plasma proteins

Main functions of plasma proteins

Maintain blood viscosity, limit capillary permeability, transport substances, and serve as amino acid sources.

Plasma protein contributing most to blood viscosity

Fibrinogen.

Effect of plasma proteins on capillary permeability

They close capillary pores, limiting permeability and preventing water loss.

Role of albumin, α and β globulins

Act as carriers for hormones, vitamins, and lipids.

How plasma proteins conserve substances

By binding them to prevent rapid loss in urine and provide a reservoir.

Plasma proteins during starvation

Act as a source of amino acids for tissue protein replacement.

Determinants of blood viscosity

RBCs and plasma proteins.

Viscosity of blood compared to water

Blood is 3× and plasma is 1.5× as viscous as water.

Viscosity in polycythemia

Increases due to more RBCs.

Viscosity in anemia

Decreases due to fewer RBCs.

Importance of viscosity

Helps maintain arterial blood pressure.

Are RBCs true cells?

No, they lack nuclei.

Shape of RBCs

Circular, biconcave, non-nucleated discs.

RBC count in males and females

5.4 million/mm³ in males, 4.8 million/mm³ in females.

High RBC count in infants, athletes, and high altitudes

Due to increased oxygen demand and hypoxia.

Low RBC count in children and elderly

Reduced bone marrow activity and oxygen demand.

Structure of adult hemoglobin (HbA)

2 alpha and 2 beta chains.

Structure of fetal hemoglobin (HbF)

2 alpha and 2 gamma chains.

Why HbF has higher oxygen affinity

To extract oxygen from maternal blood.

When HbF is replaced by HbA

By 4 months after birth.

Normal hemoglobin content

15–16 g/dL in males, 13–14 g/dL in females, 19 g/dL in newborns.

Hematocrit value (PCV)

RBC volume ÷ total blood volume × 100; normally 46% in males, 42% in females.

What is oxyhemoglobin?

Hb loosely bound to oxygen (Fe²⁺ remains unchanged).

What is carbaminohemoglobin?

Hb bound to carbon dioxide.

What is carboxyhemoglobin?

Hb bound to carbon monoxide (cherry red color).

What is methemoglobin?

Hb with Fe³⁺, cannot carry oxygen (dark color).

Enzyme reducing methemoglobin back to Hb

NADH-met-Hb reductase.

Hereditary methemoglobinemia

Congenital deficiency of NADH-met-Hb reductase causing excess met-Hb.

Blood color in methemoglobinemia

Chocolate brown with cyanosis.

Blood color in CO poisoning

Cherry red without cyanosis.