section 2, chapter 4
TRANSCRIPT
Chapter 4, Metabolism…continued
Section 2, Chapter 4
Mitochondria
Oxidation- transfer of electrons away from a molecule. Glucose is oxidized in cell respiration. Energy from the transfer of e- away from glucose is used to make ATP.
Initial fuel or energy source
Overview of Cell Respiration
ATP = energy currency used by cells
Glucose is broken down to make ATP
ATP
hydrolysis
ADP
Adenosine Triphosphate (ATP)Currency of Energy for cells
Adenosine Diphosphate (ATP)ATP is converted to ADP by hydrolyzing one of the phosphorus bonds
Cells break down ATP into ADP for cell activity.
Energy is released by hydrolyzing 3 r d phosphate group of ATP
Cell respiration regenerates ATP supplies by adding a phosphate to ADP
Cells quickly use their ATP supplies for cell activity, so the ATP must be replenished.
ATP provides energy for cell activity
Cell Respiration regenerates ATP
Figure 4.8
Cell Respiration
anaerobic respiration (glycolysis)occurs in the cytoplasmdoes not require oxygen
yields 2 ATP per glucose
aerobic respirationoccurs in mitochondria
requires oxygenyields up to 38 ATP per glucose
Cell Respiration involves 3 reactions
1. GlycolysisGlycolysis is a series of anaerobic reactions that occur in the cytoplasm.
Glucose is broken down into 2 molecules of pyruvic acidOnly 2 molecules of ATP are produced per glucose molecule.
2. Citric Acid Cycle (Kreb’s Cycle)
If oxygen is present respiration continues into the Citric Acid Cycle within the matix of the mitochondrion.
3. Electron Transport ChainAerobic respiration is complete in the electron transport chain.ETC occurs on the inner membrane of the mitochondrion.
glucose 1. glycolysis 2. citric acid cycle 3. ETCUp to
36 ATP
If O2 available
Without O2
Lactic acid
2 ATP
Overview of Cell Respiration
mitochondrion
cellglucose
1. Glycolysis (anaerobic )
pyruvic acid pyruvic acid
O2 available
O2 not available
Lactic acid
2. CAC
3. ETC
Overview of Cell Respiration
Electron Carriers: NADH & FADH2
During respiration electrons are removed from glucose and transported to the ETC by electron carriers.
Energy from the electrons is used to synthesize ATP in the ETC.
NAD+ NADH
glucose
2e- NADH carries 2e- from glucose into the ETC, where its worth 2-3 ATP
FAD FADH2
2e- FADH2 carries 2e- into the ETC, where its worth 2 ATP
2e-
Glycolysis
Glycolysis breaks down glucose into 2 Pyruvic Acid molecules
Occurs in Cytoplasm of Cell
Anaerobic Reaction (no oxygen required)
Glycolysis Yields 2 ATP (net gain) per glucose2 NADH molecule (worth 2-3 ATP in the ETC)2 Pyruvic Acid molecules
Phase 2: lysing of glucose
Phase 3
Summary of Glycolysis glucose
ATPATP
ADPADP
pyruvic acidpyruvic acid
2ATP2 ATP
2ADP2ADP
NAD+NAD+
NADH
Phase 1: phosphorylation of glucose
2 phosphates are added to glucose. 2 ATP are hydrolyzed into 2 ADP molecules in this step.
Glucose is split into 2 3-carbon molecules
Phase 3: oxidation of glucose glucose is oxidized into 2 molecules of pyruvic acid
Phase 3 produces 4 ATP, 2 NADH 2 molecules of pyruvic acid.
Phase 2
Phase 1
NADH
Glycolysis
+ 2 ATP
- 2ATP are used in the first phase
+4 ATP are produced in the third phase
Glycolysis produces a net gain of 2 ATP
The overall products of glycolysis includes:2ATP2 Pyruvic Acids2 NADH (these carry e- to the ETC)
The rest of cell respiration depends on oxygen availability
pyruvic acid
If O2 is available pyruvic acid enters mitochondria for aerobic respiration.
If O2 is not available pyruvic acid completes anaerobic respiration in the cytoplasm.
Anaerobic Respiration
The electron carriers (NADH) from glycolysis cannot enter into the ETC if oxygen is not available.
Without oxygen NADH donates its electrons to pyruvic acid, forming Lactic acid.
pyruvic acid
NADH NAD+
lactic acid
2e-
2e-
This replenishes NAD+ supplies, so they can be used to remove electrons from additional glucose molecules.
Anaerobic Respiration
During exercise when there isn’t sufficient O2 for aerobic respiration, lactic acid (Lactate) accumulates in the cells.
Without O2, Lactic acid builds up as glucose is burned
Anaerobic respiration yields only 2 ATP per glucose, but it provides cells with a quick source of energy; for exercise
Once oxygen is available (eg after exercise), then Lactic Acid is converted back to glucose by the liver
Anaerobic Respiration
Oxygen debt is the amount of O2 required to convert the lactic acid back to glucose after exercise.
End of section 2, chapter 4