Life Process Part-II

Life Process Part-II Class 10th Science

Topics in the Chapter

• Respiration in Human Beings
→ Breakdown of Glucose by Various Pathways
→ Types of Respiration
→ Human Respiratory System
→ Mechanism of Breathing
• Respiration in plants
• Transportation in Human Beings
→ Circulatory system in human beings
• Blood circulation in human body
→ Direction of blood flow through human heart
• Blood
→ Lymph
→ Types of Blood Vessels
→ Exchange of gases between alveoli, blood and tissues
• Transportation in Plants
→ Transpiration and its Functions
• Excretion System in Human Beings
→ Excretory wastes
→ Three steps of Urine formation
→ Formation of Urine in Human Beings
→ Functions of Nephron
→ Artificial Kidney
• Excretion in Plants

Respiration in Human Beings

→ Respiration involves:

(i) Gaseous exchange (Breathing) : Intake of oxygen from the atmosphere and release of CO2.

(ii) Cellular respiration: Breakdown of simple food in order to release energy inside the cell.

• Breakdown of Glucose by Various Pathways

→ The first step is the break-down of glucose (a six-carbon molecule) into a three-carbon molecule called pyruvate which takes place in the cytoplasm.

→ The pyruvate may be converted into ethanol and carbon dioxide which takes place in yeast during fermentation. Since this process takes place in the absence of air (oxygen), it is called anaerobic respiration.

→ The pyruvate is broken down into three-carbon pyruvate molecule in the presence of oxygen to give three molecules of carbon dioxide and water. This process takes place in mitochondria. Since this process takes place in the presence of air (oxygen), it is called aerobic respiration.

→ The pyruvate is converted into lactic acid when there is a lack of oxygen in our muscle cells, which is also a three-carbon molecule. This build-up of lactic acid in our muscles during sudden activity causes cramps.

The whole process of break down of glucose is shown below:

→ The energy released during cellular respiration is immediately used to synthesise a molecule called ATP which is used to fuel all other activities in the cell. In these processes, ATP is broken down giving rise to a fixed amount of energy which can drive the endothermic reactions taking place in the cell.

→ The rate of breathing in aquatic organisms is much faster than that seen in terrestrial organisms  because the amount of dissolved oxygen is fairly low compared to the amount of oxygen in the air.

• Types of Respiration

Aerobic Respiration                                                                 Anaerobic Respiration

Takes place in the presence of oxygen.                               Takes place in the absence of oxygen.

Occurs in mitochondria.                                                       Occurs in cytoplasm.

End products are CO2 and H2O.                                          End products are alcohol or lactic acid.

More amount of energy is released.                                     Less amount of energy is released.

• Human Respiratory System

Passage of air through the respiratory system:

→ Nostril: Air is taken into the body.

→ Nasal Passage: It is a channel for airflow through the nose.

→ Nasal Cavity:  It is lined with hairs and mucus membrane. It warms, moisturize, and filter air before it reaches the lungs.

→ Pharynx: It contains rings of cartilage which ensure that the air-passage does not collapse.

→ Larynx: It houses the vocal cords and manipulates pitch and volume, which is essential for phonation. It is also known as voice box.

→ Trachea: Pharynx splits into trachea and esophagus. It connects the larynx (or voice box) to the bronchi of the lungs. It provides air flow to and from the lungs for respiration.

→ Bronchi: They are the main passageway into the lungs. They are the extensions of the windpipe that shuttle air to and from the lungs. The oxygen goes to the lungs and carbon dioxide leave the lungs through them.

→ Bronchioles: Bronchi get smaller when they reaches closer to lungs tissues and are called Bronchioles. They are the passageways by which air passes through the nose or mouth to the alveoli of the lungs

→ Alveoli: They are smaller tubes which finally terminate in balloon-like structures which are called alveoli. They allow oxygen and carbon dioxide to move between the lungs and bloodstream.

→ Blood capillaries: They are the sites of the transfer of oxygen and other nutrients from the bloodstream to other tissues in the body. They also collect carbon dioxide and waste materials and return it to the veins.

• Mechanism of Breathing

Inhalation                                                                                                                  Exhalation

During inhalation the thoracic cavity (chest cavity) expands.                          Thoracic cavity contracts.

Ribs lift up.                                                                                                       Ribs move downwards.

Diaphragm become flat in shape.                                                                    Diaphragm becomes dome shaped.

Volume of lungs increases and air enters the lungs.                                       Volume of lungs decreases and air exits from the lungs.

• Exchange of gases between alveoli, blood and tissues

(i) Air (rich in O2) reaches blood which combines with haemoglobin in RBC and O2 is released in
alveoli tissues (through blood vessels).

(ii) CO2 is released in blood  and dissolved into it and carried by blood vessels. The carbon dioxide is released in alveolar sac which is sent out through nostrils.

→ Terrestial organisms: Use atmospheric oxygen for respiration.

→ Aquatic organisms: Use dissolved oxygen for respiration.

Respiration in plants

Respiration in plants is simpler than the respiration in animals. Gaseous exchange occur through :
(a) Stomata in leaves
(b) Lenticels in stems
(c) General surface of the root

Transportation in Human Beings

Human beings like other multicellular organism need regular supply of food, oxygen etc. This function is performed by circulatory system.

→ The circulatory system in human beings consists of:
(i) Heart (pumping organ)
(ii) Arteries and Veins (Blood vessels)
(iii) Blood and lymph (Circulatory medium)

• Circulatory system in human beings

→ The lungs supply oxygen-rich blood to the the left atrium of the heart.

→ The left atrium relaxes when it is collecting the blood and contracts when blood is transferred to the left ventricle. The left ventricle expands when it receives blood.

→ The blood is pumped out of the body when the muscles of left ventricle contracts.

→ De-oxygenated blood comes from the body to the upper chamber on the right i.e. the right atrium when it expands.

→ The corresponding lower chamber i.e. the right ventricle expands when right atrium contracts. It transfers the blood to the right ventricle which in turn pumps it to the lungs for oxygenation.

→ Right ventricles have thicker muscular walls so that they pump blood into various organs.

→  Valves ensure that blood does not flow backwards when the atria or ventricles contract.

Blood circulation in human body

→ Double circulation: Blood travels twice through the heart in one complete cycle of the body.

Direction of blood flow through human heart

→ Pulmonary Circulation: Blood moves from the heart to the lungs and back to the heart.

→ Systemic Circulation: Blood moves from the heart to rest of the body and back to the heart.

• Blood

Blood is connective tissue which is fluid in nature.

→ Solid components of blood (Blood corpuscles):

(i) RBC (Red blood cells): It carries O2 and CO2 and also contain Haemoglobin which impart red colour to the blood.

(ii) WBC (White blood cells): It provides body defence by engulfing the germs and produces antibodies.

(iii) Blood Platelets: It helps in blood clotting during injury.

→ Liquid components (Plasma): It is a yellow colour fluid which contain 90% water & 10% organic
substances.

• Lymph

→ It is a yellowish fluid which escapes from the blood capillaries into the intercellular spaces.

→ It contains less proteins than blood.

→ It flows from the tissues to the heart which helps in transportation and destroying germs.

→ It carries digested and absorbed fat from intestine and drains excess fluid from extra cellular space back into the blood.

• Types of Blood Vessels

There are two types of blood vessels
(i) Arteries
(ii) Veins

Arteries                                                                                                                                        Veins

Carry oxygenated blood from heart to                                                                        Carry deoxygenated blood from body parts to 

body parts except pulmonary artery.                                                                           heart except pulmonary vein.        

Also called distributing vessel.                                                                                    Also called collecting vessel.

Thick and elastic.                                                                                                        Thin and less elastic.

Deepseated. (far from the skin)                                                                                  Superficial (near to the skin) as compared to arteries.

Transportation in Plants

There are two main conducting pathways in a plant.
(i) Xylem
(ii) Phloem

Xylem                                                                                                                 Phloem

Carries water & minerals from the roots                                              Carries product of photosynthesis from leaves

to other parts of the plant.                                                                    to the other parts of the plant.

No energy is used.                                                                               Energy is used from ATP.

Transpiration and its Functions

It is the process of loss of water as vapour from aerial parts of the plant.

Function :
(a) Absorption and upward movement of water and minerals by creating PULL.
(b) Helps in temperature regulation in plant.

Transport of food from leaves (food factory) to different part of the plant is called Translocation.

Excretion System in Human Beings

Excretory/urinary system consists of :
(1) The kidneys : The excretory organ
(2) The ureters : The ducts which drain out urine from the kidneys
(3) The urinary bladder : The urinary reservoir
(4) The urethra : The channel to the exterior

Excretion

(i) The metabolic activities in the body generates many kinds of wastes including nitrogenous wastes which are harmful for the body and hence needed to be removed. Excretion is a process by which these wastes are removed from our body.

(i) Unicellular organisms remove these wastes by simple diffusion.

Excretory wastes

Functions of Organs involved in Excretory System

Each kidney contains many filtration units called as nephrons.

→ Nephrons are made up of a cluster of thin walled capillaries called glomerulus which is associated with a cup like structure called as Bowman’s capsule and the long tube which terminates through this
capsule.

→ The renal artery brings oxygenated blood to the kidneys along with the nitrogenous wastes like urea and uric acid and many other substances.

→ The blood gets filtered through the glomerulus and this filtrate enters the tubular part of nephron.

→ As this filtrate moves down the tubular part, glucose, amino acids, salts and excess of water gets selectively reabsorbed by the blood vessels surrounding these tubules.

→ The amount of water reabsorbed depends upon :
(i) How much excess of water is there in the body and,
(ii) How much nitrogenous wastes need to be excreted out.

→ So the fluid now flowing in the tubular part is urine which gets collected in collecting ducts of nephrons.

→ These collecting ducts together leave the kidney at a common point by forming the ureter.

→ Each ureter drains the urine in the urinary bladder where it is stored until the pressure of expanded bladder leads to an urge to pass it out through urethra.

→ This bladder is a muscular structure which is under nervous control.

→ 180 litres of filtrate is formed daily but only 2 litres is excreted out as urine so the rest is reabsorbed in the body.

Structure of Nephron

Functions of Nephron

→ Excretion of nitrogenous wastes.
→ To maintain the water and ionic balance (osmic regulation).

Artificial Kidney

Haemodialysis: The process of purifying blood by an artificial kidney. It is meant for kidney failure patients.

Excretion in Plants

Plants use different strategies for excretion of different products :

→ Oxygen and carbon dioxide is diffused through stomata.

→ Excess water is removed by transpiration.

→ Plants can even loose some of their old parts like old leaves and bark of tree.

→ Other waste products like raisins and gums especially in old xylem cells which can also be lost by plants.

→ Plants also secrete some waste substances into the soil around them.

Formation of urine in Humans

The urine formation involves three steps :

(i) Glomerular filtration: Nitrogenous wastes, glucose water, amino acid filter from the blood into Bowman Capsule of the nephron.

(ii) Tubular reabsorption: Now, useful substances from the filtrate are reabsorbed back by capillaries surrounding the nephron.

(iii) Secretion: Urea, extra water and salts are secreted into the tubule which open up into the collecting duct & then into the ureter.