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Cell Biology Core Concepts

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  • Functions of Rough and Smooth ER

    Rough ER is involved in protein synthesis. Smooth ER functions in drug detoxification, carbohydrate metabolism, calcium storage, and steroid biosynthesis.

  • Golgi Apparatus Roles

    The Golgi has cis- and trans- sides and is responsible for membrane and protein processing, sorting, and trafficking.

  • Lysosome Function and Origin

    Lysosomes degrade major macromolecules, develop from endosomes, and maintain an acidic environment for digestion.

  • Anterograde vs Retrograde Trafficking

    Anterograde transport moves materials from ER to Golgi to plasma membrane; retrograde transport moves materials backward to earlier compartments.

  • Cotranslational Import Mechanism

    Proteins with signal sequences are recognized by SRP, targeted to the ER translocon, where they fold and process; integral membrane proteins insert via stop-start sequences.

  • Protein Sorting Signals

    Proteins have retention and retrieval tags such as amino acid sequences, hydrophobic region length, and covalent modifications to direct their localization.

  • Types of Endocytosis

    Includes receptor-mediated endocytosis, phagocytosis, and pinocytosis; receptor-mediated involves clathrin, adaptor proteins, and dynamin for vesicle formation.

  • Coated Vesicles and Their Functions

    Clathrin-coated vesicles mediate endocytosis; COPI vesicles mediate retrograde Golgi to ER transport; COPII vesicles mediate anterograde ER to Golgi transport.

  • SNARE-Mediated Membrane Fusion Components

    Fusion requires v-SNAREs, t-SNAREs, tethering proteins, Rab GTPases, NSF, and SNAPs to mediate vesicle docking and fusion.

  • Neuron Types in the Nervous System

    Neurons include sensory, motor, and interneurons; glial cells include microglia, oligodendrocytes, Schwann cells, and astrocytes.

  • Phases of Neuron Action Potential

    Action potential phases: depolarization (Na+ influx), repolarization (K+ efflux), and hyperpolarization (excess K+ efflux).

  • GPCR Signaling Pathway Overview

    GPCRs activate heterotrimeric G proteins; Gα subunit switches between GDP (off) and GTP (on); downstream effectors include adenylyl cyclase and phospholipase C.

  • Gsα and Gqα Signaling Effects

    Gsα activates adenylyl cyclase to increase cAMP and activate PKA; Gqα activates PLC producing IP3 and DAG, increasing cytosolic Ca2+ via ER channels.

  • RTK Activation and Signaling Cascade

    RTKs dimerize and autophosphorylate upon ligand binding, recruit adaptor proteins, activate Ras, and trigger MAP kinase cascade leading to gene expression.

  • Microtubule Dynamics

    Microtubules show polarity, require GTP for assembly, and exhibit dynamic instability with phases of growth (rescue) and shrinkage (catastrophe).

  • Microtubule Organizing Centers (MTOCs)

    MTOCs include centrosomes and basal bodies; gamma-tubulin nucleates microtubule assembly at these sites.

  • Actin Filament Structures and Locations

    Actin filaments form stress fibers, gel-like networks, branched and parallel arrays found in trailing edge, cortex, lamellipodia, and filopodia.

  • Motor Proteins on Microtubules

    Kinesins move cargo toward microtubule plus ends; dyneins move toward minus ends; both use ATP as energy source.

  • Muscle Contraction Mechanism

    Myosin thick filaments slide along actin thin filaments in sarcomeres; contraction regulated by troponin, tropomyosin, and Ca2+ ions.

  • Major Cell-Cell Junction Types

    Includes adhesive junctions (adherens, desmosomes), tight junctions, gap junctions, and plasmodesmata in plants.

  • Extracellular Matrix Protein Types

    Major ECM proteins are collagens, elastins, proteoglycans, fibronectins, and laminins; basal lamina is a specialized ECM layer.