Model 1 - Formation of a Peptide Bond: This diagram demonstrates how two amino acids link via a peptide bond to form a dipeptide, highlighting the amine and carboxylic acid groups involved.

Problem Analysis:

The task involves understanding the formation of a peptide bond between two amino acids and identifying functional groups in the process. The document provides a diagram of two amino acids forming a dipeptide through a dehydration reaction. The questions ask for identification of specific functional groups and an analysis of similarities and differences between the amino acids.

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Solution:

#### Model 1 – Formation of a Peptide Bond
The diagram shows the formation of a peptide bond between Amino acid 1 and Amino acid 2. Here is a step-by-step explanation:

1. Amino Acids:
- Each amino acid has a carboxyl group (–COOH) and an amine group (–NH₂).
- The R-group is unique to each amino acid, which determines its chemical properties.

2. Peptide Bond Formation:
- A dehydration reaction occurs between the carboxyl group of one amino acid and the amine group of another.
- Water (H₂O) is released as a byproduct.
- The resulting bond is called a peptide bond, which links the two amino acids together.

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#### Questions and Answers:

1. Examine the amino acids in Model 1.
- a. Circle an amine group in the diagram.
- An amine group is represented as –NH₂.
- In the diagram, the amine group is circled in red for both amino acids.
- b. Draw a triangle around a carboxylic acid (carboxyl) group.
- A carboxylic acid group is represented as –COOH.
- In the diagram, the carboxylic acid group is highlighted with a green triangle for both amino acids.

2. How are the amino acids similar to one another?
- All amino acids share the same basic structure:
- They all have a central carbon atom (α-carbon) bonded to:
- An amine group (–NH₂).
- A carboxyl group (–COOH).
- A hydrogen atom (H).
- An R-group (which varies among different amino acids).
- Answer:
The amino acids are similar to one another because they both have an amine group and a carboxylic acid (carboxyl) group.

3. How are the amino acids different from one another?
- The primary difference between amino acids lies in their R-groups.
- The R-group determines the chemical properties and functionality of each amino acid.
- In the given diagram:
- Amino acid 1 has an R-group of CH₂OH.
- Amino acid 2 has an R-group of CH₃.
- Answer:
The amino acids are different from one another because of their different R groups. (CH₃ & CH₂OH)

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Explanation of Functional Groups:

- Amine Group (–NH₂):
- Found in the amino acid backbone.
- Reacts with the carboxyl group of another amino acid to form a peptide bond.
- Carboxyl Group (–COOH):
- Also found in the amino acid backbone.
- Reacts with the amine group of another amino acid to form a peptide bond.
- R-Group:
- Determines the identity and properties of the amino acid.
- Examples: CH₃ (methyl), CH₂OH (hydroxymethyl).

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Final Answer:

1. Similarities:
- Both amino acids have an amine group and a carboxylic acid (carboxyl) group.

2. Differences:
- The amino acids differ due to their R groups. In this case, the R groups are CH₃ and CH₂OH.

\boxed{
\text{Similarities: Both have an amine group and a carboxylic acid group. Differences: Different R groups (CH₃ & CH₂OH).}
}