Chapter 12 Flashcards
Explain how signal transduction in animals is universal
Considered universal because it involves a set of conserved biochemical processes that enable cells to respond to external and internal signals, regardless of the organism or specific cell type.
Describe Enzyme cascades: amplification
Increase in the signal via activation of additional enzymes in the cascade
Describe Enzyme cascades:
desensitization
Process by which a response ceases after prolonged exposure to the signal
Describe Enzyme cascades:
integration
Multiple signals producing a unified response to maintain homeostasis
Describe Enzyme cascades: divergent
A single signaling molecule or pathway activates multiple, distinct downstream signaling pathways, leading to a variety of different cellular responses.
Describe Enzyme cascades:
response localization
The spatial and temporal regulation of cascades within the cell, ensuring that the signaling event is confined to a specific location or time frame, and preventing unnecessary or widespread activation.
Describe Enzyme cascades:
second messengers
Serve as intracellular signaling molecules that transmit signals from a receptor on the cell surface to target molecules inside the cell.
They act as intermediaries that propagate and amplify signals, allowing cells to respond to external stimuli efficiently.
How would the addition of DTT impact kinetic parameters, if it has an impact at all? and why or why not?
DTT is a reducing agent commonly used in biochemical and enzymatic studies to break disulfide bonds in protein.
Increased Activity: If the enzyme has disulfide bonds that are important for its proper folding or active site configuration, DTT may help to reduce these bonds and possibly activate the enzyme by enabling a more favorable active conformation.
Decreased Activity: Alternatively, DTT could potentially alter the enzyme’s structure in a way that reduces its activity if the disulfide bonds play a role in maintaining a critical structure or the correct active form of the enzyme
if disulfide bonds are crucial for proper folding or maintaining a stable, active enzyme structure, DTT might increase both Vmax and Km if it facilitates more enzyme-substrate interactions.
How to determine which line on a LWB plot is uninhibited?
- Identify which equation of the line represents the highest Vmax. That one is the uninhibited one, and this will always be true if Vmax is not staying the same.
If it were staying the same, then it’s automatically competitive inhibition because that’s the only one where that happens, and at that point the Km values would be what indicates which is inhibited (whichever one is higher would be the inhibited one because competitive inhibition causes Km to increase).
Explain how the catalytic triad functions
ASP, HIS, SER
The ASP is hydrogen bonded to the histidine, and when a hydrophobic amino acid on the substrate docks into the hydrophobic pocket of the enzyme, there is a structural rearrangement of the enzyme that makes the hydrogen bond between these two shorter than normal.
With this “low-barrier hydrogen bond” the pKa of its imidazole nitrogen increases from 7 to around 12 because the Asp is drawing off some of the electronegativity.
Histidine is thus able to act as a powerful general base, activating the serine nucleophile. The histidine base aids the first leaving group by donating a proton, and also activates the hydrolytic water substrate in the “pong” part of the reaction by drawing off a proton as the remaining OH− attacks the acyl-enzyme intermediate.
Explain what happens to DNA when ROS go above an acceptable range
- DNA breaks
-DNA lesions
you can end up with:
-loss (or gain) of function mutations
-loss of genomic integrity that causes pathogenic gene expression profiles (cancer and literally every other disease)
-cell cycle arrest and or senescence (aging)
-cell/organism death
When insulin signaling is activated, what three things happen?
- receptor mobilization of glucose receptors
- Regulate expression of genes involved in growth/replication
- Glycogen production initiation
Contrast the Na/Glucose symporter and the Na/K pump
Na/glucose:
- not really involved in membrane potential
- secondary active transport
Na/K pump: creates/maintains membrane potential
- primary active transport
( 3 Na in/ 2 K out)
Describe how Na+-glucose symporter in epithelial cells is an example of secondary active transport
Located in epithelial cells
transports glucose into the cell along with Na+ ions, using the energy stored in the Na gradient across the membrane.
The Na/K pump establishes a high concentration of Na+ outside the cell and a low concentration inside the cell.
The symporter uses the sodium gradient (secondary active transport) to move both Na+ and glucose into the epithelial cell simultaneously.
The movement of Na+ down its concentration gradient provides the energy to bring glucose into the cell against its concentration gradient.
What is the enzyme responsible for breaking down acetylcholine so the muscle can relax (i.e. it attenuates the signal)
Cholinesterase breaks AcH into
- acetyl-coenzyme A
- choline
Describe the structure function relationship of the acetylcholine receptor, including which type of ion channel this falls under.
a ligand-gated ion channel
A five subunit receptor, with each subunit having four transmembrane helices. The arrangement of subunits forms a central pore that functions as the ion channel.
Upon acetylcholine binding, the channel opens, permitting the passage of cations (mainly Na+ and K+), which leads to depolarization of the membrane and transmission of a signal.
