Transportation

Simple definition of a transport system in biology: A transport system is a means by which materials are moved (‘transported’) from an exchange surface or exchange surfaces to cells located throughout the organism.

In cellular biology, membrane transport refers to the collection of mechanisms that regulate the passage of solutes such as ions and small molecules through biological membranes, which are lipid bilayers that contain proteins embedded in them.

Supplement

In biology, transport refers to the act or the means by which a molecule or ion is moved across the cell membrane or via the bloodstream. There are two types of transport in this regard: (1) passive transport and (2) active transport. Passive transport is a kind of transport by which ions or molecules move along a concentration gradient, which means movement from an area of higher concentration to an area of lower concentration. Examples of passive transport include diffusion, filtration, and osmosis. Active transport is a kind of transport wherein ions or molecules move against a concentration gradient, which means movement in the direction opposite that of diffusion – or –movement from an area of lower concentration to an area of higher concentration. This type of transport requires expenditure of energy and the assistance of proteins (i.e. carrier protein).

Transportation in Animals

In case of unicellular and small multicellular organisms transport takes place by diffusion. However, in large multicellular organisms, as the distances between different body parts have increased, they need an elaborate and efficient system for transportation of materials. In large animals, such a system is called circulatory system in which a fluid circulates in all parts of the body. In many invertebrates this fluid is the haemolymph, where as in all vertebrates and in some higher invertebrates this fluid is the blood.

The circulatory system in animals is of two main types (A) open circulatory system and (B) closed circulatory system.

Open Circulatory System

Many invertebrates e.g. arthropods have open circulatory system. In this system the blood is pumped from the heart into the blood vessel. The blood vessels in turn, empty themselves into open spaces called sinuses. In the sinuses, the blood is in direct contact with the tissues, and after exchange of materials with the tissues it re-enters the heart for circulation again.

Closed Circulatory System

Closed circulatory system is more elaborate, complicated and efficient as compared to the open circulatory system. The closed circulatory system consists of a muscular, and contractile pumping organ, the heart with its incoming (veins) and outgoing (arteries) blood vessels. The blood remains confined in the blood vessels while circulating in the whole body e.g. earthworm, man etc.

Transportation in Plants

Plants have specialized vascular tissues for transportation of substances. There are two types of vascular tissues in plants, viz. xylem and phloem.

Xylem: Xylem is responsible for transportation of water and minerals. It is composed of tracheids, xylem vessels, xylem parenchyma and xylem fibre. Tracheids and xylem vessels are the conducting elements. The xylem makes a continuous tube in plants which runs from roots to stem and right up to the veins of leaves.

Phloem: Phloem is responsible for transportation of food. Phloem is composed of sieve tubes, companion cells, phloem parenchyma and bast fibres. Sieve tubes are the conducting elements in phloem.

Ascent of Sap:

The upward movement of water and minerals from roots to different plant parts is called ascent of sap. Many factors are at play in ascent of sap and it takes place in many steps. They are explained as follows:

Root Pressure:- The walls of cells of root hairs are very thin. Water; from soil; enters the root hairs because of osmosis. Root pressure is responsible for movement of water up to the base of the stem.

Capillary Action:- A very fine tube is called capillary. Water; or any liquid; rises in the capillary because of physical forces and this phenomenon is called capillary action. Water; in stem; rises up to some height because of capillary action.

Adhesion- cohesion of Water Molecules: Water molecules make a continuous column in the xylem because of forces of adhesion and cohesion among the molecules.

Transpiration Pull: Loss of water vapour through stomata and lenticels; in plants; is called transpiration. Transpiration through stomata creates vacuum which creates a suction; called transpiration pull. The transpiration pull sucks the water column from the xylem tubes and thus water is able to rise to great heights in even the tallest plants.

Transport of Food:-
Transport of food in plants happens because of utilization of energy. Thus, unlike the transport through xylem; it is a form of active transport. Moreover, the flow of substances through phloem takes place in both directions, i.e. it is a two-way traffic in phloem.

Transportation in Human beings

In human beings, the various organs associated with this system include the heart, lungs, blood vessels, capillaries, and blood. The heart is the pumping organ that squirts out blood. The heart does this with so much pressure that it is capable of squirting blood up to 9 meters high. It never stops and beats continuously so that blood can travel to all parts of the body.

Your blood travels through these blood vessels transporting oxygen, carbon dioxide, digested food, hormones and even waste products.It is amazing to see how transportation in human beings is carried out by the circulatory system, with the heart and the vast network of blood vessels.

Blood

Blood is an important fluid connective tissue. It is mainly composed of plasma and blood cells. There are three types of blood cells, namely, red blood cells, white blood cells, and blood platelets. The RBCs have haemoglobin, an iron-containing complex protein. The WBCs are the cells that help in fighting diseases and attack any foreign bodies in the blood. The blood platelets are the ones that help in clotting of blood.

In human beings, there is a phenomenon called double circulation that occurs, which is an efficient way. The heart pumps the blood, and through the various blood vessels, it travels to different organs and then comes back again to the heart. Now, this flow of blood in humans occurs in two pathways called the pulmonary pathway and the systemic pathway.

This system ensures that the deoxygenated blood (blood carrying carbon dioxide) from the right side of the heart goes to the lungs, where gaseous exchange occurs. Blood gets filled with oxygen from the lungs and carbon dioxide is given out to the lungs(from where it leaves the body). The oxygenated blood then travels from the left side of the heart to all other parts of the body.

The double circulation seen here ensures that there is no mixing of oxygenated blood and deoxygenated blood. There is also an efficient supply of oxygen to the body cells and a greater rate of blood flow in the body.

Heart

How do the oxygenated blood and the deoxygenated blood not get mixed? Firstly, they travel in different blood vessels. Secondly, in the heart, there are four chambers. The blood without oxygen and the blood with oxygen flow into different chambers.

The human heart is a muscular organ, which has four chambers. The two upper chambers called the right atrium and the left atrium, and the two lower chambers called the right ventricle and left ventricle. The right atrium and the right ventricle together may be called the right heart. The left atrium with the left ventricle together can be called as the left heart. All the chambers of the heart are separated by muscular walls called septum.

Blood Vessels

Arteries and veins are the main blood vessels. These are interconnected by a network of smaller vessels called capillaries. Veins carry deoxygenated blood to the right side of the heart whereas arteries carry oxygenated blood away from the heart to different parts of the body.

Lymphatic system

In human beings and vertebrates, the lymphatic system acts as a subsystem of the circulatory system. It also has a role to play in the transportation in human beings. Lymph is a special fluid called the tissue fluid. It plays a role in the exchange process of nutrients and gases that occurs through blood. Any excess fluid remaining in the cells and tissues is collected by the lymph and is drained into the veins, which carry blood.