Transcript METABOLISM - OxleyLearning Home

METABOLISM
Its regulation and the importance of
maintaining a constant internal
environment
What is Metabolism?
• The total of ALL chemical reactions in a living
organisms
• Reactions which:
- BUILD UP large compounds from smaller
molecules
- BREAK DOWN large compounds into
smaller molecules
Building Up: Anabolic Reactions
Glucose + Glucose + Glucose (lots & lots!) → Starch
Plants make small monosaccharides GLUCOSE during
photosynthesis then store it as the large polysaccharide
STARCH
Breaking Down: Catabolic Reactions
Starch → Glucose + Glucose + Glucose
Animals & plants breakdown large polysaccharides STARCH into
the small monosaccharide GLUCOSE to use for ENERGY in
CELLULAR RESPIRATION
THINK: another large molecule BROKEN DOWN to smaller units ?
Role of Enzymes
• Enzymes are ESSENTIAL in REGULATING ALL these
reactions.
• They are called BIOLOGICAL CATALYSTS- without
them reactions in living things would happen too
slowly, and Energy would not be accessed
• Enzymes control the RATE of chemical reactions that
make up metabolism in living organisms.
• THEY ARE NOT CONSUMED (used up) IN A REACTION
THEY CATALYSE
Chemical Composition of Enzymes
LARGE PROTEIN MOLECULES
(made of smaller subunits called…..)
- Fold into SPECIFIC SHAPES according to the
SEQUENCE of amino acids in them
- FUNCTION of each enzyme is dependent on its
shape
- If shape of an enzyme changes its function is
IMPAIRED
Enzymes are Specific
• An enzyme’s shape makes it specific to a given
SUBSTRATE
Substrate- the molecule/s being broken down
or built up
• Enzyme has an ACTIVE SITE which fits onto the
substrate
(change shape of active site= cannot fit onto substrate)
Enzyme-Substrate Complex
• http://highered.mcgrawhill.com/sites/0072495855/student_view0/ch
apter2/animation__how_enzymes_work.html
Enzymes reduce Activation Energy
Induced Fit Model
In this model the active site changes shape slightly
then returns to its original shape
Lock & Key Model
In this model the active site DOES NOT change shape
Sensitivity of Enzymes
Enzymes are sensitive to changes in:
- temperature: increases in temperature can
DENATURE the enzyme and change the shape
of the active site
- pH: change in pH can have a similar effect on
as temperature.
In both situations the enzyme is unable to BIND
to the substrate, hence its activity is INHIBITED
Temperature
There is an OPTIMUM TEMPERATURE at which the
enzyme will work best
pH
There is an OPTIMUM TEMPERATURE at which the
enzyme will work best
Substrate Concentration
Why is this all so important…..?
- Biological reactions would not occur as
quickly as needed without enzymes (they
reduce energy needed for reactions to
proceed
- If temperature or pH of the internal
environment of an organism changes,
enzymes cannot do their job and so…..
Therefore….
We need to keep our internal environment
stable in terms of…..
AND
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