Solved Carbohydrates Worksheet and Key 1) Define: aldoses, | Chegg.com - Free Printable

Let’s go step by step to solve each part of the worksheet.

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Part 1: Definitions and Comparisons

We’ll define each term simply, then compare them as asked.

Define:

- Aldose: A sugar with an aldehyde group (–CHO) at one end. Example: glucose.
- Ketose: A sugar with a ketone group (C=O) in the middle. Example: fructose.
- Hexose: A sugar with 6 carbon atoms. Example: glucose, fructose.
- Aldopentose: An aldose with 5 carbons. Example: ribose.
- Ketotetrose: A ketose with 4 carbons. Example: erythrulose.
- Alcohol sugar: A sugar where the carbonyl group is reduced to an alcohol. Also called “sugar alcohol.” Example: sorbitol.
- Deoxy sugar: A sugar missing one oxygen atom compared to normal sugar. Example: deoxyribose (in DNA).
- Amino sugar: A sugar with an amino group (–NH₂) instead of a hydroxyl group. Example: glucosamine.
- Carboxylic acid sugar: A sugar where the end carbon is oxidized to a carboxylic acid. Example: gluconic acid.
- Anomeric carbon: The carbon that becomes chiral when a sugar forms a ring — it was the carbonyl carbon before cyclization.
- Glycosidic bond: The bond linking two sugar molecules together (or a sugar to another molecule).
- Hemiacetal: Formed when an alcohol reacts with an aldehyde. In sugars, this happens when the OH on C5 attacks the carbonyl carbon (C1) to form a ring.
- Acetal: Formed when a hemiacetal reacts with another alcohol. Glycosidic bonds are acetals.
- Cyclic hemiacetal: The ring form of a sugar made from intramolecular reaction between OH and carbonyl group.

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Compare and contrast:

#### Haworth Projection vs. Fischer Projection

- Fischer: Flat, vertical chain. Top = most oxidized end (aldehyde/ketone). Horizontal lines = coming out toward you. Good for open-chain form.
- Haworth: Ring shape (usually hexagon or pentagon). Shows how the sugar looks in its cyclic form. Up/down positions show orientation of groups.

→ *Simple difference*: Fischer = straight line; Haworth = ring.

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#### Monosaccharide, Oligosaccharide, Polysaccharide

- Monosaccharide: One sugar unit. Can’t be broken down further. Example: glucose.
- Oligosaccharide: 2–10 sugar units linked together. Example: sucrose (glucose + fructose).
- Polysaccharide: Many sugar units (hundreds or thousands). Example: starch, cellulose.

→ *Difference*: Size — mono = 1, oligo = few, poly = many.

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#### D-sugar vs. L-sugar

- Based on the position of the –OH group on the last chiral carbon (farthest from carbonyl).
- If –OH is on the right in Fischer projection → D-sugar.
- If –OH is on the left → L-sugar.
- Most natural sugars are D-form.

→ *Think*: Right = D, Left = L (like driving side in some countries!).

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#### Starch vs. Glycogen

Both are polymers of glucose used for energy storage.

- Starch: Found in plants. Has amylose (linear) and amylopectin (branched).
- Glycogen: Found in animals (liver/muscles). More branched than starch.

→ *Key difference*: Branching — glycogen has more branches than starch.

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#### Amylose vs. Amylopectin

Both parts of starch.

- Amylose: Long, unbranched chains of glucose linked by α(1→4) bonds. Forms helix.
- Amylopectin: Branched chain. Main chain α(1→4), branches every ~24–30 units via α(1→6) bonds.

→ *Difference*: Amylose = no branches; Amylopectin = lots of branches.

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#### Cellulose vs. Amylose

Both are long chains of glucose.

- Cellulose: β(1→4) linkages. Straight chains. Strong fibers. Not digestible by humans.
- Amylose: α(1→4) linkages. Coiled/helical. Digestible by humans.

→ *Big difference*: Bond type — beta vs alpha. That changes everything!

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Part 2: Identify D- or L-monosaccharides

Look at the bottom chiral carbon (the one just above CH₂OH). In Fischer projection:

- If OH is on the right → D
- If OH is on the left → L

Let’s check each:

1. First structure (leftmost):
- Bottom chiral carbon: OH is on the right → D

2. Second structure:
- Bottom chiral carbon: OH is on the left → L

3. Third structure:
- Bottom chiral carbon: OH is on the right → D

4. Fourth structure:
- Bottom chiral carbon: OH is on the left → L

✔ So answers: D, L, D, L

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Part 3: Identify α or β anomer

In Haworth projection:

- Look at the anomeric carbon (carbon #1 in aldoses, usually right next to oxygen in ring).
- If the –OH on anomeric carbon is down (trans to CH₂OH) → α
- If the –OH on anomeric carbon is up (cis to CH₂OH) → β

Note: For glucose-type rings, CH₂OH is up (on carbon #5).

Let’s check each:

1. First ring (left):
- Anomeric carbon (C1): OH is down → α

2. Second ring (middle):
- Anomeric carbon (C1): OH is up → β

3. Third ring (right):
- This is a furanose (5-membered ring). Anomeric carbon is still C1.
- OH on C1 is down → α

Wait — let’s double-check third one.

Actually, in furanose rings, we still look at whether the anomeric OH is on same side as CH₂OH (which is attached to C4 in furanose).

But standard rule: if anomeric OH is opposite to CH₂OH group → α; same side → β.

In third structure:

- CH₂OH is pointing UP (attached to C4).
- Anomeric OH (on C1) is pointing DOWN → so opposite → α

Yes.

✔ Answers: α, β, α

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Final Answer:

Part 1:
Definitions and comparisons provided above.

Part 2:
From left to right: D, L, D, L

Part 3:
From left to right: α, β, α