Metabolism

<–2/”>a >Metabolism is the set of life-sustaining chemical transformations within the cells of organisms. The three main purposes of metabolism are the conversion of food/fuel to energy to run cellular processes, the conversion of food/fuel to building blocks for proteins, lipids, nucleic acids, and some Carbohydrates, and the elimination of nitrogenous wastes. These enzyme-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. The word metabolism can also refer to the sum of all chemical reactions that occur in living organisms, including digestion and the transport of substances into and between different cells, in which case the set of reactions within the cells is called intermediary metabolism or intermediate metabolism.

Digestive System

Introduction

The respiratory and circulatory systems work together to provide cells with the Oxygen they need for cellular Respiration.
Cells also need glucose for cellular respiration. Glucose is a simple sugar that comes from the food we eat.
To get glucose from food, digestion must occur. This process is carried out by the digestive system.

Overview of the Digestive System

The digestive system consists of organs that break down food and absorb nutrients such as glucose.
Organs of the digestive system are shown in Figure below. Most of the organs make up the gastrointestinal tract. The rest of the organs are called accessory organs

The Gastrointestinal Tract

The gastrointestinal (GI) tract is a long tube that connects the mouth with the anus. It is more than 9 meters (30 feet) long in adults and includes the esophagus, stomach, and small and large intestines.
Food enters the mouth, passes through the other organs of the GI tract, and then leaves the body through the anus.
The organs of the GI tract are lined with mucous membranes that secrete digestive ENZYMES and absorb nutrients.
The organs are also covered by layers of muscle that enable peristalsis.
Peristalsis is an involuntary muscle contraction that moves rapidly along an organ like a wave (see Figure below).

Accessory Organs of Digestion

Other organs involved in digestion include the liver, gall bladder, and pancreas.
They are called accessory organs because food does not pass through them. Instead, they secrete or store substances needed for digestion.

Functions of the Digestive System

The digestive system has three main functions: digestion of food, absorption of nutrients, and elimination of solid food waste. Digestion is the process of breaking down food into components the body can absorb.
It consists of two types of processes: mechanical digestion and chemical digestion.

Mechanical digestion is the physical breakdown of chunks of food into smaller pieces. This type of digestion takes place mainly in the mouth and stomach.
Chemical digestion is the chemical breakdown of large, complex food Molecules into smaller, simpler nutrient molecules that can be absorbed by the blood. This type of digestion begins in the mouth and stomach but occurs mainly in the small intestine.

After food is digested, the resulting nutrients are absorbed. Absorption is the process in which substances pass into the bloodstream, where they can circulate throughout the body.
Absorption of nutrients occurs mainly in the small intestine. Any remaining matter from food that cannot be digested and absorbed passes into the large intestine as waste. The waste later passes out of the body through the anus in the process of elimination.

The Start of Digestion: Mouth to Stomach

Mouth

The mouth is the first digestive organ that food enters. The sight, smell, or taste of food stimulates the release of digestive enzymes by salivary glands inside the mouth.
The major salivary enzyme is amylase. It begins the chemical digestion of carbohydrates by breaking down starch into sugar.
The mouth also begins the process of mechanical digestion. Sharp teeth in the front of the mouth cut or tear food when you bite into it. Broad teeth in the back of the mouth grind food when you chew.
Food is easier to chew because it is moistened by saliva from the salivary glands. The tongue helps mix the food with saliva and also helps you swallow. After you swallow, the chewed food passes into the pharynx

Esophagus

From the pharynx, the food moves into the esophagus. The esophagus is a long, narrow tube that passes food from the pharynx to the stomach by peristalsis.
The esophagus has no other digestive functions. At the end of the esophagus, a muscle called a sphincter controls the entrance to the stomach.
The sphincter opens to let food into the stomach and then closes again to prevent food from passing back into the esophagus.

Stomach

The stomach is a sac-like organ in which food is further digested both mechanically and chemically.
Churning movements of the stomach’s thick, muscular walls complete the mechanical breakdown of food.
The churning movements also mix food with digestive fluids secreted by the stomach. One of these fluids is hydrochloric acid.
It kills bacteria in food and gives the stomach the low pH needed by digestive enzymes that work in the stomach. The main enzyme is pepsin, which chemically digests protein.
The stomach stores the partly digested food until the small intestine is ready to receive it. When the small intestine is empty, a sphincter opens to allow the partially digested food to enter the small intestine.

Digestion and Absorption: The Small Intestine

The small intestine is a narrow tube about 7 meters (23 feet) long in adults. It is the site of most chemical digestion and virtually all absorption.
The small intestine consists of three parts: the duodenum, jejunum, and ileum

Digestion in the Small Intestine

The duodenum is the first and shortest part of the small intestine.
Most chemical digestion takes place here, and many digestive enzymes are active in the duodenum (see Tablebelow). Some are produced by the duodenum itself.
Others are produced by the pancreas and secreted into the duodenum.

Enzyme	What It Digests	Where It Is Made
Amylase	Carbohydrates	pancreas
Trypsin	Proteins	pancreas
Lipase	Lipids	pancreas, duodenum
Maltase	Carbohydrates	duodenum
Peptidase	Proteins	duodenum

The liveris an organ of both digestion and Excretion. It produces a fluid called bile, which is secreted into the duodenum. Some bile also goes to the gall bladder, a sac-like organ that stores and concentrates bile and then secretes it into the small intestine.
In the duodenum, bile breaks up large globules of lipids into smaller globules that are easier for enzymes to break down. Bile also reduces the acidity of food entering from the highly acidic stomach.
This is important because digestive enzymes that work in the duodenum need a neutral Environment. The pancreas contributes to the neutral environment by secreting bicarbonate, a basic substance that neutralizes acid.

Absorption in the Small Intestine

The jejunum is the second part of the small intestine, where most nutrients are absorbed into the blood. The mucous membrane lining the jejunum is covered with millions of microscopic, fingerlike projections called villi (singular, villus).
Villi contain many capillaries, and nutrients pass from the villi into the bloodstream through the capillaries. Because there are so many villi, they greatly increase the surface area for absorption.
The ileum is the third part of the small intestine. A few remaining nutrients are absorbed here. Like the jejunum, the inner surface of the ileum is covered with villi that increase the surface area for absorption.

The Large Intestine and Its Functions

From the small intestine, any remaining food wastes pass into the large intestine.
The large intestine is a relatively wide tube that connects the small intestine with the anus.
Like the small intestine, the large intestine also consists of three parts: the cecum (or caecum), colon, and rectum.

Metabolism is the set of chemical reactions that occur within a living organism to maintain life. These processes allow organisms to grow and develop, reproduce, move, maintain their structures, and respond to their environment.

Metabolism is divided into two main categories: anabolism and catabolism. Anabolism is the process of building up molecules, while catabolism is the process of breaking down molecules.

Anabolism requires energy, which is provided by ATP (adenosine triphosphate). ATP is a molecule that stores energy in its chemical Bonds. When ATP is broken down, it releases energy that can be used to power anabolic reactions.

Catabolism releases energy, which can be used to power anabolic reactions or to provide energy for other cellular processes.

Carbohydrate metabolism is the process of breaking down carbohydrates into glucose, which is then used by the body for energy. Carbohydrates are the body’s main Source Of Energy.

The citric acid cycle, also known as the Krebs cycle, is a series of chemical reactions that occur in the mitochondria of cells. The citric acid cycle is responsible for the production of ATP, NADH, and FADH2.

The electron transport chain is a series of proteins that are located in the inner membrane of mitochondria. The electron transport chain is responsible for the production of ATP.

Glycolysis is a series of chemical reactions that occur in the cytoplasm of cells. Glycolysis is the first step in the breakdown of glucose.

Gluconeogenesis is the process of synthesizing glucose from non-carbohydrate sources, such as lactate, amino acids, and glycerol. Gluconeogenesis is important for maintaining blood glucose levels.

Ketogenesis is the process of producing ketone bodies from fatty acids. Ketone bodies are used as an alternative source of energy when glucose is not available.

Lipid metabolism is the process of breaking down and synthesizing lipids. Lipids are a type of molecule that includes fats, oils, and cholesterol.

Protein metabolism is the process of breaking down and synthesizing proteins. Proteins are essential for the Growth and repair of Tissues.

Starvation metabolism is the process that the body goes through when it does not have enough food to eat. Starvation metabolism is characterized by a decrease in the body’s metabolic rate and an increase in the breakdown of muscle tissue.

Thermogenesis is the process of heat production in the body. Thermogenesis is important for maintaining body temperature.

Metabolism is a complex process that is essential for life. The different metabolic pathways work together to provide the body with the energy it needs to function.

1. What is the difference between a virus and a bacterium?

A virus is a tiny infectious agent that replicates only inside the living cells of other organisms. Viruses can infect all types of life forms, from animals and Plants to bacteria and archaea. Viruses are not considered living because they do not have cells or cell membranes. They are also not able to reproduce on their own. Instead, they must infect a host cell and use the cell’s machinery to replicate themselves.

Bacteria are single-celled organisms that are classified as prokaryotes. This means that they do not have a nucleus or other membrane-bound organelles. Bacteria are found in all environments, including Soil, water, and the human body. Some bacteria are beneficial, while others can cause disease.

2. What is the difference between a gene and a chromosome?

A gene is a unit of heredity that is located on a chromosome. Genes are made up of DNA, which is a molecule that contains the instructions for how an organism develops and functions. Chromosomes are structures in the nucleus of a cell that contain DNA. Humans have 23 pairs of chromosomes, for a total of 46 chromosomes.

3. What is the difference between RNA and DNA?

RNA and DNA are both nucleic acids, which are molecules that contain the instructions for how an organism develops and functions. However, RNA and DNA have different structures. RNA is a single-stranded molecule, while DNA is a double-stranded molecule. RNA also contains the sugar ribose, while DNA contains the sugar deoxyribose.

4. What is the difference between a mutation and a genetic disorder?

A mutation is a change in the DNA sequence of an organism. Mutations can be caused by errors in DNA replication, exposure to radiation or chemicals, or viruses. Most mutations are harmless, but some can cause genetic disorders. Genetic disorders are diseases that are caused by changes in the DNA sequence. Genetic disorders can be inherited from parents or they can be caused by mutations that occur during a person’s lifetime.

5. What is the difference between a cell and an organ?

A cell is the basic unit of life. Cells are tiny, self-contained units that carry out all the functions necessary for life. Organs are groups of tissues that work together to perform a specific function in the body. For example, the heart is an organ that pumps blood throughout the body.

6. What is the difference between a tissue and an organ system?

A tissue is a group of cells that are similar in structure and function. There are four main types of tissues in the human body: epithelial tissue, connective tissue, muscle tissue, and nervous tissue. Organs are groups of tissues that work together to perform a specific function in the body. For example, the heart is an organ that pumps blood throughout the body. Organ systems are groups of organs that work together to perform a complex function in the body. For example, the digestive system is responsible for breaking down food and absorbing nutrients.

7. What is the difference between the nervous system and the Endocrine System?

The nervous system is the body’s Communication system. It sends messages from the brain and spinal cord to all parts of the body. The endocrine system is the body’s hormone-producing system. HORMONES are chemicals that control many of the body’s functions, including growth, metabolism, and Reproduction.

8. What is the difference between the cardiovascular system and the Respiratory System?

The cardiovascular system is the body’s blood-pumping system. It consists of the heart, blood vessels, and blood. The heart pumps blood throughout the body, delivering oxygen and nutrients to the tissues and removing waste products. The respiratory system is the body’s gas-exchange system. It consists of the lungs, airways, and blood vessels. The lungs take in oxygen from the air and deliver it to the blood. The blood then carries the oxygen to the tissues, where it is used for energy production.

9. What is the difference between the digestive system and the Excretory System?

The digestive system is the body’s food-processing system. It consists of the mouth, esophagus, stomach, small intestine, large intestine, and rectum. The digestive system breaks down food into smaller molecules that can be absorbed by the body. The excretory system is the body’s waste-removal system. It consists of the kidneys, bladder, and ureters. The excretory system removes waste products from the blood and eliminates them from the body.

10. What is the difference between the immune system and the lymphatic system?

The immune system is the body’s defense system. It protects the body from infection and disease. The lymphatic system is the body’s fluid-transport system. It

The process by which cells break down food to produce energy is called:
(A) Metabolism
(B) Digestion
(C) Assimilation
(D) Excretion
The three main types of nutrients are:
(A) Carbohydrates, lipids, and proteins
(B) VITAMINS, Minerals, and water
(C) Nucleic acids, carbohydrates, and lipids
(D) Carbohydrates, lipids, and nucleic acids
The main function of carbohydrates is to:
(A) Provide energy
(B) Build and repair tissues
(C) Regulate body functions
(D) Transport nutrients
The main function of lipids is to:
(A) Provide energy
(B) Build and repair tissues
(C) Regulate body functions
(D) Transport nutrients
The main function of proteins is to:
(A) Provide energy
(B) Build and repair tissues
(C) Regulate body functions
(D) Transport nutrients
The main function of vitamins is to:
(A) Provide energy
(B) Build and repair tissues
(C) Regulate body functions
(D) None of the above
The main function of minerals is to:
(A) Provide energy
(B) Build and repair tissues
(C) Regulate body functions
(D) None of the above
The main function of water is to:
(A) Provide energy
(B) Build and repair tissues
(C) Regulate body functions
(D) Transport nutrients
The process by which food is broken down into smaller molecules that can be absorbed by the body is called:
(A) Digestion
(B) Assimilation
(C) Excretion
(D) None of the above
The process by which nutrients are absorbed into the bloodstream is called:
(A) Digestion
(B) Assimilation
(C) Excretion
(D) None of the above
The process by which waste products are removed from the body is called:
(A) Digestion
(B) Assimilation
(C) Excretion
(D) None of the above