Principles of biochemistry Flashcards
What is a protein?
Large molecules, polymers of amino acids
What is an enzyme?
Enzymes are biological catalysts that provide a reaction surface, suitable environment, bring reactants together, position reactants correctly, weaken bonds in reactants, and may provide acid/base catalysis and nucleophiles. They do not change the equilibrium position of the reaction.
Enzymes are crucial for facilitating biochemical reactions without being consumed in the process.
What is the active site of an enzyme?
The active site is a region within an enzyme that fits the shape of substrate molecules, allowing for binding through interactions like hydrogen bonding and hydrophobic interactions.
The active site is essential for enzyme specificity and catalytic activity.
What does the Lock and Key Hypothesis propose?
The Lock and Key Hypothesis proposes that the active site has a rigid shape, allowing for an exact fit between the substrate and the active site, forming a temporary enzyme-substrate complex.
This model emphasizes the specificity of enzymes for their substrates.
What is the Induced Fit Hypothesis?
The Induced Fit Hypothesis suggests that the active site is flexible and can change its conformation to maximize fit with the substrate, improving catalysis and allowing for a greater range of substrate specificity.
This model accounts for the dynamic nature of enzyme-substrate interactions.
How does pH affect enzyme activity?
Enzyme activity is generally highest at an optimum pH (around 7.4), with activity lost at low or high pH due to disruption of the tertiary structure of the enzyme.
Different enzymes can have varying pH optima based on their physiological roles.
What are cofactors?
Cofactors are nonprotein prosthetic groups that bind to enzymes to maintain the correct configuration of the active site, which can include metal ions and other inorganic factors.
Cofactors are essential for the functionality of many enzymes.
What is the role of coenzymes?
Coenzymes are organic molecules that bind to enzymes by weak interactions and often carry electrons or small groups, many of which are derived from modified vitamins.
Coenzymes play a crucial role in facilitating metabolic reactions.
What is enzyme nomenclature?
Enzyme nomenclature often identifies the reacting substance and describes the enzyme’s function, typically ending in ‘ase’, such as sucrase for sucrose hydrolysis.
Common names may also be used, especially for digestive enzymes.
List the six main classes of enzymes.
- Oxidoreductases
- Transferases
- Hydrolases
- Lyases
- Isomerases
- Ligases/synthases
Each class of enzymes is defined by the type of reaction they catalyze.
What is the function of oxidoreductases?
Oxidoreductases catalyze the transfer of electrons from donors to acceptors and are involved in oxidation-reduction reactions in biochemical pathways.
An example is Lactate Dehydrogenase (LDH), which plays a role in cellular respiration.
What do transferases do?
Transferases catalyze the transfer of a specific functional group between molecules, such as kinases that transfer phosphate groups.
These enzymes are crucial for metabolic processes involving group transfers.
What is the role of hydrolases?
Hydrolases catalyze the cleavage of bonds by the addition of a water molecule, such as lipases and peptidases.
They are important in digestion and metabolic pathways.
What do lyases do?
Lyases catalyze the addition of water, ammonia, or CO2 to double bonds or remove them to create double bonds.
They facilitate reactions that do not involve hydrolysis or oxidation.
What is the function of isomerases?
Isomerases catalyze the interconversion of isomeric forms of a molecule by transferring groups within the same molecule.
This includes conversions between cis and trans isomers.
What do ligases do?
Ligases catalyze the synthesis of new covalent bonds using ATP energy, also known as synthetases.
They are essential for processes such as DNA replication and repair.
What is enzyme specificity?
Enzyme specificity refers to the varying degrees of specificity enzymes have for substrates, recognizing a single substrate, a group of similar substrates, or a particular type of bond.
Enzymes can be classified as having absolute, group, or linkage specificity.
What is feedback inhibition?
Feedback inhibition is a regulatory mechanism where a product late in a series of enzyme-catalyzed reactions inhibits an earlier enzyme in the pathway.
This ensures metabolic pathways are regulated according to the needs of the cell.
What is allosteric regulation?
Allosteric regulation involves effector molecules changing the activity of an enzyme by binding at a second site, which can either speed up (positive allosterism) or slow down (negative allosterism) enzyme action.
This type of regulation is critical for maintaining homeostasis in metabolic pathways.
What are the functions of proteins?
Enzymes- catalyse chemical reactions in cells
Structural support- e.g. collagen support for skin and bones
Hormones- e.g. insulin regulate physiological processes
Cell signalling- Transmit signals within and between cells e.g. growth and differentiation
What is a zwitterion?
An ion that contains both positive and negative charges
What groups do amino acids contain?
Amine (alkali group) and carboxylic acid (acid group)
What happens to an amino acid at a low and high pH environment?
Low pH- becomes a cation (NH3+)
High pH- becomes an anion (COO-)
When amino acids react with themselves they form dimers and trimers. What bond joins these amino acids? What are the enzymes that perform this called?
Peptide bond
Peptidyl transferases
