Proteins Flashcards
(44 cards)
Describe the basic structure of amino acids
Amino acids all have the same basic structure different only in their side chain (the r group)
Define stereoisomerism in the context of amino acids
Most naturally occurring amino acids have L configuration which is the opposite configuration from sugars
How can amino acids be characterised based on their side chains?
Amino acids can be characterised into hydrophobic (non-polar, such as alkyl groups or aromatic rings) And hydrophilic (Polar, include uncharged chains with polar groups negatively charged chains and positively charged chains).
Explain the effect of pH on amino acids
The overall charge of amino acids depends on which chargeable groups are charged which is influenced by the pH of the solution relative to the PKA values of those groups
What is the general rule regarding PH and PKA values for amino acids?
If the pH of a solution is less than the PKA, the H + is on (charged); if the pH is higher than the PKA, the H + is off (uncharged)
Describe the significance of natural peptides
Natural peptides, such as enkephalin (opioid), insulin (hormone), and various venoms, have important biological functions
What is a synthetic peptide example and it’s relevance
Aspartame is a synthetic dipeptide sweetener that contains phenylalanine and aspartic acid, which must be avoided by individuals with PKU due to their inability to metabolise phenylalanine
Define a peptide bond
A peptide bond is formed through a condensation reaction, resulting in a bond with double bond characteristics that restricts rotation and limit the secondary structures of the peptide chain
How is protein structure described?
Protein structure is best described as levels of structure including primary secondary territory and quaternary structures. The primary structure refers to the amino acid sequence, while secondary structures like alpha Helices and beta sheets arise from hydrogen bonding. Tertiary and quaternary structures involve complex folding and interactions between multiple polypeptide.
What constitutes the primary level of protein structure?
Their primary level of protein structure consists of the amino acid sequence and chain length, involving covalent peptide bonds Lincoln the amino acids together.
How does the primary structure of a protein influence its properties?
The primary structure determines the physiological, structural, and biological properties and functions of a protein
Describe the secondary level of protein structure
The secondary level of protein structure refers to the arrangement and space of the atoms in the backbone of the protein influenced by the geometry of the peptide bond and local hydrogen bonding.
Define the main types of secondary protein structures
The main types of secondary protein structures are alpha helix, beta pleated sheet, and random coil or irregular structure
How does the secondary structure contribute to protein properties?
The secondary structure adds properties such as strength and flexibility to the protein.
Explain the stabilisation of the alpha helix structure
The alpha helix is stabilised by hydrogen bonds formed between the amide hydrogen of one peptide bond and the carbonyl oxygen off another peptide bond located in the next turn of the helix.
What is the orientation of side-chain R groups in an alpha helix?
In an alpha helix, the bulky side chain (R) groups are directed outwards.
Describe the beta pleated sheet structure
In a BETA pleated sheet, the peptide chain adopt the confirmation of a sheet of paper, and the structure is stabilised by hydrogen bonds between peptide bonds.
What is the result of large amounts of alpha helix in a protein?
Large amounts of alpha helix result in a strong, insoluble, fibrous, and flexible protein.
What is the tertiary level of protein structure?
The tertiary level of protein structure involves further folding of the secondary structure to give an overall three dimensional shape, influenced by side chain interactions.
Identify the types of interactions involved in tertiary protein structure
The interactions involved in tertiary protein structure include disulphide cross links, hydrophobic attractions, hydrogen bonding, and iconic bonding
How does protein function relate to its structure?
Protein function, such as enzyme activity, as derived from it three dimensional structure (conformation)
Define the quaternary level of protein structure?
The quaternary level of protein structure refers to proteins that consist of more than a single peptide strand, which may exist as dimers, trimers, tetramers etc. Often off identical subunits.
Describe the structure of globular protein
Globular proteins are intricately folded with the hydrophobic side chains tucked inside, making them water soluble and roughly spherical in shape
Define myoglobin and its function?
Myoglobin is the oxygen-holding protein in muscle tissue, consisting of one polypeptide unit that is primarily an alpha-helix and contains a prosthetic group called haem for oxygen binding.
