Database results:
examBoard: Pearson Edexcel
examType: IGCSE
lessonTitle: Plasma Transport Functions
Blood is often called the 'river of life' because it flows through our bodies carrying essential substances to every cell. Blood plasma is the often-overlooked hero of this transport system. It's the liquid part of blood that makes up about 55% of total blood volume and serves as the medium in which blood cells and various substances are carried throughout the body.
Key Definitions:
Blood plasma is approximately 90% water and 10% dissolved substances including:
Plasma has several important physical properties that enable its transport functions:
Plasma serves as the body's transport medium, carrying various substances to where they're needed and removing waste products. Let's explore these vital transport functions in detail.
After digestion, nutrients enter the bloodstream and are transported by plasma to cells throughout the body. This ensures that every cell receives the fuel and building blocks it needs to function properly.
Glucose is the primary energy source for cells. Plasma transports glucose from the digestive system or liver to all body cells. Blood glucose levels are carefully regulated by hormones like insulin and glucagon.
Fats and cholesterol are insoluble in water, so they're transported in plasma bound to proteins as lipoproteins (like HDL and LDL). These provide energy, insulation and materials for cell membranes.
Amino acids from digested proteins are transported in plasma to cells where they're used to build new proteins for growth, repair and enzyme production.
While most oxygen (98%) is carried by haemoglobin in red blood cells, plasma still plays a role in gas transport, particularly for carbon dioxide.
About 2% of oxygen is dissolved directly in plasma. While this is a small percentage, it's still important, especially when oxygen levels are low. Plasma also carries the red blood cells that transport the majority of oxygen.
Plasma transports carbon dioxide in three ways:
Hormones are chemical messengers produced by endocrine glands. Plasma transports these hormones from their site of production to their target cells throughout the body.
Hormones like insulin, glucagon and adrenaline dissolve directly in plasma. They typically act quickly but have a short lifespan in the bloodstream.
Steroid hormones like oestrogen, testosterone and cortisol are transported bound to plasma proteins. This binding protects them from rapid breakdown and extends their lifespan in the blood.
Plasma plays a crucial role in removing metabolic waste products from tissues and transporting them to excretory organs for elimination from the body.
Produced in the liver from the breakdown of excess amino acids. Plasma transports urea to the kidneys where it's filtered out and excreted in urine.
A waste product from the breakdown of nucleic acids. Transported in plasma to the kidneys for excretion. Excess uric acid can form crystals that cause gout.
A waste product from muscle metabolism. Levels in plasma are used as an indicator of kidney function, as healthy kidneys efficiently remove creatinine from blood.
Plasma proteins are produced mainly by the liver and play crucial roles in transport and other bodily functions. There are three main types:
The most abundant plasma proteins. They maintain osmotic pressure, preventing fluid leakage from blood vessels. Albumins also transport fatty acids, hormones and some drugs through the bloodstream.
Include antibodies (immunoglobulins) that fight infection, alpha and beta globulins that transport metals and lipids and gamma globulins involved in immune response. They're crucial for defending against disease.
Essential for blood clotting. When bleeding occurs, fibrinogen is converted to fibrin, which forms a mesh to trap platelets and blood cells, creating a clot that stops bleeding.
Sarah, a 19-year-old student, regularly donates plasma at her local blood centre. Unlike whole blood donation, plasma donation involves removing blood, separating the plasma and returning the blood cells to the donor. This process, called plasmapheresis, allows donors to give plasma more frequently than whole blood.
Sarah's donated plasma might be used to help patients with immune deficiencies, bleeding disorders, or severe burns. It could also be processed to extract specific proteins for medications. Plasma donation is particularly valuable because plasma can be frozen for up to one year, creating a stable supply for medical emergencies.
The COVID-19 pandemic highlighted another use for plasma: convalescent plasma therapy. People who recovered from COVID-19 had antibodies in their plasma that could help others fight the infection. This demonstrates how understanding plasma transport functions has real-world medical applications.
Beyond transport, plasma plays crucial roles in homeostasis maintaining stable conditions in the body.
Plasma proteins, especially albumin, create osmotic pressure that helps maintain the correct distribution of water between blood and tissues. This prevents oedema (swelling from excess fluid in tissues) and helps maintain blood volume and pressure.
When plasma protein levels are too low (as in malnutrition or liver disease), water leaks from blood vessels into tissues, causing swelling.
Plasma contains buffer systems that resist changes in pH, keeping blood slightly alkaline (pH 7.35-7.45). The main buffer is the bicarbonate system:
CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-
If blood becomes too acidic, bicarbonate ions neutralize excess hydrogen ions. If blood becomes too alkaline, carbonic acid provides hydrogen ions to restore balance.
Understanding plasma transport functions has important medical applications:
If all the blood vessels in your body were laid end to end, they would stretch about 100,000 kilometres enough to circle the Earth more than twice! This vast network allows plasma to reach every cell in your body, delivering nutrients and removing wastes.
Plasma can appear yellow-green under certain lighting conditions due to the presence of bilirubin, a breakdown product of haemoglobin.
During pregnancy, blood plasma volume increases by up to 50% to support the growing baby, while red blood cell production increases by only about 20-30%. This is why pregnant women sometimes develop physiological anaemia.
Log in to track your progress and mark lessons as complete!
Login NowDon't have an account? Sign up here.