Exam 3: Cell-cell interactions (Class 2) Flashcards
What are the five categories of signaling?
- direct intercellular signaling
- contact-dependent signaling
- autocrine signaling
- paracrine signaling
- endocrine signaling
What is direct intercellular signaling?
Cell junctions allow signaling molecules to pass from one cell to another at rate of diffusion (via gap junction)
What type of junctions are used in direct intercellular signaling?
Gap junctions
How does contact dependent signaling work?
Receptors on adjacent cells bind to other cell surface molecules
What do the cell surface molecules in contact dependent signaling function as?
Signals
What is the difference between direct intercellular signaling and contact dependent signaling?
Direct intercellular: passed from cytoplasm to cytoplasm
Contact dependent: adjacent cell membranes
What is autocrine signaling?
Cells secrete signaling molecules that bind to its own surface or other neighboring cells
What is paracrine signaling?
Same as autocrine, but no receptors so a cell cannot receive its own signal
Endocrine signaling
Signals travel long distance through blood stream, take a long time to fade
What are the 4 stages of cell signaling?
- Signal reception
- Signal processing/transduction
- Signal response
- Signal deactivation
What occurs in signal reception (step 1)?
Signal receptors are bound
What are the two type of signals
- Hormones
- Other cell-cell signals
The presence of what dictates which cells will be able to respond to a particular hormone
appropriate receptor proteins
What does protein function depend on? (3 factors)
- Binding
- Shape
- Location
When the signal binds to the receptor, what happens to the receptor
It undergoes a conformational change
Signal receptors that bind to lipid-soluble hormones are located where
Inside the cell
Signal receptors that bind to non lipid-soluble hormones are located where
in the plasma membrane
Lipid-soluble steroid hormones are ___ soluble in water
less
Estrogen, progesterone, glucocorticoids, and ecdysone are examples of what
hormone response elements
The hormone receptor complex binds to…
the hormone response elements (HRE)
Where is the hormone-receptor complex transported to and for what
the nucleus, for altering gene expression
Are lipid-soluble hormones hydrophilic or hydrophobic
hydrophobic
Are lipid-insoluble hormones hydrophilic or hydrophobic
hydrophilic
When a signal binds at the cell surface, it triggers a complex series of events called a …
signal transduction pathway
After the receptor undergoes a conformational change once a lipid-insoluble hormone binds to it, what happens
A secondary messenger is released
What happens once the second messenger is released
It can be amplified
Signal transduction moves information from where to where
From the cell surface to the nucleus/other targets
What are the three kinds of cell surface receptors?
- G-protein coupled receptors (GPCR)
- Enzyme-linked receptors
- Ligand-gated ion channels
All of the three kinds of cell surface receptors are what type of membrane protein
Integral
How many transmembrane segments do GPCRs have?
7
When G-proteins are bound to GTP, the G-protein is ___
on
When G-proteins are not bound to GTP, the G-protein is ___
off
What is the first step for GPCRs
Signal received
What is the second step for GPCRs
G protein binds GTP and splits
What is the third step for GPCRs
The activated G protein binds to an enzyme, which catalyzes the production of a secondary messenger
GPCRs are found in all _____ and are common in _____
eukaryotes, animals
What are the two parts of an enzyme-linked receptor?
Extracellular domain and intracellular domain
Which domain of enzyme-linked receptors binds the signal?
Extracellular
Which domain of enzyme-linked receptors becomes a functional catalyst?
Intracellular
Most enzyme-linked receptors are ___
kinases
What are the two types of receptor kinases?
- Receptor tyrosine kinase (RTK)
- Receptor serine/threonine kinase (RSTK)
What is the first step of RTK catalyzing a reaction?
Hormone binds to an RTK, signal received
What is the second step of RTK catalyzing a reaction?
RTK forms a dimer and is phosphorylated by ATP
What is the third step of RTK catalyzing a reaction?
Ras protein exchanges its GDP for GTP, while it is bridged to RTK
What is the fourth step of RTK catalyzing a reaction?
Ras protein triggers the phosphorylation and activation of another protein
What is the fifth step of RTK catalyzing a reaction?
Phosphorylation cascade amplifies the signal many times
What is phosphorylation cascade?
Sequence pathway where one enzyme phosphorylates another and so on
Which type of cell surface receptor is found both in plant and animal cells?
Ligand-gated ion channels
What is another name for a signal
ligand
What happens when a ligand binds to a ligand-gated ion channel
The ion channel opens and ions flow in through the membrane
In animals, synaptic signals are between ___ and _____ or between two _____
Neurons and muscles or between two neurons
What are three examples of signal response (stage 3)?
- change enzyme activity
- change function of structural proteins
- change gene expression or regulation
What are two factors that can alter signal deactivation
- concentration of hormones
- number and activity of signal receptors
