Download Cellular Respiration

Metabolic Pathways
1. Substrates are substances that enter
reactions
2. Intermediates are the compounds formed
between the start and the end of a pathway.
3. Enzymes are proteins that catalyze (speed up)
reactions
4. Cofactors are small molecules and metal ions
that help enzymes by carrying atoms or
electrons.
5. Energy carriers are mainly ATP
6. End products are the substances present at
the conclusion of a pathway.
Introduction to Cellular Respiration
• Cellular Respiration
– Aerobic harvesting of energy from food
molecules
– Rearrangement of atoms during chemical
reactions releases the potential energy
– Generating ATP for cellular work
ATP
• Powers nearly all forms of cellular work
• Adenosine Triphosphate
– Adenine
• Nitrogenous base
– Ribose
• Five carbon sugar
– Tri-phosphate tail
• Three phosphates (business end)
• Potential energy stored in bonds
– Triphosphate chain equivalent to a
compressed spring
– ATP ADP (releasing P releases energy)
• Phosphorylation:
– Transfer of a phosphate group (usually from an
ATP molecule) to a molecule
• ATP is a renewable source of energy
Cellular Respiration
• Chemical energy released from bonds of
food molecules and stored in bonds of ATP
• Produces 38 ATP molecules per Glucose
molecule
– 40% of energy in glucose
– The rest released as heat
Vocabulary
• Redox Reaction: Movement of electrons
from one molecule to another
– Oxidation: Loss of electrons from one
substance
– Reduction: addition of electrons to a substance
Cellular Respiration
• Three Steps:
– Glycolysis
• Occurs in cytoplasm
– Citric Acid Cycle (Krebs Cycle)
• Takes place in the mitochondria
**Minimal ATP made 1st two stages
• They supply electrons to third stage
– Electron Transport Chain
• Inner membrane of the mitochondria
• Energy from electrons used to generate ATP
Key Players
• ATP
• NAD+ and FAD
– Shuttle electrons in redox reactions
• (dump trucks)
• Key Reactions
– Substrate-level phosphorylation
• Phosphate transferred from substrate to ADP;
forming ATP
– Oxidative phosphorylation
Substrate-Level
Phosphorylation
Glycolysis
• Glucose split
– two three carbon molecules
– this requires 2 ATP molecules (investment)
• Each three carbon molecule transfers
electrons and H+ to carrier molecule
– NAD+  NADH
• Four ATP molecules made (payback)
– Three carbon molecules converted to pyruvate
Glycolysis
Section 9-1
Glucose
1. Glucose enters the cell
Go to
Section:
2 Pyruvic acid
To the electron
transport chain
Glycolysis
Section 9-1
Glucose
2 Pyruvic acid
2. 2 ATP are used to split glucose apart to form two 3 carbon molecules call PEP
Go to
Section:
Glycolysis
Section 9-1
Glucose
2 Pyruvic acid
3. 4 ADP pick up energy to form 4 ATP
4. 2 NAD+ pick up electrons to form NADH
To the electron
transport chain
5. The ATP formed can now be used for normal cellular function
6. Pyruvate moves into the mitochondria and Krebs cycle
Go to
Section:
Glycolysis
Don’t get caught up in the details!!
• The splitting of sugar
• **What goes in:
– Glucose
– 2 ATP
• **What comes out
– 2 pyruvate molecules
– 4 ATP (Net of 2)
– 2 NADH (electron carrier)
Krebs Cycle
Pyruvate gets broke down to CO2, ATP,
NADH, FADH2
Takes place in the mitochondria
• Oxygen is required.
• Pyruvic acid enters the mitochondria.
carbon)
(3
– 1 carbon kicks off to form carbon dioxide.
– 2 remaining carbons form Acetyl-CoA join a 4 carbon
molecule to form citric acid (6 carbons).
– 1 carbon is kicked off to form carbon dioxide
(5 carbon molecule)
– 1 carbon is kicked off to form carbon dioxide (4
carbon molecule)
• This 4 carbon molecule is then ready to
accept another 2 carbon Acetyl-CoA group,
which starts the cycle all over again.
• 1(2) ATP molecule
• 4 (8)NADH molecules
• 1 (2)FADH molecule
• 3 (6)Carbon dioxides
Section 9-2
The Krebs
Cycle
Citric Acid
Production
Mitochondrion
Go to
Section:
Section 9-2
The Krebs
Cycle
Citric Acid
Production
Mitochondrion
Go to
Section:
The Citric Acid Cycle
(Stage Two)
• Per Glucose molecule:
• What goes in:
– 2 Pyruvate 2 Acetyl-CoA
– 6 NAD+ *
– 2 FAD
• What comes out:
– 8 NADH
– 2 FADH2
– 2 ATP
– 6 CO2
Electron Transport Chain
• Oxidative Phosphorylation
• Requires Oxygen.
• The high energy electrons from NADH and FADH
produced in the krebs cycle and glycolysis are passed to
the electron transport chain.
• 2 high energy electrons are transported down the chain
from carrier to carrier through redox reactions
• Energy from electrons actively transports H+ ions across
inner membrane of the mitochondria
• H+ ion gradient stores potential energy
• H+ ions diffuse back across membrane due to
concentration gradient
• Membrane not permeable to H+ ions
• They move across through a channel called ATP
Synthase
• As they move through, the channel uses energy from the
flow of H+ to convert ADP to ATP
• Each pair of high energy electrons that move down the
electron transport chain provides enough energy to
convert 3 ADP molecules into 3 ATP molecules.
• At the end of the transport chain an enzyme combines
electrons with hydrogen and oxygen to form water
– Oxygen is the final electron acceptor
Electron Transport
Chain
Section 9-2
Electron Transport
Hydrogen Ion Movement
Channel
Mitochondrion
Intermembrane
Space
ATP synthase
Inner
Membrane
Matrix
ATP Production
Go to
Section:
Anaerobic Respiration