A levels/IB biology enzymes and metabolism summary (with syllabus and exam questions))
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Course
Biology
Institution
Oxford University (OX)
This 21 page document offers in depth descrptions, diagrams, graphs, labelling etc. about enzymes and metabolism. The document talks about enzyme inhibition, explains graphs, answers exam/past paper questions, denaturation, effects of temp/ph on enzymes, activation energy, exothermic vs endothermic...
Enzymes and metabolism
https://ibguides.com/biology/notes/enzymes/
Green highlighter: extra info
C1.1.1— Enzymes as catalysts
• Enzyme: A globular protein that increases the rate of a biochemical reaction by lowering the
activation energy threshold (ie. A biological catalyst).
• Define Catalyst: A catalyst is a chemical that speeds up chemical reactions. In organisms,
catalysts are called enzymes. Essentially, enzymes are biological catalysts. Like other
catalysts, enzymes are not reactants in the reactions they control. They help the reactants
interact but are not used up in the reactions.
• Role of enzymes in the chemical reactions on which life is based: They act as catalysts,
which means that they make biochemical reactions happen faster than they would
otherwise. Without enzymes, those reactions simply would not occur or would run too
slowly to sustain life.
• Enzymes speed up chemical reactions without being altered, so they can be reused.
C1.1.2— Role of enzymes in metabolism
• Define metabolism: Metabolism describes the totality of chemical reactions that occur
within a living organism in order to maintain life These reactions are catalyzed by enzymes
and allow organisms to grow and reproduce, maintain their structures, and respond to their
environments. It is the web of all enzyme-catalysed reactions that occur within a cell or
organism.
• Specificity in relation to enzyme structure: The specificity of an enzyme depends on its
three-dimensional structure which is critical for its normal functioning. According to the
lock-and-key hypothesis of enzyme action, the three-dimensional structure of the active site
of an enzyme allows the enzyme to bind easily to specific substrates only. The specificity of
an enzyme is primarily due to the precise arrangement of atoms in the active site, which is a
region on the enzyme where the substrate binds. The active site is uniquely suited to bind a
specific substrate and not others, much like a lock and key. This is known as the 'lock and
key' model.
• Specificity in relation to enzyme function: Enzyme specificity refers to the speed at which
enzymes can catalyze reactions, with certain enzymes being faster than others. Enzyme
specificity is the tendency of enzymes to bind and catalyze reactions with specific substrates
due to their complimentary shapes and structures.
,•
• How do enzymes control metabolism: Enzymes are proteins that help speed up metabolism,
or the chemical reactions in our bodies. They build some substances and break others
down.
• Why are enzymes essential: Enzymes lower the activation energies of chemical reactions; in
cells, they promote those reactions that are specific to the cell's function. Because enzymes
ultimately determine which chemical reactions a cell can carry out and the rate at which
they can proceed, they are key to cell functionality.
•
, C1.1.3— Anabolic and catabolic reactions
• Contrast anabolic and catabolic reactions: Catabolism, at its core, involves breaking down of
complex molecules and releasing energy for the body to use. The anabolic process is the
complete opposite of catabolism as it involves creating bigger, complex molecules from
smaller, simpler molecules. These are usually stored by the body for future use.
•
• 1st example of anabolic reactions: Photosynthesis, where CO2 and water are built up into
complex sugars.
• 2nd example of anabolic reactions: Protein synthesis, where amino acids are joined together
in sequence.
• 3rd example of anabolic reactions: The formation of glycogen by linking glucose molecules
together.
• Anabolic reactions often include condensation reactions. Anabolic reactions are endergonic
(they require an input of energy to take place). Energy-storing products are the end result.
• 1st example of catabolic reactions: Respiration, where CO2 and water are produced from the
oxidation of sugars.
• 2nd example of catabolic reactions: Deamination of proteins to release urea.
• 3rd example of catabolic reactions: Breakdown of macromolecules into monomers during
digestion
• Catabolic reactions often include hydrolysis reactions. Catabolic reactions are exergonic
(free energy is released for cellular processes or as excess heat)
C1.1.4— Enzymes as globular proteins with an active site for catalysis.
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