Mod 6 Flashcards
Signal transduction
The process of communicating extracellular messages over long or short distances in order to elicit a specific reaction within the targeted cell or tissue
Example of long-distance signal transduction
remote, ex. hormones
Example of short-distance signal transduction
local, ex. neurotransmitters
Four classes of extracellular messengers/signals
and their differences
PHukiNG
- Hormones (act at a distance)
- Neurotransmitters (secretion close to target cells)
- Pheromones (act upon cells in a different organism)
- Growth factors (act at various distances)
How do extracellular messengers/signals have large effects even though they are excreted in small amounts
signal amplification during transduction
Three types of hormones (in vertebrates)
PSA
- Peptides (insulin, glucagon)
- Steroids (vit D, estrogen)
- Amino acid derivatives (epinephrine, thyroxine)
Hormones
small molecules secreted by endocrine glands which travel through the bloodstream and bind to specific receptors on or in target cells
Epinephrine
secreted by?
does what?
adrenal gland
promotes the generation of energy in the form of ATP in muscle when it is required for exercise
Glucagon
secreted by?
does what?
pancreas
acts on the liver to promote glycogen breakdown and gluconeogenesis when blood glucose levels are low
Insulin
pancreas
promotes uptake of glucose into cells when blood glucose levels are high
Three steps of cell signalling
R T CR
- Reception of the extracellular signal
- Transduction of the signal from the outside of the cell to the inside of the cell
- Cellular response to the signal
Signal reception
Ligands (signal molecules) bind to receptors on the surface of a cell or within it
Signal transduction
rter
- signal received by receptor
- activates a transducer protein
- then activates the effector
elicits cellular response
Cell response
- effector causes a second messenger to take off and create a cellular response
What is the first messenger vs. second messenger?
+ examples
First messengers: extracellular ligands or cytokines that activate receptors
ex. hormones, neurotransmitters, cytokines, lymphokines, growth factors and chemical inducers.
Second messengers:
directly or indirectly cause cells to perform physiological functions
ex. cAMP, Ca2+, IP3, DAG
Example of signal transduction: epinephrine
signal: epinephrine
receptor: beta adrenergic receptor (is a GPCR)
transducer: G protein
effector: adenylate cyclase
second messenger: cAMP
Cascade mechanism - epinephrine
Signal amplified because one molecule of epinephrine activates adenylate cyclase to synthesize many molecules of cAMP, which then activate many protein kinase a enzymes, which then each activate many phosphorylase b kinase enzymes and so on and so on until many glycogen phosphorylase enzymes have been activated within the single cell
Receptor tyrosine kinase family
and example
example insulin receptor
- Each have a protein tyrosine kinase domain which is activated when insulin (ligand) binds
- When insulin binds to the receptor, it activates the tyrosine kinase activity which then activates another cascade mechanism whereby PIP3, another second messenger, is synthesized
- At the end of the cascade, GLUT4 (or glucose transporter 4) proteins are relocalized to the plasma membrane and are responsible for taking up glucose from the bloodstream after a meal
Energy metabolism
The pathway involved in the generation or storage of metabolic energy
Three macronutrients → generate energy
- Carbohydrates (sugars)
- Lipids (fats)
- Proteins
Is protein stored in reserves
not really
“stored” as muscle protein
drawn on during periods of starvation
What is the building block of each macronutrient, and what are they stored as
lipids
- free fatty acids (b)
- triglycerides (s)
Carbs
- glucose (b)
- glycogen (s)
Protein
- amino acids (b)
- muscle protein (s)
ATP for energy
ATP broken down into ADP + Pi while releasing free energy
Brain preferred fuel
glucose
Muscle preferred fuel
prefers glucose during high intensity exercise, prefers lipids during rest or low intensity exercise
Catabolism
+ examples
+ generates
+ catalyzed by
ex. glycolysis and citric acid cycle
breakdown of macronutrients; large complex macronutrients are broken down to smaller simple compounds
oxidative degradation of carbs, lipids, and proteins
generates reducing equivalents (NADH and FADH2) and energy (ATP)
catalyzed by dehydrogenases
Anabolism
+ example
+ uses
+ catalyzed by
ex. gluconeogenesis
synthesis of complex biomolecules
reductive biosynthesis of carbs and lipids
uses reducing equivalents (NADPH) and energy (ATP)
catalyzed by reductases
produces ADP and Pi
Metabolism
Catabolism + anabolism
= degradation + synthesis
Pathway
(enz)
sequential series of reactions in a cell that are catalyzed by enzymes
