Photosynthesis

Question 1

what happens during photosynthesis?

Answer 1

light energy is converted to chemical energy in the form of glucose

Question 2

what is the equation for photosynthesis?

Answer 2

6CO2 + 6H2O –> C6H12O6 + 6O2

Question 3

when is the chemical energy released?

Answer 3

photosynthesising organisms release it during respiration

Question 4

how do animals obtain their glucose?

Answer 4

eating plants or other animals that have eaten plants, then respire glucose to release energy

Question 5

what are examples of metabolic pathways?

Answer 5

• photosynthesis
• aerobic respiration
• anaerobic respiration

Question 6

what are metabolic pathways?

Answer 6

process that occurs in series of small reactions controlled by enzymes

Question 7

what is anaerobic respiration?

Answer 7

• without oxygen
• plants + yeast cells: produce ethanol and CO2 and release energy
• humans: lactate produced and energy released

Question 8

what is aerobic respiration?

Answer 8

• with oxygen
• produces CO2 and H2O and releases energy

Question 9

can cells make their energy directly from glucose?

Answer 9

• no
• in respiration, energy released from glucose is used to make ATP
• ATP synthesised via condensation reaction, this uses energy from an energy-releasing reaction
  = for example the breakdown of glucose during respiration
• energy is stored as chemical energy in the phosphate bond

Question 10

what is phosphorylation?

Answer 10

adding a phosphate to a molecule

Question 11

what are properties of ATP?

Answer 11

• stores or releases small, manageable amounts of energy so no energy is wasted as heat
• small, soluble molecule so it can easily be transported around the cell
• easily broken down, so energy can easily be released
• quickly remade
• make other molecules more reactive by phosphorylation
• ATP can’t pass out the cell, so cell always has an immediate supply of energy

Question 12

what is the compensation point of light intensity?

Answer 12

• when there’s a particular level of light intensity at which the rate of photosynthesis exactly matches the rate of respiration

Question 13

how can we measure the compensation point?

Answer 13

• measure rate at which oxygen is produced and used by a plant at different light intensities
• compensation point of light intensity is when oxygen is being used as quickly as its being produced

Question 14

where does photosynthesis take place?

Answer 14

chloroplasts

Question 15

what type of membrane do chloroplasts have?

Answer 15

double membrane

Question 16

what do chloroplasts contain?

Answer 16

photosynthetic pigments

Question 17

what are photosynthetic pigments?

Answer 17

coloured substances that absorb light energy needed for photosynthesis

Question 18

where are photosynthetic pigments found?

Answer 18

• found in thylakoid membranes and are attached to proteins

Question 19

what does the protein and the photosynthetic pigment make?

Answer 19

photosystem

Question 20

what are the two types of photosystems?

Answer 20

• Photosystem I (PSI)
• Photosystem II (PSII)

Question 21

what is a photosystem I?

Answer 21

absorbs light best at a wavelength of 700nm

Question 22

what is a photosystem II?

Answer 22

absorbs light best at a wavelength of 680nm

Question 23

what are redox reactions?

Answer 23

involves both oxidation and reduction

Question 24

what are examples of redox reactions?

Answer 24

• photosynthesis
• respiration

Question 25

what is reduction?

Answer 25

- gained electrons - gained hydrogen - lost oxygen

Question 26

what is oxdiation?

Answer 26

- lost electrons - lost hydrogen - gained oxygen

Question 27

oxidation of one moelcule...

Answer 27

reduction of another molecule

Question 28

what is a coenzyme?

Answer 28

a molecule that aids the function of an enzyme

Question 29

how does a coenzyme work?

Answer 29

transferring a chemical group from one molecule to another

Question 30

what is the coenzyme in photosynthesis and what does is do?

Answer 30

NADP - NADP transfers hydrogen from one molecule to another

Question 31

what are the two stages that make up photosynthesis?

Answer 31

- light-dependent reaction - light-independent reaction

Question 32

what is the light dependent reaction?

Answer 32

- requires light

Question 33

where does the light dependent reaction occur?

Answer 33

thylakoid membrane of the chloroplasts

Question 34

explain the process of light dependent reaction.

Answer 34

- light is absorbed by chlorophyll + other photosynthetic pigments in photosystems - light energy excites the electrons in the chlorophyll giving them more energy to eventually be released from the chlorophyll molecules = called photoionisation

Question 35

what is the charge of the chlorophyll?

Answer 35

chlorophyll is now a positively charged ion

Question 36

what is the energy released from released electrons used to do?

Answer 36

- adds a phosphate group to ADP to form ATP - used to reduce NADP to form reduced NADP

Question 37

what does ATP do?

Answer 37

transfers energy

Question 38

what does reduced NADP do?

Answer 38

transfers hydrogen to the light-independent reaction

Question 39

what happens to water during this process?

Answer 39

H2O is oxidised to O2

Question 40

what is a light-independent reaction?

Answer 40

- doesn't require light - relies on the products of light-dependent reaction

Question 41

where do light-independent reactions take place?

Answer 41

stroma of chloroplasts

Question 42

what does ATP and reduced NADP do in light-independent reactions?

Answer 42

- supply energy and hydrogen to make glucose from CO2

Question 43

what are the 3 uses of the energy from photoionisation?

Answer 43

- making ATP from ADP and Pi, this is called photophosphorylation - making reduced NADP from NADP - splitiing water into protons (H+ ions), electrons and oxygen called photolysis

Question 44

what is photophosphorylation?

Answer 44

adding a phosphate to a molecules using light

Question 45

what is photolysis?

Answer 45

splitting a molecule using light energy

Question 46

what reaction includes two types of photophosphorylation?

Answer 46

light-dependent reaction

Question 47

what are the two types of photophosphorylation?

Answer 47

- non-cyclic - cyclic

Question 48

what is non-cyclic photophosphorylation?

Answer 48

- produces ATP, reduced NADP and oxygen

Question 49

what happens during non-cyclic photophosphorylation?

Answer 49

- photosystems in thylakoid membranes are linked by electron carriers

Question 50

what are electron carriers?

Answer 50

proteins that transfer electrons

Question 51

what does a photosystem and electron carriers make?

Answer 51

electron transport chains

Question 52

what are electron transport chains?

Answer 52

chain of proteins through which excited electrons flow

Question 53

what is the process of non-cyclic photophorylation?

Answer 53

- light energy excites electrons in chlorphyll - photolysis of water - energy from excited electrons make ATP - energy from excited electrons generates reduced NADP

Question 54

what happens when the light energy excites electrons in chlorophyll during non-cyclic photphosphorylation?

Answer 54

- light energy is absorbed by PSII, this light energy excites electrons in chlorophyll - electrons move to a h