Proteins and Enzymes Flashcards
What are the four groups of an amino acid?
- Central “alpha” carbon.
- Amino group
- Carboxylic acid group
- R group
What are the 2 main traits to categorise amino acids with?
- Acidic / basic
- Polar / non-polar
Peptide bonds form between the ______ group of one amino acid and the ______ group of another.
Carboxyl, amino.
What is lost when peptide bonds form?
Water.
Peptides have polarity - a _____ terminus and a ______ terminus.
Amino (A), carboxyl (C)
The order of amino acids is the _______ peptide structure.
Primary.
What are the two arrangements of secondary structure?
- Alpha helix
- Beta sheet
Does tertiary structure include side chains?
Yes.
Fibrous structures are often insoluble in water. True or false?
True.
Globular structures have hydrophobic interiors. True or false?
True.
Globular structures are mainly alpha-helices. True or false?
False.
Active site bonding in enzymes occurs via which 3 weak forces?
- Van der Waals forces
- Ionic forces
- Hydrogen bonds
Catalysis makes chemical reactions happen. True or false?
False. Speeds ‘em up.
The catalyst is consumed upon reaction. True or false?
False.
The amount of energy in a system that can be converted into work is called:
Free energy.
Activation energy is independent of free energy. True or false?
True.
Do products or substrates have lower free energy?
Products, thus they are favoured for equilibrium.
Enzymes lower the _____ energy for a reaction.
Activation.
How do enzymes lower activation energy?
Assisting in the formation of reaction intermediates.
Induced fit models are oversimplistic compared to lock-and-key. True or false?
False.
In the induced fit model, the binding of ______ changes the shape of the _______ to favour a transition state.
Substrate, active site.
Km is the ______________ constant.
Michaelis-Menten.
What is the Michaelis-Menten constant?
The substrate concentration at which reaction rate is half its maximal rate.
Do enzymes all have different Km values?
Yes.
What is turnover?
The number of substrates converted to products per second.
Reaction velocity is affected by substrate concentration. True or false?
True.
High Km corresponds to low enzyme affinity for substrate. True or false?
True.
Low Km means more substrate is required. True or false?
False. Low Km = high affinity.
What is the main issue with Michaelis-Menten plots?
Vmax is approached asymptotically, which is unrealistic.
The ______________ plot is the double _______ of the Michaelis-Menten plot.
Lineweaver-Burk, reciprocal.
A kinetically-perfect enzyme would only be limited by the rate it encounters product. True or false?
False - the rate it encounters substrate, not product.
Reaction velocity is proportional to substrate concentration when concentration is low or high?
Low.
Where does the inhibitor bind in competitive inhibition?
Active site.
In competitive inhibition, there is higher Vmax but lower Km. True or false?
False - same Vmax, higher Km.
Where does the inhibitor bind in non-competitive inhibition?
Inhibition site.
What does non-competitive binding to the inhibition site do?
Alters shape of active site.
In non-competitive inhibition, the amount of functional enzyme is lower - do Vmax or Km change?
Vmax is lower, Km is the same.
What separates allosteric enzymes from non-competitive inhibition?
Cooperativity - multiple active sites that increase activity at the others.
Allosteric enzymes show _____ kinetics (shape-wise).
Sigmoidal.
What are zymogens?
Inactive precursors to enzymes.
