AP Biology Unit 3: Metabolism and Homeostasis Notes

UNIT 3: METABOLISM AND HOMEOSTASIS



Introduction to Metabolism (Ch. 6)
​General structure of ATP
​The functions of enzymes
-​ Enzymes are proteins: provide a
space(active site) for
reactants(substrates) to me
-​ Tool for reactions, can speed up or slow
down reactions
​How/why enzymes lower the activation
energy
-​ The enzymes allows the substrates to meet and create a product easier so there is
less of a need for activation energy.
​The catalytic cycle of an enzyme involving its active site
-​ Catalyst: the leftover
-​ The enzyme binds two substrates together to make a product and goes on to the next
one, so more products are created from one enzyme
​Difference between exergonic and endergonic reaction
-​ Exergonic reactions: spontaneous, releases energy
-​ Endergonic reactions: not spontaneous, requires energy
​Difference between anabolic and catabolic pathways
-​ Anabolism: endergonic reaction (requires energy)
-​ Catabolism: exergonic reaction (releases energy)


​Different forms of energy and descriptions
-​ Light energy: used for photosynthesis
-​ Glucose: sugar energy used in cellular energy production
-​ ATP: chemical energy created from cellular respiration


​The laws of thermodynamics
1.​ Energy can not be created nor destroyed, only converted
2.​ Energy transfers in the universe increase entropy


​How the hydrolysis of ATP provides energy for work, and the regeneration provides
storage
-​ Hydrolysis of ATP ⇒ ATP + H2O ⇒ ADP + Pi
-​ Hydrolysis of ATP and ADP is reversible ⇒ regenerates ATP from ADP and P
-​ ATP provides storage for potential energy since it will be broken again and it will
release energy.
-​ Why does it release energy? ATP breaks bonds: breaks ADP and a phosphate group, ATP
also forms bonds: forms bonds between broken phosphate group and OH, forms bond
between H and ADP.

, ​The relationship between an enzyme and its substrate (ex: charges must be
complementary)
-​ Enzymes are proteins that provide an active site for substrates to meet and form a
product
-​ Enzymes can help speed up chemical reactions ⇒ lowers activation energy
​Effects of local conditions on enzyme activity - including temp, pH, cofactors, and
enzyme inhibitors, esp. the graphs of them
-​ Competitive enzyme inhibitors: compete with the substrate for the active site +
prohibit products from forming
-​ Noncompetitive enzyme inhibitors: binds at an area away from the active site but
changes its shape to prevent substrate from fitting
-​ Cofactors: help the substrate fit into the enzyme’s
active site


Temperature:
-​ → activity reaches a peak at a certain temperature,
before reaching the peak, temperature increases ⇒
activity increase ⇒ substrates move faster into the
enzymes ⇒ increasing rate of activity
→ after activity reaches the peak, enzymes denature ⇒
slower rate of activity


pH:
-​ Each enzyme has an ideal range of pH range; changing the
pH out of the range ⇒ slows enzyme activity
-​ Extreme pH ⇒ enzyme will denature


Substrate concentration:
-​ Increasing substrate concentration increases the rate of
reaction to a certain point. After all the enzymes are
bound ⇒ increase in substrate concentration won’t have
an effect on enzyme activity b/c enzymes are working at
max rate = saturation


​ Enzyme concentration:
-​ Increase enzyme concentration ⇒ more enzymes substrates
can bind to; once all enzymes are bound ⇒ reaction will
plateau because not enough enzymes for substrates to
bound to



​Regulation (activation and inhibition) of enzymes
-​ Inhibitor: prevent the substrate from working in the enzyme
-​ Allosteric regulation: particle binds at one site and enables a change in
configuration at a separate site allosteric inhibition: inhibitor fits into
allosteric site and changes the shape of the active site