Chapter 3: Bacterial Cell Structure

Question 1

Prokaryotes were originally defined in 1962 by the characteristics they lack compared to eukaryotes: they lacked (4)

Answer 1

• membrane-bound nucleus
• cytoskeleton
• membrane-bound organelles
• internal membranous structures (e.g. Golgi, ER)

Question 2

() proposed in 2006 that the term prokaryote should be abandoned

Answer 2

Norman Pace

Question 3

2 most common shapes of bacterial cells

Answer 3

1. cocci - spherical cells
2. rods - oblong cells

Question 4

types of bacterial cell arrangements

Answer 4

1. plane of division
2. whether they are separated or not

Question 5

cocci shape and arrangement

() divide and remain in pairs

Answer 5

diplococci (s. diplococcus)

Question 6

cocci shape and arrangement

in the genera Streptococcus, Enterococcus, and Lactococcus, cells divide on (1) to form (2)

Answer 6

1. 1 plane
2. chains

Question 7

cocci shape and arrangement

staphylococci divide on (1) to generate (2)

Answer 7

1. random planes
2. irregular, grape-like clusters

Question 8

cocci shape and arrangement

Bacteria in the genus Micrococcus often divide in two planes to form square groups of four cells called (1). In the genus (2), cocci divide in three planes, producing cubical packets of eight cells

Answer 8

1. tetrads
2. Sarcina

Question 9

other shapes and aggregations

rods, sometimes called (1) differ considerably in their (2)

Answer 9

1. bacilli
2. width-to-length ratio

Question 10

() is a type of rod bacteria that is short and wide, resembling cocci

Answer 10

coccibacillus

Question 11

other shapes and aggregations

other types of shapes/aggregations include:
1. () - comma chaped
2. () - rigid spiral-shaped
3. () - flexible spiral-shaped
4. () - characterized by networks of long filaments called (4a)
5. () - organisms that are variable in shape

Answer 11

1. vibrios
2. spirilla
3. spirochetes
4. mycelium
   4a. hyphae
5. pleomorphic

Question 12

size-shape relationship

cells want a high (1) -> increases efficiency of (2) and (3) within a cell.

Answer 12

1. surface area-to-volume ratio (S/V ratio)
2. nutrient uptake
3. diffusion of molecules

Question 13

size-shape relationship

for some bacteria, having a large size and/or odd shape may be a () from predation

Answer 13

protective mechanism

Question 14

common bacterial structures - internal

1. () - layers the surround the cell
2. () - innermost layer of (1)
3. () - chemically complex, covers (2)
4. () - internal compartment
5. () - where genetic material is localized

no single bacterium possesses all these structures at all times; some are found only in certain conditions or phases of the life cycle

Answer 14

1. cell envelope
2. plasma membrane
3. cell wall
4. cytoplasm
5. nucleoid

Question 15

common bacterial structures - external

1. () - filamentous structures that facilitate gene transfer or attachment to surfaces
2. () - commonly for motility

no single bacterium possesses all these structures at all times; some are found only in certain conditions or phases of the life cycle

Answer 15

1. pili (s. pilus)
2. flagella

Question 16

bacterial cell envelope

cell envelope - composed of the (1) and all of the (2) external to it

Answer 16

1. plasma membrane
2. surrouding layers

Question 17

bacterial cell envelope

the cell envelop commonly includes (3)

Answer 17

1. plasma membrane
2. cell wall
3. at least one additional layer:
   3a. capsule
   3b. slime layer

Question 18

plasma membrane functions

the plasma membrane encomapses the cytoplasm; it is a () that acquires nutrients and eliminates waste

Answer 18

selective permeable barrier

Question 19

plasma membrane functions

how the plasma membrane interacts with the external environment (3)

Answer 19

1. detects and responds to surrounding chemicals
2. serves as transport systems for nutrient uptake
3. location for metabolic processe (e.g. respiration, photosynthesis)

Question 20

plasma membrane structure is dynamic

most membrane-associated lipids are ()

Answer 20

amphipathic

Question 21

dynamic plasma membrane structure -> membrane proteins

2 types of membrane proteins have been identified based on their ability to be separated from the membrane:
1. () - loosely connected to the membrane and easily removed; comprise 20-30% of total membrane proteins
2. () - amphipathic proteins that are embedded within membrane and not easily removed

Answer 21

1. peripheral membrane proteins
2. integral membrane proteins

Question 22

plasma membrane proteins

characteristics of integral membrane proteins (3)

Answer 22

1. hydrophobic region buried in membrane lipids
2. hydrophilic regions project from surface
3. carry out important func’s like transport

Question 23

bacterial lipids

the plasma membrane is mainly composed of ()

Answer 23

phospholipids

Question 24

bacterial lipids - other smaller lipids in the plasma membrane

1. () - hydrophobic molecule similar to cholesterol
   a. () the bilayer, impacting fluidity and shape in membrane region
   b. form () that are platforms for protein complex assembly

Answer 24

1. hopanoids
   1a. distorts
   1b. functional membrane microdomains

Question 25

# bacterial cell wall cell wall functions: 1. maintains () of the bacterium 2. helps prottect the cell from () 3. may contribute to ()

Answer 25

1. shape 2. osmotic lysis and toxic materials 3. pathogenicity

Question 26

# bactrerial cell wall () - rigid strcuture lying outside the plasma membrane

Answer 26

peptidoglycan (murein)

Question 27

# bacterial cell wall 2 types of bacteria based on Gram stain 1. (a) - stain purple; (b) peptidoglycan 1.1. () - single membrane 2. (a) - stain pink or red; (b) 2.1. () - plasma membrane and an outer membrane revealed by TEM

Answer 27

1. (a) Gram-positive; (b) thick 1.1. monoderm 2. (a) Gram-negative; (b) thin peptidoglycan and outer membrane 2.1. diderm

Question 28

# peptidoglycan structure composed of 2 alteranting sugars:

Answer 28

1. N-acetylglucosamine (NAG) 2. N-acetylmuramic acid (NAM)

Question 29

# peptidoglycan structure aside from sugars, also contains ()

Answer 29

4 alternating D- and L-amino acids = stem peptide ## Footnote D-aas in the stemp peptide protects against degradation by most host peptidases

Question 30

# strands are cross-linked peptidoglycan strands have () shape

Answer 30

helical

Question 31

# strands are cross-linked peptidoglycan chains are crosslinked by peptides for strength: 1. () - connecting carboxyl and amino groups between amino acids 2. indirect crosslink - () may form

Answer 31

1. direct crosslink 2. peptide interbridge

Question 32

# Gram-positive cell walls composed primarily of peptidoglycan, but may also contain (1); which are (2) polymers that help (3)

Answer 32

1. techoic acids 2. glycerol 3. main tain the cell envelope (anchors cells wall to membrane) ## Footnote can be classified as wall tech. acids (linked PG), or lipotech. acids (linked to membrane)

Question 33

# Gram-positive cell walls other functions of techoic acids include:

Answer 33

- protect from environmental substances - may bind to host cells to initiate infection

Question 34

# Gram-negative cell wall basic structure - (1) compared to Gram-positive - consist of (2) surrounded by (3)

Answer 34

1. more complex 2. thin layer of peptidoglycan 3. outer membrane

Question 35

# Gram-negative cell wall basic structure outer membrane is composed of:

Answer 35

lipids, lipoproteins, and lipopolysaccharides (LPS) ## Footnote no techoic acids

Question 36

# Gram-negative cell walls The (1) lies outside the thin PG layer. (2) connect OM to PG, the latter of which lies in the (3), which differs from that in Gram+ cells

Answer 36

1. outer membrane 2. Braun’s lipoproteins 3. periplasmic space

Question 37

# LPS - lipopolysaccharide consists of 3 main parts: 1. () - major constituent; buried in the outer membrane 2. () - 10-sugar structure joined to (1) 3. () - polysaccharide that extends outward from the core

Answer 37

1. Lipid A 2. core polysaccharide 3. O side chain (aka O antigen) -> elicits immune response

Question 38

# functions of LPS - contributes to (1) on cell surface - helps (2) structure - creates a (3) - (4) protection - acts as an (5)

Answer 38

1. negative charge 2. stabilize outer membrane 3. permeability barrier 4. host defense 5. endotoxin

Question 39

# Gram- membrane transport 2 step process facilitated by (a): 1. solute () into the periplasm 2. crosses the ()

Answer 39

a. porins 1. crosses OM 2. plasma membrane

Question 40

# cell walls and osmotic protection in () environments: - solute concentration outside cell < conc. inside cell - water moves into cell, causing swelling (lysis)

Answer 40

hypotonic

Question 41

# cell walls and osmotic protection in (1) environments: - solute conc. outside cell > conc. inside cell - water leaves, cell shrivels up -> (2)

Answer 41

1. hypertonic 2. plasmolysis

Question 42

# evidence for protection of cell wall - (1) breaks the bond between NAG and NAM - (2) inhibits peptidoglyan synthesis - if cells are treated with either of the above, they (3)

Answer 42

1. lysozyme 2. penicillin 3. lyse in a hypotonic solution

Question 43

# extracellular vesicles (EVs) 1. Gram-positive EVs are made of the () 2. Gram-negative EVs are made of (a); sometimes called (b)

Answer 43

1. plasma membrane surrounding a small amount of cytoplasm 2. (a) LPS-containing OM containing a sample of periplasm; (b) outer membrane vesicles (OMVs) ## Footnote for OMVs, the outer membrane needs to dissociate from Braun's lipoprotein before the vesicles are formed

Question 44

# EVs are not cells - they do not (1) - can carry some ATP but do not have the ability to conserve energy - they play roles in (2)

Answer 44

1. reproduce 2. cell-cell interactions

Question 45

# external cell wall components - capsules - capsules are well organized and (1) from cells - usually composed of (2)

Answer 45

1. not easily removed 2. polysaccharides -> not easily washed away

Question 46

# external cell wall components - capsules protective advantages of capsules: 1. resistant to () 2. protect from () 3. exclude ()

Answer 46

1. phagocytosis 2. desiccation 3. viruses and detergents (toxic) ## Footnote capsules not necessarily req'd for culture, but may have benefits

Question 47

# external cell wall components - slime layers - similar to capsules, except they are diffuse, unorganized, and (1) - slime may facilitate (2)

Answer 47

1. easily removed 2. motility (i.e. in gliding bacteria)

Question 48

# external cell wall components - s layers S layers are regularly structured (1) layers of protein or glycoprotein - in Gram-, S layers non-covalently adhere to (a) - in Gram+, S layers are associated with (b)

Answer 48

1. self-assembling a. outer membrane b. peptidoglycan

Question 49

# external cell wall components - s layers S layer functions: 1. () ion and pH fluctuations, osmotic stress, enzymes, and predation 2. maintains () 3. promotes () 4. protects from () 5. protential use in ()

Answer 49

1. protects from 2. shape and rigidity 3. adhesion to surfaces 4. host defenses 5. nanotechnology

Question 50

# bacterial cytoplasmic structures - (1) - plasma membrane and everything within - (2) - material bounded by (1) - (3) - liquid component of (2)

Answer 50

1. protoplast 2. cytoplast 3. cytosol

Question 51

# bacterial cytoplasmic structures molecules dissolved in the cytosol include inclusions, ribosomes, plasmids, etc.; the high concentrations of these molecs and their precursors (+ metabolites) creates a phenomenon known as ()

Answer 51

macromolecular crowding ## Footnote bacterial cytoplasm is 10x more viscous that water, affecting processes like diffusion

Question 52

# bacterial cytoskeleton homologs of the ff eukaryotic cytoskeletal elements have been indentified:

Answer 52

actin filaments, microtubules, intermediate filaments

Question 53

# bacterial cytoskeleton functions are similar as those in eukaryotes: 1. participate in () 2. localize () 3. maintain ()

Answer 53

1. cell division 2. proteins 3. cell shape

Question 54

# best studied examples of bacterial cytoskeleton molecules 1. () - actin homolog, found in many rods where it maintains shape by positioning PG synthesis machinery 2. (a) - intermediate filament homolog maintains (b) shape 3. (a) - tubulin homolog found in many bacteria; forms (b) that constricts as daughter separates

Answer 54

1. MreB 2. (a) CreS; (b) curve 3. (a) FtsZ; (b) ring at center of a dividing cell

Question 55

# intracytoplasmic membranes -> plasma membrane infoldings - observed in many (1) bacteria - observed in many bacteria with high (2) - may be aggregates of (3)

Answer 55

1. photosynthetic 2. respiratory activity (e.g. nitrifying) 3. spherical vesicles ## Footnote internal membranes differ from PM by being enriched for molecules involved in energy conservation

Question 56

# inclusions - formed by (1) - primary function is to (2) cellular components so that they do not diffuse freely in the cytoplasm - may be in the form of (3) that are stockpiled by the cell for future use

Answer 56

1. aggregation of organic or inorganic substances 2. segregate 3. granules, crystals, or globules of organic/inorganic material

Question 57

# inclusions some are enclosed by a single-layered protein or lipid shell - may be referred to as (1) - often used to (2)

Answer 57

1. microcompartments 2. sequester enzymes that produce toxic intermediates ## Footnote may also be useful when one intermediate is ready but others are not

Question 58

# microcompartments (example) (1) - CO2 fixing bacteria - contain the enzyme (2) that release CO2 into a shell so it accumulates into high concentration - then (3) makes sugar

Answer 58

1. Carboxysomes 2. carbonic anhydrase 3. RuBisCo

Question 59

# gas vacuoles - involved in (1) - provide (2) to aquatic bacteria - made of aggregates of hollow, cylindrical (3)

Answer 59

1. bacterial movement 2. buoyancy 3. gas vesicles - impermeable to water, but freely permeable to atmospheric gases

Question 60

# magnetosomes - also found in aquatic bacteria - magnetite particles inside are helpful for (1) in Earth's magnetic field - cytoskeletal protein (2) helps form magnetosome chain

Answer 60

1. orientation 2. MamK

Question 61

# ribosomes complex protein/RNA structures - sites of (1) - bacterial and archaea ribosomes are typically (2) bacterial ribosomal RNA (rRNA): - (3) rRNA in small subunit - (4) rRNAs in large subunit

Answer 61

1. protein synthesis 2. 70S ribosomes 3. 16S 4. 23S and 5S

Question 62

# nucleoid - usually not membrane-bound, though there are a few exceptions - location of (1) - usually 1 closed circular, dsDNA molecule - (2) aid in folding and structure

Answer 62

1. chromosome and associated proteins 2. supercoiling and nucleoid(-associated) proteins (NAPs)

Question 63

# plasmids plasmids are extrachromosomal DNA that are usually (1) - (2) independently of chromosome - episomes are able to (3) ## Footnote may carry genes that can confer a selective advantage in some situations

Answer 63

1. small, closed, circular DNA molecules 2. exist and replicate 3. integrate into

Question 64

# external structures extend beyond bacterial cell envelope - function in (4)

Answer 64

protection, attachment to surfaces, horizontal gene transfer, cell movement

Question 65

# pili and fibriae pili and fibriae (categrized depending on func./ size, etc) - short, thin, hair-like protein appendages (abt 1k/cell) - can mediate (1) sex pili - longer, thicker, less numerous (10/cell) - genetically encoded on plasmids - required for (2)

Answer 65

1. attachment to surfaces, motility, and DNA uptake 2. conjugation - DNA transfer to different cell

Question 66

# flagella flagella are threadlike, locomotor appendages extending outward from plasma membrane and cell wall; functions include ()

Answer 66

- motility - attachment to surfaces - server as virulence factors -> contribute to pathogenicity

Question 67

# flagella Patterns of flagella distribution: - (1) —one flagellum. -- (1a) —flagellum at end of cell. - (2)—one flagellum at each end of cell. - (3)—cluster of flagella at one or both ends. - (4)—spread over entire surface of cell.

Answer 67

1. Monotrichous 1a. polar flagellum 2. Amphitrichous 3. Lophotrichous 4. Peritrichous

Question 68

# bacterial flagella Thin, rigid protein structures that cannot be observed with bright-field microscope unless specially stained. Ultrastructure composed of 3 parts: * (1)—extends from cell surface to the tip. * (2)—embedded in cell envelope. * (3)—short curved segment.

Answer 68

1. Filament 2. Basal body 3. Hook

Question 69

# flagella synthesis Complex process involving many proteins. * New flagellin molecules transported through the hollow filament. * Filament subunits () with help of filament cap at tip, not base.

Answer 69

self-assemble

Question 70

# bacterial motility 5 Major types of bacterial movement; the first 3 of which are conferred by flagella

Answer 70

1. swimming 2. swarming 3. spirochete motility 4. twitching 5. gliding

Question 71

# bacterial motility () - movement towards chemical attractants (nutrients) and away from repellants (toxic materials)

Answer 71

chemotaxis

Question 72

# swimming flagellum rotates like a propeller - rapid rotation (up to 1100 rev/sec) in general: - CCW rotation causes (1) - CW roation causes (2)

Answer 72

1. run - forward motion 2. tumble - disrupt run, stop

Question 73

# swarming -> useful for colony morphology - occurs when cells (1) - most swarmers have (2) flagella - commonly, the cell produces a molecule tha lowers (3)

Answer 73

1. move in unison across a moist surface 2. peritrichous 3. surface tension (surfactant)

Question 74

# spirochete motility characterized as (1) - multiple flagella form (2) which winds around the cell - flagella remain (3) - (4) shape exhibits flexing and spinning movements

Answer 74

1. undulation of entire cell 2. axial fibril 3. inside of the cell wall 4. corkscrew

Question 75

# twitching and gliding motility - occurs on solid surfaces - do not involve (1) - may involve (2) twitching motility - involve (3) - short intermittend, jerky motions - cells are in contact with each other and surface gliding - smooth movements that (4)

Answer 75

1. flagella 2. Type IV pili and slime 3. pili at ends of cell (Type IV) 4. don't require appendages

Question 76

# chemotaxis - chemical attractants and repellants bind (1) that transmit signals throughout the chemosensing system - in presence of attractant/repellant, (2) - behavior of bacterium altered by temporal concentration of chemical

Answer 76

1. chemoreceptors 2. tumbling frequency is reduced; rtuns toward/away from comound are longer