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Transcript
CELL ORGANELLES Structures and Functions PLASMA MEMBRANE PLASMA MEMBRANE STRUCTURE • • • • Phospholipid bilayer Embedded proteins Proteins on surface Cholesterol molecules within PLASMA MEMBRANE FUNCTIONS • Boundary layer for the cell and certain organelles • “Gatekeeper:” allows only certain molecules in or out if they are small • Covers cell / keeps it different from the environment MEMBRANE LOCATIONS • Cell Membrane • Plastids – Vacuoles • Golgi Bodies • Endoplasmic Reticulum • Mitochondria • Nucleus CYTOPLASM FUNCTIONS: • Holds organellles in place, not too tightly • Site of most cellular chemical reactions (metabolism) • Gives shape to animal cells CYTOPLASM STRUCTURE • “Chemical Soup”—Made of water (70%) with many different dissolved solutes such as fats, minerals, carbohydrates, proteins, RNA • Gel-like—Not quite as solid as jello, but more viscous than water RIBOSOMES • Made of 2 “balls” of RNA and protein stuck together • Numerous—may be .5 million per cell • Attached to rough ER or floating in cytoplasm • No membrane (Are they in prokaryotic cells then?) FUNCTION OF RIBOSOMES • Site of Protein Synthesis • Strings the amino acids together ENDOPLASMIC RETICULUM • Tube-like, branched “canal system” throughout the cell • Continuous from nucleus to cell membrane • Half of plasma membrane of cell is in ER • Lumen: hollow portion inside FUNCTION OF ENDOPLASMIC RETICULUM • Transports newly made proteins to other parts of the cell, or even out of the cell • Divides the cytoplasm into reaction areas • As it grows, it pushes out and inward to form the cell / nuclear membrane ROUGH ENDOPLASMIC RETICULUM • Has ribosomes attached • Membrane in “sheets” or flattened sacs SMOOTH ENDOPLASMIC RETICULUM • Mesh of interconnecting tubules smaller than rough ER 13 13 GOLGI APPARATUS • Like a stack of hollow pancakes • Cisternae (“pancakes”) are slightly curved • Vesicles come off ends • Abundant in cells that secrete proteins (like pancreas cells) FUNCTION OF GOLGI APPARATUS • Modify and package cell products, like proteins • Vesicles transport newly made proteins MITOCHONDRIA • Kidney bean shaped • Double membrane: inner is bigger than outer, so has many folds (cristae) • Matrix full of fluid • Numerous in cells that require lots of energy FUNCTION OF MITOCHONDRIA • Powerhouse of the cell • Site of cellular respiration—glucose is broken down to release energy as ATP for cellular work • Provides energy for cell • Can reproduce themselves Contain own DNA and ribosomes (An early cell?) NUCLEUS • Surrounded by a nuclear membrane (“skull”) that has pores . Membrane is double. • Filled with gel-like nucleoplasm NUCLEUS Contains: • Nucleolus– a dense area of RNA where ribosomes are made • Chromatin-- DNA (genes) and protein “Brain:” has recipe for protein production CHROMATIN IN NUCLEUS • Chromatin is coiled and packaged to fit inside the nucleus FUNCTION OF NUCLEUS • Controls cell activities • Keeps DNA out of the cytoplasm, but allows RNA to move through the nuclear pores and ribosomes • Cell reproduction starts here • Protein synthesis starts here: message from DNA to ribosomes CELL WALL In plant cells only • Cellulose fibers • criss-crossed to form a rigid box-like structure • Thick and porous • Outside the cell membrane • Also found in fungi, bacteria, some Protista FUNCTION OF CELL WALL • Supports and gives shape to plant cells • Protects plant cells from rupture • Acts as fiber for animals who eat cellulose in cell wall VACUOLES • Come and go in animal cells—also smaller and more numerous • Larger, less mobile in plant cells—permanent, too • Filled with water and solutes • Plasma membrane on outside FUNCTION OF VACUOLES • Store food, waste, water, pigments, toxins, et cetera • Creates turger pressure PLASTIDS • Found in plant cells, some Protista, some Monera (blue-green algae) • Types: Chloroplasts Chromoplasts Amyloplasts CHLOROPLASTS • Outer membrane bag filled with little stacks of other sacs containing chlorophyll, a green molecule • Site of photosynthesis (CO2 + H2O made into glucose using energy from sun) • Has own DNA AMYLOPLASTS • Filled with starch instead of chlorophyll • Clear • Store energy for the cell Potato amyloplast CHROMOPLASTS • Have yellow or orange pigments instead of chlorophyll • Give color to leaves or vegetables-squash, sweet potatoes, fall leaves VESICLES • Lysosome: responsible for degrading proteins and membranes in cell, and materials ingested by cell • Peroxisome: produces and degrades hydrogen peroxide, a toxic compound produced during metabolism Centriole a small organelle near the nucleus of animal cells only used in cellular reproduction • This has been brought to you by the cell which would not be where it is today without its organelles!