Evolution of the Cell PDF

Derek V. Coronacion WVSU - BS Biology 3D Relation to Life’s Origin The harsh conditions of early Earth were crucial for Evolution of the Cell...

Derek V. Coronacion WVSU - BS Biology 3D Relation to Life’s Origin The harsh conditions of early Earth were crucial for Evolution of the Cell the origin of life. How do you think life started on Earth? The energy from lightning, UV radiation, and Life likely began through a process called volcanic activity facilitated the chemical reactions abiogenesis, where simple organic molecules needed to synthesize complex molecules. gradually formed more complex structures, The early oceans provided a medium where these eventually leading to the first self-replicating molecules could interact, combine, and eventually organisms, such as RNA molecules. lead to the emergence of simple life forms. This process may have occurred in environments like deep-sea hydrothermal vents or shallow water Primordial Soup Hypothesis pools rich in chemical nutrients. Alexander Oparin and J.B.S. Haldane Suggests that early Earth's oceans were rich with a What do you think the Earth’s condition was? mixture of organic molecules, forming a "soup" Early Earth was a harsh environment with frequent where life began. volcanic activity, intense radiation from the Sun, and This hypothesis posits that simple compounds in the an atmosphere rich in gasses like methane, atmosphere, such as methane, ammonia, hydrogen, ammonia, and water vapor. and water vapor, combine to form more complex The planet also had vast oceans, and its surface organic molecules, like amino acids and nucleotides. was constantly reshaped by geological processes. ○ Atmosphere: Alexander Oparin Rich in gasses like methane, Proposed in 1924 that these organic molecules were ammonia, hydrogen, and water synthesized in the atmosphere and then rained into vapor. the oceans. ○ Environment: He believed that the energy required for these High temperatures, frequent chemical reactions came from lightning and the volcanic activity, and intense Sun's ultraviolet radiation. lightning storms. Earth started with an anaerobic environment. J.B.S. Haldin consequently, only anaerobic organisms can live Independently developing similar ideas in 1929, coined the term "primordial soup." How are these conditions related to how life started? “Primordial" means something that exists from the These conditions provided the necessary ingredients beginning or from the earliest times. and energy sources for chemical reactions that led to “Soup” because it's a mixture of organic molecules. the formation of complex organic molecules. Haldane emphasized the role of ultraviolet radiation The absence of oxygen allowed these molecules to in driving the synthesis of organic molecules. survive and interact, eventually forming the building blocks of life. Stanley Miller and Harold Urey - The harsh environment also drove the evolution of tested the Oparin-Haldane theory and had a more resilient and adaptable forms of life, setting the groundbreaking experiment which demonstrated the stage for the diversity of life we see today. formation of organic molecules, the building blocks of proteins, under conditions that mimic early Earth Theories on the origin of life Abiogenesis: Experiment (1953): Life arose from non-living matter. ○ Simulated early Earth conditions. ○ Mixed water, methane, ammonia, hydrogen. Primordial Soup Hypothesis: ○ Used electrical sparks to mimic lightning. Organic molecules formed in early oceans. Results: This idea posits that early oceans were filled with a ○ Produced amino acids such as alanine, mix of organic molecules, which were synthesized aspartic acid, and glycine, which are from simple compounds present in the atmosphere, fundamental components of proteins and driven by energy sources like lightning and UV some organic molecules. radiation. ○ Demonstrated that life's building blocks can Over time, these molecules underwent further form under early Earth conditions. reactions, leading to the formation of more complex molecules and eventually simple life forms. Organic molecules - building blocks of proteins Hydrothermal Vent Hypothesis: Life began in deep-sea hydrothermal vents These vents provided a rich source of chemicals and a stable environment for life to develop.  Mechanism A: RNA to DNA: The Transition Initial State 2 Key Functions of RNA ○ Cells are initially provided with multiple Informational abundant related nutrients. ○ Analogous to genotype Nutrient Depletion ○ carries information encoded in nucleotide ○ Over time, one of the key nutrients, referred sequence which can be passed on by to as Nutrient 1, becomes exhausted. In process of replication response, the surviving cells develop the ○ Critical for the continuity of genetic capacity to convert an alternative nutrient, information across generations. Nutrient 2, into Nutrient 1. This adaptation is Functional facilitated by the development of specific ○ Analogous to phenotype enzymes. ○ Has specific folded structure that enables it Outcome to interact selectively with other molecules ○ The cells establish a new metabolic pathway and determines how it will respond to the that allows them to continue surviving and ambient conditions thriving even in the absence of Nutrient 1, by ○ Defines the physical and biochemical converting Nutrient 2 into Nutrient 1. characteristics of the organism. Mechanism B: An RNA molecule, enclosed within a membrane-like Initial State structure, undergoes a series of chemical reactions that ○ In this scenario, a substance related to the eventually lead to its transformation into DNA. This transition nutrient normally utilized by the cells is represents a crucial step in the evolution of life, as DNA highly abundant in the environment. became a more stable and reliable medium for storing Enzyme Evolution genetic information. ○ The cells respond to this environmental condition by evolving an enzyme capable of Genetics First: RNA World vs Metabolism First converting the abundant nutrient into the 1. RNA World Hypothesis: necessary nutrient they require. Life began with self-replicating nucleic acids, Cellular Modifications such as RNA or DNA. ○ The cells then undergo modifications to RNA was likely the first genetic material. effectively utilize the abundant nutrient, ensuring their survival and continued Role of RNA: metabolic function. RNA is considered the first genetic material. It was not only a repository for genetic information but also Both Mechanism A and Mechanism B demonstrate the cell's acted as a catalyst for chemical reactions through capacity to adjust to nutrient limitations through metabolic molecules known as ribozymes. alterations, though they differ in the order and type of these adaptations. Genetic Inheritance: Mechanism A highlights the production of new Ribozymes could catalyze their own replication, enzymes to transform one nutrient into another, which allowed genetic material to be passed from Mechanism B concentrates on evolutionary changes one generation to the next. that enhance the cell's ability to utilize an abundant nutrient more efficiently. 2. Metabolism-First Hypothesis: Life originated from self-sustaining networks of LUCA in an Oxygenated Environment metabolic reactions. These metabolic networks likely formed near undersea hydrothermal vents, which provided a steady supply of chemical precursors. These networks were capable of sustaining themselves over time, forming the basis for more complex life forms. LUCA (Last Universal Common Ancestor) Ancestral Prokaryote In the anaerobic environment, LUCA developed mechanisms to utilize the available nutrients efficiently. Although LUCA thrived in an oxygen-free environment, oxygen was still produced as a by-product during its metabolic processes. What will happen if the environment is filled with oxygen How did eukaryotic cells achieve multicellularity? which is not conducive for ancestral prokaryotes? Structural Modifications Enabling Multicellularity Death Cytoplasmic bridges For some of the earliest life forms, the presence of ○ Play a critical role in plants. oxygen was toxic, leading to their extinction. ○ These bridges are formed by cytoskeletal Migration or Strategic Positioning fibers, which create direct connections Some LUCA descendants adapted by migrating or between cells. situating themselves in specific environments where ○ Through these connections, cells can oxygen levels were lower or absent, allowing them to communicate and share resources, allowing survive. them to function as a unified system. Development of Respiratory Capacity (Eubacteria) Extracellular Matrix (ECM) A subset of these organisms evolved the ability to ○ Crucial in Plants utilize oxygen through respiration, which marked the ○ Enabled the formation of cohesion adhesion emergence of eubacteria. This adaptation was molecules, or CAMs, which are essential for crucial for thriving in oxygen-rich environments creating strong cellular junctions. Predatory or Parasitic Relationships ○ These junctions not only hold cells together Others became predatory or parasitic, targeting but also facilitate communication between organisms that had developed respiratory capacities. them. This interaction often led to a symbiotic relationship, where one organism would benefit from the other, Practice Questions: eventually leading to more complex evolutionary 1. The Miller-Urey experiment was significant because it pathways. demonstrated that: a) Life can spontaneously generate from non-living matter. Endosymbiotic Theory b) Simple organic molecules could form under the conditions Origin of eukaryotic cells from prokaryotic thought to resemble early Earth's atmosphere. organisms. Mitochondria (alphaproteobacteria) and c) DNA can be synthesized from inorganic compounds. chloroplasts (cyanobacteria) were once free-living d) RNA molecules have catalytic properties that can support bacteria. early life forms. Large, anaerobic, heterotrophic prokaryote ingested a small, aerobic prokaryote leading to a symbiotic 2. Which hypothesis suggests that early life forms relied relationship. As natural selection takes place and on chemical reactions for energy, leading to the these endosymbionts survive, they become development of metabolic pathways before the permanent and evolve into our modern day formation of genetic material? eukaryotic cells. a) Abiogenesis Mitochondria are derived from aerobic, b) Primordial Soup Hypothesis heterotrophic bacteria. alpha-proteobacteria. c) Metabolism-First Hypothesis Chloroplasts likely arose from photosynthetic d) RNA World Hypothesis bacteria. Chloroplast evolved from cyanobacteria, the 3. In the context of the RNA World Hypothesis, why is light-harnessing small organisms that abound in RNA considered a key molecule in the evolution of life? oceans and freshwater. a) RNA molecules are more stable than DNA and can easily So for other organelles like Endoplasmic reticulum replicate. and nuclear membranes might have been derived b) RNA can store genetic information and also catalyze from a portion of the cell’s outer plasma membrane chemical reactions, making it both an informational and that became internalized and then modified into a functional molecule. different type of membrane. c) RNA forms the backbone of all current life forms, serving as the primary genetic material. Evidence: d) RNA molecules are capable of photosynthesis, which Both mitochondria and chloroplasts contain their own provided the first energy source for early life. DNA, which is quite similar to bacterial genomes. Additionally, these organelles replicate in a manner Properties of Cell and Cell Structure akin to binary fission, a process used by bacteria. The ribosomes found in mitochondria and Cell and Molecular Biology chloroplasts also bear a closer resemblance to those reductionist, based on the premise that studying in bacteria than to those in eukaryotic cells. the parts of the whole can explain the character of the whole. Lynn Margulis ○ by studying individual components such as Popularized the theory in the 1960s organelles, molecules, and genes, insights Highlighted symbiosis in evolution can be gained into how cells function as a whole. Discovery of Cells Cells are highly complex and organized Robert Hooke (1665): Cells are complex, organized, regulated, and share ○ first observed cells in cork. common features across species. ○ used a more complex compound Highly Complex and Organized: ○ Cells exhibit intricate structures and microscope which featured a double lens functions. system. Regulated Processes: ○ noticed small, box-liked structures or ○ Cellular activities are tightly regulated and honeycomb-like structures which he termed coordinated. “cells” Conserved features across species: Antoine van Leeuwenhoek (1670s) ○ Similar Structures: Shared cellular ○ observed living cells in pond water and structures among different species ○ Metabolic Features: Conserved metabolic called them “animalcules”. pathways and processes ○ first to describe various forms of bacteria from water soaked with pepper and from Cells are the basic units of life scraping of his teeth Known for their complexity and organization. Microscopy advancements: improved cell viewing Complexity and Organization Cells contain various organelles with specific roles Cell Theory (e.g., nucleus for growth control, mitochondria for energy production). 1. All organisms are composed of one or more cells Regulated Processes This principle was first articulated by Matthias Activities like cell division and signaling pathways Schleiden and Theodor Schwann, are carefully controlled to ensure correct function. ○ showed that both plants and animals are Conserved Features Across Species made up of cells. Some structures (e.g., ribosomes) and processes Unicellular - bacteria, archaea, viruses (e.g., glycolysis) are shared among all life forms, showing fundamental importance. Multicellular - animals and plants Prokaryotes might be confused as unicellular, and Levels of Cellular and molecular organization eukaryotes as multicellular. ○ However unicellular prokaryotes: protozoa, paramecium, and amoeba Prokaryotes can rarely be multicellular however they can exhibit multicellular forms when they form large colonies, or are in a population. ○ Examples include our Actinomyces and cyanobacteria. 2. The cell is the structural unit of life: Cells are the basic building blocks of all living organisms, forming the structure of every tissue and organ. 3. Cells arise from pre-existing cells by division: Rudolf Virchow proposed this concept, New cells are produced from the division of existing cells, not from spontaneous generation. This is the theory that living organisms develop from Illustrates different aspects of cellular structure & function: nonliving matter. Inset 1: This image shows an epithelial layer of cells lining Basic Properties of Cells the intestinal wall. On the apical surface, you can Ability to sustain life (growth and reproduction) see microvilli, which are tiny, finger-like projections Cell Culture: Cells can grow and reproduce in culture that increase the surface area for nutrient for extended periods of time. absorption. The basal region of these cells contains ○ HeLa Cell Line numerous mitochondria, which are crucial for Tumor cells isolated from Henrietta providing the energy required for cellular functions. lacks by George Gey in 1951. Inset 2: The first human cells to be Here, we zoom in on the apical microvilli. Each successfully cultured indefinitely; microvillus is composed of a bundle of essential for research. microfilaments. These microfilaments, primarily Crucial tools for cell biologists, made of actin, support the microvilli's structure and aiding in various scientific medical function, helping to maximize the cell's ability to advancements. absorb nutrients. Inset 3: Genetic Instructions: This inset focuses on actin protein subunits, which ○ Each daughter cell receives a complete set are the building blocks of the microfilaments found in of genetic instructions the microvilli. Actin subunits polymerize to form long, thin filaments that provide structural support and Cells Acquire and Utilize Energy shape to the microvilli. Photosynthesis: Inset 4: ○ Provides fuel for all living organisms. This image depicts an individual mitochondrion. ○ Through photosynthesis, plants convert Mitochondria are known as the powerhouses of the sunlight into chemical energy, producing cell because they generate the majority of the cell’s glucose and oxygen. energy through the production of ATP. Inset 5: Energy Source for Animals: Here, we see a portion of the inner membrane of a ○ Animal cells derive energy from mitochondrion. The membrane features stalked photosynthesis products, primarily glucose. particles that project from its surface. These particles correspond to the sites where ATP is synthesized, ATP Production: playing a crucial role in the energy production ○ Cells convert glucose into ATP, providing process. readily available energy. Inset 6 and 7: ○ ATP is a molecule that stores and provides These insets present molecular models of the readily available energy for various cellular ATP-synthesizing machinery. These models illustrate activities, such as muscle contraction, nerve the detailed structure of the proteins involved in the impulse transmission, and biochemical synthesis of ATP, highlighting how the molecular synthesis. components work together to produce energy for the r=the energy currency of cell cell. Each of these insets provides a closer look at specific cellular structures and their functions, Cells Carry Out a Variety of Chemical Reactions illustrating the complexity and organization required Cells require enzymes to catalyze reactions. for cellular processes. Enzymes lower the activation energy needed for reactions. Cells Possess Genetic Program and the Means to Use It Metabolic pathways consist of a series of Genetic Program enzyme-catalyzed reactions. Genes encode information for building cells and Cells regulate enzyme activity to control metabolic organismsThis program is encoded in the DNA, processes. which contains genes responsible for various cellular functions. Enzymes as Catalysts Enzymes are specialized proteins that accelerate Functions of Genes: chemical reactions. Reproduction They lower the activation energy needed for ○ Directs cellular division and replication. reactions to occur, making processes more efficient. ○ Encode information essential for cellular reproduction, ensuring accurate cell division Examples of Enzymes and replication. Ligases - DNA Ligase: Zips up DNA during Activity: replication and repair. ○ Regulates cellular functions and responses. Lipases - Help digest fats in the gut. ○ Genes regulate cellular activity, influencing Amylase - In saliva, converts starches into sugars. how cells respond to their environment and DNA Polymerase - Involved in DNA synthesis perform their functions during replication. Structure: ○ Determines cellular and organismal Role in Metabolism structures. Enzymes facilitate metabolic pathways, which are ○ Determine the structure of cells and sequences of enzyme-catalyzed reactions. organisms by directing the synthesis of Metabolic pathways are essential for cellular proteins and other molecules that form metabolism. cellular components and tissues. Regulation of Enzyme Activity Cells regulate enzyme activity to ensure that In essence, genes are the blueprint for life, guiding every metabolic processes meet the cell's current needs. aspect of cellular and organismal development and function. Cells Engage in Mechanical Activities Cells are Capable of Producing More of Themselves Cells are sites of bustling activity. Cell Reproduction: They exhibit movement through cytoskeletal ○ Reproduce to generate new cells. dynamics of the cytoskeleton, a network of protein  fibers that provide structural support and facilitate ○ more complex, containing organelles like the cell movement. nucleus, mitochondria, and endoplasmic Cells divide and replicate to produce new cells. reticulum, which compartmentalize various Intracellular transport moves molecules and functions. organelles within cells ensuring that cellular components are correctly positioned. Genetic Material Cellular motility includes processes like muscle Packaging: contraction and cell migration which are crucial for ○ Prokaryotic - genetic material is located in a development, repair, and immune responses. nucleoid region without a surrounding membrane, Cells Are Able to Respond to Stimuli ○ Eukaryotic - genetic material is enclosed in Cells detect environmental changes through a membrane-bound nucleus. receptors which initiate signal transduction Amount pathways. ○ Eukaryotic - possess more genetic material Signal transduction pathways relay signals from the than prokaryotes, reflecting their complexity cell surface to the interior. Form Cells can respond to stimuli such as light, ○ Prokaryotes - single, circular DNA molecule temperature, and chemicals. ○ Eukaryotes - multiple linear chromosomes, Responses include changes in gene expression, tightly wound around histone proteins. enzyme activity, and cell behavior enabling cells to adapt and maintain homeostasis. Cytoplasm Eukaryotic cells ○ contain membrane-bound organelles like Cells Are Capable of Self-Regulation mitochondria and the endoplasmic reticulum, Self-regulation involves constant monitoring of which compartmentalize and enhance internal conditions. cellular efficiency. Feedback mechanisms help maintain homeostasis. ○ They also have a complex cytoskeleton that Cells adjust metabolic pathways based on nutrient provides structural support and assists in availability. intracellular transport. Regulation ensures balanced growth, division, and While both cell types have ribosomes, eukaryotic ribosomes are larger and more complex. differentiation. Cellular Reproduction Cells Evolve Eukaryotic cells Evolution occurs through genetic variation and ○ reproduce through mitosis, ensuring natural selection. identical chromosomes in each daughter Mutations introduce new genetic variations. cell. Selective pressures favor advantageous traits. Prokaryotic cells ○ divide by simple fission, a less complex Evolutionary changes can lead to increased process that does not involve mitosis. complexity and adaptation. Cells' evolutionary history is reflected in conserved Locomotion genetic and biochemical features. Eukaryotic cells ○ use mechanisms like cytoplasmic streaming, cilia, and flagella for movement. Two Fundamentally Different Classes of Cells ○ flagella move in a wave-like motion and are Prokaryotic Cells: structurally more complex ○ Generally smaller, lack membrane-bound Prokaryotic cells ○ Flagella rotates like a propeller. organelles ○ No nucleus, genetic material is found in nucleoid region Viruses ○ Examples: Bacteria Origin: Arise ~3.7 billion Definition: Non-cellular entities years ago Structure: Protein coat with genetic material Eukaryotic Cells: Infection: Hijack host cells to replicate Impact: ○ Generally larger Disease and genetic engineering tools ○ Nucleus, contain membrane-bound organelles The Human Perspective: Prospect of Cell ○ Examples: Protists, animals, plants, fungi Replacement Therapy Complexity Objective: Replace damaged or diseased cells Prokaryotic cells Methods: Stem cell therapy, tissue engineering ○ simpler, lacking membrane-bound Potential: Treat degenerative diseases, injuries organelles, so cellular functions occur in the Challenges: Ethical issues, immune rejection cytoplasm or near the plasma membrane. Eukaryotic cells  ○ M Phase Length: Experimental Pathways: The Origin of Eukaryotic Cells Calculated by the percentage of cells engaged in mitosis or Endosymbiotic Theory: Mitochondria and cytokinesis. chloroplasts originated from symbiotic relationships Evidence: Genetic similarities to bacteria Duration: Experimental Support: Studies on mitochondrial M phase lasts about 1 hour in mammalian cells. DNA and chloroplasts Interphase can last from days to weeks, depending on cell type. Cell Division Cell Cycles in Vivo: Three broad categories of cells Highly specialized cells lack the ability to divide The Cell Cycle ○ Neurons, muscle cells, red blood cells Cell Division - New cells arise from other living cells ○ Once differentiated, they remain in that state Multicellular Organisms - A single-celled zygote until they die. divides countless times, forming complex organisms. Cells that normally do not divide but can be Continuous Division - Even in mature organisms, induced to begin DNA synthesis and divide when certain tissues like bone marrow or the intestinal given an appropriate stimulus lining constantly undergo cell division. ○ Liver cells and lymphocytes Cells that normally possess a relatively high Types of Cell Division: level of mitotic activity Mitosis: Produces genetically identical cells. ○ Stem cells i.e. hematopoetic stem cells that Meiosis: Produces cells with half the genetic content give rise to red and white blood cells and for sexual reproduction. stem cells at the base of numerous epithelia that line the body cavity and body surface. Evolutionary Link - Mitosis and meiosis connect ○ Asymmetric Cell Division offspring to parents and all eukaryotic life to ancient Important property of stem cells origins. Two daughter cells have different sizes, components, or fate Phases of the Cell Cycle One uncommitted daughter cell and Cell Cycle: Dividing cells go through a series of one daughter cell that becomes a stages known as the cell cycle. differentiated cell of that tissue. Cell Cycle Length Major Phases: Varies from 30 minutes (e.g., cleaving frog embryos) M Phase: to several months (e.g., slow-growing liver tissue). ○ Mitosis: Duplicated chromosomes are separated into two nuclei. Quiescent Cells (G0): ○ Cytokinesis: The entire cell divides into two Cells in a non-dividing state but capable of daughter cells. re-entering the cycle if conditions change. Interphase: The period between divisions, where the cell grows and performs metabolic activities. G0 vs G1: ○ G1 Phase: Quiescent cells are arrested before DNA synthesis The gap between the end of mitosis (G1) but can proceed into the cell cycle when given and the beginning of DNA synthesis a growth-promoting signal. (S phase), following G2, S, and M phases. Control of the Cell Cycle ○ S Phase: Importance of Cell Cycle Study: DNA replication and histone Vital for understanding cancer, as it results from a synthesis occur during this phase, failure in cell division regulation. doubling the number of nucleosomes in chromosomes. Rao and Johnson Experiment: ○ G2 Phase: Demonstrated that regulatory factors in the Period between the end of DNA cytoplasm affect cell cycle activities by fusing synthesis (S phase) and the start of mammalian cells at different stages of the cycle. M phase, ensuring proper cell preparation for division. ○ Determining S Phase Length: Measured by the percentage of cells Mitotic Induction: with radioactively labeled nuclei in Fusing a mitotic cell with cells in G1, G2, or S phase an asynchronous culture. resulted in premature chromosomal compaction,  suggesting that diffusible mitotic factors promote the transition from G2 to M phase. Key Insight: The transition from G2 to M phase is controlled by stimulatory agents in the cytoplasm. Maturation-Promoting Factor (MPF): MPF initiates M phase in the cell cycle. Two Subunits of MPF: Kinase Subunit: Transfers phosphate groups to specific proteins, driving the cell into mitosis. Cyclin Subunit: Regulates the kinase, rising and falling with the cell cycle. Cyclin's Role: The kinase is inactive when cyclin levels are low; it activates when cyclin levels rise, promoting mitosis. Conclusion: Cell cycle progression relies on a kinase controlled by cyclin, which fluctuates predictably. Mitosis and Cytokinesis