Cell Biology Basics Quiz

Structured Study Sessions (SSS)

• Bio 120 SSS sessions led by Janelle and Steve
• Offered September 17, 2024
• Materials developed by peer mentors, not course professors
• Session content selected based on peer mentor knowledge, experiences, and input from the SSS Peer Mentor Team

What is SSS?

• Structured study sessions (SSS)
• Weekly sessions reviewing course material
• Opportunities to ask questions and better understand topics
• Four 80-minute sessions per week, students can attend any or all
• Focuses on deepening lecture material understanding
• Sessions facilitated by peer mentors who have previously taken and excelled in Bio 120

Icebreaker Activity

• Students introduce themselves, their program, and a favorite aspect of university

In This Session

• Topics covered in session include:
  • Macromolecules
  • Early Microscopy
  • Cell Theory
  • Microscopy types and their uses
  • Features common to all cells
  • Prokaryotic vs. eukaryotic cells

Let's See What You Already Know!

• Introduction to a knowledge check activity

Question 1 - Cell Theory

• Option B is part of the cell theory: Cells arise when pre-existing cells divide

Question 2 - Magnification

• Option A describes magnification: The ratio of the object as you see it under the microscope to its real size.

Question 3 - Prokaryotic Cells

• Option A (Nucleus) is not found in prokaryotic cells

Macromolecules

• Life is composed of four macromolecules:
  • Proteins (monomer: amino acids)
  • Nucleic acid (DNA/RNA, monomer: nucleotides)
  • Carbohydrates (monomer: monosaccharides)
  • Lipids (not made of monomers)

Hooke and van Leeuwenhoek

• Hooke: First to use a microscope to observe cells
• van Leeuwenhoek: First to use a microscope to observe living organisms (pond water, bacteria)

Cell Theory

• Proposed in the mid-19th century
• Three key tenets:
  • All organisms are made of one or more cells
  • The cell is the basic structural and functional unit of all living organisms
  • Cells only arise when pre-existing cells divide

Overview of Cells

• Cells carry out essential life processes
• Cells are too small to be seen without a microscope
• All cells contain a central region with DNA surrounded by cytoplasm
• Cells utilize DNA and RNA for genetic information and protein synthesis
• Cells utilize energy, respond to environmental changes, reproduce, and transmit genetic information
• Two main types of cells: prokaryotic and eukaryotic

Light Microscopy

• Uses light to illuminate the specimen
• Advantages: living specimens, inexpensive
• Ideal for: bacteria, protists, larger cells, plasma membrane, nucleus and organelles
• Types include bright field, phase contrast, dark field, and confocal laser scanning microscopy (with different advantages in usage)

Electron Microscopy

• Uses a beam of electrons to illuminate the specimen
• Specimens must be fixed (dead) and usually stained/coated with a metal
• Higher resolution than light microscopy
• Types include SEM (scanning electron) and TEM (transmission electron)

SEM (Scanning Electron Microscopy)

• Allows 3D visualization of specimen surfaces, like insects or viruses

TEM (Transmission Electron Microscopy)

• Viewing very tiny structures, like organelles, requires thin sectioning and staining

Magnification

• Ratio of the image as seen under the microscope to its real-life size
• Microscope lenses responsible for magnification

Resolution

• Ability to distinguish two points in a specimen as separate
• Higher resolution with shorter wavelengths of light or electrons

Contrast

• How sharp the borders of the specimen appear
• Increasing contrast does not improve resolution.

Question 4 - Resolution

• Option C (Cut the specimen into smaller pieces) will enhance resolution. This improves clarity and visibility.

Question 5 - Microscopy

• Bright field microscopy best for observing a paramecium in pond water--because it can look at living specimens

Why are Cells So Small? Considerations

• Speed of diffusion
• Easier to replace damaged cells (damage of a smaller cell is less significant)
• Surface area to volume ratio (SA/Volume Ratio)

SA/Volume Ratio

• Nutrients, waste, and other materials enter/exit the cell via the plasma membrane
• Larger cells require more material to maintain metabolic needs
• Surface area and volume do not increase proportionally.

Components Common to All Cells

• Ribosomes
• Cytoplasm and cytosol
• DNA (and the central dogma)
• Plasma membrane
• Cytoskeleton

DNA and the Central Dogma

• All cells contain DNA
• Contains genetic instructions encoded in genes
• The central dogma is: DNA --> RNA --> protein

Prokaryotic vs Eukaryotic Cells- DNA and Central Dogma

• Prokaryotic: single circular chromosome in the nucleoid region
• Eukaryotic: Multiple linear chromosomes in the nucleus

Plasma Membrane

• Forms a semi-permeable barrier
• Composed of a phospholipid bilayer with embedded proteins
• Phospholipids are amphipathic
• Can be described using the fluid mosaic model.

Plasma Membrane - Prokaryotes vs Eukaryotes

• Similar structure in prokaryotes and eukaryotes
• Slight differences in membrane composition and regulation of fluidity

Ribosomes

• Machinery for protein synthesis.
• Formed from rRNA and proteins; large and small subunits.
• Read genetic instructions (mRNA) and produce proteins
• Translation (process of protein building)

Ribosomes - Prokaryotes vs Eukaryotes

• Prokaryotic ribosomes are smaller and freely suspended.
• Eukaryotic ribosomes are larger and sometimes attached to the endoplasmic reticulum.

Cytoplasm and Cytosol

• Cytoplasm is everything inside the plasma membrane.
• Cytosol is liquid part of the cytoplasm containing molecules (ions, organic molecules)
• Prokaryotic cells primarily consist of cytosol without many organelles
• Eukaryotic cells have cytoplasm divided into compartments by internal membranes

Cytoskeleton

• Network of proteins supporting, shaping, and moving cells
• Functions to support and protect the cell, assist in cellular movement/response to stimuli, anchor organelles, aid in cell division;

Cytoskeleton - Prokaryotes vs Eukaryotes

• Prokaryotic cytoskeleton is simpler.
• Eukaryotic cytoskeleton serves additional functions, including anchoring organelles and aiding in cell division.

Prokaryotic Cells (Overview)

• Two kingdoms: bacteria and archaea
• Unicellular organisms
• Capable of thriving in extreme conditions.
• Each cell performs all life functions without specialization

Prokaryotic Cells - Other Features

• Nucleoid region: Stores DNA.
• Circular Chromosome: Single circular DNA molecule
• Cell wall: Supporting structure
• Glycocalyx: Carbohydrate coating; capsule or slime layer
• Flagella: Used for movement
• Pili: Used for attaching to surfaces
• Plasmids: Extra pieces of self-replicating DNA

Eukaryotic Cells (Overview)

• Four kingdoms: Plants, Animals, Protista, Fungi
• Most are multicellular but some are unicellular

Eukaryotic Cells - Summary

• Nucleus: Stores DNA (in linear chromosomes)
• Organelles : Perform specific processes
• Cell wall (some eukaryotes)

Summary

• Life forms are made of macromolecules
• Microscopes enabled understanding cell types
• Cells are divided into prokaryotic and eukaryotic categories; eukaryotic cells are larger and have more elaborate structures. Some features are shared by both cells

Test your understanding of cell theory, the characteristics of prokaryotic and eukaryotic cells, and microscopy concepts. This quiz covers essential topics that are crucial for any biology student. Challenge yourself with questions regarding cellular structures and processes.