Levels of Organization PDF

Levels of organization Dr. Shwetha S Durgad 1st B.Sc A Subcellular ----> Multicellular ❑ Anatomy refers to the internal and external structures of the body, their physical relationships, & their organization ❑ Physiology refers to the study of the functions of those struct...

Levels of organization Dr. Shwetha S Durgad 1st B.Sc A Subcellular ----> Multicellular ❑ Anatomy refers to the internal and external structures of the body, their physical relationships, & their organization ❑ Physiology refers to the study of the functions of those structures Essentials for life ❑Requirement for nutrients ❑Absorption of nutrients ❑Circulation of energy sources ❑Respiration ❑Metabolism Homeostasis ❑Refers to a stable internal environment ❑Includes specific concentrations of nutrients, oxygen, water etc. ❑Homeostatic mechanisms include: ❑Receptors ❑Set points ❑Effectors  Homeostatic Response to Food Intake Homeostatic Response to Vomiting Profuse vomiting leading to loss of fluids and Intake of food Stimulus Stimulus acidic digestive juices. Sensors (osmoreceptors in the hypothalamus and Detection of increased blood glucose baroreceptors in blood vessels) detect changes in Receptor levels. Receptor blood volume and pH levels. Pancreas responds to changes in The hypothalamus in the brain receives signals blood glucose. Set point indicating dehydration and altered pH levels. Set point Kidneys conserve water and electrolytes, and the Release of insulin by the pancreas. Effector respiratory system adjusts breathing patterns. Effector Decreased urine output to conserve water & Uptake of glucose by body cells, altered breathing rate to balance pH levels, Response reducing blood glucose levels. Response helping restore fluid balance & pH to maintain homeostasis. Factors homeostatically regulated ❑Concentration of nutrients ❑Concentration of O2 & CO2 ❑Concentration of waste products ❑pH ❑Concentration of water, salt, & electrolytes ❑Volume and pressure ❑Temperature Contributions of the body systems to homeostasis ❑Circulatory system –transport of O2 & CO2, nutrients, waste, electrolytes, hormones ❑Digestive system – breakdown of nutrients for absorption, supply water & electrolytes ❑Respiratory system – gaseous exchange ❑Urinary system – removal of excess salts, water, acid, waste products ❑Skeletal system – support and supply of Ca2+ ❑Muscular system – locomotion ❑Nervous system – coordinates most activities and generates responses ❑Integument system – provides physical barriers ❑Immune system – defense against invaders and cancerous cells ❑Endocrine system – a major regulatory system; maintains long-term processes  Feedback regulation of bodily processes Positive feedback  Disruptions in homeostasis can lead to illness and death Anatomical planes Body cavities  Membranes ❑ Inner thoracic & abdominopelvic cavities are lined by connective membranes ❑ Heart is lined by pericardium ❑ Lungs are lined by the parietal and visceral pleura ❑ Abdominopelvic cavity is lined by the peritoneal membrane Case 1 Food for thought: JR has the “stomach flu” that is going around campus and has been vomiting profusely for the past 24 hours. Not only has she been unable to keep down fluids or food but she has also lost the acidic digestive juices secreted by the stomach that are normally reabsorbed back into the blood farther down the digestive tract.  What body systems respond to resist/ overcome these changes? In what ways might this condition threaten to disrupt homeostasis in JR’s internal environment? What homeostatically maintained factors are moved away from normal by her profuse vomiting? Fluid loss → Plasma volume → pH Adjustments made Urinary system Circulatory system Respiratory system Nervous & Endocrine systems Case 2  ‘HIV’ causes widespread infections and the occurrence of rare forms of cancers Which functionality of the body is affected? Cell & Cell organelles Cell under EM Various Shapes Various Shapes Skeletal Epithelial Muscle Cell Neuron Rod cell Pyramidal cell Human sperm cell Cone Cell Human ovum  Nucleus Human genome – 3.2 billion nucleotides 30K genes > 205 cm (diploid) Structural Components of the Nucleus: 1.Nuclear Envelope: A double-membrane structure that encases the nucleus. The outer membrane is continuous with the endoplasmic reticulum. The nuclear envelope contains nuclear pores that regulate the exchange of substances between the nucleus and the cytoplasm. 2.Nuclear Pores: Large protein complexes that span the nuclear envelope, allowing the selective exchange of molecules such as RNA and proteins between the nucleus and the cytoplasm. 3.Nucleolus: A dense, spherical region within the nucleus where ribosomal RNA (rRNA) synthesis and ribosome assembly occur. The nucleolus plays a crucial role in protein synthesis by producing ribosomes, which are essential for translating mRNA into proteins. 4.Chromatin: The complex of DNA and proteins (histones) within the nucleus. Chromatin exists in two forms: euchromatin, which is less condensed and actively involved in transcription, and heterochromatin, which is more condensed and transcriptionally inactive. 5.Nuclear Matrix: A network of fibers within the nucleus that provides structural support and may play a role in organizing the chromatin and other nuclear components.  Key Functions of the Nucleus: 1.Genetic Information Storage: The nucleus houses the cell's genetic material in the form of DNA. DNA is organized into chromosomes, which contain the instructions necessary for the development, functioning, growth, and reproduction of the cell. 2.Regulation of Gene Expression: The nucleus controls the expression of genes, determining which genes are turned on or off at any given time. This regulation is crucial for cell differentiation, adaptation to environmental changes, and the overall functioning of the organism. 3.Replication and Cell Division: Before a cell divides, the DNA in the nucleus replicates to ensure that each daughter cell receives an identical set of genetic instructions. This process is fundamental to growth, development, and tissue repair. 4.RNA Synthesis: Within the nucleus, transcription occurs, where DNA is used as a template to synthesize messenger RNA (mRNA). The mRNA then exits the nucleus and enters the cytoplasm, where it directs protein synthesis on ribosomes.  Plasma membrane The fluid mosaic model was proposed by S.J. Singer and Garth L. Nicolson (1972) https://wordwall.net/resource/27807075/biology/cell-membrane-diagram Permeability and transport Crossing the plasma membrane Carrier mediated transport The process of transferrin receptor-mediated endocytosis, which involves the uptake of holotransferrin (iron-bound transferrin) into cells, does require energy.  Types of transporters  Channels Pumps  Passive transport Endocytosis & Exocytosis Osmosis  Case Patient Profile: Emily, 45 years old, admitted for severe dehydration due to vomiting and diarrhea. In the hospital, Emily is administered IV solution to restore blood volume and electrolyte balance. Identify the type of osmosis mechanism that helped Emily to recover ? Endoplasmic reticulum & ribosomes ER under EM  Secretory pathway for Proteins synthesized by RER  Smooth endoplasmic reticulum The smooth endoplasmic reticulum (smooth ER) is a membrane-bound organelle found in eukaryotic cells. 1. Lipid Metabolism: One of the primary functions of the smooth ER is lipid metabolism. It is involved in the synthesis of lipids, such as phospholipids and cholesterol. These lipids are essential components of cell membranes and are also used to make hormones and other important cellular molecules. 2. Detoxification: The smooth ER is involved in detoxifying harmful substances in the cell. It contains enzymes that help to break down drugs, alcohol, and other toxins, making them easier for the cell to eliminate. 3. Calcium Storage: The smooth ER also plays a role in storing and regulating calcium ions in the cell. Calcium ions are important for various cellular processes, including muscle contraction, cell signaling, and enzyme activity. 4. Steroid Hormone Production: In certain specialized cells, such as those in the adrenal glands and reproductive organs, the smooth ER is involved in the production of steroid hormones. These hormones play key roles in regulating various physiological processes in the body.  General Functions of the Endoplasmic Reticulum Intracellular Transport: The ER acts as a transport network within the cell, moving synthesized molecules to different locations, such as the Golgi apparatus, lysosomes, or the plasma membrane. Quality Control: The ER has quality control mechanisms to ensure that only properly folded and functional proteins are transported to their final destinations. Misfolded proteins are often targeted for degradation.  Role in Health and Disease Dysfunction in the ER can lead to various diseases, including: Protein Misfolding Diseases: Conditions like cystic fibrosis and Alzheimer's disease are linked to problems in protein folding and processing. Liver Diseases: Impaired detoxification functions of the smooth ER can lead to liver damage and diseases such as hepatitis and cirrhosis. Metabolic Disorders: Abnormalities in lipid metabolism in the smooth ER can contribute to conditions like fatty liver disease and cholesterol-related disorders. Few interesting pointers……. 1. Muscle cells have a specialized ER – sarcoplasmic reticulum 2. Liver cells have SER containing detoxifying enzymes…… increases soon after drug administration Golgi apparatus Electron micrograph of transitional elements and cis Golgi network Transport vesicles bud from the transitional Within the golgi…… elements of the ER, which are nearly free of 1. Processing the raw materials into finished ribosomes and fuse with the cis Golgi network, products thereby transferring newly made proteins and 2. Sorting, directing, and packaging to lipids from the ER to the Golgi apparatus respective destinations  Intracellular compartments involved in biosynthetic/secretory and endocytic pathways Endocytic pathway So what is pinocytosis? Secretory/ exocytic pathway Cargo sorting  Ribosomes (80s) (60s) (40s) Cellular Function: Proteins synthesized by ribosomes perform a vast array of functions, including enzymatic activity, structural roles, signaling, and transport, making ribosomes essential for cell survival and function. Structure: Composition: Ribosomes are composed of ribosomal RNA (rRNA) and proteins. Subunits: They consist of two subunits: a larger one and a smaller one. In eukaryotes, the large subunit is 60S, and the small subunit is 40S, combining to form an 80S ribosome. Location: Ribosomes can be found floating freely in the cytoplasm or attached to the endoplasmic reticulum (forming rough ER). Protein Synthesis: Ribosomes are the molecular machines that synthesize proteins by translating messenger RNA (mRNA) into polypeptide chains.Translation Process: mRNA, transcribed from DNA in the nucleus, carries the genetic instructions to the ribosome. Transfer RNA (tRNA) brings the appropriate amino acids to the ribosome. The ribosome reads the sequence of mRNA codons and facilitates the binding of tRNA anticodons, adding the corresponding amino acids to the growing polypeptide chain. This process continues until a stop codon is reached, signaling the end of protein synthesis. Polyribosomes: Multiple ribosomes can simultaneously translate a single mRNA molecule, forming a structure known as a polyribosome or polysome, which increases the efficiency of protein synthesis.  Lysosomes Autophagy Lysosomal storage disorders  Structure 1.Membrane-bound: Lysosomes are enclosed by a single lipid bilayer membrane, which protects the rest of the cell from the digestive enzymes contained within. 2.Hydrolytic Enzymes: These enzymes, such as proteases, lipases, nucleases, and glycosidases, function best in the acidic environment of the lysosome (pH ~4.5-5). The enzymes are synthesized in the rough endoplasmic reticulum, processed in the Golgi apparatus, and delivered to lysosomes. 3.pH Maintenance: Lysosomes maintain an acidic pH through the action of proton pumps (H+-ATPases) in their membranes.  Functions of Lysosomes Digestion of endocytosed material: Lysosomes degrade material brought into the cell via endocytosis, including nutrients, pathogens, and cell debris. Autophagy: Lysosomes degrade and recycle cellular components through autophagy, a process where damaged or unnecessary organelles and proteins are encapsulated in autophagosomes and then fused with lysosomes for breakdown. Phagocytosis: Specialized cells like macrophages engulf large particles such as bacteria or dead cells, forming phagosomes that subsequently fuse with lysosomes for digestion. Recycling of cellular components: By breaking down macromolecules, lysosomes provide raw materials for new synthesis, helping maintain cellular homeostasis. Programmed cell death (Apoptosis): Lysosomes can release their enzymes into the cytoplasm to help initiate apoptosis, a controlled process of cell death.  Peroxisomes Peroxisomes Structure: Composition: Peroxisomes are small, membrane-bound organelles that contain a variety of enzymes. Membrane: A single lipid bilayer encloses the enzymes within the peroxisome. Matrix: Inside the peroxisome, the matrix contains enzymes such as catalase and various oxidases. ❖ Detoxifying enzymes ❖ Oxidative enzymes – produce H2O2 ❖ catalase Importance: Cellular Protection: By breaking down toxic substances and reactive oxygen species, peroxisomes protect cells from oxidative damage. Metabolic Functions: Their roles in lipid metabolism and detoxification are essential for maintaining cellular homeostasis and overall health. Neurological Health: Defects in peroxisomal functions can lead to neurological disorders due to the importance of peroxisomes in maintaining the myelin sheath and overall neuronal function. Understanding the detailed roles and functions of ribosomes and peroxisomes highlights their importance in maintaining cellular health and function. mitochondria ❖Cellular respiration ❖Cell autonomous ❖Fission and fusion ❖mitophagy  Mitochondria under EM unhealthy mitochondria Normal mitochondria Mitochondria and energy production Why Mitochondrial energy production? Cytoskeleton  Centrioles ❖ Centrioles are paired barrel-shaped organelles located in the cytoplasm of animal cells near the nuclear envelope ❖ Centrioles play a role in organizing microtubules that serve as the cell's skeletal system ❖ They help determine the locations of the nucleus and other organelles within the cell ❖ Help in movement of chromosomes during cell division ❖ Help in the formation of cilia and flagella