1.2 ultrastructure of cells prokaryotes and eukaryotes
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1.2 Ultrastructure of CellsProkaryotes and Eukaryotes
“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
Prokaryotic Cells
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
Prokaryotes
E. coli
Blue- Green Algae
Prokaryote Cell Structue
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 nucleoid region
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)
Prokaryote Cell Parts
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)
Prokaryotic Reproduction
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
cytoplasmPlasma membrane
No visible slime capsule in this diagram
PILUS
SLIME LAYER
Metabolic Activity of Prokaryotic Cells
1. Photosynthesis: light + CO2 + H2O C6H12O6 + O2
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)
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 Cells
Plasma Membrane: Outer surface of animal cells Made of phospholipid bilayer (usually double layer) 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 fro 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 (mDNA) 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
Eukaryotic Organelles
Atypical Cells
Striated Muscle Muscle Fibres
(Muscle Cells) Longer than
typical cells (30mm opposed to <0.3mm)
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 tube-like 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
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
EUKARYOTES
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