1 2 Ultrastructure of Cells Prokaryotes and Eukaryotes

1. 2 Ultrastructure of Cells Prokaryotes and Eukaryotes

Prokaryotic Cells “primitive cells” cells that lack membrane-bound organelles ie: no nucleus, no mitochondria, no vacuoles, etc Ex: bacteria (ie E. Coli) – found in soil, water, on your skin, in your intestine Ex: blue green algae

Prokaryotes organisms that are made of prokaryotic cells. Most prokaryotes are unicellular, such as bacteria, however, they can be multicellular too, such as blue green algae

Blue- Green Algae E. coli

Prokaryote Cell Structure

Prokaryote Cell Structue

Prokaryote Cell Parts CELL SURFACE MEMBRANE / PLASMA MEMBRANE: Thin layer composed of phospholipids Controls the entry/ exit of substance via active or passive transport Selectively permeable

Prokaryote Cell Parts CELL WALL: Rigid to semi-rigid wall surrounding the plasma membrane. Contains pores to allow passage of materials in and out of the cell. The Cell wall supports the cell and provides shape

Prokaryote Cell Parts SLIME CAPSULE: Protective outside layer, found outside the cell wall Also known as “surface layer” or the “S-layer” Protects the cell from environmental dangers Contains proteins and or glycoproteins

Prokaryote Cell Parts Cytoplasm: The “inside” of the cell Contains cytosol (fluid of the cell) Contains the enzymes (biological catalysts) for catalyzing chemical reactions of metabolism Contains ribosomes and naked DNA No membrane bound organelles!

Prokaryote Cell Parts NUCLEOID: Region of the prokaryotic cytoplasm where genetic information is found (1 main chromosome and plasmids) The 1 chromosome is made of NAKED DNA This means that the DNA is not bound to proteins (like histones) This reduces the amount of space they take up Usually circular

Prokaryote Cell Parts PLASMID: Small, circular, naked, DNA Smaller, and contains less information than the chromosome. Found in the cytoplasm

Prokaryote Cell Parts Mesosome: Indentation in the cell membrane of bacteria Unknown function, produced by chemical fixation techniques.

Prokaryote Cell Parts RIBSOSOME: Made of RNA and proteins Makes proteins Less dense than eukaryotic ribosomes

Prokaryote Cell Parts FLAGELLUM: threadlike, motile proteins structures and are used for locomotion Cell may have none, 1, or several

Prokaryote Cell Parts PILI (plr) / PILUS (singular): Thin protein tubes found outside the plasma membrane and extend out from the slime capsule Attachment Pili Have sticky ends that allow it to attach to surfaces (i. e. another cell) Conjugation Pili (Sex Pili) Longer Build a bridge between 2 bacterial cells allowing for exchange of DNA (conjugation)

Prokaryotic Reproduction Prokaryotic cells divide asexually by binary fission (similar to mitosis) They duplicate their chromosome (their circular DNA) and then split in half (each new daughter cell gets half the cytoplasm and 1 chromosome)

Since binary fission is a form of asexual reproduction, the daughter cells produced are identical to the original parent cell. Conjugation (with the help of conjugation pili) allows for genetic variation – allows for a new combination of DNA

Annotate and Identify Structures from and electron micrograph of E. Coli ribosome Nucleoid region (DNA, plasmid) Cell wall cytoplasm Plasma membrane No visible slime capsule in this diagram

PILUS SLIME LAYER

Metabolic Activity of Prokaryotic Cells 1. Photosynthesis: light + CO 2 + H 2 O C 6 H 12 O 6 + O 2 2. Nitrogen Fixation: Convert nitrogen from an unusable from to a usable form 3. Fermentation: convert organic substances into simpler substances (ie sugar into ethanol)

Eukaryotic Cells complex cells with membrane bound organelles Ex: the cells that make up you! (and other animals) Ex: plant cells STRUCTURE: all eukaryotes contain: Plasma membrane Central nucleus with DNA Membrane bound organelles in the cytoplasm

Eukaryotic Organelles Plasma Membrane: Outer surface of animal cells Made of phospholipid bilayer Controls the entry and exit of molecules

Eukaryotic Organelles Nucleus: Control center of the cell Largest organelle Surrounded by a double membrane (nuclear envelope) Contains chromosomes – made of DNA and proteins Nuclear Envelope: Controls entry and exit of molecules Contains nuclear pores (openings)

Eukaryotic Organelles Chromosomes: Contains hereditary info Made of DNA and proteins Nucleolus: In center of nucleus Makes ribosomes

Eukaryotic Organelles Endoplasmic Reticulum: Tubules for transport and synthesis of large organic molecules Often continuous with the nuclear envelope RER – rough ER – has ribosomes SER – smooth ER – makes carbs and lipids

Eukaryotic Organelles Ribosomes: Made of proteins and RNA Site of protein synthesis Lysosomes: “suicide sac” Contains digestive enzymes breakdown of macromolecules Digest worn-out cell parts/organelles Digest pathogens Can cause cell death if it breaks open (cell lysis) and releases enzymes

Eukaryotic Organelles Mitochondrion: Site of cellular respiration Makes ATP (adenosine triphosphate) energy for the cell Double membrane Has its own DNA (m. DNA) Own ribosomes Chloroplast: Site of photosynthesis (makes sugar from light energy) Has double membrane, own DNA, own ribosomes

Eukaryotic Organelles Flagella: Long microtubules strand “whiplike” tail For motility Cillia: Short microtuble strands For motility

Eukaryotic Organelles Golgi Apparatus/Golgi Body/Golgi Complex: Looks like a stack of deflated balloons Membranous sacs “Packaging plant” of the cell Packages cell products (ie: carbs and lipids) Vacuoles: Membrane bound organelles used for storage of water, wastes, and macromolecules

Eukaryotic Organelles Cell Wall: Rigid outer layer of plant cells Made of cellulose Plasmodesmata: Gaps in cell walls Create junctions between plant cells

Atypical Cells Striated Muscle Fibres (Muscle Cells) Longer than typical cells (30 mm opposed to <0. 3 mm) Multiple nuclei

Atypical Cells Giant Algae Ex Acetabularia, a unicellular organism, can grow to a length of 10 cm, despite having only 1 nucleus. Usually organisms that large consist of several cells.

Atypical Cells Aseptate Hyphae Narrow thread like structure in fungi Have a cell wall and membrane. In aseptate fungi, the hyphae is an uninterrupted tubelike structure with many nuclei spread along it.

Animal vs Plant Cells ANIMAL CELL No chloroplasts No cell wall Usually no large central vacuole Carbohydrates stored as glycogen Have lysosomes Amorphic shape PLANT CELL Chloroplasts usually present Cell wall present Have large central vacuole Carbohydrates stored as starch or cellulose Generally lack lysosomes Rigid shape, often with straight edges

Prokaryotic Cell vs Eukaryotic Cell PROKARYOTES EUKARYOTES Do not have membrane bound organelles Naked circular DNA (no proteins associated) DNA in nucleoid region RIBOSOMES: free floating in cytoplasm No mitochondria; uses plasma membrane for respiration Membrane bound organelles present DNA wrapped around histone proteins DNA within the nucleus Ribosomes: attached to RER or free floating in cytoplasm Has mitochondria for aerobic cellular respiration