Chapter 11-12 Flashcards
Local Communication (short distance)
Paracrine signaling involves a cell secreting a chemical that causes nearby target cells to change or act in a different way. The cell can release a growth factor that can cause surrounding cells to grow and multiply. It has rough er because ribosomes translate, and it makes lots of vesicles.
Neurons communication (nervous system) (ex of local signaling)
Neurons release neurotransmitters that affect nearby cells (without entering them). These chemicals move across a small gap between cells (intercellular space), attach to receptors, and interact with another neuron. Neurotransmitters only interact with the receptor attached to the cell.
Direct Contact
Can occur between cells with cell junctions (allow direct contact between cytoplasm of the cells next to them.) Plasmodesmata allows for movement of materials and back.
Immune cells interaction (Direct contact)
Between protein on macrophage and receptor site on T-cell. The cells attack pathogens and receive a signal that a foreign substance or virus. Between white blood cells.
Long distance signaling
Involves the use of hormones. Animals release hormones into the circulatory system. Hormone is meant for a target somewhere else in the body. Ends up in blood stream to travel.
Animals in long distance signaling
Animals release hormones into the circulatory system. The hormones travel to target cells. Ex: Insulin or Estrogen.
Plants in long distance signaling
Plants release hormones that travel in their transport system via vesicles or diffuse into the air as a gas such as Ethylene (a ripening hormone)
Steroid hormone (Animal hormone)
Ex: testosterone and estrogen (lipid soluble). They can get through plasma membrane because of their phospholipid tails.
Modified Amino Acid (Non- steroid hormone or protein hormone and animal hormone)
Ex: thyroxine is a hormone modified from the amino acid and tyrosine. Cannot pass through the plasma membrane and attaches to the cell receptor outside the cell.
Reception (stages of cell signaling)
Starts with the signal (non-steroid) interacting with a receptor site located on the outside surface of the plasma membrane. The non-steroid signals never enter the cell. Once attached it will change the shape of the receptor starting the transduction of the signal which causes a chemical reaction. Receptors are usually proteins in the plasma membrane. (more info page 254)
G- protein- linked membrane receptors (common)
Vary in their binding sites, they recognize and activate different G proteins. G proteins are also found in the plasma membrane. Bacteria can often cause disease by secreting toxins which interfere with G-protein functions.
Tyrosine-kinase membrane receptor
Can activate more than one signal-transduction pathway at one time. There are 2 receptors (initiates 6 different pathways) Important when cells need multiple pathways to be activated. ATP activates tyrosine and initiate second stage.
Ligand-gated ion channels (membrane receptor and pore channel for ions)
Protein pores in a membrane that open or close in response to a chemical signal. This will allow or prevent the flow of ions (ca++ or Na +) into or out of the cell (or organelles- Golgi apparatus or ER). Channel is locked or closed until the ligand is connected which changes the shape which opens channel. (making ions pass through).
Second Messenger
A molecule inside the cell that is needed to trigger and amplify the transduction pathway. They initiate the AMP beginning stage 2. It changes shape and G protein is activated.
Cyclic AMP
cAMP is a derivative of ATP. Adenylyl cyclase found in the plasma membrane. Converts ATP into cAMP. Once phosphates removed, the remaining p will bind. It changes ATP by removing two phosphate groups (AMP)
where is steroid hormone located?
outside the cytoplasm
Where is non steroid hormone located?
in the cytoplasm
Calcium ions removed from the cytosol (second messenger)
Most of the time Ca++ in the cytosol is low because it is pumped into the E.R, the mitochondria and also pumped outside of the cell. When Ca ++ ions flood the cytosol, it is then they are used as a second messenger.
IP3
Acts as a signal, already inside the cell
Transduction (step 2 of cell signaling)
This process takes place in cytoplasm and its purpose is to boost the signal. The cell processes the signal. Transduction pathway often results in a series of chemical reactions (cascading) which amplifies each product. Influences how the cell responds to its environment. Can activate multiple pathways and 2 second messengers.
Types of cellular responses are
- activating an enzyme
- synthesis of a particular enzyme or protein by activating a gene
when cAMP, Ca++ or IP3 is activated or made, it is followed by interacting with a specific enzyme to start the cascading effect of a particular biochemical pathway.
Scaffolding proteins
large relay proteins to which other relay proteins are attached. Scaffolding proteins help increase the signal transduction efficiency by grouping together different proteins involved in the same pathway.
What can signal transduction cause?
It can result in changes in gene expression and cell function, which may alter the phenotype or result in programmed cell death (apoptosis) .
Mutations in cellular response
hanges (mutations) in any part of the receptor protein or in any step of the signaling process can affect the next steps by disrupting how the signal is passed along.
