Test 1 Ch 4: Cell structures Flashcards
What is a prokaryotic cell?
The DNA is not bound in a nucleus; lacks membrane-bound organelles; cell walls contain peptidoglycan; binary fission
What is a eukaryotic cell?
The DNA is bound in a nucleus; has membrane-bound organelles; cell walls with chemically simple substances; mitosis
What is the size of a bacterium?
0.2-2.0 micrometers in diameter; 2-8 micrometers in length
Name and describe the 3 bacteria shapes
- Cocci (sing. coccus) = sphere
- Bacilli (sing. bacillus) = rod shaped
- Spirals = spiral shape
Name and describe the 3 spiral types
- Vibrio: a curved rod
- Spirillum: cork screw; more rigid than a spirochete
- Spirochete: cork screw; more flexible than a spirillum
Name and describe the 3 types of bacteria arrangements
- Pairs (prefix: diplo-)
- Chains (strepto-)
- Clusters or sheets (Staphylo-)
What is a glycocalyx?
- Located outside the cell wall
- Sugar coat that some cells have and others do not
- Made of polysaccharide, protein, or both
Name and describe the 3 types of glycocalyxes?
- Capsule–> organized and firmly attached to cell wall; increases virulence; grease watermelon
- Slime layer –> unorganized and loosely attached to cell wall; aides in attachment
- Biofilm –> mess of slime layer, bacteria, etc.; plaque on teeth
What are flagella? (Sing. flagellum)
- Used for movement
- Motion: rotational; circumduction; unlike eukaryotic cells
- Some bacteria have it but not all
- Outside the cell wall
What are the flagella parts?
Filament → attached to hook (does the rotating) –> attached to basal body (attached to cell)
What do H-antigens do for flagella?
Identify strains of bacteria (ex: depending on what version is present on the flagella, you can determine what strain of E.coli you are working with)
What are the various arrangements of flagella?
- 1 flagellum = monotrichous
- Flagella coming out all around the cell = peritrichous
- Flagella coming out of 2 distinct ends = amphitrichous
- Multipule flagella coming from one spot = lophotrichous
- no flagella = atrichous
What is an axial filament?
- SImilar structure to flagella
- Only found in spirochetes
- they wrap around the cell, so the entire cell moves in a corkscrew manner
What are fimbriae and pili?
- Hairlike appendages
- Used for attaching to surfaces or to other cells
- Fimbriae = shorter; hundreds of them; used for attaching
- Pili = longer; 1 or 2 of them; used for transferring DNA (and for movement)
What is a cell wall?
- Provides cell shape
- Protects cell from bad environmental changes (such as if the cell is in a hypotonic environment, where the cell takes up water and swells)
- Made up of peptidoglycan
Name and describe the 2 types of cell walls
- Gram positive: Extremely thick; many layers of peptidoglycan
- Gram negative: very thin; 1 or 2 layers of peptidoglycan; outer membrane made of LPS (lipopolysaccharide)
Gram stain steps and physiology
- Crystal violet enters both types of cells and stains both types purple
-Iodine binds to the crystal violet
CV-I = the crystal violet iodine complex
[Form] crystals that are too large to escape through the cell wall
-Alcohol dissolves LPS/outer membrane in gram negatives
CV-I complex escapes from gram negatives, but stays in gram positives
-Safranin re-stains unstained (gram negative) cells red
CV-I still stays in gram positives, cells are purple
Gram stain does not work :(
use acid-fast stain
- some cells have mycolic acid (aka waxy lipid) in their walls that prevents uptake of gram stain dye
- Carbolfuchsin (fuchsia/magenta dye) can get through after you heat the cell
- Mycobacterium (TB, leprosy) have acid-fast walls
- Some (Mycoplasma, archaea) do not have cell walls
Plasma membrane
- Inside the cell wall
- Selectively permeable
- made up of Phospholipids, proteins, NO CHOLESTEROL/STEROLS
- Location of cellular respiration enzymes
Selective toxicity
When designing a drug, you want the drug to be toxic to the microbe causing disease, but harmless to the host
(cell walls are a good target because humans do not have cell well but bacteria do)
Chromatophores
- Only found in a limited # of bacteria
- Plasma membrane folds inward into the cytoplasm
- Contains pigments and enzymes involved in photosynthesis
Cytoplasm
- 80% water
- Some protein, carbs, lipids, ions found inside
- have a cytoskeleton
- No membrane-bound organelles or nucleus
Nucleoid
- Part of the cytoplasm
- The location of the bacterial chromosome
- Has plasmids (small, circular self-replicating DNA molecule)
- Has Ribosomes
What are inclusions?
- Storage structures
- Reserve deposits for nutrients that will be used later
What are the various types of inclusions?
These ones have a main purpose of storage
- Metachromatic granules: reserve deposit for phosphate (needed to make ATP)
- Polysaccharide granules: stores polysaccharides
- Lipid inclusions: stores lipids
- Sulfur granules: located in some bacteria not all; store sulfur (some bacteria use sulfur instead of oxygen)
- Carboxysomes: contain carbon-fixing enzymes; found only in photosynthetic bacteria
Which 2 inclusions are mainly used for movement, rather than storage?
- Gas vacuoles: fill with gas and allow buoyancy
- Magnetosomes: contain iron oxide and turn bacteria into a magnet that can attach to metal
What are endospores?
- Formed by cells when essential nutrients are depleted
- Cell copies DNA and forms a hard shell
- Highly durable
- Survrive for a super long time
- Only formed by some gram-positives like Clostridium and Bacillus
- Very few species of bacteria form endospores
