module 5 - 17.3 photosynthesis (1)

Question 1

what is photosynthesis?

Answer 1

the process by which the Sun’s energy is used to synthesise organic molecules from 2 small inorganic molecules: carbon dioxide and water

Question 2

what happens to light energy?

Answer 2

it is transferred to chemical energy stored in organic molecules such as glucose

Question 3

what does it mean if an organism is autotrophic?

Answer 3

organisms that photosynthesise

Question 4

what does it mean if an organism is heterotrophic?

Answer 4

organisms obtain organic molecules by eating autotrophs or heterotrophs

Question 5

what do both autotrophs and heterotrophs use in respiration?

Answer 5

both use organic molecules such as glucose, as respiratory substrates to synthesise ATP from ADP and Pi by respiration

Question 6

what are the adaptations, for photosynthesis, for a dicotyledonous leaf?

Answer 6

• large SA in chloroplasts
• flattened sacs called thylakoids (SA)
• short diffusion distance
• stomata
• vascular bundle

Question 7

why are the apical surfaces of the upper and lower mesophyll moist?

Answer 7

for gas exchange

Question 8

why do the lower or spongy mesophyll have air spaces?

Answer 8

to maintain concentration gradient and maintain bulk flow of the leaf

Question 9

why is the cuticle transparent?

Answer 9

to allow light to get through for photosynthesis

Question 10

why is the upper epidermis this and have no chloroplasts?

Answer 10

so light can get all the way through, no photosynthesis

Question 11

how many membranes does a chloroplast have?

Answer 11

2 + thylakoids = 3 membranes

Question 12

what are thylakoid membranes?

Answer 12

flattened sacs

Question 13

what are grana?

Answer 13

stacked thylakoids

Question 14

what are lanellae?

Answer 14

membranous channels

Question 15

what is the stroma?

Answer 15

aqueous solution membrane

Question 16

where are chlorophyll molecules located in a chloroplast?

Answer 16

embedded in thylakoid membrane

Question 17

how is a large surface area of thylakoid membranes achieved in a chloroplast?

Answer 17

folded and flattened

Question 18

what do photosynthetic pigments red, blue and green show?

Answer 18

red - long wavelength of visible light spectrum
green - middle length wavelength of visible light spectrum
blue - short wavelength of visible light spectrum

Question 19

what are photosynthetic pigments?

Answer 19

coloured molecules that absorb and reflect different wavelengths or colours of visible light

Question 20

what do photosynthetic pigments transfer?

Answer 20

light energy into chemical energy with high energy electrons

Question 21

what is chlorophyll A?

Answer 21

the primary photosynthetic pigment and absorbs red and blue light or reflects blue/green

Question 22

what are the 3 secondary photosynthetic pigments?

Answer 22

chlorophyll b - reflects yellow green
xanthophyll - reflects yellow
carotene - reflects orange

Question 23

what is a photosystem?

Answer 23

functional unit in the thylakoid membranes that absorb light energy and transfer the energy to electrons to make high energy electrons

Question 24

what are the 2 components of photosystems?

Answer 24

• antennae complex
• reaction centre

Question 25

what is the antennae complex?

Answer 25

• contains secondary photosynthetic pigments bound to proteins or bound to chlorophyll a/b binding to a protein
• these pigments harvest light energy in the form of high energy electrons and amplify energy until it reaches reaction centre

Question 26

what is the reaction centre?

Answer 26

contains chlorophyll a molecules nound to chlorophyll a/b binding protein, embedded in thylakoid membrane