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Glycolysis 2
Lecture 23
Pages 439 - 451
Citric Acid Cycle
• Molecular oxygen is involved in this
cycle and changed to form a water
molecule
• All three food groups may enter the
citric acid cycle
• It is a 8 step process
• Takes place in the mitochondria of
eukaryotes (or cytosol of bacterial)
13_10_acetylCoA_prod.jpg
This 8 step cycle is designed to remove 2 carbons at a spin.
The purpose is to produce high energy molecules from low
energy one and the elimination of those 2 carbons as CO2
High energy
3 NADH’s
1 FADH2
1 GTP
The structure of GTP - learn this!
We have a base - Guanine
We have a sugar - Ribose
We have three inorganic phosphates in GTP
& just 2 phosphates in GDP
structure_GTP.jpg
This is the structure of FAD
It is similar to GDP in that it too is made of a base (Adenine) &
the sugar ribose. It has two inorganic phosphates and then a
complex hydrocarbon structure.
structure_FADH2.jpg
If is designed to
carry proton
and electrons which combine
to form
hydrogen in this
case
Remember the names of
each of the products with
the letters next to their
names. These are very
important to the cell
Even though oxygen is
not used directly in the
cycle, it is used in the
generation of ATP from
the carrier molecules.
This oxygen forms water
and not the CO2 that you
breath out.
13_13_02_to_CO2.jpg
RECAP
13_17_final_oxidation .jpg
Starvation prevention
• The cell wants to make and use energy at all
times to live
• Problem is that food is delivered to the cell
periodically
• How does the cell cope?
• Answer: it stores the raw materials for its
energy needs close by
• Animal cells have either lipid drops or
glycogen granules in the cytoplasm
• Plant cells have starch and lipid drops - these
are stored in the chloroplasts
13_18_store_glycogen .jpg
Fat deposits in animal cells are stained red
13_19_store_fats.jpg
Plant Chloroplasts
• Plants are able to perform
photosynthesis during periods with
sunlight
• They make the sugars and other
metabolites themselves, but also use
the same processes of glycolysis as
animal cells to derive energy from the
breakdown of these same sugars
13_20_chloroplasts.jpg
Seeds are high in energy because they contain lots of
stored food reserves such as fats and sugars
13_21_plant seeds.jpg
In plant cells the system can be simplified as illustrated here.
Note that ATP and NADH molecules are not able to leave the
chloroplast membranes. So the organelle exports the sugars
that it makes to other regions of the cell.
13_22_metabolites_ATP.jpg
Plants consume net oxygen at night as we do. Do not
sleep with too many plants in your bedroom without
proper ventilation
These pathways
have another
function in addition
to the generation
of energy: that is
to generate the
raw materials for
other cellular
boichemicals
13_23_precursors.jpg
The biochemical pathways
within cells are complex here is a very simplified view
showing how glycolysis and
the citric acid cycle are
integrated
13_24_metabolism.jpg
About 500 metabolites are
represented here - either
feeding into these two
central pathways or taking
molecules from them