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CELL BIO CH1
| Question | Answer |
|---|---|
| What is Cell Biology? | The scientific study of the structure, function, and behavior of cells |
| What are the three tenets of Cell Theory? | (1) Cells are the fundamental structural and functional units of all living things (2) all living organisms are composed of enclosed cell structures (3) all cells arise only from pre-existing cells through division (omnis cellula e cellula) |
| What four basic characteristics are shared by all cells? | (1) Enclosed by a plasma membrane ; (2) conduct similar biochemical activities via the Central Dogma ; (3) replicate their genome to reproduce ; and (4) evolve over time through mutation and natural selection |
| What is the Plasma Membrane? | A continuous selective barrier that encloses the cell contents, separating the internal cytoplasm from the external environment |
| What are Lipids and what specific structural role do they play in membranes? | Hydrophobic organic molecules that form the primary structural fluid bilayer of the plasma membrane, preventing the uninhibited passage of water-soluble molecules |
| What are Proteins and how do they function within membranes? | Macromolecules composed of amino acid chains ; in membranes, embedded proteins act as selective transporters, ion channels, signal receptors, and structural anchors |
| What are Macromolecules? | Large biological polymers—including proteins, nucleic acids, and polysaccharides—concentrated within the cytosol to form a dense gel-like environment |
| What are Nucleic Acids? | Biological polymers (DNA and RNA) composed of nucleotide sequences that encode, store, and transmit genetic information |
| What is the Central Dogma of Biology? | The fundamental process of genetic expression: DNA nucleotide sequences are transcribed into messenger RNA (mRNA), which is then translated into amino acid chains to form functional proteins |
| What is Transcription? | The synthesis of an RNA molecule from a DNA template strand, occurring inside the nucleus of eukaryotic cells |
| What is Translation? | The synthesis of a protein from an mRNA code, mediated by ribosomes located in the cytosol or on the Rough ER |
| What does Biochemical mean in cell biology? | Refers to the chemical reactions and metabolic pathways—such as energy transformation and molecule synthesis—conducted inside living cells |
| What is Evolution and how does it drive cellular diversity? | The gradual process where genetic mutations combined with natural selection allow cell lineages to adapt to diverse environmental habitats |
| What are Enzymes? | Specialized catalytic proteins that accelerate specific biochemical reactions without being consumed in the process |
| What are the three domains of life? | Bacteria, Archaea, and Eukarya |
| What defines a Prokaryote? | Single-celled organisms lacking a membrane-enclosed nucleus or internal organelles; their circular DNA resides directly in the cytoplasm |
| What are the physical and cellular characteristics of Prokaryotes? | Small diameter (~2.5 µm), enclosed by a rigid outer cell wall, with rapid cell division rates (e.g., doubling in 20 minutes) |
| How do Bacteria and Archaea compare? | Both are prokaryotes, but Archaea possess a unique chemical cell wall structure distinct from bacteria and frequently inhabit extreme environmental niches |
| What defines a Eukaryote? | Organisms whose cells contain a distinct double-membrane-bound nucleus housing linear DNA, alongside a complex suite of membrane-bound organelles |
| What are the structural features of Eukaryotes? | Larger size (~25 µm diameter; 1,000× the volume of prokaryotes) with elaborate internal membrane organization; can exist as unicellular or multicellular organisms |
| What is the difference between a Unicellular Organism and a Multicellular Organism? | Unicellular organisms consist of a single independent cell (e.g., yeast, protozoa); multicellular organisms consist of many specialized, interconnected cells working together |
| How do differentiated cell types form in multicellular organisms? | Specialized cell types (e.g., neurons, muscle cells) possess identical genome sequences but display distinct shapes and functions due to differential gene expression |
| What is a Cell Wall? | A rigid outer layer external to the plasma membrane found in prokaryotes, plants, and fungi that provides structural support and protection against osmotic lysis |
| What is a Microscope and what is a Micrometer (µm)? | A microscope is an optical or electronic instrument used to resolve cellular structures; a micrometer ($10^{-6}\text{ m}$) is the standard unit used to express cell sizes |
| How do Light Microscopy and Electron Microscopy compare? | Light microscopy uses visible light to view live or fixed cells (max magnification 2,000×); Electron microscopy uses electron beams on fixed, non-living specimens to reveal fine organelle ultrastructure (max magnification 10,000,000×) |
| What are Model Organisms and Homologous Genes? | Model organisms (e.g., E. coli, S. cerevisiae, A. thaliana, mice) are studied to uncover universal biological mechanisms ; homologous genes share common evolutionary ancestry and are often functionally interchangeable between species |
| What is an Organelle? | A discrete internal compartment enclosed by one or more lipid membranes that performs a specialized metabolic function within eukaryotic cells |
| What is the Nucleus and Nuclear Envelope? | The largest eukaryotic organelle; houses linear chromosomal DNA and serves as the site of transcription . It is enclosed by a double-membrane nuclear envelope perforated by pores |
| What is a Mitochondrion and what is Cellular Respiration? | A double-membrane organelle that performs cellular respiration, harnessing energy from nutrient breakdown to generate ATP; also regulates programmed cell death (apoptosis) |
| What is ATP (Adenosine Triphosphate)? | The primary chemical energy currency of the cell, generated in mitochondria to power energy-requiring biochemical processes |
| What are Chloroplasts, Chlorophyll, and Photosynthesis? | Chloroplasts are triple-membrane plant/algal organelles containing the green pigment chlorophyll ; they execute photosynthesis to capture light energy and convert it into chemical sugars |
| What is the Endosymbiosis Theory? | The theory that mitochondria and chloroplasts originated when an ancestral anaerobic predatory cell engulfed aerobic or photosynthetic bacteria, establishing a symbiotic relationship; evidenced by their double/triple membranes and distinct organelle DNA |
| What is the Endoplasmic Reticulum (ER)? | An extensive membrane network continuous with the nuclear envelope where lipids and membrane/secreted proteins are synthesized |
| What is the difference between Rough ER and Smooth ER? | Rough ER is studded with ribosomes and synthesizes proteins destined for membranes or secretion ; Smooth ER lacks ribosomes and synthesizes membrane lipids |
| What is a Ribosome? | A molecular machine composed of RNA and proteins (located on the Rough ER or floating in the cytosol) that translates mRNA sequences into amino acid chains |
| What is the Endomembrane System? | A functionally connected network of internal membrane-bound organelles (ER, Golgi, vesicles, lysosomes, plasma membrane) involved in macromolecule synthesis, modification, and transport |
| What is the Golgi Apparatus? | Stacks of flattened, membrane-enclosed sacs that receive proteins and lipids from the ER, chemically modify them, and sort them into vesicles for transport to specific cell locations or secretion |
| What is a Transport Vesicle? | A small, membrane-bound sphere that pinches off from organelle membranes to ship macromolecules between compartments of the endomembrane system |
| What are Endocytosis and Exocytosis? | Endocytosis imports extracellular material into the cell by budding inward from the plasma membrane into vesicles ; Exocytosis exports material out by fusing transport vesicles with the plasma membrane |
| What is a Lysosome? | An acidic, membrane-bound organelle containing hydrolytic enzymes specialized for digesting, breaking down, and recycling unwanted macromolecules, organelles, and debris (primarily in animal cells) |
| What is a Vacuole and what is Turgor? | A large plant organelle (occupying up to 90% of cell volume) that stores nutrients and degrades waste . It maintains turgor—hydrostatic fluid pressure against the cell wall—to keep plant tissues rigid |
| What is a Peroxisome and what are Reactive Oxygen Species (ROS)? | Peroxisomes house oxidative enzymes that neutralize reactive oxygen species (toxic, chemically reactive oxygen byproducts) and oxidize harmful substances to protect the cell |
| What is the Cytosol? | The concentrated, water-based (70% water) gel-like fluid filling the cytoplasm outside internal organelles; site of initial nutrient breakdown and cytosolic protein synthesis |
| What is the Cytoskeleton? | A dynamic network of protein filaments extending throughout the cytosol that provides structural framework, maintains cell shape, and enables cellular movement alongside motor proteins |
| What are Actin Microfilaments? | The thinnest cytoskeletal filaments; responsible for cell shape changes, cell surface movements, and muscle contraction support |
| What are Microtubules? | Thick, hollow tubes that serve as internal tracks for organelle and vesicle transport, pull chromosomes apart during division, and drive cell motility |
| What are Intermediate Filaments? | Tough, rope-like protein fibers that provide high tensile mechanical strength, protecting animal cells against mechanical stress |
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