Lecture 3 Flashcards
How are prokaryotes different from eukaryotes?
lack of nucleus and histones
the makeup of their cell wall
lack of membrane-bound organelles
What do all prokaryotic bacterial cells possess?
a cell membrane
cytoplasm
ribosomes
a cytoskeleton
one chromosome
May be a few in some prokaryotes
What do most prokaryotic bacterial cells possess?
a cell wall
a glycocalyx
What do some prokaryotic bacterial cells possess?
flagella, pili, and fimbriae
an outer membrane
plasmids
inclusions
endospores
intracellular membranes
What is pleomorphism?
when cells of one species vary in shape and size caused by variations of the cell wall structure
What are the 3 bacterial shapes?
Coccus (circular), Rod (rectangle with round edges), spiral
What are flagella?
used for bacterial movement
360o rotation
Flagellar structure differs between Gram positive and Gram negative cells due to differences in cell wall structure
What are the 4 flagellar arrangements?
- Monotrichous
- Lophotrichous
- Amphitrichous
- Peritrichous
What is mono trichous?
single flagellum
What is lophotrichous?
small bunches or tufts of flagella
What is amphitrichous?
flagella at both poles of the cell
What is peritrichous?
flagella dispersed randomly over the surface of the cell
How do bacteria move?
in response to chemical signals
What happens when a cell “runs”? (bacterial movement?)
- smooth linear movement toward a stimulus
- positive
What happens when a cell “tumbles”? (bacterial movement?)
- flagellar rotation reverses, causing the cell to stop and change its course
- negative
What are fimbriae used for??
used for attachment
What are pili used for?
used for attachment and genetic exchange during
What is glycocaylx?
Sticky layer composed of polysaccharides (sugars), proteins or both
Varies in thickness, can be either a slime layer or capsule
Used to avoid phagocytosis, and for adhesion (biofilms)
What is the capsule of a cell?
Bound more tightly to the cell, denser and thicker than a slime layer
What is the slime layer?
Loosely attached to cell surface Attachment and prevents drying Helps trap nutrients near the cell Formation of biofilms All bacteria have at least a very thin slime layer
Where is the cell envelope?
outside of the cytoplasm
What is the cell envelope composed of?
cell wall
cell membrane
outer membrane in some bacteria
What is a peptidoglycan cell wall?
Repeating framework of long glycan (sugar) chains cross-linked by short peptide (protein) fragments
Present in most bacteria
Provides strength to resist rupturing (lysis) due to osmotic pressure
What are 3 characteristics of a gram positive cell?
Thick peptidoglycan
Teichoic acid, lipoteichoic acid
One membrane involved
What are 3 characteristics of a gram negative cell?
Thin peptidoglycan layer surrounded by two phospholipid membranes (outer membrane and cell membrane
Lipopolysaccharide and porins in outer membrane
Periplasmic space
Where is the only place an outer membrane is found?
Gram negative bacteria
What is the outer membrane composed of?
composed of bilayer of phopholipids inside and lipopolysaccharide (LPS) outside
Pores
Where is only periplasm found?
gram negative bacteria
What is periplasm?
Extra cellular compartment
Enzymes to break down nutrients
Proteins to bind nutrients for transport
Who was the gram stain found by?
Hans Christian gram
What is the cell membrane?
A lipid bilayer with proteins embedded
bacterial cell membranes contain primarily phospholipids (30%–40% of the membrane mass) and proteins (60%–70% of the membrane mass)
What does the cell membrane provide?
Provides a site for reactions
contains enzymes of respiration and ATP synthesis since prokaryotes lack mitochondria
What is a major action of the cell membrane?
A major action of the cell membrane is to regulate the passage of nutrients into and out of the cell – selectively permeable
What is the cytoplasm composed of?
70-80% water
Soluble proteins, salts, carbohydrates
Site of nearly all chemical reactions
Contains the DNA in the nucleoid
Is the nucleoid membrane bound?
No
Where is bacterial DNA found?
Nucleiod
How does DNA exist in bacteria?
DNA of most bacteria exists in the form of a single circular bacterial chromosome
What does the prokaryotic ribosome do?
Translates mRNA into proteins
What is the cytoskeleton?
Peptidoglycan layer determines shape of many bacteria
What genuses are bacterial endospores found in?
Bacillus and Clostridium
Are bacterial endospores highly resistant?
yes
What are the 4 major divisions of prokaryotic bacteria based on cell wall structure?
- Gracilicutes
- Firmicutes
- Tenericutes
- Mendosicutes
What is gracilicutes?
gram-negative cell walls and thus are thin-skinned
What are firmicutes?
gram-positive cell walls that are thick and strong
What are tenericutes?
lack a cell wall and thus are soft
What are mendosicutes?
archaea with unusual cell walls
What is the percent of genes all bacteria share?
70 - 80
