Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Topic 8 – Metabolism, Cell Respiration, and Photosynthesis

Enzymes
Metabolism: The chemical reactions that occur in living organisms (controlled by enzymes)
Metabolic Pathway: Chains and cycles of enzyme-catalysed reactions
Enzyme: Biological catalysts that speed up chemical reactions in cells
The enzyme binds to the
substrate, lowering activation
energy by weakening the bonds
...

Inhibitors: They slow the rate of
an enzyme controlled reaction
Competitive inhibitors have a
similar structure to the enzyme’s
normal substrate, and they bind
to the active site to prevent the
substrate from binding, reducing
the reaction rate
...

Infection by viruses can be treated by inhibitors to the viral enzyme protease
...

Non-competitive inhibitors have a different shape to the enzyme’s normal substrate
...
This means
that the substrate can no longer attach to the active site, so the rate of reaction is reduced
...
If this enzyme is inhibited, ATP cannot be made since oxygen use is
decreased, which is potentially fatal
...
If the rate
of reaction increases, there is a competitive inhibitor
...


1

Topic 8 – Metabolism, Cell Respiration, and Photosynthesis
End-product inhibition controls metabolic pathways
...
This is useful
because the isoleucine at the
end of the pathway acts as a
non-competitive inhibitor at the
start of the pathway, so

threonine reacts and not as much isoleucine will be made
...
5,655 chemicals
that could act as an enzyme inhibitor in Plasmodium were identified
...
Inhibitors
were found from 6/9 enzymes and are being researched as potential anti-malarial drugs
...

In oxidation reactions, substances lose electrons, lose hydrogen, or gain oxygen
...

It transfers energy within the cell and releases it instantly for reactions that require energy
...
It
is also soluble and easily transported
...
This makes
molecules less stable
...
Both photosynthesis and respiration
involve coenzymes
...
These
coenzymes are responsible for transferring hydrogen atoms or ions and act as electro carriers
...

Respiration takes place in the mitochondria
...

Outer Membrane: separates contents
of mitochondria from the rest of the
cell
...

Intermembrane Space: protons are
pumped into this space
...

Inner Membrane: contains electron
transport chains and ATP synthase
which
carry
out
oxidative
phosphorylation
...

Christae: tubular projections of inner membrane which increase surface area available for oxidative
phosphorylation
...


Glucose is phosphorylated by 2 ATP, which makes 2
ADP and 2 Pi

This makes hexose bisphosphate (this is
phosphorylation)

Hexose bisphosphate undergoes lysis to give 2
molecules of triose phosphate

Triose phosphate is oxidised to pyruvate – NAD is
reduced in this process and 4 ATP molecules are produced

Pyruvate then enters the link reaction

3

Topic 8 – Metabolism, Cell Respiration, and Photosynthesis
The Link Reaction
The link reaction occurs in the matrix of
the mitochondria because pyruvate is
small enough to move through the
mitochondrial membrane
...
The remaining 2 carbon
molecule reacts with coenzyme A
...


Krebs Cycle
The Krebs cycle takes place in
the
matrix
of
the
mitochondria
...

 Citrate is oxidised to form a
5 carbon compound
...
CO2 is produced



again and NAD is reduced to NADH
The 4 carbon compound undergoes several changes to reform oxaloacetate
...

The oxaloacetate is used to start the cycle again

The reduced NAD and FAD (NADH and FADH) carry the hydrogen ions to the electron transport chain,
which is on the cristae of the mitochondria, for oxidative phosphorylation
...

 Electrons are passed from carrier to
carrier, providing energy to pump
hydrogen ions into the intermembrane
space, setting up a H+ gradient (proton
gradient)
...

 Oxygen is the final electron acceptor
and combines with H+ and electrons to form water
...
It releases energy, so ATP synthase makes ATP
...

Granum: a stack of thylakoids for absorption of as
many photons of light as possible
Thylakoid Space: has a small volume for a steep
proton gradient to build up after few photons of
light have been observed
Stroma: contains all the enzymes of the Calvin cycle,
including large quantities of rubisco
...
Also
provides a site for electron flow, the generation of a proton gradient, and chemiosmosis
Photosynthesis: 6C02 + 6H2O  C6H12O6 + 6O2
Chlorophyll is the pigment found in chloroplasts
...

The Light-Dependent Stage
During this stage NADH and ATP are produced for the light-independent stage
...

5

Topic 8 – Metabolism, Cell Respiration, and Photosynthesis
Chlorophyll A and chlorophyll B are the two main pigments in plants that absorb light
...

Photosystem II: photons of
light strike photosystem II,
exciting 2 electrons
...

Primary Electron Acceptor and
Electron Carriers: electrons are
passed down the carriers,
releasing energy to pump
protons
through
the
membrane
...

Formation of ATP: ATP is
formed using ATP synthase and a proton gradient
...
This is
chemiosmosis
...

Photosystem I: two excited electrons are passed along a series of carriers and go to reduce NADP in
the stroma
...

The Light-Independent Stage
The light-independent stage occurs in the stroma
...
Carbon, in the
form of carbon dioxide, is ‘fixed’ and built up into sugars
...


6



---