Chapter 7 Inside the Cell How do the parts inside the cell function individually Key Concepts Cells are Within a cell thousands of chemical reactions occur every second molecules are constantly moving across the plasma membrane cell products are transported along protein fibers and elements of the cell s internal skeleton grow and shrink Grouping Cells According to morphology there are two broad groupings of life 1 2 According to phylogeny there are three domains 1 2 3 Prokaryotic Cells Structural Overview All prokaryotes lack a membrane bound nucleus Recent advances in microscopy reveal complexity in prokaryotic structure Archaeal cell structure is relatively poorly understood Bacterial cells vary greatly in size and shape but most bacteria contain several structural similarities Prokaryotic chromosomes are found in a localized area of the cell called the nucleoid Represents 20 of the cell s volume Genetic material is not separated by a membrane They also carry genetic information in which are extra chromosomal pieces of DNA Prokaryotic Cells Internal Structure In addition to the nucleoid chromosome and plasmids other structures are contained within the cytoplasm All prokaryotic cells contain consisting of RNA molecules and protein for protein synthesis Some prokaryotes have membrane enclosed compartments that qualify as little organs An organelle is a membrane bound compartment inside the cell that contains enzymes or structures specialized for a particular function Most prokaryotes have a cell wall Bacterial and archaeal cell walls are a tough fibrous layer that surrounds the plasma membrane Eukaryotes and Prokaryotes Compared Four key differences between eukaryotic and prokaryotic cells have been identified Eukaryotic Cells The relatively large size of the eukaryotic cell makes it difficult for molecules This problem is partially solved by breaking up the large cell volume into several smaller Why are organelles compartmentalized The compartmentalization of eukaryotic cells offers two primary advantages 1 2 The Nucleus The nucleus is large and highly organized STRUCTURE The nucleus is surrounded The nucleus has a distinct region called the nucleolus FUNCTION Contains the cell s chromosomes Ribosomal RNA synthesis in the nucleolus Rough Endoplasmic Reticulum STRUCTURE The rough endoplasmic reticulum rough ER RER is a network of membrane bound tubes and sacs studded with ribosomes The interior is called the lumen The rough ER is continuous with the nuclear envelope FUNCTION New proteins are folded and processed in the rough ER lumen Smooth Endoplasmic Reticulum STRUCTURE The smooth endoplasmic reticulum smooth ER SER lacks the ribosomes associated with the rough ER FUNCTION Enzymes within the smooth ER may synthesize or break down poisonous lipids Reservoir for Ca2 ions Golgi Apparatus STRUCTURE The Golgi apparatus is formed by a series of stacked flat membranous sacs called cisternae FUNCTION The Golgi apparatus Membranous vesicles carry materials to and from the organelle Mitochondria STRUCTURE Mitochondria have two membranes the inner one is folded into a series of sac like cristae The solution inside the cristae is called the mitochondrial matrix Mitochondria have their own DNA and manufacture their own ribosomes FUNCTION Ribosomes STRUCTURE Ribosomes are non membranous they are not considered organelles Have large and small subunits both containing RNA molecules and protein Ribosomes can be attached to the rough ER or free in the cytosol the fluid part of the cytoplasm FUNCTION Peroxisomes STRUCTURE Peroxisomes are globular organelles bound by a single membrane FUNCTION Specialized peroxisomes in plants are packed with enzymes that oxidize fats to form a compound that can be used to store energy for the cell Lysosomes STRUCTURE Lysosomes are single membrane bound structures containing approximately 40 different digestive enzymes Lysosomes are found in animal cells FUNCTION
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