Unit 3 Flashcards
Explain why a vein may be described as an organ (1)
Made up of different tissues
Explain the importance of maintaining a constant blood pH (3)
- Proteins like haemoglobin are affected by changes in pH
- The tertiary structure would be different
- Less oxygen would bind with the haemoglobin
Explain how co-transport takes place when cells lining the ileum absorb glucose (3)
- Na+ actively transported from ileum cells to blood
- Maintains diffusion gradient for Na+ to enter cells from gut
- Glucose enters by facilitated diffusion with Na+
Explain how the counter-current mechanism in fish gills ensures the maximum amount of the oxygen passes into the blood flowing through the gills (3)
- water and blood flow in opposite directions
- blood always passes water which has a higher 02 conc.
- Concentration gradient is maintained across the whole gill
Explain two ways in which the structure of fish gills is adapted for efficient gas exchange (2)
- Many lamellae = large S.A.
- Thin surface = short D.P.
In humans, substances move out of the capillaries to form tissue fluid. Describe how this tissue fluid is returned to the circulatory system (3)
- hydrostatic pressure is lower in capillaries
- water returns
- by osmosis
Explain how oxygen is loaded, transported and unloaded in the blood (6)
- Haemoglobin carries oxygen
- loads oxygen in lungs
- at high partial pressures of o2
- unloads to respiring cells
- at low partial pressures of 02
- unloading is linked to higher c02 conc.
The oxygen dissociation curve of the fetus is to the left of that for its mother. Explain the advantage of this for the fetus (2)
- Higher affinity for oxygen
- So oxygen moves from the mother to the fetus
A fish uses its gills to absorb oxygen from water. Explain how the gills of a fish are adapted for efficient gas exchange (6)
- Large S.A. due to the lamellae
- thin epithelium = short distance between water and blood
- water and blood flow in opposite directions
- maintains C.G. along gill
- circulation replaces blood saturated with oxygen
- ventilation replaces water (o2 is removed)
Explain how oxygen in a red blood cell is made available for respiration in active tissues (3)
- low pH due to increased co2 due to increased respiration
- means haemoglobin has increased dissociation
- oxygen diffuses from r.b.c to tissues
Describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs (4)
- Air enters the trachea which splits into the bronchi and bronchioles
- down pressure gradient
- down diffusion gradient
- across alveolar epithelium
- across capillary epithelium
The hydrostatic pressure falls from the arteriole end of the capillary to the venule end of the capillary. Explain why (1)
- loss of water
High blood pressure leads to an accumulation of tissue fluid. Explain how (1)
- High blood pressure = high hydrostatic pressure
- Reduces inward pressure at venule end of capillary
- so more tissue fluid is formed
The total number of bases in the DNA of the a-polypeptide gene is more than 423. Give two reasons why there are more than 423 bases (2)
- There are introns which are non-coding
- Stop/start sequences
The haemoglobin in one organism may have a different chemical structure from the haemoglobin in another organism. Describe how (1)
different primary structure
