- D2 ✏︎ Cells -
D2.1 - Cell & Nuclear Division (SL/HL)
LECTURE VIDEO
DESCRIPTION
Move over, family trees—it’s time to meet the real reproduction methods. Mitosis isn’t just “cells splitting”; it’s the body’s flawless photocopier, making exact duplicates of you since day one. And meiosis? That’s its chaotic sibling who shuffles the genetic deck like a casino dealer and creates the ultimate lottery tickets: sperm and eggs.
This video crashes the cellular replication party, from binary fission to budding, and reveals why some organisms don’t even need a plus-one:
- Mitosis: The Faithful Clone Machine: One cell in, two cells out. Identical DNA. No drama. Used for growth, repair, and replacing the skin cells you’re shedding all over your phone screen right now.
- Meiosis: The Genetic Shuffle: Four cells out. Half the DNA. Each one unique. Features a brief but steamy chromosomal hookup (crossing over) that swaps genetic material just to keep things interesting. Sex exists because of this. You’re welcome.
- Binary Fission: Bacteria Don’t Do Romance: No nucleus. No spindle. Just copy, grow, split. One becomes two becomes four becomes a yogurt. Simple. Efficient.
- Budding: When You Just Want a Mini-You: The yeast and hydra special. Grow a lump, copy the DNA, pinch it off. Now there’s a tiny clone floating nearby. Not a twin. Not a child. Both. Weird flex but okay.
Understand how life copies itself—whether it’s making perfect repairs, shuffling the genetic lottery, or just squeezing out a miniature version of itself and calling it a Tuesday.
TIMESTAMPS
STUDY RESOURCES
00:00 – Intro To Mitosis, Meiosis, Binary Fission, Budding
05:20 – What is NOT mitosis?
07:40 – The Cell Cycle (+ Some Interphase Details)
12:10 – Nucleus Brief Review
14:49 – Interphase
16:38 – Prophase [Mitosis]
23:19 – Metaphase [Mitosis]
24:08 – Anaphase [Mitosis]
28:36 – Telophase [Mitosis]
29:17 – Cytokinesis &.Table/Word Summary Of Mitosis
33:04 – Guess the Stage Of Mitosis?
33:57 – What & Why Meiosis?
36:56 – Meiosis I
43:52 – Meiosis II
46:47 – Overall Meiosis & Table/Word Summary
48:07 – Crossing Over (Prophase I)
51:34 – Independent Assortment (Metaphase I)
54:27 – Non-Disjunction (Problem In Meiosis)
55:54 – Binary Fission & Budding
57:06 – Oogenesis Unequal Cytokinesis
58:05 – Questions & Answers
NOTES – All you need to know in one place!
QUESTIONS – Test your Big Brain!
D2.1 - Cell & Nuclear Division (HL)
LECTURE VIDEO
DESCRIPTION
Your cells don’t just divide whenever they want. There’s a system. Security guards. ID checks. VIP lists. When that system breaks, cells divide like there’s no tomorrow—and eventually, there isn’t.
This video raids the cellular nightclub:
- The Cell Cycle: Not Just Mitosis, The Whole Vibe
G1: “Do I even need to exist?”
S: “Time to copy my entire genetic hard drive.”
G2: “Did I screw that up? Double-checking.”
M: The main event (all those weird “phases”. Then cytokinesis (cell splitting). Then back to G1, smaller, tired, ready to do it all again. - Cyclins & CDK: The Bouncer and His Pager
CDK is the doorman. Cyclin is the signal that tells him when to work. Together, they guard the checkpoints. No cyclin? Doors locked. No CDK? No bouncer. Chaos. - Cancer: When the Security Team Sleeps on the Job
Cancer is what happens when a cell ignores the rules and divides anyway. Forever.
Proto-oncogene mutation? Gas pedal stuck down. Tumor suppressor mutation? Brakes? What brakes?
The cell doesn’t die when it should. It doesn’t stop when it should. It just… goes. - Mitotic Index: Measuring the Mayhem
Cells in mitosis ÷ total cells × 100.
High in embryos. High in healing wounds.
Terrifyingly high in tumours.
Low in your liver, which is just quietly doing its job, thanks for asking.
Understand the bouncers, the corrupted security footage, and the genetic typos that turn a normal cell into an immortal menace .
TIMESTAMPS
STUDY RESOURCES
00:00 – Outline Of This Video
01:00 – Recap Of Mitosis V.S Meiosis
01:34 – Purposes Of Mitosis
07:09 – The Cell Cycle
18:42 – Cyclins & cyclin dependent kinases (CDK’s)
34:37 – Cancer Explained
44:50 – Mitotic Index
48:13 – Effect Of Mutations
55:35 – Questions & Answers
NOTES – All you need to know in one place!
QUESTIONS – Test your Big Brain!
D2.2 - Gene Expression (HL)
LECTURE VIDEO
DESCRIPTION
Your genome is the complete instruction manual for every protein in your body. Your transcriptome is the specific pages your cell has photocopied and taped to the wall. Your proteome is the actual furniture you’ve built. A liver cell and a neuron have the exact same manual—they’re just reading completely different chapters.
This video exposes which genes get the mic and which get sent to voicemail:
In Eukaryotes: The Control Freaks
- mRNA synthesis: Transcription factors = bouncers deciding which genes get the mic and which stay silent . Enhancers yell “LET THEM IN.” Silencers shake their heads.
- mRNA breakdown: Some mRNA lasts hours. Some gets shredded instantly. Job security varies.
- Epigenetic modifications: Permanent-ish tags saying “USE THIS” or “IGNORE FOREVER”. Methylation? “DO NOT READ” sticker on the DNA. Acetylation? Loosening the histone spool so the gene gets attention. Same gene. Different wrapping. Identical twins, different outcomes.
In Prokaryotes: The Minimalists. No nucleus. No drama. Just the operon.
- Lac operon: Lactose? Flip switch, digest. No lactose? Switch off. Save energy.
- Trp operon: Low tryptophan? Build it. High tryptophan? Shut up. Bacteria don’t overthink. They’re IKEA.
Understand how your cells decide which genes get a megaphone, which get a muzzle, and which are still waiting for a callback after 30 years.
TIMESTAMPS
STUDY RESOURCES
00:00:00 – Overview Of This Video
00:00:32 – Epigenesis
00:04:36 – What Is Gene Expression?
00:09:02 – Genome, Transcriptome, Proteome
00:10:08 – Phenotype & Genotype
00:12:30 – Gene expression can be regulated
00:12:50 – Regulation of mRNA synthesis (Eukaryotes)
00:24:49 – Regulation of mRNA breakdown (Eukaryotes)
00:31:01 – Epigenetics, DNA & Histone Methylation (Eukaryotes)
00:39:50 – Epigenetic Inheritance
00:42:55 – TWINS
00:46:55 – Imprinted Genes
00:53:53 – [LAC OPERON] Regulation of mRNA synthesis (Prokaryotes)
00:59:51 – [TRP OPERON] Regulation of mRNA synthesis (Prokaryotes)
01:03:44 – Questions & Answers
NOTES – All you need to know in one place!
QUESTIONS – Test your Big Brain!
D2.3 - Water Potential (SL/HL)
LECTURE VIDEO
DESCRIPTION
Move over, mitosis—it’s time to meet the real cellular crowd-pleaser. Osmosis isn’t just “water moving”; it’s the ultimate groupie, following solutes around and crashing concentration gradients uninvited. And your cell membrane? That’s the reluctant bouncer trying to keep the whole thing from becoming a flooded disaster.
This video dives into the watery drama of cellular life, from raisin-mode to explosion-level turgidity, and reveals why hospitals are so weirdly obsessed with saline:
- Isotonic: The Goldilocks Zone – Same concentration inside and out. Water moves equally in both directions. Animal cell is thriving. Plant cell is… fine. A little floppy, but fine. No drama. Boring. Perfect.
- Hypotonic: The Water Park Incident – More water outside than inside. Water floods in. Animal cell swells. Keeps swelling. Then bursts. Lysis. A watery grave. Plant cell? It has a cell wall. It gets plump. Turgid. Crisp. Instagram-ready lettuce energy.
- Hypertonic: The Desert Vacation – More solute outside than inside. Water flees. Animal cell shrivels into a sad, spiky raisin (crenation). Plant cell? The membrane peels away from the wall. Plasmolysis. The plant wilts dramatically. It’s not dead. It’s just judging you.
- Isotonic Fluids: Why IV Bags Aren’t Tap Water – Same saltiness as your blood. Used in hospitals, contact lens solution, and keeping premature babies alive. Tastes like regret if you drink it. But it won’t pop your cells, so that’s a win.
- Paramecium: The Original Sump Pump – Lives in pond water—extremely hypotonic. Water constantly floods in. Its solution? A contractile vacuole that actively yeets water out before the cell goes kaboom. Single-celled organism. Genius engineering. Humans didn’t invent bilge pumps. This microscopic speck did.
- Your Kidney: The Fancy Version –Too much water? Pee it out. Too little? Hold onto it like it’s the last bottle at a festival. You are a walking, talking osmoregulator with excellent plumbing and absolutely no gratitude for it.
Understand why your cells are concentration-obsessed control freaks, why IVs aren’t just fancy hydration packs, and how a pond-dwelling protozoan figured out fluid management before your city’s water treatment plant.
TIMESTAMPS
STUDY RESOURCES
00:00 – Water Structure Details
07:37 – Water As A Solvent
15:56 – Osmosis
25:09 – Diffusion V.S Osmosis
29:45 – Isotonic, Hypotonic, Hypertonic
37:16 – Try It Yourself (Q/A)
40:17 – Uses Of Isotonic Solutions
45:12 – Osmosis In Plant Cell
50:31 – Adaptations (prevent swelling & shrinking)
55:01 – Questions & Answers
NOTES – All you need to know in one place!
QUESTIONS – Test your Big Brain!
D2.3 - Water Potential (HL)
LECTURE VIDEO
DESCRIPTION
Move over, osmosis—it’s time to meet the actual physics behind the thirst. Water potential isn’t just “how much water wants to move”; it’s the universal ranking system of wetness, and water always flows from “eh, I’m fine here” to “PLEASE I NEED TO BE HERE.” Pure water is the celebrity. Everything else is just trying to get an autograph.
This video measures the pressure, solute drama, and gravitational beef that determines where your H₂O ends up:
- What Is Water Potential (Ψ)?: Basically, water’s mood. How free it feels. Pure water at atmospheric pressure has a water potential of zero. Sounds like a perfect score, right? Wrong. Zero is the maximum. Everything else is NEGATIVE. Water potential is the only grading system where 0 is an A+ and -2000 is a cry for help.
- Solute Potential (Ψs): The Dissolved Drama – The more solutes you add, the more negative the water potential gets. Water sees dissolved sugar and salt and goes “oh thank god, somewhere I’m needed.” It rushes in. Plant cells love this. Your gummy bear? Put it in distilled water and watch it become a sad, bloated mattress.
- Pressure Potential (Ψp): The Pushback – Cell walls push back. Turgor pressure is just water potential’s way of saying “okay, that’s enough, we’re full.” In animal cells? No cell wall. No pushback. Just pop.
- Gravity Potential (Ψg): Only Matters If You’re a Tree – Water hates climbing. It takes serious negative water potential in the leaves to drag that column of H₂O up 100 meters of xylem. Trees aren’t majestic. They’re just really good at creating suction.
- Putting It All Together: Total water potential = solute + pressure +
gravity+matrix(but IB doesn’t need the last two, phew). Water moves from HIGHER (less negative) to LOWER (more negative). Always. It’s not about how much water there is. It’s about how desperate it is to be somewhere else.
Understand why zero is actually winning, why your cells are constantly playing hydration tug-of-war, and how a 100-meter tree is just one long, desperate straw with commitment issues.
TIMESTAMPS
STUDY RESOURCES
00:00 – Intro To Water potential
04:13 – Solute (Osmotic) Potential
07:51 – Pressure Potential
15:23 – Water potential from root to leaf
20:39 – Unwilted Plant (In hypotonic environment)
24:23 – Wilted Plant (In hypertonic environment)
26:47 – Questions & Answers
NOTES – All you need to know in one place!
QUESTIONS – Test your Big Brain!