Chapter – 3D : Nutrition | Chapter Solution Class 9

(c) Energy

Explanation:

Energy is essential for all life processes including growth, reproduction, repair, and movement. While food and nutrients are sources of energy, it is the energy derived from them (mainly ATP) that powers cellular activities.

(c) Starch

Explanation:

Amylolytic enzymes like amylase break down starch (a polysaccharide) into simpler sugars such as maltose and glucose. This process begins in the mouth with salivary amylase.

(c) Green Plants

Explanation:

Autophytes and holophytes refer to self-nourishing plants (auto = self). Green plants perform photosynthesis using sunlight, water, and carbon dioxide to produce food, hence they are called autophytes or holophytes.

(c) Autophytes

Explanation:

Chemosynthetic bacteria produce their own food using chemical reactions (not sunlight), making them a type of autotroph. They oxidize inorganic substances like ammonia or hydrogen sulfide to generate energy for food synthesis.

(b) Saprophytes

Explanation:

Saprophytic plants feed on dead and decaying organic matter. They release digestive enzymes into their surroundings and absorb the resulting nutrients, helping in decomposition.

(a) Parasite

Explanation:

A parasite derives its nourishment from another organism (host), often harming it. It lives either inside or on the surface of the host and depends on it for survival.

(c) Host

Explanation:

Parasites cannot make their own food. They depend on a host organism for nutrients, often causing it harm over time. Examples include lice on humans or tapeworms in intestines.

(c) Symbiosis

Explanation:

Symbiosis is a close relationship between two organisms where they share resources. In mutualism (a type of symbiosis), both partners benefit. In parasitism, one benefits while harming the other.

(a) Holozoic

Explanation:

Animals follow holozoic nutrition, in which they ingest complex food and break it down internally through digestion. This includes humans, dogs, lions, and many other animals.

mouth.

Explanation:

The process of digestion starts in the mouth, where food is broken down mechanically by teeth and chemically by the enzyme ptyalin (salivary amylase) which acts on starch.

host

Explanation:

A host is an organism that provides nutrients and shelter to a parasite, often getting harmed in return.

pharynx.

Explanation:

In earthworms, the pharynx is a muscular organ that helps in sucking soil containing food particles into the alimentary canal.

hydrochloric acid (HCl).

Explanation:

The gastric glands in the stomach lining secrete HCl, which kills harmful microbes and helps in protein digestion by activating pepsinogen into pepsin.

Liver

Explanation:

The liver is the largest internal gland of the human body, reddish-brown in colour, and plays a key role in metabolism, digestion, and detoxification.

True

Explanation:

Ptyalin (salivary amylase) functions only in the mouth, as it is inactivated by the acidic pH in the stomach.

True

Explanation:

Holozoic nutrition involves ingestion, digestion, absorption, and assimilation of food, which is followed by organisms like humans and dogs.

False

Explanation:

Pancreatic juice is released into the small intestine (duodenum), not the stomach. It helps in digestion of proteins, fats, and carbohydrates.

True

Explanation:

The stomach acts as a storage tank and performs mechanical and chemical digestion by churning food and mixing it with gastric juices.

True

Explanation:

Excess intake of alcohol and fatty foods can damage liver cells over time, leading to cirrhosis, a serious liver condition.

Parasites

Explanation:

All others (saprophytes, autophytes, symbionts) are involved in non-harmful or mutual nutrition, while parasites harm their host.

Saprozoic nutrition

Explanation:

Ingestion, digestion, and absorption are phases of nutrition, but saprozoic nutrition is a mode of nutrition, hence different.

Pepsin

Explanation:

Pepsin is a protein-digesting enzyme, while the others are carbohydrate-digesting.

Amino acid

Explanation:

Amino acid is a protein unit, while the others are monosaccharide sugars (carbohydrates).

Ptyalin is a salivary amylase enzyme that breaks down starch into maltose in the mouth.

Amylolytic enzymes are enzymes that break down starch into simpler sugars, such as amylase.

Autotrophic plants like green plants synthesize their own food using sunlight, CO₂, and water.

Cuscuta draws nourishment from host plants and is known as a parasitic plant.

Such organisms are known as saprophytes or saprotrophs.

It is known as Lichen — a symbiotic relationship.

Holophytes is the other name of autophytes.

Because nutrition involves biochemical reactions like digestion, absorption, and assimilation, which lead to the release or use of energy. These changes are part of metabolism, hence nutrition is a metabolic process.

Biological catalysts made of proteins that speed up biochemical reactions in living organisms without being consumed are called enzymes.

Examples: Amylase, Lipase, Pepsin.

Substances in food that provide energy and materials needed for growth, repair, and functioning of the body is called a nutrient.

Example- Carbohydrates, Proteins, Fats, Vitamins, Minerals and Water

Starch-splitting enzyme: Amylase (Salivary amylase or ptyalin)

Fat-digesting enzyme: Lipase

Protein-breaking enzyme: Pepsin and Trypsin

Because vitamins do not provide energy or build body tissues like carbohydrates, proteins, or fats, but help in regulating body functions, they are not considered food.

When the intake of nutrients is lower than the body’s requirement, leading to poor health and stunted growth is called undernutrition.

A type of symbiotic relationship where both organisms involved benefit from each other is called mutualism.

The close and long-term association between two different organisms, where at least one benefits, is called symbiosis.

The enzyme secreted by the salivary gland is ptyalin (also known as salivary amylase).

The salivary gland works mainly on starchy foods like rice, bread, potatoes, and chapati. It secretes an enzyme called ptyalin (salivary amylase) which begins the digestion of starch by breaking it down into simpler sugars like maltose. This process starts in the mouth as soon as food is chewed.

Nutrition is the process by which living organisms obtain and utilize food for energy, growth, and maintenance of body functions.

Nutrients are the components of food that are essential for the body to perform various life processes. These include carbohydrates, proteins, fats, vitamins, minerals, water, and dietary fiber.

Types of nutrients:

1. Macronutrients – Macronutrients are the nutrients required by the body in large amounts for providing energy, building and repairing tissues, and maintaining body functions. e.g. Carbohydrates, Proteins, Fats, Water
2. Micronutrients – Micronutrients are the nutrients required by the body in very small quantities, but they play a crucial role in regulating body processes, enzyme functioning, immunity, and overall health. e.g. Vitamins and Minerals

Explanation:

All foods are considered nutrients because they supply one or more nutrients required by the body. But all nutrients (like vitamins or minerals) may not be considered “food” as they do not provide energy or bulk on their own.

Plants show different modes of nutrition based on how they obtain food and nutrients from their environment. The main types of plant nutrition are:

1. Autotrophic Nutrition: Plants that can prepare their own food using sunlight, carbon dioxide, water, and chlorophyll through the process of photosynthesis show autotrophic nutrition.
2. Parasitic Nutrition: Some plants depend on other living plants (hosts) for water and nutrients. They have special structures called haustoria to absorb food from the host.
3. Insectivorous Nutrition: Some green plants trap and digest insects to obtain nitrogen and other nutrients because they grow in nitrogen-deficient soil.
4. Saprophytic Nutrition: Plants that feed on dead and decaying organic matter are saprophytes. These plants secrete enzymes to break down complex substances into simpler ones for absorption.
5. Symbiotic Nutrition: In this mode, two different organisms live together and help each other in nutrition. One may supply food while the other provides water or shelter.

Nutrition is the biological process by which organisms take in food and utilize it for energy, growth, and repair.

Different phases of nutrition in animals:

1. Ingestion: Ingestion is the process by which an organism takes in food or nutrients from the external environment.
2. Digestion: Breaking down complex food into simpler, absorbable forms using enzymes.
3. Absorption: Absorption is the process by which digested food is transported from the intestines into the bloodstream.
4. Assimilation: Assimilation is the process by which the absorbed nutrients are used by the body for various essential functions such as energy production, growth, and cell repair.
5. Egestion: Egestion is the process of eliminating undigested and unabsorbed food from the body. This occurs primarily through the rectum and anus as feces.

The stomach plays a vital role in the digestive system by acting as a muscular, hollow organ that temporarily stores food and starts the digestion of proteins.

(i) Mechanical Digestion: The stomach muscles churn and mix the food with digestive juices, turning it into a semi-liquid paste called chyme.

(ii) Chemical Digestion: The gastric glands in the stomach wall secrete gastric juice, which contains:

• Hydrochloric acid (HCl) – makes the medium acidic, kills germs, and helps enzymes work.
• Pepsin – a digestive enzyme that starts breaking down proteins into smaller peptides.
• Mucus – protects the inner lining of the stomach from acid.

(iii) Food Storage: The stomach stores food for a few hours, releasing it gradually into the small intestine for further digestion and absorption.

Metabolism is the sum total of all the chemical reactions that take place in a living organism to maintain life. These reactions help in converting food into energy, building up body structures, and removing waste products. It includes both the breakdown of complex substances and the synthesis of new ones to keep the body functioning properly.

Metabolism is divided into two main types:

1. Catabolism: Catabolism is the process where complex molecules are broken down into simpler ones, releasing energy. Catabolism provides the energy required for all cellular activities.
2. Anabolism: Anabolism is the process of building up complex molecules from simpler ones. It requires energy. Anabolism helps in growth, healing, and storage of energy.

Metabolism = Catabolism (breakdown, energy release) + Anabolism (building up, energy use)