Define The cell organelles. Describe the comparison between prokaryotic and eukaryotic cells Determine the types of cell.

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Madeline Wilkins
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2 Define The cell organelles. Describe the comparison between prokaryotic and eukaryotic cells Determine the types of cell. List the types of organelles. Describe the Mitochondrial Inheritance. Nice to know the Mitochondrial diseases. Nice to know the clinical features of the Mitochondrial diseases in this lecture.

3 In cell biology: an organelle is a specialized subunit within a cell that has a specific function, and it is usually separately enclosed within its own lipid bilayer. The name organelle comes from the idea that these structures are to cells what an organ is to the body (hence the name organelle, the suffix - elle being a diminutive). Organelles are identified by microscopy, and can also be purified by cell fractionation. There are many types of organelles, particularly in eukaryotic cells. While prokaryotes do not possess organelles.

4 The prokaryotic cell is a simple cell. It has no nucleus, and no membrane-bound organelles. The genetic material of a prokaryotic cell is found in a region of the cell known as the nucleoid. Bacteria are a fine example of prokaryotic cells and divide by a process known as binary fission; they duplicate their genetic material, divide in half, and produce two identical daughter cells. The eukaryotic cell is much more complex. It contains a nucleus, which functions as the control center of the cell, directing DNA replication, transcription, and cell growth. Eukaryotic organisms may be unicellular or multicellular. One of the key features of eukaryotic cells is the presence of membranebound organelles, each with its own duties.

5 Eukaryotes Prokaryotes protists, fungi, plants, animals bacteria, archaea Typical organisms ~ µm [10] ~ 1 5 µm [10] Typical size true nucleus with double membrane nucleoid region; no true nucleus Type of nucleus linear molecules (chromosomes) with histone proteins circular (usually) DNA

6 60S and 40S highly structured by endomembranes and a cytoskeleton flagella and cilia containing microtubules; lamellipodia &filopodia containing actin one to several thousand (though some lack mitochondria) in algae and plants single cells, colonies, higher multicellular organisms with specialized cells Mitosis (fission or budding) Meiosis 50S and 30S very few structures flagella made of flagellin none none usually single cells Binary fission (simple division) Ribosomes Cytoplasmic structure Cell movement Mitochondria Chloroplasts Organization Cell division

7 Prokaryotic Organelles: Plasma membrane: 1- This is a selective barrier around a cell composed of a double layer of phospholipids. 2- Part of this selectivity is due to the many proteins that either rest on the exterior of the membrane or are embedded in the membrane of the cell. 3- Each membrane has a different combination of lipids, proteins, and carbohydrates that provide it with its unique characteristics.

8 Cell wall: This is a wall or barrier that functions to shape and protect cells. This is present in all prokaryotes. Ribosomes: These function as the host organelle for protein synthesis in the cell. They are found in the cytoplasm of cells and are composed of a large unit and a small subunit.

10 Eukaryotic Organelles: Ribosomes: 1) As in prokaryotes, eukaryotic. 2) ribosomes serve as the host organelle for protein synthesis. 3) Eukaryotes have bound ribosomes, which are attached to endoplasmic reticula and form proteins that tend to be exported from the cell or sent to the membrane. 4) There are also free ribosomes, which exist freely in the cytoplasm and produce proteins that remain in the cytoplasm of the cell. 5) Eukaryotic ribosomes are built in a structure called the nucleolus.

11 Prokaryotic ribosomes Eukaryotic ribosomes

12 Smooth endoplasmic reticulum: This is a membrane-bound organelle involved in lipid synthesis, detoxification, and carbohydrate metabolism. Liver cells contain a lot of smooth endoplasmic reticulum (SER) because they host a lot of carbohydrate metabolism (glycolysis). The liver contains much SER for another reason it is the site of alcohol detoxification. It is given the name "smooth" endoplasmic reticulum because there are no ribosomes on its cytoplasmic surface.

14 Rough endoplasmic reticulum: This membranebound organelle is termed "rough" because of the presence of ribosomes on the cytoplasmic surface of the cell. The proteins produced by this organelle are often secreted by the cell and carried by vesicles to the Golgi apparatus for further modification. Golgi apparatus: Proteins, lipids, and other macromolecules are sent to the Golgi to be modified by the addition of sugars and other molecules to form glycoproteins. The products are then sent in vesicles to other parts of the cell, directed by the particular changes made by the Golgi, in other words: storage & packaging of materials that will be exported from the cell.

15 Rough endoplasmic reticulum Golgi apparatus

16 Nucleus: This is the control center of the cell. In eukaryotic cells, this is the storage site of genetic material (DNA). It is the site of replication, transcription, and posttranscriptional modification of RNA. It also contains the nucleolus, the site of ribosome synthesis. Vacuole: This is a storage organelle that acts as a vault. Vacuoles are quite large in plant cells but small in animal cells.

17 Nucleus Vacuole

18 Chloroplast: This is the site of photosynthesis and energy production in plant cells. Chloroplasts contain many pigments, which provide leaves with their color. Chloroplasts are divided into inner portion and outer portion. The inner fluid portion is called the stroma, which is surrounded by two outer membranes. Winding through the stroma is an inner membrane called the thylakoid membrane system, where the light-dependent reactions of photosynthesis occur. The light-independent (dark) reactions occur in the stroma. Cytoskeleton:The skeleton of cells consists of three types of fibers that provide support, shape, and mobility to cells: microtubules, microfilaments, and intermediate filaments. - Microtubules are constructed from tubulin and have a lead role in the separation of cells during cell division. Microtubules are also important components of cilia and flagella, which are structures that aid the movement of particles. - Microfilaments, constructed from actin, play a big part in muscular contraction. - Intermediate filaments are constructed from a class of proteins called keratins and are thought to function as reinforcement for the shape and position of organelles in the cell.

19 Chloroplast Cytoskeleton

20 Peroxisomes: 1-are single-membrane structures found in all eukaryotic cells. They are small, membrane-bound structures that use molecular oxygen to oxidize organic molecules. 2-These are organelles containing enzymes that produce hydrogen peroxide as a byproduct while performing various functions, such as breakdown of fatty acids and detoxification of alcohol in the liver. 3-Peroxisomes also contain an enzyme that converts the toxic hydrogen peroxide byproduct of these reactions into cell-friendly water.

22 are special types of vacuoles. contain enzymes for use in the hydrolytic breakdown of macromolecules. Three ways to enter a lysosome phagocytosis, autophagy, and receptormediated endocytosis.

24 Found in ALL eukaryotic cells (even in plant cells) Site of aerobic respiration sugars + O > ATP + CO 2 + H 2 O So it called powerhouse of the cell Contain DNA which codes for mitochondrial proteins, ribosomes, etc. Divide by a process similar to binary fission when cell divides. Enclosed in a double membrane system. Inner Membrane forms the Cristae (invaginations into interior region) Site of energy generation Matrix is the soluble portion of the mitochondria Site of carbon metabolism Location of mdna Site of mitochondrial protein synthesis

26 Mammalian cells contain mitochondria which have their own circular deoxyribonucleic acid (mtdna). Mitochondria are only passed on in the cytoplasm of the egg so that a child inherits all its mitochondria from its mother. There are some diseases that are some diseases that are associated with mutations in mitochondrial DNA. A woman with such a mutation will therefore pass it on to all her children whilst a man with the same mutation will not pass it on to any of his children. There is often a wide range of severity of disease in carriers of mitochondrial mutations. Mitochondrial inheritance is characterized by: 1-Maternal transmission only. 2-Extreme variability in the same family.

27 The genetics of mtdna differ from that of DNA in the following unique properties: 1-The mitochondrial genome is maternally inherited: The mother transmits her oocyte mtdna to all of her offspring & her daughters transmit their mtdna to the next generation. This is due to the fact that during fertilization. The few mitochondria from the sperm that enter the egg are rapidly eliminated through unknown mechanism. 2-Mitochondria are polypoid: Each human cell has hundreds of mitochondria each containing 2-10 mtdna molecules. At cell division mitochondria and their genomes are randomly distributed to daughter cells.

28 3-The mitochondrial genome has a much faster evolution rate than the nuclear genome: The average number of base pair difference between two human mitochondrial genomes is estimated to be from 9.5 to 66. This explained by the fact that, although the mitochondrial gamma-dna polymerase may retain a proofreading activity X certain types of repair enzymes have been identified in mitochondrial fractions. Mitochondria lack an efficient DNA repair system, based, for instance, on homologous recombination or removal of pyrimidine dimmers. In addition, the mitochondrial genome lacks protective proteins like histones, and is physically associated with the inner mitochondrial membrane, where highly mutagenic oxygen radicals are generated as byproducts of OXPHOS.

29 Normally, the mitochondrial genotype of an individual is composed of a single mtdna species: A condition known as homoplasmy. However, the intrinsic propensity of mtdna to mutate randomly can occasionally determine a transitory condition known as heteroplasmy, where the wild-type & the mutant genomes co-exist intracellular.

30 Assorted myopathies and neuropathies observed clinically in recent years: neurologic disorders ragged red fibers in muscle biopsies weakness exacerbated by exercise seizures (muscle jumps) dementia with early onsetmovement disorders stroke-like symptoms retinopathy hearing loss partial blindness migraine headaches

31 Combined oxidative phosphorylation deficiency 5.

33 .

Cell (Learning Objectives)

Cell (Learning Objectives) 1. Understand & describe the basic components necessary for a functional cell. 2. Review the order of appearance of cells on earth and explain the endosymbiotic theory. 3. Compare