Harvesting Chemical Energy

As open systems, cells require _________ energy sources to perform cellular work.

Only photosynthetic organisms have the ability to ______________ the energy from
the sun.

During Photosynthesis:
 ________ and _______ are the raw materials used to make __________
 _______________ energy is converted into _____________________ energy

__________________________ energy can be released to drive _____________
reactions by cellular respiration.

Note: the chemical elements are recycled, but the energy is not!
The storage and release of Free Energy

The free energy is __________ and ______________ to ATP (adenosine triphosphate).

Recall, the _______________ bonds have stored energy; ____________ these bonds
releases energy (to drive reactions); while ____________ new phosphate bonds
temporarily stores the chemical energy.

The compound receiving the phosphate group from ATP is said to be
______________________ and becomes more reactive in the process.

The ________________________ compound loses its newly acquired ______________
group as work is performed.

There are two types of phosphorylation:
1.
____________________________ phosphorylation
 an enzyme catalyzed reaction of Pi to ADP
2. ____________________ phosphorylation
 forming of ATP directly through a series of enzyme catalyzed
_________ reactions where oxygen is the ____________________________
(more about this in a bit).
REDOX Reactions Also Release Energy

_____________________________________ reactions = chemical reactions which
involve a partial or complete transfer of electrons from one reactant to another;
called «____________________________ » for short.
1. Oxidation = ____________________________________________________________
2. Reduction = ____________________________________________________________
“LEO says GER”
Loss of electrons = oxidation
Gain of electrons = reduction

The electron transfers require both a ___________ (becomes oxidized) and an
_____________________ (becomes reduced).

Since electrons lose ___________________________ when they shift towards _________
electronegative atoms, redox reactions that move electrons closer to elements with a
higher electronegativity (like oxygen) _______________ energy.

Cellular Respiration is a ___________ process that (ultimately) transfers
_____________________, including electrons with high potential energy, from sugar
(glucose) to _____________________.

Released energy is used to convert ADP to ATP.
How is the energy transferred to a molecule of ATP?

Essentially, glucose is broken down in a series of sequential steps so that the
____________________ released from ________________ bonds can be harnessed
(captured) bit by bit.

Eventually this harnessed free energy is ______________________ to molecules of
ATP as they are phosphorylated (i.e from ADP + Pi  ATP)
Why does the process need to occur in a sequence of steps?

Activation energy = requires extreme heating to start combustion of glucose

Exergonic reation = large amount of energy is released; would damage cells

Therefore, the combustion of glucose occurs by a series of
_______________________________ steps, that result in:

At each step of the way, __________________ (along with electrons) are transferred
to another substance (enzymes & coenzymes) and eventually a final acceptor
(oxygen)

When this happens, a _____________of the reaction’s total energy is released and
stored in ATP (ie. ATP is produced).
An Overview of Cellular Respiration
There are two types:

___________________ respiration (fermentation) = ATP-producing pathway in
which sugars are only partially degraded (low energy yield); proton donors and
acceptors are organic molecules.

__________________ respiration = ATP-producing pathway in which sugar is fully
oxidized (high energy yield); ultimate electron acceptor is oxygen (inorganic
molecule)
Overall Equation:
(Aerobic)
Aerobic Cellular Respiration occurs in four stages:
1.
2.
3.
4.
Glycolysis
pyruvate oxidation (occurs only in eukaryotic cells)
Citric Acid or Kreb’s Cycle
Electron Transport Chain (ETC)
Glucose + oxygen  carbon dioxide + water + energy
C6H12O6 + 6O2  6CO2 + 6H2O + 38 ATP (total)
Breaking down
glucose to get H+
(and electrons)
Using H+ (and
electrons) by releasing
them slowly 
trapping released
energy in ATP
Stepwise fall of Electrons

occurs due to special electron acceptors (______ and ______) and the
______________________________________.

_______________ (and electrons) stripped from glucose are NOT transferred
directly to oxygen, but are first passed to a special electron acceptor  ex. NAD+
NAD+ (nicotinamide adenine dinulceotide) and FAD (flavin adenine dinucleotide =
are dinucleotides that function as a coenzyme in the redox reactions of metabolism.
NAD+ and FAD
 are found in all cells
 assist enzymes in electron transfer during redox reactions
What happens?
 During the ____________________ of glucose, the electrons are ________________
and temporarily trapped in NAD+ and FAD.

This transferred is catalyzed by enzymes called ______________________, which:
o remove a pair of hydrogen atoms (2 electrons and 2 protons) from
glucose (substrate)
o deliver the two electrons (______) and one proton (______) to NAD+ (or 2eand 2H+ to ________)
o ____________ the remaining proton (H+) into the surrounding solution.
Overall reactions:

The high energy electrons transferred to NAD+ and FAD are then passed down
the _______________________________ to oxygen, powering the production of ATP
by oxidative phosphorylation.
Electron Transport Chains

Consist of ____________________________ molecules built into cellular membranes

_____________ energy rich electrons from reduced coenzymes (NADH and FADH2)

Since electrons lose potential energy when they are transferred to a more
electronegative atom, this series of reactions _______________ energy.

______________ energy from energy-rich electrons in a controlled stepwise fashion
 powering the production of ATP

Each successive carrier in the chain has a ____________ electronegative then the
carrier before, so the electrons are pulled downhill towards ________________ (the
molecule with the ______________ electronegativity), and the final electron
______________.