AP Bio - Unit 2 Review

Compare a prokaryote to a eukaryote.

Prokaryotes = no nucleus or membrane-bound organelles.
Eukaryotes = have a nucleus and organelles

Why do scientists think that eukaryotes evolved from prokaryotes (endosymbiosis theory)? Provide at least two pieces of evidence

Eukaryotes evolved when one prokaryote engulfed another.
Evidence:

Mitochondria and chloroplasts have their own DNA.
They reproduce independently by binary fission.

Why is it important that cells exchange materials with their environment? Give two examples

To get nutrients and remove waste.
Examples: oxygen in, carbon dioxide out; glucose in, waste out

Why are cells small?

Smaller cells have a higher surface area-to-volume ratio, allowing faster material exchange

Bigger cells have higher or lower SA/V ratios. Explain.

Lower SA/V ratio — less surface area for exchange, making transport inefficient

Why do we have embedded proteins?

They help with transport, signaling, and cell recognition in the membrane

Why is a cell membrane considered selectively permeable? What items can move across the membrane with ease?

It only allows certain substances through.
Small, nonpolar molecules (like O₂, CO₂) move easily

What is a cell wall made of in bacteria?

peptidoglycan

What is a cell wall made of in plants?

cellulose

What is a cell wall made of in fungi?

chitin

What is passive transport? How do the molecules move across the membrane with passive transport?

Moves molecules from high → low concentration without energy (diffusion, osmosis).

What is active transport? How do the molecules move across the membrane with active transport?

Moves molecules from low → high concentration using energy (ATP).

Compare endocytosis to exocytosis. 

Endocytosis = cell takes in materials.
Exocytosis = cell releases materials

How does the sodium potassium pump work?

Uses ATP to move 3 Na⁺ out and 2 K⁺ in, maintaining cell charge and ion balance

What is an aquaporin’s purpose?

Protein channels that allow water to move quickly across membranes

Compare hypertonic, hypotonic, and isotonic solutions.

Hypertonic: water moves out → cell shrinks.
Hypotonic: water moves in → cell swells.
Isotonic: water moves equally → no change

What is osmosis? How does it work? 

Diffusion of water through a selectively permeable membrane from high to low water concentration

What is water potential? How is it calculated?

Measures water’s ability to move; ψ = pressure potential + solute potential (ψ = Ψp + Ψs)

How does cell compartmentalization help a cell? Explain. 

It separates reactions into organelles, increasing efficiency and allowing different environments for different functions