Cell Respiration

1
Cell Respiration
2
Harvesting Chemical Energy

• ATP--main fuel for cells
• Cellular Respiration--process cells use to make
  ATP by breaking down organic compounds

3
The Big Picture
4
Cellular Respiration An Overview
5
The Cell Respiration Equation

• 6O2 C6H12O6 6CO2 6H2O Energy
• oxygen sugar carbon dioxide water energy

6
Glycolysis
Glucose
2 Pyruvic acid
7
Glycolysis

• The process of breaking 1 molecule of glucose in
  half
• Happens in the cytoplasm
• Produces pyruvic acid and NADH
• Produces 4 ATPs overall
• 2 ATPs used up to in the reaction
• Net gain 2 ATPs

8
NAD and NADH

• NAD is a carrier molecule, it becomes NADH when
  it picks up energy (an electron)
• It is similar to NADPH, used in photosynthesis
• Carries high energy electrons to other places
  they are needed in the cell

9
Glycolysis

• This is a FAST process
• Thousands of ATPs can be produced in a few
  milliseconds
• However, there are a limited number of NAD
  carriers, so more must be made
• Without additional NAD, glycolysis cannot
  continue

10
The Big Picture
11
Oxygen or No Oxygen??

• The next step of cell respiration depends on
  whether or not oxygen is available
• If no oxygen, then the next step is called
  FERMENTATION
• Fermentation is an anaerobic process
• Two types of fermentation--alcoholic fermentation
  and lactic acid fermentation

12
Alcoholic Fermentation

• Yeasts and a few other microorganisms use this
• pyruvic acid NADH --gt alcohol CO2 NAD
• Used to produce bread,
• wine, beer,
  homeade rootbeer, etc.

The holes in bread are from pockets of CO2 that
got trapped.
13
Lactic Acid Fermentation

• This type of fermentation happens in your
  muscles, and also in certain microorganisms
• pyruvic acid NADH --gt lactic acid NAD

Used to produce cheese, yogurt, soy sauce,
sauerkraut, etc. Lactic acid gives these things
the sharp, sour taste. YUMMMMY!
14
Lactic Acid Fermentation

• This is also the reason for runners fatigue
  or cramps
• When exercising strenously, your muscle
  cells use up all your oxygen and
  must switch to lactic acid
  fermentation
• Lactic acid burns when it builds
  up inside the cells

15
Lactic Acid Fermentation

• Since NAD is produced
• pyruvic acid NADH --gt
  lactic acid NAD
• glycolysis can continue and
  more ATP can be made

16
Cellular Respiration in the presence of Oxygen
KrebsCycle
ElectronTransportChain
Carbon Dioxide (CO2) Water (H2O)
Glucose(C6H1206) Oxygen(02)
Glycolysis
17
After Glycolysis...

• Most of the energy in glucose is still not
  released even after glycolysis
• Oxygen is needed to release the remaining energy
  from the glucose molecule
• The next step is called the Krebs Cycle (if
  oxygen is available)

18
The Krebs Cycle
19
Krebs Cycle

• What goes IN? pyruvic acid from glycolysis
• Where? Mitochondrial matrix (space inside the
  inner membrane of mitochondria)
• What comes OUT? NADH and FADH2 (both are carrier
  molecules for high energy electrons). These go
  to the next step of cellular
  respiration...

20
Krebs Cycle

• When pyruvic acid enters mitochondria, it reacts
  with coenzyme A to make acetyl CoA releases
  CO2

christae
21
Krebs Cycle

• 5 Major Steps
• 1) combines with oxalocetic acid to form citric
  acid
• 2) releases CO2 and NAD to NADH
• 3) CO2 released and NAD to NADH, also ATP
  synthesized
• 4) FAD (carrier molecule) to FADH2
• 5) NAD to NADH, more oxalocetic acid created

22
The Krebs Cycle
5 Major Steps 1) combines with oxalocetic acid
to form citric acid 2) releases CO2 and NAD to
NADH 3) CO2 released and NAD to NADH, also ATP
synthesized 4) FAD (carrier molecule) to
FADH2 5) NAD to NADH, more oxalocetic acid
created

23
Electron Transport Chain
Mitochondrion
24
Electron Transport Chain

• What goes IN? NADH and FADH2 from Krebs Cycle
• Where? Inner membrane of mitochondria
• What comes OUT? Lots and lots of ATP
  molecules!!!! (34 to be exact)

25
Electron Transport Chain
Electron Transport
Hydrogen Ion Movement
Channel
Mitochondrion
Intermembrane Space
ATP synthase
Inner Membrane
Matrix
ATP Production
26
Electron Transport Chain

• High energy electrons are passed from NADH and
  FADH2 along a series of molecules
• As they go from molecule to molecule, they lose
  their energy. It is used to pump H into the
  space between inner and outer mitochondrial
  membrane.

27
Electron Transport Chain

• Chemiosmosis takes place, H ions diffuse from
  high to low through ATP synthase
• As the ATP synthase spins, this generates ATP
  molecules
• Sound familiar?

28
Electron Transport Chain

• Oxygen is the final electron acceptor in this
  reaction
• This gets rid of low energy electrons and extra
  H ions
• Byproduct that results is H2O

29
The Totals (Net Gains)

• Glycolysis Fermentation 2 ATP
• Glycolysis Krebs ETC 36 ATP
• Even 36 ATP is only about 66 of the energy
  available in one glucose molecule. Where does
  the rest of the energy go???

QUESTION
30
ANSWER

• The remaining 34 is given off as body heat
  (keeps you warm in this chilly room!)

31
Pacing Yourself

• Fermentation--used during strenuous exercise
  (fast breakdown of sugar)
• Krebs Cycle and ETC--used during longer, paced
  exercises (like long-distance running) Slower,
  but more energy released

32
Why do runners breathe heavily after a race?
Question
33
They are repaying the oxygen debt they have
built up!
Answer
34
The BIGGEST Picture of All !!!

• Photosynthesis--removes CO2 from the atmosphere,
  puts back O2
• Cellular Respiration--removes O2 from the
  atmosphere, puts back CO2

6H2O 6CO2 light energy? C6H12O6 6O2
6O2 C6H12O6 ? 6CO2 6H2O Energy