OCR A level Biology - Photosynthesis

Phospholipid bilayers play crucial roles within plant cells.
Which of the following statements linked to the importance of membranes in plant cells is / are true?

• ATP synthase embedded in thylakoid membranes maintains chemiosmotic gradients.

• Phospholipid bilayers within the chloroplast are impermeable to protons.

• Thylakoid membranes contain electron transport chain proteins.

The following graph shows the absorbance spectrum of an accessory pigment.

Which of the following statements explains why this pigment is orange-red to the human eye?

• The pigment absorbs green and blue light.

• The pigment has an absorption peak at 500 nm.

• The pigment passes photons to the primary pigment reaction centre.

RuBisCO is an enzyme that fixes carbon dioxide in photosynthesis. In some conditions, RuBisCO also carries out oxygen fixation.

The graph below shows how the carbon dioxide and oxygen fixing activities of RuBisCO are affected by temperature.

What are the correct percentage changes in RuBisCO carbon dioxide and oxygen fixing activities between 30 °C and 40 °C?

• carbon dioxide fixation – 12.7%, oxygen fixation 23.3%

• carbon dioxide fixation – 14.6%, oxygen fixation 18.9%

• carbon dioxide fixation – 2.4%, oxygen fixation 54.2%

• carbon dioxide fixation – 3.6%, oxygen fixation 35.1%

Mistletoe is a plant parasite that lives on the stems of other plants. It survives by removing water and assimilates from the host plant.

The mistletoe binds to the stem of the host plant and grows a specialised root-like tissue called a haustorium that attaches to different tissues in the stem.

One species of mistletoe, Viscum minimum, contains no chloroplasts.

Which of the options, A to D, explains why V. minimum does not need chloroplasts?

• the haustorium of V. minimum attaches to sieve tube elements

• the haustorium of V. minimum attaches to xylem vessels

• the haustorium of V. minimum attaches to meristem cells

• the haustorium of V. minimum attaches to cambium tissue

Which of the following, A to D, is a similarity in the way ATP is made in respiration and photosynthesis?

• both involve NAD

• both involve substrate level phosphorylation

• both involve photons

• both involve proton gradients

Cyanobacteria are photosynthetic prokaryotes.

A scientist exposed cyanobacteria to light of different colours and intensities and made the following observations:

Most cyanobacteria are blue in colour.

At low light intensities, glucose production in cyanobacteria is low.

When light intensity reaches a certain level the rate of glucose production in cyanobacteria stops increasing.

Which of the following statements, A to D, correctly explains these observations?

• The pigments in cyanobacteria absorb blue light and light intensity is a limiting factor for the rate of photosynthesis.

• The pigments in cyanobacteria absorb red light and light intensity is not a limiting factor for the rate of photosynthesis.

• The pigments in cyanobacteria absorb blue light and light intensity is not a limiting factor for the rate of photosynthesis.

• The pigments in cyanobacteria absorb red light and light intensity is a limiting factor for the rate of photosynthesis.

Which option is not a component of a chloroplast?

• Cristae

• DNA

• Ribosome

• Thylakoid

A class compared the number of chloroplasts in the leaves taken from plants of the same species growing in two areas. One area had a high light intensity, the other had a low light intensity.

Which option is the correct procedure for statistical analysis of the data collected by the class?

• Calculate the mean number of chloroplasts per cell in the high and low light intensity areas and use a paired t-test.

• Calculate the mean number of chloroplasts per cell in the high and low light intensity areas and use an unpaired t-test.

• Calculate the median number of chloroplasts per cell in the high and low light intensity areas and calculate Spearman’s rank correlation coefficient.

• Calculate the median number of chloroplasts per cell in the high and low light intensity areas and use a chi-squared test.

Which of the statements about the relationship between photosynthesis and aerobic respiration in plants is/are correct?

• During the day, photosynthesis produces all the ATP that cells in the leaves require.

• Carbon dioxide produced in respiration can be used as a carbon source in photosynthesis.

• Oxygen produced in photosynthesis can be used in aerobic respiration.

From which molecule is TP synthesised during the light-independent stage?