what is the right article of an
Answers
Answer:
Here is a summary of the basic rules: Use the definite article the with specific nouns. Use the indefinite article a or an with non-specific nouns. Use a before words that begin with a consonant or vowel that sounds like a consonant.
Carbon dioxide is produced by cell metabolism
in the mitochondria. The amount produced
depends on the rate of metabolism and the relative amounts of carbohydrate, fat and protein
metabolized.The amountis about 200mlmin1
when at rest and eating a mixed diet; this utilises
80% of the oxygen consumed, giving a respiratory quotient of 0.8 (respiratory quotient ¼
rate of carbon dioxide production divided by
rate of oxygen consumption). A carbohydrate
diet gives a quotient of 1 and a fat diet 0.7.
Carbon dioxide transport in
the blood
Carbon dioxide is transported in the blood
from the tissue to the lungs in three ways:1
(i) dissolved in solution; (ii) buffered with
water as carbonic acid; (iii) bound to proteins,
particularly haemoglobin.
Approximately 75% of carbon dioxide is
transport in the red blood cell and 25% in the
plasma. The relatively small amount in plasma
is attributable to a lack of carbonic anhydrase
in plasma so association with water is slow;
plasma plays little role in buffering and combination with plasma proteins is poor.
There is a difference between the percentage
of the total carbon dioxide carried in each
form and the percentage exhaled from them.
For example, 5% of the total is in solution but
10% of exhaled carbon dioxide comes from this
source; 10% is protein bound, particularly with
haemoglobin, but this supplies 30% of the
exhaled amount.
Dissolved carbon dioxide
Carbon dioxide is 20 times more soluble than
oxygen; it obeys Henry’s law, which states that
the number of molecules in solution is proportional to the partial pressure at the liquid
surface. The carbon dioxide solubility coefficient is 0.0308 mmol litre–1 mm Hg–1 or
0.231 mmol litre–1 kPa–1 at 37C. (Solubility
increases as the temperature falls.) This corresponds to 0.5 ml kPa–1 carbon dioxide in 100 ml
blood at 37C. The partial pressure of carbon
dioxide is 5.3 pKa in arterial blood and 6.1 kPa
in mixed venous blood; therefore, arterial
blood will contain about 2.5 ml per 100 ml
of dissolved carbon dioxide and venous
blood 3 ml per 100 ml. A cardiac output of
Carbonic acid
Carbon dioxide combines with water to form
carbonic acid, a reaction accelerated by carbonic anhydrase. The carbonic acid then freely
dissociates (Equation 1).
CO2 þ H2O Ð
carbonic anhydrase
H2CO3
Ð Hþ þ HCO
3 ð1Þ
The enzyme carbonic anhydrase is present
in a number of organs of the body including
the eye, kidney and brain; however, for this
purpose, it is the red blood cell carbonic anhydrase that is important. Once carbonic acid is
formed it dissociates easily so that the ratio of
Carbon dioxide and water diffuse freely
into the red blood cell and are converted to
carbonic acid, which dissociates into hydrogen
and bicarbonate ions. Hydrogen ions do not
pass through cell membranes but carbon
dioxide passes readily. This situation cannot
be sustained as the intracellular hydrogen ion
and bicarbonate ion concentration, osmolarity
and cell size will rise and rupture the cell. Thebicarbonate ion diffuses out to the plasma to be exchanged for
chloride ions. This is known as the chloride shift (Gibbs–Donnan
equilibrium or Hamburger effect). An ion exchange transporter
protein in the cell membrane called Band 3 for Cl–
HCO3
– facilitates
chloride shift.
A build up of hydrogen ion in the red blood cell would also
prevent further conversion and production of bicarbonate ion.
However, hydrogen ions bind easily to reduced haemoglobin,
which is made available when oxygen is released; therefore, free
hydrogen ions are removed from solution. Reduced haemoglobin
is less acidic than oxygenated haemoglobin. This is another way
of stating the Haldane effect, which explains that, at any given
PCO2, the carbon dioxide content of deoxygenated blood is
greater than that of oxygenated blood.
As a result of the shift of chloride ions into the red cell and the
buffering of hydrogen ions onto reduced haemoglobin, the intercellular osmolarity increases slightly and water enters causing
the cell to swell. This can be measured as an increase in mean
corpuscular volume (MCV). The reverse process occurs as the
red blood cell passes through the lung.
Bound to haemoglobin and other proteins
Carbon dioxide combines rapidly to the terminal uncharged
amino groups (R-NH2) to form carbamino compounds.
.........................plz mark my answer as brainlist