Photosynthesis (BIOL4)

Question 0

Define phosphorylation

Answer 0

Adding phosphate to a molecule

Question 1

Define metabolic pathway

Answer 1

Series of small reactions controlled by enzymes e.g respiration and photosynthesis

Question 2

Define photophosphorylation

Answer 2

Adding phosphate using light

Question 3

Define photolysis

Answer 3

Splitting using light

Question 4

Define hydrolysis

Answer 4

Splitting using water

Question 5

Define decarboxylation

Answer 5

Removal of carbon dioxide

Question 6

Define dehydrogenation

Answer 6

Removal of hydrogen

Question 7

What happens during a **REDUCTION **reaction?

Answer 7

Gained electrons

Gained hydrogen

Loss of oxygen

Question 8

What happens during an OXIDATION reaction?

Answer 8

Loss of electrons

Loss of hydrogen

Gain of oxygen

Question 9

Define coenzyme

Answer 9

Molecule that aids the function of an enzyme

Question 10

Where does photosynthesis take place within a plant?

Answer 10

In the organelle chloroplasts

Question 11

What features do a chloroplast have?

Answer 11

• Inner membrane
• Outer membrane
• Thylakoids that are stacked into granum
• Photosynthetic pigments found in the thylakoid membranes: chlorophyll A, B and carotene (absorb light energy)
• Stroma
• Starch grain

Question 12

What are the stages of the light-dependent reaction?

Answer 12

1. Light energy absorbed by PSII, exciting electrons to move to higher energy level, moving along electron carriers to PSI
2. Loss of electrons in PSII causes photolysis of water into protons (H+ ions), electrons and oxygen
3. Excited electrons lose energy as moving along electron carriers, this energy transports protons into thylakoid, so thylakoid has a h. conc. than stroma
   
   • Protons move down concentration gradient into stoma via ATP synthase
   • Energy from this movement combines ADP + Pi –> ATP
4. Electrons transferred to NADP + H+ to form NADPH

Question 13

What is the difference between non-cyclic phosphorylation and cyclic phosophylation?

Answer 13

Non-cyclic phosphorylation produces ATP, NADPH and oxygen

Cyclic phosphorylation produces electrons and are recycled to only produce ATP

Question 14

What happens during the light-independent reaction/Calvin cycle?

Answer 14

1. CO2 diffuse into stroma of chloroplasts, combines w/ RuBP (5C) by rubisco, forming 2x 3C GP
2. ATP from LDR gives energy to reduce 2x GP –> 2x TP
   
   • ​​NADPH oxidised to NADP
3. TP molecules converted to organic compounds (e.g glucose)
4. TP regenerate RuBP using ATP from LDR to restart cycle.

Question 15

What are the limiting factors of photosynthesis?

Answer 15

Light intensity, temperature and concentration of CO2.

Question 16

What are the effects of light as a limiting factor?

Answer 16

• Needed for photosynthesis
• Light energy absorbed by chlorophyll to excite elections to move along electron carriers
• Influences primary productivity, thus affecting all food chains (more light available for photosynthesis, thus more products made)
• Day length affects plant growth and animal behaviour

Question 17

What are the effects of temperature as a limiting factor?

Answer 17

• Affect enzymes used in metabolic reactions
• Will increase/decrease kinetic energy, more/less collisaions and more/less producted formed

Question 18

What are the effects of salinity?

Answer 18

• Affects osmosis, affecting water availability
• **Osmosis **- movement of water molecules through semi-permeable membrane from area of high water potential to low water potential

Question 19

What are the effects of pH level?

Answer 19

• Affects enzyme activity, thus affects metabolism
• Certain pH ranges needed by enzymes to work (optimum pH), if below/above range, enzymes will denature