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Human Physiology: An Integrated Approach 5th Ed. - Ch. 4

Biological Sciences
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Chapter 4 Notes
Energy = essential for biological processes to maintain life
ow/o E, cells would not be able to:
be repaired
and be maintained
Energy in Biological Systems
living organisms must use energy in order for their cells to grow, make new
parts, and reproduce
oplants trap E from the sun through the process of photosynthesis and
stores it in chemical-bonds
they also get essential molecules from CO2, the soil, and water to
make biomolecules like glucose and AAs
oAnimals must INGEST the biomolecules of plants or other animals in
order to import chemical-bond E so, in actuality, all animals
ultimately get their E from the sun that was trapped by photosynthesis
Animals EXTRACT the E contained in biomolecules through the
process of respiration, which consumes O2 and produces CO2 and
Excess E is stored in chemical bonds mainly in glycogen
(glucose polymer) and lipid molecules (in animals)
Concept Check
1.Amino acids and nucleic acids always include nitrogen in their chemical
Energy is used to perform work
Energy: the capacity to do work
owork (in biological systems) means one of three specific things:
chemical work

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the making and breaking of chemical bonds
allows cells and organisms to grow, maintain an
appropriate internal environment, and store info needed
for reproduction and other activities
transport work
enables cells to move ions, molecules, and larger particles
through the cell membrane and membranes of organelles
in the cell
useful for creating concentration gradients when
therere more molecules on one side of a membrane than
there are on the other side
mechanical work
used for movement (in animals)
@ the microscopic level, movement can include organelles
moving around inside of a cell & flagella and cilia beating
@ the macroscopic level, movement usually involves
muscle contraction
most mechanical work is brought about by motor proteins
that make up certain IC fibres and filaments of the
oAll organisms obtain, store, and use E to fuel their activities
Energy comes in two forms: kinetic and potential
All types of E are able to appear in 2 forms:
oKinetic E: the E of motion
oPotential E: stored E
o All types of E have the ability of PE to become KE and vice versa
Energy can be converted from one form to another

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when potential E is converted into kinetic E, the conversion is never 100%
efficient, and some E is usually lost to the environment as heat amt of heat
lost depends on the processs efficiency
many physiological processes in the human body are NOT very efficient
in biological systems, PE is stored in concentration gradients and chemical
othis E is converted into KE when needed to do chemical, transport, or
mechanical work
Thermodynamics is the study of energy use
2 rules concerning the transfer of E in the universe:
ofirst law of thermodynamics aka law of conservation of energy:
states that the TOTAL AMT OF E in the universe is CONST
the universe is a closed system nothing enters and
nothing leaves
the human body is NOT a closed system; it imports E via
food and loses E to the environment in the form of
(usually) heat; E within the body can be converted into
other forms or can be used to do work
osecond law of thermodynamics:
states that natural spontaneous processes move from a state of
order (nonrandomness) to a condition of disorder
(randomness) entropy
creating and maintaining order reqs E
disorder occurs through the loss of E w/o regaining the E
Concept Check
2.chemical bonds and concentration gradients
3.potential E is stored E which has the ability to be converted to kinetic E; KE
is the energy that is associated w/ motion
4.entropy is the state of randomness of a process; as randomness (disorder)
increases, so too does entropy
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