Unit 2 (Cellular Respiration) Flashcards
Overall Equation for Cellular Respiration
C6H12O6(aq) + 6O2(g) → 6CO2(g) + 6H2O(l) + 36ATP
During cellular respiration, …. energy liberated by …. reactions is used to build ATP
free, endergonic
ATP Equation
ADP + Pi (inorganic phosphate) → ATP + H2O
Cellular Respiration: Endergonic or Exergonic
Exergonic
ATP Synthesis: Endergonic or Exergonic
Endergonic
Substrate Level Phosphorylation (3 defining attributes)
Forms ATP directly in an enzyme catalyzed reaction
A phosphate group is attached to ATP (in a coupled reaction)
Does not require oxygen (anaerobic)
Oxidative Phosphorylation (3 defining attributes)
Forms ATP indirectly in a series of enzyme catalyzed reactions
Oxygen is the final electron acceptor
Requires oxygen (aerobic)
What is the reaction coupling used in the synthesis of ATP?
The free energy released from the exergonic oxidation of glucose is used in the endergonic reactions used to synthesize ATP.
What is the role of electron carriers?
During cellular respiration, redox reactions transfer the bond energy between carbon and hydrogen molecules in glucose in the form of electrons to molecules called electron carriers. By using electron carriers, energy harvested from glucose can be temporarily stored until the cell can convert the energy into ATP.
Where does glycolysis occur?
Cytoplasm
What is the purpose of Glycolysis
Glycolysis is used to partially oxidize the glucose (6-C) into two 3 carbon molecules called pyruvate.
What is required to activate glycolysis?
2 ATP (needed to phosphorylate the glucose to produce G6P which becomes G3P)
Is Glycolysis aerobic or anaerobic?
Anaerobic.
What is the net yield of glycolysis?
2ATP (4 are produced, but two are used up to create G6P), and 2NADH
Equation of Glycolysis
Glucose + 2ADP + 2Pi +2NAD+ → 2 pyruvate + 2ATP + 2NADH + 2H+
Where do pyruvate molecules go after glycolysis?
Pyruvate go to the mitochondria for further reaction.
Where do NADH molecules go after glycolysis?
NADH molecules go to the mitochondria to participate in the electron transport chain.
What are the areas of the Mitochondria? (5)
Outer membrane (smooth), inner membrane (highly folded), Cristae (folds), Inter Membrane Space, Matrix (inner compartment of protein rich fluid)
Where in the mitochondria are the proteins and coenzymes involved in electron transport?
In the cristae.
Where does pyruvate oxidation occur?
Pyruvate molecules translocated from cytoplasm to mitochondrial matrix by carrier proteins.
What does pyruvate oxidation do? (3)
Removes CO2 from the pyruvate changing it from a 3-C to a 2-C molecule decarboxylation (CO2 is waste)
Oxidizes the 2-C molecule while reducing NAD+ to NADH
2-C (Acetyl) group attaches to Coenzyme A
What does pyruvate oxidation produce?
Two CO2, Two NADH (one for each of the two pyruvate molecules), Acetyl-CoA
Where does Acetyl CoA go if ATP levels are high?
The acetyl CoA will convert the acetyl group to fats for storage
Where does Acetyl CoA if ATP levels are low?
It will move on to the Krebs cycle.
What does Kreb’s cycle do?
Kreb’s cycle removes as many electrons from the remaining acetyl groups as possible.
How many times does Kreb’s cycle occur?
The cycle occurs twice (once for each of the 2 acetyl-CoA molecules).
What does the cycle begin and end with?
A 4-C molecule called oxaloacetate.
Kreb’s Cycle Equation
2 Oxaloacetate + 2acetyl-CoA +2ADP + 2Pi + 6NAD+ + 2FAD → 2 Oxaloacetate + 2CoA + 2ATP + 6NADH + 6H+ +2FADH2 + 4CO2
Where does Kreb’s cycle occur?
Kreb’s cycle occurs in the matrix.
What does Kreb’s cycle produce?
This cycle produces lots of stored energy in the form of high energy electrons in NADH and FADH2.
Why is recylcling NAD+ and FAD important?
Cells have limited supplies of coenzymes NAD+ and FAD so recycling them is very important.
How do NADH and FADH2 help with recycling coenzymes?
These reduced coenzymes will carry their high energy electrons to the ETC where they will be oxidized and returned to the system as NAD+ and FAD.
What happens to glucose at the end of Kreb’s cycle?
It is completely broken down.
What does the Electron Transport Chain do?
ETC removes the electrons from the coenzymes NADH and FADH2.
How does ETC function?
High energy electrons funneled through a series of redox reactions, liberating free energy that is used to phosphorylate ADP.
Where do the oxidized coenzymes go after ETC?
Oxidized coenzymes (NAD+ and FAD) return to pick up more electrons from other glucose molecules.
Where does ETC occur?
ETC occurs in the inner membrane of the mitochondria.
In what order of the proteins arranged in the Electron Transport Train?
The proteins are arranged in order of increasing electronegativity.
What goes first in ETC?
NADH (weakest)
What goes last in ETC?
Cytochrome oxidase
What is the final electron acceptor?
Oxygen gas
What happens to oxygen after it receives two electrons?
When oxygen receives the 2 electrons, it attracts 2 H+ ions, and together, they all form water (a known product of cellular respiration).
How many electrons do NADH and FADH2 release to ETC?
They both release two electrons.
Every time the electrons are transferred from one carrier to another (redox) a small amount of ………. is released.
free energy
Does the Electron Transport Chain make ATP directly?
No.
What is the Free energy released by redox reactions used for?
Free energy released by redox reactions is used pump H+ ions from matrix to inter-membrane space
What does the movement of the H+ ions from the matrix to the inter-membrane produce?
This generates a proton gradient across the inner mitochondrial membrane
What does the proton gradient produce?
Potential energy (proton motive force) stored in the proton gradient created across biological membranes that are involved in chemiosmosis (used to phospohrylate ADP).
What is coupled in chemiosmosis?
Hydrogen flow (Ek) is coupled to ATP synthesis.
How does chemiosmosis work?
The H+ ions that are built up in the intermembrane space (IMS) want to diffuse back into the matrix (down the gradient) but the membrane is impermeable. Transport proteins are the only path. ATP synthase enzyme is associated with each protein channel and harnesses the ‘flow’ energy.This energy is used to phosphorylate ADP to ATP (Oxidative Phosphorylation).
Since NADH and FADH2 don’t produce the same amount of free energy…
They can’t produce the same amount of ATP.
How many ATP in a glucose molecule?
36 ATP in a glucose molecule.
What is the yield of ATP and where does the remaining energy go?
The yield is closer to 32 ATP/glucose, the remaining energy is lost as heat.
2 e- from NADH (glycolysis) provide enough free energy to produce…
2 ATP
2 e- from NADH (Krebs cycle/Pyruvate oxidation) provide enough free energy to produce…
3 ATP
2 e- from FADH2 (Krebs cycle) provide enough free energy to produce…
2 ATP
How much NADH is produced in glycolysis?
2 NADH
How much NADH is produced in Krebs cycle/Pyruvate oxidation?
8 NADH
How much FADH2 is produced in Krebs cycle?
2 FADH2
How much ATP does NADH from (glycolysis) produce?
4 ATP
How much ATP does NADH from (Krebs cycle/Pyruvate oxidation) produce?
24 ATP
How much ATP does FADH2 from (Kreb’s cycle) produce?
4 ATP
How much ATP is produced in Substrate Level Phosphorylation (total)?
4 ATP
How much ATP is produced in Substrate Level Phosphorylation (glycolysis)?
2 ATP
How much ATP is produced in Substrate Level Phosphorylation (Krebs cycle/Pyruvate oxidation)?
2 ATP
How much ATP is produced in Substrate Level Phosphorylation (Electron Transport Chain)?
0 ATP
How much ATP is produced in Oxidative Phosphorylation (total)?
32 ATP
How much ATP is produced in Oxidative Phosphorylation (glycolysis)?
0 ATP
How much ATP is produced in Oxidative Phosphorylation (Krebs cycle/Pyruvate oxidation)?
0 ATP
How much ATP is produced in Oxidative Phosphorylation (Electron Transport Chain)?
32 ATP
What process happens when there is no oxygen present?
Fermentation.
What are the molecular implications of a lack of oxygen?
The ETC can no longer rid itself of electrons (not ‘syphoned off’)
It backs up
no longer recycles FAD/NAD+ needed for Krebs cycle
No -ΔG
How does fermentation work?
Glycolysis is the only means of making ATP in cells
Step 4 of glycolysis forms NADH from NAD+
Unless there is a source of NAD+ (H+ atoms added to NADH, glycolysis will stop (glycolysis requires NAD+)
NADH is used to reduce pyruvate (2-oxopropanoate) to lactate (2-hydroxypropanoate) in animal cells or to ethanol and CO2 in yeast cells.
This regenerates NAD+ so that glycolysis can continue.
How much ATP are yielded by ethanol fermentation?
2 ATP
Can ethanol fermentation be used by multicellular organisms?
No.
Why is alcohol limited to about 10%?
Ethanol produced by fermentation kills the yeast if it remains in their environment.
Describe fat degradation.
Fats - hydrolyzed to glycerol and 3 fatty acids
Glycerol - easily converted to G3P (C3 - P) for entry into glycolysis
Fatty Acids - snipped into C2 groups (acetyl) for entry into Kreb’s cycle
Describe protein degradation.
Proteins - hydrolyzed to amino acids
Amino acids
NH2 is removed (deamination), converted to ammonia (NH3) and excreted
the # of C remaining now determines where the molecule enters Kreb’s cycle
All of the reactions involved in cellular respiration are part of a …..
Metabolic pool
Molecules from the metabolic pool can be used either as…..
energy sources or as substrates for various synthetic reactions.
The essence of synthetic pathways is that…..
one type of molecule can be converted to another.
Why is acetyl CoA essential to synthetic pathways?
Acetyl CoA has a central role in these conversions since it links Kreb’s cycle, glycolysis, protein metabolism and fatty acid metabolism.
What amino acids cannot be synthesized?
Essential amino acids cannot be synthesized.
What is VO2 max?
VO2 max, is the maximum volume of oxygen that the cells of the body can remove from the bloodstream in one minute per kilogram of body mass while the body experiences maximal exertion.
What is the lactate threshold?
The lactate threshold is the value of exercise intensity at which blood lactate concentration begins to increase sharply.
