Glycolisis

Step 1: Glucose → Glucose-6-Phosphate

• What happens? The glucose molecule enters the cell and gets hit with a phosphate from ATP.

• Why? This traps glucose inside the cell and makes it chemically unstable.

• Energy? 1 ATP is used here.

• Visual: You’ll see ATP dropping a P onto glucose.

Analogy: Like scanning a movie ticket before you enter — once you're in, you can't leave (glucose can’t leave now).

Step 2: Glucose-6-Phosphate → Fructose-6-Phosphate

• What happens? The glucose gets rearranged into a new sugar form (fructose).

• Why? Prepping it for another phosphate to make it symmetrical (for splitting).

• Energy? None used here.

• Visual: The shape of the molecule changes.

Analogy: Like twisting a Rubik’s cube to line up colors before the next move.

Step 3: Fructose-6-Phosphate → Fructose-1,6-Bisphosphate

• What happens? Another phosphate is added from a second ATP.

• Why? This makes the molecule even more unstable and ready to split.

• Energy? 1 more ATP is used.

• Visual: Now the sugar has 2 phosphates attached (one on each end).

Analogy: Like pulling both ends of a stick until it snaps.

Step 4: Fructose-1,6-Bisphosphate → DHAP + G3P

• What happens? The 6-carbon sugar splits in half into two 3-carbon sugars.

• Why? You can’t use glucose’s energy until it's in small chunks.

• Visual: You’ll see one big molecule become two.

Analogy: Like cutting a sub sandwich in half to share.

Step 5: DHAP → G3P

• What happens? DHAP is converted into another G3P.

• Why? So now you have two identical 3-carbon sugars to work with.

• Visual: You now have 2 G3Ps going through the rest of glycolysis.

Analogy: Like converting Canadian dollars to US dollars so everything matches.

Step 6: G3P → 1,3-Bisphosphoglycerate

• What happens? NAD+ takes electrons and becomes NADH; phosphate is added to G3P.

• Why? This stores energy in NADH and adds energy to the sugar.

• Energy? NAD+ becomes NADH for each G3P (2 total).

• Visual: You’ll see electrons transferring and new P's being added.

Analogy: Like charging up a power bank (NAD+ becomes NADH).

Step 7: 1,3-Bisphosphoglycerate → 3-Phosphoglycerate

• What happens? A phosphate is removed and added to ADP to make ATP.

• Why? First ATP payoff.

• Energy? 2 ATP made here (one from each G3P).

• Visual: A P gets moved from sugar to ADP → becomes ATP.

Analogy: Like cashing in your coupons for real money.

Step 8: 3-Phosphoglycerate → 2-Phosphoglycerate

• What happens? The phosphate group is shifted to a new position.

• Why? To prep the molecule for the final step.

• Visual: Rearrangement.

Analogy: Like moving the engine in a car to the back before a race.

Step 9: 2-Phosphoglycerate → Phosphoenolpyruvate (PEP)

• What happens? A water molecule is removed (dehydration).

• Why? Makes the molecule even more unstable.

• Visual: Water (H₂O) is released.

Analogy: Like squeezing water out of a sponge before lighting it on fire.

Step 9: 2-Phosphoglycerate → Phosphoenolpyruvate (PEP)

• What happens? A water molecule is removed (dehydration).

• Why? Makes the molecule even more unstable.

• Visual: Water (H₂O) is released.

Analogy: Like squeezing water out of a sponge before lighting it on fire

Second atp payoff

Step 10: PEP → Pyruvate

• What happens? The last phosphate is removed and added to ADP → more ATP made.

• Why? Final ATP payout.

• Energy? 2 ATP made here (1 per G3P).

• End Result? You get 2 pyruvate, ready for the next stage.

Analogy: Like launching the final piece of a firework show — boom, big payoff.

Glucose used

Used:1

Pyruvate used

2 Pyruvate

Atp used

2 Atp

ATP made

4 made

Net ATP

2 Net atp

NADH made

2 Nadh made

Water Released

2 water relased

Final Result of Glycolysis (What’s the point?)

You're breaking 1 glucose into 2 pyruvates to:

• Make ATP = energy your cells need to live

• Make NADH = energy storage for the next stage (like saving coins)

• Prepare pyruvate for the Krebs Cycle or fermentation

What is the overall purpose of glycolysis?

To break 1 glucose into 2 pyruvate molecules, making 2 ATP (net) and 2 NADH in the process. It happens in the cytoplasm and does not require oxygen.

Q: What is phosphorylation in glycolysis?

It's when a phosphate group is added to a molecule. ATP gives its phosphate to glucose to make it more reactive

What happens during the investment phase of glycolysis?

2 ATP are used to add phosphates to glucose, turning it into fructose-1,6-bisphosphate.

Q: What is the end product of the investment phase?

Fructose 1,6-bisphosphate

What happens during the sugar-splitting phase of glycolysis?

Fructose 1,6-bisphosphate splits into 2 molecules: DHAP and G3P. DHAP is converted into another G3P.

The 6-carbon sugar fructose-1,6-bisphosphate is split into two 3-carbon sugars:

• One is called G3P (glyceraldehyde-3-phosphate)

• The other is called DHAP (dihydroxyacetone phosphate)

But only G3P can continue in glycolysis — so…

👉 DHAP gets converted into another G3P

So now you have 2 identical G3P molecules, and each one goes through the second half of glycolysis.

Q: What happens during the oxidation phase?

: Both G3P molecules are oxidized using NAD+, which becomes NADH. Phosphates are added to the sugars.

What’s substrate-level phosphorylation?

When a phosphate is directly transferred from a molecule to ADP, making ATP.

What happens during the payoff phase?

Phosphates are removed from the sugars and added to ADP to make 4 ATP (2 net), and 2 NADH are made.

What happens if there is no oxygen after glycolysis?

The cell goes into fermentation, turning pyruvate into either lactic acid or ethanol + CO₂, just to recycle NAD⁺.

What’s the difference between NAD⁺ and NADH?

NAD⁺ is an empty battery. NADH is charged up with electrons (like a full battery) and carries energy to the mitochondria.

Lactic Acid Fermentation

:

🧾 Where it happens:

• In animal cells (like your muscles when you work out too hard)

• Some bacteria (used in yogurt & sour cream)

🧬 What happens:

• Pyruvate (from glycolysis) gets turned into lactic acid

• NADH gives its electrons to pyruvate → becomes NAD⁺ again

🔄 Why?
So glycolysis can restart by reusing NAD⁺
⚡ No extra ATP is made here — just recycling

🤕 Effect:
Lactic acid builds up in muscles = soreness

Alcoholic Fermentation:

🧾 Where it happens:

• In yeast and some plants

🧬 What happens:

• Pyruvate → becomes ethanol (alcohol) and CO₂

• NADH → gives electrons back → regenerates NAD⁺

🔄 Why?
Same reason: to keep glycolysis going when no O₂ is around

🍺 Effect:
This is how bread rises (CO₂ bubbles) and how alcohol is made

HOW TO IDENTIFY PHASE IN PICTURES:

• ATP is used = Investment (Steps 1 & 3)

• Sugar splits in 2 = Cleavage (Step 4)

• ATP/NADH made = Payoff (Steps 6–10)

What is ATP? Why is it important? How is it recycled?

ATP (Adenosine Triphosphate) = the main energy currency in your cells

• It powers muscles, thinking, breathing — everything.

🧠 Analogy: ATP = a charged battery.
When used, it becomes ADP (battery drained)
When recharged (by adding phosphate), it becomes ATP again

ATP is recycled by:

• Breaking it: ATP → ADP + Pi (releases energy)

• Rebuilding it: ADP + Pi → ATP (requires energy, like from food)

equation for cellular respiration.

✅ Balanced Equation:

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ~36-38 ATP

Glucose + Oxygen → Carbon Dioxide + Water + Energy

What are electron carriers? What role do they play? Name two.

Electron carriers are molecules that temporarily hold electrons taken from glucose.

• They carry energy to the Electron Transport Chain (ETC)

• Think of them like charged delivery trucks bringing energy

🧠 Analogy: NADH and FADH₂ are Uber Eats drivers, delivering electrons to the “power plant” (ETC) to make ATP

Two carriers:

• NAD⁺ → NADH

• FAD → FADH₂

What are Redox reactions?

Redox = Reduction + Oxidation

• Oxidation = Losing electrons

• Reduction = Gaining electrons
  🧠 Analogy: Think of electrons like money:

• If you give away money (electrons) → you're oxidized

• If you receive money (electrons) → you're reduced

Redox reactions are how energy is transferred in cellular respiration! Electrons carry energy — so transferring them powers ATP production.

Phase 1: Energy Investment Phase

🧠 Goal: Spend energy to prepare glucose for breaking

What happens:

• 2 ATP are used

• Glucose gets phosphorylated (phosphates added to it)

• Glucose is turned into Fructose 1,6-bisphosphate

• That molecule is then split into two 3-carbon sugars:

  • DHAP and G3P

  • DHAP is converted into another G3P

✔ At the end of Phase 1:

• You now have 2 G3P molecules

• No energy is made yet — you actually lost 2 ATP

Phase 2: Energy Payoff Phase

🧠 Goal: Each G3P makes NADH + ATP as it becomes pyruvate

What happens for EACH G3P:

• NAD⁺ takes electrons → NADH is made

• 2 ATP are made by substrate-level phosphorylation

• Ends as Pyruvate (3C)

Since you had 2 G3P → this happens twice

✔ At the end of Phase 2 (total from both G3P):

• 2 Pyruvate

• 2 NADH

• 4 ATP (but subtract 2 used earlier) → net 2 AT