Download Glycolysis

Glycolysis
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Glycolysis
• glycolysis is another word for the breakdown
of glucose
• if glucose is broken done in the presence of
oxygen, carbon dioxide, and water you have
the formula:
– C6H12O6 + 6O2  6CO2 + 6H2O
• glucose + 6 oxygen  6 carbon dioxide + 6 water
• cell takes the glucose apart and then captures
then energy a little bit at a time
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Calories
• the end product from the formula on the
previous slide gives off about 3811 calories
per gram of glucose (sugar)
• a calorie is a unit of heat, more specifically
how much heat is needed to raise the
temperature 1 degrees Celsius
• glucose has A LOT of energy--more than ATP
and NADPH
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Glycolysis
• glycolysis is the first stage in the breaking
down of glucose
• takes place in the cytoplasm of the cell
• in glycolysis, a series of enzymes speed up
chemical reactions that change glucose, one
step at a time, into different molecules
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First Step of Breaking Down Glucose
• a molecule of glucose goes through a few
chemical reactions
• these reactions split the 6-carbon sugar into
two 3-carbon PGAL (phosphoglyceraldehyde)
molecules
• two molecules of ATP are used in this first
process
• the cell must use some of the energy it has
stored away to begin the breakdown of glucose
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Next Few Steps of Glycolysis
• the 2 PGAL molecules are turned into 2
molecules of pyruvic acid (3-carbon
compound)
• the energy from the 2 PGAL molecules is used
to make 4 molecules of ADP and 2 molecules
of NADH
– NADH is an energy storing compound similar to
NADPH
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Next Few Steps of Glycolysis (cont.)
• in glycolysis 4 molecules of ATP are made
into 4 molecules of ADP
• there is a gain of 2 molecules of ATP during
glycolysis
• the 2 molecules of ATP produced are more
than 2% of the total chemical energy in
glucose
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Respiration
• as long as there is oxygen, respiration can take
place
• aerobic processes, like respiration, need
oxygen
• respiration is the process that involves oxygen
and breaks down food molecules to release
energy
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Respiration (cont.)
• the pyruvic acid produced by glycolysis is
what is used in respiration
• when the pyruvic acid is broken down, the
energy goes into 34 more molecules of ATP
• chemical reactions of respiration take place in
the mitochondria
– the reactions are enclosed by the inner membrane
– the 2nd set of reactions are inside the inner
membrane
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Respiration Info.
• respiration is a synonym for breathing
• both plants and animals use some type of
respiration--whether it’s “breathing” or cellular
respiration
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Krebs Cycle
• the first set of reactions in respiration are
called the Krebs Cycle--discover was Hans
Krebs
• the Krebs Cycle doesn’t make an
end product, but rather is a continuous
circle of reactions
• known as citric acid cycle since citric
acid is formed in the cycle
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Kreb’s Cycle (cont.)
• the pyruvic acid, produce by glycolysis, travels
from the cytoplasm to the mitochondrion
• in the first reaction, the pyruvic acid is broken
down in CO2 and a 2-carbon acetyl group
• the acetyl-coenzyme A passes the 2-carbonsof
the acetyl group into the Krebs Cycle where
they are joined with a 4-carbon compound
• that then produces citric acid, 6-carbon
compound
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Krebs Cycle (cont.)
• there are nine reactions and nine intermediates
that make up the Krebs Cycle
• two places CO2 is released
• four spots where a pair of high-energy
electrons are taken in by electron carriers
– changes NAD+ to NADH
– changes FAD to FADH2
• a molecule of GDP (close to ADP) is
converted to GTP (close to ATP)
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Krebs Cycle Summary
• 2 carbon atoms added (from breakdown of
pyruvic acid)
• 2 carbon atoms removed (in 2 molecules of
CO2)
• 3 molecules of NAD+ converted to NADH
• 1 molecule of FAD converted to FADH2
• 1 molecule of ADP converted to ATP
• CO2 produced by the cycle is released from the
cell
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Electron Transport in the Mitochondria
• electrons from NADH and FADH2 are passed to
many electron transport enzymes which form an
electron transport chain
• at the end of the chain, an enzyme combines electrons
from the chain, H+ (hydrogen ions) from the fluid in
the cell, and O2 (oxygen) to make H2O (water).
• oxygen is the final electron accepter and is needed to
obtain energy from NADH and FADH2
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ATP Formation
• the mitochondria accepts electrons, while some
enzymes pump hydrogen ions outside the inner
membrane
• movement of hydrogen ions is what powers
the making of ATP
• the movement of a pair of electrons down the
electron transport chain produces enough
energy to make 3 ATP molecules from ADP
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ATP Formation (cont.)
• the more H ions on the outside makes the
outside more positively charged then the inside
• the difference in the charges gives the energy
needed to make ATP from ADP
• the mitochondrion membrane lets the enzymes
pump ions out, but won’t let them come back
in
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Totals
• glycolysis makes a net-gain of 2 ATP
molecules and passes electrons to 2 NADH
molecules
• the energy from he NADH molecules makes
10 ATP molecules
– (4 from Glycolysis & 6 from the first step of the
Kreb’s cycle)
• in respiration, 6 more NADH, 2 ATP, and 2
FADH2 molecules are made in the Krebs Cycle
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Totals (cont.)
• electrons use the energy from NADH and
FADH2 to produce 22 ATP molecules
• between glycolysis and respiration 36 ATP
molecules are made from one molecule of
glucose
• the energy in the 36 ATP molecules is about
37-38% of the total available chemical energy
in glucose
– Still makes the human body more efficient than a
car engine
– Where does the other 62% of the energy released
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go?
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Getting Energy from Food
• complex carbs. are broken down into simple
sugars which are them converted to glucose
• lipids and proteins can be broken down to go
through glycolysis and the Krebs Cycle
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How Important is Oxygen??
• without oxygen, electron transports can
happen, the Krebs Cycle will stop, and the
making of ATP in the mitochondria will also
stop
• if our bodies don’t get enough oxygen, then
they’ll try to work from the oxygen from
glycolysis and that is not enough
• oxygen has a major role in the mitochondria of
a cell
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Balance
• photosynthesis and respiration can be thought
of as opposite reactions
• photosynthesis gives energy, respiration takes
energy
• respiration and photosynthesis’ equations are
reverse of each other
• the products of photosynthesis are the reactants
for the breaking down of glucose
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Balance (cont.)
• the products of breaking down glucose, are the
reactants in photosynthesis
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Fermentation
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Fermentation
• in order for glycolysis to continue, NADH
must be converted back to NAD+
• the only way to do that is with fermentation
• fermentation is an anaerobic process, meaning
it doesn’t require oxygen
• NADH is converted to NAD+ by adding extra
electrons in NADH to an organic molecule
acting as an electron accepter
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Fermentation (cont.)
• fermentation lets cells carry out energy
production in the absence of oxygen
• together, glycolysis and fermentation make 2
ATP molecules from a molecule of glucose
• the two ways to change NADH to NAD+ is
alcoholic and lactic acid fermentation
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Lactic Acid Fermentation
• pyruvic acid that accumulates as a result of
glycolysis can be turned into lactic acid
• lactic acid fermentation produces lactic acid
• this process regenerates NAD+ so that
glycolysis can continue
• pyruvic acid + NADH  lactic acid + NAD+
• lactic acid is often produced in muscles when
one is doing rapid exercises
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Lactic Acid Fermentation (cont.)
• after doing some form of exercise very
quickly, your muscles produce ATP by
fermentation and during this lactic acid is
made
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Alcoholic Fermentation
• alcoholic fermentation occurs in yeasts and
other small microorganisms
• pyruvic acid is broken down to make a 2carbon alcohol and CO2
• alcoholic fermentation produces alcohol
• pyruvic acid + NADH  alcohol +CO2 + NAD+
• the carbon dioxide made by yeast during
fermentation makes breads rise
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Alcoholic Fermentation (cont.)
• the CO2 released by fermentation also causes
the bubbles in the wines and beers
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