Goals: Identify the structures of eukaryotic and prokaryotic cells Identify the differences between viruses, prokaryotes and eukaryotes Use knowledge about differences between types of cells to solve a case study about pathogens (germs/infectious agents) and disease Viruses: not considered alive Living cells Prokaryotes Bacteria Archae Bacteria Cells have to be big enough to hold their components but surface area limits their total size Eukaryotes Plants Animals Protists Fungi The prokaryotic cell structure Nucleoid: region of circular DNA (not surrounded by a membrane!) Ribosomes: smaller and different from eukaryotes Plasma membrane: encloses the cytoplasm. Cell wall: peptidoglycans protein sugar polymer for support What is one reason that prokaryotes are smaller than eukaryotes? They contain fewer organelles Capsule: sticky outer coat for extra protection. Pili: attachment to surfaces. Flagella: cell movement.
Organelle: A membrane-bound structure with a specialized function within a eukaryotic cell. Many of the chemical reactions that occur within eukaryotic cells occur within organelles. Plasma membrane Nucleus (organelle) Cytoplasm Simplified eukaryotic cell Phospholipid bilayer membranes surround the cell and organelles Hydrophilic heads Hydrophobic tails Inside cell Outside cell Proteins Hydrophobic region of protein Hydrophilic region of protein Typical animal cell: structures & organelles Which other organisms are eukaryotes? Plants, fungi, protists Rough endoplasmic reticulum Smooth endoplasmic reticulum Nucleus DNA in linear chromosomes Flagellum Not in most plant cells Lysosome Centriole Golgi apparatus Ribosomes Cytoskeleton Microtubule Intermediate filament Mitochondrion Plasma membrane Microfilament
Plants are also composed of eukaryotic cells but they have more organelles & a cell wall Nucleus Rough endoplasmic reticulum Ribosomes Golgi apparatus Smooth endoplasmic reticulum Microtubule Not in animal cells Central vacuole Chloroplast Intermediate filament Microfilament Cytoskeleton Cell wall Mitochondrion Plasma membrane Protists are single celled eukaryotes Some protists cause disease Giardia, Trypanosoma (sleeping sickness), Plasmodium (malaria) Eukaryotic organelles and structures compromise four functional categories 1) Manufacturing 2) Breakdown 3) Energy production and use 4) Structural support and movement
Manufacturing and breakdown- the nucleus Chromatin (DNA) Nucleolus Two membranes of nuclear envelope Rough endoplasmic reticulum - nucleus contains DNA and is usually the largest organelle - separated from the cytoplasm by the nuclear envelope. - contains the nucleolus, where ribosomes are made. Ribosomes A structure composed of ribosomal RNA and protein. Made in the nucleolus, and transported into the cytoplasm or rough endoplasmic reticulum. Make proteins for the cell from RNA. Many cell organelles are connected through the endomembrane system The endomembrane system consists of the: nuclear envelope endoplasmic reticulum golgi apparatus lysosomes vacuoles plasma membrane These organelles and structures work together in the synthesis, storage, breakdown and export of molecules from the cell.
The endoplasmic reticulum is a factory for making molecules. Comes in two forms: smooth and rough. Rough endoplasmic reticulum has ribosomes attached. Transmission electron microscopy, 45,000x Smooth endoplasmic reticulum 1) The synthesis of lipids, phospholipids, and steroids. 2) In liver cells, smooth endoplasmic reticulum is used to detoxify drugs. 3) In muscle cells, contribute to muscle contractions by storing calcium ions. Rough endoplasmic reticulum Major functions include: 1) Making more membranes for the cell. 2) Assists in the synthesis of membrane proteins, secretory proteins and lysosomal proteins.
An example of how the rough ER plays a role in synthesizing a functional secretory protein What is the structural term for an amino acid chain? Primary structure Ribosome Transport vesicle buds off. 4 Secretory protein inside transport vesicle. 1 3 Sugar chain added to form a functional, secreted protein Polypeptide 2 Folded protein What is the structural term for a folded protein? Tertiary (3D structure) The golgi apparatus Major functions include: 1) The golgi apparatus receives and modifies proteins made in the endoplasmic reticulum. 2) The golgi sorts and ships proteins to other organelles or the plasma membrane. Shipping and sorting in the golgi apparatus Transmission electron microscopy, 130,000x ER = endoplasmic reticulum
Eukaryotic organelles and structures compromise four functional categories 1) Manufacturing 2) Breakdown 3) Energy production and use 4) Structural support and movement Lysosomes 1) Lysosomes are membrane-bound sacs filled with proteins, called digestive enzymes, which break down molecules. 2) Lysosomes bud off the golgi apparatus. 3) Major function: lysosomes digest food for cells and dispose of wastes. Lysosomes Recycling organelles Digesting food Destroying bacteria and viruses Food Plasma membrane Food vacuole Rough endoplasmic reticulum LYSOSOMES Transport vesicle (containing digestive enzymes) Golgi apparatus Digestion Damaged organelle
Vacuoles function in maintenance of the cell Vacuoles are membrane-bound sacs with a variety of functions: 1) Food vacuoles in animal cells deliver molecules to lysosomes. 2) Central vacuoles in plant cells act like lysosomes and store water. The organelles of the endomembrane system are structurally and functionally interconnected. Organelles and major structures Nucleus Smooth endoplasmic reticulum Rough endoplasmic reticulum Golgi apparatus Transport vessicles Lysosomes Vacuoles Chloroplasts Mitochondria Cytoskeleton Ribosomes Nucleolus Plasma membrane
Eukaryotic organelles and structures compromise four functional categories 1) Manufacturing 2) Breakdown 3) Energy production and use 4) Structural support and movement Organelles that produce energy Chloroplasts: 1) Membrane-bound organelles. 2) Found in plant cells, but not animal cells. 3) Structurally designed to carry out the chemical reactions for photosynthesis, which converts solar energy to chemical energy. Chloroplast structure Different chemical reactions occur in different parts of the chloroplast. Chloroplast Stroma Inner and outer membranes Granum Transmission electron microscopy 9,750 Intermembrane space The compartmentalization of chemical reactions is a key for allowing photosynthesis to occur.
Organelles that produce energy Mitochondria: 1) membrane-bound organelles. 2) Found in all eukaryotic cells, including plant and animal cells. 3) Designed to carry out the chemical reactions for cellular respiration, which converts sugars into energy-rich adenosine triphosphate (ATP). Intermembrane space Mitochondria structure Different chemical reactions occur in different parts of the mitochondria. Mitochondrion Intermembrane space Outer membrane Inner membrane Cristae Matrix Transmission electron microscopy 44,880 The compartmentalization of chemical reactions is a key for allowing cellular respiration to occur. The evolution of mitochondria and chloroplasts Originated as prokaryotic bacteria that established themselves inside eukaryotic cells. This idea is called the hypothesis of endosymbiosis. Evidence that suggests this hypothesis: They contain DNA! They contain prokaryotic-like ribosomes.
Eukaryotic organelles and structures compromise four functional categories 1) Manufacturing 2) Breakdown 3) Energy production and use 4) Structural support and movement The cytoskeleton and related structures The cytoskeleton organizes the shape of the cell, provides structure, and controls cell movement. A network of proteins make up the cytoskeleton. Fluorescent light microscopy, 1000x Three types of protein fibers make up the cytoskeleton Microfilaments: enable cells to change shape and move. They enable cells to contract, that is, get smaller.
Three types of protein fibers make up the cytoskeleton Intermediate filaments: reinforce the cell structure and anchor organelles in place. Made of rope-like protein fibers. Three types of protein fibers make up the cytoskeleton Microtubules: provide anchors for organelles and act as tracks for organelle movement. Composed of tubulin subunits bonded into a hollow tube. Lysosome Microtubule Microtubules make up cilia and flagellum Flagella and cilia are appendages that extend from some cells. Function to move cells in the environment or to move materials outside of cells. Are composed of microtubules.
Microtubules make up cilia and flagellum Flagella propels a cell by a whip-like motion. FLAGELLUM Electron microscopy of sections, 206,500x: Cilia can propel cells by a rowinglike motion. Plasma membrane Flagellum Central microtubules Both have a 9+2 arrangement, but flagella are longer than cilia. Outer microtubule doublet Basal body Basal body Cells are connected in multicellular organisms Cells are connected to each other by three types of cell junctions. Junctions allow cells to communicate, stick together, and coordinate functions. = water-tight seal between cells. = rivets cells together for strength. = protein-lined channels that allow for cell-to-cell communications. Cells are connected in multicellular organisms A glue of proteins and polysaccharides, called the extracellular matrix, holds cells together to form more complex structures, such as tissues and organs. Extracellular matrix Extracellular matrix Plasma membrane Integrin Inside the cell
Cells are connected in multicellular organisms The cell wall of plants connects and protects plant cells. Plasmodesmata are channels that allow plant cells to communicate and share nutrients. Plant cell walls of adjacent cells. Plasmodesmata Prokaryotes Unicellular Reproduce asexually Composition Protected interior (cytoplasm) that contains genetic material (one circle of DNA) as well as complexes of protein enzymes to carry out necessary functions of gathering energy, manufacturing proteins (ribosomes), etc. 41 Prokaryotes Size 0.2-10 micrometer (µm) Composition Phospholipid membrane, many contain cell wall composed of peptidoglycan (positive for chemical Gram stain), those with little or no peptidoglycan called Gram negative (like Coxiella). Coxiella burnetii gramnegative 42
Eukaryotes Prokaryotes DNA Organization Metabolism Organelles Examples linear strands within single circle in nucleoid membrane-bound nucleus region Size 5-100 µm 0.2-10 µm often multicellular, some (i.e., plants) have cell walls (no peptidoglycan) usually single-celled, some have peptidoglycan cell walls usually need oxygen to exist may not need oxygen to exist membrane bound organelles including mitochondria plants, animals, protists, fungi no organelles, different/smaller ribosomes 43 bacteria, archaea Eukaryotes Uni- or multicellular. Reproduce asexually & sexually. Composition: Genetic material (long linear strands of DNA chromosomes) especially isolated and enclosed in membrane (nucleus) Some have cell walls (plants have cellulose, fungi ß-glucan) 44 Eukaryotes Size 10-100 (µm) Composition: Phospholipid membrane outside, as well as membrane bound organelles. Interior membranes/organelles separate functions such as gathering and transforming cellular energy and manufacturing macromolecules. 45
Viruses Not cells Cannot reproduce alone hijacks a host cell to replicate itself. Composition Outer shell: repetitive protein often inserted into a lipid envelope (responsible for recognition and infection of host cell.) 46 Viruses Size Smallest Organisms (50nm) 100 times smaller than bacteria Composition Protected interior that contains genetic material (DNA or RNA) with important protein enzymes required for duplication. 47 Virus hijacking host system 48
Tamiflu: Blocks neuraminidase enzyme made by all influenza A strains (cause the flu and avian flu.) Viruses are unable to remove sticky sialic acid, and can t escape. 49 Eukaryotic Organelles & Endosymbiosis prokaryote N C N Strange similarities: 1. Chloroplasts and mitochondria are the same size as prokaryotes. 2. Both have circular DNA without histones with similar sequence to photosynthetic bacteria (cyanobacteria) and obligate intracellular rickettsia bacteria. 3. Both divide like prokaryotes. 50 Eukaryotic Organelles & Endosymbiosis prokaryote N C N Strange similarities: 4. Have their own protein synthesis machinery (ribosomes) more like bacteria than eukaryotes (sensitivity to Streptomycin). 5. Inner membrane of mitochondria contains unusual phospholipid characteristic of bacterial membranes. 51
Similarities Used to Group Organisms First prokaryotes 3.75 billion years ago Single-celled eukaryotes 2 billion years ago 52 Organism Bacteria Circular DNA Size rdna sequence Phospholipid Similarity Ribosome similarity Divides to make clones Mitochondria