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Questions and Answers
What is the smallest living unit of structure in all organisms?
What is the smallest living unit of structure in all organisms?
Which of the following statements about viruses is correct?
Which of the following statements about viruses is correct?
Which organisms are classified as unicellular?
Which organisms are classified as unicellular?
What is the size range of the largest viruses compared to bacteria?
What is the size range of the largest viruses compared to bacteria?
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What does the term 'Cytology' refer to?
What does the term 'Cytology' refer to?
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What is cytology primarily concerned with?
What is cytology primarily concerned with?
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Which of the following correctly describes prokaryotic cells?
Which of the following correctly describes prokaryotic cells?
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What did Robert Hooke contribute to the field of cytology?
What did Robert Hooke contribute to the field of cytology?
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What is a key feature of plant cells not found in animal cells?
What is a key feature of plant cells not found in animal cells?
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Who proposed the cell theory for animals in collaboration with M. Schleiden?
Who proposed the cell theory for animals in collaboration with M. Schleiden?
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Study Notes
Cytology and Genetic Course
- Cytology, also known as cell biology, studies cells.
- It's crucial for researchers in vaccine and medicine development.
- The cell is the basic unit of life.
- Plant cells have cell walls and plastids, unlike animal cells which lack these components.
- Prokaryotic cells lack membrane-bound organelles, unlike eukaryotic cells.
- Plants are unique eukaryotes capable of producing their own food (autotrophic).
Historical Review
- Cytology emerged as a distinct biological field by the late 19th century.
- Before the 19th century, figures like Aristotle and Paracelsus considered few fundamental components in plants and animals
- Leonardo da Vinci (1485) used lenses to view small objects.
- Jan Swammerdam (1658) described cells (blood cells).
Further Development of Cytology
- Marable (1808): Found plants have membranous cellular tissues.
- Turpin (1826): Observed cell division.
- Robert Brown (1826, 1831): Discovered and described the nucleus as a central part of plant cells.
- Felix Dujardin (1835): Described protoplasm in protozoa.
- Schleiden (1838) and Schwann (1839): Established basic cell theory for plants and animals, respectively.
- Rudolf Virchow (1858): Stated all cells arise from preexisting cells.
Additional Key Developments
- Robert Hooke (1665-1703): Studied cork and coined the term "cells."
- Antonie van Leeuwenhoek (1632-1723): Discovered protozoa, red blood cells, etc.
- Fontana (1781): Described the nucleolus.
- 19th century: Considered the classical era for cytological investigations.
- Purkinje (1840): Named the cell contents as protoplasm.
- Haecked (1866): Named plastids.
- Strasburger (1875): Described chromosomes.
Principles of Cell Theory
- All living things are made of cells.
- Cells are the smallest living units of structure and function in organisms.
- All cells arise from preexisting cells.
- Most cells are microscopic.
Cell Surface Area
- Larger surface area to volume ratio is advantageous for cells.
- A smaller cell can more effectively exchange substances with its environment.
Viruses Versus Cells
- Viruses are transitional between living and nonliving things.
- Viruses infect both prokaryotic and eukaryotic cells.
- Viruses are metabolically inert but active in hosts.
- Viruses are simpler than cells in structure and life cycle.
- Virus size is smaller than bacteria.
Classification of Organisms
- Cellular organisms (except some plants like rhizopus and vaucheria) have cellular organization.
- They may be unicellular or multicellular.
- Prokaryotic cells lack a true nucleus.
- Examples include certain bacteria, blue-green algae and PPLO.
- PPLO are bacteria-like organisms.
Prokaryotic Cells (Bacteria)
- Bacteria are microscopic, unicellular, and lack chlorophyll.
- They can be saprophytic or parasitic.
- Average size is 1.25 μm.
- Smallest bacteria are 0.15-0.30 μm in length; largest up to 13-15 μm.
- Forms include coccus, bacillus, and spirillum.
Cytology Key Terms
- Karyokinesis: Nucleus division
- Cytokinesis: Cytoplasm division
- Diploid: Two sets of chromosomes (somatic cells).
- Haploid: One set of chromosomes (gametes).
- Crossing over: Genetic material exchange during meiosis.
- Homologous chromosome: Pair of chromosomes with same size and identical gene sequences.
- Phenotype: Observable characteristics of organism.
- Genotype: Genetic makeup of organism.
- Tonoplast: Membrane surrounding the vacuole.
- Unit membrane: Basic structure of cell membrane.
Plant and Animal Cell Differences
| Feature | Plant Cell | Animal Cell |
|---|---|---|
| Cell wall | Present | Absent |
| Vacuoles | Present | Absent |
| Chloroplasts | Present | Absent |
| Centrosomes | Absent | Present |
Eukaryotic vs. Prokaryotic Cells
| Feature | Eukaryotic Cell | Prokaryotic Cell |
|---|---|---|
| Nucleus | Present | Absent |
| Chromosomes | More than one | One, not true chromosome; plasmids |
| Membrane-bound Nucleus | Present | Absent |
| Lysosomes and peroxisomes | Present | Absent |
Eukaryotic Cell Organelles (Presence/Absence, Size)
| Organelle | Eukaryotic Cell | Notes |
|---|---|---|
| Mitochondria | Present | |
| Ribosomes | Present | Larger |
| Vesicles | Present | |
| Golgi apparatus | Present | |
| Chloroplasts | Present (plants) | Absent, chlorophyll scattered in cytoplasm |
| Vacuoles | Present | |
| Cell size | 10-100 μm | 1-10 μm |
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