CBSE CLASS 10 CHAPTER 6 NOTES

 CHAPTER 6

LIFE PROCESSES

WHAT ARE LIFE PROCESSES?

·         Even when the organism is sitting, sleeping or not doing anything the maintenance function goes on.

·         Processes those which do this maintenance jobs are called Life Processes.

·         All life processes require energy which is provided by the food we eat à Nutritional Processes.

·         Food is broken down with the help of oxygen to give energy à Respiration

·         Food and O₂ though taken at one place have to be carried to all parts à Transportation System.

·         During metabolic activities in our body many by products are created of which some may be toxic and are removed à Excretion.

OSMOSIS

·         The movement of water from higher concentration to lower concentration through a semi permeable membrane.

DIFFUSION

·         The movement of gases from higher concentration to lower concentration.

NUTRITION

·         The source of energy is the food we eat.

·         Living things

o   (i) Autotrophic

§  Prepare their own food.

§  Example: Green plants & some bacteria

o   (ii) Heterotrophic

§  Depends directly or indirectly on plants.

§  Example: Animals & fungi

AUTOTROPHIC NUTRITION

·         Seen in plants.

·         Photosynthesis

 

 

·         Excess glucose is stored in the form of Starch (in Plants).

·         In case of humans à excess glucose is stored as glycogen.

PHOTOSYNTHESIS

Steps involved:

1.    Absorption of light energy by the chlorophyll.

2.    Conversion of light energy into chemical energy.

3.    Splitting of H₂O into Hydrogen &Oxygen.

4.    Reduction of CO₂ into carbohydrates.

 

PHOTOSYNTHESIS IN DESERT PLANTS

·         In desert plants – they take CO₂ at night and prepare an intermediate which is acted upon by the light energy absorbed by the chlorophyll during the day.

·         

·         Stomata controlled by the guard cells open to obtain CO₂ for photosynthesis and closes once CO₂ is taken in.

·         In desert plants, CO₂ is taken during night, because if the stomata are open during day, there may be intense water loss due to transpiration.

·         Plants require other materials like nitrogen, phosphorus, iron & magnesium which is taken from soil.

·         Atmospheric N₂ is converted into nitrates & nitrites by denitrifying bacteria (Rhizobium), which is then taken by plants.

·         Nitrogen is very essential for plants for the synthesis of proteins & other components.

HETEROTROPHIC NUTRITION

·         Animals which directly or indirectly depend on plants for their food are said to exhibit heterotrophic nutrition.

·         HOLOZOIC NUTRITION

o   Organisms that takes in whole food and breaks down inside the body.

o   Example: Amoeba

·         SAPROPHYTIC NUTRITION

o   Organisms feed on dead and decaying matter.

o   Example: Fungi like yeast, bread moulds& mushroom.

·         PARASITIC NUTRITION

o   Organisms which are dependent on other plants or animals completely where the host is not benefitted.

o   Example: Cuscuta, ticks, lice, etc.,

NUTRITION IN AMOEBA

·         In Amoeba the food may be taken in by the entire surface.

·         Amoeba puts forward its finger like extension (Pseudopodia) around the food it encounters and enclose it within the food vacuole.

·         Inside the food vacuole food is digested and the digested food is diffused into cytoplasm.

·         The waste is thrown out through the cell surface at any point.

 

NUTRITION IN PARAMECIUM

·         The cilia present in the Paramecium helps them to move towards the food.

·         Unlike Amoeba, Paramecium has a specific spot at which food is taken in.

·         It also has a specific spot through which wastes are thrown out.

NUTRITION IN HUMAN BEINGS

·         Alimentary canal – long tube extending from the mouth to anus.

·         The tube has different parts at different regions, specialised to perform different function.

·         The food that is taken in is crushed with our teeth.

·         Saliva secreted by salivary gland is mixed with the food.

 

·         Saliva contains an enzyme called salivary amylase that breaks down starch into sugar.

·         This food is moved into the food pipe (oesophagus) by a peristaltic movement (contraction & relaxation of the muscles).

·         Food is then moved to the stomach, which is a large muscular bag which expands when the food is sent into it.

·         Stomach has gastric glands which secretes

o   Hydrochloric acid (Hcl) – creates an acidic medium and kills germs in food. It also activates the enzyme pepsin.

o   Pepsin – digests proteins in acidic medium.

o   Mucus – protects the inner lining of the stomach from the action of acid.

·         The exit of food from stomach to the small intestine is slow and is controlled by the sphincter muscle. 

·         Small intestine – longest part of the alimentary canal, which is extensively coiled and compactly kept.

·         Complete digestion of carbohydrates, proteins and fats takes place in small intestine.

·         Herbivores have longer intestine for digestion of cellulose. As they feed on plants and plants contain cellulose.

·         Carnivores have short intestine as meat is easily digestible.

·         The food which comes from the stomach is acidic; it is turned alkaline by bile juices secreted by liver. 

·         Bile salts from liver acts on fat globules & breaks them down into smaller globules.

·         The smaller globules can be easily acted upon by the enzymes.

·         Pancreatic juices contains enzymes like

o   Trypsin – digests protein

o   Lipase – digests lipids or fats

·         Walls of small intestine have glands that secretes intestinal juices.

·         Enzymes in intestinal juices digests

o   Carbohydrates à glucose

o   Proteins àamino acids

o   Fats à fatty acids & glycerol

·         The digested food is absorbed in the small intestine by villi

·         The villi are finger like projections to increase the surface area for absorption of digested food.

 

 

·         Villi are richly supplied with blood vessels which takes the absorbed food to each and every cell in the body.

·         This food is then converted into energy by the process of cellular respiration.

·         The unabsorbed food is sent into large intestine, where more villi are present and it absorbs water.

·         The rest of the waste material is removed via the anus which is controlled by the anal sphincter.

 

RESPIRATION

·         The food material taken in during the process of nutrition is used in cells to provide energy for all the life processes.

·         Some organisms use oxygen to break down glucose – Aerobic respiration.

·         Some organisms don’t involve oxygen for breaking down glucose – Anaerobic respiration.

ANAEROBIC RESPIRATION (ABSENCE OF OXYGEN)

·         FIRST STEP: Breaks down glucose (6C molecule) into pyruvate (3C molecule)

·         This process takes place in cytoplasm.

·         SECOND STEP: Pyruvate is converted into Ethanol and CO₂ & energy is released.

·         This process takes place in yeast during fermentation.

AEROBIC RESPIRATION (PRESENCE OF OXYGEN)

·         FIRST STEP: Break down of glucose (6C) to pyruvate (3C).

·         This process takes place in Mitochondria.

·         SECOND STEP: Pyruvate is converted into 3 molecules of CO₂, water and energy.

·         The release of energy in aerobic respiration is a lot greater than anaerobic respiration.

·         Example: Cellular respiration in human beings.

 

IN MUSCLE CELL (LACK OF OXYGEN) ALTERNATE PATHWAY

·         FIRST STEP: Glucose (6C) à pyruvate (3C) + Energy

·         SECOND STEP: Pyruvate à Lactic acid (3C) + Energy

·         Lactic acid accumulates in our muscles and may cause sudden cramps.

 

·         The energy released during cellular respiration is converted into ATP (used as fuel for cellular activities)

·         ATP is the energy currency for most of the cellular processes.

·         Energy released during cellular respiration makes as ATP from ADP and one inorganic phosphate

·         ADP + P à ADP-P = ATP

·         ADP àAdenosine Di Phosphate

·         P àInorganic Phosphate

·         ATP àAdenosine Tri Phosphate

·         ATP is used by many endothermic processes to drive the reaction.

·         The terminal phosphate linkage in ATP id broken using water to give 30.5 KJ/mol of energy.

·         This energy is used for the various life processes in our body.

IN PLANTS

·         Exchange of gases takes place through stomata.

·         CO₂ and I are exchanged by diffusion.

·         At night, when there is no photosynthesis occurring, CO₂ is eliminated.

·         During the day, CO₂ is used up for photosynthesis. Thus there is no CO₂ release – instead O₂ is released.

IN ANIMALS

·         Respiration (inhaling of O₂ and exhaling of CO₂) takes place differently in different organisms.

·         Terrestrial animals – can breathe in O₂ from the atmosphere.

·         Aquatic animals – uses the O₂ dissolved in water.

·         Example: Fishes – they takes in water through their mouth and forces it to pass through the gills. Where the dissolved O₂ is taken up by the blood.

·         The rate of breathing in aquatic animals is faster than terrestrial animals as the amount of O₂ dissolved in water is less compared to that in the atmosphere.

IN HUMAN BEINGS

·         Air is taken through nostrils.

·         The air passing through nostrils is filtered by fine hairs and mucus.

·         Then the air passes through the throat and into lungs.

·         Rings of cartilage (flexible bones) present in the throat ensure the passage from getting collapsed.

·         Inside the lungs the passage divides into smaller and smaller tubes and ends up in balloon-like structure called alveoli.

·         Alveoli provide increased surface area for the exchange of gas.

·         Walls of alveoli are supplied with blood vessels.

·          

·         When we breathe in, our ribs lift and diaphragmflatten and the chest cavity becomes larger.

·         Because of this, air is sucked into the lungs and it fills the alveoli.

·         Blood brings CO₂ from the rest of the body and releases into the alveoli.

·         The O₂ in the alveoli is taken up by blood to be transported to all the cells in the body.

·         When air is let out the diaphragm relaxes and reduces the chest cavity.

·         During the breathing cycle, (when the air is taken in and let out) the lungs always contains a residual volume of air so that there is sufficient time for O₂ to be absorbed and for the CO₂ to be released.

·         In small or unicellular organisms exchange of gases takes place through diffusion (movement from higher concentration to lower concentration).

·         In large animals diffusion is not possible, as the movement of one molecule of O₂ from the lungs to the feet will take nearly 3 years!

·         Instead we have respiratory pigments (haemoglobin) to take up O₂ from the lungs & carry to the cells that require them.

·         Haemoglobin has a very high affinity for O₂. This is present in RCBs.

·         CO₂ is more soluble in H₂O than O₂ is, so it is mostly transported in dissolved form in our blood.

TRANSPORTATION

·         Blood consists of fluid medium called plasma in which cells are suspended.

·         Plasma transports food, carbon dioxide and nitrogenous waste in dissolved form.

·         Oxygen is carried by the RBCs.

·         A pumping organ is needed to transport these substances by blood called ‘heart’.

THE HEART

·         Heart – muscular organ which is as big as our fist.

·         Heart has 4 different chambers to prevent the mixing of oxygen-rich blood and the blood containing CO₂.

·         The CO₂ rich blood comes to the lungs for removal of CO₂ and the oxygenated blood from the lungs comes to the heart and is pumped to various organs of the body.

STEP BY STEP PROCESS

1.    O₂ RICH BLOOD

·         O₂ rich blood from the lungs comes to the left atrium.

·         The left atrium relaxes and collects the blood.

·         The left atrium then contracts, while the left ventricle expands.

·         The blood from left atrium is transferred to left ventricle.

·         When left ventricle contracts, the blood is pumped out of the body.

 

2.    DE-OXYGENATED BLOOD

·         De-oxygenated blood comes from the body to the right atrium.

·         The right atrium contracts, while the right ventricle expands.

·         The blood from right atrium is transferred to right ventricle.

·         When the right ventricle contracts, the blood is pumped to the lungs for oxygenation.

 

 

·         As ventricles have to pump blood to various organs, they have thicker muscular wall than atrium.

·         Valves present in the blood vessels ensure that blood doesn’t flow backwards.

BLOOD VESSELS

·         Arteries – vessels that carry blood away from the heart to various organs of the body (carries O₂ rich blood).

·         Exception – Pulmonary arterycarries de-oxygenated blood.

·         Arteries have thick, elastic walls – as the blood which they carry emerge from heart under high pressure.

·         Veins – carry blood collected from various parts of the body and bring it back to heart. (De-oxygenated blood).

·         Exception – Pulmonary vein carries O₂ rich blood.

·         Veins don’t need thick walls as the blood they carry is not under pressure.

·         On reaching an organ/tissue the artery divides into smaller and smaller branches that can reach each and every cell in our body.

·         The smaller vessels are only one cell thick and are called capillaries.

·         The capillaries, after the exchange of materials join together to form veins that carry blood away from the organ.

DIFFERENCE BETWEEN ARTERIES AND VEINS

ARTERIES	VEINS
They are thick walled.	They are thin walled.
Valves are absent.	Valves are present.
They carry oxygenated blood except Pulmonary artery.	They carry deoxygenated blood except Pulmonary vein.
Blood from heart flows to different organs.	Blood from different organs flows to heart.
The flow of blood is fast and under high pressure.	The flow of blood is slow and under less pressure.

 

BLOOD VESSELS INVOLVED IN CIRCULATION

·         PULMONARY VEIN brings O₂ rich blood from the lungs to the left atrium.

·         AORTA carries O₂ rich blood from the left ventricle to various organs of the body.

·         VENA CAVA brings de-oxygenated blood from various parts of the body to right atrium.

·         PULMONARY ARTERY carries de-oxygenated blood from right ventricle to the lungs for oxygenation.

BLOOD PRESSURE

·         The force that the blood exerts against the walls of a vessel is called Blood Pressure.

·         Blood pressure (BP) is greater in arteries than in veins.

·         It is measured using an instrument called Sphygmomanometer.

·         The pressure of blood in artery during ventricular systole (contraction) is called Systolic pressure.

·         The pressure of blood in artery during ventricular diastole (relaxation) is called Diastolic pressure.

·         The normal BP is 120/80 mm of Hg.

·         High blood pressure is called hyper tension.

PLATELETS

·         When there is an injury in the blood vessels blood start to leak and this may reduce pressure in the flow of blood.

·         To prevent the leakage, platelets present in the blood helps to clot the breakage at the point of injury.

LYMPH

·         Lymph is another type of fluid involved in transportation.

·         Lymph is also called tissue fluid.

·         Through the pores present in the walls of capillaries some amount of plasma, proteins and blood cells escape into the intercellular spaces in the tissue to form tissue fluid as lymph.

·         Lymph is similar to plasma but colourless and contains less protein.

·         Lymph drains into lymphatic capillaries which then join to form lymph vessels that open into larger veins.

·         Lymph carries digested and absorbed fat from intestine.

TRANSPORTATION IN PLANTS

·         Plant takes in raw materials from soil through roots.

·         If the distance between the soil and the chlorophyll containing organ is less the raw materials (water + nutrients) can pass by simple diffusion.

·         In tall plants (trees) diffusion is not possible.

·         Plants transport system consists of two conducting tubes.

o   XYLEM – moves water and minerals from soil

o   PHLOEM – moves products of photosynthesis from leaves to other parts of the plants.

TRANSPORTATION OF WATER

·         In Xylem tissue, vessels and tracheids of the root, stem and leaves are interconnected to form a continuous system which conducts water to all the parts of the plants.

·         At the roots, cells in contact with the soil actively take up ions.

·         This creates a difference in the concentration of the ions between the roots and the soil.

·         Water therefore moves into the roots to eliminate this difference.

·         Thus, water is pushed upwards steadily.

·         Another method in which water moves upward is through transpiration.

·         Transpiration – the loss of water in the form of vapour from the aerial parts of the plant is known as transpiration.

·         When stomata opens water molecules are lost in the form of vapour this creates suction and water molecule is taken up by the roots.

·         Thus transpiration helps in the absorption and upward movement of water and minerals from roots to the leaves.

·         It also helps in temperature regulation.

TRANSPORTATION OF FOOD AND OTHER SUBSTANCES

·         The transport of product of photosynthesis is called Translocation.

·         Translocation takes place through vascular tissue called Phloem.

·         Phloem transports amino acids and other substances.

·         These substances are delivered to storage organs of roots, fruits and seeds and to growing organs.

·         The translocation takes place in the sieve tubes with the help of companion cells.

·         Translocation takes place by utilising energy (ATP).

·         This energy increases the osmotic pressure in phloem which transports materials in the phloem to tissues which have less pressure.

EXCRETION

·         Metabolic activities generate nitrogenous waste material which should be removed.

·         The biological process that removes the nitrogenous harmful waste from the body is called Excretion.

·         Excretion in simple unicellular organisms occurs by diffusion.

·         In complex multicellular organisms special organs are involved in excretion.

 

 

EXCRETION IN HUMAN BEINGS

·         The excretory system in human beings include

o   A pair of Kidneys

o   A pair of Ureters

o   A Urinary bladder

o   A Urethra

·         Kidneys are located in the abdomen, one on either side of the backbone.

·         Urine produced in the kidneys passes through the ureters into the urinary bladder.

·         Urine is stored in the urinary bladder until it is released through the ureters.

HOW IS URINE PRODUCED?

·         The purpose of making urine is to filter the nitrogenous waste from the blood.

·         Nitrogenous wastes like urea or uric acid are removed from the blood in kidneys.

·         Each kidney has large number of filtration units called Nephrons.

·         Nephrons are cluster of very thin walled blood capillaries.

·         Each blood capillary is associated with the cup-shaped end of tube that collects the filtered urine.

·         As the urine flows through the tube some substance such as the glucose, amino acids, salts and major amount of water are re-absorbed.

·         The urine thus formed in each kidney is sent to the urinary bladder through the ureters and stored in the bladder till it is released through ureters.

 

ARTIFICIAL KIDNEY (HAEMODIALYSIS)

·         Kidney failure lead to accumulation of poisonous wastes in the body, which can even lead to their death.

·         In this case an artificial kidney can be used.

·         An artificial kidney is a device used to remove nitrogenous wastes from the blood through dialysis.

·         Artificial kidneys contains a number of tubes with semi-permeable lining, suspended in a tank filled with dialysing fluid with the same osmotic pressure as that of blood.

·         The patient’s blood is passed through the tubes, during the passage the waste products from the blood pass into dialysing fluid by diffusion.

·         The purified blood is again pumped into patient.

·         Reabsorption is not possible in an artificial kidney.

EXCRETION IN PLANTS

·         Plants excrete O₂ through stomata.

·         Excess of water is lost by transpiration.

·         Other wastes are stored as resins and gums especially in old xylem.

·         Plants also excrete wastes into the soil around them.