Prokaryotic and Eukaryotic Cell Structure And a Little Taxonomy too!

Taxonomy The science of classification of living organisms. So we can identify and understand relationships between organisms.

Linnaean System First developed by Carolus Linnaeus (1707-1778). Method of classifying things in a hierarchical structure from most general to most similar. Binomial System (2 names) Domain Kingdom (most general) Phylum or Division Class Order Family Genus Species Ex. Eschericia coli or E. coli

Classification Domains constitute a level of classification above the kingdom. Domains are further subdivided into kingdoms etc.

The 3 Domains Prokaryotes Eukaryotes 1. Archaea 2. Bacteria 3. Eukarya - animals - plants - algae - protozoa - fungi Prokaryotes Eukaryotes

5 Kingdoms Based on similar morphology, geographic distribution, and if multicellular, the ability to interbreed. Bacteria

Bergey System Another system for classifying Prokaryotes. Still use kingdom, division or phylum, class, order, family, genus, species. Classification based on similar morphological and biochemical characteristics.

Eukaryotic and Prokaryotic Cells How are they different and how are they the same?

What Is a Cell? It is the fundamental unit of all living matter. Has all characteristics of life. Can live independently of other cells.

All Cells Have the Following: Enzymes A protein that speeds up a chemical reaction. DNA – deoxyribonucleic acid A large molecule that stores genetic information. RNA – ribonucleic acid A large molecule involved in protein synthesis. ATP – adenosine triphosphate The main energy currency of a cell. Amino Acids Proteins are composed of basically the same 20 amino acids.

Eukaryotic Cell Structure Possess membrane-bound organelles. 10-30µm in diameter. Eukaryote = “true nucleus” Their DNA is enclosed by a double membrane.

Eukaryotic Cell Structure Cell Membrane Phospholipid (fatty chain with a phosphate) bi-layer with different types of proteins interspersed. Separates inside of cell from external environment. It has selective permeability. Only certain things can get in and out. Other organelle membranes are similar in structure.

Cell Membrane

Eukaryotic Cell Structure Nucleus Controls the functions of the cell (“the control center). Nuclear membrane – surrounds nucleus. Nucleoplasm – gelatinous matrix. Chromosomes – linear DNA molecules and proteins. Gene – specific DNA segment on the chromosome that contains the information for making a gene product, usually a protein. Nucleolus – where rRNA is made and is used to make a structure called ribosomes.

Eukaryotic Cell Structure Cytoplasm A semi-fluid, gelatinous, nutrient matrix. Contains storage granules and cell organelles. Most of cell’s metabolism occurs. Often called the cytosol.

Eukaryotic Cell Structure Endoplasmic Reticulum (ER) An irregular maze of spaces enclosed by a membrane. “Assembly Line” Rough ER Contains ribosomes Involved in making proteins Smooth ER Does not contain ribosomes Involved in lipid metabolism (fat storage)

Eukaryotic Cell Structure Ribosomes Are important in protein synthesis. Are found in the Rough ER.

Eukaryotic Cell Structure

Eukaryotic Cell Structure Golgi Complex “packaging plant.” Stacks of flattened, membranous sacs. Completes and packages newly formed proteins and lipids. Packages them so that they are ready for storage within the cell or outside of the cell.

Eukaryotic Cell Structure Lysosomes “garbage disposal system” 1 µm diameter Contain lysozyme and other enzymes that break down foreign material. Particles may enter cell by phagocytosis. Also involved in programmed cell death called autolysis or apoptosis. Peroxisomes Membrane-bound vesicles that generate and break down hydrogen peroxide (a dangerous and highly reactive chemical). Used to break down lipids (fats) and destroy toxic molecules.

Eukaryotic Cell Structure Mitochondria “the power plant of the cell” 0.5 – 1 µm in diameter, 7 µm in length Where ATP (adenosine triphosphate) is formed. ATP is the energy currency of the cell. ATP is formed during a reaction called cellular respiration. ATP is formed from our food sources.

Eukaryotic Cell Structure

Eukaryotic Cell Structure Plastids Site of photosynthesis. Contain photosynthetic pigments. Photosynthesis – converting light energy into a source of chemical energy for organism. Chloroplasts – type of plastid that contains chlorophyll. Chlorophyll – a green photosynthetic pigment.

Eukaryotic Cell Structure - Plant Cell micro.magnet.fsu.edu/cells/plants/plantmodel.html

Eukaryotic Cell Structure Cell Wall External structure that provides rigidity, shape, and protection. May be composed of cellulose, pectin, lignin, chitin, and some mineral salts. Usually simpler than prokaryotic cells.

Eukaryotic Cell Structure Plant Cells Cells stained green (DNA) and red (keratin) www.newworldencyclopedia.org/entry/Cell_(biology Illustration by Robert Hooke (c.1665) askabiologist.asu.edu/.../rhooke.html

Cell Walls Cell Walls Absent Present Animals Plants Protozoa Algae Mycoplasma species (type of bacteria) Present Plants Algae Fungi Most Bacteria

Eukaryotic Cell Structure Flagella An organelle of movement. Long, thin structure that moves like a whip to propel organism through liquid environment. Can be found in some species of protozoa, spermatozoa, and algae. Cilia Organelle of locomotion. Usually short, hair-like structures that beat in coordinated, rhythmic movement. Can be found in some species of protozoa and types of cells that line respiratory tract.

Eukaryotic Cell Structure Paramecium – sp. Protozoa. Notice the cilia. microbewiki.kenyon.edu/index.php/Paramecium Euglena – sp. Protozoa. Notice the flagella. www.biologie.uni-erlangen.de/.../fotonm3_eng.htm

Prokaryotic Cell Structure More simple than eukaryotic cells. Can perform all functions necessary for life. Prokaryotes comprise all bacteria and archaeans. Do NOT contain membrane-bound organelles. Typical E. coli cell is about 1 µm wide and 2-3 µm long.

Prokaryotic Cell Structure Bacterial Cell Wall Provides rigidity, strength, and protection. More complex than eukaryote cell walls. Composed of peptidoglycan (polymer of sugars and amino acids) Gram-positive bacteria Thick layer of peptidoglycan with some other molecules. Gram-negative bacteria Thinner layer of peptidoglycan with an outer membrane composed of lipid macromolecules. Genus Mycoplasma do not have cell walls. Archaens have cell walls but not composed of peptidoglycan.

Prokaryotic Cell Structure Cell Membrane Similar to eukaryotic cells. Contains proteins and phospholipids. Selectively permeable. It is very flexible and thin.

Prokaryotic Cell Structure Glycocalyx Thick, slimy, gelatinous material produced by the cell membrane and secreted outside the cell wall. Some bacteria have it. 2 types of glycocalyx 1. Slime Layer Is not highly organized or firmly attached to cell wall. Allows bacteria to glide or slide along surfaces. 2. Capsule Highly organized and firmly attached to cell wall. Chemical composition allows scientists to determine different types of bacteria. Prevent bacteria from being phagocytized by phagocytic white blood cells. Can attach bacteria to a wide array of surfaces.

Prokaryotic Cell Structure diverge.hunter.cuny.edu/~weigang/Lecture-syll.

Prokaryotic Cell Structure Prokaryotic Chromosome Single, long, supercoiled, circular DNA molecule. Embedded in cytoplasm. Found in nuclear region of cell. Does not have a nuclear membrane. Contains all the information for carrying out life processes. Plasmids may also be found in prokaryotic cells.

Prokaryotic Cell Structure Plasmid Small, circular molecule of double-stranded DNA. Not part of the chromosome. Called extrachromosomal DNA. Found in the cytoplasm. May contain 10-100s genes. Number varies per cell.

Prokaryotic Cell Structure Cytoplasm Semiliquid interior of cells. Consists of water, enzymes, dissolved oxygen (in some bacteria), waste products, nutrients, proteins, carbohydrates, and lipids. Everything necessary for its metabolic functions.

Prokaryotic Cell Structure Cytoplasmic Particles Ribosomes are found in the cytoplasm. They are important in protein synthesis. Some substances are stored in cytoplasmic granules. Such as starch, lipids, sulfur, or iron. The type of substance stored depends on the species of organism.

Prokaryotic Cell Structure diverge.hunter.cuny.edu/~weigang/Lecture-syll.

Prokaryotic Cell Structure Flagella A mechanism for movement for some bacteria. Bacteria can be classified and identified by the arrangement of their flagella. Nonflagellated bacteria are usually considered to be nonmotile. Although there are exceptions. Pseudomonas fluorescens – aerobic soil bacteria. www.scienceclarified.com/As-Bi/Bacteria.html

Prokaryotic Cell Structure Pili (Fimbriae) Not associated with motility. Thin, rigid, hair-like structure. Arise in cytoplasm and extend through the plasma membrane, cell wall, and capsule (if present). 2 types of pili 1. Adhesins - allows bacteria to adhere to surfaces. 2. Sex pilus Allows for the transfer of genetic material through a process called conjugation. One bacteria attaches its sex pilus to another cell and transfers its genetic material to the other cell usually in the form of a plasmid.

Prokaryotic Cell Structure Adhesin bacterial cell with pili (fimbriae) ultr23.vub.ac.be/.../fimbrialadhesion.html Bacterial conjugation with sex pilus. www.cbs.dtu.dk/.../roanoke/genetics980309.html

Prokaryotic Cell Structure Spores (Endospores) Bacterial spores called endospores. Usually found in 2 genera: Bacillus and Clostridium. Form through the process sporulation. A copy of the chromosome and some cytoplasm is enclosed in a thick protein coat. This occurs when moisture and nutrients are low. Endospores are resistant to heat, cold, drying, and most chemicals. If adequate conditions are present, the endospore can become an active bacteria.

Endospore Clostridium difficil forming an endospore. Associated with antibiotic related diarrhea caused by toxins produced Red structure is endospore forming. www.chem.wayne.edu/feiggroup/research.htm

Prokaryotic Cell Reproduction Binary Fission One parent cell splits to become 2 daughter cells. This process produces a clone of the parent cell. During this process, its chromosome is replicated in a process called DNA replication. Generation time The time it takes one parent cell to become 2 identical daughter cells.

Binary Fission www.uic.edu/.../bios100/lecturesf04am/lect06.htm

The End