Why do advanced multicellular organisms need a transportation mechanism?

In advanced multicellular organisms, the sites of absorption and synthesis are specific and separated by greater distances, making diffusion alone insufficient for transport.

Which processes facilitate the movement of materials into individual cells?

The movement of materials into individual cells is facilitated by diffusion, osmosis, or active transport.

Why does blood not clot inside a blood vessel?

In the blood plasma, the basophil cells (type of WBC) secrete heparin, which is an anticlotting chemical. Heparin prevents the blood from clotting within the blood vessels.

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question 1 of 1

What is the primary role of Platelets (Thrombocytes) in the human blood circulatory system?

1.They help cluster together to plug leaks and form blood clots at points of injury.

2.They transport digested food, carbon dioxide, and nitrogenous wastes in a dissolved form.

3.They fight against diseases and infections to protect the body.

4.They transport oxygen from the lungs to all tissues of the body.

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Transportation in Humans

Master the Circulatory System in Minutes: Discover how the human body transports nutrients, oxygen, carbon dioxide, and metabolic wastes efficiently across long cellular distances. Learn about the components of blood, how a blood clot forms, and the critical differences between arteries, veins, and capillaries without complex formatting blocks.

Class: 10 Science (CBSE)
Chapter: Life Processes
Estimated Learning Time: 15–20 Minutes

1.0Learning Outcomes

After completing this lesson, you will be able to:

Explain why complex multicellular organisms require a dedicated transport system.
Detail the composition of blood (plasma vs. cellular elements) and list its primary functions.
Describe the stepwise biochemical sequence behind blood clotting.
Contrast the structural and functional traits of arteries, veins, and capillaries.
Solve fundamental board-level and textbook questions accurately.

Transportation in Biology Introduction

In unicellular organisms, a single cell carries out all the life processes as the cell itself is an organism. In advanced forms like the few-celled algae, protozoa, sponges, etc., the size of the organism ensures that all the cells are not very far from each other. The uptake of materials from the environment is through the general body surface and the transport within the cells is by diffusion. However, more advanced multicellular forms need a transportation mechanism. The sites of absorption and synthesis are very specific and are separated by a greater distance from the other parts of the body.

The actual movement of materials into the individual cells is by diffusion, osmosis or active transport.

2.0Transportation in Human

The process of transporting the absorbed food, gases, water, waste products etc., from one place to another in the body is called circulation.

In human beings, the circulatory (transport) system is divided into two systems :

Blood Circulatory System

(a) Blood

(b) Blood vessels

(c) Heart

Lymphatic System

(a) Lymph

(b) Lymph vessels

(c) Lymph nodes

(d) Lymphatic organs

3.0Blood Circulatory System

The circulatory system is the main transportation system of the human body.

The body has about 5 liters of blood continuously travelling through it by the way of the circulatory system.

Blood

Blood is an important fluid connective tissue which transports the materials to different body

parts.

Composition of Blood

Blood is thicker and slightly heavier than water. Its pH ranges from 7.35 to 7.45 (slightly alkaline). It consists of two parts, each with its own job in the body.

(i) Plasma

(ii) Cellular components

Plasma

Plasma is a liquid portion of blood. It transports food, CO₂ and nitrogenous wastes in dissolved form. It contains water (90-92%), protein (7% - albumin, globulin, fibrinogen), others (1% - hormones, wastes, gases, salts, ions).

Red Blood Cells (Erythrocytes)

It transports oxygen from lungs to all tissues of the body and returns CO₂ back to the lungs.

In humans, RBCs are circular, biconcave and enucleated. The red colour of RBC is due to the presence of haemoglobin.

White Blood Cells (Leukocytes)

It protects us against diseases & infections. WBCs are of two main types on the basis of presence or absence of granules in cytoplasm. It shows ameoboid movement. It can change its shape.

Platelets/Thrombocytes

Small plate shaped cells that cluster together to help in forming blood clots when bleeding occurs.

Functions of Blood

Transportation of oxygen from lungs to tissues.
Transportation of carbon dioxide from the tissues to the lungs.
Transportation of excretory materials from the tissues to the kidneys.
Transportation of digested food from the small intestine to the tissues.
Distribution of hormones and enzymes.
Formation of clots to prevent blood loss.
Distribution of heat and temperature control. Prevention from infections and helps in wound healing.

Blood clotting or Coagulation

When we are injured and start bleeding, the loss of blood from the system has to be minimized. In addition, leakage would lead to a loss of pressure which would reduce the efficiency of the pumping system. To avoid this, the blood has platelets which circulate around the body and plug these leaks by helping to clot the blood at these points of injury.

Blood Clot

Injured tissue + blood platelets releases thrombokinase.

$P ro t h ro mbin thrombokinase C a^{++} T h ro mbin$

$F ib r in o g e n Thrombin f ib r in$

Fibrin + Dead RBC, WBC and Platelets → Blood clot

Prothrombin and fibrinogen are plasma protein synthesized in liver and are present in plasma.

Serum is a watery fluid expelled from a contracting blood clot.

Serum = plasma – Clotting factors.

Blood Vessels

In human, three types of blood vessels are present.

(i) Arteries

These vessels carry blood from heart to various organs of the body. The walls of the arteries are thick and elastic.

(ii) Veins

They collect the blood from different parts of the body and pour it into the heart. The walls of veins are thin and less elastic. They do not need thick walls because the blood is no longer under pressure instead they have valves that ensure that the blood flows only in one direction.

(iii) Capillaries

These are smallest blood vessels and one-cell thick. The walls of capillaries are very thin. Exchange of materials between the blood and tissue cells take place at capillaries. Capillaries lack muscular wall and is lined by simple squamous epithelium (endothelium).

The major differences between various blood vessels have been given in table.

Comparative Study of Blood Vessels
S.No.	Features	Arteries	Veins	Capillaries
1.	Blood flow	Blood flows rapidly with jerks.	Blood flows smoothly without jerks.	Blood flows smoothly without jerks.
2.	Lumen	Narrow	Wide	Very small
3.	Valves	Absent	Present	Absent
4.	Location	Mostly deep seated	Mostly superficial	Form a network all over the body and the organs.
5.	Direction of blood flow	Take the blood away from heart to different parts of body.	Bring the blood towards the heart from various body parts.	Blood flows from arterioles to capillaries and then to venules.
6.	Kind of blood	Oxygenated blood except in pulmonary artery.	Deoxygenated blood except in pulmonary vein.	Blood changes from oxygenated to deoxygenated.
7.	Blood pressure	Pressure is high.	Pressure is low.	Pressure is extremely low.

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5.0Supporting Study Materials

This study material CBSE Notes and NCERT Solutions for the Chapter "Life Processes" on Transportation Topics is designed according to the latest CBSE Class 10 Science syllabus and NCERT guidelines. It provides clear explanations of key concepts, definitions, examples, and important questions to help students understand redox reactions, corrosion, and rancidity, and prepare effectively for examinations.

CBSE Class 10 Science Notes Chapter 5 Life Processes	NCERT Solution Class 10 Science Chapter 5: Life Process

6.0PREVIOUS YEAR QUESTIONS (PYQs)

Q1. Why are the walls of arteries thick and elastic, whereas veins have thin walls and contain valves? (CBSE Board)

Answer

Arteries receive blood directly from the heart immediately after a contraction. Because the heart pumps blood with significant force, the blood inside arteries moves rapidly under very high pressure. To withstand this high pressure without bursting, arteries require thick, elastic walls.
Veins collect blood from various body tissues where the fluid pressure is already very low. Since the pressure is low, thick walls are unnecessary. However, because the blood moves slowly and often against gravity, veins contain internal valves to prevent the blood from flowing backward, ensuring it travels only toward the heart.

Q2. What is the composition of blood plasma, and what are its primary transport responsibilities? (CBSE Board)

Answer

Composition: Blood plasma is a pale, straw-colored liquid component of blood that accounts for roughly 55% of its total volume. It contains 90-92% water, about 7% structural proteins (like fibrinogen and albumin), and 1% dissolved salts, nutrients, and hormones.
Transport Responsibilities: Plasma is responsible for carrying digested food molecules (like glucose and amino acids) from the small intestine, carbon dioxide gas from working tissues, and nitrogenous metabolic waste compounds (like urea) from cells to the excretory organs in a completely dissolved state.

7.030-Second Revision

Plasma = Transports food, CO₂, and urea in dissolved form.
RBCs = Lack a nucleus; carry oxygen via haemoglobin.
Platelets = Form a fibrin mesh to build a blood clot and stop bleeding.
Arteries = Thick, elastic walls; high pressure; lack valves; carry blood away from the heart.
Veins = Thin walls; low pressure; contain valves to stop backflow; carry blood back to the heart.
Capillaries = One-cell thick; specialized exclusively for nutrient and gas exchange.

8.0Recommended Next Topics

The Human Heart and Double Circulation Pathway
Lymphatic System (Composition and Functions of Lymph)
Transportation in Plants (Xylem vs. Phloem Mechanism)
Respiration: Aerobic vs. Anaerobic Metabolism