Flashcards in Aerobic Respiration, Energy and ATP (Chapter 12) Deck (81)
What are the 4 stages of respiration?
The link reaction
The Krebs cycle
Oxidative Phosphorylation (OP)
What is glycolysis?
- The lysis (splitting) of glucose
- It is a multi-step process in which a glucose molecule with 6 C atom is eventually split into 2 molecules of pyruvate, each with 3 C atoms
Where does glycolysis occur?
In the cytoplasm of the cell
What is the net gain of ATP molecules per molecule of glucose broken down during glycolysis?
2 (4 produced, 2 lost)
What is the first stage of glycolysis called?
What happens during phosphorylation?
- Glucose is phosphorylated using 2 molecules of ATP, in order to make it more reactive
1) glucose is first converted to fructose phosphate
2) fructose phosphate is converted to fructose 1,6-biphosphate
What happens during the second stage of glycolysis?
1) fructose 1,6-biphosphate breaks down to produce 2 molecules of triose phosphate (TP)
2) hydrogen is removed from TP + transferred to the carrier molecule (coenzyme) NAD
3) 2 TP is converted to 2 glycerate-2-phosphate (GP)
4) 2 GP is converted to 2 pyruvate and 2 ATP
How many molecules of reduced NAD are produced for each molecule of glucose entering glycolysis?
What is the end-product of glycolysis?
Pyruvate (which still contains lots of chemical potential energy)
What happens during the link reaction?
1) Pyruvate is actively transported from the cytoplasm, through the outer and inner membranes of the mitochondria into the mitochondrial matrix
2) Here, it is decarboxylated and dehydrogenated and combined with coenzyme A (CoA) to produce acetyl CoA
3) The hydrogen removed is transferred to NAD
What are hydrogens carried by reduced energy used for?
They are transferred to other molecules and used in OP to generate ATP
What is the equation for the link reaction?
pyruvate + CoA + NAD <=> acetyl CoA + CO2 + reduced NAD
How many carbons does acetyl CoA have?
When (and only when) does the link reaction happen?
When oxygen is present
When in respiration is CO2 first produced?
During the link reaction
What is the Krebs cycle?
A closed pathway of enzyme-controlled reaction
What happens during one turn of the Krebs cycle?
1) acetyl CoA combines with oxaloacetate (4C) to form citrate (6C)
2) citrate is decarboxylated and dehydrogenated in a series of steps, to yield CO2 (given off as a waste gas) and hydrogens (which are accepted by NAD and FAD)
3) citrate is then reconverted to oxaloacetate
For each turn of the Krebs cycle, how many molecules of CO2 are produced?
For each turn of the Krebs cycle, how many molecules of FAD/NAD are reduced?
For each turn of the Krebs cycle, how many molecules of ATP are generated?
1, via an intermediate compound
Really Fat Americans Can't Run Normally?
1 reduced FAD
3 reduced NAD
What molecule to the reactions of the Krebs cycle make no use of?
What is the most important contribution of the Krebs cycle to the cell's energetics?
The release of hydrogens which can be used in OP to provide energy to make ATP
Where does the link reaction take place?
The matrix of the mitochondrion
Where does the Krebs cycle take place?
The matrix of the mitochondrion
Where does oxidate phosphorylation take place?
In the inner mitochondrial membrane
Where does the energy for the phosphorylation of ADP and ATP come from in OP?
The activity of the electron transport chain
Describe the process of OP (up to the movement of H+)
1) reduced NAD and FAD are passed to the ETC
2) here, the hydrogens are removed from NAD and FAD that they gained in the Krebs cycle and each hydrogen is split into its constituent H+ and e-
3) the energetic e- is transferred to the first in a series of electron carriers, H+ remains in solution
4) as an electron moves from one carrier at a higher energy level to another one at a lower level, energy is released
5) some of this energy is used to move H+ from the matrix to the space between the inner and outer membranes of the mitochondrial envelope
Describe the process of OP (after the movement of H+)
6) this produces a higher [H+] in the intermembrane space than in the matrix, setting up a conc gradient
7) now H+ pass back into the matrix through protein channels in the inner membrane, moving down their conc gradient - associated with each channel is ATP synthase
8) as the H+ pass through the channel, their electrical potential energy is used to synthesise ATP via chemiosmosis
9) in the matrix and e- and a H+ are transferred to O2, reducing it to H2O