Review Questions

Roles of Nitrogen:

Plants get nitrogen in the form of nitrates. Nitrogen is a major component of proteins, hormones, chlorophyll, vitamins, and enzymes essential for plant life. Nitrogen metabolism is a major factor in stem and leaf growth. Too much nitrogen can delay flowering and fruiting.

Effects of the lack of nitrate ions:

Deficiencies of nitrogen can reduce yields, cause yellowing of the leaves, and stunt growth. Roles of Magnesium: Magnesium is a structural component of the chlorophyll molecule and is necessary for the functioning of plant enzymes to produce carbohydrates, sugars, and fats. It is used for fruit and nut formation and is essential for the germination of seeds. Effects of the lack of magnesium ions: Deficiency of magnesium causes yellowing and wilting of leaves

Fertilizers:

Nutrients applied to crops to speed up their growth are called fertilizers.

Classification of Fertilizers:

Fertilizers are broadly classified as organic or inorganic.

1. Importance of inorganic fertilizers:

Naturally occurring inorganic fertilizers include rock phosphate, elemental sulfur, and gypsum that are not chemically modified. If nitrogen is the main element, they are often described as nitrogen fertilizers. Most inorganic fertilizers dissolve readily in water and are immediately available to plants for uptake. These fertilizers efficiently supply the required nutrients for plant growth

1. Importance of organic fertilizers:

Natural organic fertilizer is derived from either plant or animal materials containing one or more essential elements. Organic fertilizers are more complex chemical substances that take time to be broken down into forms usable by plants. They have fewer salts so their larger amounts can be applied without injury to plant roots. However, their excessive amounts can cause environmental degradation due to nitrate leaching or runoff of soluble organic compounds. Manure and compost are used as organic fertilizers. They can also increase soil drainage, aeration, water holding capacity, and the ability of the soil to hold nutrients.

Vitamins: Organic substances which are essential in a small amount to regulate the metabolism and maintain the immune system are called vitamins.

Importance of vitamin A/Function of vitamin A:

Vitamin A was the first fat-soluble vitamin identified in 1913). It performs the following functions.

1. Vitamin A combines with a protein called opsin to form rhodopsin in the rod cells of the retina of the eye. When vitamin A is inadequate, the lack of rhodopsin makes it difficult to see in dim light.
2. It is involved in normal cell differentiation, a process through which embryonic cells transform into mature cells with highly specific functions.
3. Vitamin A supports male and female reproductive processes and bone growth. iv. It is essential for immune function and vitamin-A deficiency causes decreased resistance to infections.
4. It is essential for immune function and vitamin-A deficiency causes decreased resistance to infections.

Importance of vitamin C/Function of vitamin C (Ascorbic Acid):

1. Vitamin C participates in many reactions by donating electrons, essential to the activity of many enzymes. Collagen: Vitamin C is needed to form collagen (a fibrous protein) that gives strength to connective tissues. Collagen is also needed for the healing of wounds.
2. Vitamin C in white blood cells enables the immune system to function properly.

Importance of vitamin D/Function of vitamin D:

1. The best-known function of vitamin D is to help regulate blood levels of calcium and phosphorous
2. Vitamin D increases absorption of these minerals from the intestine and their deposition in bones.

Role of Calcium:

Calcium is essential for the development and maintenance of bones and teeth. It is also needed for maintaining cell membranes and connective tissues and for the activation of several enzymes. Calcium also aids in blood clotting.

Foods Containing Calcium:

Humans get calcium from milk, cheese, egg yolk, beans, nuts, cabbage, etc.

Effects of Deficiency of Calcium:

The deficiency of calcium causes the spontaneous discharge of nerve impulses which may result in tetany Bones also becoming soft, blood clots slowly, and wounds healing slowly.

Role of Iron:

Iron plays a major role in oxygen transport and storage and is a component of hemoglobin in red blood cells and myoglobin in muscle cells. Cellular energy production also requires iron which acts as an enzyme cofactor. Iron also supports immune function.

Foods Containing Iron:

Humans get iron from red meat, egg yolk, whole wheat, fish, spinach, mustard, etc.

Effects of Deficiency of Iron:

Iron deficiency causes anemia which affects hundreds of millions of people. Infants, young children, adolescents, and pregnant and lactating women are especially vulnerable due to their high demand for iron.

Effects of water and dietary fibre:

Water and dietary fibre are not considered nutrients, but they do play important role in life.

Importance of water in our diets:

1. Approximately 60% of the adult human body is composed of water. Nearly all life-sustaining chemical reactions require an aqueous (watery) environment.
2. Water also functions as the environment in which water-soluble foodstuff is absorbed in the intestines and the waste products are eliminated in urine.
3. Another essential role of water is to maintain body temperature through evaporation, as in sweating.
4. Severe dehydration may result in cardiovascular problems.
5. Water toxicity (too much water) is also possible, resulting in dilution of important electrolytes (mineral salts) that may lead to irregular heart rhythm.
6. The estimated water requirement of an average adult is two litres per day.

Important sources of daily water intake are natural water, milk, juicy fruits and vegetables.

Importance of Dietary fibre "roughage" in our diets:

Dietary fibre (also known as "roughage") is the part of human food that is indigestible. It is found only in plant foods and it moves undigested through the stomach and small intestine and into the colon.

Types of dietary fibre:

There are two types of dietary fibre; insoluble and soluble.

Insoluble fibre:

Insoluble fibre travels through the small intestines quickly. Wheat bran, whole-grain bread and cereals, as well as the skins of many fruits and vegetables consist of insoluble fibres.

Soluble fibre:

Soluble fibre breaks down as it passes through the digestive tract, forming a gel. This gel traps some substances, and it helps in lowering the blood levels of cholesterol and sugars. Examples of soluble fibres are oats, beans, barley, and many fruits and vegetables.

The recommended dose of fibre per day:

Physicians recommend consuming 20 to 35 grams of fibre per day.

Functions of fibre:

1. Fibre prevents and relieves constipation by stimulating the movement of the intestinal muscles, increasing stool bulk and making stools softer and easier to pass.
2. It also controls weight by creating a feeling of fullness without adding too many calories to the diet.

Reduction of risks by dietary fibre:

Dietary fibre can also reduce the risk of many other health conditions for example:

1. Avoiding constipation reduces the risk of developing haemorrhoids (swollen anal tissues).
2. Soluble fibre takes some acids away in the stool and in response, the liver draws cholesterol from the blood to make more acids, thus lowering blood cholesterol.
3. Soluble fibre slows the absorption of blood sugar from the small intestine, lowering blood sugar levels.
4. Insoluble fibre minimizes exposure to carcinogens (cancer-causing agents) that may be in the stool by diluting them and speeding their movement through the bowel.

Balanced Diet:

A balanced diet may be defined as one which contains all the essential nutrients like carbohydrates, fats, proteins, minerals, and vitamins in the correct proportion for the normal growth and development of the body.

Relation of a balanced diet with age, gender, and activity:

A balanced diet is related to the state of one's age, sex, and activity Balance Diet during growth period: During the growth period of the body there is a higher metabolic rate in body cells and so the body needs a balanced diet that contains more energy.

Balance Diet during the adult period:

Adults need fewer proteins per kg body weight, but a growing boy or girl needs more proteins per kg weight. Similarly, children need more calcium and iron for their growing bones and red blood cells respectively.

Impact of gender on Balance Diet:

Gender has an impact on the requirements of a balanced diet. Women have comparatively less metabolic rates than men of the same age and weight. So, men need a balanced diet that provides comparatively more energy than women require.

Different people have different lifestyles and varied nature of work. A man with sedentary habits does not require as much energy as a man who is on his feet for most of the day.

Problems Related to Nutrition (Malnutrition)

Problems related to nutrition are grouped as malnutrition. Malnutrition is a term for the condition caused by an improper or insufficient diet. It most often refers to undernutrition resulting from inadequate consumption, poor absorption, or excessive loss of nutrients, Malnutrition also includes overnutrition, resulting from overheating or excessive intake of specific nutrients.

Major Forms of Malnutrition:

Common forms of malnutrition include protein-energy malnutrition (PEM), mineral deficiency disease (MDD), and over-intake of nutrients (OIN).

Protein-Energy Malnutrition (PEM):

Protein-energy malnutrition refers to inadequate availability or absorption of energy and proteins in the body. It is the leading cause of death in children in developing countries.

Primary PEM:

Primary PEM results from a diet that lacks sufficient sources of protein and/or energy.

Secondary PEM:

Secondary PEM occurs as a complication of other diseases (AIDS, cancer, kidney failure, etc) that impair the body's ability to absorb or use nutrients.

Diseases caused by PEM:

PEM may lead to diseases such as Kwashiorkor and marasmus

1. Kwashiorkor:

   Kwashiorkor is due to protein deficiency at the age of about 12 months when breastfeeding is discontinued, but it can also develop at any time during a child's growing years. Children may grow to normal height but are abnormally thin.

2. Marasmus:

   Marasmus usually develops between the ages of six months and one year in children. Patients lose all their body fat and muscle strength and acquire a skeletal appearance. Children with marasmus show poor growth and look small for their age.

Mineral Deficiency Diseases (MDD):

Diseases resulting from the deficiency of a mineral are relatively rare among humans. Some examples are given below:

1. Goiter:

   Goiter is a condition caused by an insufficient amount of iodine in the diet. Iodine is used by the thyroid gland to produce hormones that control the body's normal functioning and growth. If sufficient iodine is not available in a person's diet, the thyroid gland becomes enlarged and results in swelling in the neck and the condition is known as goiter.

2. Anemia:

   Anemia is the most common of all mineral deficiency diseases. The term anemia means "a lack of blood." The condition is caused when the number of red blood cells is reduced to a level lower than normal. We know that the hemoglobin molecule contains a single atom of iron at its center. If the body fails to receive sufficient amounts of iron, an adequate number of hemoglobin molecules will not be formed. In that case, there are not enough functioning red blood cells. A person becomes weak and listless.

Over-Intake of Nutrients (OIN):

Over-intake of nutrients (OIN) is a form of malnutrition in which more nutrients are taken than the amounts required for normal growth, development, and metabolism. The effects of the over-intake of nutrients are usually intensified when there is a reduction in daily physical activity (decline in energy expenditure).

Over-intake of nutrients causes several health problems. For example, a high intake of carbohydrates and fats leads to obesity, diabetes, and cardiovascular problems. Similarly, a high dose of vitamin A causes loss of appetite and liver problems, and an excess dose of vitamin D can lead to the deposition of calcium in various tissues, etc.

Famine-the major Cause of Malnutrition:

Famine is the lack of enough food to feed all the people living in an area. It is a social and economic crisis that results in malnutrition and increased mortality Historically, famines have occurred because of drought, crop failure, and because of man-made causes such as war or misguided economic policies. The most terrible famines of the twentieth century include the disaster in Bengal (1942-1945), famines in China (1928 and 1942), and famine in Ukraine (1932-33). The last great famines of this century were the disaster in Cambodia Ethiopian famine (1983-85) and the North Korean famine (the 1990s). Famine may be due to unequal distribution of flood, drought, flooding, or increasing population.

Unequal distribution of food:

The achievements in science have enabled human beings to produce better food in terms of quality and quantity. Today the agricultural practices produce more than enough food that can be supplied to everyone on earth. But due to political and administrative problems, the food is not equally distributed to the different regions of the world. The result is that there is always surplus food in countries like America, the UK, Canada, etc, and at the same time people have nothing to eat in countries like Ethiopia, Somalia, etc.

Alimentary canal:

The digestive system of a human consists of a long tube that extends from the mouth to the anus. This tube is called the alimentary canal. Structure of human alimentary canal: Main sections of the alimentary canal are:

1. Oral cavity 2. Pharynx 3. Oesophagus,                 
2. Stomach 5. Small intestines               6. Large intestine.

Glands associated with the alimentary canal:

In addition, there are many glands associated with the alimentary canal. These are the three pairs of salivary glands, the pancreas, and the liver.

Oral cavity - (Selection, grinding, partial digestion):

Functions of the oral cavity:

1. Food Selection:

The oral cavity is the space behind the mouth and has many important functions in the whole process. Food selection is one of them. When food enters the oral cavity, it is tasted and felt. If the taste of mutton suggests that it is old, we reject it. If the teeth or tongue detect some hard object, such as dirt, we also reject that bite. The senses of smell and vision also help the oral cavity in the selection of food.

2. Grinding of food:

The second function of the oral cavity is the grinding of food by teeth. It is known as chewing or mastication. This is useful first because the esophagus can pass only small pieces and secondly because enzymes cannot act on large pieces of food. They require small pieces with large surface areas to attack.

3. Lubrication and chemical digestion of food:

The third and fourth functions of the oral cavity are the lubrication and chemical digestion of food. The chewing process stimulates the three pairs of salivary glands (under the tongue, behind the jaws, and in front of the ears) to release a juice called saliva in the oral cavity.

Functions of Saliva:

Saliva has two main functions. First, it adds water and mucous to the food which acts as lubricants to ease the passage of food through the esophagus. Second, saliva contains the enzyme salivary amylase, which aids in the partial digestion of starch.

Bolus:

After the processes of chewing, lubrication, and partial digestion the pieces of bread and mutton are rolled up by the tongue into a small, slippery, spherical mass called a bolus. We swallow the bolus and push it into the esophagus through the pharynx.

Pharynx and Oesophagus- (Swallowing and Peristalsis):

The bolus is swallowed and then pushed down by the movement called peristalsis.

Steps in swallowing:

During swallowing the bolus is pushed to the back of the mouth by the tongue. The soft palate moves upward and to the rear to close the opening of the nasal cavity.

When swallowed, the bolus goes to the pharynx, which makes special adaptations to prevent choking or aspiration when food is swallowed. When the larynx (the top of the trachea) moves upward, it forces the. epiglottis (a flap of cartilage) into a more or less horizontal position thus closing the glottis i.e., opening of the windpipe (trachea) The beginning of the swallowing action is voluntary, but once the food reaches the back of the mouth, swallowing becomes automatic.

After being swallowed, the food enters the tube called the esophagus, which connects the pharynx to the stomach. Neither the pharynx nor the esophagus contributes to digestion and the previous digestive actions of saliva continue.

Steps in Peristalsis:

Peristalsis moves the food from the oral cavity to the rectum. It is defined as the rhythmic sequence of waves of contraction in the smooth muscles of the walls of the alimentary canal, thus squeezing the food down along the alimentary canal.

Note:

If due for any reason, the direction of peristalsis reverses, what would be the result? It results would be vomiting.

Stomach - (Digestion, churning, and melting):

The stomach is a dilated part of the alimentary canal. It is J-shaped, located on the left of the abdomen, just beneath the diaphragm.

Portions of Stomach:

The stomach has two main portions.

1. Cardiac portion:

The cardiac portion is present immediately after the esophagus.

1. Pyloric portion:

 The pyloric portion is located beneath the cardiac portion. The stomach has two sphincters (openings that are guarded by muscles).

Cardiac sphincter and pyloric sphincter:

The cardiac sphincter is between the stomach and esophagus while the pyloric sphincter is between the stomach and the small intestine. The bolus enters the stomach from the esophagus through the cardiac sphincter.

Entrance of Food In the stomach:

When food enters the stomach, the gastric glands found in the stomach wall are stimulated to secrete gastric juice. It is composed chiefly of mucous, hydrochloric acid, and a protein-digesting enzyme pepsinogen.

Functions of Hydrochloric acid:

Hydrochloric acid converts the inactive enzyme pepsinogen into its active form called pepsin, HCI also kills microorganisms present in food. Pepsin partially digests the protein portion of the food (the bulk of mutton) into polypeptide and shorter peptide chains.

Churning action:

In the stomach, food is further broken apart through a process of churning. The walls of the stomach contract and relax and these movements help in the thorough mixing of the gastric juice and food. The churning action also produces heat which helps to melt the lipid content of the food.

Note:

The starch in our bite of bread and the protein in mutton have been partially digested and the food has been converted to a soup-like mixture called chyme. After it, the pyloric sphincter allows a little mass of chyme to enter the duodenum.

Small Intestine - (Complete digestion and absorption):

The function of Small Intestine:

Duodenum comprises the first 10 inches (25 cm) of the small intestine and it is the part of the alimentary canal where most of the digestive process occurs. Here the food is further mixed with 3 different secretions.

1. Bile from the liver helps in fat digestion through emulsification.
2. Pancreatic juice from the pancreas contains enzymes trypsin, pancreatic amylase, and lipase which digest proteins, carbohydrates, and lipids respectively
3. Intestinal juice from the intestine walls contains many enzymes for the complete digestion of all kinds of food.

Jejunum:

Next to the duodenum is 2.4 meters long jejunum. It is concerned with the rest of the digestion of the proteins, starch, and lipids of our bite.

The function of Ileum:

Last 3.5 meters long part of the small intestine is the ileum. It is concerned with the absorption of digested food.

The function of Villi:

There are circular folds in the inner wall of the ileum. These folds have numerous fingerlike projections called villi (singular: Villus). The villi increase the surface of the inner walls and it helps a lot in the absorption of digested food. Each villus is richly supplied with blood capillaries and a vessel of the lymphatic system called a lacteal. The walls of the villus are only single-cell thick. The digested molecules i.e., simple sugars and amino acids are absorbed from the intestine into the blood capillaries present in villi. The blood carries them away from the small intestine via the hepatic portal vein and goes to the liver for filtering, removal of toxins, and nutrient processing. Fatty acids and glycerol are absorbed into the lymphatic vessel (lacteal) present in villi, which carries them to the main lymphatic duct, from where they enter the bloodstream.

Large intestine- (Absorption of water and defecation)

After the digested products of our bite have been absorbed in the blood, the remaining mass enters the large intestine.

Parts of Large intestine:

It has 3 parts:

1. The caecum (or pouch that forms the T-junction with the small intestine).
2. The colon
3. The rectum.

From the colon, water is absorbed into the blood. As the water is absorbed, the solid remains of the food are called feces. The feces contain the undigested material A large number of bacteria, sloughed-off cells of the alimentary canal, bile pigments, and water are also part of the feces. Feces are temporarily stored in the rectum, which opens out through the anus. Under normal conditions when the rectum is filled up with feces, it gives rise to a reflex, and the anus is opened for defecation.

Pharynx and Oesophagus - (Swallowing and Peristalsis):

The bolus is swallowed and then pushed down by the movement called peristalsis.

Steps in swallowing:

During swallowing the bolus is pushed to the back of the mouth by the tongue. The soft palate moves upward and to the rear to close the opening of the nasal cavity. When swallowed, the bolus goes to the pharynx, which makes special adaptations to prevent choking or aspiration when food is swallowed. When the larynx (the top of the trachea) moves upward, it forces the epiglottis (a flap of cartilage) into a more or less horizontal position thus closing the glottis i.e., opening of the windpipe (trachea) The beginning of the swallowing action is voluntary, but once the food reaches the back of the mouth, swallowing becomes automatic.

After being swallowed, the food enters the tube called the oesophagus, which connects the pharynx to the stomach. Neither the pharynx nor the oesophagus contributes to digestion and the previous digestive actions of saliva continue.

Steps in Peristalsis:

Peristalsis moves the food from the oral cavity to the rectum. It is defined as the rhythmic sequence of waves of contraction in the smooth muscles of the walls of the alimentary canal, thus squeezing the food down along the alimentary canal.

It result would be vomiting.

Disorders of the gut:

Diarrhea, constipation, and ulcer are the most common disorders of the gut that affect several people.

Diarrhea:

Diarrhea is a condition in which the sufferer has frequent watery, loose bowel movements.

Signs and symptoms of Diarrhea:

This condition may be accompanied by abdominal pain, nausea, and vomiting.

Causes of Diarrhea:

It occurs when required water is not absorbed in blood from the colon. If the colon is damaged or inflamed, absorption is inhibited, and watery stools result. The main causes of diarrhea include a lack of adequate safe water. Diarrhea is also caused by viral or bacterial infections.

Recovery of diarrhea:

If sufficient food and water are available a patient recovers from diarrhea in a few days. However, for malnourished individuals’ diarrhea can lead to severe dehydration and can become life-threatening.

Treatment of diarrhea:

The treatment for diarrhea involves consuming adequate amounts of water to replace the loss, preferably mixed with electrolytes to provide essential salts and some amount of nutrients. Antibiotics may be required if diarrhea is due to bacterial infection.

Preventions for diarrhea:

Preventions for diarrhea include taking proper water and electrolytes, eating regularly, and taking hygienic measures.

Constipation:

Constipation is a condition where a person experiences hard feces that are difficult to eliminate.

Signs and Symptoms of constipation:

In severe cases, it may lead to symptoms of bowel obstruction.

Causes of Constipation:

The main causes of constipation include hardening of the feces due to excessive absorption of water through the colon, insufficient intake of dietary fiber, dehydration, use of medicines (e.g., those containing iron, calcium, and aluminum), injured anal sphincter, and tumors in the rectum or anus.

Treatment of constipation:

Treatment of constipation is with a change in dietary and exercise habits. Enemas can be used to provide a form of mechanical stimulation. Laxatives (e.g., paraffin) may be necessary in some cases.

Prevention of constipation:

Constipation is usually easier to prevent than to treat. One should take the required quantities of water and dietary fibers.

Ulcers:

An ulcer (peptic ulcer) is a sore in the gut lining caused by a gradual breakdown of the tissue by the acidic gastric juice. An ulcer of the stomach is called a gastric ulcer of the duodenum, a duodenal ulcer, and of the esophagus, an esophageal ulcer.

Causes of Ulcer:

The causes of ulcers include excess acid, infection, long-term use of anti-inflammatory medicines (including aspirin), smoking, drinking coffee, and colas, and eating spicy foods.

Signs and Symptoms of Ulcer:

The signs and symptoms of an ulcer include abdominal burning after meals or at midnight. Severe ulcers may cause abdominal pain, the rush of saliva after an episode of regurgitation, nausea, loss of appetite, and weight loss.

Treatment of Ulcer:

An ulcer is treated with medicines containing alkaline composition.

Prevention of Ulcers:

Preventive measures should be adopted for such complications. Spicy foods and those containing more acidity should be avoided. As smoking is a major factor in ulcers, it should be avoided.

Saturated fatty acids can increase a person's cholesterol level. An increased cholesterol level may eventually result in the clogging of arteries and, ultimately, heart disease.

Importance of vitamin A/Function of vitamin A:

Vitamin A was the first fat-soluble vitamin identified in 1913). It performs the following functions

1. Vitamin A combines with a protein called opsin to form rhodopsin in the rod cells of the retina of the eye. When vitamin A is inadequate, the lack of rhodopsin makes it difficult to see in dim light.
2. It is involved in normal cell differentiation, a process through which embryonic cells transform into mature cells with highly specific functions.
3. Vitamin A supports male and female reproductive processes and bone growth.

iv. It is essential for immune function and vitamin-A deficiency causes decreased resistance to infections. 

Bolus:

The small, slippery, spherical mass of food formed in the oral cavity during the processes of mastication, lubrication, and semi-digestion.

Chyme:

The soup-like mixture formed after the action of the stomach on food. 

The stomach has two sphincters (openings that are guarded by muscles). The cardiac sphincter is between the stomach and esophagus while the pyloric sphincter is between the stomach and the small intestine. The bolus enters the stomach from the esophagus through the cardiac sphincter. 

Entrance of Food in the stomach:

When food enters the stomach, the gastric glands found in the stomach wall are stimulated to secrete gastric juice. It is composed chiefly of mucous, hydrochloric acid, and a protein-digesting enzyme pepsinogen.

Functions of Hydrochloric acid:

Hydrochloric acid converts the inactive enzyme pepsinogen into its active form called pepsin, HCI also kills microorganisms present in food. Pepsin partially digests the protein portion of the food (the bulk of mutton) into polypeptide and shorter peptide chains.