Prokaryotic Cells (Bacteria and Archaea) Flashcards
Some examples of prokaryotes
bacteria and archea
type of chromosomes prokaryotes have
one circular chromosome
Some characteristics of prokaryotic cells
-no nuclear membrane
-plasma membrane acts as mitochondrial membrane
-organelles are absent
-genetic material in single circular chromosome
-no histone proteins (eukaryotes hmr pl shi)
-cell wall is made up of carbohydrates and amino acids (polysaccharides)
-divide asexually by binary fission, sexually by conjugation
Where is genetic material present?
-in a nucleoid (spherical, rod-shaped or spiral)
-single circular chromosome
What is capsule? What does it do?
-outer protection found in bacterial cells
-outside of the cell wall
-moisture retention, protection, attachment
What is the cell wall in prokaryotes?
-outer layer of cells that gives shape
-protects and prevents bursting
Component of cell walls in bacteria
-peptidoglycans => polymer of linked sugars and polypeptides
Unusual fact about peptidoglycans
-contains both L and D amino acids
-L is the common one in making proteins
Peptidoglycans are present in which prokaryotes?
-bacteria
-archaeal cell walls dont have them
What do archaeal cell walls have?
-pseudopeptidoglycan
-polysaccharides (sugars)
What is cytoplasm composed of?
-enzymes, salts and cell organelles
What does cell membrane (plasma membrane do)?
-surrounds cytoplasm
-regulate entry and exit of substances
What is plasma membrane made up of (bacteria)?
-phospholipid bilayer
What is phospholipid( bacteria)?
-lipid composed of glycerol molecule attached to hydrophilic phosphate head and 2 hydrophobic fatty acid tails
What are pili?
-hair-like outgrowth used for attachment to surfaces
examples of bacterial pili
- sex pilus
-allows DNA to transfer between 2 cells in conjugation process - type IV pili
-helps bacterium move in environment
What is a flagellum?
-structures that help with locomotion
-whip-like
What are ribosomes?
-involved in protein synthesis
What are plasmids?
-non-chromosomal double-stranded DNA structures/not involved in reproduction (extra chromosomal DNA)
-smaller than chromosomal DNA
What do plasmids do?
-carry genes for enzyme production
What is nucleoid region?
-where genetic material is present in prokaryotes
-does not have a membrane
What are fimbriae?
-thin filaments used for adhesion
cell projections in prokaryotes
flagella, pili, fimbriae, cilia
4 main components of prokaryotic cells?
-plasma membrane
-cytoplasm
-DNA
-ribosomes
How do prokaryotes (bacteria) reproduce?
-asexually by binary fission
-sexually by conjugation
Explain binary fission.
-Mature parent cells split into 2 identical daughter cells
-used for propagation (simple and fast)
-starts at replication origin and duplicate the genome
-duplicated genome segregate into two separate ends of cell
-plasma membrane grows inward to form a septum
-after septum formation, 2 daughter cells
Explain conjugation.
-sexual reproduction method to directly transfer genetic material
-via conjugation tube or via direct contact
-two cells are donor cell and recipient cell
-plasmid of donor cell comes near the sex pilus and nicks from one point to become single stranded
-the strand goes into the recipient through the tube
-both cells covert the DNA into double strand by synthesizing complementary strand
What do donor cells have?
-fertility factor (F factor) needed to develop the sex pilus
Where are antibiotic resistant genes located?
-plasmid DNA of bacteria
What are endospores?
-tough dormant structures, help bacteria survive during unfavorable conditions
Where is archaeal cell found?
-extreme environment such as hot springs, soil, marshes, even human
chromosomes in archaea
single circular chromosome (circular double stranded DNA)
initiator tRNA in bacteria and archaea
bacteria- formyl-,methionine
archaea - methionine
calvin cycle
-exist in bacteria
-none in archaea
What is plasma membrane made up of in archaea?
-glycerol is linked with phytanyl units rather than fatty acids
-tends to be lipid monolayer some time
2 major groups of bacteria
gram positive and gram negative based on gram stain reaction (used to determine the category based on the type of cell wall)
cell wall of gram positive bacteria
-thick cell wall
-has teichoic acids
cell wall of gram negative bacteria
-thin cell wall
-lipopolysaccharide and lipoproteins
what are phototrophs
get energy from light/the sun
what are chemotrophs
get energy from chemical compounds
autotrophs
get energy by fixing carbon from carbon dioxide inorganic compounds
heterotrophs
get carbon from organic compounds of other organisms
nutrition mode of bacterium thiobacillus concretivorans
consume metal-melting sulfuric acid
plants nutrition mode
photoautotrophs
humans nutrition mode
chemoheterotrophs
prokaryotes nutrition modes
all 4 categories
photoauto, photohetero, chemoauto, chemohetero
what are obligate aerobes?
organisms that require oxygen for metabolism
what are obligate anaerobes?
organisms that can’t tolerate oxygen and only perform anaerobic metabolism
prokaryotic example of an obligate anaerobe
-bacterium called C. botulinum
-causes botulism (food poisoning) when it grows inside canned food because they multiply well inside sealed cans
what are facultative anaerobes
-aerobic metabolism when O2 is there, anaerobic when theres no O2
bacteria example of facultative anaerobes
bacteria that cause staph and strep infections
what is carbon cycle?
physical cycle of carbon through earth’s biosphere, geosphere, hydrosphere and atmosphere
-involved photosynthesis, decomposition, respiration and carbonification
what is nitrogen cycle?
-atmospheric nitrogen is is converted to nitrogen oxides and deposited in the soil, is used by organisms and decomposed back to elemental nitrogen
what is nitrogen fixation?
-conversion of atmospheric nitrogen into ammonia and organic derivatives by soil microorganisms, made usable
