CELLULAR RESPIRATION Flashcards
What s cellular respiration?
A group of catabolic reactions that are jointly called “cellular respiration”
CONSISTS OF:
- glycolysis
- Citric Acid Cycle
- Electron Transport Chain
Why is glucose important in these reactions?
- Is the primary source of fuel
how does glucose enter the cell?
- using a glucose transport protein - insulin aids in sneaking glucose thru the membrane
- The cells then begin glucose catabolism and use the energy to create ATP
What are anaerobic and aerobic reactions?
- anaerobic: doesn’t require oxygen
- Aerobic: does require oxygen
( most ATP is produced by aerobic reactions)
Where does glycolysis take place?
- In the cytosol and doesn’t require oxygen
How much ATP does glycolysis produce?
- TWO ATP
How much ATP does the citric acid cycle produce?
- TWO ATP
How much ATP does the electron transport chain produce?
- generates about 28 ATP.
How much ATP is produced per glucose molecule?
- typically 32
What are the general characteristics of glycolysis?
- Both aerobic and anaerobic pathways begin with glycolysis
- Consists of ten enzyme-catalyzed reactions that break down a 6-carbon glucose molecule into two 3-carbon pyruvic acid molecules
What are the 3 steps in glycolysis?
- Priming by phosphorylation
- Cleavage
- Formation of NADH + ATP
What is the first step of glycolysis in detail?
- Two phosphate groups are added to a glucose molecule, one at each end, in a step called PHOSPHORYLATION.”
- This step requires energy from TWO ATPS, which are used to PRIME the glucose to ready it for the upcoming reactions
What is the second step of glycolysis in detail?
- The 6-carbon glucose molecule is cleaved into two 3-carbon molecules
What is the third step of glycolysis in detail?
- The hydrogen carrier NADH is formed, ATP is synthesized, and two 3-carbon pyruvic acid molecules result
What happens to the “high energy” electrons released during glycolysis?
- Electrons that are released during glycolysis are hydrogen atoms + contain much of the energy from the chemical bonds in the original glucose molecule
What is NAD+ and how is it related to the hydrogen atoms?
- To use hydrogen atoms as cellular energy, they are passed in pairs to bind with NAD+ molecules
2 protons + 2 electrons bind to the molecules of the hydrogen carrier NAD+
How does NAD+ change after the hydrogen bonds bind to it?
NAD+ + 2H –> NADH + H+
What does NADH do with the hydrogen atoms?
- NADH delivers hydrogen atoms with high energy electrons to the electron transport chain in the mitochondria to be synthesized as ATP
- NADH is an electron carrier
How many ATP are synthesized during glycolysis?
- 4 ATP are synthesized directly, subtracting the 2 ATP molecules in the priming process
- This yields a net gain of 2 ATP per molecule of glucose
What are the products of glycolysis?
- when one glucose molecule is broken down there are 2 ATP and 2 pyruvic acid molecules
What is oxygen’s role at the end of the electron transport chain?
- For cellular respiration to continue, NADH + H+ must be able to deliver hydrogen atoms to the electron transport chain to replenish the supply of NAD+
- This can only happen in the presence of oxygen
- It is the final electron accept at the end of the ETC
that enables the chain to continue processing hydrogen atoms and recycling NAD+
What happens without oxygen in the Electron Transport Chain?
- The NADH+ has nowhere to unload its hydrogen atoms
- As an alternative NADH + H+ can give its hydrogen atoms back to the pyruvic acid in a reaction that forms lactic acid
- this inhibits glycolysis and ATP production declines
What is the citric acid cycle?
- Takes place in the fluid of the mitochondrial matrix
- The citric acid cycle begins when a 2-carbon acetyl CoA molecule combines with a 4-carbon oxaloacetic acid molecule to form a 6-carbon citric acid and CoA
- The citric aid is changed thru a series of reactions back into oxaloacetic acid
- The cycle repeats as long as the mitochondrion receives oxygen and pyruvic acid
What are the 3 important consequences of the citric acid cycle?
- One ATP is produced directly for each citric acid molecule that goes thru the cycle
- For each citric acid molecule, 8 hydrogen atoms with high-energy electrons are transferred to the hydrogen carriers NAD+, and the related molecule FAD
NAD+ + 2H —> NADH + H+
FAD + 2H –> FADH2
- As the 6-carbon citric acid reacts to form the 4-carbon oxaloacetic acid, two carbon dioxide molecules are produced.
