Download Cellular Respiration

Cellular Respiration
Where do animal cells get their energy?
Remember
• Energy used by
all Cells.
• Organic
molecule
containing highenergy
Phosphate bonds
How Do We Get Energy From ATP?
By breaking
the highenergy
bonds
between the
last two
phosphates
in ATP
Cellular Respiration
The process of cell catabolism in which cells turn food into usable energy in the form of ATP. In this
process glucose is broken down in the presence of molecular oxygen into six molecules of carbon
dioxide, and much of the energy released is preserved by turning ADP and free phosphate into
ATP. Cellular respiration occurs as a series of chemical reactions catalyzed by enzymes, the first of
which is glycolysis, a series of anaerobic reactions in which glucose (a 6-carbon molecule) is split
into two molecules of lactate (a 3-carbon molecule), producing a net gain of two ATP molecules.
In a series of aerobic reactions, lactate is converted to pyruvate, which enters the mitochondrion
and combines with oxygen to form an acetyl group, releasing carbon dioxide. The acetyl group
(CH 3 CO) is then combined with coenzyme A as acetyl coenzyme A, and enters the Krebs cycle.
During this series of reactions, each acetyl group is oxidized to form two molecules of carbon
dioxide, and the energy released is transferred to four electron carrier molecules. The electron
carrier molecules then release their energy in a process that results in the pumping of protons
(hydrogen ions) out across the inner membrane of the mitochondrion. The potential energy of the
protons generated by one acetyl group is later released when they recross the membrane and
are used to form three molecules of ATP from ADP and phosphate in the process of oxidative
phosphorylation. The pyruvate from one molecule of glucose drives two turns of the Krebs cycle.
Thus, during cellular respiration one molecule of glucose, as well as oxygen, ADP, and free
phosphate are catabolized to yield six molecules of carbon dioxide and an increase in usable
energy in the form of eight molecules of ATP.
 Glycolysis: the breakdown of glucose by enzymes,
releasing energy and pyruvic acid.
Pyruvic Acid: organic acid that occurs as an
intermediate in many metabolic processes, especially
glycolysis
 Anaerobic Respiration: A form of cellular respiration that
occurs when oxygen is absent or scarce. The process of
generating energy by the oxidation of nutrients and using
an external electron acceptor other than oxygen.
 Fermentation: enzymatically controlled anaerobic
breakdown of an energy-rich compound
 Aerobic Respiration: A form of cellular respiration that
requires oxygen in order to generate energy. The process of
generating energy by the full oxidation of nutrients through
Krebs cycle where oxygen is the final electron acceptor.
Where Does Cellular Respiration Take Place?
It actually
takes place in
two parts of
the cell:
* Glycolysis occurs in the
Cytoplasm
* Krebs Cycle & ETC Take
place in the Mitochondria
Review of Mitochondria Structure
Smooth outer
Membrane
Folded inner
membrane
Folds called Cristae
Space inside
cristae called the
Matrix
Explain:
Where do our cells get energy?
6-C sugars are the MAJOR source of
energy for cell
What type of macromolecule are 6-C
sugars?
Carbohydrates
Cells break down glucose a 6-C sugar
to make ATP “energy”
6 Carbon Sugars: They even count the
sugars for you…
Cellular Respiration (3-stages)
Glycolysis
Krebs Cycle (Citric Acid Cycle)
Electron Transport Chain (ETC)
Glucose
Glucose
Glycolysis
Glycolysis
Krebs
cycle
Fermentation
(without oxygen)
Electron
Transport
Electron
Krebs
transport
Cycle
Fermentation (without oxygen)
Alcohol or
lactic acid
Alcohol or
lactic acid
Overall Chemical Process
C6H12O6 + 6O2  6CO2 + 6H2O + usable energy
Sugar
+ Oxygen  Carbon dioxide + Water + ATP
Flowchart of Cellular Respiration 
Glucose
(C6H1206)
+
Oxygen
(02)
Glycolysis
Krebs
Cycle
Electron
Transport
Chain
Carbon
Dioxide
(CO2)
+
Water
(H2O)
+
ATP
Glycolysis
Where Cytoplasm
NO O2 required
Energy Yield net gain of 2 ATP at the
expense of 2 ATP
6-C glucose  TWO 3-C pyruvates
Free e- and H+ combine with organic ion
carriers called NAD+  NADH + H+
(nicotinamide dinucleotide)
Glycolysis:
Glucose
2 Pyruvic acid
To the electron
transport chain
Glycolysis step 1
Glucose
2 Pyruvic acid
To the electron
transport chain
Glycolysis Step 2
Glucose
2 Pyruvic acid
To the electron
transport chain
C.R. Reactions
Glycolysis
Series of reactions which break the 6carbon glucose molecule down into two 3carbon molecules called pyruvate
Process is an ancient one-all organisms
from simple bacteria to humans perform it
the same way
Yields 2 ATP molecules for every one
glucose molecule broken down
Yields 2 NADH per glucose molecule
Summary
In
Glucose (6-C)
2 ATP
Out
2 pyruvate; 2(3C)
2NADH
a net of 2 ATP
Questions
Where does glycolysis take place?
____________________________________________
It needs _______ ATP to work.
It provides _______ ATP a net gain of _______.
Breaks glucose into TWO ___________.
It is an Aerobic or Anaerobic process?
After Glycolysis
After glycolysis, about 90 percent of
the energy in glucose is still unused.
Oxygen is required to extract the rest
of the energy (aerobic process).
Still Need a review? Click on the picture.
Aerobic Cellular Respiration
Oxygen required=aerobic
2 more sets of reactions which occur in a
specialized structure within the cell called the
mitochondria
1. Kreb’s Cycle
2. Electron Transport Chain
Krebs Cycle aka Citric Acid Cycle
A Little Krebs Cycle History
Discovered by Hans Krebs in 1937
He received the Nobel Prize in
physiology or medicine in 1953 for his
discovery
Forced to leave Germany prior to
WWII because he was Jewish
The Krebs Cycle
Citric Acid
Production
Mitochondrion
Kreb’s Cycle
Completes the breakdown of glucose
Takes the pyruvate (3-carbons) and breaks
it down, the carbon and oxygen atoms
end up in CO2 and H2O
Hydrogens and electrons are stripped and
loaded onto NAD+ and FAD to produce
NADH and FADH2
Production of only 2 more ATP but loads up
the coenzymes with H+ and electrons which
move to the 3rd stage
Krebs Cycle
Requires Oxygen (Aerobic)
Cyclical series of oxidation reactions that
give off CO2 and produce one ATP per cycle
Turns twice per glucose molecule
Produces two ATP
Takes place in matrix of mitochondria
Review of Mitochondria Structure
Smooth outer
Membrane
Folded inner
membrane
Folds called Cristae
Space inside
cristae called the
Matrix
Krebs Cycle
Each turn of the Krebs Cycle also
produces 3 NADH, 1 FADH2, and 2 CO2
Therefore, For each Glucose
molecule, the Krebs Cycle produces
6 NADH, 2 FADH2, 4 CO2, and 2 ATP
First Step: Krebs Cycle/Citric Acid Cycle
Breakdown of Pyruvic Acid
Where mitochondria matrix
Pyruvate (3-C)  Acetic acid (2-C)
3rd C forms CO2
Acetic acid combines with
Coenzyme A to form ACETYL-CoA
Summary
In
Out
Pyruvate
CO2 (as waste)
NAD
NADH
CoA
Acetyl-CoA
What is releasing Energy with O2?
Aerobic respiration
Where In the cells mitochondria
Second Step: Krebs Cycle or Citric Acid Cycle
Where Mitochondrial matrix
Energy Yield 2 ATP and more eAcetyl-CoA (2-C) combines with 4-C to form
6-C CITRIC ACID
Citric Acid (6-C) changed to 5-C then to a
4-C
Gives off a CO2 molecule
NAD+ and FAD pick up the released eFAD becomes FADH2
NAD+ becomes NADH + H+
Cycle ALWAYS reforming a 4-C molecule
Krebs Cycle
Still Need a review? Click on the picture.
Citric
Acid
Producti
on
Mitochondrion
Electron Transport Chain
Aka ETC
Electron Transport Chain
Electron carriers loaded with electrons and
protons from the Kreb’s cycle move to this
chain-like a series of steps (staircase).
As electrons drop down stairs, energy
released to form a total of 34 ATP
Oxygen waits at bottom of staircase, picks
up electrons and protons and in doing so
becomes water
ETC
Where inner membrane of mitochondria
Energy Yield Total of 34 ATP
O2 combines with 2 H+ to form H2O
Exhale (waste product) - CO2, H2O comes
from cellular respiration
Electron Transport Chain
Electron Transport
Mitochondrion
Hydrogen Ion Movement
Channel
Intermembrane
Space
ATP
synthase
Inner
Membrane
Matrix
ATP Production
Other ETC videos
 http://www.science.smith.edu/departments/Biology/Bio231/etc.html
So where did all the ATP come
from again…
Total ENERGY Yield
Glycolysis 2 ATP
Krebs Cycle 2 ATP
ETC  34 ATP
Total 38 ATP
What happens if no O2?
Cellular respiration process STOPS…
but life needs to go on …
Anaerobic respiration
Fermentation
 Anaerobic respiration (requires no oxygen)
 Only 2 ATP are made in anaerobic respiration
so it is not as good as aerobic respiration (34
ATP)
 Both begin with glycolysis (remember this
process was anaerobic.)
 No Krebs (citric acid) cycle or electron
transport chain
Two Types of Fermentation
Alcoholic Fermentation
-
Used by yeasts and a few other micro-organisms
with ethyl alcohol and carbon dioxide as waste
products.
-
Causes bread to rise.
Lactic Acid Fermentation
- Lactic acid is produced from pyruvic
acid.
- Produced in muscles during rapid
exercise when enough oxygen is not
present.
- Unicellular organisms also produce
lactic acid as a waste product.
- Prokaryotes are used in the production
of cheese, yogurt, buttermilk, sour
cream, pickles, sauerkraut, and kimchi.
Anaerobic Respiration
Glycolysis
Glucose
Pyruvate + 2 ATP
Followed by one of these 2 processes.
Alcoholic Fermentation
Pyruvate
ethyl alcohol + CO2
- Carried out by yeast & some
bacteria.
-Used in brewing beer &
making cakes.
Only 2 ATP are
made in anaerobic
respiration so it is
not as good as
aerobic respiration
(38 ATP).
Lactic Acid Fermentation
Pyruvate
Lactic Acid
-Carried out by your muscle
cells when you are exercising
hard (need ATP)
-Causes muscle cramps &
soreness.
Aerobic vs. Anaerobic
Anaerobic DOES
NOT require oxygen.
It is …
 Simple
Aerobic DOES
requires oxygen
It…
 fast
 Yields large amounts
of energy
 produces smaller
amounts of energy
But is not simple, fast
or efficient
What is the energy molecule that is created?
ATP
Releasing Energy with out Oxygen
Anaerobic Respiration
NO Additional ATP is Formed
No Oxygen leads to Fermentation
Two Types
Lactic Acid Fermentation
Alcoholic Fermentation
What are the 2 chemical equations?
Alcoholic fermentation
 pyruvic acid + NADH → alcohol + CO₂ + NAD⁺
Lactic acid fermentation
 pyruvic acid + NADH → lactic acid + NAD⁺
What are the differences?
Review Time…
Step 1 Glycolysis occurs in the cytoplasm.
Glucose
ATP
Glycolysis
Pyruvate
Pyruvate
ATP
Energizes 2 electron carriers.(NAD+
NADH)
Glucose is broken in half to form two pyruvate molecules.
A small amount of energy (ATP) is also produced.
Step 2: Kreb’s Cycle (Citric Acid Cycle) occurs
inside the mitochondria.
ATP
ATP
Pyruvic
Acid
Kreb’s Cycle
Citric Acid
e-
e-
NADH
e-
CO2
Kreb’s Cycle/ Citric Acid Cycle cont…
- 3 Products from Kreb’s Cycle…
1. Carbon Dioxide released (like in your
breath).
2. ATP provides energy for cellular
activities.
3. High-energy electron (carried by
electron carriers) that can be used to
generate large amounts of ATP.
Step 3: Electron transport chain occurs in the
mitochondria.
Electrons move down the
electron transport chain.
NADH
e-
e34ATP
Electrons are caught by
oxygen to make water.
e34 ATP are also made.
Oxygen we breathe
We use for
energy
Water
Electron Transport Chain
- Uses the high-energy electrons from the
Kreb’s cycle to convert ADP to ATP.
- Electrons are passed from one carrier protein
to the next and finally combine with
hydrogen ions & oxygen to form water.