signalling molecules Flashcards
endocrine signalling
- Long distance.
- hormones
- travels through the blood stream
paracrine siganlling
- travel to nearby cells
- local mediators
autocrine siganlling
- has effect on itself
- eg T cells
direct cell-to-cell contact
from one cytosol to another
what’s apoptosis
programed cell death
What are the 5 things that happen to the cell during apoptosis?
- shrinkage
- blebbing
- nuclear fragmentation
- Chromatin Condensation
- Chromosomal Dna fragmentation
homeostasis
the body’s tendency to maintian a constant internal environment.
-relatively stable equilibrium
negative feedback.
response feeds back and countereacts the change from the set point.
negative feedback in terms of blood glucose levels.
- BG levels arr too high
- receptors on pancreas (beta cells) detect, and insulin is produced.
- insulin stimulates glucose uptake, and the liver converts it to glycogen= lower BG levels
- BG levels are too low
- receptors on pancreas (alpha cells) detect, and glucagon is secreted.
- glucagon stimulates the breakdown of glucogen in the liver, and BG levels increase.
blebbing
cell membrane shows irregular budding
cell shrinkage
cell gets smaller and loses its shape
chromatin condensation
nuclear DNA forms patches against the nuclear membrane
-chonmatin swells up (like in mitosis)
Hormones
Influeces other cells in body. Travel using the bloodstream.
Types of hormones.
–can be: amino acid derivatives (hydrophillic), lipid-derived hormones (hydrophobic), and peptide and protein hormones (hydrophillic).
Properties of hormones (hydrophillic)
can dissolve readily in the water in the blood plasma. it binds to receptor sites on the cell’s surface. Eg: epinephrine.
Porperties of hormones (hydrophobic)
can’t dissolve readily in blood, and therefore uses protien carries to travel to the target cell. It binds to receptor sites inside the target cell. Eg: cortisol
Characteristics of cell undergoing apoptosis
-blebbing, cell shrinkage, nucleus fragmenting, apoptotic bodies (the little vesicles). chromatin condensation, etc.
Intrinsic (mitochondrical) apoptosis pathway
- Depends on factors released by the mitochondria.
- Occurs due to cellular stress.
- Cytochrome C is released from mitochondrial pores, and aggregates other compounds in the cytoplasm to activate caspase 9.
- caspase 9 then activates other caspases (executioners) to “systematically dismantle” the cell.
- after dismantlment, the cell contents are packaged into apoptotic bodies an engulfed by phagocytic cells
Examples of cellular stress?
DNA damage, low O2 levels, viral infection, deprivation of growth factors.
Why does the cell need to be packaged into apoptotic bodies?
To prevent the immune respone from being triggered due to presense of infection.
Caspase
protien digestor enzyme
Extrinsic (death receptor) pathway
- molecules bind to death receptor OUTSIDE cell.
- signal sent when cell’s no longer needed, are being replaced by other cells, or are in excess of current needs.
- a cascade of reactions results in the activation of the executioner caspases, same as inrinsic.
- note that the extrinsic can activate the “intrinsic” response too.
Examples of plant hormone responses?
ripening, growth (size), development (form),
