In this lesson, we will explore the importance of nutrition for all organisms, as they need food for growth, energy, and normal functioning. Nutrition is the process by which organisms obtain, absorb, and convert food into body substances necessary for these purposes. Nutrients are the essential elements and compounds that organisms acquire and use for energy or to create new materials.

Autotrophic organisms, such as plants, gather water, carbon dioxide, and minerals from their environment to make their own food, which they use for growth and energy. In contrast, heterotrophic organisms, including animals and fungi, obtain their food from other organisms to fulfill their energy and growth requirements.

Roles of Nitrogen and Magnesium in Plants

Plants absorb nitrogen in the form of nitrates, which is essential for the formation of proteins, hormones, chlorophyll, vitamins, and enzymes. Nitrogen is crucial for stem and leaf growth, but too much can delay flowering and fruiting. A deficiency can lead to reduced yields, yellowing leaves, and stunted growth.

Magnesium, on the other hand, is a key component of chlorophyll and is necessary for the proper functioning of plant enzymes that produce carbohydrates, sugars, and fats. It plays a vital role in fruit and nut formation and is essential for seed germination. A lack of magnesium can cause yellowing and wilting of leaves.

Importance of Fertilizers

As humans began cultivating plants, they discovered that adding certain materials to the soil could enhance plant characteristics, such as increased fruit production and faster growth. These materials are known as fertilizers, which can be classified as organic or inorganic.

Inorganic fertilizers, like rock phosphate and elemental sulfur, occur naturally and are not chemically modified. Nitrogen fertilizers are those that primarily contain nitrogen. These fertilizers dissolve quickly in water, making nutrients readily available to plants.

Organic fertilizers come from plant and animal materials and are more complex, taking time to break down into usable forms for plants. Examples include manure and compost, which improve soil drainage, aeration, and nutrient retention. Although urea is an organic compound, it is often grouped with inorganic fertilizers due to its chemical synthesis.

Some plants, like carnivorous plants, have adapted to trap and digest small animals, using the resulting nutrients to supplement their nitrogen supply.

Environmental Hazards Related to Fertilizer Use

The excessive use of inorganic fertilizers can negatively impact soil nutrient retention and lead to environmental issues like eutrophication, which is the over-enrichment of ecosystems with nutrients. The storage and application of nitrogen fertilizers can also release greenhouse gases like nitrous oxide and ammonia, increasing soil acidity and leading to pest problems due to heightened reproduction rates.

Therefore, it is important to assess the nutrient content of the soil and the needs of the crops before applying inorganic fertilizers. Excessive organic fertilizers can also cause environmental problems through nitrate leaching and runoff of soluble organic compounds.

Components of Human Food

Human nutritional needs are more complex than those of plants, as we require various nutrients, including carbohydrates, lipids, nucleic acids, proteins, minerals, vitamins, and water.

Carbohydrates

Carbohydrates are the primary source of energy for humans, providing about half to two-thirds of our daily caloric intake. Glucose is the most commonly used carbohydrate for energy, but others, such as maltose, lactose, sucrose, and starch, are also important. Carbohydrates contain 4 kilocalories per gram, and we obtain them from foods like bread, pasta, beans, potatoes, rice, and cereals. While proteins and lipids are essential for building body components, they can also be used for energy. However, consuming saturated fatty acids can raise cholesterol levels, potentially leading to heart disease.

Lipids

Lipids consist of fatty acids bonded to glycerol and can be classified as saturated or unsaturated. Saturated fatty acids have all carbon atoms bonded to hydrogen, making them solid at room temperature, while unsaturated fatty acids have some double bonds and are typically liquid at room temperature. For example, butter contains about 70% saturated and 30% unsaturated fatty acids, while sunflower oil has around 75% unsaturated fatty acids. Lipids are crucial for forming cell membranes, insulating neurons, and producing certain hormones. They provide a significant energy source, with 1 gram of lipids containing 9 kilocalories. Important lipid sources include milk, butter, cheese, eggs, meat, fish, nuts, and seeds.

Proteins

Proteins are made up of amino acids and are vital for growth, making up key components of cells, membranes, and tissues like muscles and ligaments. Many proteins also function as enzymes and can be used for energy, providing 4 kilocalories per gram. Dietary sources of protein include meat, eggs, grains, legumes, and dairy products like milk and cheese. Notably, proteins can be converted into carbohydrates when needed.

Minerals

Minerals are inorganic elements that come from the Earth and cannot be produced by the body. They play essential roles in various bodily functions and are necessary for maintaining health. Most minerals in our diet come from plants and water, or indirectly from animal foods. Minerals are categorized into major minerals, which are needed in amounts of 100 mg or more per day, and trace minerals, required in smaller amounts. Each type of mineral has specific roles in the human body.

Role of Calcium and Iron

Calcium is vital for developing and maintaining strong bones and teeth. It helps maintain cell membranes, connective tissues, and activates several enzymes. Additionally, calcium plays a crucial role in blood clotting. Good dietary sources of calcium include milk, cheese, egg yolk, beans, nuts, and cabbage. A deficiency in calcium can lead to issues such as spontaneous nerve impulses, softening of bones, slow blood clotting, and delayed wound healing.

Iron is essential for transporting and storing oxygen in the body. It is a key component of hemoglobin in red blood cells and myoglobin in muscle cells. Iron is also necessary for cellular energy production and acts as a cofactor for many enzymes involved in cellular respiration. Furthermore, it supports immune function. Humans obtain iron from foods like red meat, egg yolk, whole wheat, fish, spinach, and mustard. Iron deficiency is the most common nutrient deficiency worldwide and can lead to anemia. Adequate calcium intake, combined with low salt and high potassium consumption, can help prevent hypertension and kidney stones.

Vitamins

Vitamins are essential chemical compounds required in small amounts for normal growth and metabolism. They can be classified into two groups: fat-soluble vitamins (A, D, E, and K) and water-soluble vitamins (B vitamins and vitamin C).

Vitamin A was the first fat-soluble vitamin discovered. It is crucial for forming rhodopsin in the rod cells of the retina, which is important for seeing in dim light. Vitamin A also aids in cell differentiation, supporting bone growth and immune function. Cooking or heating can destroy water-soluble vitamins more easily than fat-soluble ones.

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