EXAM 1: LO 3, 4 & 5 Flashcards
Exopolysaccharide
a polysaccharide secreted by an organism into the environment
Chemotaxis
- Movement of a motile cell or organism in a direction corresponding to a gradient of increasing or decreasing concentration of a particular substance
Adhesin
cell surface components or appendages of bacteria that facilitate bacterial adhesion/adherence to other cells or to inanimate surfaces
Signal Transduction
a mechanism that converts a mechanism/chemical stimulus to a cell into a specific cellular response
Where does DNA replication and protein synthesis occur in prokaryotes? What does this link?
The cytoplasm
Transcription/translation are linked
Where does DNA replication occur in eukaryotes? What about translation (protein synthesis)?
- DNA replication (transcription) occurs in the nucleus
- Translation occurs in the cytoplasm for protein synthesis
Eukaryotic cells include what kingdoms?
Composed of algae, protozoa, fungi, animals, and plants
Prokaryotic cells include what
Include bacteria and archaea
Specify the exact shapes for prokaryotic cells
Cocci (spherical)
Bacilli (rod)
Spirochete (spiral)
Vibrio (comma)
Prokaryotes External Structures
What are glycocalyces (Capsules & EPS)? What are they composed of?
- The gelatinous, sticky substance surrounding the outside of the cell
- Composed of polypeptides, polysaccharides, or both
- Can be rigid or flexible, integral, or peripheral
Prokaryotes External Structures
Capsules
- Firmly attached to the cell surface
- Composed of polypeptides and polysaccharides
- May prevent bacteria from being recognized by host
- Much more defined than EPS on the surface of the cell
Prokaryotes External Structures
EPS
- Loosely attached to cell surface
- Promotes attachment to surfaces
- More diffuse on the surface of the cell, compared to the capsule
Prokaryotes External Structures
Flagella is composed of what?
Filament, Hook and Basal Body
Prokaryotes External Structures
Flagella: Filament?
- Extends from cell surface to the tip
- Hollow, rigid cylinder
- Composed of protein flagella
- Some bacteria have sheath around filament
Prokaryotes External Structures
Flagella: Hook?
Links filament to basal body
Prokaryotes External Structures
Flagella: Basal Body ?
Anchors filament & hook to cell wall by a rod & series of either 2 or 4 rings
Fimbriae function
- Responsible for motility and adherence
- Twitching motility (nondirectional)
- Sticky, bristle-like projections that are shorter than flagella
- Contains adhesin
- Mediate attachment to substances in the environment
- Required for biofilm formation
Flagella and fimbriae require for _______
swarming
_______ is often the initial step of persistent infection
Adherence
Pili function
Composed of what?
- Responsible for conjugation
- Tubules composed of pilin
- Longer than fimbriae but shorter than flagella
- Not universal→ Absent in Gram +
Conjugation is what
process by which one bacterium transfers genetic material to another through direct contact
Eukaryotes External Structures
Glycocalyses
- Never as organized as prokaryotic capsules
- Help anchor animal cells to each other
- Strength cell surface
- Provide protection against dehydration
- Function in cell to cell recognition & communication
Eukaryotes External Structures
Explain cell wall components of eukaryotic orgs.
Plants: cellulose in cell wall
Fungi: cellulose, chitin, and/or glucomannan in cell wall
Algae: a variety of polysaccharides in the cell wall
Eukaryotes External Structures
How do eukaryotic flagella differ structurally and functionally from prokaryotic flagella?
- Within the cytoplasmic membrane (undulate)
- They have a filament
Prokaryotes Cytoplasmic Membrane
Bacterial cytoplasmic membrane function
- Interface with the environment
- Signal transduction
- Maintain concentration & electrical gradient (energy)
- Transport → Selectively permeable
Prokaryotes Cytoplasmic Membrane
Bacterial cytoplasmic membrane structure
Phospholipid bilayer
Gram (+) only has a plasma membrane
Gram (-) has an inner & outer membrane
What is it and what are the components of the fluid mosaic model
- Describes the structure of the plasma membrane as a mosaic of components
- Includes: Phospholipids, cholesterol, proteins, and carbohydrates—that gives the membrane a fluid character
Prokaryotes Cytoplasmic Membrane
Periplasm
space between the inner and outer membrane in Gram-negative bacteria.
Prokaryotes Cytoplasmic Membrane
Archaeal cell walls / cytoplasmic membrane
- Most archaea have cell walls
- Do not have peptidoglycan → contain a variety of specialized polysaccharides and proteins
- All archaea have cytoplasmic membranes (same functions as bacterial cytoplasmic membranes)
Eukaryotes Cytoplasmic Membrane
contains what?
Function?
- All eukaryotic cells have cytoplasmic membranes
- Are a fluid mosaic of phospholipids and proteins
- Contain steroids to help maintain fluidity
- Contain regions of lipids and proteins called membrane rafts
- Control movement into and out of the cell
Prokaryotes Cytoplasm
List and characterize the components of the bacterial cytoplasm
Metabolic processes occur here
DNA replication, transcription & translation occurs
Prokaryotes Cytoplasm
What are the non-membranous organelles of bacterial cytoplasm? Functions?
1) 70S (50&30) Ribosomes → translation (protein synthesis)
2) Cytoskeleton → plays a role in forming the cell’s basic shape
3) Nucleoid
4) Inclusions
5) Endospores
What are endospores?
- Unique structures produced by some bacteria that are a defensive strategy against unfavorable conditions
- Function → ensures the survival of a bacterium through periods of environmental stress.
- Dormant, non reproductive, durable
What are Inclusions
Cytoplasmic raw materials that include reserve deposits of chemicals
Archaeal cytoplasm structures
70S ribosomes
Fibrous cytoskeleton
Circular DNA
How does Archael cytoplasm differ from the bacterial cytoplasm?
- Different ribosomal proteins
- Different metabolic enzymes to make RNA
- Genetic code is more similar to eukaryotes
Eukaryotes cytoplasm structure
NO FIMBRIAE IN EUK.
80S Ribosomes (larger than prokaryotic ribosomes)
Cytoskeleton
Flagella
Cilia
Membranous organelles
Eukaryotic cytoskeleton
- Made up of tubulin microtubules, actin microfilaments, and intermediate filaments
- Anchors organelles
- Produces basic shape of the cell
Eukaryotic Flagella
- Flagella are within the cytoplasm (flagella of prokaryotes are external)
- Shaft composed of tubulin arranged to form microtubules
- Filaments are anchored to cell by basal body (no hook)
- Maybe single or multiple flagella
- Function: motility BUT DO NOT ROTATE, but undulate rhythmically
Eukaryotic cilia
- Shorter and more numerous than flagella
- Coordinated beating propels cells through their environment (MOTILITY)
- Also used to move substances past the surface of the cell
Cell wall composition of plants, fungi, algae and bacteria
Plants Cell Wall → cellulose in cell wall
Fungi Cell Wall → cellulose, chitin, and/or glucomannan in cell wall
Algae Cell Wall → a variety of polysaccharides in the cell wall
Bacterial Cell wall → peptidoglycan in cell wall
What is bacterial wall function?
- Responsible for shape & rigidity
- Provide structure and shape and protect the cell from osmotic forces
- Protects against some antimicrobial drugs & targeted by others
- Can be Gram + or Gram -
Discuss the function of flagella.
- Are responsible for movement
- Have long structures that extend beyond cell surface
- Are not present on all bacteria
Discuss the structure of flagella: filament
- Extends from cell surface to the tip
- Hollow, rigid cylinder
- Some bacteria have a sheath around the filament
Discuss the structure of flagella: Hook
Links filament to the basal body
Discuss structure of flagella: basal body
- Anchors filament and hook into the cell wall by a rod and a series of either two or four rings of sensory and motor proteins that make it rotate
- ROTATION, not undulation
List and describe the different types of flagellation
Peritrichous: covers the surface
Monotrichous: single polar flagellum
Lophotrichous: tufted bunch at one pole
Amphitrichous: single flagellum at both poles
Endoflagella (on spirochete): Axial filament wraps around, causing a spiral/corkscrew shape
Explain swimming, what structure does it require?
Explain counter/clockwise
- require flagella
- rotation propels bacterium through the environment
- not random: response to stimuli (moves toward/away from it)
Counterclockwise: run → run towards stimuli
Clockwise: tumble
What is taxis?
- Movement in response to stimuli
- Towards chemical gradient
- In the presence of an attractant tumbling frequency is reduced and runs in direction of attractant are longer
Explain twitching, what structures does it require?
- requires fimbriae
- Like a stress response, doesn’t matter which direction, just needs to move
Explain swarming, what structures does it require?
- Flagella & fimbriae are required
- Many bacteria traveling in the same direction/pattern to a food source/attractant at once
What is LPS
IN GRAM NEGATIVE CELLS
- Contributes to neg change on the cell surface
- Stabilizes outer membrane
- Contributes to the attachment on surfaces & biofilm formation
- Protection against host defenses (O antigen) outer portion of LPS
- Can act as an endotoxin (lipid A)
Gram staining main purpose
- Common technique used to differentiate two large groups of bacteria based on their different cell wall constituents.
- Does this by coloring them pink or purple
Why are gram negative bacteria stained pink?
- Attributed to a thinner peptidoglycan wall
- Does not retain the crystal violet during the decoloring process
Describe the structure of peptidoglycan
- Peptidoglycan is a polysaccharide (a derivative of glucose)
- Has alternating units of NAG (N-acetylglucosamine) & NAM (N-acetylmuramic acid)
- Peptide cross-bridge occurring off of NAM → binds to other NAG/NAM polysaccharide chains
- This is where we get the rigidity from
What color is NAM
Pink
Spell NAG
NAG (N-acetylglucosamine)
Spell NAM
NAM (N-acetylmuramic acid)
Discuss the composition of the cell wall in Mycobacteria
- Resistant to Gram stain procedure
- Due to the presence of mycolic acid on the cell wall
- The layer of mycolic acid on the cell wall is described as waxy: has a thin layer of peptidoglycan (but can not be considered gram -)
- Poor absorption of nutrients
- Mycobacterium is the most common ex.
______ bacteria is resistant to gram stain procedure
Acid fast
