Cell Compartmentalization

RNA and Cell Development

• RNA likely emerged as a key molecule for passing down information from generation to generation.

• This process was essential for the development of cells.

Prokaryotic Cells

• Prokaryotic cells are simple, single-celled organisms without a nucleus.

• Main structures include:

  • Flagella: Used for propulsion.

  • Capsule: Protective outer layer that retains moisture and aids in osmosis.

  • Cell Wall: Provides structure and protection.

  • Cell Membrane: Controls entry and exit of substances.

• DNA is located in a region called the nucleoid, often in a loop called a plasmid.

• Contains small ribosomes known as 70S ribosomes.

Eukaryotic Cells

• Eukaryotic cells have a defined nucleus and membrane-bound organelles.

• Key organelles include:

  • Nucleus: Site of genetic material and ribosome production (contains a nucleolus).

  • Rough Endoplasmic Reticulum (ER): Site of protein synthesis due to attached ribosomes.

  • Smooth Endoplasmic Reticulum (ER): Involved in fat metabolism and synthesis.

  • Golgi Apparatus: Modifies, sorts, and packages proteins and lipids from the ER.

  • Lysosomes: Contain enzymes for breaking down waste and cellular debris (act as the cell's janitor).

• Mitochondria: Double-membraned organelles that produce ATP, the energy currency of the cell.

  • Originated from engulfed bacteria, demonstrating a symbiotic relationship with eukaryotic cells.

  • Site of cellular respiration and glucose breakdown.

• Chloroplasts: Present in plants and algae, involved in photosynthesis but not found in animal cells.

Cell Compartmentalization

• Refers to divisions within a cell that isolate various processes.

• Enhances efficiency by providing different environments (e.g., varying pH) for chemical reactions.

• Similar to operational departments in a store, each organelle specializes in specific tasks.

Centrifugation

• A technique used to separate cellular components based on density by spinning samples at high speeds.

• Allows for the extraction of different organelles and analysis of their functions.

Nucleus and Genetic Material

• Site of DNA transcription.

• Nuclear envelope: double-layered with pores for RNA and ribosome movement.

• Nucleoplasm: Gel-like substance within the nucleus facilitating molecular collisions.

• Nucleolus: Production site for ribosomal RNA (rRNA).

Lysosomes and Cellular Digestion

• Contain lytic enzymes for digestion and waste management within cells.

• Perform phagocytosis: engulfing particles such as bacteria to digest them.

• When cellular components need disposing of, lysosomes can initiate cell death.

Specialization of Cells

• Different types of cells (muscle, nerve, fat) have specialized functions requiring specific nutrients and energy sources.

• Even though all cells contain the same DNA, only certain genes are expressed depending on the cell's function.

Cellular Respiration

• Process of glucose breakdown to produce ATP, yielding energy for cellular activities.

• ATP is generated primarily in mitochondria and is essential for all living organisms.

  • In aerobic conditions, a single glucose can yield about 30-36 ATP.

• Anaerobic respiration occurs when oxygen is limited, as in intense exercise.

Ribosomes and Protein Synthesis

• Ribosomes consist of two subunits and synthesize proteins by translating mRNA sequences into amino acid chains.

• There are two types of ribosomes: 70S (in bacteria) and 80S (in eukaryotes).

  • Free-floating ribosomes synthesize proteins for use within the cell; attached ribosomes (on rough ER) make proteins for export.

Golgi Apparatus

• Composed of flattened, membrane-bound sacs (cisternae).

• Receives materials from the ER, processes them, and then secretes them via vesicles through the trans side (exocytosis).

Vesicles Functionality

• Transport vesicles: Move materials from the ER to other organelles.

• Secretory vesicles: Carry materials out of the cell through exocytosis.

• Peroxisomes: Contain enzymes for breaking down fatty acids.

• Lysosomes: Their functions peak during waste processing and cell death.