BSc Medical Sciences: Human Biology Module - Cell Structure and Functions PDF

BSc Medical Sciences: Human Biology Module Topic: Cell Structure and Functions  Learning Outcomes i. Describe the cell theory and its significance in biology. ii. Classify cells by their internal organisation and explain the differences between prokaryotic and e...

BSc Medical Sciences: Human Biology Module Topic: Cell Structure and Functions  Learning Outcomes i. Describe the cell theory and its significance in biology. ii. Classify cells by their internal organisation and explain the differences between prokaryotic and eukaryotic cells. iii. Relate cell structure to function, including the roles of different organelles. iv. Discuss the structure of the plasma membrane and its functions. v. Explain passive and active movements across the cell membrane, including diffusion, osmosis, and active transport. vi. Define osmosis and relate it to the actions of isotonic, hypotonic, and hypertonic solutions.  Introduction to Cell Theory Cell theory is one of the fundamental principles of biology, positing that all living organisms are made up of cells. It asserts that new cells are created from existing cells, ensuring a continuous line of genetic information passed through cell division. This theory has been instrumental in developments across medical and biological sciences. Historical Development of Cell Theory Developed in the mid-19th century, cell theory was formulated through the contributions of several scientists, notably Matthias Schleiden and Theodor Schwann. They proposed that plants and animals are made of cells, setting the foundation for modern cell biology and genetics.  Major Components of Cell Theory 1. All living organisms are composed of one or more cells. 2. The cell is the basic unit of life, responsible for all life's processes. 3. All cells arise from pre-existing, living cells, supporting the continuity of life.  Cell Classification Cells are primarily classified into two categories: prokaryotic, which lack a defined nucleus, and eukaryotic, which have a defined nucleus and complex organelles. This classification helps biologists understand and predict cellular behavior and interactions.  Prokaryotic vs. Eukaryotic Cells Prokaryotic cells are generally smaller and simpler, lacking a nucleus and most organelles. Eukaryotic cells are larger, with complex structures including a nucleus and various organelles, facilitating diverse functions within the cell. Eukaryotes vs Prokaryotes Cell Organelles and Their Functions Eukaryotic cells contain numerous organelles such as the nucleus, mitochondria, ribosomes, endoplasmic reticulum, and Golgi apparatus. Each plays a critical role in the cell's physiology, from genetic management to energy production and protein synthesis. Cellular evolution  Nucleus and Genetic Material The nucleus serves as the command center of the cell, housing genetic materials (DNA). It controls cellular activities by regulating gene expression, crucial for cell growth, division, and specialization.  Mitochondria and Energy Production Mitochondria are the cell's powerhouses, converting nutrients into energy (ATP) through cellular respiration. This energy is essential for powering various cellular processes and functions.  Endoplasmic Reticulum and Protein Synthesis The endoplasmic reticulum (ER) is subdivided into rough ER, which is involved in protein synthesis and folding, and smooth ER, which plays a role in lipid synthesis and detoxification processes within the cell.  Golgi Apparatus and Protein Sorting Following synthesis in the ER, proteins are transferred to the Golgi apparatus. Here, they are modified, sorted, and packaged into vesicles for distribution to their intended destinations within or outside the cell.  Lysosomes and Waste Processing Lysosomes are filled with enzymes that break down cellular waste, damaged organelles, and foreign particles. This process is vital for maintaining cellular health and preventing buildup of waste products.  Cytoskeleton and Cell Shape The cytoskeleton is a network of fibers that not only maintains the shape of the cell but also facilitates movement, both internally (transport of organelles) and externally (cell motility and muscle contraction).  Worksheet Classifying Cells and Labelling Organelles Worksheet Part 1: Classification of Cells 1. Classify the following cells as either Prokaryotic or Eukaryotic: i. A bacterial cell – ii. A human liver cell – iii. An amoeba – iv. A plant cell – 2. State three differences between prokaryotic and eukaryotic cells. 3. List two examples of prokaryotic organisms and two examples of eukaryotic organisms.  Plasma Membrane Structure The plasma membrane consists of a phospholipid bilayer with embedded proteins that manage the entry and exit of substances, allowing the cell to maintain homeostasis and communicate with its environment.  Functions of the Plasma Membrane Beyond its role as a barrier, the plasma membrane's embedded proteins aid in transport, signal transduction, and cellular adhesion, pivotal for cellular communication and coordination.  Transport Mechanisms Across Cell Membranes Cells employ various transport mechanisms to move substances across the plasma membrane. These include passive transport (diffusion, facilitated diffusion, osmosis) and active transport (pumps and vesicular transport).  Passive vs. Active Transport Passive transport relies on the concentration gradient and does not require energy, whereas active transport requires energy to move substances against their concentration gradient, critical for maintaining cellular concentrations of ions and molecules. Osmosis and Water Balance in Cells Osmosis is a special case of diffusion, where water moves across a semipermeable membrane from an area of lower solute concentration to higher concentration. This process is crucial for maintaining cell volume and pressure.  The Importance of Cell Theory in Modern Biology Understanding cell theory is essential for all areas of biology and medicine. It informs research into infectious diseases, genetic disorders, and therapies, linking microscopic cellular processes with large-scale biological functions.  Worksheet Worksheet: Labelling the Plasma Membrane Components Instructions: Study the diagram of the plasma membrane provided below. Label each of the following components in the diagram: i. Phospholipid bilayer ii. Hydrophobic tails iii. Hydrophilic heads iv. Integral proteins v. Peripheral proteins vi. Cholesterol molecules vii. Glycoproteins viii. Glycolipids ix. Protein channels Diagram:  Case studies Case Study Handout: Application of Cell Theory and Membrane Transport Case Study 1: Dehydration and Electrolyte Imbalance Scenario: A 25-year-old athlete collapses after running a marathon in hot, humid conditions. The paramedics suspect that the collapse was due to dehydration and electrolyte imbalance. Upon examination, they noticed that the athlete had been drinking only water during the race and had not consumed any electrolyte-replenishing fluids. Tasks: 1. Group Discussion: i. Discuss how cell theory explains the importance of maintaining proper electrolyte and water balance in cells. ii. Using the concept of osmosis, explain how drinking only water, without replacing lost electrolytes, could lead to cell dysfunction in this case. 2. Membrane Transport Mechanisms: i. How does osmosis play a role in the dehydration and electrolyte imbalance seen in this athlete? ii. Discuss the role of passive and active transport mechanisms in maintaining cellular homeostasis, particularly in muscle cells during intense physical activity. 3. Group Activity: i. Propose a solution to prevent dehydration and electrolyte imbalance during long-distance races. ii. Explain how this solution would help maintain proper osmotic balance and cell function. 4. Presentation: i. Present your findings and solution to the class, focusing on how cell structure and membrane transport principles apply to this real-life scenario.