C1.3 Photosynthesis SL

Question 1

give the chemical equation for photosynthesis

Answer 1

6CO2 + 6H2O -> C6H12O6 + 6O2

Question 2

give the word equation for photosynthesis

Answer 2

carbon dioxide + water -> glucose + oxygen

Question 3

what does photosynthesis do?

Answer 3

photosynthesis generates a chemical store of energy in the form of carbohydrates

it converts light energy to chemical energy

Question 4

give an example of an autotroph

Answer 4

photosynthetic organisms

Question 5

give a brief summary of light dependent reaction?

Answer 5

use light energy to produce ATP and to split water (photolysis), making H+ ions

Question 6

give a brief summary of light independent reaction?

Answer 6

use ATP and H+ ions to “fix” CO2, making glucose

Question 7

what is photolysis?

Answer 7

light splits 6H2O into O2 and H+ ions

Question 8

what happens to the products of photosynthesis?

Answer 8

• some oxygen is a waste product
• glucose is either used for respiration or stored as starch

Question 9

Why will desert plants die if they carry out light independent reactions? and what are these plants called?

Answer 9

• stomata is open b/c needed for gas exchange
• but cause too much transpiration and die from dehydration, so do light independent reaction at night

Question 10

some plants close their stomata during the day and take up CO2 at night, when the air temperature is lower. what are these plants called?

Answer 10

CAM plants

Question 11

what are the 2 polysaccharide molecules found in plants? and what are they used for?

Answer 11

• starch is a chemical store of energy
• cellulose builds up the plant cell wall

Question 12

What is the process through which monosaccharides are combined to make carbohydrates?

Answer 12

glucose + glucose → (C6H10O5)n

• condensation
• bond in product called glycosidic bond → covalent bond

Question 13

what is the bond between monosaccharides when they are combined?

Answer 13

glycosidic bond (a covalent bond)

Question 14

what helps absorb different wavelength of color in plants?

Answer 14

pigments

= chlorophyll (in the organelle chloroplast)

Question 15

why does a leaf look green?

Answer 15

• chlorophyll is the main photosynthetic pigment
• white light = all colors (wavelengths)
• in plants, blue and red wavelengths are absorbed, green light is reflected

Question 16

why do leaves die in autumn?

Answer 16

• not a lot of sunlight
• less area of plant that needs to be kept alive through respiration

Question 17

why should a plant make different pigments to absorb different wavelengths of light?

Answer 17

• to maximise light that it can absorb

the pigments in photosynthetic organisms (chlorophyll), absorb useful wavelengths of light

Question 18

can low frequency radiation be used in most organisms?

Answer 18

low frequency radiation is low in energy - too low to be used in most organisms

Question 19

what is the y axis of the absorption spectrum?

Answer 19

• y axis: absorption of light
• how much light was absorbed

Question 20

what can be observed on the absorption spectrum?

Answer 20

• how much light was absorbed
• blue + red high, green low

Question 21

what is the y axis of the action spectrum?

Answer 21

y axis: rate of photosynthesis

• how much of that light was used in photosynthesis

Question 22

what does the action spectrum show?

Answer 22

• how much of that light was used in photosynthesis
• blue higher than red?

Question 23

is CO2 a limiting factor for light independent reaction?

Answer 23

yes

Question 24

oxygen is a ______ of photosynthesis

Answer 24

by-product

usually a waste product

Question 25

where does oxygen in photosynthesis comes from? (in simple terms)

Answer 25

from photolysis (splitting of H2O)

Question 26

what is the effect of photolysis on the concentration of oxygen inside chloroplasts and explain

Answer 26

• photolysis increases concentration of oxygen inside chloroplasts
  
  • causes oxygen to diffuse out of chloroplasts then out of leaf cells to air spaces inside the leaf
  • oxygen diffuses thru stomata to the air outside the leaf

Question 27

what is cyanobacteria and explain

Answer 27

• cyanobacteria
  
  • when there was no oxygen
  • able to carry out photosynthesis
  • only possible if oxygen conc (around 30%) was really high
  • cyanobacteria was really good at releasing oxygen
  • eukaryotes ingested cyanobacteria and inherited its abilities
  • endosymbiosis occurred