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Transcript
How do our cells and other living
organisms get energy from organic
polymers (i.e. food)?
Cellular Respiration (2.8/8.2)
Review:
• How ventilation and gas exchange different
from respiration?
• What are redox reactions?
• What is phosphorylation?
HL Only:
• What is carboxylation?
• What is chemiosmosis?
Oxidation-Reduction (Redox) Reactions in
Cellular Respiration
“OIL
”
• Removal of hydrogen
• Addition of oxygen
“RIG”
• Addition of hydrogen
• Removal of oxygen
Why cellular respiration?
• All living organisms respire to produce ATP
(adenosine triphosphate) from organic molecules
• ATP is used for cellular processes– energy stored
in chemical bonds
• In plants, cellular respiration is dependent upon
the end-products produced in photosynthesis
• Breathing is NOT respiration (aerobic respiration
requires oxygen – i.e. purpose of ventilation and
gas exchange)
Definition & Chemical Equation for
Cellular Respiration
Definition: controlled release and conversion of
chemical energy stored in carbon compounds
to ATP
Role of Enzymes in Respiration
• Metabolic pathway controlled by enzymes ; rate
controlled by end product inhibition (Amount of ATP
determines rate of reaction ; if there is adequate
supply of ATP, ATP will block the attachment of more
substrate)
• ATP binds to the allosteric site of the starting enzyme
(binding site for non-substrates)
Which has more mitochondria? Why?
Muscle Cell Micrograph
Skin Cell Micrograph
What is the structure of the mitochondria?
Structure of
Mitochondria
Ex: ATP Synthase
What are the 4 stages of aerobic respiration?
Where does each stage occur?
• Glycolysis
occurs in the
cytoplasm
• The Link
Reaction occurs
in the matrix
• The Krebs Cycle
occurs in the
matrix
• The ETC occurs
along the inner
membrane
• Glycolysis can occur
with or without
oxygen (aerobic or
anaerobic
respiration)
• Yields a small
amount of ATP
• Produces pyruvate,
which can be further
broken down to
lactate OR ethanol
(fermentation)
Why can’t we just keep doing
anaerobic respiration?
• Ethanol and lactic acid products can become toxic
• Production of ethanol is not reversible. If levels get
too high it will kill the organism.
• Lactic acid can be reversible, but requires oxygen.
• Oxygen debt – lack of oxygen that needs to be
repaid in order to convert lactic acid into carbon
dioxide and water (this is why we continue
breathing deeply and frequently after we’ve
already stopped exercise)
•
Source: http://ibbiologyhelp.com/OptionB/oxygendebt.png
4 Stages of
Glycolysis
(glycol = sugar ;
lysis =splitting)
1. Phosphorylation
of Glucose
2. Lysis
3. Oxidation of T.P.
4. Formation of
ATP
Animation:
http://highered.mheducation.com/sit
es/0072507470/student_view0/chap
ter25/animation__how_glycolysis_w
orks.html
1
2
3
4
• Step 1 - Glucose is phosphorylated (two phosphate groups
are added to glucose to form hexose biphosphate). These
two phosphate groups are provided by two molecules of
ATP.
• Step 2 - Lysis of hexose biphosphate. Hexose biphosphate
splits into two molecules of triose phosphate.
• Step 3 - Each triose phosphate molecule is oxidized
(hydrogens and electrons are removed from each molecule).
NAD+ accepts the electrons and hydrogen lost by TP, and
gets reduced to NADH. Energy is released from the oxidation
of each molecule of TP.
• Step 4 – The energy released by the oxidation of TP is used to
phosphorylate two molecules of ADP. Two pyruvate
molecules are formed by removing two phosphate groups
from each molecule. These phosphate groups are given to
ADP molecules and form ATP.
Products and (Summary) of
Glycolysis:
• ONE glucose is converted
into TWO pyruvates.
• A net yield of TWO ATP
molecules
• TWO NAD+ are reduced to
+
Oxidation in Glycolysis
• Two atoms of hydrogen are removed from each
triose phosphate molecule. This is oxidation.
• These two atoms of hydrogen are added to
NAD+ to make NADH & H+. This is reduction.
Link Reaction by Oxidative decarboxylation
• Occurs in
mitochondrial matrix
• Pyruvate is converted
to acetyl CoA through
oxidative
decarboxylation and
combination with
coenzyme A
• Oxidation = loss of
hydrogen/electrons
• Decarboxylation =
removal of CO2
• Acetyl CoA and NADH
are used in the Krebs
Cycle
The Krebs Cycle
• Acetyl CoA (2C) is combined with a
4C compound (oxaloacetate) to
make a 6C intermediate (citrate),
which is broken down in a series of
reactions to reform the 4C
compound
Reaction Types:
• Decarboxylation: CO2 is removed
and excreted as waste
• Oxidations: hydrogens are
removed and accepted by NAD
and FADH ; energy released is
stored in hydrogen carriers
• Substrate-level phosphorylation:
ATP is produced
• Link Reaction and Krebs Cycle Animation:
http://highered.mheducation.com/sites/0072507470
/student_view0/chapter25/animation__how_the_kre
bs_cycle_works__quiz_1_.html
(Oxaloacetate)
•2 molecules
of CO2 are
released
•NADH &
FADH2 are
sent to the
ETC
(Citrate)
The ETC and Oxidative Phosphorylation
•Electrons are brought to
the chain by NADH and
FADH2, and move through
protein complexes to
release energy
•Energy from the
movement of electrons is
used to pump H+ ions in to
the intermembrane space
to produce a concentration
gradient for chemiosmosis
•ATP Synthase is used to
generate energy for
phosphorylation of ADP
The Role of Oxygen in Aerobic Respiration
•Oxygen = “terminal electron acceptor”
•Oxygen accepts electrons at the end of the ETC and H+ ions
to form water as a byproduct of aerobic respiration
IB Prompt: Explain oxidative phosphorylation in terms
of chemiosmosis
• Oxidative phosphorylation involves using energy from
the oxidation of hydrogen carriers (NADH / FADH2) to
phosphorylate ADP, and make ATP.
•Energy is generated as electrons move through the
electron transport chain, and is used to pump hydrogen
ions (H+) from the matrix into the intermembrane space
•This generates a concentration gradient which drives the
hydrogen ions back into the matrix through enzymes
called ATP Synthase.
•ATP synthase uses energy generated by the movement of
H+ ions to make ATP from ADP; this process of making ATP
by the movement of H+ is called chemiosmosis.