Questions Flashcards
Describe transduction in cell signalling
- Transduction: When the signalling molecule binds the receptor it changes the receptor (e.g. conformation or phosphorylation).
- This change initiates the process of transduction. Signal transduction is usually a pathway of several steps (e.g. kinase cascades).
- Each relay molecule in the signal transduction pathway changes the next molecule in the pathway (e.g. through phosphorylation).
Name three types of pst translational modifications of PROTEINS
- Glycosylation (in Golgi) targets proteins to plasma membrane
- Phosphorylation can alter protein-protein interactions leading to re-
distribution to other compartments (using adaptor proteins) - Ubiquitination sends proteins for breakdown in the
proteasome/lysosome.
Describe response in cell signalling
- Response: Response can lead to regulation of gene expression (turning transcription of specific genes on or off).
- Response could also regulate the activity of a protein, for example opening or closing an ion channel in
the plasma membrane or promoting a change in cell metabolism such as catalysing the breakdown of glycogen. - Also possible: important cellular events such as cell division or apoptosis.
Apoptosis cell level
- Cell shrinks - chromatin condenses
- Membrane blebbs
- Nucleus and organelles collapse
- Apoptosic bodies form
- Macrophages engulf
Reason why enzyme kinetic graph plateaus
- Reverse reactions
- Product inhibition
- Substrate depletion
Effect of enzymes on kinetics
What is the biological function of protein signal sequences? (2 marks)
To target proteins to a specific area of the cell, so that they may perform their biological function
Are non polar molecules hydrophilic or hydrophobic
- Nonpolar molecules are hydrophobic, can dissolve in the lipid bilayer and pass through the membrane rapidly.
- A non polar molecule has no charge so repels water
Briefly describe the function of the extracellular matrix (ECM) (2 marks)
The ECM provides structure, mechanical and biochemical support for the tissues connective tissue
Which ONE of the following is TRUE for chylomicrons?
- They are transported through lymphatic vessels from the intestine to the blood circulation
- Its a type of lipoprotein
Stimulation of glycogen breakdown by exercise in muscle?
- Muscle activity stimulates release of adrenaline
- Excercise generates AMP
- AMP binds to (allosteric site) of inactive (T) glycogen phosphorylase b and promotes formation of the active form
- OR same but with Ca2+
How do liver and skeletal muscle cells use the products of glycogen differently?
- Skeletal muscle uses glucose-6-phosphate to undergo glycolysis
- Liver: glucose-6-phosphate → glucose → blood glucose (brain)
What is mixed inhibition?
- Its similar to non-competitive inhibition. However, the binding of the substrate or the inhibitor or substrate effects the affinity of each other for the enzyme
- This means binding of the substrate to the inhibitor is reduced in the presence of the inhibitor
- Inhibitor effects both Km and Vmax
Name all the levels which gene can be regulated in eukaryotes (summary)
- Alteration of gene structure (Euchromatin vs heterochromatin)
- Transcriptional control (whether RNA is created or not)
- mRNA processing (post transcriptional modification/splicing)
- Stability of RNA (degredation of mRNA by siRNA or miRNA)
- Translational control (whether its translated or not)
What causes lactose intolerance
In infants its caused by mutation in LCT
