HBS109 Cell Biology Part 1_default

Introduction to Physiology

• Physiology is the study of how biological systems function, with a fundamental focus on the cell as the basic unit of life.

• Cells are the building blocks of all tissues and organs in the body.

• Understanding physiology involves recognizing the various functions of cells and how they can work individually or in groups.

• The upcoming lectures will cover several organ systems in detail.

Types of Cells

• There are two main types of cells in the human body:

  • Sex cells (germ cells): Include sperm cells and oocytes (egg cells).

  • Somatic cells: All other body cells, which will be the focus of these lectures.

Cell Structure and Components

• Cells function as individual units akin to small organisms and contain various components called organelles that enable them to perform specific functions.

• The human body is estimated to have around 37 trillion cells.

Cell Membrane

• The cell membrane, also called the plasma membrane, serves several critical functions:

  • Physical isolation: Separates the intracellular environment from the extracellular environment.

  • Regulation of exchanges: Monitors and controls what enters and exits the cell, acting like a border control.

  • Sensory functions: Detects environmental changes such as pH or chemical composition of extracellular fluid.

  • Structural support: Maintains cell shape and tissue integrity.

Cytoplasm

• The cytoplasm consists of everything between the cell membrane and the nucleus, including:

  • Cytosol: The liquid component containing dissolved nutrients, proteins, ions, and wastes. It varies in viscosity among different cells (thin and watery to thick and gel-like).

  • Organelles: Specialized structures within the cytosol performing various functions essential for cell survival.

Differences between Cytosol and Extracellular Fluid

• The cytosol has a higher concentration of potassium ions compared to the extracellular fluid, which has a higher sodium ion concentration. This is significant for functions like the sodium-potassium pump that maintains cellular homeostasis.

Organelles

• Organelles can be classified into two types:

  • Membrane-bound organelles (e.g., mitochondria, lysosomes).

  • Non-membrane-bound organelles (e.g., microfilaments, microtubules, and intermediate filaments).

Cytoskeleton

• The cytoskeleton gives the cell its shape and strength, consisting of:

  • Microtubules: Composed of tubulin, provide rigidity, assist in cell division, and form a transport system for organelles.

  • Microfilaments: Comprised of actin, mainly involved in muscle contractions and shape changes of the cell. They interact with myosin for movement.

  • Intermediate filaments: Thicker than microfilaments and provide structural stability and support to the cell and its organelles.

Nucleus

• Most cells contain one nucleus, but skeletal muscle cells have multiple nuclei and red blood cells have none.

• The nucleus has its own nuclear envelope with pores for chemical exchange with the cytosol, containing nucleoplasm.

• DNA, organized into chromosomes, resides within the nucleus:

  • Somatic cells contain 23 pairs of chromosomes, one from each parent.

  • DNA carries the genetic code essential for cellular function and inheritance.

• If all DNA from all cells were stretched out, it would form a strand approximately twice the diameter of the solar system.

Organelles and Their Functions in Physiology

1. Mitochondria

   • Often referred to as the "powerhouses" of the cell, mitochondria are responsible for producing adenosine triphosphate (ATP) through cellular respiration.

   • They convert energy from nutrients into a usable form, enabling the cell to perform various functions.

2. Lysosomes

   • Lysosomes contain digestive enzymes that break down waste materials and cellular debris.

   • They are involved in autophagy (the process of recycling cellular components) and help maintain cellular health by removing damaged components.

3. Endoplasmic Reticulum (ER)

   • The ER is divided into rough ER (with ribosomes) and smooth ER (without ribosomes).

   • Rough ER is involved in protein synthesis and processing, while smooth ER is involved in lipid synthesis and detoxification processes.

4. Golgi Apparatus

   • The Golgi apparatus is responsible for modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles.

   • It plays a crucial role in the post-translational modification of proteins.

5. Ribosomes

   • Ribosomes are the sites of protein synthesis, translating mRNA into polypeptides.

   • They can be found floating freely in the cytosol or attached to the rough ER.

6. Cytoskeleton

   • Composed of microtubules, microfilaments, and intermediate filaments, the cytoskeleton provides structural support and shape to the cell.

   • It is also involved in intracellular transport and cell division.

7. Centrioles

   • Centrioles are involved in organizing microtubules during cell division, facilitating the proper separation of chromosomes.

   • They help in forming the spindle apparatus necessary for mitosis and meiosis.

8. Peroxisomes

   • Peroxisomes contain enzymes that produce and break down hydrogen peroxide, aiding in the detoxification of harmful substances and the metabolism of fatty acids.

9. Vesicles

   • Vesicles are small membrane-bound sacs that transport materials within the cell.

   • They are involved in processes such as secretion, endocytosis, and the storage of substances.

Summary

Each organelle plays a vital role in maintaining cellular function and overall homeostasis within the organism. By understanding their individual functions, we can better comprehend the complexity and efficiency of cellular operations in physiology.

Anatomy and Physiology of Cell Organelles

1. Mitochondria

   • Anatomy: Double-membraned organelle; outer membrane is smooth, while the inner membrane is folded into cristae, creating compartments.

   • Physiology: Known as the "powerhouses" of the cell, they produce adenosine triphosphate (ATP) through cellular respiration, converting energy from nutrients into a usable form for cellular functions.

2. Lysosomes

   • Anatomy: Membrane-bound vesicles containing digestive enzymes.

   • Physiology: Breaks down waste materials and cellular debris; involved in autophagy, recycling damaged components to maintain cellular health.

3. Endoplasmic Reticulum (ER)

   • Anatomy: Network of membranous tubules and sacs; divided into rough ER (with ribosomes) and smooth ER (without ribosomes).

   • Physiology: Rough ER is crucial for protein synthesis and processing, while smooth ER is involved in lipid synthesis and detoxification processes.

4. Golgi Apparatus

   • Anatomy: Stacked, flattened membranous sacs (cisternae).

   • Physiology: Modifies, sorts, and packages proteins and lipids for transport or secretion, playing a key role in post-translational modification of proteins.

5. Ribosomes

   • Anatomy: Composed of two subunits (large and small); can be free in the cytosol or bound to rough ER.

   • Physiology: Sites of protein synthesis that translate messenger RNA (mRNA) into polypeptides.

6. Cytoskeleton

   • Anatomy: Composed of microtubules, microfilaments, and intermediate filaments, providing structural integrity.

   • Physiology: Provides shape, supports the cell, and is involved in intracellular transport and cell division.

7. Centrioles

   • Anatomy: Cylindrical structures made of microtubules, typically found in pairs.

   • Physiology: Organize microtubules during cell division; form spindle apparatus necessary for mitosis and meiosis.

8. Peroxisomes

   • Anatomy: Membrane-bound organelles containing enzymes.

   • Physiology: Aid in the detoxification of harmful substances and the metabolism of fatty acids by producing and breaking down hydrogen peroxide.

9. Vesicles

   • Anatomy: Small, membrane-bound sacs.

   • Physiology: Transport materials within the cell; involved in secretion, endocytosis, and storage of substances.

Anatomy and Physiology of Cell Organelles

1. Mitochondria

   • Anatomy: Double-membraned organelle; outer membrane is smooth, while the inner membrane is folded into cristae, creating compartments.

   • Physiology: Known as the "powerhouses" of the cell, they produce adenosine triphosphate (ATP) through cellular respiration, converting energy from nutrients into a usable form for cellular functions.

2. Lysosomes

   • Anatomy: Membrane-bound vesicles containing digestive enzymes.

   • Physiology: Breaks down waste materials and cellular debris; involved in autophagy, recycling damaged components to maintain cellular health.

3. Endoplasmic Reticulum (ER)

   • Anatomy: Network of membranous tubules and sacs; divided into rough ER (with ribosomes) and smooth ER (without ribosomes).

   • Physiology: Rough ER is crucial for protein synthesis and processing, while smooth ER is involved in lipid synthesis and detoxification processes.

4. Golgi Apparatus

   • Anatomy: Stacked, flattened membranous sacs (cisternae).

   • Physiology: Modifies, sorts, and packages proteins and lipids for transport or secretion, playing a key role in post-translational modification of proteins.

5. Ribosomes

   • Anatomy: Composed of two subunits (large and small); can be free in the cytosol or bound to rough ER.

   • Physiology: Sites of protein synthesis that translate messenger RNA (mRNA) into polypeptides.

6. Cytoskeleton

   • Anatomy: Composed of microtubules, microfilaments, and intermediate filaments, providing structural integrity.

   • Physiology: Provides shape, supports the cell, and is involved in intracellular transport and cell division.

7. Centrioles

   • Anatomy: Cylindrical structures made of microtubules, typically found in pairs.

   • Physiology: Organize microtubules during cell division; form spindle apparatus necessary for mitosis and meiosis.

8. Peroxisomes

   • Anatomy: Membrane-bound organelles containing enzymes.

   • Physiology: Aid in the detoxification of harmful substances and the metabolism of fatty acids by producing and breaking down hydrogen peroxide.

9. Vesicles

   • Anatomy: Small, membrane-bound sacs.

   • Physiology: Transport materials within the cell; involved in secretion, endocytosis, and storage of substances.

Anatomy of Cell Organelles

1. Mitochondria

   • Structure: Double-membraned organelle; outer membrane is smooth, while the inner membrane is folded into cristae, creating compartments.

2. Lysosomes

   • Structure: Membrane-bound vesicles containing digestive enzymes.

3. Endoplasmic Reticulum (ER)

   • Structure: Network of membranous tubules and sacs; divided into rough ER (with ribosomes) and smooth ER (without ribosomes).

4. Golgi Apparatus

   • Structure: Stacked, flattened membranous sacs (cisternae).

5. Ribosomes

   • Structure: Composed of two subunits (large and small); can be free in the cytosol or bound to rough ER.

6. Cytoskeleton

   • Structure: Composed of microtubules, microfilaments, and intermediate filaments, providing structural integrity.

7. Centrioles

   • Structure: Cylindrical structures made of microtubules, typically found in pairs.

8. Peroxisomes

   • Structure: Membrane-bound organelles containing enzymes.

9. Vesicles

   • Structure: Small, membrane-bound sacs.