1.5: Cell Biology

Introduction

The basic subunit of all living things is the cell.

Types of cells are divided into two categories - prokaryotic cells and eukaryotic cells.

Prokaryotic cells are simple cells found in Bacteria and Archaea.

Eukaryotic cells are complex cells found in Protists, Plants, Animals, and, though greatly modified, in Fungi.

Activity A: Prokaryotic Cells

Figure 1: Structure of a Prokaryotic Cell (OpenStax.org)

• Prokaryotes are single-celled organisms.
• They have no membrane-bound organelles.
• Usually there is a single piece of circular, double-stranded DNA in the region called a Nulceoid.
• The cell wall is protective and gives the cell its shape.
• Many have a flagellum for locomotion.
• Pili enable the organism to attach to surfaces.
• Some have a capsule that makes pathogens more resistant to our immune responses.

Figure 2: Scanning electron micrographs showing the shapes of Prokaryotic Cells - Coccus, Bacillus, Spirillum (https://openlab.citytech.cuny.edu/bio-oer)

1. Obtain slides of cocci, bacillus, and spirillum bacteria. Draw them below and list an example of each.

   Cocci Bacteria

   Example ________________________________________________

   Bacillus Bacteria

   Example ________________________________________________

   Spirillum bacteria

   Example ________________________________________________

   
   
   
2. Look at a slide of Gram-negative and Gram-positive bacteria and draw what you see. Explain the difference between gram-negative and gram-positive bacteria.
   
   Gram-negative and Gram-positive bacteria

   What is the difference between the two types in terms of human disease? ___________________________________________________

Activity B: Eukaryotic Cells

• Eukaryotic cells are those found in plants, animals, protists, and (though modified) in fungi.
• Eukaryotic cells can be found in both autotrophs, which carry out photosynthesis to produce their own energy, and heterotrophs, which depend upon other cells for energy.
• Eukaryotic cells have many internal membrane-bound organelles, such as mitochondria and chloroplasts, a nucleus surrounded by a membrane, and rod-shaped chromosomes.
• Recall that in the Microscope Lab you studied a plant cell (Elodea) and animal cells (squamous cells)
• Now we are going to look at more detail as revealed by the transmission electron microscope and scanning electron microscope.

Figure 3: Animal Cell showing details revealed by the electron microscope. (https://oercommons.org/authoring/566...ty-textbook-re)

Figure 4: Plant Cell with details revealed by the electron microscope. (https://oercommons.org/authoring/566...ty-textbook-re)

Look at Figures 3 and 4 and answer these questions:

1. List 3 components that plant cells have that animal cells do not have.
   ______________________ ______________________ ______________________
2. List 2 components that animal cells have that plant cells do not have.
   ______________________ ______________________
3. What are the functions of the following structures?
   1. Rough endoplasmic reticulum
      _______________________________________________________
   2. Smooth endoplasmic reticulum
      _______________________________________________________
   3. Golgi apparatus
      _______________________________________________________
   4. Mitochondria
      _______________________________________________________
   5. Chloroplast
      _______________________________________________________
   6. Lysosome
      _______________________________________________________
   7. Cell wall
      _______________________________________________________
   8. Central vacuole
      _______________________________________________________
   9. Ribosome
      _______________________________________________________
   10. Plasma membrane
       _______________________________________________________
   11. Centrosome
       _______________________________________________________
   12. Nucleus
       _______________________________________________________
   13. Nucleolus
       _______________________________________________________

Activity C: Protista

• Protists are a diverse group of mostly single-celled eukaryotes.
• Protists are ideal examples of eukaryotic cells. Since they are single-celled, they contain all cellular components necessary for life, unlike multicellular organisms such as plants and animals, in which cells may be specialized and may not have all cellular components.
• Some are animal-like heterotrophs that move and eat other organisms. Examples include Amoeba and Paramecium
• Others are plant-like. Examples include Euglena and diatoms. They have chloroplasts that are used in photosynthesis.
• Most Protists have structures for locomotion. Common methods are cilia, flagella, and pseudopods. Humans have ciliated cells in the trachea that carry pathogens and other particles away from the lungs. Our white blood cells have pseudopodia.
• Protists live in freshwater, seawater, soil, and some are parasites.

Figure 5: Drawings of 3 common protists: Paramecium, Amoeba, Euglena. (https://oercommons.org/authoring/566...ty-textbook-re)

(a) Paramecium lives in freshwater. It is a predator of bacteria and other small particles that it sweeps into an oral groove (mouth), It moves with hair-like structures called cilia. A macronucleus controls everyday cell activities. Food vacuoles contain ingested food. Contractile vacuoles pump excess water out of the cell.

(b) Amoeba is also a freshwater predator. It also lives in soil and other moist environments. It moves with pseudopods (false feet). It engulfs food such as bacteria and small protists by surrounding them with pseudopodia in a process called phagocytosis. You can see the cell membrane, cytoplasm, nucleus, pseudopodia, food vacuoles, contractile vacuole.

(c) Euglena lives in freshwater habitats. It has characteristics of both animals and plants. moves with a long whip-like flagellum. It can carry out photosynthesis using chloroplasts like a plant. When light is unavailable, it can ingest nutrients like an animal. It has an eye-spot that detects light, helping it move toward brighter areas.

Figure 6: Process of Phagocytosis. (https://oercommons.org/authoring/566...ty-textbook-re)

The process of phagocytosis involves surrounding the food particle with pseudopodia, engulfing it in a food vacuole, digesting it with lysosomes, and then getting rid of the wastes by exocytosis. In humans, 4 of the 5 types of leukocytes (white blood cells) carry out phagocytosis of pathogens such as viruses and bacteria, as well as other agents.

Make wet mounts of each of these 3 protists. There may be others available.

If there are no live cultures, you may work from prepared slides.

After you have prepared your wet mount, begin with the scanning 4x objective, which magnifies 40x.

After centering and focusing on a specimen, turn to the low-power 10x objective, which magnifies 100x.

Center and focus again.

Finally, turn to the high-power 40x objective, which magnifies 400x. Make your drawings at high-power magnification.

If your specimens move too fast for you to study, you can add a drop of methylcellulose (ProtoSlo). It will slow the movement without harming the organism.

Label as many structures as you can see.

Paramecium Amoeba

Euglena __________

Fill in:

Table 1. Comparison of Protists

Protist	Locomotion	Nutrition	Method of Feeding	Similar Cells in Humans
Paramecium
Amoeba
Euglena

Licensing and Attributions

• CC Licensed Content, Original
• Biology Labs. Authored by: Joe Frantz. Provided by Oxnard College. Located at http://www.oxnardcollege.edu. License CC BY: Attribution
• Biology Open Educational Resources, authored and curated by Jeremy Seto, Department of Biological Sciences – New York City College of Technology. https://openlab.citytech.cuny.edu/bio-oer. License CC BY-NC-SA
• Brammer, Amanda. "Concepts of Biology by Rice University Textbook Resources for Biology II." OER Commons. Institute for the Study of Knowledge Management in Education, 09 Aug. 2019. Web. 25 Jun. 2026. https://oercommons.org/authoring/566...ty-textbook-re

This document, "Cell Biology," provides an introduction to the fundamental unit of life, the cell, and then delves into the characteristics and activities related to prokaryotic and eukaryotic cells, including a specific focus on protists.

Key Sections and Activities:

• Introduction to Cells:
  • Defines the cell as the basic subunit of all living things.
  • Categorizes cells into two main types: prokaryotic and eukaryotic.
  • Briefly describes prokaryotic cells as simple cells found in Bacteria and Archaea, and eukaryotic cells as complex cells found in Protists, Plants, Animals, and Fungi.
• Activity A: Prokaryotic Cells
  • Describes prokaryotes as single-celled organisms lacking membrane-bound organelles.
  • Highlights key structures such as a single circular DNA in the nucleoid, a protective cell wall, flagellum for locomotion, pili for attachment, and a capsule in some pathogens.
  • Includes an activity to draw and provide examples of different prokaryotic shapes (coccus, bacillus, spirillum).
  • Asks for an explanation of the difference between Gram-negative and Gram-positive bacteria and their implications for human disease.
• Activity B: Eukaryotic Cells
  • Reiterates that eukaryotic cells are found in plants, animals, protists, and fungi.
  • Explains that eukaryotic cells can be autotrophs or heterotrophs.
  • Details the presence of internal membrane-bound organelles (e.g., mitochondria, chloroplasts), a membrane-bound nucleus, and rod-shaped chromosomes.
  • Refers to previous microscope lab experience with plant and animal cells.
  • Presents figures of animal and plant cells and asks for a comparison of their components.
  • Requires listing the functions of various eukaryotic organelles (e.g., rough ER, smooth ER, Golgi apparatus, mitochondria, chloroplast, lysosome, cell wall, central vacuole, ribosome, plasma membrane, centrosome, nucleus, nucleolus).
• Activity C: Protista
  • Introduces protists as a diverse group of mostly single-celled eukaryotes, ideal for studying cellular components.
  • Classifies protists as animal-like heterotrophs (e.g., Amoeba, Paramecium) or plant-like autotrophs (e.g., Euglena, diatoms).
  • Discusses common methods of locomotion (cilia, flagella, pseudopods) and their human counterparts.
  • Describes the habitats of protists.
  • Provides detailed descriptions of Paramecium, Amoeba, and Euglena, including their structures and functions.
  • Explains the process of phagocytosis using Amoeba as an example and relates it to human immune responses.
  • Outlines a lab procedure for observing protists under a microscope.
  • Includes sections for drawing and labeling the observed protists.
  • Concludes with a table for comparing protists based on locomotion, nutrition, method of feeding, and similar cells in humans.