Cell Structure and Function Flashcards
What are the major components of peptidoglycan? (2)
- Complex polysaccharide composed of 2 alternating sugars
- Cross bridges of short proteins that hold the chains of sugars together
Peptidoglycan is structurally similar to ______
Glucose
Name the 2 modified sugars found in peptidoglycan
- n-acetylglucosamine (NAG)
- n-acetylmuramic acid (NAM)
How are the 2 modified sugars found in peptidoglycan arranged / positioned?
Alternating position
How are the carbohydrate chains in peptidoglycan connected to other chains of carbohydrates?
Tetra- / penta- peptides between neighboring NAMs
What are tetra- / penta- peptides?
Cross bridges of short proteins
What peptidoglycan component do tetra- / penta- peptides attach?
Hold chains of NAG and NAM together
Differentiate between the ‘peptido’ and the ‘glycan’ portions of peptidoglycan
- ‘Peptido’ = peptide cross bridges
- ‘Glycan’ = NAG / NAM carbohydrate chains
Compare and contrast gram-positive cell walls with gram-negative cell walls
- Gram-positive cell walls - thick layer of peptidoglycan
- Gram-negative cell walls - thin layer of peptidoglycan and an outer membrane (bilayer)
Where are teichoic acids found?
The outer thick layer of peptidoglycan in gram-positive cell walls
Teichoic acids are ______ linked to lipids
Covalently
What is the function of lipoteichoic acid in gram-positive bacteria?
Anchors the peptidoglycan to the cytoplasm membrane
What color do gram-positive bacteria stain after performing the gram stain?
Purple
What is a ‘bilayer’?
The outer membrane of gram-negative cells walls composed of two different layers
Differentiate between the inner leaflet and the outer leaflet of the outer membrane of gram-negative bacteria in terms of basic composition
- Inner leaflet - composed of phospholipids
- Outer leaflet - composed of lipopolysaccharide (LPS)
What unique component is found in the outer leaflet of the outer membrane of gram-negative bacteria?
Porins
What are porins?
Integral proteins that form channels through both leaflets of the outer membrane
What role do porins play in gram-negative bacteria?
Allow midsize molecules (such as glucose) to move freely across the outer membrane
What 2 major components make up lipopolysaccharide (LPS)?
- Lipids
- Sugar
Describe the relationship between lipid A, core polysaccharide, and O-specific side-chain components of LPS
Shock-inducing lipid A is attached to a core polysaccharide with variable O-specific side chains
What is lipid A?
Lipid portion
Where is lipid A found?
Inside gram-negative cells (endotoxin)
What symptoms / physiological conditions does lipid A cause inside in host organisms? (5)
- Vasodilation
- Fever
- Inflammation
- Blood clotting
- Shock
Describe endotoxin
Dead gram-negative cells release lipid A when the outer membrane disintegrates
Where is endotoxin found?
Inside gram-negative cells
Explain how the outer membrane of gram-negative bacteria can be an impediment to the treatment of disease (2)
- Prevents movement of penicillin to the underlying peptidoglycan
- Drug becomes ineffective against many gram-negative pathogens
Where is the periplasmic space found?
Between the cytoplasmic membrane and outer membrane of gram-negative bacteria
What does the periplasmic space contain?
Digestive enzymes and proteins involved in specific transport