Homeostasis-Blood Glucose Flashcards
homeostasis
the regulation of a cell or organism to maintain stable optimum conditions in response to internal and external changes.
why is it important that core temperature remains stable
-to maintain stable rate of enzyme-controlled reactions & prevent damage to membranes.
-temperature too low= enzyme & substrate molecules have insufficient kinetic energy
-temperature too high= enzymes denature
why is it important that blood pH remains stable
-maintains stable rate of enzyme-controlled reactions (&optimum conditions for other proteins)
-acidic pH= H+ ions interact with H-bonds & ionic bonds in tertiary structure of enzymes, so shape of active site changes, ES complexes cannot form.
why is it important blood glucose concentration remains stable?
-maintains stable blood water potential: prevent osmotic lysis/ crenation of cells.
-maintains constant concentration of respiratory substrate: organism maintains constant level of activity regardless of environmental conditions.
negative feedback
when any deviation from the normal values are restored to original level.
positive feedback
a fluctuation triggers changes that result in an even greater deviation from the normal level.
general stages involved in negative feedback
receptors detect deviation -> coordinator-> corrective mechanism by effector-> receptors detect that conditions have returned to normal.
why do seperate negative feedback mechanisms fluctuate in different directions
provides more control, especially in case of ‘overcorrection’, which would lead to deviation in the opposite direction from the original one.
why is there a time lag between hormone production and response by an effector?
it takes time to:
-produce hormone
-transport hormone to the blood
-cause required change to target protein
what happens when blood glucose concentration increases
-increase in blood glucose is detected by beta cells in islets of Langerhans (pancreas)
-beta cells secrete insulin into bloodstream
-insulin binds to surface receptors and make liver cells more permeable to glucose, enzymes are activated for glycogenesis (liver & muscles)
-glucose is removed from blood and stored as glycogen in cells.
what happens when blood glucose concentration decreases
-detected by alpha cells in islets of Langerhans
-alpha cells release glucagon, adrenal gland releases adrenaline
-second messenger model occurs to activate enzymes to hydrolyse glycogen.
-glycogen is hydrolysed into glucose and more glucose is released back into blood.
glycogenesis
liver converts excess glucose into glycogen when blood glucose is higher than normal
glycogenolysis
liver hydrolyses glycogen into glucose which can diffuse into blood, when blood glucose lower than normal
gluconeogenesis
process of creating glucose from non-carbohydrates (glycerol & amino acids) in liver. happens when glycogen supply is exhausted.
role of insulin in regulating blood glucose
beta cells in islets of langerhan detect when blood glucose is too high and secrete insulin. Insulin will decrease blood glucose in the following ways:
-attaching to the receptors on the surfaces of target cells. ->changes the tertiary structure of the channel proteins, resulting in more glucose being absorbed by faciliated diffusion.
-more protein carriers are incorporated into cell membranes so more glucose is absorbed into cells from blood
-activating enzymes involved in conversion of glucose to glycogen->results in glycogenesis in liver.
