Cell Signaling
What are the major components of cell signalling?
Ligand - signalling molecule sent by cell sending the signal
Receptor - protein that is attached to the cell receiving the signal
What subunit of the G-Protein activates the next part of the pathway?
What happens to the other subunits?
Alpha subunit binds to the GTP and activates AC
Beta and Gamma subunits remain attached to the membrane and allow the Alpha subunit to bind again once the GTP is removed.What are the 3 divisions of the cytoskeleton?
What are the protein subunits they are made up of?
Microtubules - tubulin dimers (froms hallowed tube)
Intermediate filaments - varies (keratin for skin, nuclear lamina - nucleus)
Microfilaments - actin (forms helix)
What is the process that allows for genetic diversity?
Crossing over between homologous chromosomes.
What are the different types of signalling?
What are examples of each?
Autocrine - ligand is produced and received by the same cell (Growth Factors - can be cancerous)
Paracrine - Ligand is received by a cell in close proximity to the cell that produced the ligand (Neuron signalling)
Endocrine - Ligand travels a long distance (through the bloodstream) to reach the receptor cell (Hormones - Adrenaline)
What is the first messenger?
What is the second messenger?
First - ligand (signaling molecule)
Second - cAMP (produced by adenylyl cyclase after the ligand produced some conformation change in the receptor)
Microtubules - cilia, flagella, division spindles, intracellular movement
Intermediate - structural support
Microfilaments - contractile ring, microvilli, general whole cell movement
What is the difference between sister chromatids and homologous chromosomes?
Sister chromatids are copies of replicated DNA connected at the centromere (make up 1 chromosome)
Homologous chromosomes encode the same set of genes, each set received from each parent
What characteristics would a ligand need to have to utilize an cell-surface receptor?
What is another type of receptor?
The ligand would need to be unable to pass through the membrane on it's own, so the hydrophobic interior of the membrane must prevent simple diffusion. So the molecule must be Polar / Large.
Another type is intracellular (used by small, non polar)
What is the general pathway of the G-protein pathway, starting with the ligand and ending with the Protein Kinase A (PKA)?
Ligand -> G-protein receptor -> G-Protein -> Adenylyl Cyclase (cAMP) -> PKA
What kind of junction would a cell use to connect to another cell? What kind of protein does this use?
What about connection to a non cell membrane?
Adherens Junctions connect to another cell using Cadherins (connect to each to other extracellularly and connect to microfilaments in each cell)
Connecting a cell to a non cell membrane would use integrans.
Which stage of Meiosis and Mitosis are similar? Why is the other stage of Meiosis different?
Phase II of Meiosis and Mitosis are similar, the separation of the sister chromatids occurs here.
Phase I of Meiosis involves the separation of Homologous Chromosomes connected at the Chiasma
What does it mean for a signal to be amplified?
Defined as the increase in intensity of a signal through intracellular interactions.
Ex. G-Proteins, a signal activates a protein which allows activation of more proteins that activate more proteins (1 protein activates 2 proteins that each activate 4 proteins, ect.).
A mutation of the G protein–coupled receptor removes the extracellular domain of the receptor. The amount of cAMP in cells will...
2. Decrease
If the extracellular domain of the G-Protein is removed, there will be no association between the ligand and the receptor. Without this association, there will be no activation of the receptor, the G-Protein, or the AC (therefore less cAMP production).
Which types of cytoskeleton have motor proteins associated with them?
What are they?
Microfilaments - Myosin
Microtubules - Kinesin (+) and Dynein (-)
What is the term that can lead to Trisomy 21 (Down Syndrome)?
Non disjunction
in Meiosis 1, the Homologous do not separate and go into the same daughter cell.
What does the term "Phosphorylation" and "Dephosphorylation"?
What are the 2 types of proteins that utilize mechanism related to phosphorylation.
Phosphorylation - adding phosphate group
Dephosphorylation - removing phosphate group
adding and removing a phosphate changes the conformation of the protein activating it (adding phos.) or deactivating it (removing phos.).
Kinase - adds phosphate
Phosphatase - removes phosphate
A mutation in the αlpha subunit of the G protein that prevents the release of bound GTP. The amount of cAMP in cells will:
1. stay the same
2. increase
3. decrease
2. Increase
The αlpha subunit releases from the AC by the GTP being dephosphorylated to GDP. Without releasing the GTP, the alpha subunit will remain associated with AC and the cAMP will keep being produced.
You are told that a cell junction connects 2 cells using cadherins and connects to intermediate filaments in the cytosol in each cell.
What type of junction is described?
1. Adherens
2. Gap
3. Tight
4. Desmosome
connecting 2 cells, uses cadherins and connects intermediate filaments in the cytosol
4. Desmosomes
What is the amount of DNA that is present in each cell at the end of each stage (Mitosis, Meiosis I, and Meiosis II)?
Mitosis - Diploid
Meiosis I - Haploid
Meiosis II - Haploid