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Flashcards in lecture 4 Photosynthesis Deck (50)
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What does Photosynthesis mean?

“Synthesis using light” and it is process of biological importance which involves conversion of solar energy of the chemical energy producing organic compounds


The photosynthetic process takes place in what kind of plants?

Under natural conditions, the photosynthetic process takes place in plants that are continuously responding to internal and external change


What does the amount of light CO2 determine?

The amount of light CO2 determine the photosynthetic response of plants and multiple level of control over the process of photosynthesis allows plants to grow successfully in changing environments and diverse habitats.


What are plant physiologists interested in?

Plant physiologists are interested to understand the effect of environmental factors such as light, CO2 concentration and temperature on photosynthesis


The photosynthetic process is important for? but why?

The photosynthetic process is important for agronomists because plant productivity and crop yield depends on photosynthetic efficiency in a dynamic environment


What are the names for the 3 major steps in the process of photosynthesis?

1)The light reactions

2)uptake of carbon dioxide

3)Carbon dioxide fixation


What does step 1 involve?

involves the light reactions which capture light energy to be used for reduction of NADP and formation of ATP. These energy rich compounds are later used in the synthesis of sugars and complex organic molecules


What does step 2 involve?

Involves the uptake and diffusion of carbon dioxide to the reaction centre in the chloroplast


What does step 3 involve?

Is the fixation of carbon dioxide to synthesize carbohydrate, involving the calvin cycle


In the light reaction, visible light is absorbed by?

the chlorophyll molecules which are located in thylakoid membranes of the chloroplast


How are the light photons captured?

The light photons are captured by chlorophyll (a and b) the green pigment molecules and the excitation energy is transferred to a chemical acceptor


What is the result of the photosynthetic electron transfer process?

the end result is the production of reducing power (NADPH) and the synthesis of ATP


What happens in the chemical reactions in which water is oxidized to oxygen?

NADP is reduced, and ATP is formed, take place in the thylakoid membrane, are known as thylakoid reactions


What is the chemical energy of NADPH and ATP later used for?

The chemical energy of NADPH and ATP is later used for the fixation of carbon dioxide into carbohydrates.


What is leaf used for in photosynthesis?

Leaf - the primary site of photosynthesis and internal structure of the chloroplast


In chloroplast, light energy is converted into?

chemical energy by two different photosystems.


What are these photosystems and what do they do?

These photosystems are known as photosystem and photosystem 2, which carry out early energy storage reactions in the process of photosynthesis.


Explain Photosystem 1

Photosystem 1 absorbs far-red light of wavelength greater than 680 nm and produces strong reductant capable of reducing NADP+


Explain Photosystem 2

Photosystem 2 absorbs the light of 680 nm and produces very strong oxidant capable of oxidizing water.


What do both Photosystems have?

Both photosystems have specific antenna pigments and photochemical reaction centre which are linked by an electron transport chain


What is the fraction of the captured light also used for?

Fraction of the captured light is also used for light-dependant ATP synthesis, known as photophosphorylation.


What is the process of the uptake of carbon dioxide?

The uptake of carbon dioxide is a diffusion process


How do the Carbon dioxide molecules move?

Carbon dioxide molecules move by diffusion down a concentration gradient from the atmosphere into the leaf entering through the stomata


What are the stomata?

The stomata are pores of the leaf surface, each of which are formed by two guard cells responsible for opening and closing like a valve, which is controlled by changes in turgor pressure inside the guard cells.


What happens to the carbon dioxide molecules do after they pass through the stomata?

After passing through stomata, the carbon dioxide molecules diffuse through the intercellular spaces, entering the mesophyll cells which contain the chloroplasts. Once in the chloroplast, the fixation process can take place using a special enzyme - Rubisco.


What does C3 fixation refer to?

C3 fixation refers to the production of a 3 carbon compound (Phosphoglycerate) as the first stable product of photosynthesis


What do a number of important crop plants and major natural vegetation plants in the sub-tropics do instead of C3 fixation?

C4 fixation


What is Net photosynthesis?

Net photosynthesis is a function of a both photosynthesis and respiration i.e

Net Photosynthesis = Gross Photosynthesis – Gross Respiration
↓ ↓ ↓
Net uptake of CO2 =Gross uptake of CO2 by fixation – Gross evolution of CO2 by dark and photo-respiration


What is the most abundant enzyme?

RuBisCO is the most abundant enzyme (Protein) in the world since it is present in every plant that undergoes photosynthesis


Where is the enzyme RuBisCO located?

The enzyme RuBisCO is located in the stroma of chloroplasts and used in the Calvin Cycle to catalyze the first major step of carbon fixation.