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The energy from ATP drives all bodily functions, such as contracting muscles, maintaining the electrical potential of nerve cells, and absorbing food in the gastrointestinal tract. The metabolic reactions that produce ATP come from various sources ( [link] ).

Sources of atp

This flowchart shows how food is modified into lipids, carbohydrates, and protein, and the various catabolic reactions which convert food into energy.
During catabolic reactions, proteins are broken down into amino acids, lipids are broken down into fatty acids, and polysaccharides are broken down into monosaccharides. These building blocks are then used for the synthesis of molecules in anabolic reactions.

Of the four major macromolecular groups (carbohydrates, lipids, proteins, and nucleic acids) that are processed by digestion, carbohydrates are considered the most common source of energy to fuel the body. They take the form of either complex carbohydrates, polysaccharides like starch and glycogen, or simple sugars (monosaccharides) like glucose and fructose. Sugar catabolism breaks polysaccharides down into their individual monosaccharides. Among the monosaccharides, glucose is the most common fuel for ATP production in cells, and as such, there are a number of endocrine control mechanisms to regulate glucose concentration in the bloodstream. Excess glucose is either stored as an energy reserve in the liver and skeletal muscles as the complex polymer glycogen, or it is converted into fat (triglyceride) in adipose cells (adipocytes).

Among the lipids (fats), triglycerides are most often used for energy via a metabolic process called β-oxidation. About one-half of excess fat is stored in adipocytes that accumulate in the subcutaneous tissue under the skin, whereas the rest is stored in adipocytes in other tissues and organs.

Proteins, which are polymers, can be broken down into their monomers, individual amino acids. Amino acids can be used as building blocks of new proteins or broken down further for the production of ATP. When one is chronically starving, this use of amino acids for energy production can lead to a wasting away of the body, as more and more proteins are broken down.

Nucleic acids are present in most of the foods you eat. During digestion, nucleic acids including DNA and various RNAs are broken down into their constituent nucleotides. These nucleotides are readily absorbed and transported throughout the body to be used by individual cells during nucleic acid metabolism.

Anabolic reactions

In contrast to catabolic reactions, anabolic reactions    involve the joining of smaller molecules into larger ones. Anabolic reactions combine monosaccharides to form polysaccharides, fatty acids to form triglycerides, amino acids to form proteins, and nucleotides to form nucleic acids. These processes require energy in the form of ATP molecules generated by catabolic reactions. Anabolic reactions, also called biosynthesis reactions    , create new molecules that form new cells and tissues, and revitalize organs.

Hormonal regulation of metabolism

Catabolic and anabolic hormones in the body help regulate metabolic processes. Catabolic hormones stimulate the breakdown of molecules and the production of energy. These include cortisol, glucagon, adrenaline/epinephrine, and cytokines. All of these hormones are mobilized at specific times to meet the needs of the body. Anabolic hormones are required for the synthesis of molecules and include growth hormone, insulin-like growth factor, insulin, testosterone, and estrogen. [link] summarizes the function of each of the catabolic hormones and [link] summarizes the functions of the anabolic hormones.

Questions & Answers

how can you remember the integumentary system
Naomi Reply
integumentary system is the skin the skin is protection all the body and contain deid cells
Drs
how can you remember the formation of bone?
Maame
the largest organ of the body
Toni
skin is largest organ
Zara
what is the best way to remember the cranial bones or any other bones ?
Savannah
skeletal system?
Savannah
look at the diagram structure and then remember it considering it your own body i memorise like that
Zara
hi guys! do you have to remember ALL the structures of the bones- I mean every single hole, depression or tuberosity?
Kristina
tuborisity
Zara
hey guz i hv to remember Immune antibodies and antigens how? i found it difficult
Zara
well, they are all grouped, aren't they? I mean they all come in series like H1, H2A, H2B and so on. In this case I learn the common part first and then that what's different
Kristina
nd what about IgG , IgE etc.
Zara
the majors
Toni
blood is a connective tissue which transport oxygen and other nutrients to body
Zara Reply
which type of protein is blood?
Zara
what is blood?
Masthan Reply
blood is a connective tissue which transport oxygen and nutrients to body
Zara
which type of protein is blood?
Zara
haemoglobin
Rashid
and what about its structure i think its Quartenary structure 🤔💭
Zara
yes it is
Rashid
it is globular
Rashid
a vascular structure compose of vessels.
Toni
what is the functions of lymph
moula Reply
what is plasma
Chukwu Reply
A plasma is a hot ionized gas consisting of approximately af a equal number of positive ly charged ionized and negative ly charged electron is called plasma.
Muhammad
what is an atomical position?
Madinatu
military position, body erect where by the body will be up straight..the cephalic and thoracic are straight
Mwita
functions of plasma membrane
Dinyando Reply
what is heparin
Lawrence Reply
why is it anatomy
Tenacious Reply
hello
ASIMENU
hi
asare
hws life
Tenacious
anatomy is the scientific study of the body's structure
Lawrence
great
Lawrence
good night
Kaaya
anatomy is the study of form, physiology is the study of function
Patrick
anatomy is the study of the structure of the body and the physical relationship between it constituent part
Florence
what is heparin
Lawrence
what is the trunk
Tenacious
trunk is define as a person's or animal's body apart from the limp and head
Lawrence
The trunk is part of the axial skeleton
Patrick
hellow friends
mickson
hi friends
mickson
Hi
REEMA
hii
sampath
hi
Inayat
am fine
Ematai
supine or dorsal position is used in clinical setting when patient is placed in position, to examine what?
Dinyando Reply
what do nurses/doctors detect when a patient is placed on dorsal position?
Dinyando
What is coroid process?
kelvin Reply
describe special situation with implications in medical ethics.
kelvin
what is the difference between anatomy and physiology
Dinyando Reply
anatomy is the study of human body . and physiology is the study of the brain
Maryiam
ok
Varun
hi friends
Varun
hi!
kelvin
hello
Maryiam
anatomy is the study of the human body,its form and it physical relations Whiles Physiology is the Study of the functions of the various part of the body
Madinatu
yes
Yeboah
hi friends
mickson
sorry I cant see the full question
Jessica Reply
what was the question?
evelyna
what is spine as a bone marking?
John
similar to a crest but raised more
evelyna
pointed process
evelyna
slender
evelyna
pointed projection i meant
evelyna
what fills the hallow space in the middle of bones? thanks
John
marrow
evelyna
bone marrow
evelyna
hey you gotta read a book
evelyna
i just happen to take this bone chapter in my book last week so i remember
evelyna
yeah i should. how about the correct match of the number of tarsal, metatarsal and phalanges?
John
10, fingers and toes, u know this
Patrick
what is the difference between basal laminal and basal membrane
Nartey Reply
I think they r the same
Patrick
If one is missing the opsin which detects wavelengths of approximately 560 nm what color would they be unable to see?
Alicia Reply
how do I explain into details the epithelial tissue
Sir Reply
Epithelial tissues line the outer surfaces of organs and blood vessels throughout the body, as well as the inner surfaces of cavities in many internal organs. An example is the epidermis, the outermost layer of the skin. There are three principal shapes of epithelialcell: squamous, columnar, and cub
DJ
thank you
Sir
explain how the intestinal irritation results in diarrhoea
Sir
elasticity of the vagina
Mariam Reply

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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