Question

When temperature decreases, oxy-Hb curve becomes (a) more steep (b) straight (c) parabola (d) none of these.

Short answer

When temperature decreases, the oxy-Hb curve becomes (a) more steep.

Step-by-step solution

Understanding the Oxyhemoglobin Dissociation Curve

The oxyhemoglobin (oxy-Hb) dissociation curve describes how hemoglobin's affinity for oxygen changes with varying blood oxygen levels. A shift to the left in the curve at lower temperatures indicates an increased affinity for oxygen, because hemoglobin holds onto oxygen more tightly.

Analyzing the Effect of Temperature

As the temperature decreases, the curve shifts to the left, becoming steeper at the plateau phase (the middle range of partial pressures of oxygen where hemoglobin saturation is high), but it does not turn into a straight line or a parabola.

Selecting the Correct Option

The correct option that describes the curve becoming steeper at the plateau phase as the temperature decreases is (a) more steep. This is because the affinity of hemoglobin for oxygen increases at lower temperatures.

Key concepts

Hemoglobin's affinity for oxygen

Hemoglobin is a protein in red blood cells that is critically involved in transporting oxygen from the lungs to the rest of the body, and then carrying carbon dioxide back from the body's tissues to the lungs to be exhaled. Its affinity for oxygen is the degree to which the protein binds to oxygen molecules.

The oxyhemoglobin dissociation curve is a graphical representation that shows the relationship between the saturation of hemoglobin with oxygen (y-axis) and the partial pressure of oxygen (x-axis) in the blood. When hemoglobin's affinity for oxygen is high, it will bind oxygen more readily, and the curve will shift to the left. This means that at a given partial pressure of oxygen, hemoglobin will be more saturated with oxygen, thereby enhancing oxygen delivery to the tissues that require it.

Physiologically, this mechanism is essential for adapting to changing oxygen demands. For instance, during exercise, tissues demand more oxygen, triggering a rightward shift in the curve to facilitate oxygen release. Conversely, when the demand is lower, such as in a resting state, the leftward shift helps retain oxygen within the hemoglobin.

Effect of temperature on oxy-Hb curve

Temperature is one of several factors that can cause the oxyhemoglobin dissociation curve to shift. In a clinical or physiological context, this shift is important as it affects hemoglobin's ability to pick up and release oxygen.

As temperature decreases, the hemoglobin molecule undergoes a conformational change that increases its affinity for oxygen. This results in a leftward shift of the oxy-Hb dissociation curve and makes the curve steeper at its plateau phase. This steeper slope at lower temperatures is indicative of hemoglobin's increased affinity for oxygen, meaning it's more tightly bound to oxygen molecules and less likely to release them into tissues.

Subjects like hypothermia, where the body's core temperature drops significantly, demonstrate this concept well. During hypothermia, tissue oxygen demand is reduced, and so enhanced oxygen affinity helps maintain tissue oxygenation even with lowered metabolic rates.

Blood oxygen levels

The measurement of blood oxygen levels, often referred to as oxygen saturation, is an indicator of how much oxygen the blood is carrying as a percentage of the maximum it could carry. It is a crucial parameter in assessing respiratory and circulatory efficiency and is typically measured using a pulse oximeter or blood gas analysis.

An optimal oxygen saturation level is usually between 95% and 100%. When saturation levels drop below this range, a condition known as hypoxemia can occur, leading to symptoms like breathlessness, headaches, and confusion. Persistent low oxygen levels may lead to hypoxia, which is detrimental to body tissues and organs and can result in severe health consequences.

Understanding the factors that influence the oxyhemoglobin dissociation curve, such as temperature and hemoglobin's affinity for oxygen, is vital. These factors directly impact how efficiently oxygen is delivered throughout the body and can inform medical decisions, such as oxygen supplementation in patients with compromised lung function.