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Cell biology and study strategies — Transcript notes

Exam logistics and support resources

  • Assignment: second case study on biological molecules due this evening at midnight; no late penalties if you miss the deadline, but avoid turning in a page full of copied content.
  • If you need more time: you can take longer this week or next; the instructor encourages putting in the time for the assignment.
  • Help video: a recording is available to help you approach each question and locate relevant slides/information; it’s in Canvas under the first unit (Week 4 area) alongside the case study materials.
  • If you’re stuck: use the help video and the available recording; take the time you need.
  • Location note: the assignment may be tucked under the chemistry part in Canvas; look for Week four → Case study → recording explaining how to approach questions and where slides/info are.
  • Pearson pre-reading: Chapter 6 (on large cellular structures and organelles) is due Thursday before class.
  • Exams and grades: exam grades posted on Canvas; you can view them there; you can attend office hours for feedback.
  • Office hours: regular hours Wednesday and Friday at 10:00; open to all; space can be tight.
  • Exam review sessions: set aside as additional support, with three scheduled times mentioned; times shown on Canvas and in slides; one Friday session is longer; one Friday session is shorter due to a faculty meeting; there may be an additional session added (e.g., Friday late afternoon or Monday early afternoon) depending on room availability and student preference.
  • How review sessions work: instructor will have answer keys, exam copies with marked answers, and each student's Scantron so you can review your responses, discuss with others or with the instructor; drop-in format; you can attend part or all of the session.
  • Ethics and fairness reminder: an incident occurred where someone left with an exam packet; the instructor stresses ethics as critical in science and education; if you’re involved or know anything, please discuss with the instructor to maintain fairness for all students.
  • Exam retake policy: you can retake one exam at the end of the semester; the retake replaces the original grade if it’s higher; most students retake the first exam to improve understanding and adapt study strategies; retakes may involve different questions.
  • Questions about retakes or exam reviews: encouraged to ask; the instructor aims to be transparent about logistics and fairness.
  • Study strategies overview: two systematic approaches (study cycle and planning/goal-oriented study) drawn from LSU Center for Academic Success; the emphasis is moving beyond passive reading to active discussion and practice; ideas include studying with peers, explaining material to others, and practicing application of concepts.
  • Standing encouragement: most students improve over time with the right strategies; the first exam is a common rough start, but it’s not indicative of overall performance; there are opportunities to adjust and improve.
  • Bloom’s taxonomy reference: the instructor introduces levels of cognitive demand (remembering, understanding, applying, analyzing, etc.) to structure practice questions; you can use tools like ChatGPT to generate questions at different taxonomy levels to scaffold learning.
  • Open invitation for strategy brainstorming: the instructor is available to discuss new study strategies and to tailor approaches to individual schedules and learning styles.
  • Transition to content: after the study strategies, we’ll apply these ideas to examining cells and cellular structure.

Study strategies and the study cycle

  • Before class (priming): preread the chapter; identify which parts click and which are challenging; note questions and rusty areas to address in class.
  • Use chapter objectives and end-of-chapter summaries to distill key points; these are helpful for focusing reading and guiding learning goals.
  • Create a study guide aligned with learning objectives; while reading, focus on specific targets (e.g., the ratio of atoms in carbohydrates) rather than trying to memorize everything.
  • Note-taking guidance: don’t try to transcribe every slide; capture big takeaways, questions that clarified concepts, and anything the instructor emphasized that helped your understanding.
  • After class (self-assessment): review exit tickets and questions; identify remaining struggles and consider SI or office hours for clarification.
  • Spacing and distribution: avoid studying the night before an exam; spread practice into shorter sessions across days (e.g., 20–25 minutes daily or several short sessions per week).
  • Group study and peer explanations: explain concepts to others to reinforce your own mastery; group study can reveal gaps and deepen understanding.
  • SI sessions and collaborative learning: use SI or general study partners; even one partner can be highly effective; you can meet in person or via Zoom.
  • Active learning strategies: generate your own practice questions; use study guides or online tools (e.g., ChatGPT) to create questions aligned to objectives; practice with others to reinforce understanding.
  • Planning study sessions: set a concrete, achievable goal for each session (e.g., review functional groups for 20 minutes, tackle two learning objectives on nucleic acids); identify questions you’ll email to the instructor.
  • Breaks and momentum: schedule short breaks after focused study blocks to maintain momentum; use the 25-minute focus + 5-minute break cycle to overcome procrastination.
  • Periodic self-assessment: use practice questions, study guides, dynamic study modules, or retaking practice quizzes to measure progress; adjust focus accordingly.
  • Bloom’s taxonomy in practice: start with level-1 remembering questions, then build to level-2 or level-3 applying and analyzing questions to deepen mastery.
  • Personal adaptation: strategies should be tailored to your learning style and schedule; the instructor can help brainstorm techniques that work for you.

Cells: cell theory, structure, and microscopy

  • Core goals for today: why cells are small; overall cell structure shared by prokaryotes and eukaryotes; deep dive into the cytosol (fluid inside the cell) and the cytoskeleton (cell shape and movement).
  • Cell theory recap: cells are the fundamental unit of life; all organisms are composed of one or more cells; cells arise from pre-existing cells via division; applies to unicellular and multicellular organisms; internal regulation and environmental sensing are universal cellular traits.
  • Early visualization limits: before microscopy, cell study was hindered by tiny cell size; advances in microscopy enabled foundational ideas about cellular life and reproduction.
  • Miller–Urey context (brief): experiments on the origin of large biological molecules; RNA as primitive genetic material; cell membranes can form spontaneously from phospholipids; with energy and building blocks, early cellular systems could emerge; leads to first cells arising from combinations of molecules and membranes; many early cells died, but some survived and contributed to evolution.
  • Microscopy types:
    • Light microscope: uses visible light to visualize cells and some organelles (nucleus, mitochondria) and can show big structures.
    • Electron microscope: uses electrons to visualize much smaller structures; two main types:
    • Scanning electron microscope (SEM): 3D-like surface imaging of samples (great for outer structures).
    • Transmission electron microscope (TEM): cross-sections to view internal structure at high resolution.
  • UNCW microscopy facility: located in DoVal Hall; has electron and fluorescent microscopes; undergraduates can use these for research; unique access to staining and imaging facilities that many schools don’t offer to undergrads; possible campus tours/open hours during the semester.
  • Why cells are small: small size improves surface area-to-volume (SA:V) ratio, which helps nutrient uptake and waste removal; larger cells have higher nutrient demand that cannot be met by the limited surface area that scales with the square of radius, while volume scales with the cube of radius.
  • Mathematical relation:
    • Surface area: SA = 4 \, \pi \, r^2
    • Volume: V = \frac{4}{3} \, \pi \, r^3
    • SA:V ratio: \frac{SA}{V} = \frac{3}{r}
  • Example with radius r = 1:
    • \frac{SA}{V} = 3
  • Effect of increasing radius:
    • Increasing r reduces the SA:V ratio; e.g., r = 2 gives \frac{SA}{V} = \frac{3}{2} = 1.5; r = 3 gives \frac{SA}{V} = 1, meaning nutrient supply exactly matches demand.
  • Intuition of the SA:V concept: smaller cells have more surface area relative to their volume, enabling more efficient nutrient uptake and waste removal; as cells grow, supply fails to keep up with demand, prompting division to maintain efficiency.
  • Enterocytes and intestinal surface area (practical example of SA:V):
    • Enterocytes line the intestinal wall and have microvilli (folds in the cell membrane) that dramatically increase surface area to enhance nutrient absorption.
    • Higher SA:V is advantageous for absorptive cells, enabling more nutrients to be absorbed from digested material.
    • In contrast, other cell types (e.g., in the arm or eye) may have lower SA:V and differ in absorptive needs.
  • Structure-to-function link in the intestine: microvilli increase SA to boost nutrient uptake; folds in membranes are a tiny-scale reflection of the larger intestinal surface that resembles a highly convoluted surface.
  • Prokaryotes vs. eukaryotes in size and organization:
    • Prokaryotes (archaea and bacteria): generally smaller; lack a true nucleus; DNA is not enclosed in a membrane-bound organelle; often more generalist in environmental tolerance.
    • Eukaryotes (plants, animals, fungi, many algae): larger; contain a true nucleus; membrane-bound organelles; greater compartmentalization supports specialization and complex metabolism.
  • Five shared cellular features (present in all cells):
    • Genetic material: DNA or nucleic acids stored in a central location (nucleus in eukaryotes; not enclosed in a nucleus in prokaryotes).
    • Ribosomes: protein synthesis factories; essential for producing cellular proteins.
    • Cytoskeleton: structural network to maintain shape, anchor organelles, and facilitate movement.
    • Cytosol: fluid interior (mostly water) with dissolved nutrients and ions; site of various metabolic reactions.
    • Cell membrane: phospholipid bilayer that encloses the cell and regulates internal vs external environments.
  • Cytosol and metabolism:
    • Cytosol is the aqueous interior containing soluble molecules and ions; site of initial metabolic steps, including the first stages of energy production in cellular respiration as described in the lecture.
    • Cytosol also participates in signaling and some protein synthesis via floating ribosomes.
  • Cytoskeleton overview: structural framework that enables shape, organization, and movement; connects organelles and forms intracellular highways.
  • Cytoplasmic streaming and amoeba movement: amoeba moves by cytoplasmic streaming, where cytoskeleton-driven shape changes cause membrane projections to extend and pull the cell forward.
  • Cytoskeleton components and their classification (by fiber width and protein composition):
    • Microfilaments (actin; ~7 nm diameter): smallest; dynamic; maintain cell shape; enable movement; drive cytokinesis; contribute to muscle contraction when organized into actin filaments.
    • Intermediate filaments: medium size; provide stability and mechanical strength; anchor the nucleus and organelles; maintain cell and nuclear shape (e.g., nuclear lamina).
    • Microtubules: largest; hollow tubes; formed from tubulin dimers (alpha and beta tubulin); radiate from centrosomes to form networks; serve as cellular highways for cargo transport; organize chromosomes during cell division; powers flagellar/ciliary movement in some cells (e.g., sperm tail).
  • Microtubule and motor functions: microtubules create networks that transport organelles and chromosomes; dynamic instability supports rapid reorganization during cell division and movement.
  • How compartmentalization helps larger cells (eukaryotes): separating reactions into organelles concentrates substrates and enzymes, maintains distinct pH and chemical environments, and enables segmented processes (e.g., assembly lines for sequential steps).
  • Prokaryotic simplicity vs. eukaryotic compartmentalization: prokaryotes lack a true nucleus and lack membrane-bound organelles; eukaryotes compartmentalize functions to improve efficiency and complexity as they grow.
  • Practical takeaway on organization: compartmentalization is a key driver behind the evolution of larger, more complex cells.

The five universal cell features in detail

  • Genetic material: DNA or nucleic acids stored within the cell; in eukaryotes, DNA is enclosed in a nucleus; in prokaryotes, DNA is generally in a nucleoid region without a separate membrane.
  • Ribosomes: tiny RNA-protein complexes that synthesize proteins; present in all cells; drive production of enzymes and structural proteins.
  • Cytoskeleton: network of protein filaments (microfilaments, intermediate filaments, microtubules) providing shape, internal organization, transport routes, and mechanical support.
  • Cytosol: the fluid matrix inside the cell, mostly water with dissolved ions, nutrients, and solutes; site of some metabolic reactions and signaling; fills the cell volume around organelles.
  • Cell membrane: lipid bilayer that encloses the cell; controls movement of substances in and out; maintains homeostasis; participates in signaling and interactions with the environment.
  • Note: these five features are shared by both prokaryotic and eukaryotic cells, though the organization and presence of a nucleus and organelles differ between the two groups.

The cytoskeleton: microfilaments, intermediate filaments, and microtubules

  • Microfilaments (actin; smallest, ~7 nm):
    • Dynamic, form dense networks just under the cell membrane.
    • Maintain cell shape and support membrane protrusions.
    • Enable cell movement via cytoplasmic streaming and muscle contraction (in muscle cells, actin filaments interact with myosin).
    • Important for cytokinesis during cell division by pinching the cell membrane to split cells.
  • Intermediate filaments (size between microfilaments and microtubules):
    • Form stable, durable networks throughout the cytoplasm.
    • Anchor and stabilize organelles, maintain nuclear shape (lamina) and overall cell integrity.
    • Provide structural support rather than driving movement.
  • Microtubules (largest, hollow tubes):
    • Composed of alpha-tubulin and beta-tubulin dimers; radiate from organizing centers to form a dynamic cytoskeletal network.
    • Act as highways for intracellular transport of vesicles and organelles; motor proteins move along microtubules.
    • Play a central role in chromosome movement during cell division (attach to chromosomes and help pull sister chromatids apart).
    • Involved in cell motility for certain cells that use flagella or cilia; movement is achieved by bending patterns driven by microtubule sliding.
  • Visual takeaway: microfilaments provide flexibility and surface interactions, intermediate filaments provide stability, and microtubules provide highways and organization for movement and division.
  • Recap of terms:
    • Cytoskeleton components are categorized by fiber width and protein makeup.
    • Each type has distinct roles but all contribute to shape, organization, and dynamics of the cell.

Cytosol, movement, and cellular processes

  • Cytosol essentials:
    • The intracellular fluid mostly composed of water with dissolved ions, small and large molecules.
    • Site of many metabolic pathways and initial energy extraction steps.
    • Facilitates diffusion of molecules and the movement of proteins within the cell.
  • Cytoplasmic streaming (movement mechanism):
    • Amoeba-like cells move by extending membrane projections; cytoskeleton rearrangements push out parts of the membrane, and cytosol flows to fill the space, pulling the cell forward.
  • Role in metabolism: cytosol hosts initial metabolic processes and provides a medium for signaling and protein synthesis (some ribosomes are in the cytosol).
  • Movement and structure interplay: cytoskeleton reorganizes to enable shape changes and directional movement.

Prokaryotes vs. eukaryotes: compartments and organization (summary)

  • Prokaryotes:
    • No true nucleus; DNA is not membrane-bound.
    • Generally smaller; often generalists; limited compartmentalization.
  • Eukaryotes:
    • True nucleus; membrane-bound organelles; larger cells.
    • Compartmentalization allows specialization and complex regulation of metabolism.
    • Organelles create functional regions (e.g., mitochondria for energy, lysosomes for degradation, Golgi for protein processing, etc.).
  • Shared features (revisited): genetic material, ribosomes, cytoskeleton, cytosol, and cell membrane.
  • Functional advantage of compartments: enables more complex chemistry, greater efficiency, and the ability to localize incompatible reactions in separate spaces.

Key terms and concepts referenced in the lecture

  • Cell theory: cells are the fundamental unit of life; all life is composed of one or more cells; new cells come from existing cells via division.
  • SA:V concept and geometry:
    • Surface area: SA = 4 \pi r^2
    • Volume: V = \frac{4}{3} \pi r^3
    • Surface-area-to-volume ratio: \frac{SA}{V} = \frac{3}{r}
  • Enterocytes and microvilli: intestinal cells have folded membranes (microvilli) to increase nutrient absorption.
  • Miller–Urey and origin of life notion: early molecules and membranes formed spontaneously under abiotic conditions; genetic material and energy pathways developed over time to yield primitive cells.
  • Microscopy recap: light vs electron microscopy; SEM (surface detail) vs TEM (internal detail); UNCW facility advantages for undergraduates.
  • Big-picture takeaway: cells are small because SA:V constraints influence nutrient uptake and waste removal; compartmentalization in eukaryotes enables larger, more specialized cells.

Practical implications and connections

  • Ethics in science: integrity in exams and data handling is crucial for fairness and scientific credibility; cheating undermines trust and learning.
  • Study strategies in practice: active learning, peer explanation, and spaced practice have shown to improve mastery beyond passive reading; apply to exam prep and case studies.
  • Real-world relevance: understanding SA:V implications helps explain why tissues like intestinal epithelium have microvilli; organelle compartmentalization is foundational to modern cell biology and is reflected in examples like specialized tissues and organ systems.
  • The microscopy facility at the university demonstrates how access to advanced tools can enable hands-on experiences, bridging theory and real-world lab work for undergraduates.

Quick recap equations and numbers to memorize

  • Surface area: SA = 4 \pi r^2
  • Volume: V = \frac{4}{3} \pi r^3
  • SA:V ratio: \frac{SA}{V} = \frac{3}{r}
  • Sample evaluation for radius values:
    • If r = 1, then \frac{SA}{V} = 3
    • If r = 2, then \frac{SA}{V} = 1.5
    • If r = 3, then \frac{SA}{V} = 1

Next steps and reminders

  • Review the Pearson Chapter 6 pre-reading before Thursday’s class; connect it to the upcoming exam material.
  • Consider attending the exam review sessions (three time slots, with possible additional session) and take advantage of the opportunity to review answer keys and personalized feedback.
  • If you’re exploring research opportunities, check out UNCW’s microscopy facility and discuss with instructors or SI leaders about potential undergraduate research options.
  • If you’re uncertain about study strategies or how to implement these techniques in your schedule, reach out to the instructor to brainstorm tailored approaches.
  • Prepare for upcoming topics: more about metabolism, organelle function, and advanced cellular processes; expect integrative problems that apply the study strategies discussed.