A2 Unity and diversity: Cells Flashcards
What key structural difference between prokaryotic and eukaryotic cells supports the theory of endosymbiosis?
Mitochondria and chloroplasts in eukaryotes have double membranes, 70S ribosomes, and circular DNA, like prokaryotes—suggesting they were once free-living cells engulfed by ancestral eukaryotes.
What’s the main function of the smooth endoplasmic reticulum (SER), and how does it differ from the rough ER?
The smooth ER synthesizes lipids and steroids, and detoxifies substances. It lacks ribosomes, unlike the rough ER, which is involved in protein synthesis and transport.
What is the role of the Golgi apparatus in protein processing?
It modifies, sorts, and packages proteins from the ER into vesicles for secretion or internal use.
What are lysosomes and how are they formed?
Lysosomes are membrane-bound vesicles containing hydrolytic enzymes. They’re formed by the Golgi apparatus and are responsible for breaking down cellular waste and debris.
What is the significance of compartmentalization in eukaryotic cells?
It allows for specialized environments within organelles, increasing efficiency and enabling simultaneous incompatible reactions.
How can you calculate actual size of a cell/organelle from a micrograph?
actual size = image size ÷ magnification
What makes stem cells special compared to differentiated cells?
They’re undifferentiated, can self-renew, and differentiate into specialized cells.
What’s the key argument for using stem cells from embryos over adult tissues?
Embryonic stem cells are pluripotent—they can become any cell type. Adult stem cells are usually multipotent and more limited in their potential.
Why are viruses not considered living organisms?
They lack cellular structure, can’t reproduce on their own, and don’t carry out metabolism.
How do electron microscopes differ from light microscopes?
Electron microscopes use electrons instead of light, have a higher resolution, and allow you to see ultrastructure (like ribosomes and membranes).
But they’re expensive, and the samples have to be dead and dehydrated—RIP.
How do fatty acids spontaneously form vesicles?
In water, fatty acids naturally coalesce into spherical bilayers, forming vesicles due to their hydrophilic heads and hydrophobic tails.
What are key structural features of a prokaryotic cell?
No membrane-bound organelles
Circular DNA in the nucleoid
70S ribosomes
Cell wall made of peptidoglycan
Often has plasmids and a capsule
What are key features of a eukaryotic cell?
Membrane-bound nucleus
80S ribosomes
Compartmentalized organelles (e.g. ER, Golgi, mitochondria)
DNA in linear chromosomes
What structural differences exist between animal, plant, and fungal eukaryotic cells?
Plants: cell wall (cellulose), chloroplasts, large central vacuole
Animals: no cell wall, have lysosomes and centrioles
Fungi: cell wall (chitin), no chloroplasts
What structural features are shared by all viruses?
Protein coat (capsid)
Genetic material (DNA or RNA)
Some have lipid envelopes
No organelles, no metabolism
What happens in the lytic cycle of a virus?
The virus injects its genetic material → hijacks the host cell → assembles new viruses → bursts the cell (lysis) to release them.
What happens in the lysogenic cycle of a virus?
The virus integrates its DNA into the host genome (as a prophage/provirus) → replicates silently during cell division → may activate later and switch to lytic.
