IB Biology B2.2 Organelles and Compartmentalization

Flashcards covering key terms and concepts related to IB DP Biology B2.2 (Organelles, Compartmentalization, Cell Fractionation, Ultracentrifugation, Mitochondria, Chloroplasts, and Vesicle Transport).

Organelle

A compartmentalized subcellular structure found within a cell that is adapted to perform a specific function.

Non-compartmentalized Cell Structures

Cellular structures not classified as organelles, including the cell wall (extracellular), cytoplasm (gel-like fluid lacking compartmentalization), and cytoskeleton.

Cell Fractionation

A laboratory process that separates cell organelles while preserving their individual functions.

Homogenization

The initial step of cell fractionation where tissues are broken up in a blender using a cold, buffered, isotonic solution, then filtered to remove large debris.

Ultracentrifugation

A technique using a fast centrifuge to separate organelles by density through sequential high-speed spins, producing pellets of specific cell components.

Plasma Membrane

A phospholipid bilayer surrounding and enclosing the cell that controls what enters and exits; considered an organelle by the IB curriculum.

Lysosome

A membrane-bound organelle containing digestive enzymes that break down macromolecules, old cellular structures, or engulfed pathogens.

Phagocytosis

The endocytic process by which a cell engulfs solid particles or pathogens to form a phagocytic vacuole.

Phagosome (Phagolysosome)

A cellular compartment formed by the fusion of a lysosome with a phagocytic vacuole, allowing enzymes to digest engulfed material.

Mitochondrion

A double-membraned organelle responsible for ATP production via aerobic cell respiration, identifiable by inner membrane folds called cristae.

Cristae

Folds of the inner mitochondrial membrane that increase surface area for the electron transport chain and ATP synthase.

Mitochondrial Matrix

The fluid-filled inner compartment of a mitochondrion containing DNA, $70S$ ribosomes, and enzymes required for the link reaction and Krebs cycle.

Mitochondrial Intermembrane Space

The narrow region between the inner and outer mitochondrial membranes that allows rapid accumulation of protons ($H^+$).

Chloroplast

A double-membraned organelle in plant cells and algae that carries out photosynthesis using absorbed light energy.

Thylakoid Membrane

Internal membrane system of a chloroplast organized into grana stacks, containing photosystems, chlorophyll, electron transport chains, and ATP synthase.

Granum

A stack of flattened disc-like thylakoid membranes within a chloroplast that maximizes surface area for light absorption.

Stroma

The fluid portion of the chloroplast surrounding the thylakoids, containing circular DNA, $70S$ ribosomes, and enzymes for the Calvin cycle.

Nuclear Membrane (Nuclear Envelope)

A double membrane with nuclear pores that encloses genetic material in eukaryotic cells, breaking into small vesicles during mitosis and meiosis.

Free Ribosomes

Unattached ribosomes floating in the cytoplasm that synthesize proteins primarily retained and used within the cell cytosol.

Rough Endoplasmic Reticulum (rER)

A membrane network studded with ribosomes that synthesizes polypeptides destined for transport within vesicles, extracellular secretion, or lysosomal enzymes.

Golgi Apparatus

An organelle composed of flattened sacs called cisternae that modifies, sorts, and packages proteins received from the rough ER into secretory vesicles.

Vesicle

A small membrane-bound phospholipid sac used to store and transport materials throughout the cell.

Clathrin

A triskelion-shaped protein that polymerizes into a cage structure on membranes to induce budding and formation of clathrin-coated vesicles.