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  2. 2. Introduction What are the basic activities of living organisms? 1. Maintenance of the individual 2. Perpetuation of the species To maintain an organism: There must be synthesis of new molecules to replace the degraded and outdated molecules. Cells obtain energy from biological fuels for various cellular function. 2 Tewekel R 2/3/2023
  3. 3. Introduction … To perpetuate the species: There is storage and transmission of genetic information from generation to generation at molecular level. Genetic macromolecule, DNA is replicated to give daughter DNA that passes to the offspring. In an organism DNA is also transcribed in to RNA and then RNA is translated to proteins of variable uses. Is biochemistry helps to understand the activities of life at molecular and cellular level? yes 3 Tewekel R 2/3/2023
  4. 4. What is biochemistry? Biochemistry can be defined as the science of the chemical basis of life (Greek bios “life”). The science of the chemical constituents of living cells and of the reactions and processes they undergo. The science concerned with the various molecules that occur in living cells and organisms and with their chemical reaction. Tewekel R 4 2/3/2023
  5. 5. Anything more than a superficial comprehension of life – in all its diverse manifestation - demands a knowledge of biochemistry. By this definition, Biochemistry encompasses large areas of cell biology, molecular biology, and molecular genetics. The aim of biochemistry is to describe & explain all biochemical processes of living cells in molecular terms. Tewekel R 5 2/3/2023
  6. 6. The major objective of biochemistry is the complete understanding of all biochemical processes associated with living cells at the molecular level. To achieve this objective, biochemists have sought to isolate the numerous molecules found in cells, determine their structures, and analyze how they function. Many techniques have been used for these purposes. Tewekel R 6 2/3/2023
  7. 7. Health depends on  a harmonious balance of biochemical reactions occurring in the body, and  Disease reflects  abnormalities in biomolecules, biochemical reactions, or biochemical processes ; this is the main concern of medical biochemistry. Tewekel R 7 2/3/2023
  8. 8. The scope of biochemistry The knowledge and skills of biochemistry is applied in a number of areas. Genetics – the biochemistry of nucleic acids Physiology – study of normal body function Pharmacology and pharmacy – for designing of therapeutic drugs, the metabolism of drugs . Toxicology – to understand toxic effect of metabolites and xenobiotics Tewekel R 8 2/3/2023
  9. 9. The scope of biochemistry… Pathology (the study of disease) – e.g., inflammation, cell injury and cancer. Each pathologic condition has biochemical basis. Microbiology, zoology and botany Medicine – the understanding and maintenance of health and effective treatment of diseases. Public health Nutrition and preventive medicine Agriculture and biotechnology In forensic medicine Tewekel R 9 2/3/2023
  10. 10. Two categories of biochemistry Descriptive biochemistry: deals with qualitative and quantitative nature (character, complexion & makeup) of molecules in the living cells. Major Molecules in humans include: Water, Macromolecules (Carbohydrates, Proteins, Lipids and Nucleic acids) and Micro molecules which include Vitamins & Minerals. Dynamic biochemistry: deals with reactions and mechanisms of reactions in the living cells. Tewekel R 10 2/3/2023
  11. 11. The Biomolecular Hierarchy Atoms/ elements Simple Molecules (are the Units for Building Complex Structures) Metabolites and Macromolecules Organelles Membranes The Unit of Life is the Cell 11 Tewekel R 2/3/2023
  12. 12. carbon atom organ system DNA molecule organelle cell tissue organ organism population community ecosystem biosphere 12 Tewekel R 2/3/2023
  13. 13. Figure: structural hierarchy in the molecular organization of Cells. For example the nucleus is an organelle containing several Types of supramolecular complexes, including chromosomes. 13 Tewekel R 2/3/2023
  14. 14. Tewekel R 14 2/3/2023
  15. 15. Elemental Composition of the living system More than 99% of the elements in animals’ bodies are accounted for by four elements, carbon, hydrogen, oxygen, and nitrogen. Most of the H and O occur as H2O, which alone make 60-70% of cell mass. These elements are the major constituents of organic molecules, called biomolecules, on which most living organisms depend. 15 Tewekel R 2/3/2023
  16. 16. The second biologically important group of elements, which account only about 0.5% of the body mass, are the seven essential mineral elements. These elements include sodium, potassium, calcium, magnesium, chlorine, sulfur and phosphorus. Sulfur and phosphorus are also components of some biomolecules. Tewekel R 16 2/3/2023
  17. 17. The chemical components of cells Water Water accounts for about 60-70% of the weight of the cell. Other cellular constituents are either dissolved or suspended in water. Organic Compounds/Biomolecules They are nucleic acids, proteins, polysaccharides (carbohydrates) and lipids. 17 Tewekel R 2/3/2023
  18. 18. • Proteins accounts 10-20% of the weight of the cell. • Nucleic acids account 7-10% of the cell weight. • Polysaccharides usually account for 2-5% of the cell weight. • About 3% of cell weight is due to lipids. • Lipids content may be higher in adipocytes or fat cells. • Proteins may account more of cell weight in cells like erythrocytes. Tewekel R 18 2/3/2023
  19. 19. Other low molecular weight organic compounds may account for 4% of cell weight. They are monosaccharaides, amino acids, fatty acids, purine and pyrimidine nucleotides, peptides, hormones, vitamins and coenzymes. Tewekel R 19 2/3/2023
  20. 20. Inorganic Compounds Inorganic compounds account for the rest of the cell weight. They are cations like sodium, potassium, calcium, magnesium, copper, iron and anions like chloride, phosphate, bicarbonate, sulfate, iodide and fluoride. They exist as electrolytes (sodium ion) and compounds ( calcium phosphate in bone) in the living system Tewekel R 20 2/3/2023
  21. 21. Biochemical reactions in the living system Metabolism: the sum total of chemical reactions in the living cell/organism. Can be of two type 1. Catabolism: break down or degradation reactions Examples: digestion, oxidation of glucose… 2. Anabolism: Synthetic reactions Examples: Synthesis of proteins, nucleotides… Tewekel R 21 2/3/2023
  22. 22. Metabolic errors: abnormalities in metabolism. Inherited and acquired type Waste products: inevitable waste products are produced when biochemical reactions are undergoing in the living system. Tewekel R 22 Biochemical reactions in the living system… 2/3/2023
  23. 23. Building blocks – Simple sugars – Amino acids – Nucleotides – Fatty acids Macromolecules – Polysaccharides – Proteins /peptides – RNA or DNA – Lipid/fats Anabolic Catabolic 23 Tewekel R 2/3/2023
  24. 24. Metabolism of dietary components In order to survive, humans must meet two basic metabolic requirements:  we must be able to synthesize everything our cells need that is not supplied by our diet, and  we must be able to protect our internal environment from toxins and changing conditions in our external environment. Tewekel R 24 2/3/2023
  25. 25. Metabolism of dietary components… • In order to meet these requirements, we metabolize our dietary components through four basic types of pathways:  fuel oxidative pathways,  fuel storage and mobilization(utilization) pathways,  biosynthetic pathways, and  detoxification or waste disposal pathways. Tewekel R 25 2/3/2023
  26. 26. Figure: General metabolic routes for dietary components in the body Tewekel R 26 2/3/2023
  27. 27. Role of biochemistry in medicine and other health sciences Biochemistry helps to understand the biochemical changes and related physiological alteration in the body. Pathophysiology of any disease is studied through biochemical changes. Example 27 Tewekel R 2/3/2023
  28. 28. Role of biochemistry… In the present scenario, many people rely in taking multivitamin and minerals for better health. The function and role of vitamins and minerals are best described by biochemistry. There are many disorders due to hormonal imbalance especially in women and children. The formation, role of hormones and disorders in due to deficiency or excess of hormones are best studied by biochemistry. To determine health effects of toxins and pollutants. Tewekel R 28 2/3/2023
  29. 29. Role of biochemistry… Almost all the diseases or disorders have some biochemical involvement. So the diagnosis of any clinical condition is easily possible by biochemical estimations. Examples: 1. In kidney disorders and chemotherapy treatment urine test is used to understand the extent of excretion of drugs or other metabolites, the change in pH, the color of urine etc. 2. In diabetes blood glucose level test helps to understand the severity of diabetes disorders. Biochemical test for ketone bodies in urine also indicate the stage of diabetes. Tewekel R 29 2/3/2023
  30. 30. Role of biochemistry… 3. Liver function tests help to understand the type of disease or damage to the liver, the effect of any medication on liver. 4. Evaluation of blood cholesterol level and lipoproteins help to understand the proneness of the patient to cardiovascular disease. Thus importance of biochemical tests is to help to monitor the patient health condition regularly during the treatment. Tewekel R 30 2/3/2023
  31. 31. Role of biochemistry… Biochemistry gives an idea of the composition of drugs and their chance of degradation. It also gives an idea how drugs are metabolized by many biochemical reactions in the presence of enzymes. This helps to avoid drugs with poor metabolism or those with excessive side effects from being prescribed or dispensed to patients. Biochemical tests help to fix the specific half life or time of expiry of drugs. Tewekel R 31 2/3/2023
  32. 32. Role of biochemistry… For maintenance of health, optimum intake of many biochemicals like vitamins, minerals, proteins, essential fatty acids, water etc… is necessary. Biochemistry gives an idea of what we eat i.e. it’s components and possible alteration due to their deficiency or excess. Helps to understand the importance of biomolecules to health. The nutrient value of food materials can also be determined by biochemical tests. Helps Physician to prescribe limited usage of certain foods like excess sugar for diabetics, excess oil for heart problem prone patients etc. Tewekel R 32 2/3/2023
  33. 33. In the future, Biochemistry may provide answers for: Obesity solutions/weight reduction A cure for diabetes and many other diseases, more accurate diagnosis, better treatment of infection. Increased life expectancy with slower ageing synthetic organs and tissues for transplant, and a whole array of other potential paths that Biochemistry could take. Tewekel R 33 2/3/2023
  34. 34. 2. Cell and sub cellular Fractionation 34 Tewekel R 2/3/2023
  35. 35. Biochemical studies at different level Stage Examples of study 1. Whole organism Systems: respiration, circulatory etc.. 2. Organ Control /function of an organ 3. Cells Biosynthesis, secretion of proteins... 4. Membrane transport, energy metabolism… 5. Organelle specialised organelle metabolism 6. Cell supernatant Enzyme activity... Tewekel R 35 2/3/2023
  36. 36. Introduction to Cell Cell is the basic functional and structural unit of all forms of life in which different biochemical reactions takes place at mild physiological condition. On the basis of differences in cell structure, all life forms are divided into two major classes. Prokaryotes are simple cells and in most cases, individual cell itself is the organism. They lack membrane bound organelles. Examples for prokaryotes are bacteria, primitive green algae and archae. Eukaryotes: They have membrane bound organelles. They include plants, animals, fungi, protozoa, and true algae. 36 Tewekel R 2/3/2023
  37. 37. Introduction to Cell… The cells of humans and other animals are eukaryotes (eu, good; karyon, nucleus) because the genetic material is organized into a membrane-enclosed nucleus. In contrast, bacteria are prokaryotes (pro, before; karyon, nucleus); they do not contain nuclei or other organelles found in eukaryotic cells. Tewekel R 37 2/3/2023
  38. 38. Eukaryotic cell structure and function A eukaryotic cell is surrounded by a plasma membrane, has a membrane bound nucleus and contains a number of other distinct sub-cellular organelles. In eukaryotes, cells aggregate to form tissues or organs and these are further organized to form whole organism. In humans, eukaryotic cells exist in large number of sizes and shapes to perform varieties of functions. Organelles (such as the nucleus, mitochondria, lysosomes, and peroxisomes) are also surrounded by a membrane system that separates the internal compartment of the organelle from the cytosol. 38 Tewekel R 2/3/2023
  39. 39. The function of these membranes is to collect or concentrate enzymes and other molecules serving a common function into a compartment with a localized environment. Each organelle has different enzymes and carries out different general functions.  For example, Lysosomes contain hydrolytic enzymes that degrade proteins and other large molecules.  The nucleus contains the genetic material and carries out. gene replication and transcription of DNA Tewekel R 39 2/3/2023
  40. 40. Different cell types differ quantitatively in their organelle content, or their organelles may contain vastly different amounts of a particular enzyme, consistent with the function of the cell. For example, liver mitochondria contain a key enzyme for synthesizing ketone bodies, but they lack a key enzyme for their use. The reverse is true in muscle mitochondria. Thus, the enzymic content of the organelles varies somewhat from cell type to cell type. Tewekel R 40 2/3/2023
  41. 41. Fig. Common components of human cells Tewekel R 41 2/3/2023
  42. 42. Cell Membrane(plasma membrane ) The cell membrane is a lipid bilayer that serves as a selective barrier; it restricts the entry and exit of compounds. Envelops the cell, separating it from the external environment; maintaining the correct ionic composition and osmotic pressure of the cytosol. It is impermeable to most substances but within the plasma membrane, different integral proteins facilitate the transport of specific compounds by energy-requiring active transport, facilitated diffusion, or by forming pores or gated-channels. 42 Tewekel R 2/3/2023
  43. 43. Cell membrane is involved in communicating with other cells, in particular through the binding of ligands (small molecules such as hormones, neurotransmitters, etc.) to receptor proteins on its surface. The transporters and receptors in cell membrane control communication of the cell with the surrounding milieu(environment). It is also involved in the exocytosis (secretion) and endocytosis (internalization) of proteins and other macromolecules. E.g. Exocytosis of hormones from endocrine cells; Endocytosis of foreign substance by phagocytic cells. Tewekel R 43 2/3/2023
  44. 44. The selective permeability of cell membrane is responsible for the maintenance of internal environment of the cell and for creating potential difference across the membrane. The variable carbohydrate components of the glycolipids on the cell membrane surface function as cell recognition markers. For example, the A, B, or O blood groups are determined by the carbohydrate composition of the glycolipids. 44 Tewekel R 2/3/2023
  45. 45. Cell membrane surface glycolipids may also serve as binding sites for viruses and bacterial toxins before penetrating the cell. The modification of the cell membrane results in formation of specialized structures like axon of nerves, microvilli of intestinal epithelium and tail of spermatids. Tewekel R 45 2/3/2023
  46. 46. Figure: Basic structure of an animal cell membrane. Tewekel R 46 2/3/2023
  47. 47. Cytoplasm The cytoplasm of the cell is the portion of the cell between the cell membrane and the nucleus. The cytosol is solution part of the cytoplasm not included within any of the subcellular organelles. It is a major site of cellular metabolism like glycolysis , gluconeogenesis, the pentose phosphate pathway and fatty acid synthesis. The cytosol is not a homogeneous ‘soup’ but has within it the cytoskeleton, a network of fibers criss-crossing through the cell that helps to maintain the shape of the cell. 47 Tewekel R 2/3/2023
  48. 48. Cytoskeletons These are filament like structures made up of proteins present in cytoplasm. Non-muscle cells perform mechanical work with these intracellular network of proteins. These cytoskeletons are involved in the maintenance of cell shape, cell division, cell motility, phagocytosis, endocytosis and exocytosis. Microfilaments (8 nm in diameter): Actin polymers form the thin filaments (also called microfilaments). It form a network controlling the shape of the cell and movement of the cell surface, thereby allowing cells to move, divide, engulf particles, and contract. Actin is present in all living cells. 48 Tewekel R 2/3/2023
  49. 49. Microtubules (30 nm in diameter): Microtubules, cylindrical tubes composed of tubulin subunits, are present in all nucleated cells and the platelets in blood. They are responsible for the positioning of organelles in the cell cytoplasm and the movement of vesicles, including phagocytic vesicles, exocytotic vesicles, and the transport vesicle. They also form the spindle apparatus for cell division. Tewekel R 49 2/3/2023
  50. 50. A variety of human cells have cilia and flagella, hair like projections from the surface that have a stroke like motion. These projections contain a flexible organized array of microtubules. Dendrites, axons of nerve cells and sperm cells contain microtubules. The sperm cell moves with the help of flagellum, a microtubule. Intermediate Filaments (10 nm in diameter): Are composed of fibrous protein polymers that provide structural support to membranes of the cells and scaffolding for attachment of other cellular components (e.g., epithelial cells have cytokeratins, and neurons have neurofilaments). These provide an internal network that helps support the shape and resilience of the cell. Tewekel R 50 2/3/2023
  51. 51. Cytoplasmic organelles 1. Mitochondria Mitochondria :has an inner and an outer membrane between which is the inter-membrane space. Are the second largest structures in the cell. Generally mitochondria are ellipsoidal in shape and can assume variety of shapes. The outer membrane contains pores made from proteins called porins and is permeable to molecules with a molecular weight up to about 1000 g/mole. The inner membrane, which is considerably less permeable, has large foldings called cristae which protrude into the central matrix. 51 Tewekel R 2/3/2023
  52. 52. The inner membrane is the site of oxidative phosphorylation and electron transport involved in ATP production. The central matrix is the site of numerous metabolic reactions including the citric acid cycle and fatty acid breakdown. Within the matrix is found the mitochondrial DNA; can reproduce by replicating their DNA and then dividing in half. Although nuclear DNA encodes most of the enzymes found in mitochondria, mitochondrial DNA encodes some of the subunits of the electron transport chain proteins and ATP synthase. Tewekel R 52 2/3/2023
  53. 53. Mutations in mitochondrial DNA result in a number of genetic diseases that affect skeletal muscle, neuronal, and renal tissues. They are implicated in aging. The number of mitochondria ranges from 1-100 per cell depending on type of cell and its function. Several factors influence the size and number of mitochondria in cells. Exposure to cold increases mitochondria by 20-30% in liver cells. In highly metabolically active cells mitochondria are more and large. Location of mitochondria in cell also depends on types and functions of cell. In liver cell mitochondria are scattered. In muscles they are parallely arranged. Tewekel R 53 2/3/2023
  54. 54. Figure: The Structure Mitochondria This organelle processes energy for a cell. It makes ATP. (ATP = energy) Involved in cellular respiration. 54 Tewekel R 2/3/2023
  55. 55. 55 Tewekel R 2/3/2023
  56. 56. 2. Ribosomes Synthesizes proteins/site of translation. Present in the cytoplasm. Present with Rough ER. Consists of protein and rRNA. Ribosome & associated molecules are termed as translational apparatus 56 Tewekel R 2/3/2023
  57. 57. Tewekel R 57 2/3/2023
  58. 58. 3. Peroxisomes Are also small vesicles surrounded by a single membrane. They are also called as micro bodies Contain enzymes that degrade fatty acids and amino acids. A byproduct of these degradation reactions is hydrogen peroxide, which is toxic to the cell. The presence of large amounts of the enzyme catalase in the peroxisomes rapidly converts the toxic hydrogen peroxide into harmless H2O and O2. The enzymes of H2O2 catabolism present in peroxisomes are peroxidase and catalase. 58 Tewekel R 2/3/2023
  59. 59. Figure: Types of reactions in peroxisomes. Tewekel R 59 2/3/2023
  60. 60. Peroxisomes function in the oxidation of very long chain fatty acids (containing 20 or more carbons) to shorter chain fatty acids, the conversion of cholesterol to bile acids, and the synthesis of ether lipids called plasmalogens. Peroxisomal Diseases. Peroxisomal diseases are caused by mutations affecting either the synthesis of functional peroxisomal enzymes or their incorporation into peroxisomes. Zellweger’s syndrome is caused by the failure to complete the synthesis of peroxisomes (read about this syndrome) Tewekel R 60 2/3/2023
  61. 61. 4. Lysosomes Lysosomes are called as ‘Suicide bags’ of the cell, which are found only in animal cells, have a single boundary membrane. The internal pH of these organelles is mildly acidic (pH 4–5), and is maintained by integral membrane proteins which pump H ions into them. The lysosomes contain a range of hydrolases that are optimally active at this acidic pH (and hence are termed acid hydrolases) but which are inactive at the neutral pH of the cytosol and extracellular fluid. 61 Tewekel R 2/3/2023
  62. 62. These enzymes are involved in the degradation of host and foreign macromolecules into their monomeric subunits; proteases degrade proteins, lipases degrade lipids, phosphatases remove phosphate groups from nucleotides and phospholipids, and nucleases degrade DNA and RNA. Lysosomes are involved in the degradation of extracellular macromolecules that have been brought into the cell by endocytosis as well as in the degradation and recycling of normal cellular components. Tewekel R 62 2/3/2023
  63. 63. Figure: Lysosomal reactions Tewekel R 63 2/3/2023
  64. 64. Lysosomal enzymes are involved in bone remodeling and intracellular digestion. Disease, shock or cell death causes rupture of lysosomes and release of enzymes. Lack of one or more of lysosomal enzymes cause accumulation of materials in the cell resulting in lysosomal storage diseases. 64 Tewekel R 2/3/2023
  65. 65. Cytomembranes There is an extensive network of membranes in the cytoplasm. These membranes are called as cytomembranes. They are divided into endoplasmic reticulum and golgi complex or apparatus. The endoplasmic reticulum is further subdivided into rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER). 65 Tewekel R 2/3/2023
  66. 66. Rough Endoplasmic Reticulum It is continuous with outer nuclear membrane. The cytoplasmic surface of rough endoplasmic reticulum is coated with ribosomes. Membrane enclosed channels of endoplasmic reticulam are called cisternae. Functions Ribosomes and RER are involved in protein synthesis. Protein synthesized, enters cisternae and later extruded. . 66 Tewekel R 2/3/2023
  67. 67. Smooth Endoplasmic Reticulum It is continuous with RER. It differs from RER by the absence of ribosomes. When isolated SER is called as microsomes (small vesicles). SER of intestinal cells is involved in formation of triglycerides. In the adrenal cortex, SER is the site of steroid formation. Cytochrome P450 dependent monooxygenases are present in liver cell SER for drugs metabolism. 67 Tewekel R 2/3/2023
  68. 68. 68 Tewekel R 2/3/2023
  69. 69. Golgi Apparatus Golgi apparatus - a system of flattened membrane-bound sacs, is the sorting and processing center of the cell. Membrane vesicles from the RER, containing membrane and secretory proteins, fuse with the Golgi apparatus and release their contents into it. On transit through the Golgi apparatus, further posttranslational modifications to these proteins take place and they are then sorted and packaged into different vesicles. 69 Tewekel R 2/3/2023
  70. 70. These vesicles bud off from the Golgi apparatus and are transported through the cytosol, eventually fusing either with the plasma membrane to release their contents into the extracellular space or with other internal organelles (e.g. lysosomes). Exocytotic vesicles release proteins into the extracellular space after fusion of the vesicular and plasma membranes. Exocytotic vesicles containing hormones also may contain proteases that cleave the prohormone at a specific site. Tewekel R 70 2/3/2023
  71. 71. Golgi Complex The protein packaging and transport center of the cell. Has incoming and outgoing vesicles. Incoming vesicles pick up proteins from RER for post-translational modification. Proteins for different target are leaving the complex by outgoing vesicles. 71 Tewekel R 2/3/2023
  72. 72. Fig. The role of RER and Golgi complex for protein synthesis, post- translational modification and sorting Tewekel R 72 2/3/2023
  73. 73. The digestive enzymes of pancreatic juice and insulin are produced and released in this way. Golgi apparatus helps in the formation of other sub- cellular organelles like lysosomes and peroxisomes. Golgi apparatus is involved in protein targeting. It directs proteins to be incorporated into membranes of other sub- cellular structures. It is also involved in glycosylation and sulfation of proteins. 73 Tewekel R 2/3/2023
  74. 74. Nucleus Centre of the cell is nucleus. It is bounded by two membranes. The two membranes fuse periodically to produce nuclear pores. Exchange of material between nucleus and rest of the cell occurs through nuclear pores. Messenger ribonucleic acid (mRNA), proteins, ribosomes, etc.] can move between the nucleus and the cytosol. 74 Tewekel R 2/3/2023
  75. 75. Nucleus… Other proteins, for example those involved in regulating gene expression, can pass through the pores from the cytosol to the nucleus. The outer nuclear membrane is often continuous with the rough RER. Within the nucleus the DNA is tightly coiled around histone proteins and organized into complexes called chromosomes . Tewekel R 75 2/3/2023
  76. 76. Functions of the nucleus Nucleus is the information centre of eukaryotic cell. More than 90% of the cellular DNA is present in the nucleus. It is mainly concentrated in the form of chromosomes. Human cell contains 46 chromosomes. These chromosomes are composed of nucleoprotein chromatin, which consist of DNA and proteins histones. Some RNA may also present in the nucleus. In prokaryotes, the DNA is present as thread(strand) in the cytosol. 76 Tewekel R 2/3/2023
  77. 77. Figure: The structure of cell nucleus The control center of the cell. It contains the DNA code for the cell coiled into chromosomes. 77 Tewekel R 2/3/2023
  78. 78. 78 Tewekel R 2/3/2023
  79. 79. Nucleolus It is visible under the light microscope ,it is the sub-region of the nucleus which is the site of ribosomal ribonucleic acid (rRNA) synthesis. These are small dense bodies present in the nucleus. Their number varies from cell to cell. There is no membrane surrounding them. They are continuous with nucleoplasm. Nucleoplasm It is also called as nuclear matrix. It contains enzymes involved in the synthesis of DNA and RNA ( enzymes of replication and transcription). 79 Tewekel R 2/3/2023
  80. 80. Summary of major biochemical function of cell organelles Tewekel R Organelles Major functions Cell membrane Transport of molecules in and out of cells Intercellular adhesion and communication Signal transmission Cytoplasm Enzymes of glycolysis Fatty acid synthesis Cholesterol synthesis etc Golgi-apparatus Intra cellular sorting of proteins Glycosylation reactions Sulfation reactions Peroxisomes Degradation of certain fatty acids & amino acids Production & degradation of H2O2 80 2/3/2023
  81. 81. Summary major biochemical function of cell organelles… Organelles Major functions Mitochondria Fatty acids oxidation Citric acid cycle Oxidative phosphorylation/ATP formation etc.. Endoplasmic reticulum (ER) Membrane bound ribosome are a major site of protein synthesis Synthesis of various lipids Metabolism of drugs Nucleus Site of chromosome Transcription… Ribosomes Site of protein synthesis Lysosomes Site of many acid hydrolases (enzymes catalyzing degradative reactions) Tewekel R 81 2/3/2023
  82. 82. Medical and biological importance of cell Cells are mortal i.e., they have finite life span. In the body, cells are formed and destroyed. So, cells are in dynamic state. Cell division and cell death are two opposite processes required to maintain constant tissue volume (tissue homeostasis). Further cell death plays an important role in shaping tissues and organs during development or during recovery from injuries. Cell death may occur due to several external factors . 82 Tewekel R 2/3/2023
  83. 83. There are three types of cell death Necrosis: It is also termed as cell murder. Cells undergo necrotic death if  cell membrane is damaged or  due to decreased oxygen supply and  if energy (ATP) production is blocked. Apoptosis: This type of cell death occurs in tissue turnover. Individual cells or groups of cells undergo this type of death. Aged cells in the body are removed by apoptosis. It is a genetically programmed cell death. In the initial stages of apoptosis, cell shrinks, followed by fragmentation and finally these fragments are eliminated by phagocytosis. 83 Tewekel R 2/3/2023
  84. 84. • Atrophy: This type of cell death occurs in the absence of essential survival factors. Survival factors required by the cell are produced by other cells. Absence of nerve growth factor leads to atrophy of nerves. It is also genetically programmed cell death. Tewekel R 84 2/3/2023
  85. 85. 2/3/2023 85 Tewekel R