6.4.1/2 Flashcards
(22 cards)
What is homeostasis?
The maintenance of a constant internal environment
Why could an increase in temperature be a problem?
H-bonds in the tertiary structure of proteins (including enzymes) might break
So the tertiary structure changes and the protein can no longer carry out its function
Why could a decrease in temperature be a problem?
A decrease in temperature means particles might not have enough kinetic energy for reactions to occur so the rates of reaction are too slow
Why could a deviation in blood pH be a problem?
The H-bonding and ionic bonding in proteins will change
This could cause a change in the tertiary structure and thus function of proteins e.g. enzymes
Why could an increase in blood glucose levels be a problem in terms of water potential of the blood?
• Increase in blood glucose decreases water potential of blood more water leaves the cells and moves into the blood cells dehydrate and shrivel
Why could a decrease in blood glucose levels be a problem in terms of energy transfer and water potential of the blood?
- Decrease in blood glucose lack of glucose available for cells less respiration in cells
- Decrease in blood glucose increases water potential of blood more water absorbed into cells than they need (could lead to cells bursting)
What is negative feedback?
Where a change triggers a response which reduces the effect of a change.
What is positive feedback?
Where a change triggers a response which increases the effect of a change
When talking about an example of positive feedback what should you always include in your answer?
More X, therefore more Y, therefore more X
Make sure that you close the loop, e.g. in the case above there is more X and as a result there is more Y and this causes more X (so you end where you started)
Why are there separate mechanisms involving negative feedback to control departures in different directions from the original state?
This allows a greater degree of control
What can cause blood glucose concentration to increase?
Eating and drinking carbohydrate rich foods
What can cause blood glucose concentration to decrease?
Exercising
What is glycogenesis? And where does it take place?
Conversion of glucose glycogen
What is glycogenolysis? And where does it take place?
Conversion of glycogen to glucose. It takes place in the liver (and a bit in muscles)
What is gluconeogenesis? Where does it take place? What causes it to take place?
Glucagon binds to receptors
This causes enzymes to be activated so that amino acids and fatty acids and glycerol are converted into glucose.
It takes place in the liver.
Write a flow-chart to describe what happens when blood glucose concentration is too high
- Detected by beta cells in the islets of langerhan in the pancreas
- The beta cells release insulin
- Insulin travels in the blood
- Insulin binds to receptors on target cells (muscle cells, liver cells, adipose cells)
- More glucose transporter proteins become embedded in the cell membrane and open
- More glucose is absorbed into the cells
- Insulin activates enzymes which convert glucose to glycogen
Write a flow-chart to describe what happens when blood glucose concentrations is too low
- Detected by alpha cells in the islets of langerhan in the pancreas
- The alpha cells release glucagon
- Glucagon travels in the blood
- Glucagon binds to receptors on target cells in the liver and muscles
- adenylate cyclase is activated and converts ATP to cAMP
- cAMP activates protein kinase
- protein kinase activates other enzymes which converts glycogen to glucose and/or amino acids & fats to glucose
Describe the effect of adrenalin on glycogen break down
- Adrenalin travels in the blood
- Adrenalin binds to receptors on target cells in the liver and muscles
- adenylate cyclase is activated and converts ATP to cAMP
- cAMP activates protein kinase
- protein kinase activates other enzymes which converts glycogen to glucose
What’s the difference between the effects of glucagon and adrenalin?
Adrenalin causes glycogenolysis
Glucagon can cause glycogenolysis and gluconeogenesis
Glucagon and adrenaline both work by the secondary messenger model.
What is the primary messenger?
Glucagon and adrenaline
What is the secondary messenger in both cases?
Cyclic AMP
Describe how you could use a dilution series of glucose solutions and a colorimeter to find the concentration of glucose in an unknown ‘urine’ sample
- Make at least 5 solutions of glucose of known concentrations
- Put 2cm3 of each glucose solution into a labelled test tube
- Add 2cm3 of Benedict’s solution to each of the 5 test tubes and heat them
- Allow the precipitate to settle overnight (or use cotton wool to push down the precipitate which has formed)
- Use a pipette to remove the solution from the top of the test tube and transfer it to a cuvette
- ensure that the colorimeter is set to a red light filter
- ‘calibrate’ the colorimeter using a cuvette containing distilled water
- put each glucose solution into the colorimeter and measure the absorbance of light
- plot a graph with glucose concentration on the x-axis and absorbance of light by the solution of the y-axis
- this is a calibration curve
- mix 2cm3 of the urine with 2cm3 of Benedict’s solution and heat
- Allow the precipitate to settle overnight (or use cotton wool to push down the precipitate which has formed)
- use a pipette to transfer a sample of the solution into a cuvette
- measure the absorbance of light by the solution
- find the absorbance value on the y-axis of the graph and draw a line across until it hits the calibration curve
- draw a line down until you reach the x-axis. This tells you the concentration of glucose in the unknown sample
