Photosynthesis M5

Question 1

Describe how plants absorb light energy from the sun and use this energy to produce useful substances in the LD stage of p/s.

Answer 1

1. Plants have chloroplast. 2. Inside the chloroplasts are thylakoid membranes, containing photosystems called Photosystem 2 and Photosystem 1. 3. Accessory pigments absorb a wide range of wavelengths (photons) and pass the excitation energy to the reaction centre, made of 2 chlorophyll a molecules. 4. two high energy electrons are released from PS2 reaction centre and pass down the ETC. 5. The electrons loose energy, which activates the proton pump to establish and electrochemical gradient. 6. H+ diffuse back in stroma via ATP synthase, creating ATP from ADP. 7. high energy electrosn from PS1 reaction center get released and used with H+ ions to reduce NADP to NADPH2

Question 2

How many carbons are in one molecule of GP?

Answer 2

unstable 6C compound breaks into 2x 3C

Question 3

How many carbons are in one molecule of TP?

Answer 3

stable 2 molecules of 3C

Question 4

How many times does the Calvin cycle have to occur to produce one molecule of glucose?

Answer 4

6

Question 5

Describe how the products of the LDS of p/s, are used in the Calvin cycle and how carbohydrate is synthesised as a result of the cycle.

Answer 5

1. GP is reduced to form TP. 2. This uses the electrons from NADPH2. 3. ATP hydrolysis in ADP, that supplies the energy for this reaction. 4. Some TP is used to regenerate Ribulose bisphosphate, using ATP. 5. One molecule of glucose is synthesised from 2 TP molecules. 6. Glucose can be used to synthesis other carbohydrates like sucrose, starch or cellulose.

Question 6

Describe the role of water in the light-dependant reaction of p/s.

Answer 6

1. Water is split by photos on light in photosystem 2 in photolysis to give of 2H+ and 2e- and 2.5O2. 2 These two low energy electrons are needed to replace the high energy electrons released by from the reaction centre of PS2

Question 7

Similarities between photosynthesis and respiration

Answer 7

1. conversion of energy from one form to another. 2. They both use and produce ATP. 3. inner mitochondrial membrane is an ETC, and thylakoid membrane is also an ETC. 4. both membrane provide a large surface area for the production of ATP. 5. Both establish an electrochemical gradient.

Question 8

How are thylakoids adapted their functions?

Answer 8

1. Large surface area for more light absorption 2. Carry photosystems 1&2. 3. Contain electron carriers and ATP synthase

Question 9

Define an autotroph

Answer 9

An organism which produces organic molecules from CO2 and other raw material from the environment.

Question 10

Define a heterotroph

Answer 10

An organism that obtains organic food molecules by consuming other organisms or substances derived from them. Includes Animals, fungi and certain prokaryotes

Question 11

Name the products of LDS of p/s

Answer 11

reduced NADP, ATP, oxygen

Question 12

Why is the pH of the thylakoids membrane lower than that of the stroma.

Answer 12

H+ is moving from the lumen to the stroma, so there is more H+ and lower pH. H+ diffuse down the con gradient via ATP synthase. Chemomosis.

Question 13

What is a photosynthetic pigment.

Answer 13

1. Pigment found in chloroplasts. 2. Absorbs light energy that excites electrons 3. Light dependant reaction.

Question 14

What’s they difference between primary and accessory pigments?

Answer 14

absorb different wavelengths. Primary pigment acts as reaction centres whereas assessors just surround the reaction centre.