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Nutrition: Getting Food to Cells

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on 28 September 2016

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Transcript of Nutrition: Getting Food to Cells

refers to the activities by which living things obtain raw materials from the environment and transport them into their cells. All the elements and compound taken by living things are nutrients.
are the chemical substances that organisms need in order to grow and function properly. Carbohydrates, proteins, fats and vitamins are called
organic nutrients
because they are synthesized within living organisms.
Getting Food to Cells
How do animals survive?
Gas Exchange with Environment
is the exchange of oxygen and carbon dioxide between an organism and its environment. The two major processes of respiration are
external respiration
, which is the exchange of gases between the lungs and the red blood cells, and
internal respiration
, which is the exchange of gases between the red blood cells and cells that make up the various body tissues. The respiratory and circulatory systems exist to ensure adequate supply of oxygen to the tissues and exchange of carbon dioxide with the atmosphere.
Gas Exchange
Arthropods and other mollusks have an open circulatory system, in which the circulatory fluid bathes the organs directly. In these animals, the circulatory fluid is called the
. Contraction of one or more hearts pumps the hemolymph through the circulatory vessels into spaces surrounding the organs. Relaxation of the heart draws hemolymph back in through pores. Body movements help circulate the hemolymph.
Circulation: The Internal Transport System
In a closed circulatory system, blood is confined to a network of vessels where it is circulated to and from the heart. The closed circulatory system of humans and other vertebrates is often called the
cardiovascular system
The hearts of vertebrates contain two or more muscular chambers. The chambers that receive blood entering the heart are called
(sing., atrium). The chambers responsible for pumping blood out of the heart are called
. The number of chambers and the extent to which they are separated from one another differ substantially among groups of vertebrates.
The blood is part of the circulatory system that supplies the body with the nutrients needed to generate energy. Metabolism depends heavily on the circulatory system, since the nutrients from the food and the oxygen from the air will have to reach the cells through the heart, blood, and blood vessels.
Many animals with simple body plans have a digestive compartment with a single opening. This pouch is called the
gastrointestinal cavity
, which functions in digestion as well as in the distribution of nutrients throughout the body.
The structure of a respiratory system depends on the size of the animal and on whether it lives in water or in land. However, it is also influenced by the metabolic demands for gas exchange.

An animal’s body has an amazing ability to survive even in harsh conditions. How does this happen? The cells maintain a biological balance known as

by regulating which substances get in and out of the cell. If homeostasis is disrupted, cells suffer and sometimes die. This process maintains the internal condition so that the cell can work at optimum level.
The circulatory system also helps maintain constant body temperature, and carries cells which help protect the body from disease. All of these functions help the body maintain homeostasis which is essential to survival.
Salt and Water Balance and Waste Removal

Animals are constantly under attacked by pathogens.
are infectious agents that cause disease. Thus, pathogens infect a wide variety of animals, including humans. In response, animals fight back in various ways. Immune cells guard the body fluids of most animals, searching out and destroying foreign cells. Additional responses to infection take many forms, including proteins that punch holes in bacterial membranes or block viruses from entering body cells.
The Immune System:
Defense from Diseases
You have learned that butterflies undergo complete metamorphosis, a complete change of body form. Metamorphosis is one of the many biological processes controlled by hormones. In animals, a
is a molecule secreted into the extracellular fluid, circulates in the body, and communicates messages throughout the body.
How Hormone Govern Body Activities
Your immune system is your body’s main defense against pathogens. It produces cells that recognize, attack, destroy and remember each type of pathogen that enters the body. Your skin is your first line of defense. The mucus, saliva and tears trap pathogens and contain enzymes that kill bacteria. If the pathogens manage to get through and enter the body, other nonspecific defenses will be activated and this process is called
innate immunity
A second defense system, found only in vertebrates, is
acquired immunity,
also known as

adaptive immunity
. Acquired immune responses are activated after innate immune defenses take effect and develop more slowly. Closely related to the immune system is our body’s lymphatic system. The lymphatic system consists of capillaries, vessels, lymph nodes, and other organs such as thymus. spleen, and tonsils. They transport the fluid called
from the body tissues and return it to the blood.
Chemical signalling using hormones is the function of the endocrine system, one of the two basic system for communication and regulation throughout the body. Hormones secreted by endocrine cells regulate reproduction, development, metabolism, growth, and behaviour. The other major system is the nervous system, a network specialized cells called
that transmit signals along pathways.
Endocrine glands often affect many other organs at one time. For examples, your adrenal glands prepare your organs to deal with stress. They make the hormones
. Epinephrine speeds up your heartbeat and breathing rate to prepare your body either to run from danger or to fight for survival. This hormonal effect is often referred to as the
“fight or flight”
Metabolic Processes Among Living Things
The various organ systems of animals and humans perform chemical activities that involve energy.
is the entirety of all the chemical activities that an organism performs. In metabolism, energy is usually consumed when complex molecules are built, and released when complex molecules are broken down.

A cell’s metabolism involves thousands of reactions occur in a cell. These reactions are arranged as intersecting
metabolic pathways.
A metabolic pathway begins with a specific molecule, which is altered in a series of steps resulting to the production of a certain product. These degradative processes are called
catabolic pathways
or breakdown pathways.
A major pathway of catabolism is
cellular respiration
in which the sugar, glucose, and other organic fuels are broken down in the presence of oxygen and produce carbon dioxide and water.
By contrast,
anabolic pathways
occur when complex molecules are built using energy. The complex molecules are used by the body for all its activities. It includes the synthesis of compounds such as DNA, RNA and proteins.
, energy is obtained from the breakdown of larger molecules into smaller ones. In this process, energy is released. Hydrolysis is an example of a catabolic reaction in which a compund reacts with water. In
, energy is required to build larger molecules. This is necessary for cellular growth and repair.
Nervous System
Metabolism is governed by both the hormones and the nervous system. They work together like a team, complementing every single cellular action in the body. An animal’s nervous system consists of neurons, which are nerve cells that transfer information within the body.
They transmit sensory information, control heart rate, coordinate hand and eye movements, record memories, and more. In more complex animals, the higher-order processing is carried out largely in groups of neurons organized into a brain or into simpler cluster called

The brain and the spinal cord are the nervous system’s control center. The brain is constantly receiving, analysing, and storing information about conditions in both inside and outside of the body.
The Body in Motion

Animals have diverse forms of movement such as flying, swimming ,eating, and crawling. All these require muscle activity in response to nervous system input.
Vertebrate skeletal muscle, which is attached to the bones, is responsible for the animal’s movement. Most skeletal muscle consists of a bundle of long fibres running parallel to the length of the muscle. Skeletal muscles are also called

striated muscles
because the regular arrangement of the filaments creates a pattern of light and dark bands.
You have
more than 600 muscles
in your body working to keep you alive. The muscles of your heart contract to pump blood throughout your body. Your chest muscles work to help air move in and out of the lungs. The nutrients from the food that you have eaten are still being moved through your body by your muscles.

Water balance depends on the regulation of solute movement between internal fluids and the external environment. Animals across wide range species produce a fluid waste called

When the body breaks down excess amino acids, other metabolic wastes, especially nitrogen compounds in the form of ammonia, is released. The body is able to make ammonia by combining it with carbon dioxide in the liver to form a less toxic compound called
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