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BIOL 101: Vocabulary Flashcards on Cellular Structure and Organelles

Opening Questions and Core Concepts

  • Opening Question: Are all living things made of cells?
  • Think-Pair-Share opening prompt to engage with pre-class ideas about cells.
  • Five core points about cells (from the slide):
    1. Basic unit of life
    2. Cells come from pre-existing cells (Cell Theory)
    3. Two types: Prokaryotes and Eukaryotes
    4. Cells divide by binary fission in Prokaryotes; mitosis or meiosis in Eukaryotes
    5. Cells can have organelles (Eukaryotes) and can be specialized

Cell Theory and History

  • Early observations:
    • Robert Hooke observed cells under a microscope in 1665
    • Mathias Schleiden (1838) and Theodor Schwann (1839) contributed to the Cell Theory
  • Core principles of Cell Theory:
    • All organisms are composed of cells
    • Cells are the smallest living things
    • Cells arise only from pre-existing cells
    • All current cells descend from a continuous lineage dating back to the first living cells

Cell Size, Diffusion, and Limits

  • Most cells are relatively small to rely on diffusion for transport of substances in and out of the cell.
  • Factors affecting diffusion rate:
    • Surface area available
    • Temperature
    • Concentration gradient
    • Distance (diffusion distance)
  • Cell size limitation concept:
    • As cells increase in size, volume grows faster than surface area, limiting rate of exchange with the environment
  • Practical strategy: organisms can be composed of many small cells rather than a few large cells to maintain adequate exchange

Surface Area-to-Volume Considerations

  • A compact, large organism built from many small cells has an SA:V advantage over a single large cell.
  • As a cell’s size increases, its volume increases more rapidly than its surface area, reducing the relative surface area for exchange.
  • A biological solution to this limitation: some cells become long and narrow (e.g., neurons) to increase surface area relative to volume

Microscopy and Cell Size Facts

  • Most cells are not visible to the naked eye; typical cells are less than 50\,\mu\text{m} in diameter
  • Resolution: the minimum distance at which two points can be distinguished as separate points
  • Naked eye can resolve two objects only if they are at least 100\,\mu\text{m} apart

Major Cell Types: Prokaryotes vs Eukaryotes

  • Two broad categories:
    • Prokaryotic cells: Bacteria and Archaea
    • Eukaryotic cells: Plants, Animals, Fungi, Protists
  • Basic structural similarities (shared features):
    • Nucleoid or nucleus where DNA is located
    • Cytoplasm ( semifluid matrix containing organelles and cytosol )
    • Ribosomes (protein synthesis units)
    • Plasma membrane (phospholipid bilayer)
  • Key differences:
    • Eukaryotes: compartmentalized cytoplasm with membrane-bound organelles including a nucleus
    • Prokaryotes: lack a true nucleus and membrane-bound organelles; smaller and simpler
  • Origin timing (overview):
    • Prokaryotes appeared around 3.5\text{ BYA} (older lineage)
    • Eukaryotic cells appeared around 2.1\text{ BYA} (later lineage)

Prokaryotic Cells: Structure and Features

  • Basic features:
    • Lack a membrane-bound nucleus
    • DNA in a nucleoid
    • A cell wall outside the plasma membrane
    • Contain ribosomes
  • Cellular organization:
    • No membrane-bound organelles common to all prokaryotes
    • Some organelles or structures with specific functions (e.g., magnetosomes, infoldings of the plasma membrane)
  • Prokaryotic diversity:
    • Two domains: Archaea and Bacteria
    • Bacteria can be pathogens; Archaea have no known pathogens in humans
  • Prokaryotic cell walls and outer structures:
    • Bacterial cell walls typically composed of peptidoglycan (contrast with plants, fungi, and protists walls)
    • Capsule, glycocalyx, fimbriae, pili, flagella as additional structures
    • Plasma membrane lies beneath cell wall; can harbor infoldings that compartmentalize reactions
  • Prokaryotic microcompartments:
    • Bounded by a protein shell, 40–400 nm in size
    • Function: isolate specific metabolic processes or store materials
  • Cytoskeleton in prokaryotes:
    • Molecules related to actin and tubulin exist and influence the cell wall’s shape and strength
  • Prokaryotic cell walls and antibiotics:
    • Susceptibility to antibiotics often depends on the structure of the cell wall

Prokaryotic Cell Complexity: Special Features

  • Some prokaryotes contain organelles with specific functions (not universal organelles like in eukaryotes)
  • Magnetosomes: magnetic storage organelles in certain bacteria
  • Endomembrane-like infoldings: folds of the plasma membrane that organize metabolic reactions
  • Bacterial microcompartments: protein-bound organelle-like structures for specific metabolic tasks

Eukaryotic Cells: Structure and Organization

  • Hallmark feature: membrane-bound nucleus and compartmentalization
  • Endomembrane system and cytoskeleton:
    • Endomembrane system includes nuclear envelope, ER, Golgi, lysosomes, vacuoles, plasma membrane
    • Cytoskeleton provides structural support and aids movement
  • Two major cell types: animal cell and plant cell (structural differences summarized later)

The Nucleus and Genetic Information

  • Nucleus: repository of most cell DNA
  • Nucleolus: site of ribosomal RNA (rRNA) synthesis
  • Nuclear envelope: a double phospholipid bilayer that regulates traffic between nucleus and cytoplasm
  • Nuclear pores: control movement in and out of the nucleus
  • Chromosomes: multiple linear DNA-protein complexes in eukaryotes
  • Chromatin: DNA plus protein, forming chromosomes during cell division

Ribosomes and Protein Synthesis

  • Ribosomes: the cell’s protein synthesis machinery; present in all cell types across domains
  • Components:
    • Ribosomal RNA (rRNA) + proteins
    • Messenger RNA (mRNA) and transfer RNA (tRNA) are required for translation
  • Localization: ribosomes can be free in the cytoplasm or attached to the rough endoplasmic reticulum (RER)
  • Ribosome subunits: large and small subunits (illustrated in structure figures)

Endomembrane System and Transport

  • Concept: series of membranes throughout the cytoplasm that divide the cell into functional compartments
  • Major components: Nuclear envelope, Endoplasmic Reticulum (ER), Golgi apparatus, Lysosomes, Vacuoles, Plasma membrane
  • Connectivity: components are continuous or connected via transfer by vesicles
  • Protein production pathway (two-step overview):
    • Transcription in the nucleus produces RNA from DNA
    • Translation at ribosomes produces proteins
    • Proteins move through the Golgi apparatus for processing and sorting

Endoplasmic Reticulum (ER)

  • Rough ER (RER):
    • Bound ribosomes give rough appearance
    • Site of synthesis of proteins that will be secreted, sent to lysosomes, or inserted into the plasma membrane
  • Smooth ER (SER):
    • Lacks bound ribosomes
    • Functions: various synthesis and storage roles; the ratio of RER to SER depends on the cell’s function

Golgi Apparatus

  • Structure: flattened stacks of interconnected membranes (cisternae) with cis and trans faces
  • Functions:
    • Modifies, packages, and ships proteins synthesized in the ER
    • Vesicles transport proteins to their destination (plasma membrane, lysosomes, etc.)
  • Transport process (illustrated in figures):
    • Vesicle bud from RER fuses to cis face of Golgi
    • Proteins are modified and packaged into vesicles for transport
    • Vesicles may travel to the plasma membrane to release contents outside the cell

Lysosomes and Digestion

  • Lysosomes: membrane-bounded digestive vesicles that arise from the Golgi
  • Contain hydrolytic enzymes that break down macromolecules
  • Functions:
    • Digest and recycle old organelles
    • Digest ingested particles or foreign matter via phagocytosis
  • Visual pathways show fusion with old/damaged organelles and digestion of material

Microbodies and Vacuoles

  • Peroxisomes (a type of microbody):
    • Contain enzymes involved in fatty acid oxidation
    • Produce hydrogen peroxide as by-product and detoxify it with catalase
  • Lipid droplets: contain neutral lipids; membrane components and signaling molecules; transport lipids to mitochondria and peroxisomes
  • Vacuoles:
    • Plant cells often have large central vacuoles
    • Other vacuoles include storage vacuoles in plants and contractile vacuoles in some fungi and protists

Mitochondria

  • Structure: two membranes (outer and inner with cristae), intermembrane space, matrix
  • Function: sites of oxidative metabolism; harvest energy from food molecules
  • Unique features:
    • Contain their own DNA
    • Proteins involved in energy metabolism are located on the inner membrane and in the matrix

Chloroplasts and Photosynthesis

  • Chloroplasts: present in plants and some other eukaryotes
  • Structure: two membranes, contain chlorophyll for photosynthesis; internal thylakoid membranes form a granum/grana
  • Genetic material: chloroplasts have their own DNA

Endosymbiosis Theory

  • Proposes that some present-day eukaryotic organelles evolved through symbiosis between two free-living cells
  • Key idea: mitochondria and chloroplasts resemble prokaryotic cells in some ways
  • Visual representations show evolutionary steps from prokaryotic bacteria and cyanobacteria to modern organelles

Cytoskeleton and Cell Architecture

  • Cytoskeleton: network of protein fibers that provides shape, support, and tracks for movement
  • Three main types of fibers:
    • Microfilaments (actin filaments): involved in contraction and cell crawling
    • Microtubules: large; facilitate movement of cell and materials; composed of tubulin subunits
    • Intermediate filaments: very stable; provide structural support
  • Organization includes actin filaments, microtubules, and intermediate filaments components in the cell
  • Visuals show the cytoskeleton interacting with the plasma membrane, nucleus, and organelles

Centrosomes, Centrioles, and Microtubule Organization

  • Centrosomes: region surrounding centrioles; major microtubule-organizing center in many animal cells
  • Centrioles: often present as pairs in animal cells; plants and fungi typically lack centrioles
  • Centrosomes/centrioles coordinate microtubule assembly during cell division
  • Visual depictions emphasize anaphase and chromosomal movement in meiosis as a related context

Cell Movement and Cilia/Flagella

  • Movement in eukaryotic cells involves actin filaments and/or microtubules
  • Some cells crawl using actin-based motility
  • Eukaryotic flagella and cilia have a 9+2 arrangement of microtubules: nine doublet microtubules surrounding two central singlet microtubules
  • Cilia are shorter and more numerous than flagella
  • Internal structure of flagella and cilia shown in cross-section illustrations

Eukaryotic Cell Walls and Extracellular Environment

  • Eukaryotic cell walls: present in plants, fungi, and some protists; distinct in composition and structure from prokaryotic walls
    • Plant cell walls: primarily cellulose
    • Fungi cell walls: primarily chitin
    • Protists may have varied composition
  • Animal cells typically lack cell walls; plant cells retain cell walls
  • Extracellular Matrix (ECM) in animal cells:
    • Lacks a cell wall; secretes glycoproteins (e.g., collagen) into the surrounding matrix
    • Integrins link the ECM to the cytoskeleton and influence cell behavior

Plant Cell Special Features

  • Plant cells possess rigid cell walls made of cellulose; provide structural support
  • Chloroplasts and large central vacuoles are characteristic
  • Plasmodesmata: specialized channels through cell walls that connect cytoplasm of neighboring plant cells; functionally analogous to gap junctions in animal cells

Plant vs Animal Cells: Overview of Shared and Distinct Features

  • Both share: plasma membrane, many organelles (nucleus, ER, Golgi, ribosomes, mitochondria, cytoskeleton, etc.)
  • Plant cells: have cell wall, chloroplasts, and large central vacuoles
  • Animal cells: lack cell walls and chloroplasts; ECM is prominent; have centriole-containing centrosomes in most animal cells

Table 4.3: A Quick Comparison of Prokaryotic, Animal, and Plant Cells (Highlights)

  • Exterior structures:
    • Prokaryotes: cell wall present; plasma membrane; flagella/cilia may be present
    • Animal: cell wall absent; membrane present; flagella/cilia may be present in some species (9+2 structure in a few cases, e.g., sperm)
    • Plant: cell wall present (cellulose); plasma membrane; flagella/cilia absent in most plant cells
  • Interior structures:
    • Prokaryotes: ER absent; ribosomes present; no true nucleus; microtubules absent; Golgi absent; nucleus absent; mitochondria absent; chloroplasts absent; chromosomes are circular DNA in the nucleoid
    • Animal: ER present; ribosomes present; nucleus present; microtubules present; Golgi present; mitochondria present; chloroplasts absent
    • Plant: ER present; ribosomes present; nucleus present; microtubules present; Golgi present; mitochondria present; chloroplasts present; cell wall outside plasma membrane; large central vacuole
  • Overall takeaway: Prokaryotes are simpler with no membrane-bound organelles; Eukaryotes (animal and plant) have compartmentalization and a true nucleus; plant cells add chloroplasts and a cell wall

Cell-to-Cell Interactions and Junctions

  • Surface proteins provide cell identity; cells can recognize and respond to other cells
  • Glycolipids serve as tissue-specific cell surface markers
  • Major immune-related marker: MHC proteins (self vs non-self recognition)
  • Types of cell junctions:
    • Adhesive junctions: mechanically attach cytoskeletons of neighboring cells or cells to the extracellular matrix (include adherens junctions, desmosomes, hemidesmosomes)
    • Septate or tight junctions: seal adjacent cell membranes to prevent leakage between cells
    • Communicating junctions: allow chemical or electrical signals to pass directly between adjacent cells (gap junctions, plasmodesmata in plants)
  • Diagrammatic examples illustrate animal cell junctions and their roles

Plant-Specific Cell Connections: Plasmodesmata

  • Plasmodesmata are channels through plant cell walls that connect cytoplasm of neighboring cells
  • Functionally similar to gap junctions in animal cells, enabling intercellular transport and signaling

Syllabus, AI Policy, and Course Logistics (Context for Course Planning)

  • AI usage in the course is not permitted
  • Lecture and Lab attendance are graded and mandatory
  • All tasks accessed/submitted in Blackboard (LMS)
  • Connect tutorials and Smartbook assignments determine course progress
  • Chapter 1, 4, and 5 assignments have deadlines (example provided: Friday, August 29, 2025, 11:59 pm)
  • Course materials reference McGraw Hill Connect resources for registration, support, and contact information

Quick Review and Key Takeaways

  • Cells are the basic units of life with a rich diversity of structure and function across prokaryotes and eukaryotes
  • Eukaryotes exhibit compartmentalization via organelles and the endomembrane system; prokaryotes are simpler but highly diverse
  • The nucleus houses genetic material; the ER, Golgi, lysosomes, and vacuoles coordinate synthesis, processing, and trafficking of cellular products
  • Mitochondria and chloroplasts are energy-related organelles with evidence supporting endosymbiosis
  • The cytoskeleton provides structural support and drives movement; centrosomes/centrioles organize microtubules during cell division (especially in animal cells)
  • Plant and animal cells share many components but differ in the presence of a cell wall, chloroplasts, and a central vacuole in plants
  • Cell-to-cell communication and junctions regulate tissue integrity and intercellular signaling; plasmodesmata connect plant cells across cell walls
  • Understanding these structures and processes lays the groundwork for topics in physiology, development, and cell biology