C1.3 Photosynthesis

Question 1

Compare the source of glucose for cellular respiration in mammals and flowering plants

Answer 1

Mammals are consumers hence they get nutrition from plants. Plants use carbon dioxide and energy from the sun trhoigh sunlight by absorbing it with chlorophyll to convert it to glucose andwater

Question 2

Explain how the energy transformation of light energy to chemical energy is needed for most life processes in ecosystems.

Answer 2

Process: photosynthesis

Converts light energy to chemical energy (in the form of glucose).

By-product / other product of photosynthesis is oxygen.

In ecosystems, food webs or chains usually start with a producers that convert light energy to chemical potential energy.

Photosynthesis is the only process on earth that converts light energy to chemical potential energy and produces enough of it to support life

Question 3

State what colour of light the pigment chlorophyll chiefly reflects and transmits

Answer 3

Green light

Question 4

Define the term photolysis

Answer 4

In the context of photosynthesis, photolysis refers to the process where light energy is used to split water molecules into oxygen and hydrogen.

Question 5

What is the formula for Rf value?

Answer 5

distance moved by sbstance/distance moved by solvent

• Rf value for chlorophyll a is 0.65

(Singapore’s independance, Singapore 1965 is an A grade nation)

• Rf value for chlorophyl b is 0.45 (think 90/2)

Question 6

Referring to the absorption spectrum, explain how light energy is transformed into chemical energy.

Answer 6

Within a pigment molecule, absorption of light excites electrons. Accessory pigments transfer excited electrons to chlorophyll a, which leads to a series of reactions that ultimately lead to the formation of glucose. Hence, light energy is transferred to chemical energy.

Question 7

C1.3.6—Similarities and differences of absorption and action spectra
Application of skills: Students should be able to determine rates of photosynthesis from data for oxygen
production and carbon dioxide consumption for varying wavelengths. They should also be able to plot
this data to make an action spectrum.

Question 8

Define the term limiting factor

Answer 8

A limiting factor for photosynthesis is an environmental factor that when in short supply, affects the rate of photosynthesis.

Question 9

Explain the effect pf increasing light intensity, CO2 concentration and temperature with photosynthesus using graphs (5-8 marks)