Flashcards Cell Structures Chp 3 Part 1
Who first used the term ‘cells’ in 1665?
Robert Hooke
What was Robert Hooke observing when he coined the term ‘cells’?
The structure of cork, which he likened to a honeycomb.
List three main points of modern Cell Theory.
Cells are the fundamental unit of life; All organisms are made of cells; Cells arise from other cells through cell division.
What are the four processes shared by all living things?
Growth, reproduction, responsiveness, metabolism.
What is the fundamental difference between prokaryotic and eukaryotic cells?
Prokaryotic cells lack a nucleus and membrane-bound organelles, while eukaryotic cells have both.
What types of organisms are prokaryotic?
Bacteria and archaea.
What types of organisms are eukaryotic?
Algae, protozoa, fungi, animals, and plants.
What is the function of the cell envelope?
It surrounds the cytoplasm and governs interactions with the external environment.
Why is the cell envelope important?
It provides structure, protects against osmotic forces, aids in attachment, and resists antimicrobial drugs.
What are the major components of the prokaryotic cell envelope?
Cytoplasmic membrane, cell wall, outer membrane (in Gram-negative bacteria), and S-layers.
What is the composition of the cytoplasmic membrane?
A phospholipid bilayer with embedded proteins.
What is the Fluid Mosaic Model?
Describes the dynamic structure of the cell membrane, where proteins and lipids move freely.
What does ‘selectively permeable’ mean in terms of the cytoplasmic membrane?
It allows some substances to pass while blocking others.
What is simple diffusion?
Movement of molecules down a concentration gradient without energy use.
What is facilitated diffusion?
Passive transport of molecules across a membrane via protein channels.
What is active transport?
Movement of molecules against a concentration gradient using energy.
What is the proton motive force?
Potential energy from an H+ gradient used to drive transport and ATP synthesis.
What is the function of the bacterial cell wall?
Provides structure, prevents lysis, and maintains cell shape.
What is peptidoglycan?
A polymer of sugars (NAG and NAM) and peptides that forms bacterial cell walls.
What enzyme breaks β 1,4-glycosidic bonds in peptidoglycan?
Lysozyme.
How does the bacterial cell wall protect against osmotic pressure?
It prevents excessive water influx, which could cause cell lysis.
What are the key features of Gram-positive bacteria?
Thick peptidoglycan layer, teichoic acids, no outer membrane.
What are the key features of Gram-negative bacteria?
Thin peptidoglycan layer, outer membrane with LPS, periplasmic space.
What is lipopolysaccharide (LPS) and where is it found?
A component of the outer membrane in Gram-negative bacteria; acts as an endotoxin.
Why are Gram-negative bacteria more resistant to antibiotics?
Their outer membrane blocks many antibiotics.
What is the purpose of Gram staining?
To differentiate bacteria based on cell wall composition.
What color do Gram-positive bacteria appear after staining?
Purple.
What color do Gram-negative bacteria appear after staining?
Red (or pink).
Why does Gram-negative bacteria lose the crystal violet stain?
The alcohol decolorizer removes the outer membrane and releases the stain.
What is acid-fast staining used for?
Identifying bacteria with waxy mycolic acid cell walls (e.g., Mycobacterium).
What color are acid-fast bacteria after staining?
Red.
What color are non-acid-fast bacteria after staining?
Blue.
Why can’t some bacteria be Gram-stained?
They may lack peptidoglycan, have waxy cell walls, or be obligate intracellular bacteria.
What are the three basic bacterial shapes?
Coccus (spherical), bacillus (rod-shaped), spiral (curved or helical).
What are common bacterial arrangements?
Single cells, pairs (diplococci), chains (streptococci), clusters (staphylococci).
Which bacteria lack a cell wall?
Mycoplasma species.
What are obligate intracellular bacteria?
Bacteria that must live inside host cells to survive (e.g., Chlamydia).
What is the function of S-layers?
Provides strength, protection, adhesion, and resistance to host defenses.
Why are some bacteria resistant to traditional staining methods?
They may have waxy, complex, or minimal cell walls that prevent stain penetration.
