What are the primary functions of proteins?
- catalyze biochemical reactions
- transport molecules
- transmit signals
- offer mobility
- provide structural support
Proteins perform essential roles in biological systems, distinguishing them from DNA.
What tools are used to determine protein 3D structures?
- NMR for small proteins
- X-ray diffraction requiring protein crystals
These techniques allow scientists to visualize protein structures at the atomic level.
What does the primary sequence of a protein provide?
All the necessary information to achieve its native conformation, but is necessary, not sufficient.
The sequence dictates how the protein folds but does not guarantee correct folding.
What are the two main pathways for protein folding?
- random trial pathway
- chaperone and ATP-dependent pathway
Heat shock proteins such as GroEL and GroES assist in the folding process.
What can lead to the denaturation of proteins?
- heat
- UV radiation
- 6M urea
Disruptions in folding pathways can cause proteins to lose their functional structure.
How can denatured proteins be correctly refolded in vitro?
Through dialysis.
This process can help restore the functional conformation of proteins.
How are misfolded proteins removed from the cell?
By proteasomes in a ubiquitin-dependent manner.
Ubiquitin tags misfolded proteins for degradation.
What are the key components of the proteasomal structure?
- ubiquitin label for recognition
- proteasomal structures
These components work together to ensure the degradation of misfolded proteins.
Name two diseases associated with protein misfolding.
- Alzheimer’s Disease
- Creutzfeldt-Jakob disease
These diseases are linked to the accumulation of misfolded proteins in the brain.
What are the steps involved in the isolation and purification of proteins?
- Cell culture
- Breaking cells and tissues
- Centrifugation and differential centrifugation
- Liquid column chromatography (ion-exchange, gel filtration, affinity)
- Polyacrylamide gel electrophoresis (PAGE)
- Two-dimensional gel electrophoresis
These techniques are essential for studying protein characteristics.
What methods are used for protein measurement and analysis?
- Spectrophotometer
- Mass spectrometry
These tools allow for quantification and detailed analysis of protein samples.
What does the First Law of Thermodynamics state?
Energy can be neither created nor destroyed; total energy in the Universe remains constant.
What is expressed by the Second Law of Thermodynamics?
Events in the Universe have direction.
What is the equation that relates enthalpy (∆H), free energy (∆G), and entropy (∆S)?
∆H = ∆G + T∆S
What characterizes a spontaneous process in terms of free energy?
It has -∆G (exergonic) and proceeds toward a state of lower free energy.
What is the characteristic of a non-spontaneous process?
+∆G (endergonic); cannot occur spontaneously.
What is the role of ATP hydrolysis in cellular processes?
It is used to drive most cellular endergonic processes.
What are enzymes?
Conjugated proteins with nonprotein components that carry out specific biochemical activities.
List the properties of enzymes.
- Required only in small amounts
- Not altered irreversibly during the course of reaction
- Have no effect on ∆G of the reaction
- Substrate specificity (Lock-and-key binding)
What are the mechanisms of enzymatic catalysis?
- Maintaining precise substrate orientation
- Changing substrate reactivity by altering its electrostatic structure
- Inducing strain in the substrate
What does the Michaelis-Menten equation describe?
Reaction rates under various experimental conditions.
What is the Michaelis-Menten equation?
v = Vmax [S] / ([S] + Km)
What does Vmax represent in enzyme kinetics?
The maximum velocity of the reaction.
When is reaction velocity (v) equal to Vmax /2?
When [S] is set at value equivalent to Km.
