Biology

Photosynthesis in Plants

1,508 Questions

Photosynthesis is the biological process by which plants convert light energy into chemical energy. This page contains practice questions covering essential topics like chlorophyll, light reactions, and the pathways specific to plants. This material is crucial for medical entrance exams and academic assessments.

Chlorophyll and pigmentsLight reactionsCalvin cycleCAM plantsElectron transportPhotosynthesis factors

Photosynthesis in Plants Questions

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

Which "photosynthetic bacteria" possess both PS I and PS II

  1. Purple sulphur bacteria.

  2. Cyanobacteria.

  3. Purple nonsulphur bacteria.

  4. Green sulphur bacteria.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Photosynthetic bacteria posses only one type of photosystem and are mostly anaerobic and contains two type of pigment bacteriochlorophylls and bacterioviridin while cyanobacteria or blue-green algae posses two photosystems  PS I and PS II.

So the correct option is 'Cyanobacteria'.

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

PS I has

  1. More chlorophylls and more accessory pigments

  2. More chlorophylls and less accessory pigments

  3. Less chlorophylls and more accessory pigments

  4. Less chlorophylls and less accessory photosynthetic pigments
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Photosystem I is one of the two membrane-bound photosystems of plants, algae and cyanobacteria that facilitate light-determined electron transport from water to NADPH. It utilizes absorbed light for electron transport from plastocyanin on the lumenal side to ferredoxin on the stromal side of the thylakoid membrane. In plants, this special integral membrane complex consists of more than 15 protein subunits, approximately 175 chlorophyll molecules, 2 phylloquinones and 3 Fe$ _4$S$ _4$ clusters. Whereas Photosystem II (of cyanobacteria and green plants) is as many as 35 chlorophyll a, 12 beta-carotene, two pheophytins, two plastoquinone, two heme, one bicarbonate, 20 lipid molecules and other ionic clusters. Thus Photosystem I contains more chlorophylls and accessory pigments.

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

DCMU inhibits

  1. PS II

  2. PS I

  3. Destroys chloroplast

  4. Inhibits oxidative phosphorylation
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

DCMU or Dichlorophenyl dimethyl urea inhibits PS II in photosynthetic plants by blocking electron transfer from plastoquinone to cytochrome. DCMU binds to and blocks the site of plastoquinone, thus hinders the path and growth of plants. It is used as herbicide and algicide. It is also used in studying photosynthetic activity.

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

Photosynthesis II is concerned with

  1. Photolysis of water

  2. Flowering
  3. Reduction of CO$ _2$

  4. Release of energy
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Being a light reaction, non-cyclic photophosphorylation occurs in the thylakoid membrane. First, a water molecule is broken down into 2H+ + 1/2 O2 + 2e− by a process called photolysis (or light-splitting). The two electrons from the water molecule are kept in photosystem II, while the 2H+and 1/2O2 are left out for further use. Then a photon is absorbed by chlorophyll pigments surrounding the reaction core center of the photosystem. The light excites the electrons of each pigment, causing a chain reaction that eventually transfers energy to the core of photosystem II, exciting the two electrons that are transferred to the primary electron acceptor, pheophytin. The deficit of electrons is replenished by taking electrons from another molecule of water. 


So, the correct option is 'Option A'.

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

PS I is inactive at

  1. 550 nm

  2. 680 nm

  3. 690 nm

  4. 780 nm
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A) PS I can funtion at wavelengths of 700 nm or less. So, it will be active at 550 nm. But its maximum activity is at 700 nm.
B) It will be active at 680 nm.
C) It will be active at 690 nm.

D) PS I cannot function at wavelengths greater than 700 nm.
So the correct answer is '780 nm'.

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

A photosystem Contains

  1. pigments, a reaction centre, and an electron acceptor
  2. ADP1 P1 and hydrogen ions $(H^+)$

  3. protons, photons and pigments

  4. both (b) and (C)
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Photosystems refer to PSI and PSII. Photosystem II contains chlorophyll a, as well as up to 50% chlorophyll b. It probably evolved later as a supplement to Photo I. It is needed to capture enough energy to do the biosynthetic reactions of the dark reaction. Its reaction centre is a molecule called P680 which absorbs light maximally at 680 nm. Similarly, PSI or P700 absorbs light at 700nm. A reaction centre comprises several (>10 or >11) protein subunits, that provide a scaffold for a series of cofactors. The cofactors can be pigments (like chlorophyll, pheophytin, carotenoids), quinones, or iron-sulfur clusters and electron acceptors for transduction in the electron transport chain. 

So, the correct option is, 'pigments, a reaction centre, and an electron acceptor'.

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

The active component of photosystem-I composed of

  1. chlorophyll-a with absorption peak at 680 nm

  2. chlorophyll-a with absorption peak at 700 nm

  3. chlorophyll-b with absorption peak at 680 nm

  4. chlorophyll-a chlorophyll-b with absorption peak at 700 nm
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
The reaction center of photosystem-I is composed of two chlorophyll molecules and is therefore referred to as a dimer. The dimer is composed of one chlorophyll a molecule and one chlorophyll a' molecule with absorption peak at 700 nm.
Thus, the correct answer is 'chlorophyll a with absorption peak at 700 nm.'
Multiple choice biology protectors of biosphere structure of chloroplast plastids photosynthetic pigments

Which of the following processes forms chemical potential energy from electromagnetic energy?

  1. Respiration

  2. Photosynthesis

  3. Decomposition

  4. Nitrogen fixation

  5. Fermentation
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Electromagnetic energy is the same as radiation or light energy. This type of kinetic energy can take the form of visible light waves, like the light from a candle or a light bulb, or invisible waves, like radio waves, microwaves, x-rays and gamma rays. Further, irrespective of where radiation is coming from, it can travel in a vacuum. The electromagnetic energy in plants can be converted to stored chemical energy during photosynthesis. 

Multiple choice biology protectors of biosphere structure of chloroplast plastids photosynthetic pigments

Which of the following is responsible for the red, orange and yellow colour of leaves?

  1. Carotenoids

  2. ATP

  3. Leaf decay

  4. Chlorophyll

  5. Over abundance of water
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Option 'A' is correct.

Carotenoids are responsible for the red, orange and yellow color of leaves. Carotenoids are present with chlorophyll, but in summer the leaves are green because of high levels of chlorophyll. Summer masks the color of carotenoids, During autumn, the color of carotenoids becomes more noticeable because of the degradation of chlorophyll. As the autumn progresses, carotenoids also degrade along with chlorophyll but at a much slower rate. Hence the yellow, orange, red colors become visible.   

Multiple choice biology protectors of biosphere structure of chloroplast plastids photosynthetic pigments

The light is trapped by photosynthetic pigments presents in the 

  1. Stroma

  2. Grana

  3. Quantosomes

  4. Periplastidial space
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The chloroplast is the cell organelles present in plant cells that are responsible for initiating the process of photosynthesis. Chloroplasts are double-membrane bound structures. The stroma of chloroplast is the jelly-fluid like structure in which another membrane system is presently called the thylakoids. These thylakoids are stacked upon each other to form the structure called grana. The grana are connected with each other by an extension of thylakoids called stroma lamellae. Thylakoid of grana has the photosynthetic pigments embedded in it that perform the trapping of sunlight and begin the light reaction of the photosynthesis.

A. Stroma is the region where the dark reaction of the photosynthesis occurs.
B. Grana is the region where the light reaction occurs through the trap of light by the photosynthetic pigment.
C. Quantasomes are the photosynthetic units made of pigments and are present in the grana.
D. Periplastidial space is the region between the inner membrane and the outer membrane of the plastids.
Hence, the correct answer is 'Grana'

Multiple choice biology protectors of biosphere structure of chloroplast plastids photosynthetic pigments

Chloroplast stroma contains

  1. Chlorophyll

  2. Light dependent reaction enzymes

  3. Light independent reaction enzymes

  4. Ribosomes
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In photosynthesis, light-independent reactions are known as dark reactions. This process does not depend directly on the presence of light but is dependent on the products of light reaction i.e., ATP and NADPH. The dark reactions occur through Calvin cycle. They take place in the stromal matrix of the chloroplast. Chloroplast stroma contains light independent reaction enzymes which are required for the reaction. Thus, the correct answer is option C.

Multiple choice biology protectors of biosphere structure of chloroplast plastids photosynthetic pigments

Where does the primary photochemical reaction occurs in chloroplast ? Where does the light reaction of photosynthesis taken place?

  1. Stroma

  2. Endoplasmic reticulum

  3. Quantasome or thylakoids (Grana)

  4. Inner membrane of chloroplast
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In the chloroplast, the primary photochemical reactions occur. During photosynthesis, primary reactions like the light-capturing and ATP-generating reactions occur on grana. Grana are stakes of thylakoids. Quantasomes are particles found in grana. During photosynthesis, the light-dependent reactions take place on the thylakoid membranes. The inside of the thylakoid membrane is called the lumen. Light-independent reactions take place in the stroma. 

Thus, the correct answer is 'Quantasome or thylakoids (Grana).'

Multiple choice biology protectors of biosphere structure of chloroplast plastids photosynthetic pigments

Which of the following absorb light energy for photosynthesis : -

  1. Chlorophyll

  2. Water molecule
  3. O$ _{2}$

  4. RUBP
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
A pigment is a compound that absorbs a particular wavelength of visible light. Chlorophyll is a green pigment contained in thylakoid membranes of chloroplasts that are used in photosynthesis by plants. The process of photosynthesis occurs when green plants use the energy of light to convert carbon dioxide (CO2) and water (H2O) into carbohydrates. Light energy is absorbed by chlorophyll, a photosynthetic pigment of the plant, while air containing carbon dioxide and oxygen enters the plant through the leaf stomata.

So, the correct answer is 'Chlorophyll'.
Multiple choice biology protectors of biosphere structure of chloroplast plastids photosynthetic pigments

In which of the following parts of the plant cell does photosynthesis occur?

  1. The chloroplasts

  2. The mitochondria

  3. The nucleus

  4. The endoplasmic reticulum
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The green parts of the plants have the chlorophyll pigment containing chloroplasts. The chloroplast is a type of plastid which plays a major role in the photosynthesis process.

Multiple choice biology protectors of biosphere structure of chloroplast plastids photosynthetic pigments

If 24 G-3-P molecule are formed in $C _3$ plants. Calculate 
a) the number of $CO _2$ used and 
b) the number of $G3P$ used for regeneration $RuBP$ molecule.

  1. a=12, b=20

  2. a=24, b=48

  3. a=12, b=24

  4. a=20, b=12
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
All together for one G3P to leave the cycle (and go towards glucose blend), three CO2 particles must enter the cycle, giving three new molecules of settled carbon. At the point when three CO2 particles enter the cycle, six G3P atoms are made. One leaves the cycle and is utilized to make glucose, while the other five must be reused to recover three atoms of the RuBP acceptor. 
3 CO2 joins with 3 RuBP acceptors, making 6 atoms of (G3P). 
1 G3P particle leaves the cycle and goes towards making glucose. 
5 G3P particles are reused, recovering 3 RuBP acceptor atoms.
So, the correct option is 'a=12, b=24'.