Cell Biology Quiz: Cellular Structure and Functions

Cellular Specialization

• Cells become specialized through differentiation or maturation
• Eight specialized cellular functions: movement, conductivity, metabolic absorption, secretion, excretion, respiration, reproduction, and communication

Cellular Structure and Components

• Eukaryotic cells have three main components: plasma membrane, cytoplasm, and intracellular organelles
• Nucleus, the largest organelle, controls genetic information and cellular division
• Cytoplasm (cytosol) is the aqueous solution that fills the space between the nucleus and plasma membrane
• Organelles are enclosed in biological membranes and suspended in the cytoplasm

Endoplasmic Reticulum (ER)

• Network of tubular channels (cisternae) extending through the outer nuclear membrane
• Responsible for protein and lipid synthesis, transport, and protein folding, and stress sensing

Golgi Complex

• Network of smooth membranes and vesicles near the nucleus
• Processes and packages proteins into secretory vesicles for intracellular and extracellular destinations

Lysosomes

• Sac-like structures from the Golgi complex, containing digestive enzymes
• Digest cellular substances (amino acids, fatty acids, carbohydrates)
• Also have a role in nutrient-dependent signal transduction, mediating cell functions like sensing nutrients, adapting to metabolism, and quality control of proteins and organelles

Peroxisomes

• Similar to lysosomes but contain oxidative enzymes (catalase, urate oxidase)

Mitochondria

• Found in abundance in most cells
• Involved in cellular respiration and energy production
• Enzymes in the inner membrane generate ATP, the cell's main energy currency

Cytosol

• Liquid portion of cytoplasm
• Site of intermediary metabolism (enzymatic reactions), ribosomal protein synthesis, and storage of carbohydrates, fat, and secretory vesicles

Cytoskeleton

• Internal skeleton composed of protein filaments (microtubules, actin filaments)
• Provides structural support and movement

Plasma Membrane

• Encloses the cell and controls substance movement
• Lipid bilayer structure with proteins responsible for various functions (receptors, pores, transport channels, enzymes, markers, adhesion molecules)

Membrane Proteins

• Essential for membrane function
• Recognition and binding units (for materials entering/exiting)
• Transport channels
• Active pumps
• Cell surface markers
• Adhesion molecules
• Catalysts for chemical reactions

Protein Synthesis and Transport

• Proteins are made of amino acid chains (polypeptides)
• Proteins move between compartments via gated transport, protein translocation or vesicular transport
• Maintaining the balance of protein synthesis, folding, and degradation (proteostasis) is crucial for cellular health

Cellular Receptors

• Protein molecules on the plasma membrane, cytoplasm, or nucleus
• Recognize and bind to smaller molecules (ligands)
• Initiates cellular signaling cascade

Cell-to-Cell Adhesions

• Formed on plasma membranes enabling tissues/organ formation
• Three mechanisms: extracellular matrix, cell adhesion molecules (CAMs), specialized cell junctions (desmosomes, tight junctions, gap junctions)

Cellular Communication

• Cell communication occurs via three main ways
• Display of plasma membrane receptors impacting itself or other cells
• Activate membrane-bound signaling molecules impacting intracellular receptors
• Forming protein channels (gap junctions) connecting adjacent cells

Signal Transduction

• Conversion of extracellular signals to intracellular responses
• Pathways have multiple functions including signal transfer, amplification, distribution, and modulation
• Examples include cAMP and Ca++ second messenger pathways

Cellular Metabolism

• Chemical tasks necessary for cellular function
• Anabolism (energy-demanding synthesis reactions)
• Catabolism (energy-releasing breakdown reactions)
• ATP is the energy-transferring molecule

Membrane Transport

• Cell survival/growth necessitates constant molecule exchange with the environment
• Simple diffusion of small molecules (O₂, CO₂) across the lipid bilayer
• Specialized membrane transport proteins crucial for transporting other molecules (transporters, channels)
• Active transport requires energy expenditure (e.g., to move large molecules or against concentration gradients)
• Includes passive transport through pores and active transport using energy like ATP

Cellular Reproduction (Cell Cycle)

• Essential for life's continuity
• Continual cell growth and division
• Involves both nuclear division (mitosis) and cytoplasmic division (cytokinesis)
• Interphase, a stage of cellular life, is when cells mature and can divide.
• Cell cycle steps (G1, S, G2, M) involve specific processes like DNA synthesis.