A level Bio question help

1. Phospholipid bilayers play crucial roles within plant cells.
Which of the following statements linked to the importance of membranes in plant cells is / are true?
Statement 1: ATP synthase embedded in thylakoid membranes maintains chemiosmotic gradients.
Statement 2: Phospholipid bilayers within the chloroplast are impermeable to protons.
Statement 3: Thylakoid membranes contain electron transport chain proteins.

The answer is statements 2 and 3 but I don’t get why statement 1 is wrong. ATP synthase does allow for the h+ to flow and so maintains the gradients in chemiosmosis right ?On the internet it says it is embedded in the thylakoid membrane. So how’s it wrong?

Can someone explain?

Reply 1

CoZee

Original post by Heyy837372

1. Phospholipid bilayers play crucial roles within plant cells.
Which of the following statements linked to the importance of membranes in plant cells is / are true?
Statement 1: ATP synthase embedded in thylakoid membranes maintains chemiosmotic gradients.
Statement 2: Phospholipid bilayers within the chloroplast are impermeable to protons.
Statement 3: Thylakoid membranes contain electron transport chain proteins.
The answer is statements 2 and 3 but I don’t get why statement 1 is wrong. ATP synthase does allow for the h+ to flow and so maintains the gradients in chemiosmosis right ?On the internet it says it is embedded in the thylakoid membrane. So how’s it wrong?
Can someone explain?

The only explanation I can think of is it's probably the wording that's a bit confusing.
The first statement is false because its actually the other way round. Its the chemisomotic gradients/ proton gradients that drive/maintain ATP synthese function for ATP synthesis
In other words, ATP synthesis is dependent on proton gradients, if protons don't move through the atp synthase channel u don't get atp synthesis.
Whereas proton gradients aren't really dependent on the atp synthesis, rather on the energy released by the flow of e-s through the redox carriers in the ETC to push the protons against their conc gradient

Reply 2

mia66688

Original post by Heyy837372

1. Phospholipid bilayers play crucial roles within plant cells.
Which of the following statements linked to the importance of membranes in plant cells is / are true?
Statement 1: ATP synthase embedded in thylakoid membranes maintains chemiosmotic gradients.
Statement 2: Phospholipid bilayers within the chloroplast are impermeable to protons.
Statement 3: Thylakoid membranes contain electron transport chain proteins.
The answer is statements 2 and 3 but I don’t get why statement 1 is wrong. ATP synthase does allow for the h+ to flow and so maintains the gradients in chemiosmosis right ?On the internet it says it is embedded in the thylakoid membrane. So how’s it wrong?
Can someone explain?

It's because ATP synthase allows H+ to flow down the concentration gradient (from high to low H+ conc). This means since H+ move from high to low concentration eventually the concentration on both sides of the membrane become the same - and there is no longer a concentration gradient. So basically, ATP synthase gets rid of the concentration gradient, instead of maintaining it.

Hope this helps :smile: