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LET ME ASK YOU…

Would you rather have fifty $1 bills or one $50 bill?
SO THAT MEANS…

Energy in organisms is packaged in small, useful units.
These “energy packets” will be introduced in this
chapter.
CELLULAR RESPIRATION

1st you must know the eqt…
O2 + C6H12O6  CO2 + H2O + E
(be able to balance, say & write in words, write out chemical
formulas)

there are 3 stages:
1st glycolysis
2nd Krebs Cycle
3rd e- transport chain
WHERE DOES CELL RESP TAKE PLACE?
 it


glycolysis occurs in the
Cytoplasm
Krebs Cycle & ETC take
place in the
mitochondria
Copyright Cmassengale
actually takes
place in 2 parts
of the cell:
GLYCOLYSIS (A SERIES OF RXNS)

this process starts w/ 2 ATPs, b/c need E to get started

Need to break glucose into two 3-C molecs called pyruvic acid

during 1 of the rxns, high-E e-’s are excited

2 of these e-’s are sent to the e- transport chain via NAD+ so now it becomes
2 NADH
glycolysis produces 4 ATPs……so what is the net yield of E?
 2 ATP


What role do you think the excited e-’s played?
Glycolysis is anaerobic. What does that mean?
Glucose
2 Pyruvic acid
To the e-transport
chain

Glycolysis is fast! So a lot of ATP can be produced…but
that could present a problem…

If too much ATP is produced during glycolysis then in a
few seconds all of the available NAD+ molecs will be
filled w/ e-’s, thus none are available to go back and
continue the process. So what happens?
WHAT HAPPENS TO PYRUVIC ACID?

It depends on whether or not O2 is present. If O2 isn’t present 1 of
the following 2 processes takes place:

alcoholic fermentation (used by yeast & other microorgs)
pyruvic acid + NADH  alcohol + CO2 + NAD+
The CO2 here causes bread dough to rise, this would also be the
method for making some alcoholic drinks
Some unicellular orgs use this process to create foods we eat like
butter, yogurt, buttermilk, kimchi, pickles, saurkraut.
or

lactic acid fermentation
pyruvic acid + NADH  lactic acid + NAD+
This happens during vigorous exercise when you are not breathing properly
(hence absence of O2), but your body still needs ATP so it creates some by this
process. Lactic acid builds up in your muscles and causes a painful, burning
sensation.
BUT IF THERE IS O2 AVAILABLE THEN…

in the presence of O2, pyruvic acid goes on to the Krebs Cycle
(or Citric Acid Cycle)
 takes place in the matrix

1st pyruvic acid enters the mitochondria & goes thru a series of
rxns where:
it is broken into acetyl Co-A
 during the process CO2 is released
 acetyl Co-A is further broken into citric acid


as the cycle continues ATP is produced for more cell activities,
& FADH2 & NADH are produced
 remember there are 2 pyruvic acids, so cycle turns twice to
produce 1 ATPs, 4 NADHs, 1 FADH2, & 1 CO2 each turn

Hold on, where will that FADH2 & NADH go?
What did we do w/ those kinds of molecs in other processes?
Citric Acid
Production
Mitochondrion
THE ELECTRON TRANSPORT CHAIN
 NADH
& FADH2 bring the high-E e-’s to the e- transport
chain

in the inner mitochondrial memb (cristae)
 the

e-’s are passed from 1 carrier to the next
Hot potato!
@
the end of the chain is an enzyme that combos these
e-’s with H+ and O2 atoms to form H2O
Thus O2 is essential for getting rid of low-E
e-’s & H+.
 The waste of cell resp is H2O.

MORE E- TRANSPORT CHAIN
 each
time e-’s move down the chain their E is used to
create the potential difference inside the memb
 so
just as in photosyn, E & ATP synthase create ATP
every time an e- moves down the chain H+ moves across the memb which
causes ATP synthase to spin & generate lots of ATP
 in fact each e- generates 32 ATPs

Electron Transport
Hydrogen Ion Movement
Channel
Intermembrane
Space
ATP synthase
Inner
Membrane
Matrix
ATP Production
ATP SYNTHASE

What kind of molec is ATP synthase?
DIAGRAM OF THE PROCESS
Occurs across
Cristae
Copyright Cmassengale
Occurs in
Cytoplasm
Occurs in Matrix
DON’T MISS THIS!
• Where in cellular respiration are e-’s released?
• What is the significance of all the e-’s that are
released?
HOW MANY TOTAL ATPS ARE PRODUCED?

remember the 2 ATPs from glycolysis

2 more ATPs from Krebs cycle

32 more ATPs are produced in e- transport chain
TOTAL = 36 ATPs

the breakdown of 1 glucose molec nets 36–38 ATPs

This is quite different than fermentation.
What makes the difference?
WHAT TYPE OF RXN IS CELL RESP?

remember the choices are:

endergonic or exergonic
 anabolic
or catabolic
REMIND ME AGAIN WHY THE CELL USES ATP…
As far as known, all orgs from the simplest bacteria to humans use
ATP as their 1° E currency.

the E level ATP carries is just the right amt for most bio rxns

nutrients contain E in low-E covalent bonds which aren’t v. useful
to do most of kinds of work in the cells

these low E bonds must be translated to hi E bonds, & this is a role
of ATP
HOW IS E RELEASED FROM ATP?

to get the E out, the hi E bonds must be broken
• what is process called that breaks the
bonds?
hydrolysis -
THE ADP-ATP CYCLE
This diagram shows how ATP is made, used, and regenerated.
Copyright Cmassengale
ATP-ase
ATP
Synthetase
PHOTOSYNTHESIS VS. CELLULAR RESPIRATION
• What are the differences between photosyn
& cell resp?
• What would you say are the similarities between
photosyn & cell resp?
VIDEO SEGMENTS
First
Stages of Digestion (3:32)
Last
Stages of Digestion (3:38)
Fiber
in the American Diet (5:07)
From
Food to ATP (1:56)
Glycolysis
& Cellular Respiration (1:53)
CITRIC ACID….
Citric acid is a very useful and effective preservative, obtained from naturally occurring organic acids. It exists in
many different fruits and vegetables, but is especially concentrated in lemons and limes.
Citric acid is used for many different reasons, including (but not limited to):
 Citric acid is used as a flavoring in many preparations of Vitamin C, and has a wide variety of other uses. In
industry, citric acid can be used to make good “natural” cleaners, though some may still contain chemicals
that are not exactly natural. The ability of citric acid to bond with other minerals can make it helpful in
softening water. Soaps and laundry detergents can be more effective when they contain citric acid. It can
work well in shampoos because it tends to remove excess minerals from the water. Yet, sometimes a high
concentration of citric acid can damage hair, since it opens hair cuticles. It can strip the hair of needed
minerals and bleach it.
 As a food additive, citric acid is in common use. It can be added to flavor certain drinks, especially soft
drinks. It works well as a meat tenderizer because it tends to break down the meat proteins. However, it is
bitter — one of its main uses in food is to make certain candy sour.
 When you buy sour candies, you may note many of them are covered with a fine white powder. This is citric
acid, which adds an exterior coating to the candies and provides quite a bit of sour taste. It can make the
mouth pucker or feel dry, and higher quantities will produce very sour candies.
 You’ll note citric acid in a variety of cleaning products and especially now in beauty products. With sodium
bicarbonate, citric acid may be added to produce bath fizzes or bath tablets. The combination of the two
produces carbon dioxide and makes for pleasantly effervescent water.
 Citric acid is a common ingredient in skin masks and some lotions. Vitamin C in general is thought an
antioxidant that can help refresh skin and reduce the look of aging by promoting new skin growth and
destroying free radicals. Too much exposure to citric acid can cause mild skin irritation, and it may be a good
idea not to use skin products containing it if you have sensitive skin.
 One of the best benefits of citric acid in all its applications is that it is natural and poses little to no risk to the
environment. Very few people are allergic to citric acid, but some people may have stomach sensitivity to it,
and might better avoid foods containing it. Read labels carefully, since citric acid may be used as a
preservative in many more foods than you might expect.
 It’s also now commonly used in preparing photographs.