Photosynthesis

Question 1

What is the primary purpose of photosynthesis?

Answer 1

To convert light energy into chemical energy stored in glucose.

Question 2

Which organisms primarily perform photosynthesis?

Answer 2

Plants, algae, and some bacteria.

Question 3

What are the two main stages of photosynthesis?

Answer 3

Light-dependent reactions and the Calvin cycle (light-independent reactions).

Question 4

Where in the plant cell does photosynthesis occur?

Answer 4

In the chloroplasts.

Question 5

What pigment is primarily responsible for capturing light energy?

Answer 5

Chlorophyll.

Question 6

True or False: Photosynthesis occurs only in the presence of sunlight.

Answer 6

True.

Question 7

What are the inputs of the photosynthesis equation?

Answer 7

Carbon dioxide (CO2), water (H2O), and light energy.

Question 8

What is the main output of photosynthesis?

Answer 8

Glucose (C6H12O6) and oxygen (O2).

Question 9

Fill in the blank: The light-dependent reactions take place in the _______.

Answer 9

Thylakoid membranes.

Question 10

What is the role of NADP+ in photosynthesis?

Answer 10

It acts as an electron carrier, becoming NADPH.

Question 11

Multiple Choice: Which of the following is NOT a product of the light-dependent reactions? A) ATP B) NADPH C) Glucose D) Oxygen

Answer 11

C) Glucose.

Question 12

What is the function of ATP in the Calvin cycle?

Answer 12

It provides energy for the conversion of carbon dioxide into glucose.

Question 13

True or False: The Calvin cycle requires light directly.

Answer 13

False; it does not require light directly but relies on products from light-dependent reactions.

Question 14

What enzyme is crucial for fixing carbon dioxide in the Calvin cycle?

Answer 14

Ribulose bisphosphate carboxylase/oxygenase (RuBisCO).

Question 15

What is the significance of the photolysis of water in photosynthesis?

Answer 15

It produces oxygen and provides electrons for the light-dependent reactions.

Question 16

Fill in the blank: The overall equation for photosynthesis can be summarized as 6CO2 + 6H2O + light energy → _______.

Answer 16

C6H12O6 + 6O2.

Question 17

What is the role of water in photosynthesis?

Answer 17

Water provides electrons and protons and is a source of oxygen.

Question 18

What happens during the carbon fixation phase of the Calvin cycle?

Answer 18

Carbon dioxide is incorporated into organic molecules.

Question 19

Multiple Choice: Which of the following is an end product of the Calvin cycle? A) ATP B) Glucose C) NADPH D) Oxygen

Answer 19

B) Glucose.

Question 20

True or False: Chloroplasts contain their own DNA.

Answer 20

True.

Question 21

What is the role of the electron transport chain in photosynthesis?

Answer 21

It transfers electrons and pumps protons to create a proton gradient used for ATP synthesis.

Question 22

What is the significance of the proton gradient created during the light-dependent reactions?

Answer 22

It drives ATP synthesis via ATP synthase.

Question 23

Fill in the blank: The Calvin cycle occurs in the _______ of the chloroplast.

Answer 23

Stroma.

Question 24

What is the main function of light-harvesting complexes in photosynthesis?

Answer 24

To capture and transfer light energy to the reaction center.

Question 25

What effect does increased carbon dioxide concentration have on the rate of photosynthesis?

Answer 25

It generally increases the rate of photosynthesis, up to a certain point.

Question 26

Multiple Choice: Which factor does NOT affect the rate of photosynthesis? A) Light intensity B) Temperature C) Soil pH D) Carbon dioxide concentration

Answer 26

C) Soil pH.

Question 27

What happens in the light dependent reaction.

Answer 27

Light energy is used to breakdown water (photolysis) to produce hydrogen ions, electrons and oxygen in the thylakoid lumen
A proton gradient is formed due to the photolysis of water resulting in a high concentration of hydrogen ions in the thylakoid lumen
Electrons travel through an electron transport chain of proteins within the membrane
Reduced NADP (NADPH) is produced when hydrogen ions in the stroma and electrons from the electron transport chain combine with the carrier molecule NADP
ATP is produced during a process known as photophosphorylation

Question 28

What is photophosyphorylation

Answer 28

Photophosphorylation is the name for the overall process of using light energy and the electron transport chain to phosphorylate ADP to ATP
The light-dependent reaction is sometimes called ‘photophosphorylation

Question 29

Explain how photophosphorylationw irks

Answer 29

During photophosphorylation, energetic (excited) electrons are passed along a chain of electron carriers (known as the electron transport chain)
The electron carriers are alternately reduced (as they gain an electron) and then oxidised (as they lose the electron by passing it to the next carrier)
The excited electrons gradually release their energy as they pass through the electron transport chain
The released energy is used to pump protons (H+ ions) across the thylakoid membrane, from the stroma (the fluid within chloroplasts) to the thylakoid lumen (the space within thylakoids)
A ‘proton pump’ transports the protons across the thylakoid membrane, from the stroma to the thylakoid lumen
The energy for this transport comes from the excited electrons moving through the electron transport chain
This creates a proton gradient, with a high concentration of protons in the thylakoid lumen and a low concentration in the stroma
Protons then return to the stroma (moving down the proton concentration gradient) by facilitated diffusion through transmembrane ATP synthase enzymes in a process known as chemiosmosis
This process provides the energy needed to synthesise ATP by adding an inorganic phosphate group (Pi) to ADP (ADP + Pi → ATP)
The whole process is known as photophosphorylation as light provides the initial energy source for ATP synthesis
The photophosphorylation of ADP to ATP can be cyclic or non-cyclic, depending on the pattern of electron flow in photosystem I or photosystem II or both
In cyclic photophosphorylation, only photosystem I is involved
In non-cyclic photophosphorylation, both photosystem I and photosystem II are involved

Question 30

Photo systems

Answer 30

Photosystems are collections of photosynthetic pigments that absorb light energy and transfer the energy onto electrons, each photosystem contains a primary pigment
Photosystem II has a primary pigment that absorbs light at a wavelength of 680nm and is therefore called P680
Photosystem II is at the beginning of the electron transport chain and is where the photolysis of water takes place
Photosystem I has a primary pigment that absorbs light at a wavelength of 700nm and is therefore called P700
Photosystem I is in the middle of the electron transport chain
The energy carried by the ATP is then used during the light-independent reactions of photosynthesis

Question 31

Cyclic photophosphrylatin

Answer 31

Cyclic photophosphorylation involves photosystem 1 (PSI) only
Light is absorbed by photosystem 1 (located in the thylakoid membrane) and passed to the photosystem I primary pigment (P700)
An electron in the primary pigment molecule (ie. the chlorophyll molecule) is excited to a higher energy level and is emitted from the chlorophyll molecule in a process known as photoactivation
This excited electron is captured by an electron acceptor, transported via a chain of electron carriers known as an electron transport chain before being passed back to the chlorophyll molecule in photosystem 1 (hence: cyclic)
As electrons pass through the electron transport chain they provide energy to transport protons (H+) from the stroma to the thylakoid lumen via a proton pump
A build-up of protons in the thylakoid lumen can then be used to drive the synthesis of ATP from ADP and an inorganic phosphate group (Pi) by the process of chemiosmosis

Question 32

Non-cyclic photophosphorylatiob

Answer 32

Light is absorbed by photosystem 2 (located in the thylakoid membrane) and passed to the photosystem 2 primary pigment (P680)
Two electrons in the primary pigment molecule (ie. the chlorophyll molecule) are excited to a higher energy level and are emitted from the chlorophyll molecule in a process known as photoionisation
Each excited electron is passed down a chain of electron carriers known as an electron transport chain, before being passed on to photosystem 1
During this process chemiosmosis occurs:
The energy given by the electrons moving through the electron transport chain enables H­­+ ions (protons) to pass from a low concentration in the stroma to a high concentration in the thylakoid lumen
The creation of this proton gradient across the membrane later drives the synthesis of ATP in photophosphorylation