Photosynthesis Revision | Baamboozle - Baamboozle

Name the limiting factors of photosynthesis (3)

Light intensity, CO2 concentration, Temperature

Explain the term ‘limiting factor’.

factor limits the rate of a reaction (e.g. photosynthesis), often because it is in short supply, regardless of the levels of other factors

What other molecules (aside from RuBP) can TP be converted into?

Sugars e.g. glucose, starch, cellulose. Amino acids and proteins. Lipids.

What happens during the regeneration step of the light-independent stage?

TP is converted into RuBP, to be used again for fixation of CO2. This process requires ATP.

Describe the reduction step of the light-independent stage.

2 molecules of GP are reduced to 2 of triose phosphate. (ATP/NADPH required) ATP is hydrolysed to provide energy for the conversation, NADPH is reduces GP)

What is the product of fixation of CO2?

two molecules of gylcerate-3-phosophate (GP) a 3-C compound

Name the enzyme that catalyses the fixation of CO2

rubisco (in the stroma)

During fixation, which molecule does CO2 combine with?

Ribulouse bisphosphate (RuBP) a 6-C sugar

Name the three stages of the Calvin cycle

Fixation of carbon dioxide, reduction, regeneration

What are the two important products of the light-dependent stage that are used in the light-independent stage?

ATP and reduced NADP- these compound transfer energy from the light-dependent stage which is used later

State what happens to the products of the photolysis of water.

H+ taken up by NADP, e- replace those lost by the chlorophyll during photoactivation, O2 given off as waste product

What happens to water during the light-dependent stage of photosynthesis?

Water is split using light energy (photolysis). 2H2O → 4H+ + 4e- + O2

How is the H+ gradient used to make ATP?

H+ exit the thylakoid membrane through ATP synthase which catalyses the formation of ATP using the energy in the H+ gradient. NADP accepts H+ and gets reduced

How is the energy from the ETC used in the light-dependent stage?

it is used to pump two H+ ions from the stroma into the thylakoid space. This creates a H+ gradient across the thylakoid membrane

What happens to the electrons that leave the chlorophyll molecule during photoactivation?

Two electrons are taken up by an electron acceptor. They move down electron carriers within the thylakoid membrane in the ETC and release energy as they go

Define photoactivation

process where two electrons in the chlorophyll molecule become excited (due to absorption of light energy) causing them to leave the molecule.

How is the Rf value calculated in chromatography?

distance travelled by the pigment/distance travelled by the solvent

Name the technique used to separate chloroplast pigments.

chromatography

Explain the difference between an absorption spectrum and an action spectrum.

Absorption spectrum measures which wavelengths of light are absorbed by the pigments. An action spectrum measures the rate of photosynthesis at diff wavelengths

Plants containing carotenoid pigments (xanthophyll and carotene) tend to be which colours?

Red, orange and yellow. The carotenoids absorb blue light and reflect red, orange and yellow. These pigments give carrots, tomatoes and egg yolk colour

Which colours of light do chlorophyll pigments absorb, and which do they reflect?

Chlorophyll a and b absorb red light (wavelength 650-700 nm) and blue light (wavelength 400-450 nm). They reflect green light (500-550nm).

Which photosynthetic pigment is found in all photosynthetic plants?

chlorophyll a

Why are there many different photosynthetic pigment

Each pigment absorbs light most efficiently at specific wavelengths. Having multiple pigments allows capture of more energy, compared to having just one pigment

Where in the chloroplast does the light-independent stage of photosynthesis occur?

he stroma

Where in the chloroplast does the light dependent stage occur?

in the thylakoids