KIDNEY Flashcards
What happens when temperature is altered?
If body temperature is too low, enzyme activity is reduced, slowing the rate of metabolic reactions. If it is too high, enzymes will denature and metabolic reactions will stop.
What happens when pH is altered?
Above and below the optimum pH the Hydrogen ions can interfere with R- group interactions between amino acids as H+ will cluster around negatively charged R groups and disrupt the Hydrogen bonds and ionic bonds which maintain the tertiary structure of a protein and the shape of the active site.
In extremes of pH changes, the enzyme denatures H+ concentration alters the charges around the active site which may affect the binding of the substrate to the active site in the induced fit hypothesis.
the hydrogen/ionic bonds will break.
The tertiary structure will be altered – changing the active site shape.
What happens when blood glucose is altered?
If blood glucose concentration is too high, the water potential of the blood is reduced to a point where water molecules move out of the cells into the blood by osmosis. This can cause the cells to crenate (shrivel up).
If blood glucose concentration is too low, cells are unable to carry out normal activities because there isn’t enough glucose for respiration to provide ATP.
What is negative feedback?
A process that brings about a reversal of any change in conditions. It ensures that an optimum steady state can be maintained, as the internal environment is returned to its original set of conditions after any change.
What happens in negative feedback?
Any deviation from the norm or set point results in a response being taken which restores the norm. Once the norm is restored, the response is inhibited.
normal level -> level changes from normal ->receptors detect change ->communication via nervous or hormonal system -> effectors respond. LEVEL BACK TO NORMAL
What is positive feedback?
This is a process that increases any change detected by the receptors. It does not lead to homeostasis because it doesn’t keep your internal environment stable. Positive feedback is used to rapidly activate processes in the body.
What happens during positive feedback
normal level -> level changes ->receptors detect change ->communication via nervous or hormonal system -> effectors respond. CHANGE IS AMPLIFIED
What hormones control blood glucose and where are they produces?
by the action of two hormones insulin and glucagon. produced in specialised beta islet celles - insulin
alpha islet cells - glucagon
That happens when there is an increase in blood glucose?
This is detected by the α and β cells within the pancreas. Increased blood glucose (above the norm) causes β cells to release insulin. α cells stop producing glucagon. Insulin lowers blood glucose concentration by binding to receptor proteins found on the plasma membrane of liver (hepatocytes), fat and muscle cells.
- More glucose transport proteins are placed on the cell surface membrane eg. GLUT4
- More glucose can therefore enter the cell
- Enzymes are activated that convert glucose in the cell to glycogen (glycogenesis)
- More glucose used in respiration
What happens when there is a decrease in blood glucose?
α cells within the Islets of Langerhans in the pancreas detect this and release the hormone glucagon. The β islet cells of the pancreas stop releasing insulin.
Glucagon raises blood glucose concentration by binding to receptors on the plasma membrane of the target cells (eg. liver cells - hepatocytes).
- This causes stored glycogen to be hydrolysed into glucose (glycogenolysis).
- The glucose diffuses out of the target cells into the blood.
- Target cells also take up less glucose and the rate of respiration of glucose decreases (lipids or amino acids are being used instead in respiration).
- Glucagon also activates enzymes that are involved in the formation of glucose from non-carbohydrates, eg. Glycerol, amino acids, fatty acids. This is called gluconeogenesis.
How does GLUT4 work in lowering blood glucose?
GLUT4 is stored in vesicles in the cell cytoplasm. When insulin binds to receptors on the plasma membrane however, it causes the movement of GLUT4 to the membrane.
Glucose can then be transported into the cell through the GLUT4 protein by facilitated diffusion.
How does adrenaline work in increasing blood glucose?
secreted from the adrenal glands
Adrenaline binds to receptors in the plasma membrane of liver cells
• Activates glycogenolysis
• Inhibits glycogenesis
- activates glucagon secretion and inhibits insulin secretion.
What is secondary messengers work?
Both adrenaline and glucagon activate glycogenolysis inside a cell, even though they bind outside of the cell
activate an enzyme on the inside of the plasma membrane - which then causes a chemical to be produced - known as a second messenger.
The second messenger activated by adrenaline and glucagon is called cyclic AMP (cAMP).
How do secondary messengers work?
• Adrenaline or glucagon binds to their
complementary shaped receptor proteins in their
plasma membrane of target cells
• Binding activates the enzyme adenylate cyclase
which converts ATP to cyclic AMP (cAMP) – the
second messenger inside the cell.
• cAMP activates a protein called protein kinase A.
• This starts a cascade of enzyme actions within the
cell that causes glycogen to be broken down into
glucose (glycogenolysis)
What is diabetes mellitus type 1?
Autoimmune disease in which the β cells of the pancreas are attacked by the immune system therefore they can’t produce insulin
After eating, blood glucose remains high, kidneys can’t reabsorb all the glucose so some of it is excreted in the urine.
Regular monitoring of blood glucose concentration together with regular injections of insulin are required
