Zoo- Sep 2

Biomolecules

  • Four biomolecule classes: carbohydrates, lipids, proteins, nucleic acids.

  • Carbohydrates: energy source; simple sugars (glucose); common in bread, fruit, milk.

  • Proteins: diverse roles (enzymes, structure, transport); examples include insulin, keratin, myosin.

  • Lipids: energy storage, membrane structure, hormones; cholesterol example; important in cell membranes.

  • Nucleic acids: DNA and RNA; store/transmit genetic information.

Cells: Prokaryotic vs Eukaryotic

  • Prokaryotes lack a membrane-bound nucleus.

  • Eukaryotes have a membrane-bound nucleus that contains DNA and possess membrane-bound organelles.

Organelles and the Endomembrane System (overview)

  • Endomembrane system: group of membranes and organelles that work together to modify, package, and transport macromolecules (primarily proteins).

  • It is a continuous membrane system extending from the nuclear envelope.

  • Key components discussed: nucleus, endoplasmic reticulum (rough and smooth), Golgi apparatus, lysosomes, vesicles;
    ribosomes also play a central role in protein synthesis.

Nucleus and Nucleolus

  • Nucleus: double membrane with nuclear pores that regulate traffic; houses DNA.

  • Nucleolus: site of ribosomal RNA (rRNA) synthesis.

  • Nuclear pores allow transcriptional and ribosomal components to exit the nucleus.

Ribosomes

  • Ribosomes are the site of protein synthesis; composed of ribosomal RNA (rRNA) and proteins.

  • Some are free in the cytoplasm; others are attached to the rough endoplasmic reticulum (RER).

  • RNA types involved: RNA is a nucleotide; ribosomes are central to translating genetic information into proteins.

Rough Endoplasmic Reticulum (RER) vs Smooth Endoplasmic Reticulum (SER)

  • Rough ER: has ribosomes on its surface; site of protein synthesis destined for secretion or membranes.

  • Smooth ER: lacks ribosomes; synthesizes lipids and is involved in other metabolic processes.

Golgi Apparatus

  • Function: sorting, modifying, and packaging proteins for delivery to their final destinations.

  • Structure: cis, medial, trans cisternae; trans Golgi network.

  • Process: proteins from RER enter via cisternae, are modified by Golgi enzymes, and packaged into vesicles for delivery to lysosome, cell membrane, or secretion.

Lysosomes and Vesicles

  • Lysosomes: digestive organelles containing enzymes to break down biomolecules; recycling within the cell.

  • Vesicles: membrane-bound carriers that transport cargo between organelles and to/from the cell membrane.

  • Endomembrane system relies on vesicles to move materials between compartments.

Mitochondria

  • Powerhouse of the cell: produces most ATP via cellular respiration.

  • Distinct features: own DNA and own ribosomes; double membrane.

  • Origin: endosymbiotic theory (ancestral uptake of a primitive prokaryote).

  • Inheritance: mitochondrial DNA is maternally inherited in humans.

Quick Connections

  • Endomembrane system focuses on processing and trafficking of proteins and lipids via ER -> Golgi -> vesicles -> destinations (lysosome, membrane, secretion).

  • Mitochondria provide energy and have unique genetic material separate from the nuclear genome.

  • Biomolecules underpin structure and function of all organelles and processes described above.