Outline of Chapter 1: Introduction to the Study of Cell & Molecular Biology

History of Cell Biology

 Microscopy Development: Spectacles in the 13th century, compound microscopes by the 16th
century.
 Discovery of Cells: By mid1600s, scientists discovered cells using handmade microscopes.

1. Development of Cell Theory

 Schleiden and Schwann:
 1838: Schleiden concluded all plant tissues are made of cells.
 1839: Schwann realized animal life is cellular, leading to Cell Theory:
 All organisms are composed of one or more cells.
 The cell is the structural unit of life.
 Virchow's Contribution 1855): Added that cells arise only from preexisting cells.
 Modern Addition: Cells contain genetic information (DNA) passed to the next cell generation

1.2 Basic Properties of Cells

1. Life
 Cultured Cells: First human cell culture by Gey (1951).
 HeLa cells are cultured tumor cells isolated from a cancer patient (Henrietta Lacks)
1) NO CONSENT FROM PATIENT OR FAMILY
2) Used even today - for COVID
 Death: Integral property of life.
 Cells are Highly Complex & Organized
 Order and Consistency: Cells have specific structures and functions.
 Cells from different species share similar structure, composition, and metabolic features
 Example: Intestinal epithelial cells with microvilli and mitochondria.
 Genetic Program & Means to use it
 DNA as Blueprint: Genes provide instructions for cellular functions.
1) Direction for running cell activities
2) program for cells to reproduce
 Haploid or diploid
 Mutations and Evolution: Genetic changes lead to diversity and evolution.
 Reproduction
 Mitosis and Meiosis: Cells reproduce by division.
1) Daughter cells or gametes respectively
 Energy Acquisition and Usage
 Photosynthesis provides fuel for all living organisms.
 Photosynthesis and Respiration: Conversion of light energy to chemical energy.
1) Photosynthesis: 6 CO₂ + 6 H₂O + light energy → C₆H₁₂O₆ + 6 O₂
 Animals use energy from glucose
2) Respiration: C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + energy (ATP)
 ATP: Central molecule for energy storage and usage.
 Chemical Reactions
 Cells = mini chemical plants
 Enzymes: Catalysts for cellular reactions.
 Metabolism: Sum total of chemical reactions in a cell.
 Mechanical Activities
 Motor Proteins: Facilitate movement and transport within cells.
  Response to Stimuli
 Receptors: Detect environmental changes and trigger responses.
1) React to hormones, growth factors and extracellular material
 Self-Regulation
 Feedback Mechanisms: Maintain cellular stability.
1) EX: sea urchin experiment formed complete, smaller embryo polyps
 Information for product design resides in the nucleic acids, and the construction workers are
primarily proteins.
 Evolution
 Common Ancestry: All living organisms evolved from a single cell.
 Last Universal Common Ancestor ~3 billion years ago
 Cells share many features, including a common genetic code, a plasma membrane, and
ribosomes.

1.3 Characteristics That Distinguish Prokaryotic and Eukaryotic Cells

 Basic Differences
 Prokaryotes: Bacteria and cyanobacteria, no membrane bound organelles.
 Eukaryotes: Protists, fungi, plants, animals with membrane bound organelles.

 Shared Properties
 Genetic Information: Both use DNA and share metabolic pathways.

 Distinctive Features
 Nucleus: Eukaryotes have a membrane bound nucleus, prokaryotes have a nucleoid.
 Organelles: Eukaryotes have mitochondria, ER, Golgi complex, etc.
 Reproduction: Prokaryotes use binary fission, eukaryotes use mitosis and meiosis.
1.4 Types of Prokaryotic Cells

1. Domains of Prokaryotes
 Archaea: Extremophiles like methanogens, halophiles, acidophiles, and thermophiles.
 Bacteria: Eubacteria, including mycoplasma and cyanobacteria.
1.5 Types of Eukaryotic Cells

1. Complexity
 Unicellular Protists: Perform all life functions within a single cell.
 Multicellular Organisms: Division of labor among specialized cells.
 Differentiation – the formation of specialized cells


2. Model Organisms
 Commonly Studied: E. coli, yeast, Arabidopsis (thale cress), C. elegans (nematode), Drosophila
(fruit fly), mouse.

1.7 The Sizes of Cells and Their Components

1. Units of Measure
 Micrometers (µm), Nanometers (nm), Ångstroms (Å)

2. Examples of Sizes
 Proteins and Organelles: Specific dimensions of cellular components.

3. Cell Size Limitations

 Surface Area/Volume Ratio: Constraints on cell size due to diffusion limitations.
 Distance over which substances can efficiently travel through the cytoplasm via diffusion.
 Volume of cytoplasm that can be supported by the genes in the nucleus.

1.8 Viruses and Viroids

1. Viruses
 Characteristics: Intracellular parasites, not considered alive outside host cells.
 Virion: virus particle outside of host cell (capsid + membrane envelope)
 Bacteriophage: viruses that infect bacteria
 Infection Types:
 Lytic - infects host, lyses and releases reproduced viruses
 Integration - Provirus formation into host cell DNA

2. Viroids
 Characteristics: Infectious RNA molecules without a protein coat (naked)
 Causes disease by interfering with gene expression of host cells
 Sample Quiz: Introduction to Cell & Molecular Biology
Chapter 1: Introduction to the Study of Cell & Molecular Biology

Multiple Choice Questions:

1. Which of the following is NOT a tenet of the Cell Theory as proposed by Schleiden and
Schwann?
o A. All organisms are composed of one or more cells.
o B. The cell is the structural unit of life.
o C. Cells can arise only by division from a preexisting cell.
o D. Cells contain genetic information passed to the next generation.
2. What is the primary difference between prokaryotic and eukaryotic cells?
o A. Prokaryotic cells have a membrane-bound nucleus.
o B. Eukaryotic cells do not have membrane-bound organelles.
o C. Prokaryotic cells lack a true nucleus.
o D. Eukaryotic cells reproduce through binary fission.
3. Which of the following structures is found in both prokaryotic and eukaryotic cells?
o A. Nucleus
o B. Ribosomes
o C. Endoplasmic Reticulum
o D. Mitochondria
4. What is the primary molecule used by cells to store and transfer energy?
o A. Glucose
o B. ATP
o C. DNA
o D. RNA

True or False:
6. True or False: The HeLa cell line, derived from Henrietta Lacks, was the first human cell
culture.
7. True or False: All living organisms evolved from a single common ancestral cell, often referred
to as the last universal common ancestor (LUCA).
8. True or False: Viruses are considered living organisms because they can reproduce and carry
out metabolic activities on their own.
 CANNOT carry out metabolic activities (virions)
9. True or False: Eukaryotic cells have a more complex cytoskeleton compared to prokaryotic
cells.
10. True or False: Prokaryotic cells can only reproduce asexually through binary fission and have
no means of exchanging genetic material.
 PILUS

Short Answer Questions:

11. Identify two fundamental differences between prokaryotic and eukaryotic cells.
 Prokaryotic cells lack a membrane-bound nucleus, while eukaryotic cells have a defined nucleus
enclosed by a nuclear envelope.
 Eukaryotic cells contain various membrane-bound organelles, such as mitochondria and the
endoplasmic reticulum, whereas prokaryotic cells do not have such organelles.
12. Discuss the role of ATP in cellular activities.
 ATP (adenosine triphosphate) acts as the primary energy currency of the cell.
  It stores energy in its high-energy phosphate bonds and releases it to fuel various cellular
processes, including muscle contraction, chemical synthesis, and transport across cell
membranes.
13. What are viroids, and how do they differ from viruses?
 Viroids are small, infectious RNA molecules that cause disease in plants by interfering with gene
expression.
 Unlike viruses, viroids do not encode proteins and lack a protein coat (capsid).
 They rely entirely on host cellular machinery for replication and do not infect animal or bacterial
cells.