Essential Concepts in Cell Biology and Biochemistry

Cytoskeleton

The cytoskeleton is located between the karyota and the membrane. It provides intercellular support, aids in movement, participates in cell division, and is rich in protein. There are three types of eukaryotic cytoskeleton filaments:

• Actin microfilaments: Composed of actin proteins, approximately 3.7 nm in diameter.
• Intermediate filaments: Fibrous proteins, 10 nm in diameter, located in the cytoplasm.
• Microtubules: 25 nm in diameter, originating from the microtubule-organizing center, composed of alpha and beta tubulin proteins.

Cellular Functions and Processes

Cerumen

Cleans, lubricates, and protects against fungi, insects, and bacteria.

Protein Denaturation

The alteration of the secondary, tertiary, and quaternary structure of a protein under the influence of a denaturing agent; the primary structure remains unaltered. This can be caused by extreme temperatures, strong acids, or alkalis. It can be reversible or irreversible. Proteins with disulfide bridges are more resistant to denaturation.

Autophagy

A cleaning mechanism that collects old proteins and other cytoplasmic debris. It also serves as a defense mechanism against viruses and bacteria.

Abiogenesis

A term for theories regarding the origin of life.

Endosymbiotic Theory

Describes the transition from a prokaryotic cell to a eukaryotic cell, involving the adaptation of bacteria to live in different environments.

Virus and Bacterial Reproduction

Involves a 10 nm tube through which bacterial DNA is transferred directly from one cell to another, involving bacterial plasmids.

Lipid Rafts

Composed of proteins, cholesterol, glycocalyx, glycoproteins, and glycolipids.

Biochemistry and Molecular Bonds

Glycosidic Bond

The binding of monosaccharides to form di- and polysaccharides.

Peptide Bond

A covalent bond between an amino group (NH2) and a carboxyl group (COOH), involving the molecular formation of H2O and one covalent link.

Nucleic Acids

• DNA: Contains nitrogenous bases divided into purines (G, A) and pyrimidines (C, T).
• mRNA: Contains caps, exons, and poly-A tails.
• rRNA: Found in mitochondria and the nucleolus.
• tRNA: Contains an anticodon.

Carbohydrates

Large molecules formed by carbon chains and rings, binding to other atoms via four strong covalent links.

Ribosomes

Formed by proteins and ribosomal RNA. They exist as 70S (prokaryotic) and 80S (eukaryotic) units, functioning in protein synthesis.

Lactic Fermentation

A metabolic process that utilizes glucose for energy.