Lecture 10- Pathways that harvest chemical energy Flashcards
What is the difference between slow twitch and fast twitch muscle fibers?
Slow twitch: lots of mitochondria to form ATP
Fast twitch: Fewer mitochondria, generate ATP in short bursts in absence of O2
What protein breaks down fat in fat tissues and leads to ‘marathon mouse’? (increase in slow twitch muscle fibers)
PPARδ
What are fuels?
Molecules whose stored energy can be released for use
How are molecules such as fats or proteins able to supply energy?
They are converted into glucose or intermediate compounds
Complex chemical transformations in the cell occur…
in a series of separate reactions that form metabolic pathways
Each reaction in a metabolic pathway is
catalyzed by a specific enzyme
Metabolic pathways are
similar in all organisms, from humans to bacteria
Metabolic pathways are comp_____
Compartmentalized in eukaryotes (certain reactions occur in specific organelles)
Each metabolic pathway is regulated by…
Key enzymes that can be inhibited or activated to determine how fast a reaction can go
C6H12O6 +6O2 —>
6CO2 + 6H20 + free energy
What is the function of the glucose metabolism pathway?
To trap stored energy of glucose into ATP molecules
What is the reaction that traps free energy into ATP molecules?
ADP + Pi + free energy –> ATP
What is the change in free energy from the complete conversion of glucose and oxygen into carbon dioxide and water?
-686 kcal/mol (exergonic)
What are the three metabolic processes that harvest energy from glucose?
Glycolysis
Cellular respiration
Fermentation
What is glycolysis?
The first step in glucose metabolism in all cells and produces two three carbon pyruvates
Does glycolysis use oxygen?
No
What is cellular respiration?
Aerobic
Converts each pyruvate molecule into three CO2 molecules
Energy stored in covalent bonds is transferred into ADP and Pi to form ATP
What is fermentation?
Anaerobic
Converts pyruvate into lactic acid or ethanol (energy rich molecules)
Why does fermentation not release as much energy as cellular respiration?
Lactic acid or ethanol is produced. Glucose break down is incomplete, less energy is released
What four pathways operate when oxygen is present as the final electron acceptor?
Glycolysis,
Pyruvate oxidation
Citric acid cycle
Electron transport chain
What 2 pathways operate in the absence of oxygen?
Glycolysis
Fermentation
What is a redox reaction?
A reaction in which one substance transfers one or more electrons to another substance
What type of reaction is the addition of phosphate to ADP to make ATP?
Endergonic
In redox reactions, what type of agent is glucose and what type of agent is oxygen?
Glucose is a reducing agent
Oxygen is a oxidizing agent
What are co-enzymes?
Small molecules that assist in enzyme-catalyzed reactions
How is ADP a coenzyme?
It picks up energy released in exergonic reactions and uses it to form ATP
Other than ADP, what molecule acts as a coenzyme in redox reactions?
NAD acts as an electron carrier
What does NAD stand for?
Nicotinamide adenine dinucleotide
What is the oxidized and reduced form of NAD?
Oxidized: NAD+
Reduced: NADH + H+
What is the equation for the reduction of NAD+?
NAD+ + 2H –> NADH + H+
What is transferred to NAD+ to form NADH?
A hydride ion, H-
Why does oxygen readily accept electrons from NADH?
It is highly electronegative
What is the equation for the oxidation of NADH?
NADH +H+ +1/202 –> NAD+ +H20
What is the delta G value for oxidation of NADH?
-52.4 kcal/mol
What type of reaction is the oxidation of NADH?
Exergonic
Other than NAD, name another electron carrier in cells.
FAD
What does FAD stand for?
Flavin adenine dinucleotide
Where does glycolysis and fermentation occur in eukaryotes?
external to mitochondria
Where does glycolysis occur in prokaryotes?
In the cytoplasm
Where does fermentation occur in prokaryotes?
In the cytoplasm
Where does the citric acid cycle occur in prokaryotes?
In the cytoplasm
Where does the electron transport chain occur in eukaryotes?
The inner membrane of the mitochondria
Where does the electron transport chain occur in prokaryotes?
Plasma membrane
Where does the citric acid cycle and pyruvate oxidation occur in eukaryotes?
The matrix of the mitochondria