photosynthesis

Outline the source of atoms used to form glucose during photosynthesis.

[2]

Carbon and oxygen atoms come from carbon dioxide; hydrogen atoms come from water.

Outline the process of peat formation.

[4]

formed from dead plant material/leaves/mosses/Sphagnum 1 mark

b. formed in waterlogged sites/bogs/mires/swamps 1 mark

c. where bacteria/fungi/saprotrophs are not active/are inhibited 1 mark

d. organic matter not fully decomposed 1 mark

Describe the process of photosynthesis.

[8]

a. autotrophs perform photosynthesis

b. carbon dioxide and water are the reactants/raw materials required for photosynthesis

c. light splits water molecules/causes photolysis

d. photolysis releases oxygen as a waste product

e. light energy is converted into chemical energy

f. photosynthesis produces organic compounds/glucose/carbohydrates

g. photosynthesis occurs in chloroplasts

h. chlorophyll photosynthetic pigment absorbs light

i. different pigments absorb different wavelengths of light

j. chlorophyll absorbs red and blue light/ends of the spectrum

k. carbon dioxide concentration/temperature/light intensity are limiting factors

Explain the conversion of light energy to chemical energy during photosynthesis. (4)

1. Absorption of light by chlorophyll. 1 mark

2. Conversion of light energy into chemical energy in the form of ATP and NADPH. 1 mark

3. Use of ATP and NADPH in the Calvin cycle to fix carbon dioxide into glucose. 1 mark

6CO2+6H2O+light energy→C6H12O6+6O2

Outline how chromatography can be used to separate photosynthetic pigments and explain how Rf values are calculated. (4)

• Apply a sample of plant extract onto a chromatography paper or plate 1 mark

• Place the paper/plate in a solvent 1 mark

• As the solvent moves up the paper/plate, it carries the pigments with it 1 mark

• Different pigments travel at different rates due to differences in solubility and affinity for the paper/plate, resulting in separation 1 mark

This experiment measured the quantity of oxygen gas released by the water plant. State one other way of measuring the rate of photosynthesis.

• measure co2 absorption/decrease

• measure increase in biomass

• rise in ph

The fungus Rhytisma grows on the leaves of certain trees, causing a yellow leaf area in which chlorophyll is no longer present. A black, tar-like stain later spreads out.

What happens in the leaf when Rhytisma is present?

I. An increase in the intake of carbon dioxide

II. A reduction in the production of oxygen

III. An increase in the loss of water

Only 2. when Rhytisma is present, the chlorophyll in the affected area is no longer present, meaning photosynthesis cannot occur in that region. Since photosynthesis is the process that uses carbon dioxide, its absence would not lead to an increase in carbon dioxide intake. absence of chlorophyll in the affected area prevents photosynthesis, which is the process responsible for oxygen production.

Compare and contrast the mode of nutrition of detritivores and saprotrophs.

[2]

both are heteotropic and feed on dead matter

detirivors interally digest butsaprotrops secrete enzymes to externally digst

State one cause of variation in a plant such as the sweet potato

. mutations; 1 mark

b. meiosis/crossing over/random assortment of homologous pairs; 1 mark

c. sexual reproduction/recombination/random fertilisation; 1 mark

Which substance(s) is (are) used to make organic molecules during photosynthesis?

I. Carbon dioxide

II. ATP

III. Oxygen

IV. Water

1 2 and 4 because ATP is used apparently

Explain how detritivores obtain nutrition and the effects they have in ecosystems.

[4]

• Detritivores obtain nutrition from detritus/waste/dead bodies; 1 mark

• They are heterotrophic; 1 mark

• They facilitate further decomposition; 1 mark

• They contribute to the supply of inorganic nutrients for autotrophs/nutrient cycling

explaint how plants capture and use light in photosynthesists

• Plants convert light energy into chemical energy by photosynthesis; 1 mark

• Photosynthesis takes place in chloroplasts; 1 mark

• Chloroplasts contain the pigment chlorophyll; 1 mark

• Chloroplasts/chlorophyll in plants absorb sunlight; 1 mark

• Chlorophyll absorbs red AND blue light most effectively; 1 mark

• Light causes photolysis/splits water molecule; 1 mark

• Carbon dioxide AND water are reactants in photosynthesis; 1 mark

• Glucose AND oxygen are products of photosynthesis; 1 mark

• Light intensity is a limiting factor for the rate of photosynthesis; 1 mark

• Organic/carbon compounds/glucose provide food/stored energy for plant itself, animals, food chains; 1 mark

outline role of amylase (4)

• Amylase is an enzyme; 1 mark

• Secreted by salivary glands/pancreas; 1 mark

• Active/released into the mouth/small intestine; 1 mark

• Acts on starch/polysaccharides; 1 mark

• Breaks «glycosidic» bond by hydrolysis/adding water; 1 mark

• Converts insoluble/large molecule to soluble/small molecules; 1 mark

• Product is maltose/disaccharide/sugar molecule; 1 mark

In which process of photosynthesis is light directly involved?

photolysis (spllitting of water)

Explain how increasing levels of atmospheric carbon dioxide can impact plant growth, with reference to carbon dioxide enrichment experiments.

[5)

1 mark Increased levels of atmospheric carbon dioxide can enhance plant growth due to increased rates of photosynthesis, as carbon dioxide is a key reactant in the photosynthesis process.

1 mark Carbon dioxide enrichment experiments have shown that higher concentrations of CO2 can lead to increased biomass production and improved water-use efficiency in plants.

1 mark However, the response can vary depending on the plant species, availability of other nutrients, and environmental conditions.

1 mark Some experiments also indicate that there may be a saturation point beyond which additional CO2 does not further enhance growth.

1 mark Additionally, increased CO2 levels can lead to changes in plant structure and function, such as altered leaf morphology and reduced stomatal density.