signalling mechanisms Flashcards
What is the role of signal writers in intracellular signalling mechanisms?
Carries out modification of a specific region (epitope) e.g. kinase activity.
Signal writers are crucial for adding modifications that affect protein function.
Define signal readers in the context of intracellular signalling.
Protein domain binds to modified epitope e.g. binding phosphorylated sequence.
Signal readers interpret the modifications made by signal writers.
What is the function of signal erasers?
Removes the modification and returns protein/molecule to resting state e.g. dephosphorylation.
Signal erasers help reset the signalling pathways.
List the post-translational modifications (PTMs) mentioned.
- Glycosylation
- Ubiquitin-like modification
- Oxidation
- Nitrosylation
PTMs are critical for regulating protein function and activity.
What are the major fatty acids in phospholipids typically composed of in terms of carbon atoms?
14, 16, 18 or 20 carbon atoms.
These carbon chain lengths are vital for membrane structure and function.
What are the properties of unsaturated fatty acids?
- Presence of C=C bonds means they have kinks in their fatty acid chains.
- Do not pack as closely.
- Have fewer attractions between chains.
- Have lower melting points.
- Are liquid at room temperature.
- Most naturally occurring unsaturated FAs have cis configuration.
These properties affect the fluidity and functionality of membranes.
Fill in the blank: The first stage of fatty acid synthesis involves the use of _______ as a building block.
acetyl-CoA.
Acetyl-CoA is a central molecule in metabolism and fatty acid synthesis.
What enzyme catalyzes the conversion of acetyl-CoA to malonyl-CoA?
Acetyl-CoA carboxylase (ACC).
This reaction is the committed step in fatty acid synthesis.
What is palmitate and its significance in fatty acid synthesis?
Principal product of FAS; precursor for other long-chain fatty acids.
Palmitate is a key fatty acid that can be elongated or desaturated.
True or False: Unsaturated fatty acids can be formed by desaturase enzymes.
True.
Desaturase enzymes introduce double bonds into fatty acid chains.
What are the four stages of membrane synthesis?
- Esterification of two fatty acids to glycerol phosphate
- Conversion of phosphatidic acid into diacylglycerol
- Transfer of a polar head group
- Flippase-mediated movement of phospholipids
Each stage is essential for forming functional membrane lipids.
What is the role of flippases in membrane synthesis?
Catalyse the movement of phospholipids from the cytosolic to the endoplasmic leaflet.
Flippases help maintain membrane asymmetry.
What is the first step in cholesterol synthesis?
Conversion of Acetyl-CoA to HMG-CoA by HMG-CoA synthase.
This step is critical for the subsequent production of cholesterol.
What happens when membrane cholesterol levels are high?
Cholesterol binds to the Sterol Sensing Domain, inducing HMG-CoA reductase degradation.
This regulatory mechanism helps control cholesterol synthesis.
Fill in the blank: Statins inhibit _______ to reduce cholesterol levels.
HMG-CoA reductase.
Statins are widely used to manage cholesterol levels and prevent cardiovascular diseases.
List the three proposed mechanisms for lipid transport.
- Vesicular transport
- Transfer mediated by small, soluble lipid transfer proteins
- Lipid transfer mediated by direct contact between membranes
These mechanisms ensure that lipids reach their correct destinations within the cell.
What is cardiolipin and its role in the mitochondria?
An important component of the phospholipids constituting the inner membranes of mitochondria; provides curvature for increased surface area.
Cardiolipin is crucial for the function of the electron transport chain.
What occurs to cytochrome c during mitochondrial-mediated apoptosis?
Release of cytochrome c occurs when it dissociates from cardiolipin due to CL oxidation.
This release is a critical step in the apoptosis pathway.
