Sustainability and Interdependence - Plant Growth and Productivity

Question 1

photosynthesis

definition

Answer 1

process by which green plants absorb and convert light energy into chemical energy in carbohydrates

Question 2

three fates of light striking a leaf

Answer 2

• absorption
• reflection
• transmission

Question 3

pigments in the leaf

Answer 3

• chlorophyll a
• chlorophyll b
• xanthophyll
• carotene

Question 4

carotenoids

what are they?

Answer 4

accessory pigements in the leaf which extend the range of wavelengths absorbed by the leaf which include xanthophyll and carotene

chlorophyll b is also an accessory pigement

Question 5

absorption spectrum

Answer 5

graph which shows the wavelengths of light absorbed by each pigment

primarily in blue and red regions

Question 6

action spectrum

Answer 6

graph which shows the rate of photosynthesis at different wavelengths of light

Question 7

chloroplast

where do photosynthetic processes take place?

Answer 7

• photosythetic pigments are contained in the grana
• stage one of photosynthesis occurs in the grana
• stage two occurs in the fluid stroma

Question 8

light dependant stage

photosynthesis process

Answer 8

• photosynthetic pigments absorb light energy, exciting electrons in the pigment molecule (energy level is raised)
• each pigment has a different structure therefore requires a different wavelength of light for excitation
• high energy electrons are captured by primary electron acceptor and trasferred along an ETC
• this releases energy for generating ATP and photolysis
• evolved oxygen (by-product) is released from the leaf and hydrogen combines with NADP and is transferred to the calvin cycle as NADPH

ETC - electron transport chain

Question 9

carbon fixation (calvin cycle)

photosynthesis process

Answer 9

• RuBisCO enzyme fixes CO₂ by attaching it to ribulose biphosphate to form 3-phosphoglycerate molecules (x2)
• 3PG is phosphorylated by ATP and combines with hydrogen (NADPH) to form glyceraldehyde-3-phosphate
• G3P used to regenerate RuBP and for synthesis of glucose

Question 10

fates of glucose

Answer 10

• used as respiritory substrate
• stored as starch
• sythesised into cellulose
• passed onto other biosynthetic pathways to form different metabolites e.g. proteins, fats, nucleic acids

Question 11

photolysis

Answer 11

water is split into hydrogen and oxygen (by energy from high energy electrons passing down an ETC)