IB Light-Dependent Reactions HL

Which of the following describe(s) reduction?

I. removal of oxygen

II. addition of hydrogen

III. addition of electrons

• I only

• II and III only

• II only

• I, II and III

Which of the following is/are produced during the light-dependent reactions of photosynthesis?

I. ATP

II. glucose

III. NADH

• I only

• III only

• I and III only

• I, II and III

Answer explanation

NADPH is produced, not NADH.

In a chloroplast, what name is given to the stacked thylakoid discs?

• grana

• lamellae

• stroma

• chlorophyll

Where do the light-dependent reactions of photosynthesis take place in a chloroplast?

• stroma

• thylakoids

• outer membrane

• inner membrane

Which of the following is/are true of photosystems?

I. they contain pigments

II. they release excited electrons

III. they are found in thylakoid membranes

• I only

• I and III only

• III only

• I, II and III

Which of the following is/are produced during the light-dependent reactions and used in the light-independent reactions?

I. ATP

II. NADPH

III. oxygen

• I only

• I and II only

• III only

• I, II and III

Answer explanation

Oxygen is either used in respiration or leaves through the stomata. It is not needed in the light-independent reactions to produce glucose.

TRUE or FALSE:

All of the oxygen produced during photosynthesis comes from the water.

• TRUE

• FALSE

Answer explanation

Due to photolysis.

During the light-dependent reactions, what provides the energy to create an H⁺ concentration gradient?

• ATP

• osmosis

• diffusion

• energy released from electrons

Answer explanation

ATP is not used to pump the H+ across the membrane at all. Similarly, osmosis only concerns the movement of water molecules.

When H+ ions move across the thylakoid membrane through a carrier protein, in which direction are they travelling?

• inner membrane --> outer membrane

• outer membrane --> inner membrane

• thylakoid space --> stroma

• stroma --> thylakoid space

Answer explanation

The outer and inner membranes are not part of the thylakoids, which is where the light-dependent reactions happen.

When H+ ions move across the thylakoid membrane through ATP synthase, in which direction are they travelling?

• inner membrane --> outer membrane

• outer membrane --> inner membrane

• thylakoid space --> stroma

• stroma --> thylakoid space

Answer explanation

The outer and inner membranes are not part of the thylakoids, which is where the light-dependent reactions happen.