Chapter 13- Photosynthesis

Question 1

State the overall equation for photosynthesis

Answer 1

6CO2+6H2O ————–> C6H12O6 +6O2

Question 2

Describe the stroma in chloroplasts and their role in photosynthesis

Answer 2

• The storm is a watery material and acts like the matrix in the mitochondria
• It carries the circles of DNA and small ribosomes
• The storm also contains starch grains which store some of the carbohydrates made in an insoluble form
• it contains enzymes that are used in the light independent stage reactions

Question 3

Describe the lamellae and their function

Answer 3

• This acts as a membrane inside the chloroplast
• These are arranged in such a way to produce fluid-filled sacs.
• These fluid filled sacs are known as thylakoid membranes

Question 4

Describe the thylakoids membrane and their

Answer 4

• These contain spaces inside their sac that are called thylakoid spaces to accumulate H+ ions to create a proton gradient
• They appear green as they reflect it and absorb red and blue wavelengths
• They are stacked up and these stacks are called grana to increase surface area
• They hold the carrier molecules that work as an electron transport chain
• The have several different photosynthetic pigments that are coloured substances that absorb energy from certain wavelengths of light.

Question 5

what is the absorption spectrum

Answer 5

A graph showing the absorbance of different wavelengths of light by a photosynthetic pigment

Question 6

Where are the photosystems found

Answer 6

They are found in the thylakoid membrane and are arranges as clusters

Question 7

Describe photosystem 1 and 2

Answer 7

• they are made up of large numbers of pigment molecules plus some proteins
• These pigments absorb energy from light and channel it to a reaction centre

Question 8

What are the wavelengths of either photosystems

Answer 8

Photosystems 1- 700 nanometers
Photosystem 2 - 680 nanometers

Question 9

Define photophosphorylation

Answer 9

Producing ATP using energy that originated as light

Question 10

Define photolysis

Answer 10

The splitting of a water molecule using energy from light

Question 11

What is the action spectra and what does it show

Answer 11

Its a graph that shows the rate of photosynthesis at different wavelengths of light. It is related to the ability of various pigments in the chloroplasts to absorb energy from different wavelengths of light

Question 12

What is the Rf value

Answer 12

dividing the distance travelled by the substance BY the distance travelled by the solvent

Question 13

The light dependant stage has 2 types of photophosphorylations

Answer 13

• Cyclic
• Non-cyclic

Question 14

What are the products of light dependant stage

Answer 14

• ATP
• reduced NADP

Question 15

Describe Cyclic photophosphorylation

Answer 15

• Takes place ONLY in Photosystem 1
• light energy is absorbed in the system and is passed to the reaction where chlorophyll a is
• This energy excites the pigment to a higher energy level that it us eventually emitted from the chlorophyll (PHOTOACTIVATION)
• The electrons are then captured by an electron acceptor in a thylakoid membrane and passed along a chain of electron carriers
• The carriers are reduced once they GAIN an electron and are oxidised once they PASS the electron onto the next carrier. (REDOX )
• The electrons will eventually lose energy as they pass along the chain and this energy is used to actively move protons from the stroma into the thylakoid space, setting up a gradient.
• They mode down via F.D through ATP synthase and ADP results to ATP (CHEMIOSMOSIS) .

Question 16

Describe Non-cyclic photophosphorylation/ Z-scheme

Answer 16

• 1. Energy from light is absorbed by both photosystems and the excited electrons are emitted off their reaction centres
• 2. the energy emitted from Photosystem 2 is used to form ATP while in Photosystem 1 is passed to the coenzyme NADP to give out reduced NADP
• 3. The electrons now have to be replaced again so Photosystem 1 receives the electron from photosystem 2 while photosystem 2 receives an electron via photolysis
• 4. Once water has been split, oxygen hydrogen ions and electrons are free. Oxygen diffuses out of the chloroplast and is eventually lost.
• 5. The hydrogen ions combine with electrons from Photosystem 1 and the coenzyme NADP to give reduced NADP
• 6. The 1 ATP and 2 reduced NADP that are synthesised are now used in the Light -independent reactions.

Question 17

what are the products of non cyclic and cyclic

Answer 17

Cyclic: Only ATP
Non cyclic: ATP, reduced NADP, O2

Question 18

Describe the Light independent stage

Answer 18

• 1. In this stage, ATP and reduced NAD from the previous stage are used to cover CO2 into carbohydrates.
• 2. CO2 combines with ribulose bisphosphate which is catalysed by the enzyme rubisco
• 3. The reaction then forms the 3C called glycerate 3-phosphate (GP) The CO2 has now become part of the plant
• 4. Now energy from ATP and reduced NADP are used to finally reduce GP to triose phosphate

Question 19

Where does the Light independent stage occur?

Answer 19

The stroma

Question 20

Give examples of some of the molecules triose phosphate condense to

Answer 20

• hexose phosphates which produce;
• starch (storage)
• sucrose for translocation
• Cellulose (cell walls)