Organisms exchange of substances with the environment Flashcards
The mean FEV1 value of non-smokers decreases after the age of 30.
Use your knowledge of ventilation to suggest why.
Internal intercostal muscles become less effective.
Elasticity of lung tissue decreases.
The scientists’ hypothesis was that adding the inhibitor of amylase to the food would lead to a lower blood glucose concentration.
Use your knowledge of digestion to suggest how the addition of the inhibitor could lead to a lower blood glucose concentration.
Fewer E-S complexes formed between starch and amylase. With inhibitor less starch is digested to maltose per second, therefore less glucose monomers are formed from maltose; resulting in there being a decrease in absorption of glucose.
Explain how the shape of an enzyme molecule is related to its function.
It has a specific 3D tertiary structure that determines the shape of its active site. This active site is shaped in a way that is complementary only to its substrate.
Bacteria produce enzymes which cause food to decay. Explain how vinegar, which is acidic, can prevent the action of bacterial enzymes in some preserved foods.
The low pH of vinegar (since it is acidic) results in the deforming of the specific tertiary structure of the enzymes as it disrupts its ionic bonds & disulphide bridges. This alters the shape of the enzymes active site so its no longer complementary to its substrate and cannot form E-S complexes.
Suggest and explain why the combined actions of endopeptidases and exopeptidases are more efficient than exopeptidases on their own.
Exopepidases only break off the terminal amino acid. Using an Endopeptidase, amino acid chains will be broken into smaller chains as internal peptide bonds are broken. This increases the surface area for exopeptidases to work on.
The addition of a respiratory inhibitor stops the absorption of amino acids. Explain why.
A respiratory substrate will reduce ATP production. This means there will be no sodium ions pumped out of the epithelial cells through active transport into the ileum. Therefore there will be no sodium ion concentration gradient for sodium ions to move into the cell with amino acids.
Species of tubifex worm that live in ponds, lakes and rivers cannot survive in seawater.
Use your knowledge of water potential to explain why they cannot survive in seawater.
The water potential in the sea water is lower than in the worm so water will leave the worm by osmosis and therefore metabolic reactions cease.
One of the severe disabilities that results from emphysema is that walking upstairs becomes difficult.
Explain how a low FEV1 value could cause this disability.
There will be less CO2 removed and less oxygen taken up and so there will be more anaerobic respiration. This increases lactic acid production so muscles start to ache.
Some people produce a much higher ventricular blood pressure than normal. This can cause tissue fluid to build up outside the blood capillaries of these people.
Explain why.
A higher pressure means more tissue fluid is formed at the arteriole end of the capillary. The high pressure also means less will return in the venular end. There will be too much excess fluid for the lymphatic system to drain.
Some drugs used to reduce high ventricular blood pressure cause widening of blood vessels.
Suggest how widening of blood vessels can reduce ventricular blood pressure.
A larger lumen will reduce blood pressure in the blood vessels and there is less friction.
Describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs. Details of breathing are not required.
Oxygen enters and moves down the trachea and bronchi until it gets to the alveoli down its pressure gradient. It then moves down its diffusion gradient across the alveolar epithelium through the capillary endothelium.
One theory of translocation states that organic substances are pushed from a high pressure in the leaves to a lower pressure in the roots.
Describe how a high pressure is produced in the leaves.
When sugars are actively transported into the phloem, the water potential in the phloem falls. Water moves in from neighbouring xylem vessels through osmosis. This increaseed volume of water increases the hydrostatic pressure in the leaves.
Explain how an asthma attack causes a drop in FEV
Muscle walls of the bronchioles contract and the walls secrete more mucous. This reduces the diameter of the airways and so airflow is reduced.
Describe and explain the mechanism that causes forced expiration.
Internal intercostal muscles contract. The diaphragm relaxes and the ribs move upwards and outwards, reducing the volume of the thorax and thus increasing the pressure until it exceeds atmospheric pressure. This forces air out of the lungs down its pressure gradient.
The water potential of the blood plasma is more negative at the venule end of the capillary than at the arteriole end of the capillary. Explain why.
Because at the venule end water has left the capillaries but proteins were too large to leave. This increases the concentration of blood proteins.
