CH-11: Photosynthesis in Higher Plants - SET 1

Question 1

What kind of a process is photosynthesis?
(3 keywords)

Answer 1

1. Anabolic
2. Endergonic
3. Oxido-reduction process

Question 2

Which early experiment demonstrated that CO2 is necessary for photosynthesis?

Answer 2

Moll’s half leaf experiment

Question 3

Which scientist revealed the essential role of air in the growth of green plants through several experiments and when?

Answer 3

Joseph Priestly in 1770

Question 4

Who discovered oxygen and when?

Answer 4

Joseph Priestly in 1774

Question 5

What hypothesis was given by Priestly?

Answer 5

Plants restore to the air whatever breathing animals and burning candles remove.

Question 6

What did Jan Ingenhousz show through his experiments?

Answer 6

1. Sunlight is essential for the plant process that helps to somehow purify the air fouled by the breathing mouse and the burning candle
2. Presence of sunlight is necessary for the release of oxygen

Question 7

Which aquatic plant did Jan Ingenhousz use for his experiment?

Answer 7

Hydrilla

Question 8

What did Julius von Sachs find?

Answer 8

1. Green parts is where glucose is made
2. Glucose is usually stored as starch
3. The green substance in plants (now k/a Chlorophyll) is located in special bodies in plant cells (now k/a Chloroplast)

Question 9

Which organism did T.W. Engelmann experiment on?

Answer 9

A green alga, Cladophora

Question 11

What was the purpose of placing the illuminated Cladophora in a suspension of aerobic bacteria in T.W. Engelmann’s experiment?

Answer 11

The bacteria were used to detect the sites of oxygen evolution

Question 12

What did T.W. Engelmann observe during his experiment on Cladophora?

Answer 12

He found that the bacteria accumulated mainly in the region of blue and red light of the light spectrum. Thus, the first action spectrum of photosynthesis was described.

Question 13

On what organisms were the studies of Cornelius van Niel’s studies based?

Answer 13

Purple and green sulphur bacteria

Question 14

What did the studies of Cornelius van Niel demonstrate?

Answer 14

The studies demonstrated that during photosynthesis, hydrogen released from a suitable oxidizable compound reduces CO2 to carbohydrates

Question 15

What did Cornelius van Niel infer?

Answer 15

He inferred that oxygen evolved by the green plants comes from H20 and not from CO2

Question 16

How was the hypothesis of Cornelius van Niel proved later?

Answer 16

The hypothesis was later proved using radioisotopic techniques

Question 17

Who proved that O2 evolved during light reaction comes from H20 and not from CO2? What did they use to prove so?

Answer 17

Ruben, Kaben et.al.
They used a heavy but non-radioactive, stable isotope of oxygen O-18

Question 18

What is PAR?

Answer 18

Photosynthetically Active Radiation
(The part of spectrum used in photosynthesis having wavelength between 400-700 nm)

Question 19

What is the most active photosynthetic tissue in higher plants?

Answer 19

Mesophyll of leaves

Question 20

What is the third system of membranes possessed by chloroplasts known as?

Answer 20

Thylakoids

Question 21

What is a stack of thylakoids known as?

Answer 21

Granum

Question 22

What are the adjacent grana connected by?

Answer 22

Stroma lamellae

Question 23

What is the fluid compartment surrounding the thylakoids known as?

Answer 23

Stroma

Question 24

What do the proteins and pigments which are embedded in the thylakoid membrane function as?

Answer 24

They function in the photochemical events of photosynthesis i.e. trapping the light energy and synthesis of ATP and NADPH

Question 25

What happens in the stroma of a chloroplast?

Answer 25

In stroma, enzymatic reactions synthesize sugar, which in turn forms starch

Question 26

What are the former and the latter set of reactions of photosynthesis known as? Why are they called so?

Answer 26

Former set - Light reactions (Photochemical reactions) Latter set - Dark reactions (Carbon reactions) They are called so because the former set of reactions are directly light driven while the latter set of reactions are not directly light driven but are dependent on the products of the light reactions (ATP and NADPH)

Question 27

Name the technique used to separate leaf pigments.

Answer 27

Through paper chromatography

Question 28

"The color of leaves is due to four pigments." Name them and also mention the color they impart.

Answer 28

1. Chlorophyll a -- Bright or blue-green 2. Chlorophyll b -- Yellow-green 3. Xanthophylls -- Yellow 4. Carotenoids -- Yellow to yellow-orange

Question 29

Define pigments.

Answer 29

Substances that have an ability to absorb light, at specific wavelengths

Question 30

Name the primary photosynthetic pigment.

Answer 30

Chlorophyll a

Question 31

What kind of structure does the molecule of chlorophyll have?

Answer 31

Tadpole-like structure

Question 32

What are the two main parts of a chlorophyll molecule?

Answer 32

Porphyrin head and Phytol tail

Question 33

Give three characteristics of the Porphyrin head.

Answer 33

1. All chlorophylls have a complex ring-like structure chemically related to the porphyrin-like groups found in haemoglobin and cytochromes 2. Site of electrons rearrangements when the chlorophyll is excited 3. A cyclic tetrapyrrolic structure with non-ionic magnesium atom

Question 34

Give two characteristics of the Phytol tail.

Answer 34

1. Long hydrocarbon tail is almost always attached to the ring-like structure 2. Anchors the chlorophyll to the hydrophobic portion of the thylakoids

Question 35

Name the major types of chlorophylls.

Answer 35

Chlorophyll a, b, c, d, e Bacteriochlorophyll a and b

Question 36

What are accessory pigments?

Answer 36

All pigments other than chlorophyll a are called accessory pigments

Question 37

Mention the two major roles of accessory pigments in photosynthesis.

Answer 37

1. Absorb light of different wavelengths and transfer the energy to chlorophyll molecules (Thus also k/a "Antenna molecules") This enables a wider range of wavelength of incoming light to be utilized for photosynthesis 2. Carotenoids protect the plant from excessive heat and prevent photo-oxidation (oxidative destruction of light) of chlorophyll pigments. (Thus also k/a "Shield Pigments")

Question 38

Which chlorophyll accounts for about one-fourth of the total chlorophyll content?

Answer 38

Chlorophyll b

Question 39

What is absorption spectrum?

Answer 39

The graphic curve showing the amount of energy of different wavelengths of light absorbed by a substance/ pigments

Question 40

What is action spectrum?

Answer 40

The graphic curve showing the relative rates of photosynthesis at different wavelengths of light

Question 41

What do the graphs of action and absorption spectrum show?

Answer 41

They show that most of the photosynthesis takes place in the blue and red regions of the spectrum Some photosynthesis does take place at the other wavelengths of the visible spectrum The graphs depict that maximum photosynthesis occurs at the wavelength at which there is maximum absorption by chlorophyll a i.e. in the blue and red regions

Question 42

Why do the chloroplasts align themselves along the walls of the mesophyll cells?

Answer 42

1. For easy diffusion of gases 2. To receive optimum quantity of incident light

Question 43

Why do the chloroplast align themselves in vertical positions along the lateral walls of the mesophyll cells?

Answer 43

The chloroplast align themselves in vertical positions along the lateral walls of the mesophyll cells under high light intensities to protect themselves or the pigment system against destruction of light.

Question 44

Where do the dark reactions of photosynthesis occur?

Answer 44

Stroma

Question 45

Moll's half leaf experiment was done to show that _______ was required for photosynthesis.

Answer 45

CO2

Question 46

A milestone contribution to the understanding of photosynthesis was made by Cornelius van Niel, which was based on the studies of?

Answer 46

Green and purple sulphur bacteria

Question 47

The essential role of air in the growth of green plants was revealed by?

Answer 47

Joseph Priestly

Question 48

The curve showing the effectiveness of different wavelengths of light in photosynthesis was first given by Engelmann using?

Answer 48

1. Filamentous green alga, Cladophora 2. Suspension of aerobic bacteria 3. Prism to split the light in its components