Cell Organelles Overview

Cell Organelles

• Nucleus: Contains the cell's DNA, coordinates activities like protein synthesis and reproduction. In prokaryotes, the nucleoid contains the genetic material.
• Nucleolus: Site of rRNA synthesis, for ribosome production.
• Cytoplasm: Fluid-filled area where metabolic activity occurs, including the organelles.
• Mitochondria: Double-layered, produces ATP (energy), a site for fatty acid breakdown. Contains its own circular DNA and ribosomes.
• Ribosomes: Made of rRNA, responsible for protein synthesis.
• Rough Endoplasmic Reticulum (RER): Has ribosomes attached, synthesizes and stores proteins.
• Smooth Endoplasmic Reticulum (SER): Synthesizes lipids and steroid hormones.
• Golgi Apparatus: Modifies and packages proteins, including glycosylating polypeptides.
• Lysosomes: Made by Golgi, breaks down nutrients, bacteria, and cell debris, used in apoptosis.
• Peroxisomes: Common in liver and kidneys, break down substances.
• Vacuoles: Vesicles that move cell materials, membrane bound.
• Cytoskeleton: Maintains cell shape and movement. Includes microtubules (support and mobility), filaments (cell shape), centrioles (spindle fiber development).
• Vesicles: Membrane-bound structures that transport materials.
• Chloroplasts: (Plant cells) Contain chlorophyll, crucial for photosynthesis.
• Cell Walls: (Plant cells), provide support, made of various materials (peptidoglycan in bacteria, various polysaccharides in archaea).
• Cell Membrane: Controls what enters and exits the cell; selectively permeable, composed of phospholipids, proteins and cholesterol.

Cell Membrane Properties

• Phospholipid Bilayer: Allows small, uncharged, hydrophobic molecules to freely pass; others (large, polar, charged) require transporters.
• Permeability: Regulates cell membrane fluidity.
• Cholesterol: Regulates membrane fluidity.
• Membrane Proteins: Channel proteins (voltage-, ligand-, mechanically-gated); Porins (ions, polar molecules); Carrier and transport proteins (active transport like sodium-potassium pump).

Substance Movement

• Passive Transport: No ATP needed (down concentration gradient). Includes simple diffusion, osmosis, dialysis, plasmolysis, facilitated diffusion, and countercurrent exchange
• Active Transport: Uses ATP (against concentration gradient).
• Endocytosis: Phagocytosis (solid material), Pinocytosis (liquid), Receptor-mediated endocytosis (ligands binding to receptors).

Water Balance of Cells

• Hypertonic: Higher solute concentration than the surrounding environment.
• Hypotonic: Lower solute concentration than the surrounding environment.
• Isotonic: Equal solute concentration.
• Hypertonic Solution: Cell shrinks
• Hypotonic Solution: Cell swells
• Isotonic Solution: Cell remains the same size

Cell Junctions

• Anchoring Junctions: Connects cells.
• Tight Junctions: Forms a seal; prevents passage between cells. (e.g., digestive tract cells).
• Gap Junctions: Creates tunnels between animal cells for ion and small molecule passage.

Prokaryotes

• No nucleus.
• Single, circular, naked, double-stranded DNA.
• Ribosomes (70S).
• Cell walls (peptidoglycan or polysaccharides).
• Capsule/s may be present
• Flagella consist of flagellin (not microtubules)

This quiz covers essential details about various cell organelles, including their functions and significance in cellular processes. Test your knowledge on components such as the nucleus, mitochondria, and Golgi apparatus. Ideal for biology students aiming to understand cell structure and function.