BABS1201 Lecture Notes - Lecture 8: Metabolic Pathway, Activation Energy, Amylase
17 May 2018
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BABS1201
9TH APRIL 2018
METABOLISM I
EXPLAIN THE DIFFERENCES BETWEEN ANABOLISM AND CATABOLISM
× Metabolism- the biology of energy transformations and energy exchanges within and
between living things and their environments
× Metabolic processes are all the chemical reactions that occur in cells, tissues, organs and
organ systems
× Metabolism is the sum total of all the chemical reactions within a living organism and can
be characterised by two kinds of metabolic reactions:
- Catabolism- the processes by which a living organism obtains its energy and raw
materials from nutrients- the breakdown of molecules from complex to simple with
enzymes, e.g. starch (complex carbohydrate) being broken down into its glucose
monomers by amylase
× Catabolic reactions release energy, i.e. they are exergonic and exothermic
- Anabolism- the processes by which energy and raw materials are used to build
macromolecules and cellular structures (biosynthesis), the synthesis of molecules
from simple to complex, requiring an input of energy, e.g. the formation of
proteins from amino acids
× Anabolic reactions absorb or require energy, i.e. they are endergonic and
endothermic
× Enzymes and activation energy
- Bonds must be destabilised before any reaction can occur
- Activation energy must be supplied so that the bond will break
- Enzymes are biological catalysts, and reduce the amount of activation energy
required for a reaction to proceed (however, the same net energy is still released,
with and without enzymes)
- Catalysts speed up a reaction without affecting the products
- Catalysts are not consumed or changed during the reaction
× Enzyme function
- An enzyme works by binding with its substrate, the molecule whose reaction is
catalysed
- Enzymes are specific to their substrates, e.g. amylase, which breaks down starch, is
quite different to lactase, which breaks down milk sugar (lactose)
- The specificity is determined by the active site
- The active site is the location on the enzyme where the substrate fits
EXPLAIN THE BASIC MODEL FOR ENZYME CATALYSIS AND THE CONCEPT OF METABOLIC CONTROL VIA
FEEDBACK INHIBITION
× Enzymatic pathways for metabolism
- Metabolic reactions take place in a step-wise fashion in which the atoms of the raw
materials are rearranged, often one at a time, until the formation of the final
product takes place- each step requires its own enzyme
- The sequence of enzymatically-catalysed steps from a starting raw material to final
end product is called an enzymatic pathway (or metabolic pathway)- an example of
this is glycolysis
× What affects enzyme activity?
- Environmental conditions
× Optimum temperature- the temperature at which enzymatic reaction
occurs fastest. High temperatures may denature (unfold) the enzyme
× pH- most enzymes function optimally at 6-8 pH (near neutral), however,
some prefer acidic or basic conditions
× Substrate concentration- the rate of reaction increases as substrate
concentration increases (at constant enzyme concentration). Maximum
activity occurs when the enzyme is saturated (when all enzymes are bound
to a substrate)
Document Summary
Metabolism- the biology of energy transformations and energy exchanges within and between living things and their environments. Metabolic processes are all the chemical reactions that occur in cells, tissues, organs and organ systems. Metabolism is the sum total of all the chemical reactions within a living organism and can be characterised by two kinds of metabolic reactions: Catabolic reactions release energy, i. e. they are exergonic and exothermic. Anabolic reactions absorb or require energy, i. e. they are endergonic and endothermic. Bonds must be destabilised before any reaction can occur. Activation energy must be supplied so that the bond will break. Enzymes are biological catalysts, and reduce the amount of activation energy required for a reaction to proceed (however, the same net energy is still released, with and without enzymes) Catalysts speed up a reaction without affecting the products. Catalysts are not consumed or changed during the reaction. An enzyme works by binding with its substrate, the molecule whose reaction is catalysed.
