18.2 Composition of Blood Plasma

plasma component: water

92% of plasma - solvent in which formed elements are suspended and proteins and solutes are dissolved

plasma component: plasma proteins (~7% of plasma)

albumin (~58% of plasma proteins)

• exerts osmotic pressure to retain fluid within blood

• blood viscosity

• transport selected molecules (ions, lipids, hormones)

globulin (~37% of plasma proteins)

• alpha-globulin transport lipids and metal ions

• beta-globulins transport lipid and iron ions

• gamma-globulins are antibodies that immobilize pathogens

fibrinogen (~4% of plasma proteins)

• participates in blood coagulation (clotting)

regulatory proteins (<1% of plasma membrane)

• consists of enzymes and hormones

plasma component: other solutes (~1% of blood plasma)

electrolytes (sodium, potassium, calcium, chloride, iron, bicarbonate, hydrogen)

• helps establish, maintain, and change membrane potentials, pH balance, and regulate osmosis

nutrients

• energy source, metabolic processes

respiratory gases

• oxygen needed for aerobic cellular respiration

• carbon dioxide waste product produced by cells during this process

wastes

• transported to liver and kidneys where they can be removed from blood

common electrolytes in arterial plasma: cations

sodium

• fxn: neuron and muscle fxn, fluid balance, cotransporter

• regulated by: aldosterone, glucocorticoids

potassium

• fxn: neuron and muscle fxn

• regulated by: aldosterone, ANP

calcium

• fxn: hardens bone, release of neurotransmitter, muscle contraction

• regulated by: PTH, calcitriol, calcitonin

hydrogen

• fxn: pH balance

• regulated by: buffering systems, kidney, respiratory system

common electrolytes in arterial plasma: anions

chloride

• fxn: anion bound to sodium, component of gastric acid (HCL)

• regulated by: sodium

bicarbonate

• fxn: pH balance

• regulated by: CO2 and H+ levels

phosphate

• fxn: binds with Ca and deposited in bone

• regulated by: PTH

common molecules found in blood plasma

glucose

• range: 70-100 mg/dL

• fxn: fuel molecule for cellular respiration, regulated by hormones such as insulin and glucagon

amino acids

• range: varies based on specific amino acid

• fxn: monomers for synthesizing protein

lactate:

• fxn: by-product of glycolysis

lipids: generally do not dissolve in water

• cholesterol

  • range: 100-200 mg/dL

• HDL

• VLDL/LDL

• triglycerides

  • range: 30-149 mg/dL

  • fxn: fuel molecules

• phospholipids

plasma

composed of water (92%), plasma proteins (7%), dissolved molecules and ions (1%)

• extracellular fluid (ECF)

• similar composition to interstitial fluid, but plasma has higher protein concentration

blood is a colloid, why?

plasma contains dispersed proteins

• albumins, globulins, fibrinogen, and other clotting proteins, enzymes, and some hormones

• most produced in liver

colloid osmotic pressure (COP)

prevents loss of fluid from blood as it moves thru capillaries

• exerted by plasma proteins

• helps maintain blood volume and blood pressure

can be decreased by diseases, resulting in fluid loss from blood and tissue swelling

• ex. liver diseases that decrease production of plasma proteins

• ex. kidney diseases that increase elimination of plasma proteins

plasma proteins: albumin

Smallest and most abundant group of plasma proteins (58%)

• Exert greatest colloid osmotic pressure

• Act as transport proteins for some lipids, hormones, and ions

plasma proteins: globulins

Second largest group of plasma proteins (37%)

• Smaller alpha-globulins and larger beta-globulins

• Transport some water-insoluble molecules, hormones, metals, ions

plasma proteins: gamma-globulins

part of body’s defenses

plasma proteins: fibrinogen

Makes up only 4% of plasma proteins

• Contributes to blood clot formation

  • Following trauma, it is converted to insoluble fibrin strands

• Serum is plasma with clotting proteins removed

plasma proteins: regulatory proteins

Less than 1% of total proteins

• Includes enzymes (catalyze reactions), proenzymes (inactive precursors of enzymes), and hormones

blood is a solution, why?

Contains dissolved organic and inorganic molecules and ions

• electrolytes, nutrients, gases, waste products

• Polar or charged substances dissolve easily

• Nonpolar molecules require carrier proteins