Cell structure midterm 2

Question 1

What is the difference between nucleoid, nucleus, nucleolus

Answer 1

Nucleoid
- Prokaryotic cell, where the circular DNA is, it is concentrated

Nucleus
- In a eukaryotic cell

Nucleolus
- Inside the nucleolus in the eukaryotic cell
- Main function is ribosome synthesis, ribosomes are made in the nucleolus
- Ribosome is made of protein and DNA, RNA specifically, all RNA is made in the nucleus, DNA is made in the cytoplasm
- mRNA is for translation, to bring the ribosomes out of the nucleus in order to make DNA

Question 2

what are the bacterial cell envelope and their phyla?

Answer 2

1. Gram negative
   - has a thin cell wall
   - but has both the inner and outer cell membrane
   - Phyla: Proteobacteria
2. Gram positive
   - has a thick and firm cell wall but has no outer membrane
   - Phyla: Firmicutes

Question 3

what is the cell wall made of?

Answer 3

Peptidoglycan (murein)

Question 4

How is the cell wall linked together?

Answer 4

the glycan chains are cross-linked via short peptide bonds by a enzyme called transpeptidase

peptide bond attaches to the DAP –> D-ala and it cleaves off the other D-ala

Question 5

What are the types of amino acids in bacteria?

Answer 5

4 types

1. L-Alanine (L-ala)
   these are unique to bacteria
2. D-Glutamic acid (D-Glu)
3. Diaminopimelic acid (DAP)
4. D-Alanine (D-ala)

Question 6

How does lysozyme work?

Answer 6

It is part of your immune system, innate
it washes things out
it is a protein, enzyme that cleaves the glycan backbone, so this prevents the formation of cell wall

it targets bacteria with a more exposed cell wall (gram positive cells)

gram negative cells have plasma membrane that protects them from things like lysozyme

Question 7

What does transpeptidase do?

Answer 7

it moves the amino acid from one amino to another amino acid

they cross link the glycan together, so they shift the amino acids to create a peptide bond

Question 8

What do gram positive cells have?

Answer 8

Teichoic acids and lipoteichoic acid

S layer

no outer membrane

Question 9

what is teichoic acids and lipoteichoic acids?

Answer 9

Teichoic acids are chains of glycerol linked by phosphodiester bonds (anionic)
it provides strength

Question 10

What is a S-layer?

Answer 10

tough layer outside of the peptidoglycan wall, many copies of a single protein

some archaea and gram negative bacteria have it

Question 11

what is the periplasm?

Answer 11

it was inbetween the inner membrane and cell wall of both the gram negative and positive cell

Question 12

What does the periplasm contain?

Answer 12

6 things

2 proteins
- receptor proteins
- nutrient-binding proteins

3 enzymes
- digestive enzymes
- detoxifying enzyme
- enzyme for cell wall assembly

1 system
- secretion system

Question 13

What does the gram negative bacteria contain?

Answer 13

Porin
- Membrane transport proteins which allow in hydrophilic molecules

Lipopolysaccharide phospholipid
- only found in the outer leaflet

Question 14

What is the structure of lipopolysaccharide?

Answer 14

Top to bottom:
repeating O antigens

Chain of 5-sugars, core polysaccharides

Lipid A, fatty acids
- endotoxin

Question 15

What are repeating O antigens

Answer 15

hydrophilic
sugar vary
antigenic, causing an immune system to recognize it
specific to the bacteria
creates protection

Question 16

What are lipid A

Answer 16

two sugars
fatty acids
highly toxic, if you get infected with a gram negative bacteria you will have very specific symptoms
endotoxin (internal)

Question 17

What are the gram negative bacteria infection symptoms?

Answer 17

Intravascular coagulation (blood clots in blood vessels)
hemorrhage (bleeding)
shock

Question 18

What do lipopolysaccharides do?

Answer 18

activate macrophages
- this causes pyrogens (fever)
- macrophages are white blood cells and they are highly sensitive to endotoxins and so they release pyrogens

activate complement cascade
- this causes inflammation
- it is made up of proteins so one protein activates another and another

Question 19

what are acid fast bacteria and what is their genus?

Answer 19

mycobacterium (genus)
they cause tuberculosis and leprosy and they stain differently than other bacteria

they have no outer membrane like gram positive bacteria but they have mycolic acid which is a hydrophobic waxy surface and thus the stain cannot enter

thick cell walls and mycolic acid makes it hard to stain

Question 20

How do you stain mycobaterium

Answer 20

the acid fast staining procedure, 3 steps

1. use heat to drive pink stain into cell
   -They don’t let the stain come out
2. decolorized with acid-alcohol
   -it takes the stain out of everything else but not the mycobacterium
3. counterstain with methylene-blue
   - Why will this not stain the mycobacteria, because we are not heating it up so the stain will not go in
   - Gram positive and gram negative will always looks blue (it will stain everything)

Question 21

what does flagella do and what are the different types?

Answer 21

it enables bacteria to swim
it is made up of flagellin protein

there’s 4 types of structures
1. Monotrichous
- one flagella

2. Lophotrichous
   - multiple flagella at one end
3. Amphitrichous
   - flagella at both ends
4. Peritirichous
   - flagella everywhere

Question 22

How does flagella move and what makes it move?

Answer 22

To move straight it must move counter clockwise thus all the flagella (if it has multiple) must move to one side and move in the same direction

if the flagella moves clockwise it will tumble

The flagella moves to where the chemical signal via chemotaxis

Question 23

What is chemotaxis?

Answer 23

A chemical signal that the bacteria is drawn to and they start swimming, but if the signal gets stronger than it keep running until the signal gets weaker

then they tumble and pick a random direction and hope they ran correctly

Question 24

What is phototastic

Answer 24

bacteria that are drawn to light