Lecture 4 - Prokaryote Cell Structure (Bacterial Cell)

Question 1

Since prokaryotes are small, what happens with the surface area/volume ratio?

Answer 1

• dilution problem = the plasma membrane is a selective barrier and only so much can pass through the ‘doors’ at once
• surface area increase by a factor of 2
• volume increase by a factor of 3
  note:
  surface area = membrane
  volume = cytoplasm

Question 2

What do eukarya have that increases surface area?

Answer 2

internal membranes

Question 3

Describe the bacterial cell structure

Answer 3

• NO membrane-bound organelles
• they have: cell membrane, cell wall, cytoplasm, ribosomes, fimbriae, flagella, DNA in a nucleoid region
• they perform all the functions of a eukaryotic cell without compartmentalization

Question 4

What do bacterial cells have to make them motile?

Answer 4

• flagellum = rotates like a corkscrew
• filament = polymer of flagellin (protein with quaternary structure)
• hook = rotation about the hook allows movement
• basal apparatus = anchor filament into the cell wall/membrane (contains a gear system that drives rotations and this energy for rotation comes from [H+] gradient

Question 5

What does the bacterial cell wall do?

Answer 5

• prevents osmotic lysis

- cell wall required for cell defense, permeability barrier, and for structure

Question 6

What are Gram-positive bacteria?

Answer 6

• thick layer of peptidoglycan -> PM (structural polysaccharide, a polymer of NAG and NAM which are monosaccharides)
• teichoic acid = molecules that link layers of PM
• lipoteichoic acid = links the cell wall to the membrane
• refer to notes for drawing

Question 7

What are Gram-negative bacteria?

Answer 7

• thin layer of peptidoglycan and an outer membrane

- refer to notes for drawing and more info

Question 8

What is the function of antibiotics?

Answer 8

• kill bacterial pathogen by targeting bacterial specific structures (ribosomes and cell walls)

Question 9

What are fimbrae?

Answer 9

• small hair-like structures that allow attachment to surfaces
• not present in all bacteria but often in pathogens

Question 10

What is biofilm?

Answer 10

• “slim cities”
• some bacteria secrete a mucous that surrounds the cell
• protects the cell from dehydration and allows attachment ( very difficult to remove )

Question 11

What is a microbiome?

Answer 11

• collection of organisms normally found on and in our bodies
• we are covered in trillions of microbes
• these are viewed as essential to our health

Question 12

What is colonization?

Answer 12

• establishment of microbial growth in host tissue
• begins at birth
• sources of colonizing bacteria: birth canal, feeding

Question 13

What are the purposes of normal flora?

Answer 13

1. protection from pathogens
2. required for developmental processes
3. provide vitamins and nutrients
4. aid in digestion
5. modulates the immune system

Question 14

What is the hygiene hypothesis?

Answer 14

• exposure to microbes helps maintain a healthy immune system
• lack of exposure to healthy microbes leads to hyperactive immune systems