Week 2- Bacterial Physiology

Question 1

Bacterial Cytoplasmic contents

Answer 1

• DNA
• Ribosomes
• Cytoskeleton
• Inclusions and microcompartments
• Endospores

Question 2

Nucleoid

Answer 2

The genome and its proteins.

DNA is folded using histones so that it can fit properly , and be organized in the cell.

Bacterial DNA is circular with an origin of replication, the replication starting point

Question 3

Plasmids

Answer 3

Plasmids are small circular DNA independent of the genomic DNA. They replicate separately and carry non-essential genes. There can be many copies of plasmids in one bacterial cell.

They can give antibiotic resistance, transfer DNA to other cells, or confer virulence genes

Question 4

Ribosomes

Answer 4

Help turn RNA to protein in the cell. Bacteria have a 50s and 30s ribosomal subunit.

Question 5

Tubulin Homologs

Answer 5

FtsZ and TubZ

FtsZ is used in cell divison, a ring is formed in the middle of the cell to help it separate

TubZ is used for the segregation of plasmids

Question 6

Actin Homologs

Answer 6

Mamk and MreB

MamK is used in magnetic bacteria, to help position the bacteria to earths magnetic field.

MreB is used in cell shape/polarity, its found in rod shaped bacteria. Helps recruit proteins that shape the cell.

Question 7

Intermediate Filament homologs

Answer 7

CreS used for cell shape, causes a curve to form in rod shaped bacteria. It can be found on the concave side of the cell.

Question 8

Bacteria specific cytoskeleton : What is MinD ?

Answer 8

MinD prevents FtsZ from polymerizing at the end of the cell so division happens correctly, in the middle of the cell and not at the end of the cell.

Question 9

Inclusions

Answer 9

Found inside the bacteria they usually contain organic/ inorganic material

used as a storage reserve for nutrients/ metabolites

Question 10

B-hydroxybutyrate (PHB)

Answer 10

A carbon reservoir.

A lipid that is formed from B-hydroxybutyrate

polymer is formed by ester links and the polymers aggregate to form granules.

granules are made when carbon is in excess and they are used when carbon levels are low

Question 11

Polyphosphate and sulfur

Answer 11

reservoir of phosphate and sulfur

granules are formed when phosphate is in excess, can be used as a source of phosphate for proteins, lipids and in the formation of ATP.

Sulfur is used for amino acids such as cystine and in the formation of iron/sulfur clusters

Question 12

Carboxysome

Answer 12

Collect Co2 in high concentrations to help increase the efficiency of rubisco enzyme.

Bicarbonate is converted to Co2 and water, the Co2 gets trapped in the carboxysome and rubisco can easily access it

Question 13

Gas Vesicles

Answer 13

Used in water bacteria such as cyanobacteria to help them stay afloat (gives buoyancy),

made of proteins they are long and narrow, hollow and rigid, gas filled structures.

Question 14

Magnetosomes

Answer 14

Not a microcompartment, they are made of lipids rather than proteins.

made of magnetic iron oxides. They allow bacteria to move along earths magnetic field.

The membrane is enclosed.

Question 15

Endospores

Answer 15

Bacterial “seeds”

produced in unfavorable environments
contain genetic info to grow
resistant to desiccation (drying), chemicals, and antibiotics

Question 16

Plasma Membrane Facts

Answer 16

• common to all bacteria
• separates environment from cytoplasm
• has a phospholipid bilayer
• fluid, it moves

Question 17

Role of Plasma Membrane

Answer 17

1. Selectively permeable: only some molecules can enter
2. Anchors proteins: membrane is full of proteins that perform key functions
3. Creates a Proton Motive Force (PMF) with high H+ on the outside and low H+ inside

Question 18

Components of Phospholipids

Answer 18

Have a hydrophilic head with phosphate and glycerol and a hydrophobic tail made of fatty acids

A long chain of carbons

Question 19

Acyl chains affect membrane fluidity

Answer 19

Saturated: have no double bonds and form a rigid membrane

Unsaturated: have double bonds and create a fluid membrane

• high temp also creates a more fluid membrane

Question 20

Undecaprenyl pyrophosphate

Answer 20

• Essential in bacteria to form peptidoglycan.
• the 2 phosphate groups carry energy
• made of isoprene units ( prenyl)
• a carrier molecule
• same as bactoprenyl pyrophosphate

Question 21

Integral membrane Proteins

Answer 21

Are embedded in the plasma membrane, and help molecules go through.

1. Monotopic alpha helix- Crosses the membrane once
2. Polytopic alpha helices- Crosses the membrane more than once, can form a structure with a hole in the middle for proteins to go through.  3. Polytopic beta barrel : Beta sheets which form a beta barrel with a hole in the center for proteins to go through.

Question 22

Peripheral Membrane Proteins

Answer 22

Stay on the surface of the membrane, can anchor to the heads (ionic) or the fatty acid (acetylated) tails.

1. Alpha helix
2. Loop(s)
3. Acylated, the acyl group helps anchor the protein to the membrane due to it being hydrophobic
4. Ionic, helps anchor the protein to the membrane due to it being hydrophilic

Question 23

Diffusion

Answer 23

Free movement of molecules along a concentration gradient, that doesn’t require energy (passive).

small, non- polar, water, O2, Co2, can pass through

ions, polar, large molecules can’t pass through

Question 24

Osmosis

Answer 24

The movement of water along a concentration gradient, can exert a physical force on the membrane.

Hypertonic: There is more water in the cell than the environment so water leaves the cell and it shrinks.

Isotonic: No net movement, water is the same in and outside the cell.

Hypotonic: More water outside the cell than inside so water enters the cell making it large and the cell will burst.

Question 25

Facilitated Diffusion

Answer 25

Movement of molecules along a concentration gradient that requires a protein carrier. Passive.

• The transporters/carriers are selective for particular substrates
• Movement rate is limited by the number of transports
• Transporters move ions, sugars and amino acids

ex) Potassium channel w/ 8 alpha helices that form a barrel with a hole in the middle.

Question 26

What type of Simple Transporters are there and how do they work ?

Answer 26

• Can go against the concentration gradient, utilizes the PMF

Uniporters: facilitated diffusion, can go into or out of the cell in one direction carrying one molecule.

Symport: Two molecules go in or out of the cell in the same direction, using energy from the PMF they can go against the concentration gradient.

Antiport: Two molecules go in or out of the cell in opposite directions using energy from the PMF they can go against the concentration gradient.

Question 27

Glucose Transport

Answer 27

Glucose is transported using facilitated diffusion. The glucose is modified by adding on a phosphate, this helps keep the concentration of glucose low in the cell so that more glucose can be brought in.

Enzymes help to modify glucose

once glucose enters and is modified it is too big and too charged to exit the cell.

Question 28

Active Transport

Answer 28

Movement of molecules against a concentration gradient that requires a protein carrier. Requires energy in the form of ATP (active)

Transporters are selective for particular substrates

Movement rate is limited by the number of transporters

Used to pump nutrients into the cells and harmful substances out of the cell.

Question 29

ATP Binding Cassette (ABC) Transporters

Answer 29

A common form of active transport.

Can be activated by substrates , and the corresponding binding protein.

Has 2 transmembrane domains and 2 nucleotide binding domains

NBD (nucleotide binding domain) uses ATP as an energy source, ATP is hydrolyzed and a conformational change occurs.

Go from inward to outward facing opening.