Veda Bites are swipeable micro-lessons — each one teaches exactly one
idea. Here's a taste from this kit; the app has the full deck.
💡 Key Idea
The Cell Is the Basic Level of Life
What is the smallest thing that counts as alive?
Nothing alive is built from anything else. Go downward through an organism and the cell is where life stops being divisible.
↳ Go below the cell and you no longer have something alive.
⚙️ Process
Cell, Tissue, Organ, System
How do cells build a body?
Take breathing: the nasal pores, the nasal cavity, the trachea and the lungs are four organs doing one job between them.
↳ Four levels, in that order - and the cell stays the unit of structure and function throughout.
⭐ Important Fact
The Eye Runs Out at 0.1 mm
Why can you not just look at a cell?
Viewed from about 25 cm (the near point of the eye), two points must be at least 0.1 mm apart to be seen as two.
↳ Cell biology could not begin until an instrument existed.
📖 Definition
The Plasma Membrane
What separates a cell from everything else?
It is selectively permeable — some substances are let across, others turned back.
↳ Not a sealed bag, and not an open door. A gate with a policy.
✏️ Example
The Potato Experiment
Two potato pieces, one hour.
Water crossed the membrane both ways. The salt and sugar could not.
↳ Only the water was ever moving.
⚖️ Comparison
Diffusion Against Osmosis
The two words students mix up most.
↳ All osmosis is diffusion. Most diffusion is not osmosis.