9700 · 2.3
Proteins flashcards
Revision flashcards for Cambridge 9700 Proteins (syllabus 2.3). Flip, recall, then mark a real past-paper question.
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What are the four components bonded to the central carbon of a general amino acid?
1. An amino group (-NH₂) 2. A carboxyl group (-COOH) 3. A hydrogen atom (-H) 4. A variable R-group
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What type of bond links amino acids together, and what type of reaction forms it?
A **peptide bond** is formed by a **condensation** reaction (which releases a water molecule).
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What is the primary (1°) structure of a protein?
The specific sequence, number, and type of amino acids in a polypeptide chain.
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Name the two common types of secondary (2°) protein structure.
The α-helix (alpha-helix) and the β-pleated sheet (beta-pleated sheet).
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What type of bond is primarily responsible for stabilising the secondary structure of a protein?
Hydrogen bonds forming between the -C=O and -N-H groups of the polypeptide backbone.
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Name three types of bonds or interactions that stabilise the tertiary (3°) structure of a protein.
Any three from: Hydrogen bonds, ionic bonds, disulfide bridges, and hydrophobic interactions (between R-groups).
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What is a prosthetic group? Give an example.
A non-protein component that is tightly bound to a protein and is essential for its function. Example: The haem group (containing iron) in haemoglobin.
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Compare the solubility and function of globular vs. fibrous proteins.
Globular proteins are generally soluble and have functional/metabolic roles (e.g., enzymes, haemoglobin). Fibrous proteins are insoluble and have structural roles (e.g., collagen, keratin).
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Describe the quaternary structure of haemoglobin.
Haemoglobin is made of four polypeptide subunits: two alpha-globin chains and two beta-globin chains. Each subunit contains a prosthetic haem group.