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By the end of this section, you will be able to:
  • Distinguish between kinetic and potential energy, and between exergonic and endergonic chemical reactions
  • Identify four forms of energy important in human functioning
  • Describe the three basic types of chemical reactions
  • Identify several factors influencing the rate of chemical reactions

One characteristic of a living organism is metabolism, which is the sum total of all of the chemical reactions that go on to maintain that organism’s health and life. The bonding processes you have learned thus far are anabolic chemical reactions; that is, they form larger molecules from smaller molecules or atoms. But recall that metabolism can proceed in another direction: in catabolic chemical reactions, bonds between components of larger molecules break, releasing smaller molecules or atoms. Both types of reaction involve exchanges not only of matter, but of energy.

The role of energy in chemical reactions

Chemical reactions require a sufficient amount of energy to cause the matter to collide with enough precision and force that old chemical bonds can be broken and new ones formed. In general, kinetic energy    is the form of energy powering any type of matter in motion. Imagine you are building a brick wall. The energy it takes to lift and place one brick atop another is kinetic energy—the energy matter possesses because of its motion. Once the wall is in place, it stores potential energy. Potential energy is the energy of position, or the energy matter possesses because of the positioning or structure of its components. If the brick wall collapses, the stored potential energy is released as kinetic energy as the bricks fall.

In the human body, potential energy is stored in the bonds between atoms and molecules. Chemical energy is the form of potential energy in which energy is stored in chemical bonds. When those bonds are formed, chemical energy is invested, and when they break, chemical energy is released. Notice that chemical energy, like all energy, is neither created nor destroyed; rather, it is converted from one form to another. When you eat an energy bar before heading out the door for a hike, the honey, nuts, and other foods the bar contains are broken down and rearranged by your body into molecules that your muscle cells convert to kinetic energy.

Chemical reactions that release more energy than they absorb are characterized as exergonic. The catabolism of the foods in your energy bar is an example. Some of the chemical energy stored in the bar is absorbed into molecules your body uses for fuel, but some of it is released—for example, as heat. In contrast, chemical reactions that absorb more energy than they release are endergonic. These reactions require energy input, and the resulting molecule stores not only the chemical energy in the original components, but also the energy that fueled the reaction. Because energy is neither created nor destroyed, where does the energy needed for endergonic reactions come from? In many cases, it comes from exergonic reactions.

Questions & Answers

what it mean to augment?
Solomon Reply
Which of the following is generally called a Sprain?
Raneem Reply
sprain is also called torn ligament.. it is the streching Or tearing of ligament.. with in a joint
Khawaja
a long boin between your nick and pelvic
Marie
sprain is also known as" moch"
Sneha
sprain is also known as 'moch' it's a type of injury affect on ligaments..(sprain)
Sanjith
sprain and strain both called as 'moch'
Sanjith
moc
Mulumbwe
body, muscle and regional of structures in the body
Harmony Reply
when the heart beats, blood pumps through the body and making the body function
Harmony
what is vagina
Hausa Reply
what is ventricular circulation
Maryam Reply
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In a four-chambered heart, such as that in humans, there are two ventricles that operate in a double circulatory system: the right ventricle pumps blood into the pulmonary circulation to the lungs, and the left ventricle pumps blood into the systemic circulation through the aorta.
yes
anjali
hi
A 23-year-old basketball player mentally rehearses free throw shots while lying in bed. Which option best describesthe area of the brain that is involved in generating a motor image of this action in the absence of actual movement?
Rai
hapothalamus
Prashant
a 67-year-old man has a stroke. one week later, he experiences sudden and uncontrolled flailing, ballistic movements of his limbs. which part of the man’s brain is most likely to have been damaged by the stroke?
Rai
primary motor cortex.. (principal area of cerebrum)
Khawaja
what factors that affect the rate diffusion
Gift Reply
the mass of the solute the temperature of theenvironment the solvent density and the distance traveled
Sulaiman
ok.
Thobok
sorry what are the common meaning of haemostatis
Juma Reply
homeostasis is the steady internal physical and chemical conditions maintaining by living systems
Sulaiman
what are the negatives feedback regulation of ADH
Nansi Reply
what is the the differences between DNA and RNA?
Mustapha
The major differences between the DNA and RNA are contain of double stranded and single stranded which the DNA contain duoble stranded and RNA contain single stranded.
Juma
what are the negatives feedback regulation of ADH before this we confused just verify long term of ADH firstly
Juma
How many genes consist of DNA?
Omaryare
omaryare muhyadiin when you talk about genes, is the material formed in a DNA genes have form like plasma have many genes round there
Juma
aldosterone, renin
Conan
DNA contains the sugar deoxyribone while RNA contains the sugar ribose the only difference between ribose and deoxyribone is that ribose has one more- OH group than deoxyribone which has -H attached to the second carbon in the ring DNA is a double stranded molecules RNA is a single strnded molecul
Sulaiman
yes
Thobok
in human genes very in size from a few hundred DNA based to more than 2million bases
Sulaiman
to know the different structures of the body To know how the body works To know more about our body parts
Deitdre Reply
hi Deitdre you tock about knowledge or you ask the question
Juma
do you need any explanation when reading this book?
janet Reply
Its Good
Hashir
yes
Balogun
Yes
Mariam
yes
Sale
yes
Mustapha
if have many ability just do it!!
Juma
we all waiting for it
Sulaiman
compare and contrast the operation of homeostasis
Dinelle Reply
what is the difference between an ionic, polar covalent and nonpolar covalent bond?
Dinelle
In summary, the bond has different in electronegativity.
Balogun
sorry help me to get the definition of hemostasis or the meaning
Juma
the definition of distal
Dinelle Reply
farthest away from the attachment point.
felix
Distal, is the farthest possition from the origin or midle point
Juma
exercise physiologist how ?
Noor Reply
hi noorr. when you talk about physiologist its a person who study physiology but exercise physiologist is what an exercise doing by physiologist in physiologican
Juma
can I get the questions of human physiology that is present in HSC 2nd semester
Rafiullah Reply
in my lerning the question com like for example ni eassy qustion must understand the the part of the body and how it work or mechanisms of each part learned
Juma
how can I memorize
mukhtaar Reply
which part of the body produces blood
aadil
give me answer
aadil
Red blood cells are formed in the red bone marrow ofbones. Stem cells in the red bone marrow called hemocytoblasts give rise to all of the formed element
mukhtaar
what is hemocytoblasts
Fatima
hemocytoblasts are stem cells in red bone marrow which give rise the all of formed elements
Khawaja

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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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