8 20 2013 General Features of Cells Chapter 4 Cells come in a variety of shapes and sizes http www sonefe org Cells and Microscopy cell diversity jpg Cells are the smallest unit of life Figure 4 1 1 8 20 2013 Most cells are only seen with microscopes Microscopes invented in the 1600s and used to examine cells in the 1660s Three key principles of microscopy include Observations of cells using light microscopy led to http www micro magnet fsu edu primer museum janssen html http en wikipedia org wiki File Cork Micrographia Hooke png The cell theory established in 1858 includes three fundamental principles http dodd cmcvellore ac in hom 28 20 20Virchow html Spontaneous generation of cells or not The Paris Academy of Sciences offered a prize for any experiments that would help resolve this conflict fli t The prize was claimed by Louis Pasteur s experiments disproving spontaneous generation of microorganisms 1859 http bioweb wku edu courses Biol115 Wyatt Sci method Pasteur png 2 8 20 2013 The death of spontaneous generation http amoebamike files wordpress com 2009 10 pasteurs experiment jpg The death of spontaneous generation The only variable in Pasteur s experiment was the broth s exposure to preexisting cells http amoebamike files wordpress com 2009 10 pasteurs experiment jpg Cells come in a variety of shapes and sizes http www sonefe org Cells and Microscopy cell diversity jpg 3 8 20 2013 Cell size is inherently limited Campbell Figure 6 8 There are two distinct classes of cells Campbell Figure 1 8 Prokaryotes lack a true nucleus derived from pro meaning before and karyote meaning kernel to describe the nucleus and have a relatively simple structure Eukaryotes have a true nucleus derived from eu meaning true and have structures and functions compartmentalized within the cell The large internal volume of eukaryotic cells is subdivided into bacterium sized compartments Advantages of compartmentalization 1 Incompatible reactions are separated 2 Enzymes that work together can be clustered together 3 Substrates required for reactions have small diffusion distances Campbell Figure 1 8 4 8 20 2013 All cells share five features Campbell Figure 1 8 Animal and plant cells are examples of eukaryotic cells Figure 4 8 Figure 4 5 5 8 20 2013 The nucleus and endomembrane system organize and express the cell s genetic material 1 Nucleus 2 Endoplasmic reticulum 4 Plasma membrane 3 Golgi apparatus Figure 4 5 The nucleus contains most of the cells genetic information Genetic information is contained in chromosomes made up of chromatin a complex of DNA and protein The nuclear envelope consists of two phospholipid bilayer membranes The nucleolus is the site of ribosomal RNA synthesis Nuclear pores form passageways in the nuclear envelope Figure 4 15 Structure of the nucleus Nuclear envelope Nuclear matrix Nuclear lamina 6 8 20 2013 Nuclear pores Are formed from proteins embedded in the in the nuclear envelope l Form passageways or pores in the nuclear envelop that allow small molecules to pass between the nucleus and cytoplasm Figure 4 15 The nucleus and endomembrane system organize and express the cell s genetic material 1 Nucleus 2 Endoplasmic reticulum 4 Plasma membrane Figure 4 5 3 Golgi apparatus The endoplasmic reticulum ER constitutes most of the endomembrane system Ribosomes synthesize proteins and may be bound to the RER or free in the cytoplasm The ER is composed of phospholipid bilayer The space enclosed in the ER is called the lumen or cisternae The ER is divided into two types Rough ER Smooth ER Figure 4 17 7 8 20 2013 The rough endoplasmic reticulum RER is a site of protein synthesis Compare to Figure 4 17 The smooth endoplasmic reticulum SER is a site of carbohydrate and lipid synthesis Compare to Figure 4 17 The nucleus and endomembrane system organize and express the cell s genetic material 1 Nucleus 2 Endoplasmic reticulum 4 Plasma membrane Figure 4 5 3 Golgi apparatus 8 8 20 2013 The Golgi apparatus collects processes and directs the traffic of proteins Figure 6 13 The Golgi apparatus collects processes and directs the traffic of proteins Consists of a stack of flattened membranes Contains three compartments cis medial and trans Performs three primary functions The Golgi apparatus collects processes and directs the traffic of proteins Proteins are received at the cis Golgi Proteins are shipped from the trans Golgi Processing often involves glycosylation and usually occurs in the medial Golgi 9 8 20 2013 Plasma membrane separates the interior of the cell from its external environment The plasma membranes is composed of a phospholipid bilayer It is embedded with a variety of proteins that allow communication between the internal and external environment of the cell Campbell Figure 6 7 The secretory pathway Figure 4 18 Other endomembrane components Lysosomes Peroxisomes Vacuoles 10 8 20 2013 The semiautonomous organelles are important metabolic centers The semiautonomous organelles are membrane bound compartments hence organelles They can grow and reproduce within the cell and are NOT generated by budding off the endomembrane system hence autonomous However they depend on the cell for synthesis of most of their proteins which are imported from the cytosol hence semi autonomous They include mitochondria and chloroplasts They arose by endosymbiosis of prokaryotic cells that could either respire or photosynthesize Mitochondria and chloroplasts These organelles are metabolic centers where energy is changed from one form to another Mitochondria are the sites of cellular respiration and found in both plant and animal cells Mitochondria and chloroplasts These organelles are metabolic centers where energy is changed from one form to another Mitochondria are the sites of cellular respiration and found in both plant and animal cells Chloroplasts are the sites of photosynthesis and are only found in photosynthetic plant cells 11 8 20 2013 You need to know the structure of the mitochondria and chloroplasts Evolution of modern eukaryotic cells Endosymbiotic theory Lynn Margulis The cytoskeleton provides the cell with organization support and motility The cytoskeleton performs a number of roles including Components of the cytoskeleton are Fibroblast cell stained to show microtubules yellow and microfilaments blue 12 8 20 2013 Microfilaments Diameter Structure Protein subunits Characteristic Primary roles Maintain cell shape Provide cell motility in the form of muscle contraction pseudopodia and