Download Cellular Respiration

Cellular Respiration
What is Cellular Respiration?

The process of converting food energy into ATP
energy

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + 36 ATP
Why are both Photosynthesis and Cell
Respiration important to Ecosystems?



Light is the ultimate source
of energy for all ecosystems
Chemicals cycle and Energy
flows
Photosynthesis and cellular
respiration are opposite
reactions
Why do plants need both chloroplasts and
mitochondria?


Chloroplasts use
energy from the sun to
make glucose
Mitochondria convert
glucose to ATP—the
energy currency of the
cell
http://www.wiley.com/legacy/college/bo
yer/0470003790/animations/metabolis
m/metabolism.htm
What is ATP?

Adenosine Triphosphate
 5-Carbon sugar (Ribose)

Nitrogenous base (Adenine)
 3 Phosphate groups

Energy currency of the cell

The chemical bonds that link the
phosphate groups together are
high energy bonds

When a phosphate group is
removed to form ADP and P,
small packets of energy are
released
How is ATP used?

As ATP is broken down, it gives off
usable energy to power chemical
work and gives off some
nonusable energy as heat.

Synthesizing molecules for growth
and reproduction
Transport work – active transport,
endocytosis, and exocytosis
Mechanical work – muscle
contraction, cilia and flagella
movement, organelle movement


Why use ATP energy and not energy from
glucose?

Breaking down glucose yields too much energy for cellular
reactions and most of the energy would be wasted as heat.


1 Glucose = 686 kcal
1 ATP = 7.3 kcal
1 Glucose → 36 ATP

How efficient are cells at converting glucose into ATP?


38% of the energy from glucose yields ATP, therefore
62% wasted as heat.
Cell Respiration can be divided into 4 Parts:
1) Glycolysis
2) Pyruvate to Acetyl CoA
3) The Krebs Cycle
4) The Electron Transport Chain and
ATP production
Where do the 4 parts of Cellular
Respiration take place?

Glycolysis:


Pyruvate to Acytyl
CoA:


Matrix
The Krebs Cycled:


Cytosol
Matrix
Electron Transport
Chain and Production
of ATP:

Cristae
Parts of the Mitochondria
Glycolysis
Glucose
2 ATP

2 Pyruvate
4 ATP (Net 2 ATP)
2 NADH
Glucose (C6) is split to
make
2 Pyruvates (C3)

Glycolysis produces
very little ATP energy,
most energy is still
stored in Pyruvate
molecules.
Pyruvate To Acetyl CoA
2 Pyruvate

2 CO2
2 NADH
2 Acetyl CoA

When Oxygen is present, 2
Pyruvates go to the matrix
where they are converted
into 2 Acetyl CoA (C2).

2 NADH’s carry electrons
and hydrogens to the
Electron Transport Chain.

CO 2 is given off
The Krebs Cycle / Citric Acid Cycle
2 Acetyl CoA

4 CO2
2 ATP
6 NADH
2 FADH2
8 Enzymatic Steps in Matrix of
Mitochondria: Two Turns of the
Krebs Cycle are required to break
down both Acetyl Coenzyme A
molecules.
The Krebs cycle produces some
chemical energy in the form of ATP
but most of the chemical energy is
in the form of NADH and FADH2
which then go on to the Electron
Transport Chain.
The Electron Transport Chain
10 NADH
2 FADH2
Oxygen




32 ATP
H2O
NADH and FADH2 produced
earlier, go to the Electron Transport
Chain.
NADH and FADH2 release
electrons to carriers/proteins
embedded in the membrane of the
cristae. As the electrons are
transferred, H+ ions are pumped
from the matrix to the
intermembrane space up the
concentration gradient. Electrons
are passed along a series of 9
carriers until they are ultimately
donated to an Oxygen molecule.
½ O2 + 2 electrons + 2 H+ (from
NADH and FADH2) → H2O.
http://vcell.ndsu.nodak.edu/animations/etc/movie.htm
Chemiosmotic Phosphorylation




Hydrogen ions travel down their concentration gradient through a channel protein coupled
with an enzyme called ATP Synthase.
As H+ ions move into the matrix, energy is released and used to combine ADP + P →
ATP.
Hydrogens are recycled and pumped back across the cristae using the Electron Transport
Chain.
ATP diffuses out of the mitochondria through channel proteins to be used by the cell.
http://vcell.ndsu.nodak.edu/animations/atpgradient/movie.htm
ATP Synthase

Multisubunit complex with
4 parts:




Rotor – spins as H+ ions flow
Stator – holds the rotor and knob
complex together in the cristae
Internal Rod – extends between
rotor and knob, spins when rotor
spins which then turns the knob
Knob – contains 3 catalytic sites that
when turned change shape and
activate the enzyme used to make
ATP
Review ATP Production:
1) Glycolysis → 2 ATP
2) Pyruvate to Acetyl CoA → No ATP
3) The Krebs Cycle → 2 ATP
4) The Electron Transport Chain and Chemiosmotic
Phosphorylation:

Each NADH produces 2-3 ATP so 10 NADH
→ 28 ATP

Each FADH2 produces 2 ATP so
2 FADH2
→ 4 ATP
Total = 36 ATP




1 Glucose = 686 kcal
1 ATP = 7.3 kcal
1 Glucose → 36 ATP
How efficient are cells at converting glucose into
ATP?

38% of the energy from glucose yields ATP,
therefore 62% wasted as heat (used to
maintain body temperature or is dissipated)

Ex. Most efficient Cars: only 25% of the
energy from gasoline is used to move the car,
75% heat.
All Types of Molecules can be used to
form ATP by Cell Respiration:

Proteins, Carbohydrates, and
Lipids must first be broken
down into their monomers and
absorbed in the small intestine.

Monomers may be further
broken down into intermediate
molecules before entering
different parts of Cell
respiration to ultimately form
ATP.
Anaerobic Respiration: Fermentation



If there is NO oxygen, then cells can make ATP by Fermentation
Without oxygen, Oxidation of Pyruvate and the Electron Transport
Chain do not operate.
Glucose
→ Pyruvate
→
NAD+ Glycolysis
2 NADH
2 ATP
Lactate
or
Alcohol + CO2
Fermentation yields a net gain of 2 ATP for every 1 Glucose. (Inefficient)
Two Forms of Fermentation:
Lactic Acid Fermentation (animals)
Alcohol Fermentation (yeast)
Lactic Acid Fermentation
Alcoholic Fermentation