Cell Biology: Nucleus and Endoplasmic Reticulum

Study Notes

Nucleus: Largest structure in the cell, responsible for ribosome assembly.
Endoplasmic Reticulum (ER):
- Composed of lipids and tubule proteins; continuous with the nuclear envelope.
- Lumen: Interior space of the ER.
- Rough ER: Studded with ribosomes; synthesizes proteins that enter the lumen for transport via vesicles.
- Smooth ER: Lacks ribosomes; synthesizes carbohydrates and lipids, and stores calcium ions.
Vesicles and Vacuoles:
- Membrane-bound sacs for transport and storage.
- Vacuoles are generally larger than vesicles.
Golgi Apparatus:
- Responsible for packaging, sorting, and tagging molecules for various destinations.
Lysosomes:
- Function as cellular "garbage disposals"; break down proteins, lipids, and carbohydrates and recycle molecules.
- Operate at low pH.
Ribosomes:
- Sites of protein synthesis, either bound to the ER or free in the cytoplasm of prokaryotic cells.
Peroxisomes:
- Breakdown factories for lipids and amino acids; produce H2O2 as a byproduct, which is neutralized before leaving.

Mitochondria:
- Sites of ATP synthesis, carbohydrate, and lipid metabolism.
- Feature two bilayer membranes with folds called cristae; contain their own DNA.
Chloroplasts:
- Present in plant cells; function in photosynthesis.
- Comprise two membranes and contain thylakoids, stacked into granum within the stroma.

All living organisms consist of one or more cells, proposed historically by Robert Hooke, Anton von Leeuwenhoek, Schleiden, and Schwann.

Light Microscopes:
- Resolution of about 250 eukaryotic cells with a 2mm pin diameter.
Electron Microscopes:
- Utilize electron beams with a resolution of 2μm.

Single-celled organisms without membrane-bound organelles; include structures like:
- Cell Membrane: Phospholipid bilayer.
- Cell Wall & Capsule: Composed of peptidoglycan; penicillin affects this structure.
- Pili: Function in conjunction (conjugation).

Bacteria, Archaea, and Eukarya.
Key differences: Archaea lack peptidoglycan in cell walls and have different membrane phospholipids compared to bacteria.

Contain membrane-bound organelles and a nucleus; significantly larger than prokaryotic cells.

Plasma Membrane: Composed of phospholipids and proteins, separates the outside environment from the cytoplasm.
Cytosol: Liquid component of the cytoplasm, around 70% water.

A network of protein fibers maintaining cell shape, consisting of microfilaments, intermediate filaments, and microtubules.

A system of membrane-bound compartments managing lipid and protein transport, including the nuclear envelope, lysosomes, vesicles, ER, and Golgi apparatus.