* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Slide 1
Survey
Document related concepts
Cell encapsulation wikipedia , lookup
Model lipid bilayer wikipedia , lookup
Membrane potential wikipedia , lookup
Cytoplasmic streaming wikipedia , lookup
SNARE (protein) wikipedia , lookup
Organ-on-a-chip wikipedia , lookup
Signal transduction wikipedia , lookup
Cytokinesis wikipedia , lookup
Cell nucleus wikipedia , lookup
Cell membrane wikipedia , lookup
Transcript
The Cell By Dr Rehab Omer Faculty of Medicine, U of D Definition of Cell A cell is the smallest unit that is capable of performing life functions. Two Types of Cells •Prokaryotic •Eukaryotic Prokaryotes vs Eukaryotes Eukaryotes: A.Have organelles: Organelles are subcellular distinct compartments which have distinct roles. e.g. the nucleus contains the DNA (stored genetic information. Organelles are covered with membranes. B. Larger in size. C. DNA is organized into multiple linear units called chromosomes. D. Plants, fungi and animals are all eukaryotes. Prokaryotes: A. Have no organelles. 1. No nucleus. 2. DNA in cluster (less DNA ). B. Smaller in size. C. DNA is a single circular chromosome. D. Bacteria . Structure: - A typical cell as seen by light microscope has 2 major parts, a nucleus & a cytoplasm. The nucleus is separated from the cytoplasm by a nuclear membrane and the cytoplasm is separated from the surrounding by a cell membrane. Major Subcellular organelles Cell membrane. Nucleus. Mitochondria. Endoplasmic reticulum. Golgi apparatus. Ribosomes (no membrane) Lysosomes. Cell Membrane Made up of lipids & proteins. Selectively permeable, bilayer, allowing some substances to pass excluding others. Lipids are : - phospholipids bilayer such as phosphatidylcholine & phosphatidylethanolamine Head end of the phospholipids molecule contains phosphate portion, which is relatively soluble in water (polar, hydrophilic). The tail is insoluble ( nonpolar, hydrophobic). Proteins: - Uncharged hydrophobic part usually located in the interior of the membrane whereas charged hydrophilic part on the surface. - Proteins carry out functions such as: - Pumps; actively transporting ions across the cell membrane. - Carriers, transporting substances down electrochemical gradients by facilitated diffusion Ion channels, permit passage of ions into and out of the cell when activated. Receptors, bind neurotransmitters and hormones. Enzymes, catalyzing reactions at surface of membrane. Certain glycoproteins create the tight junctions. Nucleus Made up in large part of chromosomes Each chromosome is made up of a giant molecule of DNA. The nuclear envelope is a double membrane structure. Numerous pores occur in the envelope allowing RNA and other chemicals to pass. All DNA is restricted to the nucleus except the mitochondrial and plastid DNA. RNA is formed in the nucleus by coding of the DNA bases. RNA moves out to the cytoplasm. Nucleolus (usually 2 nucleoli per nucleus), don’t have surrounding membrane and are rich in RNA. Mitochondria Sausage-shaped structure, made of outer membrane & inner membrane folded to form shelves ( cristae ). Power generating units of the cell. Outer membrane is studded with enzymes concerned with biologic oxidation for reactions occurring inside mitochondria. Inner membrane and the matrix which it surrounds contain enzymes that convert products of CHO, proteins, fat metabolism to Co2 & water via Citric Acid Cycle and the electron transport chain Their number increases in cells where there is high energy requiring processes Mitochondria have their own genome. There is much less DNA in mitochondrial genome than nuclear genome. Lysosomes Relatively large, irregular structures surrounded by membrane. Interior of these structures is more acidic than the rest of the cytoplasm. These acid hyrolases enzymes allow lysosomes to break down intracellular substances, especially damaged cells and bacteria. Usually, the membrane surrounding the lysosomes prevent the enclosed enzymes from coming in contact with the surrounding substances & therefore prevent their digestive action. What will happen if one of the lysosomal enzymes is congenitally absent? Defective lysosomes lead to one of lysosomal storage diseases. Endoplasmic Reticulum A complex series of tubules. The walls are made up of membranes. Rough: granules attached to the cytoplasmic side of the membrane. Rough ER connects to the nuclear envelope through which mRNA travels to the ribosomes (the site of protein synthesis). Smooth : granules are absent it is the site of lipid synthesis. Ribosomes Sites of protein synthesis. Not membrane-bound. Structurally, consists of a small and larger subunits. Biochemically, consists of ribosomal RNA and structural proteins. Often cluster on the Endoplasmic reticulum or found free in the cytosol. Golgi Apparatus Has membrane similar to the a smooth ER. More prominent in secretory cells and functions in association with ER. Involved in intracellular sorting of proteins, glycosylation and sulfation reactions. Peroxisomes Surrounded by membrane which contains number of specific proteins that are concerned with transport of substances into and out of their matrix. It is important in getting rid of oxygen radicals and has a metabolic role in fatty acids oxidation Cytoskeleton System of fibers that maintains the structure of the cell. Permits the cell to change it’s shape and move. Made up of : 1. Microtubules: provide track for transport of vesicles. 2. Intermediate filaments: some connect the nuclear membrane to cell membrane. 3.Microfilaments: made up of actin, a protein by it’s interaction with myosin brings about contraction of muscle.