W2 Proteins & Enzymes Flashcards
How does cysteine differ compared to amino acids?
The sulfhydryl group forms disulfide bonds or bridges by covalently linking two sulfur atoms from separate cysteine residues, which can stabilize the structure of proteins by linking different parts of the same polypeptide chain or different chains
How do disulfide bridges affect the shape of polypeptides?
Disulfide bridges stabilize and constrain the shape of polypeptides by forming covalent links between different parts of a polypeptide chain or between different polypeptide chains
Explain the primary, secondary, tertiary, and quaternary structures of proteins
Primary: The linear sequence of amino acids in a polypeptide chain
Secondary: Regular local structures within a polypeptide chain, such as alpha-helices and beta-pleated sheets, stabilized by hydrogen bonds
Tertiary: The overall three-dimensional shape of a single polypeptide chain, including interactions between secondary structures, hydrophobic interactions, ionic bonds, and disulfide bridges
Quaternary: The arrangement and interaction of multiple polypeptide chains in a multi-subunit protein
What is the function of insulin and how is its structure related to its function?
Insulin is a hormone composed of two polypeptide chains linked by several disulfide bridges, which is crucial for regulating blood glucose levels
How do enzymes speed up chemical reactions?
Enzymes speed up reactions by lowering the activation energy required for the reaction to proceed, often through forming enzyme-substrate complexes at their active sites
List and briefly describe three experimental techniques used to determine protein structures
X-ray Crystallography: Used to determine the atomic structure of a protein by analyzing the diffraction pattern of X-rays passing through a crystal of the protein
NMR Spectroscopy: Used to determine the structure of proteins in solution by measuring the interactions of nuclear spins
Cryo-Electron Microscopy: Allows for the visualization of proteins at near-atomic resolution by rapidly freezing them and imaging them with an electron microscope
What’s the difference between the induced fit model and lock and key model?
- Lock-and-Key Model: The enzyme’s active site is complementary in shape to the substrate, allowing only specific substrates to bind
- Induced Fit Model: The enzyme’s active site undergoes a conformational change upon substrate binding, which enhances the fit between enzyme and substrate
What 2 factors can influence enzyme activity, and how do they affect enzyme function?
- Temperature: Enzymes have an optimal temperature range; temperatures too high can denature the enzyme, while too low can reduce activity
- pH: Enzymes have an optimal pH range; deviations can alter the charge of amino acids, affecting enzyme structure and function
- concentration - too much can cause denaturation / oversaturation
What are cofactors and coenzymes?
Cofactors: Non-protein molecules (e.g., metal ions) that assist enzyme activity
Coenzymes: Organic molecules (e.g., vitamins) that act as carriers of chemical groups or electrons
What are competitive and non-competitive inhibitors, and how do they affect enzyme activity?
Competitive Inhibitors are molecules that resemble the substrate and compete for the active site, reducing enzyme activity
Non-Competitive Inhibitors are molecules that bind to an allosteric site (not the active site) - changing the enzyme’s shape and reducing its activity regardless of substrate concentration.
Describe the concept of enzyme saturation and its implications for enzyme kinetics
Enzyme saturation occurs when all enzyme active sites are occupied by substrates, leading to a maximum reaction rate (Vmax).
The Michaelis-Menten equation describes how the reaction rate changes with substrate concentration
What are the main components of nucleotides?
- phosphate group
- pentose sugar
- nitrogenous base
Describe the structural differences between DNA and RNA
DNA: Double-stranded with deoxyribose sugar and bases A, T, G, C; forms a double helix with complementary base pairing
RNA: Single-stranded with ribose sugar and bases A, U, G, C; does not have thymine
What is the significance of Chargaff’s rules?
Chargaff’s rules state that the amount of guanine equals cytosine, and adenine equals thymine in DNA, which supports the base-pairing mechanism of the double helix structure
What is ATP, and what is its role in cellular processes?
ATP (adenosine triphosphate) is the primary energy carrier in cells. It releases energy by hydrolyzing its third phosphate group, driving various biochemical reactions.
