Biochemistry Quiz on Amino Acids and Peptides

Proteins are the most abundant and diverse molecules in living organisms, playing crucial roles in virtually every life process.

Proteins are linear polymers made up of amino acids linked together in a specific sequence.

Amino acids are organic molecules that contain both an amino group (-NH2) and a carboxyl group (-COOH).

Each amino acid (except proline) has a central carbon atom (α-carbon) bonded to an amino group, a carboxyl group, a hydrogen atom, and a unique side chain (R-group).

At a pH of 7.4 (physiological pH), the carboxyl group loses a proton (H+) to become negatively charged (-COO-), while the amino group gains a proton to become positively charged (-NH3+).

Amino acids are classified based on the properties of their side chains, which determine their role in a protein. Amino acids can be classified as non-polar, uncharged polar, acidic, or basic.

Each amino acid has a unique 3-letter and 1-letter abbreviation.

The properties of the side chains are crucial in determining a protein's structure and function, influencing interactions between amino acids and how the protein folds.

These amino acids have R groups that contain a basic amine group, making them positively charged in solution. They play important roles in protein structure and function.

Lysine, Arginine, and Histidine are the three amino acids classified as basic.

Lysine has a second amino group at the ε position on its R chain, making it a strong base.

Arginine's R chain contains a positively charged guanidinium group, which is a strong base.

Histidine has a positively charged imidazole group that can readily donate or accept protons, making it an important part of enzyme active sites.

The positive charge of basic amino acids contributes to their hydrophilicity, making them more likely to be found on the surface of proteins interacting with the aqueous environment.

Basic amino acids play critical roles in enzymatic reactions. They can act as proton donors or acceptors within the enzyme's catalytic site, aiding in the conversion of substrates to products.

The presence of basic amino acids influences the overall charge and shape of proteins, influencing their interactions with other molecules and their function within the cell.

These essential amino acids are like building blocks for essential functions in the body, but your body can't create them on its own, so you need to get them from your diet.

These semi-essential amino acids are kind of like 'helpers' for growth and protein synthesis. Adults can create some of them, but kids need more than their bodies make so they need to get them from food.

These non-essential amino acids are like handy tools that your body already has, making them for its own use.

Glycogenic amino acids are like building blocks that can directly turn into sugars to give your body energy.

Ketogenic amino acids are like special ingredients that can turn into fat for long-term energy storage.

These special amino acids are like multi-purpose ingredients, able to turn into both energy and fat, depending on your body's needs.

All amino acids have a central carbon atom that's like a crossroads, and it can be twisted in two different ways. Think of them like mirror images of each other.

Glycine is a unique amino acid with no twist in its central carbon, making it different from all other amino acids.

Selenocysteine is an unusual amino acid. It's incorporated into proteins during translation, not directly from the genetic code. Instead, it's added later, using a specific tRNA.

It's the only amino acid synthesized directly from serine. It then undergoes a complex series of reactions involving a special enzyme and tRNA.

They are not incorporated into proteins but have diverse functions within the cell. Examples include ornithine and citrulline, which are involved in the urea cycle.

Amino acids are like LEGO bricks for building proteins. They form long chains called polypeptides, which can fold into complex structures.

Amino acids are multi-talented molecules. While they build proteins, they also play roles in various metabolic processes. For instance, they are precursors for crucial molecules like hormones and neurotransmitters.

Most amino acids are readily dissolved in water but struggle to dissolve in organic solvents.

Amino acids have high melting points, often above 200°C, because they form strong bonds.

All amino acids, except glycine, have a mirror-image form due to the presence of a carbon atom with four different groups attached.

Amino acids act as ampholytes because they can both accept and donate protons (H+) due to their acidic (-COOH) and basic (-NH2) groups.

Zwitter ions, also called dipolar ions, have both positive and negative charges within the same molecule. Amino acids are commonly found in this form.

4-Hydroxyproline and 5-hydroxylysine are found in plant cell walls and collagen, respectively. They're created by modifying existing amino acids.

γ-Carboxyglutamate is essential for blood clotting and other functions that bind calcium ions (Ca2+). It's found in proteins like prothrombin.

Desmosine, a molecule derived from four lysine residues, provides elasticity to proteins like elastin, found in tissues.