The partial pressures of O2 and CO2 in the bloood vary at different points in the circulatory system. Blood arriving at the lungs via the pulmonary arteries has a lower __ and a higher __ than the air in thealveoli. As blood enters the alveolar capillaries, Co2 diffuses from the blood to the air in the alveoli. Meanwhile, O2 in the air dissolves in the fluid that coats the alveolar epitheliuum and diffuses into the blood. By the time the blood leaves the lungs in the pulmonary veins, its __ has been raised and its __ has been lowered. After returning to the heart, this blood is pumped through the systemic circuit.
PO2PCo2PO2PCO2
In the tissue capillaries, gradients of partial pressure favor the diffusion of __ out of the blood and __ into the blood. These gradients exist because cell resp in the mito of cels near each capillary removes O2 from and adds Co2 to the surrounding interstitial fluid. After the blood unloads O2 and loads CO2, it is returned to the heart and pumped tot he lungs again.
O2
CO2
True or False:
The low solubility of O2 in water (and thus in bood) poses a problem for animals that rely on the circulatory system to deliver O2.
true
In fact, animals tansport most of their O2 bound to certain proteins called __, which circulate with teh blood or __ and are often contained within specialized cells. They greatly icnreasee the amt of O2 that can be carried in the circulatory fluid.
respiratory
hemolymp
A variety of respiratory pigments have evolved among the animal taxa. With a few exceptions, these molecules have a distinctive color and consist of a protein bound to a metal.
Ex: blue pigment __ (copper as its oxygen binding component)
- Vertebrates and some invertebrates is __.= in the erythrocytes.
hemocyanin
hemoglobin
Like all resp pigments, __ binds O2 reversibly, loading O2 in the lungs or gills and unlaoding it in other parts of the body. This process depends on __ between teh hemoglobin subunits.
hemoglobin
cooperativity
The production of CO2 during cell resp promotes the unloadiing of O2 by __ in active tisssues.
- CO2 reacts with water, forming __ which lowers the pH of its surrouundings. Low pH decreasees the affinity of hemoglobin for O2, called the __. Thus, where CO2 production is greater, hemoglobin releases mroe O2, which can then be used to support more cell resp.
hemoglobiin
carbonic acid
Bohr shift
In addition to its role in O2 transport, __ helps transport CO2 and assists in buffering the blood- that is, preventing harmful changes in pH. Only about __% of the Co2 relesed by respiring cells is transported in solution in blood plasma. Another __% binds to the amino ends of the hemoglobin polypeptide chainsa dn about __% is transported in the blood in the form of bicarbonate ions (HCO3-)
hemoglobin
5
23
70
Carbon dioxide from respiring cells diffuses into the blood plasma and then into erythrocytes. THere the Co2 reacts with water (assisted by the enzyme __) and forms H2CO3, which dissociates into H+ and HCO3-. Most of the H+ binds to hemoglobin and other proteins, minimizing the change in blood pH. The HCO3- diffuses into teh plasma.
carbonic anhydrase
TRUE OR FALSE:
When blood flws through the lungs, the relative partial pressures of CO2 favors the diffusion of Co2 out tof the blood. As CO2 diffuses into the alveoli, the amt of CO2 in the blood decreases. This decrease shifts the chemical equilibrium in favor of the conversion of HCO3- to CO2, enabling further net diffusion of CO2 into alveoli.
