Cell Biology: Enzymes Lesson 1 – Enzyme Theory and Function ( Inquiry into Life pg. 106-109 )
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Transcript of Cell Biology: Enzymes Lesson 1 – Enzyme Theory and Function ( Inquiry into Life pg. 106-109 )
Cell Biology:Enzymes
Lesson 1 – Enzyme Theory and Function(Inquiry into Life pg. 106-109)
Today’s Objectives Analyze the roles of enzymes in biochemical
reactions, including: Explain the terms: metabolism, enzyme, substrate,
coenzyme, activation energy Use graphs to identify the role of enzymes in lowering
the activation energy of a biochemical reaction Explain models of enzymatic action (eg. Induced fit) Differentiate between the roles of enzymes and
coenzymes in biochemical reactions Identify the role of vitamins as coenzymes Identify the thyroid as the source gland for thyroxin,
and relate the function of thyroxin to metabolism
Definitions Metabolism:
A term which refers to all the chemical reactions of a cell Enzyme:
A protein catalyst (speeds up a certain reaction) (not used up)
Apoenzyme: Protein portion of an enzyme Its shape accounts for an enzyme’s ability to run only a
single type of reaction Coenzyme:
Non-protein portion of an enzyme Can donate or accept atoms to or from a reaction Our body often cannot make coenzymes, so we need them in
our diet Example: vitamins
Definitions Holoenzyme:
Enzyme that requires a coenzyme to function Enzyme + coenzyme = holoenzyme
Definitions Substrate:
A reactant (raw material) in an enzyme-controlled reaction
Activation Energy: Many reactions will not occur unless energy is
added to start them off This input energy is called activation energy or
energy of activation (Ea) Example: a piece of woods needs an input of
energy to start it burning
Enzyme Function Enzymes bring the substrate close enough
together so that the reaction can occur without as much activation energy
Enzyme Theory Lock and Key Theory of Enzyme Action:
1) In order for a reaction to occur, the reactants (substrates) must be brought close together
2) The substrates bond to the active site on the enzyme, and are brought close together. Sometimes the active site changes shape to bring the substrates together (this is also called the induced fit model
3) The reaction occurs and the product(s) are released. The enzyme goes back to its normal tertiary configuration (shape)
Lock and Key Theory
Lock and Key Theory
Review of Lock and Key According to this analogy, an enzyme acts like
a key by combining with a specific substrate and “unlocking” the substrate for further activity in the cell
The key (enzyme) must have the correct shape to fit the lock (substrate)
After the lock has been opened (reaction takes place), the key (enzyme) is freed and unchanged so that it may be used repeatedly in the same manner
The portion of the enzyme that is involved in the reaction is called the active site
Review of Lock and Key
Metabolic Pathway (pg. 106) Metabolic reactions often require more than
one step to produce the final product This is called a metabolic pathway A series of reactions will take place, where
the products of the first reaction become the substrate for the second reaction, and so on ABCD A = Beginning substrate B,C = intermediate products/reactants D = final product Each step requires a specific enzyme
Role of Coenzymes Coenzymes are the non-protein portion of
an enzyme Can participate in a reaction by accepting
or contributing atoms to the reaction
Significance of Vitamins Many coenzymes are vitamins Our bodies cannot make many of those
that we require, we must get them in our diet
Vitamins are vital for efficient metabolism We only need small quantities because
as part of enzymes, they can be used over and over again
Thyroxin Thyroxin is a protein hormone
that is secreted into the blood by cells of the thyroid gland
The thyroid gland, located in the neck, accumulates iodine in order to produce thyroxin
Thyroxin attaches to receptor sites on the surfaces of our body cells where it governs the rate that cells consume oxygen, thus having an overall impact on the body’s metabolism
Thyroxin Thyroxin does not have a target organ; it
stimulates most of the cells of the body to metabolize at a faster rate
The number of respiratory enzymes increases, as does oxygen intake
Thyroxin helps regulate growth and development
Thyroglobulin is the storage form of thyroxin Iodine is required for thyroglobulin to be
made If no iodine, no thyroxin