Cell Structure and Functions Flashcards
thin barrier that surrounds the cell and separates the cytoplasm from the cell’s environment
The Cell Membrane
Functions of the Cytoplasmic Membrane
Permeability barrier, Anchor for many proteins, Energy conservation
Prevents leakage and functions as gateway for transport of nutrients
Permeability barrier
water transport system
Aquaporins
Site of proteins that participate in transport, biogenetics and chemotaxis
Protein Anchor
Site of generation and use of proton motive force (transport, motility, and biosynthesis of ATP)
Energy Conservation
Shape and rigidity of the cell
Cell Wall
C.W. much thicker and consists of primarily single type of molecule
Gram +
C.W. chemically complex and consists of at least two layers
Gram -
- Polysaccharide: two sugar derivatives,
- N-acetylglucosmaine
- N-acetylmuramic acid
PEPTIDOGLYCAN
Break in B-1,4-glycosidic bonds
Lysozymes
Glycosidic link between NAM and NAG
PEPTIDOGLYCAN
between the amino acids in NAM
Peptide bonds
True or False: Thermoplasma has a cell wall
False
T or F: Archaea contain tough cytoplasmic membrane because they live in osmotically protected habitats
True
T or F: Mycoplasma has sterols, which adds strength and rigidity
True
T or F: Gram- bacteria is 90% PDG while Gram+ bacteria is 10% PDG
False
T or F: Gram- bacteria has an outer membrane
True
T or F: E. coli is a gram+ bacteria
False
Keep proteins whose activities occur outside the cytoplasmic membrane from diffusing away from the cell
Outer Membrane
- Space located betw. outer surface of cytoplasmic mem.
- Gel like consistency
- May contain hydrolytic enzyme, binding proteins, chemoreceptors
Periplasm
- Embedded in outer membrane
- Functions as channels for entrance of solutes
Porins
- Composed of altering N-acetylglucosamine
- Glycosidic bonds in B-1,3
- Not all archaea, some has thick polysaccharide like Methanosarcina and Halococcus
Pseudomurin
- Most common CW of archaea
- Paracrystaline surface layer, symmetrical patterns
- Found in major lineages of Archaea, and some bacteria
- Withstand osmotic bursting, Ex. Methanocaldococcus jannaschii
- Function as selective sieve, allows of low-molecular weight solutes
- Archaea naturally resistant to lysozymes
S-Layers
- Layer that is organized in a tight matrix that excludes small particles like Indian ink
- Adheres firmly to CW, some linked to peptidoglycan
- Virulent factor, difficult to phagocitize
Capsules
- Layer that is easily deformed and do not exclude particles and is more difficult to see
- Are loosely attached and can be lost from the cell surface
Slime layer
- Enable cells to stick to surfaces, including animal tissues
- Can form pellicles, thin sheet of cells on liquid surface
Fimbriae
- Similar to fimbriae but longer and only one or few pillion surface of a cell
- Facilitate genetic exchange in conjugation
- Adhesion to host tissue
Pili
- Assist in cell adhesion
- Twitching motility (a gliding motility)
- Genetic Transfer
Type IV Pili
Granules or other inclusions functions as energy reserves, can be seen directly with a microscope
Cell Inclusions
- Carbon and energy storage polymer
- Synthesized when there is excess of carbon
- Many prokaryotes produce PHA
Poly-B-hydroxyalkanoate( PHA)
- Polymer of glucose
- Storehouse of glucose and carbon energy
- Produced when carbon is in excess
Glycogen
- Source of phosphate for nucleic and phospholipid biosynthesis, ATP
- Phosphate, limiting nutrient in the env.
- Reside in periplasm
- H2S to SO4^2-
Polyphosphates
- can orient themselves using magnetic field
- Found in several aquatic organism
- Grow at low O2 concentration
- Surrounded in thin membrane containing phospholipids,
glycoproteins and proteins (not a bilipid layer) - Proteins play a role in precipitating Fe3+ to Fe3+O4
Magnetosomes
- Spindle-shaped structures of proteins
- Hollow yet rigid, impermeable to liquid and solutes
- Cluster of vesicles, gas vacuoles
- GvpA, forms the vesicle shell, hydrophobic, rigid
- GvpC, strengthen the shell by cross-linking GvpA
- For buoyancy
- Phototrophic organisms
Gas Vesicles
- Produce endospores in a process called sporulation
- Differentiated cells, resistant to heat and chemicals, radiation
- Vegetative to Endospore (dormant stage) to Vegetative
- Bacillus and Clostridium specie
Endospores
– activated endospores are conditioned to germinate when placed in presence of nutrients
Activation
– rapid process, involves loss of microscopic refractibility, Ability to be stained & Loss resistance to heat
Germination
– swelling due to water uptake, Synthesis of RNA, proteins and DNA
Outgrowth
- Bind tightly in DNA in the core and protect it from desiccation and dry heat
- Also, as carbon and energy source for outgrowth
SASPs, small acid-soluble proteins
a thin protein cover
Exosporium
composed of layers of spore-specific proteins
Spore coat
consists of loosely cross-linked peptidoglycan
Cortex
contains core wall, cytoplasm, nucleoid, ribosomes, other cellular essentials
Core
- Funct. by rotation to push or pull cell
- Long, thin appendages
- Flagella are not straight but helical
- Composed of flagellin proteins
- Powered by proton motive force
Bacterial Flagella
- Roughly half the diameter of bacterial flagella
- Same rotation with bacterial flagella
- Several flagellin protein are known for Archaea and no relationship with proteins in bacteria
- swim at speeds 1/10 that of E. coli
- Powered by ATP
Archaeal Flagella
- Bacteria that do not have flagella, glide
- Slower and smoother form
- Needs to be in contact with surface to glide
- Found in filamentous or rod-shaped cells
Gliding Motility
are genetic elements that cannot replicate independently of a living cell
Viruses
T or F: Viruses are not cells and thus nonliving
True
T or F: Viruses are:
- Obligate intracellular parasite
- Different form plasmid because viruses have intracellular form
- They are important in microbial genetics and genetic engineering
True
