Unit 3 Flashcards Preview

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Flashcards in Unit 3 Deck (21)
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1
Q

Explain why a vein may be described as an organ (1)

A

Made up of different tissues

2
Q

Explain the importance of maintaining a constant blood pH (3)

A
  • Proteins like haemoglobin are affected by changes in pH
  • The tertiary structure would be different
  • Less oxygen would bind with the haemoglobin
3
Q

Explain how co-transport takes place when cells lining the ileum absorb glucose (3)

A
  • 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+
4
Q

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)

A
  • 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
5
Q

Explain two ways in which the structure of fish gills is adapted for efficient gas exchange (2)

A
  • Many lamellae = large S.A.

- Thin surface = short D.P.

6
Q

In humans, substances move out of the capillaries to form tissue fluid. Describe how this tissue fluid is returned to the circulatory system (3)

A
  • hydrostatic pressure is lower in capillaries
  • water returns
  • by osmosis
7
Q

Explain how oxygen is loaded, transported and unloaded in the blood (6)

A
  • 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.
8
Q

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)

A
  • Higher affinity for oxygen

- So oxygen moves from the mother to the fetus

9
Q

A fish uses its gills to absorb oxygen from water. Explain how the gills of a fish are adapted for efficient gas exchange (6)

A
  • 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)
10
Q

Explain how oxygen in a red blood cell is made available for respiration in active tissues (3)

A
  • low pH due to increased co2 due to increased respiration
  • means haemoglobin has increased dissociation
  • oxygen diffuses from r.b.c to tissues
11
Q

Describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs (4)

A
  • Air enters the trachea which splits into the bronchi and bronchioles
  • down pressure gradient
  • down diffusion gradient
  • across alveolar epithelium
  • across capillary epithelium
12
Q

The hydrostatic pressure falls from the arteriole end of the capillary to the venule end of the capillary. Explain why (1)

A
  • loss of water
13
Q

High blood pressure leads to an accumulation of tissue fluid. Explain how (1)

A
  • High blood pressure = high hydrostatic pressure
  • Reduces inward pressure at venule end of capillary
  • so more tissue fluid is formed
14
Q

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)

A
  • There are introns which are non-coding

- Stop/start sequences

15
Q

The haemoglobin in one organism may have a different chemical structure from the haemoglobin in another organism. Describe how (1)

A

different primary structure

16
Q

The oxygen dissociation curve for haemoglobin shifts to the right during vigorous exercise. Explain the advantage of this shift (3)

A
  • lowers affinity for oxygen
  • releases o2 more readily to cells
  • for rapid respiration
17
Q

What is meant by the term ‘partial pressure’? (1)

A

A measure of the concentration of a gas

18
Q

Explain the advantage of the difference in position of the dissociation curve during exercise (2)

A
  • haemoglobin has a lower affinity for oxygen (right shift)

- so more o2 is available for respiration

19
Q

Describe the structure of proteins (5)

A
  • Proteins are polymers of amino acids
  • formed by condensation
  • joined by peptide bonds
  • primary structure is sequence of bases
  • tertiary structure is folding of polypeptide chain due to H-bonding
20
Q

Describe how proteins are digested in the human gut (4)

A
  • Hydrolysis of peptide bonds
  • Endopeptidases break polypeptides into smaller peptide chains
  • Exopeptidases remove terminal amino acids
  • Dipeptidases hydrolyse depeptides into amino acids
21
Q

Describe how mRNA is produced in the nucleus of a cell (6)

A
  • Helicase breaks H-bonds
  • only one DNA strand acts as a template
  • RNA nucleotides attracted to exposed complementary base
  • RNA polymerase joins RNA nucleotides together
  • pre-mRNA spliced to remove introns