Photosynthesis

Where does most of a plant's biomass come from?

from the soil

From carbon dioxide from the air and water from the soil

From nutrients in the soil

from water

At midday, what is happening in the leaf of a plant?

Respiration

Photosynthesis

Mainly photosynthesis and some respiration

None of the above

At midnight, what is happening in the leaf of a plant?

Respiration

Photosynthesis

Photosynthesis and respiration

None of the above

The end product(s) of photosynthesis in plants are oxygen plus:

Glucose

Starch

Starch and Sucrose

Water

The gas evolved in bubbling pond weed in the light is

Pure carbon dioxide

Pure oxygen

Air enriched with O2 plus CO2 and N2

None of the above

Thinking about photosynthesis and respiration in plants, which statement is correct

Photosynthesis is the opposite of respiration

Photosynthesis and respiration both occur in plants

Only photosynthesis occurs in plants

Respiration for maintenance and growth only occurs in the dark

Light energy captured by photosynthesis is used in a plant for the synthesis of:

Carbohydrates

Carbohydrates, Fatty acids and Proteins

Fatty Acids and Proteins

None of the above

Photosynthesis takes place in two separate but dependant series of steps, the light reactions and the photosynthetic carbon reduction cycle; this second cycle (also known as the dark reaction / light independent stage / or the Calvin-(Benson-Bassham)* cycle) of photosynthesis occurs:

Only in the dark in intact plants

In the light and dark in intact plants

Only in the light in intact plants, although will work in the dark in a test-tube

None of the above

During the aforementioned photosynthetic carbon reduction cycle, some oxygen also interacts with the primary enzyme to produce a waste product (phosphoglycollate). Photorespiration is a salvage pathway which recovers some of this carbon, the rest being released in a process called “photorespiration”. Photorespiration occurs:

Instead of conventional respiration processes in the light

At a higher rate than conventional respiration processes in the light

To generate ATP for maintenance and growth

Water used in photosynthetic light reactions:

Is a significant proportion of leaf water

Leads to dehydration and drought stress;

Only uses 2 mols H2O per mol O2 evolved, relative to 1000 water vapour mols transpired

The “Z” scheme in photosynthesis represents:

Photosystems I and II, and electron transport components, that are evenly distributed throughout higher plant chloroplast thylakoid membranes

How Photosystems I and II are spatially separated between thylakoid stacks and intrathylakoid lamellae, coupled by mobile electron carriers which shuttle back and forth through the membrane

Shows how electrons are dislodged from chlorophyll by photons and transferred through the pigment bed to each reaction centre

Rainforests are often described as the ‘lungs of the earth’ which statement is correct:

we need them to renew the oxygen we breathe each year

Purify pollutants from the air

Are virtually carbon/oxygen neutral as respiration = photosynthesis across an annual cycle in an untouched forest

Not sure

Stratospheric Ozone is thinning and a “hole” occurs over Antarctica, which:

Causes global warming by increasing radiation absorbed from sunlight

is caused by CO2 emissions

allows dangerous uv radiation to penetrate causing cancer and blindness in animals

Leads to atmospheric warming due to uv radiation

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