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Transcript
Cell Organelles of a Eukaryotic Cell Prokaryotic Cells vs. Eukaryotic Cells • Prokaryotic Cells – Much smaller and simpler than eukaryotic cells – Size less than 10 micrometers – Thought to be first living life forms on Earth – Bacteria cells – Structures • Cell wall • The plasma membrane • Flagella • Ribosomes • Nucleoid region (but NO NUCLEUS!) • No Mitochondria • I. Plasma Membrane II. Mesosome III. Cell Wall E. coli Bacteria Definition of an Organelle contained in Eukaryotic Cells • Non-cellular structures that carry out specific functions (a bit like organs in a multi-cellular organism) – These structures bring about compartmentalization in eukaryotic cells which allows for chemical reactions to be separated and for specific reactions to be isolated which increases efficiency in a cell • Different types of cells have different organelles • Definitions found on IB External exam questions for the term “organelle”: – Sub-cellular structures – Discrete structures found inside all cells that have specific function. Cytoplasm • Cytoplasm is not specifically listed as an “organelle” that you need to know, however, in other literature I have seen it included • Book Definition: Contains dissolved substances, enzymes, and the cell organelles • Test Questions I found about it pertained to: – The process of Translation occurs here – Glycolysis, which is the beginning stage of cellular respiration occurs here • Glucose here is broken into pyruvate to release energy for use in a cell Free Ribosomes • Definition (From Exam)- Small spherical structures, consisting of two subunits. • Structure/Function: Ribosomes are the workbenches where proteins get manufactured. A ribosome is a large molecular complex (organelle), composed of several proteins and ribonucleic acid that reads messenger RNA and thereby synthesizes proteins. • Contents: Large and Small subunits in Eukaryotic cells. • Characteristics- All cells, including Archaea and bacteria have ribosomes. Free vs. Attached: Ribosomes • They occur both as free particles within cells and, in eukaryotes, as particles attached to the membranes of the endoplasmic reticulum. Prokaryotic vs. Smaller size (70S) Eukaryotic cells Larger size (80S) Endoplasmic Reticulum (ER) • Functions - Smooth ER –Lipid synthesis and transportation - Rough ER –Protein transportation and processing • Structure Lysosome • Function: Lysosomes are the cell's garbage disposal system. Lysosomes digest excess or worn-out organelles, food particles, and engulfed viruses or bacteria. • Contents: Contain enzymes created by the cell that are used to digest. • Structure: Like rounded material with sacs inside Golgi Apparatus • Found in: Most eukaryotic cells • Function: The primary function of the Golgi apparatus is to process and package macromolecules, such as proteins and lipids. The Golgi apparatus modifies, sorts, and packages these macromolecules for cell secretion. • Structure: The Golgi is composed of stacks of membrane-bound structure. Mitochondrion • • • Definition: Organelles surrounded by two membranes, the inner of which is folded inwards. Function Example: -Cell respiration Structure Features Related to Function: - The mitochondrion is bounded by a double membrane; inner membrane has infoldings (cristae). The cristae greatly increases the surface area which allows the membranes to carry out their primary functions. Mitochondria is protected by two membranes and the inner membrane surrounds the cristae. • Has similarities to prokaryotic cells. Mitochondrion(cont.) • Structures on electron micrograph IB Micrograph of Mitochondria A. B. 1. Annotate similarities in structure 2. State Visible Differences other than size 3. Predict which could produce ATP at a greater rate The electron micrographs below show mitochondria in longitudinal section. The mitochondrion in A is from a bat pancreas cell and that in B is from a mouse liver cell. Answers to Questions on last slide (a)both have two (outer) membranes; both have cristae; both have a matrix (with a grainy appearance) / ribosomes; 2 max (b)shape; arrangement of cristae; density of cristae; amount of matrix granules / any reference to dark dots; (do not accept ribosomes)2 max (c)A / bat’s;larger size / volume; greater surface area of cristae / more cristae;closeness of mitochondria in B mouse reduces rate;3 max Mitochondrion(cont.) • What is contained in the inner membrane of the mitochondrion? – Electron transport chain – Crista • Internal pockets formed to help proteins operate efficiently – Many proteins • These include transport proteins that transport metabolites across the inner membrane Nucleus IB DEFINITION: Region of the cell containing chromosomes, surrounded by a double membrane, in which there are pores. Provides for storage and protection of chromosomes Note: nucleus is only present in membranebound cells • Structure Nucleus Endoplasmic Reticulum allows nutrients to flow in and out of nucleus along with RNA strands to control activities. Nucleus Cell Wall • Function: A cell wall is a tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. • Structure: It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to act as a pressure vessel, preventing over-expansion when water enters the cell. • They are found in plants, bacteria, fungi, and algae. Animals and protozoa do not have cell walls. Cell Chloroplast Chlorophyll in the Chloroplast • • The function of the majority of the chlorophyll is to absorb and transfer light energy by resonance energy transfer to the reaction center of the photosystems to a specific chlorophyll pair. The reaction chlorophyll pair then takes the light energy transferred to them from the other chlorophyll pigments and undergoes a charge separation where the chlorophyll gives up an electron into a electron transport chain. The electron flow produced by the reaction center chlorophyll pairs is used mainly to produce ATP chemical energy . The structure of chlorophyll: Wavelengths of How much – There are two parts to the chlorophyll, light absorbed (nm) the head and the tail. The head consists of a porphyrin ring or nucleus, from Red 650 which extends a tail made up of a 20Some orange 590 carbon grouping called the phytol Some yellow 570 Why do plants appear green? - Because the chlorophyll absorbs all the Blue 475 wavelengths of the sunlight except green, so Indigo 445 that is the color that reflects on our eyes. Violet 400 General IB Questions on Organelles Capillary I (a)Identify the structures labeled I, II and III in the micrograph above and give a role for each one. Structure Storage vesicles II Role A. B. C. D. (b)(i)Using the letter A, identify one location on the micrograph where transcription takes place. III (ii)Using the letter B, identify one location on the micrograph where chemiosmosis occurs. See next slide for answers! Answers to questions on last slide Structure (i) (ii) I: mitochondria II: nucleus III: (rough) endoplasmic reticulum Role produce ATP / site of (aerobic) respiration; contains genetic information / produces RNA / site of replication; (site of) translation / protein production / protein transport; A in nucleus / A in mitochondria B in a mitochondrion 1 1 General IB Questions on Organelles The electron micrograph below shows part of a cell . 1. Identify the structures labeled I and II. 2. Deduce, with a reason, whether this cell is eukaryotic or prokaryotic. Answers: I: membrane / (nuclear) envelope; II: mitochondrion / mitochondria; Answers: eukaryotic, internal membranes / membrane bound organelles / presence of mitochondria / double nuclear membrane;