Haemoglobin is a type of globular protein present in red blood cells (RBCs), which transports oxygen in our body through blood. It is a tetrameric protein and contains the heme prosthetic group attached to each subunit. It is a respiratory pigment and helps in transporting oxygen as oxyhaemoglobin from the lungs to different parts of the body. Some amount of carbon dioxide is also transported back via haemoglobin as carbaminohaemoglobin.

Other oxygen binding proteins are myoglobin in muscles, haemocyanin in arthropods and molluscs, leghaemoglobin in legumes, etc.

Answer.


a) Salivary glands secrete saliva along with enzymes.Ptyalin is the strach hydrolysing enzyme secreted by salivary glands in human beings. It is also called as salivary amylase. Ptyalin secreted in the mouth brings about digestion of starch in the mouth itself. It hydrolyses starch into disaccharaides like maltose and isomaltose and other small dextrins called as limit dextrins. Ptyalin hydrolyses at about 30 percent of the starch in the mout itself.

b) Gastric glands secrete HCL, pepsinogen, mucous.Gastric juice is a secretion of gastric glands located in the lining of the stomach. It is mainly made up of electrolytes, mucus, enzymes, hydrochloric acid, intrinsic factor etc. HCl secreted by parietal cells provides acidic medium for many enzymes to get activated. Neck cells secrete mucus which lubricated the passage of the food. Chief cells secrete pepsinogen which helps in the digestion of proteins after getting activated into pepsin by HCl. Enzymes of the gastric juice bring about digestion of different components of the food. Gastric lipase helps in emulsification of lipids in the stomach. Partially digested food in the stomach is called as chyme and this passes on into small intestine
c) Intestinal glands are present in the inner lining of small intestine. These secrete various enzymes which aid in the process of digestion of all the components of food. Maltase, sucrase and lactase bring about digestion of carbohydrates. Peptidases help in digestion of proteins. Enterokinase helps in the activation of other enzymes

d) Liver is the largest gland in our body. The liver secretes a yellowish green watery fluid called bile. It is temporarily stored in a sac called the gall bladder. Bile provides an alkaline environment for many enzymes to get active. It also reduces the acidity of chyme. Bile plays an important role in the digestion of fats. Bile is sent into duodenum through a narrow tube-like structure called the bile duct. Bile breaks the larger fat molecules into tiny droplets, thereby increasing their surface area, which helps in the digestion of fats easily.

e) Pancreas is the mixed gland. It acts as both endocrine and exocrine gland. The pancreas secretes the pancreatic juice that helps to digest carbohydrates, proteins and fats. The pancreatic juice converts carbohydrates into simple sugars and glucose, proteins into amino acids, and the lipids into fatty acids and glycerol. Trypsin and chymotrypsin help in the digestion of proteins.

Clayey and loamy soils are both suitable for growing cereals like wheat, and gram. Such soils are good at retaining water. For paddy, soils rich in clay and organic matter and having a good capacity to retain water are ideal. For lentils (masoor) and other pulses, loamy soils, which drain water easily, are required.

Epiglottis is a flap of cartilage that covers the glottis when swallowing. This helps to prevent food and liquid from entering the trachea and lungs.

• Nutrients in the soil are replenished by adding fertilisers and manures.
• Fertilisers and manures contain plants nutrients and minerals like nitrogen, phosphorus and potassium.
• Another way to replenish soil is to grow leguminous crops (for example gram, peas, pulses etc.) in the soil.
• The bacterium called Rhizobium can take atmospheric nitrogen and convert it into a soluble form.

A compound is a substance formed when two or more chemical elements are chemically bonded together. ... Example 1: Pure water is a compound made from two elements - hydrogen and oxygen. The ratio of hydrogen to oxygen in water is always 2:1. Each molecule of water contains two hydrogen atoms bonded to a single oxygen atom. Water is a substance composed of the chemical elements hydrogen and oxygen and existing in gaseous, liquid, and solid states. It is one of the most plentiful and essential of compounds.

They breathe through gills while they are tadpoles. Mature frogs breathe mainly with lungs and also exchange gas with the environment through the skin. Their skin has to stay wet in order for them to absorb oxygen so they secrete mucous to keep their skin moist.

Sericulture, or silk farming, is the rearing of silkworms for the production of raw silk. Silkworms are reared under suitable conditions of temperature and humidity to obtain silk threads from their cocoons. The female silk moth lays hundreds of eggs.
These are stored on strips of cloth or paper. Mulberry leaves are the staple diet of silkworms. When the mulberry tree bears a fresh crop of leaves, the eggs are warmed suitably so that the larvae hatch from them.
The larvae, caterpillars or silkworms are then stored in clean bamboo trays and are fed freshly chopped mulberry leaves. They eat day and night, and grow to enormous sizes. 
The bamboo trays are provided with small racks or twigs to which the cocoons can be attached.
This happens usually after 25 to 30 days when the caterpillars stop feeding and move to the twigs to spin cocoons. The silk moth develops inside these cocoons.

Image formed by concave mirror is real, inverted and diminished in size than the object.

However, when the object is placed at principal focus and pole, it will form a Virtual, erect and magnified image.

The process of releasing energy from food is called respiration. The process of respiration involves taking in oxygen (of air) into the cells, using it for releasing food, and then eliminating the waste products (carbon dioxide and water) from the body.

A concave mirror has the reflecting surface that caves inwards. Concave mirrors converge light to one prime focus point. Therefore, they are also called converging mirrors. They are used to focus light.

Concave Mirror

• A concave mirror produces a smaller, bigger and inverted image based on its distance from the object.
• When the distance between object and mirror is large, a small inverted virtual image is formed.
• As the object is brought closer, the image becomes larger.
• At a very close distance, the image is large and upright.

The process of deriving large crystals of pure substances from their solutions is known as crystallisation. It is a physical change. Crystals of salt are obtained by the evaporation of sea water.

Similarly crystals of copper sulphate can be obtained by adding copper sulphate powder to the boiling solution of water and dilute sulphuric acid. This mixture when filtered and allowed to cool produces crystals of copper sulphate.

1. When a candle burns, both physical & chemical changes occur. On heating, candle wax melts and form liquid wax. It is a physical change. Since it again turns into solid wax on cooling. This is a reversible change. When a candle is burnt in air, the mass of the product is increased due to atmospheric oxygen which show a that it is a chemical change.

3. 

Rusting of Iron

When an iron object is left in damp air (or water) for a considerable time, it gets covered with a red-brown flaky substance called rust. This is called rusting of iron. During the rusting of iron, iron metal combines with the oxygen (of air) in the presence of water (moisture) to form a compound iron oxide. This iron oxide is rust.

Iron + Oxygen +Water ——> Iron Oxide

Fe + O₂ + H₂O ——> Fe₂O₃

Rust is iron oxide (Fe₂O₃). Thus, rust and iron are not the same substance. Rusting of iron is a chemical change.

Methods of preventing iron from rusting

(1) Rusting of iron can be prevented by galvanisation

The process of depositing a thin layer (or coating) of zinc metal on iron objects is called galvanisation.

Galvanisation is done by dipping an iron object in molten zinc metal. A thin layer of zinc metal formed on the surface of an iron object protects it from rusting (because zinc metal remains unaffected by air and moisture). The iron sheets used for making buckets, drums, dust-bins and sheds (roofs) are galvanised to prevent their rusting. The iron pipes used in our homes to carry water are also galvanised to prevent rusting.

(2) Iron is coated with chromium to prevent rusting

This is called chrome-plating. Chromium metal is resistant to the action of air and moisture. So, when a layer of chromium is deposited on an iron object, then the iron object is protected from rusting.

Chromium-plating is done on steel furniture, taps, bicycle handle bars and car bumpers, etc, made of iron and steel to prevent them from rusting.

2. 

(1) Rusting of iron can be prevented by painting

When a coat of paint is applied to the surface of an iron object, then air and moisture cannot come in contact with the iron object and hence no rusting takes place. The window grills, railings, steel furniture, iron bridges, railway coaches, and bodies of cars, buses and trucks, are all painted regularly to protect them from rusting.

(2) Rusting of iron can be prevented by applying grease or oil

When some grease or oil is applied to the surface of an iron object, then air and moisture cannot come in contact with it and hence rusting is prevented.

The tools and machine parts made of iron and steel are smeared with grease or oil to prevent their rusting.

(3) Rusting of iron can be prevented by galvanisation

The process of depositing a thin layer (or coating) of zinc metal on iron objects is called galvanisation.

1. 

Examples of chemical changes :

Souring of milk
Formation of curd from milk
Cooking of food (like rice and chapatis)
Spoilage of food
Change in colour of cut apple (cut brinjal or cut potato) on keeping in air
Photosynthesis
Digestion of food
Neutralisation reaction
Explosion of a firework (or cracker)
Burning of magnesium ribbon
Burning of fuels (like burning of wood, coal, kerosene, LPG and biogas)
Burning of dry leaves
Burning of candle wax
Burning of incense stick
Rusting of iron
Ripening of fruits

Humans are unable to digest cellulose because the appropriate enzymes to breakdown the beta acetal linkages are lacking. ... They have the required enzymes for the breakdown or hydrolysis of the cellulose; the animals do not, not even termites, have the correct enzymes. No vertebrate can digest cellulose directly.

All animals require food for obtaining energy, growth, repair of damaged parts and functioning of the body. The process of taking food by an animal and its utilisation in the body is called animal nutrition.

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A n s w e r :

three hearts

An octopus has three hearts, nine brains, and blue blood. Two hearts pump blood to the gills, while a third circulates it to the rest of the body.

A n s w er

Carbon dioxide turns lime water Milky

Ca(OH)2​+CO2​⟶CaCO3​+H2​O

When carbon dioxide reacts with the lime water Ca(OH)2​, it forms calcium carbonate CaCO3​ which turns lime water milky.

Physical change

The melting of the solid wax to form liquid wax and the evaporation of liquid wax to form wax vapour are physical changes. The burning of the wax vapour is a chemical change.

The meeting of rays at common point is known as convergence. Since convex lens is able to converge light rays therefore it is also called converging lens.

A place where wastewater (or sewage) from houses and other buildings is brought for processing is called wastewater treatment plant. Waste-Water Treatment Plant is written in short form as WWTP. The wastewater treatment plant is also called sewage treatment plant.

The cramps occur when muscle cells respire anaerobically. The partial breakdown of glucose produces lactic acid. The accumulation of lactic acid causes muscle cramps.