Glycolysis - Copyright © 2003 Nelson Chapter 2 Cellular ... - Free Printable

Let's solve this Glycolytic Pathway worksheet step by step, filling in the blanks and identifying molecules A to F based on the glycolysis pathway.

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🔬 Overview of Glycolysis

Glycolysis is a metabolic pathway that breaks down one molecule of glucose (6 carbons) into two molecules of pyruvate (3 carbons each), producing ATP and NADH. It occurs in the cytoplasm and consists of 10 steps, grouped into four phases:

1. Glucose Activation (Steps 1–4): Glucose is phosphorylated and converted to fructose-1,6-bisphosphate.
2. Sugar Splitting (Step 5): The 6-carbon sugar is split into two 3-carbon molecules.
3. Oxidation (Steps 6–7): Each 3-carbon molecule is oxidized, producing NADH.
4. ATP Formation (Steps 8–10): Substrate-level phosphorylation produces ATP.

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## ✔ Molecule Identification: A to F

We’ll use the diagram to identify each molecule:

- A: Glucose → First molecule shown
- B: Glucose-6-phosphate → Phosphorylated glucose
- C: Fructose-6-phosphate → Isomerization of B
- D: 1,3-Bisphosphoglycerate → After oxidation and phosphorylation
- E: 3-Phosphoglycerate → After phosphate transfer
- F: Pyruvate → Final product

> ⚠️ Note: The diagram shows simplified structures with carbon (black), oxygen (white), and phosphate (gray). The key transformations are:
>
> - Glucose → Glucose-6-P → Fructose-6-P → Fructose-1,6-BP → Dihydroxyacetone-P + Glyceraldehyde-3-P → 1,3-BPG → 3-PG → 2-PG → PEP → Pyruvate

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🧩 Step-by-Step Answers

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#### 1. Glucose Activation

> During the first four steps of glycolysis,
> two phosphate groups are transferred to
> glucose via kinases, where glucose
> is converted to fructose-1,6-bisphosphate.
> The end product is fructose-1,6-bisphosphate.

✔ Explanation:
- Glucose → Glucose-6-P (uses 1 ATP)
- Glucose-6-P → Fructose-6-P (isomerase)
- Fructose-6-P → Fructose-1,6-BP (uses 1 ATP)

So, two ATPs are consumed to phosphorylate glucose → fructose-1,6-bisphosphate.

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#### 2. Sugar Splitting

> Fructose-1,6-bisphosphate gets split into two fragments,
> dihydroxyacetone phosphate (DHAP) and
> glyceraldehyde-3-phosphate (G3P).
> DHAP then gets converted into G3P.

✔ Explanation:
- The 6-carbon molecule splits into two 3-carbon molecules: G3P and DHAP.
- DHAP is rapidly converted to G3P by triose phosphate isomerase.
- So, we now have two molecules of G3P.

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#### 3. Oxidation

> Both molecules of glyceraldehyde-3-phosphate become oxidized using
> NAD⁺, which becomes NADH.
> This process releases inorganic phosphate (Pi), which is used to attach
> phosphate groups to the sugars, making them
> 1,3-bisphosphoglycerate.

✔ Explanation:
- G3P is oxidized to 1,3-bisphosphoglycerate.
- NAD⁺ accepts electrons → becomes NADH.
- Inorganic phosphate (Pi) is added to the sugar during this reaction.
- The energy from oxidation is used to form a high-energy phosphate bond.

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#### 4. Formation of ATP

> During the last four steps of glycolysis, the
> phosphate groups of the molecules are transferred to ADP,
> creating ATP.
> This is done via the process of substrate-level phosphorylation.

✔ Explanation:
- Two ATPs are produced per G3P (so 4 total from two G3Ps).
- ATP is made directly from ADP and phosphate (from intermediates like 1,3-BPG and PEP).
- This is substrate-level phosphorylation — not oxidative phosphorylation.

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✔ Final Answer Summary

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#### Molecules A to F

| Letter | Molecule Name |
|--------|----------------|
| A | Glucose |
| B | Glucose-6-phosphate |
| C | Fructose-6-phosphate |
| D | 1,3-Bisphosphoglycerate |
| E | 3-Phosphoglycerate |
| F | Pyruvate |

> ⚠️ Note: The diagram shows two molecules after splitting, so D and E are shown as “2” molecules. D is 1,3-BPG; E is 3-PG; F is pyruvate.

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✔ Completed Worksheet Blanks

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1. Glucose Activation
During the first four steps of glycolysis,
two phosphate groups are transferred to
glucose via kinases, where glucose
is converted to fructose-1,6-bisphosphate.
The end product is fructose-1,6-bisphosphate.

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2. Sugar Splitting
Fructose-1,6-bisphosphate gets split into two fragments,
dihydroxyacetone phosphate (DHAP) and
glyceraldehyde-3-phosphate (G3P).
DHAP then gets converted into G3P.

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3. Oxidation
Both molecules of glyceraldehyde-3-phosphate become oxidized using
NAD⁺, which becomes NADH.
This process releases inorganic phosphate (Pi), which is used to attach
phosphate groups to the sugars, making them
1,3-bisphosphoglycerate.

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4. Formation of ATP
During the last four steps of glycolysis, the
phosphate groups of the molecules are transferred to ADP,
creating ATP.
This is done via the process of substrate-level phosphorylation.

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📌 Final Notes

- Net ATP gain: 4 ATP produced – 2 ATP used = 2 ATP net
- Net NADH: 2 NADH produced
- Final product: 2 pyruvate molecules

This completes the worksheet!

Let me know if you'd like a labeled version of the diagram or a visual explanation!