Success criteria – Unit 2
These success criteria are what the exam board expects you to have learned in
this topic. The SQA questions in examinations are based on these success
criteria.
Look at each one. Do you remember and understand that piece of
learning?
Code each outcome: green (for no problems), yellow (for slight concerns),
red (for problem area).
Use the revision periods, and other resources, to try and improve.
Revaluate your progress after revising and note any areas that which will
need more work later.
Success criteria
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Learning
evaluatio
n at the
end of the
topic
Learning
evaluation
after
revision
Areas
needing
further
work
later
Metabolism is the total collection of all
the chemical reactions taking place
within the cell
Reactions occur in sequences, each
reaction is catalysed by an enzyme
Each sequence of reactions is known as
a pathway
The pathways are linked and may be
reversible
Anabolic pathways involve the
building or synthesis of molecules and
require energy
Catabolic pathways involve the
breakdown or degradation of substrates
and release energy.
Often there are alternative pathways
that achieve the same, or similar, end
results
Membranes can form compartments in
which conditions for reactions are more
favourable
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Enzymes are often located on
membranes and organise the sequence
of reactions
Proteins embedded in membranes can
act as pores, channels and pumps
The activity of an enzyme is highly
dependent on its shape
It is this shape that allows the enzyme
to connect with its substrate, but it can
also lead to inhibition
The induced fit model
The rate at which an enzyme acts is
dependent on several factors, including
the concentration of its substrate and
product
Many reactions are reversible and take
place as a series of reactions in a
pathway
Some genes are always turned on, ie
they are continually expressed
This is true of those involved in
metabolism and energy release
Genes may have their ‘volume’ turned
up or down and as a result levels of the
enzymes they produce are regulated
Inhibition of an enzyme usually occurs
by a change of shape of the active site
The change in shape can by done
directly by a substance other than the
substrate filling the active site
(competitive inhibition) or by a
substance attaching to the enzyme in
such a way that it causes the active site
to no longer engage with the substrate
(non-competitive inhibition)
On some occasions an enzyme is
inhibited by the end product of the
pathway
Frequently it is the first enzyme of the
sequence which is inhibited
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Cellular respiration is universal, ie it is
seen in all forms of life
It is the means of generating energy for
all metabolism within the cell
It is interlinked with many other
pathways
Energy within the cell is transferred
between units of ATP
It rapidly cycles between ATP and
ADP + Pi
To synthesise ATP high-energy
electrons and Hydrogen ions have to be
transported across a membrane
The Hydrogen ions flow back along a
gradient through ATP synthase to
generate ATP
ATP synthesis usually takes place in
three stages: glycolysis, citric acid
cycle and electron transport chain, if
oxygen is present
If oxygen is absent much less ATP is
produced and other end products
accumulate
The pathway does not produce ATP
alone
Depending on the needs of the cell
other molecules may be used
While glucose is a common substrate
for respiration, several others can be
used
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