Marked grade A biology A level essay-the importance of ATP in living organisms.
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Biology
Unit 1 BIOL1 - Biology and disease
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The importance of ATP:
One way that ATP is important in organisms is in muscle contraction in
the body. When calcium ions are released (from the sarcoplasmic
reticulum due to depolarisation of the sarcolemma) and bind to troponin
on tropomyosin causing tropomyosin to undergo a conformational
change in shape, tropomyosin no longer blocks the actin-myosin binding
site on the actin filament. The myosin head can then form cross bridges
with the actin-myosin binding site on actin. Calcium ions activate ATP
hydrolase, which hydrolyses ATP into ADP +Pi. The energy provided here
by the hydrolysis of ATP allows the myosin head to cock back, causing the
actin filament to slide and the muscle to contract.
The hydrolysis of ATP also provides energy for the actin-myosin cross
bridges to break. This allows the myosin head to bind to another actin
myosin binding site further along the actin molecule so muscle
contraction can reoccur. The role of ATP is important here as without the
energy provided by ATP hydrolysis no muscle contraction would occur, as
the myosin head wouldn’t be able to cock back. ATP is also needed for the
active transport of calcium ions from the binding sites back into the
sarcoplasmic reticulum. If calcium ions were not actively transported
back the muscle would remain contracted as tropomyosin wouldn’t be
blocking the actin-myosin binding sites anymore and the myosin head
would continue to be attatched to the actin-myosin binding sites.
Another reason that ATP is important in the body is in the cell cycle,
specifically mitosis. During interphase the organelles replicate and so
does DNA as its unravelled, ATP content also replicates as ATP hydrolysis
provides the energy for cell division to occur. For example during
prophase chromosomes become shorter and fatter and centrioles move to
opposite poles of the cell, spindle fibres then form, the nuclear envelope
also breaks down so chromosomes lie freely in the cytoplasm. During
metaphase these chromosomes attatch by their centromere to the
spindle fibres, and during anaphase these spindle fibres contract so that
chromatids are separated and are at opposite poles of the cell. During
teleophase these chromatids become long and thin again- chromosomes
and a nuclear envelope reforms, the cytoplasm also divides – cytokinesis
to produce two genetically identical daughter cells. All of these processes
are driven by the hydrolysis of ATP. The function of ATP is so important
here as without is mitosis wouldn’t occur- mitosis is important for
replacing faulty and damaged cells and for growth of multicellular
organisms in the body.
ATP is also important for processes involving he exchange of substances
in an organism. For example active transport- the movement of molecules
from an area of lower concentration to an area of higher concentration
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