BCH210H1 Lecture Notes - Lecture 30: Atp Synthase, Atp Hydrolysis, Integral Membrane Protein

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amethystfly536

25 May 2018

School

UTSG

Department

Biochemical Engineering and Applied Chemistry

Course

BCH210H1

Professor

Stavroula Andreopoulos

For unlimited access to Class Notes, a Class+ subscription is required.

Lecture 30: ATP Synthesis

ATP Synthase

• F0 is the integral membrane protein unit that anchors the enzyme in the inner

mitochondrial membrane

- a subunits creates a channel where protons will enter and bind to c

subunit in the membrane (10-15 of them) which forms a ring and rotates

when protons bind to them

• Protons flow through a subunit causing a rotation in the ring c subunits of F0

• F1 is the peripheral protein (matrix) unit that carries out the catalytic synthesis of ATP

- 3 a and 3 B subunits (Bs are responsible for ATP synthesis)

- Y subunit that runs from membrane component to the middle of the protein (y rotates that induce

conformational change of B)

- Delta at the top and epsilon in the middle that help attachment of lollipop to membrane

• Stator (considered membrane component d) holds the membrane and lollipop together

• Conformational changes in the F1 B subunits are responsible for ATP synthesis

• ATP is then exported out of the matrix to cytosol for use in the rest of the cell by translocase

Boyer’s Binding Change Mechanism

• Each B subunit changes between 3 states (they catalyze ATP separately)

- Open or Empty/exit

- Loose with ADP and Pi bound

- Tight with ATP bound

1. Loose state – ADP + Pi can bind → conformational change through y touching c

2. Tight state – ATP is formed through ADP and Pi combination + H2O → another conformational change

3. Open/empty state → ATP released

• Constant flow of the H+ and rotation of gamma changes the conformation of each subunit

independently

• All three subunits will all be in different states

• A subunits also go through conformational change but do not participate in catalysis (part of complete

enzyme, binding to other two B)

ATP synthase is reversible

• Imaging techniques can be used to visualize rotation of the F1 unit

• ATP hydrolysis can be used to reverse the reaction mechanism

• ATP synthase could be used to drive proton transport via ATP hydrolysis

and drive rotation (proton pumping)

• Add his-tag to anchor F1 to Ni-NTA and label y with GFP → adding ATP + H2O, it binds to tight state,

hydrolysis takes (ADP + Pi) place with conformational change in B that also rotates y

ATP Synthase

• The B-subunit is responsible for ATP synthesis in the matrix of the mitochondria

• As protons flow through the c ring, rotation results in a conformational change in B via the y subunit

• 3 H+ are pumped per ATP molecule synthesized in cytosol (human ATP synthase)

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BCH210H1 Full Course Notes

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4.) Reactions with positive standard free energy changes ( G^oâ>0) can be made to occur in cells by:

a.Coupling them to the hydrolysis of ATP.

b.Coupling them with exergonic reactions via a common intermediate.

c.Manipulating the concentrations of products and reactants such that G <0.

d.All of the above

6.Glycolysis has to âprimeâ the substrate glucose before it can subsequently extract energy from the pathway. What is the compound it uses to do this?

a.NADH. b. NAD⁺. c. GTP. d. ADP. e. ATP

10.Which of the following statements about chloroplasts is FALSE?

a.The thylakoid membrane is permeable to protons.

b.The thylakoid membrane contains the photosynthetic electron transport components.

c.Protons are pumped from the stroma into the thylakoid space.

d.ATP is synthesized in the stroma.

e.Chloroplasts divide to form new chloroplasts.

12.What is the source of free energy (G) for moving protons out of the mitochondrial matrix against their concentration and electrical gradients

a.ATP

b.The redox reactions of the electron transport chain

c.Glycolysis

d.Creatine phosphate

13.The F₀ base of ATP synthase contains a ring of 12 subunits while the F₁ head has 5 different protein subunits in the ratios 3:3:1:1:1. It takes ____ protons for the rotor to make one complete revolution, or _____ protons to make one ATP

a.12, 4

b.12, 2

c.4, 4

d.6, 2

sangriacricket98

1.Bacteriorhodopsin is a protein that has 7 alpha helices embedded in the cell membrane. As such, how many start-transfer and stop-transfer sequences would it need?

7 start transfer sequences, 6 stop transfer sequences

7 of each, in alternating fashion

4 start transfer sequences and 3 stop transfer sequences

7 start transfer sequences

2. The role of GTP hydrolysis by the Signal Recognition Particle during cotranslational translocation to the ER is

to release the SRP after docking to the translocon so translation can resume.

to open the gate/pore of the translocon into the ER.

to arrest translation so that synthesis does not finish before the peptide is delivered to the translocon.

to allow binding to the ribosome.

3. The cisternal maturation model is just one model that describes how objects might move through the Golgi. Some of the statements below describing the cisternal maturation model are correct and some are incorrect. Select all the incorrect descriptions.

There's no need for retrograde movement

Vesicles bud off from the Trans Golgi Network toward the plasma membrane

Vesicular tubules move materials from the cis to medial Golgi networks.

There are no vesicles moving in the anterograde direction

4. Select all statements that are correct concerning electron transport and ATP synthesis during photosynthesis in chloroplasts.

Each photosystem (I and II) pump protons.

Protons are pumped into the lumen of the thylakoid.

The bulb of the synthase projects into the stroma

Photosystem I is reduced directly by Photosystem II

5. Select all that are true about ATP synthesis with an F_oF₁ synthase complex.

Each ADP+Pi is transferred from one beta subunit in Open conformation to a second beta subunit in Loose conformation and finally to the 3rd beta subunit in the T conformation

As the gamma subunit rotates to each beta subunit, it forces them to the open state.

As the gamma subunit rotates to a particular beta subunit, the unit before it changes conformation to Tight and the one ahead of it changes to Loose

As the gamma subunit rotates to a particular beta subunit, the unit before it changes conformation to Loose and the one ahead of it changes to Tight

All 3 beta subunits are always in a different conformation (open, loose, or tight)

6. The number of ATPs per NADH generated by the electron transport system is higher than the number generated per FADH2 because __________.

		electrons from FADH₂ are not oxidized all the way to water
		NADH is converted to NAD⁺, which increases the charge gradient for ATP synthesis
		FADH₂ has a lower (less negative) redox potential than NADH does
		FADH₂ has a higher (more negative) redox potential than NADH does

3.Biological macromolecules are put together by condensation reactions that polymerize activated building blocks.

a.True

b.False

a.12, 4

b.12, 2

c.4, 4

d.6, 2

20.Which of the following statements about chloroplast proteins are true

a.All of the chloroplast proteins are synthesized in the chloroplast

b.Some of the chloroplast proteins are synthesized in the chloroplast, some are imported

c.All of the chloroplast proteins are imported

28.An important function of smooth endoplasmic reticulum and the sarcoplasmic reticulum of muscle cells is to:

a.Synthesize proteins destined for secretion from the cell

b.Modify proteins by the addition of carbohydrates

c.Degrade ubiquitinated proteins

d.Store or sequester Ca++ that can be used for signaling

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BCH210H1 Lecture Notes - Lecture 30: Atp Synthase, Atp Hydrolysis, Integral Membrane Protein

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