Cell Biology: Organelles, Protein Synthesis and Genetics
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Cellular Secretions
Secretions include: tears, gastric juice, hormones, and saliva.
Endoplasmic Reticulum (ER)
- Shape: A network of flattened sacs.
- Composition: Plasma membrane (lipoprotein).
- Types:
- Rough ER (RER/Ergatoplasm): Responsible for protein storage.
- Smooth ER (SER): Responsible for lipid production and transport.
Golgi Complex
Visible as flattened sacs with cis and trans faces (dictyosomes). Functions include receiving, transporting, dispatching, and packaging substances like mucus (for nasal cavities, trachea, and stomach) and glycoproteins.
- Biological roles: Polysaccharide production for the middle lamella, lysosome formation, and acrosome development in sperm cells.
Glandular Systems
- Unicellular glands: Secretory cells.
- Multicellular glands:
- Exocrine: Secretes outside (e.g., lacrimal, salivary).
- Endocrine: Secretes hormones (e.g., Thyroid T3/T4 for metabolism; Adrenal glands for adrenaline).
- Amphicrine (Mixed): Includes the pancreas (endocrine/exocrine) and gonads (testicles/ovaries).
Cellular Components and Genetics
Ribosomes
Composed of protein and ribosomal RNA. They are the site of protein synthesis and are found free in the cytoplasm, attached to the RER, or on the external face of the karyotheca.
The Nucleus
The control center of cellular activity. Components include:
- Karyotheca: A double lipoprotein membrane with pores for communication with the RER.
- Nucleoplasm: A liquid medium for chemical reactions.
- Nucleolus: Rich in RNA and proteins; responsible for ribosome production.
- Chromatin: DNA that condenses into chromosomes during cell division.
DNA and RNA Biochemistry
- DNA: Deoxyribose sugar, double-stranded, self-replicating. Bases: Adenine, Guanine, Cytosine, Thymine.
- RNA: Ribose sugar, single-stranded, no self-replication. Bases: Adenine, Guanine, Cytosine, Uracil.
- Base Pairing: G ≡ C and T = A.
Molecular Processes
- DNA to DNA: Autoduplication.
- DNA to RNA: Transcription.
- RNA to Protein: Translation.