BIOL 2420 Lecture Notes - Lecture 3: Red Blood Cell, Oxygen Saturation, Horse Length
26 Apr 2018
School
Department
Course
Professor
Unit 6 – Lecture 3
Oxygen Binding Obeys the Law of Mass Action
- Hemoglobin binding reaction obeys the law of mass action
o concentration of free O2 increases = more oxygen binds to hemoglobin = the equation
shifts to the right producing more HbO2
o concentration of free O2 decreases = less oxygen binds to hemoglobin = equation shifts
to the left (amount of oxyhemoglobin decreases)
- in the blood
o free oxygen available to bind to hemoglobin is dissolved oxygen (PO2 of plasma)
o in pulmonary capillaries, oxygen from the alveoli first dissolves in plasma
▪ dissolved O2 then diffuses into the red blood cells where it can bind to
hemoglobin
▪ hemoglobin acts like a sponge, it soaks up oxygen from the plasma until the
reaction reaches equilibrium
- transfer of oxygen from alveolar air to plasma to red blood cells and ending on hemoglobin
o occurs rapidly
o blood in the pulmonary capillaries normally picks up as much oxygen as the PO2 of the
plasma and the number of red blood cells allow
- once arterial blood reaches the tissues
o exchange process that occurred in the lungs reverses
o dissolved oxygen diffuses out of systemic capillaries into cells (which have lower PO2)
▪ decrease in PO2 disturbs the equilibrium of the oxygen-hemoglobin binding
reaction by removing O2 from the left side of the equation
• equilibrium shifts to the left according to the law of mass action
o causes hemoglobin molecules to release their oxygen stores
- tasfeig oge to the od’s ells takes plae e apidl ad goes to euiliiu
o PO2 of cells determines how much oxygen is unloaded from hemoglobin
o As cells increase their metabolic activity, their PO2 decreases and hemoglobin releases
more oxygen to them
Hemoglobin Transports Most Oxygen to the Tissues
- There must be adequate amounts of hemoglobin in our blood or we cannot survive
o Eaple: a peso’s total oge osuptio at est is aout 250L O2/min and
cardiac output is 5L blood/min. How much oxygen must blood contain to meet this
demand?
250mL O2/min consumed = 5L blood/min x ? mLO2/L blood
▪ To eet ell’s eeds fo oge, 5 L of lood/i oig to the tissues ould
need to contain at least 50 mL O2/L blood
- Low solubility of oxygen in plasma means that only 3 mL of O2 can dissolve in the plasma
fraction of each liter of arterial blood
o Dissolved oxygen delivered to the cells in plasma therefore is:
3 mL O2/L blood x 5 L blood/min = 15 mL O2/min
- Cells require at least 250 mL O2/min
o The small amount of oxygen that dissolves in plasma cannot meet the needs of the
tissues at rest
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Oxygen binding obeys the law of mass action. There must be adequate amounts of hemoglobin in our blood or we cannot survive: e(cid:454)a(cid:373)ple: a pe(cid:396)so(cid:374)"s total o(cid:454)(cid:455)ge(cid:374) (cid:272)o(cid:374)su(cid:373)ptio(cid:374) at (cid:396)est is a(cid:271)out 250(cid:373)l o2/min and cardiac output is 5l blood/min. 250ml o2/min consumed = 5l blood/min x ? mlo2/l blood: to (cid:373)eet (cid:272)ell"s (cid:374)eeds fo(cid:396) o(cid:454)(cid:455)ge(cid:374), 5 l of (cid:271)lood/(cid:373)i(cid:374) (cid:272)o(cid:373)i(cid:374)g to the tissues (cid:449)ould need to contain at least 50 ml o2/l blood. Low solubility of oxygen in plasma means that only 3 ml of o2 can dissolve in the plasma fraction of each liter of arterial blood: dissolved oxygen delivered to the cells in plasma therefore is: 3 ml o2/l blood x 5 l blood/min = 15 ml o2/min. Cells require at least 250 ml o2/min: the small amount of oxygen that dissolves in plasma cannot meet the needs of the tissues at rest.
