Cells that specialize in protein secretion pancreas frequently have high proportions of bound membranes What role do ribosomes play in carrying out genetic instruction Ribosomes in the cytoplasm translate the genetic message carried from DNA in the nucleus by MRNA into a polypeptide chain Describe the molecular composition of the nucleoli and explain their function Nucleoli consist of DNA and rRNA made according to its instructions as well as protein from the cytoplasm Together the rRNA and proteins are assembled into large and small ribosomal subunits As the cell begins the process of dividing its chromatin becomes more and more condensed Does the number of chromosomes change during this process Explain No Each chromosome is present whether its chromatin is relatively diffuse or condensed The Endomembrane system regulates protein traffic and performs metabolic functions in the cell Endomembrane system includes nuclear envelope endoplasmic reticulum golgi apparatus lysosomes various kinds of vesicles vacuoles and the plasma membrane o This system carries out synthesis of proteins o Transport of proteins o Metabolism and movement of lipids o Detoxification of poisons Vesicles sacs made of membrane Endoplasmic reticulum within the cytoplasm o little net o a network of membranous tubules and sacs called cisternae o the ER membrane separates the internal compartment of the ER called the ER lumen from the cytosol b c the ER membrane is continuous with the nuclear envelope the space between the two membranes is continuous with the lumen of the ER Smooth ER lack ribosomes Synthesis of lipids Metabolism of carbohydrates Detoxification of drugs and poisons Enzymes of the smooth ER are important in the Storage of calcium ions synthesis of lipids Other enzymes of the smooth ER help to detoxify drugs and poisons esp in the liver o in muscle cells the smooth ER membrane pumps calcium ions from the cytosol and into the ER lumen o When a muscle cell is stimulated by a nerve impulse calcium ions rush back across the ER membrane and into the cytosol triggering contraction of the muscle cell Rough ER studded with ribosomes on the outer surface of the membrane Many types of cells secrete proteins produced by ribosomes attached to the rough ER As a polypeptide chain grows from a bound ribosome he chain is threaded into the ER lumen through a pore formed by a protein complex in the ER membrane As the new polypeptide enters the ER lumen it folds into its native shape Glycoproteins proteins that have carbohydrates covalently bonded to them The carbohydrates are attached to the proteins in the ER built by enzymes built into the ER membrane Golgi Apparatus manufactures some macromolecules Cisternal maturation model the cisternae of the Golgi Apparatus actually progress forward from the CIS to the TRANS face modifying the cargo as they move Lysosome membranous sac of hydrolytic enzymes that an animal cell uses to digest or hydrolyze Lysosomes are an acidic environment o Therefore excessive leakage can destroy the cell Hydrolytic enzymes and lysosome membrane are made by the rough ER and then transferred to the Golgi for further processing Phagocytosis food vacuole fuses with a lysosome whose enzymes digest the food Transport Vesicles vesicles in transit from one part of the cell to another Rough ER grows in place by adding membrane proteins and phospholipids to its own membrane As polypeptides grow from the ribosomes they are inserted into the ER membrane and anchored by their hydrophobic portions Golgi Apparatus products of the ER such as proteins are modified stored and then sent to other destinations consists of flattened membranous sacs cisternae Two sides of the Golgi CIS and TRANS faces o These act respectively as the receiving and shipping departments of the Golgi Apparatus CIS face is near the ER Transport vesicles move material from the ER to the Golgi apparatus TRANS face gives rise to the vesicles that pinch off and travel to other sites Lysosomes use their hydrolytic enzymes to recycle the cell s own organic material autophagy During autophagy a damaged organelle or small amount of cytosol becomes surrounded by a double membrane and a lysosome fuses with the outer membrane of the vesicle The lysosomal enzymes dismantle the enclosed material and the organic monomers are returned to the cytosol for reuse o People w lysosomal storage diseases lack a functioning hydrolytic enzyme normally present in lysosomes Vacuoles are large vesicles derived from the endoplasmic reticulum and the Golgi Apparatus Food Vacuoles formed by phagocytosis Contractile vacuoles pump excess water out of the cell maintaining suitable concentration of ions and molecules inside Central vacuole develops by the coalescence o Cell sap the plant cell s main respitory of inorganic ions Describe how structural vesicles integrate the endomembrane system Transport vesicles move membranes and substances they enclose between other components of the endomembrane system Mitochondria and Chloroplasts change energy from one form to another Mitochondria site of cellular resp Chloroplasts found in plants and algae the sites of photosynthesis o Convert solar energy into chemical energy by absorbing sunlight and using it to drive the synthesis of organic compounds Evolutionary origins of mitochondria and chloroplasts Endosymbiont theory a cell living within another cell states that an early ancestor of Eukaryotic cells engulfed an oxygen using non photosynthetic prokaryotic cell Mitochondria and typical chloroplasts have two membranes surrounding them o they both contain ribosomes as well as DNA attached to their inner membranes Mitochondria Chemical Energy Conversion found in plants animals fungi and most protists the of mitochondria correlates with the cell s level of metabolic ativity two membranes o outer membrane is smooth o inner membrane is convoluted intermembrane space narrow region between inner and outer membranes mitochondrial matrix enclosed by inner membrane Chloroplasts Capture of Light Energy contain chlorophyll enzymes and other molecules that function in the photosynthetic production of sugar o contains thylakoids flattened interconnected sacs each stack is called a granum fluid inside called stroma o membranes divide chloroplast space into 3 parts intermembrane space stroma thylakoid space o amyloplast colorless stores starch and amylose o chromoplast pigments that give fruits and flowers yellow and orange hues
View Full Document
Unlocking...