Download Kreb*s Cycle

THE MITOCHONDRIA
A mitochondrion is a
specialized site of aerobic
respiration.
Like chloroplasts,
mitochondria also have
their own DNA and
ribosomes. They also have
a large organization of
membranes that provides
surface area for reactions.
Unlike chloroplasts, it is the
inner membrane that
provides this surface area,
through many folds called
cristae.
https://www.youtube.com/watch?v=RrS2
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FROM CYTOPLASM TO MITOCHONDRIA
Products from glycolysis (2
pyruvate and 2 NADH - what
about ATP?) are first
transported from the
cytoplasm into the
mitochondria through active
transport.
The pyruvate undergoes a
reaction called Pyruvate
Oxidation, under which the
pyruvate is oxidized (and 2
more NAD+ are reduced to
NADH). It loses a CO2 in the
process and the remaining 2Carbon molecule is attached
to Coenzyme A to produce a
molecule called Acetyl CoA.
Note this is the first time CO2 has been given
off. (As this happens for each of the two
pyruvates, this is 2 of the original 6 carbons
found in glucose.)
ACETYL-COA
• Acety-CoA is a central molecule in energy production.
• Can be used to create ATP or store fat
• If body need energy Acyetyl-CoA will enter the Kreb’s cycle ,
transferring most of its energy to ATP. If the body doesn’t
need energy, Acetyl Co-A is sent to an anabolic pathway
that creates lipids as a way of storing large amounts of
energy as fat.
• All nutrients; proteins, lipids and carbohydrates are
converted to acetyl-CoA and then channelled toward fat or
ATP production depending on the energy needs of the
body
THE KREB’S CYCLE
Also known as the citric acid
cycle, this is a cycle that
occurs in the
mitochondrial matrix and
incorporates Acetyl CoA in
order to break it down and
capture its biochemical
energy.
It is an 8 step pathway, and it
occurs twice for every
molecule of glucose (2
acetyl CoA molecules that
result from it).
IMPORTANT STEPS IN KREBS
Important steps:
4C oxaloacetate reacts with 2C
acetyl-CoA to produce 6C
citrate
Energy is harvested in steps 3, 4,
5, 6, and 8
For each acetyl CoA: 3 NADH, 1
GTP/ATP, and 1 FADH2 is
produced.
After step 8, the oxaloacetate
has been recycled, and can be
used again.
** In Step 5, ATP is formed by substrate level
phosphorylation.
• A Pi from the matric removes CoA from succinyl-CoA.
• The Pi is then transferred to Guanosine diphosphate (GDP)
forming GTP.
• The Pi group condenses with ADP forming ATP. Overall, free
energy is transferred from succinyl-CoA to ATP by a form of
substrate level phosphorylation.
FOLLOW THE CARBON
By the end of Krebs cycle, all six carbon atoms of the original glucose
molecule have been lost as CO2 (which will be released as waste).
All that is left of the original glucose molecule is some free energy in
ATP, NADH and FADH2.
In your pods, draw the carbons at the beginning and ending of the three
stages we’ve looked at so far; Glycolysis, Pyruvate Oxidation and
Kreb’s Cycle. .
https://www.youtube.com/watch?v=00jbG_cfGuQ&list=PLMjKVK0oPAVQ1CT
XEhB9wFk3n4r4k9KC2
FOLLOW THE ENERGY
In your groups, determine all the energy products that
arise from the breakdown of glucose. What is our net
energy production at this point?