microenvironment signals.
Animal cells increase in size by accumulating cytoplasm and organelles, while plant cells expand through water uptake in vacuoles.
Turgor pressure from vacuoles causes plant cells to swell and enlarge.

In plant cells, a cell plate forms from Golgi-derived vesicles during cytokinesis, ultimately dividing the cell.
Glyoxysomes, found in plant cells, are involved in lipid metabolism and convert stored lipids into carbohydrates, especially in seeds.
Animal cells primarily rely on mitochondria for energy production, differing in metabolic processes from plants.