5.5 Energy for Biological Processes Flashcards
What is photosynthesis ?
Where organisms make use of the energy in the bonds of organic molecules, such as glucose. These bonds are formed during photosynthesis in plants. Light is trapped by chlorophyll molecules and this energy is used to drive the synthesis of glucose.
What is the equation for photosynthesis ?
6CO2 + 6H2O = C6H12O6 + 6O2
What is the equation for respiration ?
C6H12O6 + 6O2 = 6CO2 + 6H2O
What is respiration ?
Process by which organic molecules, such as glucose, are broken down into smaller inorganic molecules. The energy stored within bonds is used to synthesise ATP.
What are exothermic reactions ?
Overall reaction releases energy.
What are endothermic reaction ?
Overall reaction takes in energy.
What is ATP ?
ATP is the universal energy currency in cells. The bond energy is used to drive essential metabolic processes.
How is ATP used in photosynthesis ?
Energy from sun provides energy to form chemical bonds in ATP. ATP is then used to to build large organic molecules. Bonds in glucose is broken down to reform ATP, which is then broken down for metabolic processes.
What is chemiosmosis ?
Involves the diffusion of protons from high to low concentration through a partially permeable membrane.
What does chemiosmosis depend on ?
Depends on the creation of a proton concentration gradient. The energy to do this comes from a high-energy electrons.
How are electrons excited ?
Electrons are excited by absorbing light from the sun. High energy electrons are released when chemical bonds are broken in respiratory substrate molecules. The excited electron pass into electron transport chain.
What is the electron transport ?
Electron transport chain is made up of series of electron carriers, each at lower energy levels. As high energy electrons move through carriers, energy is released allowing H+ to be pumped across membrane.
What happens when electrochemical gradient is established in electron transport chain ?
H+ move through membrane down ATP synthase. This flow of protons provides energy used to synthesise ATP from ADP and Pi.
What is autotrophic ?
Organisms that can photosynthesise to produce their own food.
What is heterotrophic ?
Organisms that obtain complex molecules by eating other organisms.
Structure of chloroplasts
Membrane forms flattened sacs known as thyloakoid membranes stacked to form grana, which are joined by lamellae. Has chlorphyll and fluid called stroma.
What are pigment molecules ?
Absorb specific wavelengths of light and reflect others. Different pigments absorb and reflect different wavelengths.
What is chlorophyll in terms of pigment ?
Absorbs mainly red and blue light and reflects green light. Primary pigment is chlorphyll a.
What is a light harvesting system ?
Chlorophyll b, xanthophylls and carotenoids embedded into thylakoid membrane. These form light harvesting system. Role is to absorb light energy and transfer this to the reaction centre.
What is the light harvesting system and reaction centre known as ?
Known as a photosystem.
What is a light dependent stage ?
Energy from sunlight is absorbed and used to form ATP. Hydrogen from water is used to reduce coenzyme NADP to reduced NADP.
What is the light independent stage ?
Hydrogen from reduced NADP and CO2 is used to build inorganic molecules such as glucose. ATP supplies the required energy.
What is the light dependent stage during PS2 ?
PS2 releases excited electrons and ATP is produced by chemiosmosis. Electrons lost are replaced by photolysis of water.
What is the light dependent stage during PS1 ?
Excited electrons are released from PS1 passed to another electron transport chain and ATP is produced again by chemiosmosis. Electrons lost are replaced by electrons that have travelled along first ETC from PS2. Electron leaving are accepted with H+ with NADP to form reduced NADP.
What does reduced NADP do ?
Provides hydrogen or reducing power in production of organic molecules, such as glucose, in the light independent stage which follows.
What is the photolysis of water ?
Water splits into hydrogen ions, electrons and oxygen molecules using energy from the sun.
What is cyclic phosphorylation ?
Electrons leaving the electron transport chain after PS1 can be returned there instead of producing reducing NADP.
Where does light independent stage takes place ?
Stroma of chloroplats.
Where does light dependent stage take place ?
Thylakoid membrane.
What does CO2 react with in carbon fixation ?
CO2 + RuBP and Rubisco enzymes to form an unstable intermediate.
What happens to unstable intermediate in calvin cycle ?
Splits apart into GP (glycerate 3-phosphate).
What happens to each GP molecule ?
Converted to TP (triose phosphate) using hydrogen atom from NADPH and energy from ATP.
How is TP recycled ?
5/6 are used to regenerate RuBP and 1 is used to make glucose, lipids or carbohydrates
Limiting factors of photosynthesis ?
Light intensity, CO2 concentration and temperature.
