Metabolism

1. M E TA B O L I S M
PAT H WAY S
I N
B I O S P H E R E

2. Metabolism
is the set of life-sustaining chemical reactions in
organisms.
The three main purposes of metabolism are:
the conversion of food to energy to run cellular
processes;
 the conversion of food/fuel to building blocks for
proteins, lipids, nucleic acids,
some carbohydrates; and the elimination of

3. There are two kind of metabolic reactions…
 Anabolic reactions.
 Catabolic reactions.

4. Metabolic processes
Catabolic = Breakdown:
generation of energy and reducing power from complex molecules
produces small molecules (CO2, NH3) for use and as waste products
Anabolic = Biosynthesis:
construction of large molecules to serve as cellular components such as
amino acids for proteins, nucleic acids, fats and cholesterol
usually consumes energy

5. Two Phases of Metabolism

6. Photosynthesis
Photosynthesis is an anabolic reaction which is happening mainly in green trees of biosphere.

10. The calvin cycle(C3 cycle)
light-independent reactions, dark reactions, or
photosynthetic carbon reduction (PCR) cycle of
photosynthesis are the chemical reactions that
convert carbon dioxide and other compounds into
glucose. These reactions occur in the stroma, the
fluid-filled area of a chloroplast outside the
thylakoid membranes. These reactions take the
products (ATP and NADPH) of light-dependent
reactions and perform further chemical processes on
them. There are three phases to the light-
independent reactions, collectively called the Calvin
cycle: carbon fixation, reduction reactions, and
ribulose 1,5-bisphosphate (RuBP) regeneration.

11. C4 carbon fixation
or the Hatch–Slack pathway is a photosynthetic process in some plants. It is the first step in extracting
carbon from carbon dioxide to be able to use it in sugar and other biomolecules. It is one of three known
processes for carbon fixation. "C4" refers to the four-carbon molecule that is the first product of this type of
carbon fixation.
C4 fixation is an elaboration of the more common C3 carbon fixation and is believed to have evolved more
recently. C4 overcomes the tendency of the enzyme RuBisCO to wastefully fix oxygen rather than carbon
dioxide in the process of photorespiration. This is achieved by ensuring that RuBisCO works in an
environment where there is a lot of carbon dioxide and very little oxygen. CO2 is shuttled via malate or
aspartate from mesophyll cells to bundle-sheath cells. In these bundle-sheath cells CO2 is released by
decarboxylation of the malate. C4 plants use PEP carboxylase to capture more CO2 in the mesophyll cells.
PEP (phosphoenolpyruvate, three carbons) binds to CO2 to make oxaloacetic acid (OAA). OAA then makes
malate (four carbons). Malate enters bundle sheath cells and releases the CO2. These additional steps,
however, require more energy in the form of ATP. Using this extra energy, C4 plants are able to more
efficiently fix carbon in drought, high temperatures, and limitations of nitrogen or CO2. Since the more
common C3 pathway does not require this extra energy, it is more efficient in the other conditions.

13. Cellular respiration
Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organisms
to convert biochemical energy from nutrients into adenosine triphosphate (ATP), and then release waste
products. The reactions involved in respiration are catabolic reactions, which break large molecules into
smaller ones, releasing energy in the process, as weak so-called "high-energy" bonds are replaced by
stronger bonds in the products. Respiration is one of the key ways a cell releases chemical energy to fuel
cellular activity. Cellular respiration is considered an exothermic redox reaction which releases heat. The
overall reaction occurs in a series of biochemical steps, most of which are redox reactions themselves.
Although cellular respiration is technically a combustion reaction, it clearly does not resemble one when it
occurs in a living cell because of the slow release of energy from the series of reactions.

15. Protein synthesis
is the process whereby biological cells generate new proteins; it is balanced by the loss of
cellular proteins via degradation or export. Translation, the assembly of amino acids by
ribosomes, is an essential part of the biosynthetic pathway, along with generation of
messenger RNA (mRNA), aminoacylation of transfer RNA (tRNA), co-translational transport,
and post-translational modification. Protein biosynthesis is strictly regulated at multiple
steps.They are principally during transcription (phenomena of RNA synthesis from DNA
template) and translation (phenomena of amino acid assembly from RNA).

17. Excretion
is a process by which metabolic waste is eliminated from an organism. In vertebrates this is
primarily carried out by the lungs, kidneys and skin. This is in contrast with secretion, where
the substance may have specific tasks after leaving the cell. Excretion is an essential process
in all forms of life. For example, in mammals urine is expelled through the urethra, which is
part of the excretory system. In unicellular organisms, waste products are discharged directly
through the surface of the cell.
During life activities such as cellular respiration, several chemical reactions take place in the
body. These are known as metabolism. These chemical reactions produce waste products
such as carbon dioxide, water, salts, urea and uric acid. Accumulation of these wastes
beyond a level inside the body is harmful to the body. The excretory organs remove these
wastes. This process of removal of metabolic waste from the body is known as excretion

20. Fermentation
is a metabolic process that produces chemical changes in organic substrates through the action of
enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the
absence of oxygen. In the context of food production, it may more broadly refer to any process in which
the activity of microorganisms brings about a desirable change to a foodstuff or beverage. The science of
fermentation is known as zymology.
In microorganisms, fermentation is the primary means of producing ATP by the degradation of organic
nutrients anaerobically. Humans have used fermentation to produce foodstuffs and beverages since the
Neolithic age. For example, fermentation is used for preservation in a process that produces lactic acid
found in such sour foods as pickled cucumbers, kimchi, and yogurt, as well as for producing alcoholic
beverages such as wine and beer. Fermentation occurs within the gastrointestinal tracts of all animals,
including humans