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Temperature

Nearly all chemical reactions occur at a faster rate at higher temperatures. Recall that kinetic energy is the energy of matter in motion. The kinetic energy of subatomic particles increases in response to increases in thermal energy. The higher the temperature, the faster the particles move, and the more likely they are to come in contact and react.

Concentration and pressure

If just a few people are dancing at a club, they are unlikely to step on each other’s toes. But as more and more people get up to dance—especially if the music is fast—collisions are likely to occur. It is the same with chemical reactions: the more particles present within a given space, the more likely those particles are to bump into one another. This means that chemists can speed up chemical reactions not only by increasing the concentration    of particles—the number of particles in the space—but also by decreasing the volume of the space, which would correspondingly increase the pressure. If there were 100 dancers in that club, and the manager abruptly moved the party to a room half the size, the concentration of the dancers would double in the new space, and the likelihood of collisions would increase accordingly.

Enzymes and other catalysts

For two chemicals in nature to react with each other they first have to come into contact, and this occurs through random collisions. Because heat helps increase the kinetic energy of atoms, ions, and molecules, it promotes their collision. But in the body, extremely high heat—such as a very high fever—can damage body cells and be life-threatening. On the other hand, normal body temperature is not high enough to promote the chemical reactions that sustain life. That is where catalysts come in.

In chemistry, a catalyst    is a substance that increases the rate of a chemical reaction without itself undergoing any change. You can think of a catalyst as a chemical change agent. They help increase the rate and force at which atoms, ions, and molecules collide, thereby increasing the probability that their valence shell electrons will interact.

The most important catalysts in the human body are enzymes. An enzyme    is a catalyst composed of protein or ribonucleic acid (RNA), both of which will be discussed later in this chapter. Like all catalysts, enzymes work by lowering the level of energy that needs to be invested in a chemical reaction. A chemical reaction’s activation energy    is the “threshold” level of energy needed to break the bonds in the reactants. Once those bonds are broken, new arrangements can form. Without an enzyme to act as a catalyst, a much larger investment of energy is needed to ignite a chemical reaction ( [link] ).

Enzymes

The left panel shows a graph of energy versus progress of reaction in the absence of enzymes. The right panel shows the graph in the presence of enzymes.
Enzymes decrease the activation energy required for a given chemical reaction to occur. (a) Without an enzyme, the energy input needed for a reaction to begin is high. (b) With the help of an enzyme, less energy is needed for a reaction to begin.

Enzymes are critical to the body’s healthy functioning. They assist, for example, with the breakdown of food and its conversion to energy. In fact, most of the chemical reactions in the body are facilitated by enzymes.

Chapter review

Chemical reactions, in which chemical bonds are broken and formed, require an initial investment of energy. Kinetic energy, the energy of matter in motion, fuels the collisions of atoms, ions, and molecules that are necessary if their old bonds are to break and new ones to form. All molecules store potential energy, which is released when their bonds are broken.

Four forms of energy essential to human functioning are: chemical energy, which is stored and released as chemical bonds are formed and broken; mechanical energy, which directly powers physical activity; radiant energy, emitted as waves such as in sunlight; and electrical energy, the power of moving electrons.

Chemical reactions begin with reactants and end with products. Synthesis reactions bond reactants together, a process that requires energy, whereas decomposition reactions break the bonds within a reactant and thereby release energy. In exchange reactions, bonds are both broken and formed, and energy is exchanged.

The rate at which chemical reactions occur is influenced by several properties of the reactants: temperature, concentration and pressure, and the presence or absence of a catalyst. An enzyme is a catalytic protein that speeds up chemical reactions in the human body.

Questions & Answers

elasticity of the vagina
Mariam Reply
The vagina is an elastic muscular wall
antouman
*organ
antouman
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

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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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