CELL ORGANELLES (PG 61-65)
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35 Terms
What is the endomembrane system?
The nuclear envelope, ER, Golgi, lysosomes, vacuoles, transport vesicles, and plasma membrane working together.
(🧬 Nuclear envelope = the nucleus’s outer covering
Think of the nucleus as a little room inside the cell.
🏠 Nucleus = the room
🧱 Nuclear envelope = the walls around the room
🧬 DNA = the important stuff inside the room)
What does the endomembrane system do?
It modifies, packages, and transports proteins, lipids, and carbohydrates where they need to go.
What is the endosymbiosis hypothesis
It says that mitochondria and chloroplasts used to be free-living prokaryotes that were swallowed by larger cells and eventually became organelles.
What evidence supports endosymbiosis?
Mitochondria and chloroplasts:
Have their own DNA
Have their own ribosomes
Reproduce by binary fission, like bacteria
What is kleptoplasty?
When an organism takes in photosynthetic cells/organelles and keeps their chloroplasts working instead of digesting them.
What is compartmentalization?
Dividing the cell into separate areas so different jobs can happen separately
Why is compartmentalization helpful?
It makes the cell more efficient because different reactions can happen in different places without interfering with each other.
Why do some organelles have folded membranes?
The folds give the organelle more surface area for reactions to happen.
Example: mitochondrial cristae.
Why is surface area important for a cell?
The cell uses its surface to take in nutrients, remove waste, and exchange materials with its environment.
What happens to surface area-to-volume ratio as a cell gets bigger?
It decreases
Why are smaller cells more efficient?
They have a larger surface area compared with their volume, so they can exchange materials more efficiently
How can cells increase surface area?
They can make folds in their membranes.
Examples:
Mitochondrial cristae
Intestinal villi
What does the plasma membrane do?
It controls what enters and leaves the cell.
What is selective permeability?
The membrane lets some things through but blocks other things.
What are phospholipids made of?
A hydrophilic head and two hydrophobic tails.
Easy:
💧 Head = likes water
🚫 Tails = avoid water
Why do phospholipids form a bilayer?
The heads face the water, while the tails hide away from water.
What is the fluid mosaic model?
The cell membrane is like a flexible, moving layer made of different parts floating around in it
What are some things found in the plasma membrane?
Phospholipids
Proteins
Glycoproteins
Glycolipid
What do membrane proteins do?
They can:
Transport materials
Help with cell signaling
Anchor the cell
Help chemical reactions happen
What do glycoproteins and glycolipids do?
They help cells recognize each other.
What do steroids do in the membrane?
They help adjust membrane fluidity.
What can easily cross the phospholipid bilayer?
Small hydrophobic/nonpolar molecules, such as:
O₂
CO₂
N₂
What cannot easily cross by itself?
Large polar molecules and ions.
They need membrane proteins to help them cross.
What are aquaporins?
Special membrane proteins that allow water (H₂O) to move through the membrane.
What is a cell wall?
A stiff outer layer around plant, fungal, and prokaryotic cells that gives the cell support and protection.
What is passive transport?
Movement from HIGH concentration → LOW concentration.
⭐ Does NOT require energy.
Think:
⬆ HIGH → ⬇ LOW = PASSIVE
What is diffusion
The movement of molecules from high → low concentration without energy.
What is osmosis?
The diffusion of water across a membrane.
What is facilitated diffusion?
Movement from high → low concentration, but the molecule needs a membrane protein to help it cross.
Still NO energy.
Why is facilitated diffusion called “saturable”?
Because there are only so many membrane proteins available to help molecules cross.
What is active transport?
Movement from LOW → HIGH concentration.
⭐ Requires energy.
Think:
⬇ LOW → ⬆ HIGH = ACTIVE ⚡
What does the sodium-potassium pump do?
It pumps:
3 Na⁺ OUT
2 K⁺ IN
And it uses energy.
What are endocytosis and exocytosis?
Both require energy and are forms of active transport.
Endocytosis: cell takes stuff IN 📥
Exocytosis: cell sends stuff OUT 📤
What happens during endocytosis?
The cell membrane wraps around material and makes a vesicle to bring it inside.
What happens during exocytosis?
A vesicle fuses with the cell membrane and releases its contents outside.
