Lecture 1: Intro to Cellular and Molecular Biology

Introduction

Cell and molecular biology is a foundational discipline in the life sciences that examines the structure and function of cells at both the cellular and molecular levels. Understanding this topic is crucial for numerous fields, including genetics, biochemistry, and biotechnology. This chapter will explore essential vocabulary, key concepts, and the significance of cellular structures and functions. Notably, terms such as plasma membrane, cytoplasm, nucleus, and cell theory will be emphasized as they lay the groundwork for comprehending the complexity of life.

The study of cells reveals the basic unit of life, encapsulated in the cell theory, which states that (1) all organisms are comprised of cells, and (2) cells are the smallest units of living organisms. This understanding has evolved significantly since the 17th century, with contributions from notable figures such as Robert Hooke, who first identified cells in cork, and later researchers who expanded upon these ideas.

Cellular Structures and Their Functions

Plasma Membrane

- Acts as a barrier regulating the movement of substances in and out of the cell.

- Composed of a lipid bilayer that is essential for maintaining the integrity of the cell.

Cytoplasm (Cytosol)

- The semifluid matrix surrounding organelles within the cell, containing the cytoskeleton, which supports and shapes the cell.

Nucleus

- A double membrane organelle housing DNA, specifically 46 chromosomes in human cells.

- Contains the nucleolus, a dense structure responsible for the synthesis of ribosomal RNA (rRNA).

Mitochondria

- The powerhouse of the cell, performing cellular respiration and producing ATP (adenosine triphosphate) for energy.

- Features cristae, which increase surface area for enzyme activity.

Chloroplasts

- Unique to plant cells, these organelles are the sites of photosynthesis and contain thylakoid membranes that convert light energy into chemical energy.

Endoplasmic Reticulum (ER) and Golgi Apparatus

- The Endoplasmic Reticulum synthesizes lipids and proteins while the Golgi Apparatus sorts, modifies, and packages cellular materials for transport.

Comparison of Plant and Animal Cells

- Animal cells lack chloroplasts, large central vacuoles, and plasmodesmata.

- Plant cells do not possess lysosomes, centrioles, or flagella, which are present in animal cells.

Cytoskeleton

The cytoskeleton is a complex network within the cytoplasm, consisting of three main types of filaments:

- Microfilaments: Involved in cell movement and shape.

- Microtubules: Provide structural support and facilitate intracellular transport.

- Intermediate filaments: Contribute to the mechanical strength of the cell.

Properties that Define Life

To fully grasp cell biology, it is essential to understand the properties that define life, which include:

1. Order - Organized structure of cells.

2. Reproduction - Ability to produce offspring.

3. Growth and Development - Changes occurring over a lifetime.

4. Energy Harvest from Environment - Metabolic processes for energy acquisition.

5. Homeostasis - Maintaining stable internal conditions.

6. Response to Environment - Reacting to stimuli.

7. Evolution - Changes in populations over time.

Prokaryotes vs. Eukaryotes

- Prokaryotes:

- Lack a nucleus and membrane-bound organelles.

- Generally smaller, ranging from 1-10 micrometers in size.

- Eukaryotes:

- Can be unicellular or multicellular with internal compartments.

- Size ranges from 10-100 micrometers.

- The distinction between these two cell types is fundamental for understanding biological processes.

Model Organisms

Model organisms are critical for research due to their genetic, biological, and behavioral similarities to humans. Examples include:

1. Yeast

2. Roundworm

3. Planarian

4. Mouse

5. Alga

6. Fruit Fly

7. Zebrafish

8. Plants

These organisms share homologous genes with humans, making them invaluable for studying development and disease.

Historical Context of Cell Theory

The development of cell theory evolved through key milestones, including:

- 1838-39: Schleiden and Schwann proposed that cells are the structural unit of life, refuting spontaneous generation.

- 1855: Virchow asserted that cells arise from pre-existing cells.

- 1865: Mendel's work on heredity established the concept of genes.

- 1880-90: Recognition that chromosomes carry genetic information.

- 1953: The elucidation of DNA structure by Watson and Crick.

- 2000: Completion of the human genome sequencing project, marking a significant advancement in molecular biology.

Conclusion

The exploration of cell and molecular biology reveals the intricate structures and functions that define life. Key takeaways include the importance of understanding cellular components such as the plasma membrane, nucleus, and organelles, as well as the essential properties that define living organisms. The historical context of cell theory illustrates the evolution of scientific thought surrounding cells. In summary, the knowledge gleaned from this field not only enhances our understanding of biology but also has profound implications in medicine, genetics, and biotechnology, paving the way for future discoveries and innovations.