chapter 17 - photosynthesis

Question 1

what is the difference between an organic compound and a inorganic compound?

Answer 1

• organic compound is a compound which contains carbon(co2,lipids)
• inorganic compound is a compound which does not contain a carbon (phosphate)

Question 2

what is a redox reaction ?

Answer 2

• oxidation is loss of electrons or H
• reduction is gain of electrons or H
• THINK: OILRIG

Question 3

what are coenzymes?

Answer 3

• non protein molecules that help enzymes work by transferring other molecules around
• (NAD - NADH)
• (NADP - NADPH)
• (FAD - FADH)

Question 4

what is phosphorylation?

Answer 4

• its the addition of a phosphate group(e.g. ADP + Pi = ATP)

Question 5

What is photophosphorylation?

Answer 5

• using light energy to add a phosphate

Question 6

what is photolysis?

Answer 6

• using light energy to split a molecule (e.g.H20 + light ->2H +2e + 1/2 O2 )

Question 7

what is an electron transport chain?

Answer 7

• when electrons flow through electron carriers(proteins) in a membrane

Question 8

what is a proton?

Answer 8

a hydrogen ion

Question 9

what is the purpose of the light dependant reaction and where does it take place?

Answer 9

• it uses light energy to make ATP and reduced NADP
• takes place on the thylakoid membrane(large SA)

Question 10

what is the purpose of the light independent reaction and where does it take place?

Answer 10

• it uses the products of the light dependant stage to make useful organic compounds
• takes place in the stroma

Question 11

what is the role of the chloroplast?

Answer 11

• absorbs light energy which is used for photosynthesis to make useful organic compounds

Question 12

what is purpose of the thylakoid?

Answer 12

• has a large surface area, increasing the rate of photosynthesis
• contains photosynthetic pigments which absorb light energy (e.g. chlorophyll a, chlorophyll b and keratin )

Question 13

what does the chloroplast structure consist of?

Answer 13

• thylakoid
• grana
• lamealle
• stroma
• chloroplast DNA
• starch grain

Question 14

what are the two parts photosystems are made up of and what are the roles of these systems?

Answer 14

• light harvesting system, contains accessory pigments (e.g. chlorophyll b) so plants can absorb a greater range in light wavelength
• reaction centre, contains primary pigments (e.g. chlorophyll a)

Question 15

what is happening in the light harvesting system?

Answer 15

• light energy is absorbed by the accessory pigments

Question 16

What is happening in the reaction centre?

Answer 16

• more light energy is being absorbed by the primary pigments
• this energy is being used to excite electrons

Question 17

What happens in the light dependant reaction(photophosphorylation )?

Answer 17

• photosynthetic pigments absorb light energy
• This excites the electrons which leave the chlorophyll
• electron moves along the electron transport chain
• electron releases energy
• this energy is used to join ADP + Pi = ATP
• NADP is reduced to form NADPH
• The NADP gain the hydrogen from the photolysis of water which makes H, E and O

Question 18

What happens in cyclic photophosphorylation?

Answer 18

• photosynthetic pigments absorb light energy in PS1
• This excites the electrons to a higher energy Level
• electrons flow through the electron transport chain losing its energy
• energy is used to create a proton gradient
• H ions flow back to the stroma through ATP synthase
• This provides the energy for ADP + pi = ATP

Question 19

what are some differences and similarities between cyclic and non - cyclic photophosphorylation?

Answer 19

• cyclic uses only PS1 whereas non-cyclic uses PS1 and PS2
• cyclic produces only ATP whereas non-cyclic produces ATP and NADPH
• oxygen is released from the photolysis of water in non-cyclic whereas in cyclic oxygen is not
• in cyclic the electrons are recycled whereas in non-cyclic the electrons are replaced by the photolysis of water
• both cyclic and non - cyclic use the electron transport chain

Question 20

what is the chemiosmotic theory?

Answer 20

• electrons lose energy along the electron transport chain
• this energy is used to pump protons(H) across the membrane
• This creates a proton gradient
• Protons diffuse through ATP synthase = chemiosmosis
• this provides energy for ADP + Pi = ATP

Question 21

what is the purpose of the Calvin cycle?

Answer 21

• it uses the products of the LDR (ATP and NADPH) to convert Co2 into useful organic compounds (E.g. lips, amino acids and glucose)

Question 22

what is the process of the Calvin cycle?

Answer 22

• Co2 combines with Rubp catalysed by the enzymes rubisco
• which makes two molecules of GP
• Both are reduced to form two molecules of TP using NADPH and ATP
• Most TP is regenerated to form Rubp using energy from ATP
• Some of the TP is converted into useful organic compounds (E.G. lipids, amino acids and glucose)

Question 23

what are the three limiting factors of photosynthesis?

Answer 23

• light intensity
• CO2 concentration
• Temperature

Question 24

How does light intensity, CO2 conc and temperature affect the rate of photosynthesis?

Answer 24

• light intensity, the higher it is the more energy there is for LDR so the faster the rate of photosynthesis
• the higher the CO2 conc the greater the rate of photosynthesis is. However, past its optimum(0.4%) it has a negative effect on the rate
• photosynthesis is controlled by enzymes so if you increase the temperature, you will increase the rate of reaction to the optimum temperature. However, beyond the optimum temp the rate decreases
• the plant can also close its stomata due to higher temps meaning lower CO2 levels therefore Calvin cycle falls lowering the rate of photosynthesis

Question 25

understanding how the limiting factors affect the rate of photosynthesis, what should a farmer do in order to boost the rate of photosynthesis?

Answer 25

- using light at night - greenhouse allows light to pass in - burn fossil fuels in a greenhouse which will increase the CO2 conc - greenhouse will trap warmer air - heating/cooling system to maintain optimum temperature

Question 26

What is the importance of photosynthetic pigments in photosynthesis?

Answer 26

- pigments absorb light - electrons are raised to a higher energy level - accessory pigments pass energy to primary pigments - primary pigments pass electrons to the electron transport chain

Question 27

why do Chromista need pigments that are different from those of other photosynthetic organisms?

Answer 27

- they have to absorb light of shorter wavelengths - chromista have fewer thylakoid membranes - chromista has no lamellae - chromista has no stratch grains

Question 28

where are the photosynthetic pigments located in the chloroplast?

Answer 28

- photosystems in the thylakoid membrane