cell nucleus mitochondria chloroplast structure and function
- 1. D. Asma Saleh Alilesh Biotechnology department / Misurata university Cell nucleus
- 2. The nucleoid Meaning nucleus-like Is an irregularly-shaped region within the cell of a prokaryote that contains all or most of the genetic material. It is not surrounded by a nuclear membrane. Nucleoid is composed of: 1- DNA: forms 60% of the nucleoid, found as circular double stranded chromosome. The chromosome is supercoiled. 2- Proteins: bind to DNA ( DNA binding protein), some of them: transcription factor and nucleoid associated protein (NAPs) which regulate folding process of DNA 3- Enzymes: enzymes that catalyze duplication and transcription process
- 4. Nucleus is a membrane -enclosed organelle that contains most of the cell's genetic material in eukaryotic cell. Is an irregular-shaped Nucleus is composed of: 1. nuclear envelope 2. nucleolus 3. Chromatin and chromosomes 4. nuclear matrix 5. nucleoplasm
- 6. 1- nuclear envelope Separation of a cell’s genetic material from the surrounding cytoplasm. Consists of two cellular membranes arranged parallel to one another and separated by10 to 50 nm. The two membranes are fused at sites forming circular pores. The outer membrane is generally studded with ribosomes and is continuous with the membrane of the rough endoplasmic reticulum. The inner membrane of animal cells is bound by integral membrane proteins to nuclear lamina
- 7. Nuclear lamina: a thin (10nm) filamentous meshwork composed of polypeptides called lamins.
- 8. nuclear lamina provide mechanical support to the nuclear envelope. And serves as a site of attachment for chromatin fibers at the nuclear periphery. regulated by phosphorylation and dephosphorylation. The disassembly of the nuclear lamina in mitosis induced by phosphorylation of the lamins. Mutation in one of lamins genes are responsible for several distinct human disease including rare form of muscular dystrophy and Hutchinson Gilford progeria syndrome (HGPS)
- 10. nuclear envelope pore have high activity for the monement of RNA and protein between the nucleus and cytoplasm Nuclear pores contain complex, basket like apparatus called nuclear pore complex (NPC) NPC contain about 30 different proteins called nucleoporins prtein destined for the nucleus must contain a nuclear localization signal or sequence (NLS ) NLS is amino acid sequence that tag a proteins for import into nucleus by nuclear transport, this signal consists of short sequence of positively charged lysines or arginines.
- 12. 2- chromosome and chromatin Somatic human cell contains 2m DNA in nucleus which only 10µm . DNA in eukaryotic cell coiled and packaged around proteins called histones. The packaging of DNA have several levels: - nucleosome - 10 nm nucleosome filament - 30 nm chromatin fiber - 300 nm chromatin fiber - 700 nm chromatid - Chromosome (mitotic form)
- 14. chromosome Single continuous DNA fragment , packaged in different levels and appears as X shape during mitosis. Somatic human cell contain 46 chromosomes.
- 16. 3- Nuclear matrix: part of nucleus that consists of insoluble fiber forms network. -acts as skeleton maintain the shape of the nucleus -scaffold to organize loops of chromatin - Much of proteins that involved in transcription and replication anchor to it 4- Nucleoplasm: liquid part that fill the nucleus , it contains dissolved materials . 5- Nucleolus: - is the largest structure in the nucleus of eukaryotic cells, - Nucleoli are made of proteins, DNA and RNA serves as the site of ribosome synthesis and ribosomal RNA (rRNA). - The nucleolus of several plant species has very high concentrations of iron and vacules in contrast to the human and animal cell nucleolus. - some cells from other species often have multiple nucleoli.
- 17. It is assembled at the end of mitosis around arrays of ribosomal DNA genes, forming specific chromosomal features known as nucleolar organizing regions (NORs) which are the sites of ribosomal DNA transcription. The primary function of the nucleolus consists in ribosomal RNA (rRNA) transcription, rRNA processing and ribosome subunit assembly. All active nucleoli contain at least two ultrastructural components, the nucleolar dense fibrillar component representing early pre-ribosomal complexes and the granular component containing more mature pre-ribosomal particles. Most nucleoli in higher eukaryotes also contain fibrillar centres, which are the interphase equivalents of the nucleolus organiser regions.
- 19. The nucleolus has numerous other functions including modification of transfer RNAs and sensing cellular stress.
- 21. , Mitochondrion
- 22. Mitochondrion Double membrane organelle found in most eukaryotic cells Mitochondria are small, often between 0.75 and 3 micrometers and are not visible under the microscope unless they are stained. Mitochondria can appear as individual, bean-shaped organelles ranging from 1 to 4 µm in length. The number of mitochondria in a cell can vary widely by organism, tissue, and cell type. For instance, red blood cells have no mitochondria, whereas liver tissue can have more than 2000. Mitochondria can appear as a highly branched or tubular network. Dynamic organelles capable to fuse with one another, or split in two
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- 25. Structure of mitochondria 1. outer mitochondrial membrane 2. inner mitochondrial membrane 3. intermembrane space 4. matrix
- 27. 1- Outer mitochondrial membrane Encloses the entire organelle. The outer membrane is composed of approximately 50 % lipid by weight and contains mixture of enzymes involved in diverse activities as the degradation of tryptophan, and the elongation of fatty acids. The outer mitochondrial membrane contain porins( integral proteins that have a relatively large internal channel surrounded by a barrel of β strands). The outer membrane is permeable to molecules such as ATP, NAD, and coenzyme A.
- 28. membrane The inner mitochondrial membrane is folded to form invaginated membranous sheets, called cristae. The cristae contain a large amount of membrane surface, which houses the machinery needed for aerobic respiration and ATP formation. has a very high protein/lipid ratio (more than 3/1 by weight, which corresponds to about one protein molecule for every 15 phospholipids).These protein includes: electron transport protein , ATP synthase and Transport protein the inner membrane doesn't contain porins, and is highly impermeable to all molecules. The inner membrane is virtually devoid of cholesterol and rich in an unusual phospholipid, cardiolipin (diphosphatidylglycerol) Cardiolipin plays an important
- 29. ATP synthase The ATP-synthesizing enzyme, which is called ATP synthase, is a mushroom-shaped protein complex composed of two principal components: a spherical F1 head (about 90 Å diameter) and a basal section, called F0
- 30. 3- Intermembrane space Is the region between the inner membrane and the outer membrane IMS chemically equivalent to the cytosol regarding the small molecules it contains. intermembrane space plays a pivotal role in the coordination of mitochondrial activities with other cellular processes. These activities include the exchange of proteins, lipids, or metal ions between the matrix and the cytosol, the regulated initiation of apoptotic cascades.
- 31. The matrix is the space enclosed by the inner membrane consists of gel like materials. Matrix contains : enzymes, ribosomes and several molecules of DNA. Human mitochondrial DNA contains 37 genes encode for 13 mitochondrial polypeptides , 2 ribosomal RNAs and 22 tRNAs that are used in protein synthesis within the organelle. Mitochondrial DNA (mtDNA) has many special features such as a high copy number in cell, maternal inheritance, and a high mutation rate . 4- Matrix
- 33. The N-terminal signal sequence of the precursor protein is recognized by receptors of the TOM complex. The protein is thought to be translocated across both mitochondrial membranes at or near special contact sites. The signal sequence is cleaved off by a signal peptidase in the matrix to form the mature protein.
- 34. Mitochondria function Synthesis of ATP through cellular respiration. Regulate metabolism through regulation of Ca+2 concentration. Involved in programmed cell death.
- 35. Chloroplast
- 36. Chloroplast double-membrane organelles found in photoautotrophic eukaryotic cells. Chloroplasts of higher plants are generally lens- shaped approximately 2 to 4 µm wide and 5 to 10 µm long, and typically numbering 20 to 40 per cell. chloroplasts are larger and more complex than mitochondria. Locate near the cell wall and move with the movement of cytoplasm. Consists of : 1. envelope 2. internal membrane system
- 38. Envelope Composed of two membranes separated by a narrow space. 1. Outer membrane: is bilayer of phospholipids like outer membrane of mitochondria, contains porins and permeable to most ions and metabolites. 2. Intermembrane space: is extremely small, somewhere from 10-20 nm thick, have no function. 3. Inner membrane: -borders the stroma and regulates passage of materials in and out of the chloroplast. - impermeable. - the inner chloroplast membrane is where fatty acids, lipids, and carotenoids are synthesized
- 39. internal membrane system Consists of flattened membranous sacs called thylakoids The space inside a thylakoid sac is the lumen where the photosynthesis happens In the surface of thylakoid there are: - chlorophyll molecules - accessory pigments - enzymes - electron transport system • Membrane of thylakoid consists of high ratio of proteins and low phospholipids, instead of them they have glycolipids. And highly fluid. • Thylakoid arranged to form grana. • Grana connected by membranous structure called
- 40. . and the space outside the thylakoid and within the chloroplast envelope is the stroma, which contains the enzymes responsible for carbohydrate synthesis. chloroplast electron transport system is located in the thylakoid membrane, and protons are pumped across this membrane from the stroma to the thylakoid lumen. The resulting electrochemical gradient then drives ATP synthesis. the stroma of a chloroplast contains also: chloroplast genome, ribosomes, starch granules and lipid droplets.
- 41. Chloroplast genome The genomes of chloroplasts are similar to those of mitochondria in that they consist of circular DNA molecules present in multiple copies per organelle, chloroplast genomes 120 to 160 kb and containing approximately 200 genes. Chloroplast DNA contains between about 60 and 200 genes involved in either gene expression (e.g., tRNAs, rRNAs, ribosomal proteins) or photosynthesis. The vast majority of the estimated 2000–3500 polypeptides of a plant chloroplast are encoded by the DNA of the nucleus and synthesized in the cytosol.
- 42. Function Number of genes Genes for the genetic apparatus rRNAs (23S, 16S, 5S, 4.5S) 4 tRNAs 30 Ribosomal proteins 21 RNA polymerase subunits 4 Genes for photosynthesis Photosystem I 5 Photosystem II 12 Cytochrome bf complex 4 ATP synthase 6 Genes Encoded by Chloroplast DNA
- 44. they perform several critical tasks in addition to the generation of ATP. Most importantly, chloroplasts are responsible for the photosynthetic conversion of CO2 to carbohydrates. In addition, chloroplasts synthesize amino acids, fatty acids, and the lipid components of their own membranes. The reduction of nitrite (NO2 -) to ammonia (NH3), an essential step in the incorporation of nitrogen into organic compounds, also occurs in chloroplasts.
- 45. Chloroplasts play a central role in plant immunity through the synthesis of secondary metabolites and defense compounds, as well as phytohormones, such as jasmonic acid and salicylic acid. Additionally, chloroplast metabolism results in the production of reactive oxygen species and nitric oxide as defense molecules.