Photosynthesis: 15 MCQs with answers

To convert light energy into chemical energy.

Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll. This process converts light energy into chemical energy stored in glucose.

Carbon Dioxide

The general equation for photosynthesis is $6CO_2 + 6H_2O + \text{light energy} \rightarrow C_6H_{12}O_6 + 6O_2$. Carbon dioxide ($CO_2$) is a key reactant.

Chloroplasts

Chloroplasts are the organelles within plant cells that contain chlorophyll and are the sites where photosynthesis occurs.

Light energy from the sun

Photosynthesis literally means 'synthesis using light'. Sunlight provides the initial energy input for the entire process.

Oxygen

The splitting of water molecules ($H_2O$) during the light-dependent reactions releases oxygen ($O_2$) as a byproduct.

Roots

Plant roots are specialized structures designed to absorb water and dissolved minerals from the soil, which are then transported to the leaves for photosynthesis.

True

The light-dependent reactions of photosynthesis require sunlight, so the entire process is generally considered to occur during the day when light is available.

False

Photosynthesis is a process performed by plants, algae, and some bacteria, not animals. Animals are consumers and obtain energy by eating other organisms.

True

Glucose ($C_6H_{12}O_6$) is the primary carbohydrate produced during photosynthesis, serving as the plant's food source.

Chlorophyll

Chlorophyll is the green pigment found in chloroplasts that absorbs light energy, particularly in the red and blue parts of the spectrum, to initiate photosynthesis.

ATP and NADPH

The light-dependent reactions convert light energy into chemical energy in the form of ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate), which are then used in the light-independent reactions.

Carbon Dioxide

The Calvin cycle takes the ATP and NADPH produced during the light-dependent reactions and uses them to fix carbon dioxide from the atmosphere into glucose.

$6O_2$

The balanced chemical equation for photosynthesis shows that six molecules of oxygen ($6O_2$) are produced along with one molecule of glucose.

They regulate the exchange of gases (CO2 and O2) with the atmosphere.

Stomata are small pores on the surface of leaves that open and close to allow for the intake of carbon dioxide and the release of oxygen and water vapor.

It produces organic food molecules and oxygen, supporting most food chains and aerobic respiration.

Photosynthesis is fundamental because it converts light energy into chemical energy (food) that sustains nearly all life forms, either directly (herbivores) or indirectly (carnivores), and it releases the oxygen necessary for aerobic respiration.