Exam 2 Bacteria & Archaea 9/28

Question 1

Bacteria can take many different shapes

Answer 1

Spherical (s. coccus, pl. cocci)
Rod-shaped (s. bacillus, pl. bacilli)
Comma-shaped (s. vibrio, pl. vibrios)
Spiral (s. spirillum, pl. spirilla)
Pleiomorphic (varied shapes)

Question 2

Vibiancy

Answer 2

Dormancy mechanism caused by stress, lowering metabolism to sleeping state

Question 3

Bacteria can also assume multicellular organizations

Answer 3

Hyphae (branching filaments of cells)
Mycelia (tufts of hyphae)
Trichomes (smooth, unbranched chains of cells)

Question 4

Size of bacteria can vary greatly

Answer 4

Usually smaller than eukaryal cells

SMALL eukaryal cells are usually >5 μm in diameter

Question 5

The cytoplasm

Answer 5

Liquid/gel environment where all metabolic and functional activity occurs

Question 6

The Nucleoid (nuclear region)

Answer 6

irregularly shaped region in bacteria and archaea

usually not membrane bound (few exceptions)

location of chromosome and associated proteins

supercoiling

nucleoid proteins (HU)

Question 7

Plasmids

Answer 7

extrachromosomal DNA

exist and replicate independently of chromosome

episomes

contain few genes that are non-essential

May exist in many copies in cell

Inherited stably during cell division

Can be lost during cell division

Classification of plasmids based on mode of existence, spread, and function

Question 8

Ribosomes

Answer 8

complex structures

entire ribosome
*bacterial and archaea ribosome = 70S
*eukaryotic (80S) S = Svedburg unit

^*(note: eukaryotic are slightly larger than bacterial and archaea ribosomes)

bacterial and archaeal ribosomal RNA
16S small subunit = 30S
23S and 5S in large subunit = 50S
archaea have additional 5.8S in large subunit (also seen in eukaryotic large subunit)

proteins vary

Question 9

The cytoplasm

What else is in the cytoplasm of bacterial cells?

Answer 9

A stew of macromolecules

Inclusion bodies may also be present
Polyhydroxybutyrate granules
Sulfur globules
Gas vesicles
Carboxysomes
Magnetosomes

Question 10

Inclusions

Answer 10

Common in all cells

granules of organic or inorganic material

some are enclosed by a single-layered membrane

storage of nutrients, metabolic end products, energy, building blocks

Question 11

Magnetosomes

Question 12

bacterial cytoskeleton

Answer 12

The cytoskeleton is a series of internal proteins
Keeping everything in the cell
Move things to the right locations in cells.

Some cytoskeleton proteins are involved in cell wall synthesis during cell division (FtsZ and MreB).

Other cytoskeletal proteins are involved in moving internal items (e.g., plasmids, magnetosomes).

Question 13

Bacterial Cell Envelope

Answer 13

Plasma membrane
Cell wall
Layers outside the cell wall

Question 14

The plasma membrane

Answer 14

ALL cells have a plasma membrane (PM).

Interior/exterior

Usually composed of a phospholipid bilayer with embedded proteins

Question 15

Plasma Membrane Functions

Answer 15

encompasses the cytoplasm

selectively permeable barrier

interacts with external environment

Question 16

Bacterial Lipids

Answer 16

The PM may have sterol molecules called “hopanoids” in it to help with stability across temperature ranges

Question 17

Membrane Proteins

Answer 17

peripheral
- loosely connected to membrane
- easily removed
- Make up 20 – 30% of membrane proteins

integral
- amphipathic
- Carbohydrates often attached
- carry out important functions
- Can move laterally in the membrane
- may exist as microdomains (patchwork)

Question 18

Membrane Proteins Functions

Answer 18

ATP production/energy production

Transportation through the membrane

Question 19

The plasma membrane: getting things in

Answer 19

O2 and CO2 - diffuse across readily

H2O – aquaporins

Osmosis is the flow of water across the PM toward the side with a higher solute concentration.

Question 20

How do organisms take up nutrients?

Answer 20

Microbes can only take in dissolved particles across a selectively permeable membrane

Must be able to take up specific molecules

Must concentrate nutrients against a gradient

microorganisms have developed a number of different transport mechanisms to accomplish this
facilitated diffusion – all microorganisms
active transport – all microorganisms
group translocation – Bacteria and Archaea
endocytosis – Eukarya only

Question 21

Passive Diffusion

Answer 21

molecules move from a region of higher concentration to one of lower concentration between the cell’s interior and the exterior

Not energy dependent

The rate of diffusion depends on the concentration gradient

H2O, O2, and CO2 often move across membranes this way

Question 22

Facilitated Diffusion

Answer 22

similar to passive diffusion

movement of molecules is not energy dependent

direction of movement is from high concentration to low concentration

size of concentration gradient impacts rate of uptake

differs from passive diffusion

uses membrane bound specific carrier molecules

smaller concentration gradient is required for significant uptake of molecules

A concentration gradient spanning the membrane drives the movement of molecules

Is reversible depending on concentration of molecules

The gradient can be maintained by transforming the transported nutrient into another compound

effectively transports glycerol, sugars, and amino acids

more prominent in eukaryotic cells than in bacteria or archaea

No energy required

Not useful to bacteria and Archaea that live in environments with low concentrations of nutrients

Question 23

rate of facilitated
diffusion

Answer 23

rate of facilitated
diffusion increases
more rapidly and
at a lower
concentration

diffusion rate
reaches a plateau
when carrier
becomes
saturated

Question 24

Active Transport

Answer 24

energy-dependent process

move molecules against a gradient

concentrates molecules inside cell

involves specific carrier proteins (permeases)

Question 25

Types of Active Transport

Answer 25

3 types: Primary, Secondary, Group Translocation

Primary Active Transporters (ABC Transporters) – use energy provided by ATP hydrolysis to move substances against a conc gradient

Secondary Active transporters (major facilitator superfamily MFS Transporters) – couple the potential energy of ion gradients to transport substances

Question 26

ABC Transporters

Answer 26

primary active transporters use ATP

ATP-binding cassette transporters

observed in Bacteria, Archaea, and eukaryotes

Consist of :
2 hydrophobic membrane spanning transporter proteins
2 cytoplasmic associated ATP-binding domains

Considered to be uniport – transports one molecule at a time

Question 27

ABC Transporter Function

Answer 27

Leads to ATP hydrolysis which provides energy for opening channel and movement of solute

Question 28

Secondary Active Transport

Answer 28

major facilitator superfamily (MFS)

uses ion gradients to co-transport substances
symport - two substances both move in the same direction
transport of lactose using lactose permease in E. coli transports lactose and a proton simultaneously into the cell

antiport - two substances move in opposite directions
transport of sugars and amino acids in E. coli while pumping sodium out