Cell Structure of prokaryotes in the domains Bacteria and Archaea, and Eukarya Flashcards
Prokaryotes differ from eukaryotes in ____ and _______
Elaborate
size and simplicity
- most are smaller
- most lack internal membrane systems
- and no internal phospholipid bilayer membranes
prokaryotes are divided into 2 taxa, the domains are…
Bacteria and Archaea
pictures on slides 4-6
:)
Morphology is…
the cell shape
what are the 3 major cell morphologies?
- ) Coccus (pl. cocci): spherical or ovoid
- ) Bacillus (Rod; pl. Bacilli)): cylindrical shape
- )Spirillum: spiral shape
* *Many variations on basic morphological types
diplococci (s., diplococcus) arrangement is….
pairs
streptococci arrangement is…
chains
staphylococci arrangement is…
grape like clusters
tetrads arrangement is…
4 cocci in a square
sarcinae arrangement is…
cubic configuration of 8 cocci all perpendicular to each other
the 5 Cocci are….
diplococci streptococci staphylococci tetrads sarcinae
What are the 3 Bacilli? describe
Diplobacilli- 2 bacilli
Streptobacilli – chains of bacilli
Pallisade – several parallel cells along long axis
describe the shape and arrangement of Bacilli (s., bacillus)
- rods
* coccobacilli – very short rods
describe the shape and arrangement of Vibrios
resemble rods, comma shaped
describe the shape and arrangement of Spirilla (s., spirillum)
rigid helices
describe the shape and arrangement of Spirochetes
flexible helices
describe shape and arrangement of Mycelium
network of long, multinucleate filamentous cells
describe shape and arrangement of Pleomorphic
organisms that are variable in shape
online definition: ability of some bacteria to alter their shape or size in response to environmental conditions
describe shape and arrangement of Archaea
pleomorphic, branched, flat, square, other unique shapes
What are the advantages of being a small cell?
Small cells have more surface area relative to cell volume than large cells (i.e., higher S/V)
- This allows greater nutrient exchange per unit cell volume
- Thus, small cells tend to grow faster than larger cells
*Slide 18 has a picture
Cellular organisms less than__ in diameter are unlikely
0.15 µm
_________tend to contain small cells (0.2–0.4 µm in diameter
Open oceans
starting from the outside going on, what are the 4 parts of the Prokaryotic Cell Structure?
1) Structures exterior to the cell wall
2) Cell Wall
3) Cell membranes
The three above together are also referred to as the cell envelope; there are differences in the cell envelope between Archaea and Bacteria
4) Structures within cell membrane
**Slides 21 and 22
describe prokaryote cell membranes (2)
- Absolute requirement for all living organisms (all 3 domains)
- Some prokaryotes (both domain Bacteria and Archaea) also have internal membrane systems (but these are different from the internal membrane systems in eukaryotes)
what are 5 functions of the cell membrane in all 3 domains? describe each function
- ) Maintains cell’s integrity - Vital barrier that separates cytoplasm from environment (if no cell membrane, no cell)
- ) Regulates transport - highly selective permeable barrier
- ) Energy metabolism in prokaryotes (not eukaryotes)
- ) Protein attachment
- ) Receptors for detection of and response to chemicals in surroundings
describe the Fluid Mosaic Model of Membrane Structure (all domains) (2)
- ) Membrane somewhat fluid, somewhat solid
- ) Lipid bilayers with floating proteins
- amphipathic (having both hydrophilic and hydrophobic parts) lipids
- polar ends (hydrophilic – interact with water)
- non-polar tails (hydrophobic – insoluble in water)
- membrane proteins
describe the Domain Bacteria Cell Membrane (2) and describe
- ) General structure:
- phospholipid bilayer plus proteins (6–8 nm wide) ; no sterols, but +/- hopanoids or other molecules
- Contain both hydrophobic and hydrophilic components - ) Fatty acids point inward to form hydrophobic environment; hydrophilic portions remain exposed to external environment or the cytoplasm
**slides 28-31
what are 2 types of membrane proteins? describe them
this is not naming specific proteins
Peripheral
-loosely connected to membrane on cytoplasmic side
-easily removed
Integral
-amphipathic:embedded within membrane and project -outward or inward
-carry out important functions
-may exist as microdomains
proteins that completely cross the membrane from one side to the other are called what?
Transmembrane proteins
describe the outer surface of cytoplasmic membrane
can interact with a variety of proteins that bind substrates or process large molecules for transport
describe the inner surface of cytoplasmic membrane
interacts with proteins involved in energy-yielding reactions and other important cellular functions
what are 2 membrane strengthening agents? describe them
- ) Sterols
- Rigid, planar lipids found in eukaryotic membranes -Strengthen and stabilize membranes
- Only found in a very few prokaryotes (typically wall-less prokaryotes (ie, Mycoplasma)) - ) Hopanoids
- Structurally similar to sterols
- Present in membranes of many Bacteria
Saturation levels of membrane ______ reflect __________ such as _________
lipids; environmental conditions; temperature
True or False: Bacterial membranes lack sterols but do contain sterol-like molecules.
Explain Answer
True.
hopanoids stabilize the membrane
(found in petroleum)
describe the cell membrane fluidity that applies to nearly all domains
liquid crystal; some properties like liquid, some like solid; needs to be at right fluidity which is temperature dependent
if the cell membrane is too hot it results in…
thermal lysis (cell death)
if the cell membrane is too cold it results in…
solidification (gelling)
to maintain the correct fluidity in the cell membrane…
Adjust fatty acid composition of phospholipids
to correct the fluidity in the cell membrane if it’s too cold….
more unsaturated fatty acids – minimize van der Waals forces
to correct the fluidity in the cell membrane if it’s too hot….
more saturated fatty acids – maximize van der Waals forces
to maximize or minimize van der waals forces ……
Adjust ratio of sterols, hopanoids or other lipids to phospholipids
what is passive transport?
transport which does not require ATP or other cellular energy to be used by the cell (but energy of molecules are involved)
what is active transport?
transport which requires the cell to expend its own energy in the form of ATP (or other cellular energy)
what is simple transport?
transport which does not require a transport protein
what is facilitated transport?
transport which requires a transport protein
what is Diffusion?
the movement of a molecule due to its inherent kinetic energy from a region where it is in higher concentration to a region(s) where it is in lower concentration
(it is passive transport)
what is Osmosis?
the diffusion of water across a membrane
passive transport
How a molecule gets across a phospholipid bilayer/protein membrane depends on 3 factors:
1) The charge on the molecule – ionic, polar, non polar
2) The size of the molecule
3) The shape of the molecule
To pass across a phospholipid bilayer/protein membrane a molecule can go either: (2)
*also state the type of transport for both methods
1) Between the phospholipids (simple transport) – must be non polar or a very small polar molecule (water)
2) Through a transport protein (facilitated transport) – all ions and nearly all polar molecules
what is simple diffusion?
diffusion between the phospholipids (passive and no transport proteins) – non polar molecules; water
what is facilitated diffusion? describe
diffusion through a transport protein (passive)
- common in eukaryotes; less common prokaryotes; In direction of concentration gradient (High to low)
- for ions and polar molecules
what is active transport?
any transport which requires the cell to expend its own energy (usually ATP); in prokaryotes, active transport is always facilitated (proteins required) and is in the direction against the concentration gradient (low to high)
active transport can be…..
active transport cannot be….
Can:ions, polar molecules and sometimes bigger non polar molecules
Cannot: No endocytosis/exocytosis in prokaryotes***
What are the three transport events possible?
uniport, symport, and antiport
what is uniport transport?
transport in one direction across the membrane
what is symport transport?
function as co-transporters
describe antiport transport?
a molecule across the membrane while simultaneously transporting another molecule in the opposite direction
describe Receptor-Mediated Transport Systems
- ligand binds specific protein receptors on cell surface
- Show saturation effect
- Highly specific
what is group translocation?
- simultaneous transport and chemical modification of transported substance
- Energy dependent transport that chemically modifies molecule as it is brought into cell
Best known translocation system is…
phosphoenolpyruvate: sugar phosphotransferase system (PTS)
True or False: Most prokaryotes (Bacteria and Archaea) have a cell wall; only a very few exceptions
true
Cell walls are _______ to cell membrane, rigid and mostly __________________ and _______ or ________
exterior; structural polysaccharides and peptides or protein
For _________ and ______________, the primary function of the cell wall is to prevent _________
unicellular; colonial prokaryotes;osmotic lysis
what is osmotic lysis?
pressure from water entering cell causes a rupture of the cell membrane and death of the cell
describe Hypotonic environments (3)
- solute concentration outside the cell is less than inside the cell, and water concentration is higher
- water moves into cell and cell swells
- cell wall protects from lysis
describe Hypertonic environments (3)
- solute concentration outside the cell is greater than inside, water concentration lower
- water leaves the cell
- plasmolysis occurs
slide 48-49
:)
what is a cell that does not have a cell wall? describe it (prokaryote)
Mycoplasma
- does not produce a cell wall
- plasma membrane stronger ( has sterols (rare in prokaryotes) more resistant to osmotic pressure
- Hyper regulates internal solute conc. to stay just slightly hypertonic
slide 51-52
KNOW THIS WELL
describe Peptidoglycan Structure
Mesh-like polymer of identical subunits forming long strands; a structural polysaccharide with amino acids that surrounds the cell
describe the basic sub-unit of peptidoglycan structure
-disaccharide of two alternating modified sugars joined by Beta glycosidic bonds
N-acetylglucosamine (NAG)
N- acetylmuramic acid (NAM
-And alternating D- and L- amino acids in a tetrapeptide (4 amino acids) attached to muramic acid that forms cross links with other tetrapeptides
*slides 53-55
Peptidoglycan strands have a ______ shape
helical shape
peptidoglycan strands in gram negative vs gram positive
1 for each
- ) negative: crosslinks are directly between amino acids in the tetrapeptide
- ) positive: there is often an interbridge of additional amino acids between the tetrapeptides
Peptidoglycan chains are crosslinked by _________ between the _______ for strength
covalet bonds; tetrapeptides
describe Gram-Positive Cell Walls
Composed primarily (~90 %) of peptidoglycan
Also contains large amounts of teichoic acids (negatively charged) embeded in wall
-help maintain cell envelop
-may bind to host cells
-may store PO4; may attract cations
Some gram-positive bacteria have layer of proteins on surface of peptidoglycan
Also have lipoteichoic acid which attaches wall to cell membrane
SLIDES 59-63
describe the Periplasmic Space of Gram + Bacteria
-Lies between plasma membrane and cell wall and is smaller than that of gram-negative bacteria
-Periplasm has relatively few proteins
-Enzymes secreted by gram-positive bacteria are called exoenzymes
(aid in degradation of large nutrients)
describe Gram-Negative Cell Walls
- More complex than Gram- positive
- Consist of a thin layer of peptidoglycan surrounded by an outer membrane
- Outer membrane composed of phospholipids, lipoproteins, and lipopolysaccharide (LPS)
- No teichoic acids
for Gram-Negative Cell Walls, Peptidoglycan is _____ of cell wall weight and in periplasmic space
~5-10%
for Gram-Negative Cell Walls, does Periplasmic space differ from that in gram-positive cells?
Explain
yes!
-may constitute 20–40% of cell volume
-many enzymes present in periplasm
(hydrolytic enzymes, transport proteins and other proteins)
slides 67-68
:)
*Make sure to look at!
what does LPS stand for?
Lipopolysaccharide
LPS consists of 3 parts. describe them
- ) lipid A (endotoxin)
- ) core polysaccharide
- ) O side chain (O antigen)
* Lipid A embedded in outer membrane
* Core polysaccharide, O side chain extend out from the cell
* *slide 70
what are the 6 Importances of LPS?
- ) Contributes to negative charge on cell surface
- ) Helps stabilize outer membrane structure
- ) May contribute to attachment to surfaces and biofilm formation
- ) Creates a permeability barrier
- ) Protection from host defenses (O antigen)
- ) Can act as an endotoxin (lipid A)
