M5C17 - Photosynthesis Flashcards
What is ATP and how does it release energy?
Adenosine Triphosphate
Universal energy currency in cells.
When a phsphate is removed from ATP it becomes ADP and energy is released.
What is phosphorylation?
Synthesising ATP from ADP by adding a phosphate group which requires energy
What is chemiosmosis?
Method of forming ATP:
Synthesising ATP that involves the diffusion of protons through a partially permeable membrane. As they diffuse down their concentration gradient energy is used to form ATP from ADP + phosphate.
The channel protein the protons diffuse through is attached to ATP synthase. The energy released as the protons move through allows ATP synthase to catalyse the formation of ATP.
What is an electron transport chain?
Method of forming ATP:
-In order for the protons to diffuse there has to be a concentration gradient.
-In both photosynthesis and respiration, the energy for this comes from the electron transport chain which relies on energy from excited electrons.
-The electron transport chain has a series of electron carriers with progressively lower energy levels.
-As the excited electron moves from one carrier to the next energy is released.
-This energy is used to pump protons across the membrane to produce a concentration gradient.
How are electrons excited in photosynthesis and respiration?
-In photosynthesis electrons in pigment molecules are excited by absorbing light from the sun.
-In respiration excited electrons are released when chemical bonds are broken in respiratory substrate molecules (e.g. Glucose).
What is a heterotroph?
Organisms that gain complex organic molecules by eating each other
What is an autotroph?
Organisms that can photosynthesise
What is the function of the double membrane in a chloroplast?
controls molecular traffic into and out of the chloroplast.
What are thylakoids?
Flat sacs formed by the inner membrane
What are grana?
Stacks of thylakoid membranes which contain photosynthetic pigments such as chlorophyll arranged as photosystems.
Describe 2 ways in which the grana are adapted to their function:
-Stacked and flat membranes provide a large surface area for light absorption.
-Contains photosystems.
What is the stroma?
The fluid surrounding the grana and contains all the enzymes required for the light independent stage of photosynthesis.
What are lamellae?
Membranous channels that join the grana
What is a photosynthetic pigment?
Pigment molecules absorb specific wavelengths of light and refelct others. Different pigments absorb and reflect different wavelengths which is why they have different colours.
What is chlorophyll?
The primary pigment in photosynthesis.
Absorbs mainly red and blue light and reflects green light.
What are some other photosynthetic pigments?
chlorophyll b, xanthophylls, carotenoids absorb different wavelengths to chlorophyll a.
What is a light harvesting system?
Formed by photosynthetic systems and other proteins.
The role of the system is to absorb or harvest light energy of different wavelengths and transfer this energy to the reaction centre.
Chlorophyll a is located in the reaction centre, where reactions involved in photosynthesis take place.
What is a photosystem?
The light harvesting system combined with the reaction centre.
Describe the use of chromatography to investigate photosynthetic systems:
Chromatography can be used to separate the different pigments in a plant extract.
The mobile phase would be the solution containing a mixture of pigments.
The stationary phase would be a thin layer of silica gel applied to glass.
Different solubilities of the pigments as well as different interactions with the stationary phase lead to them moving at different rates, this results in the pigments being separated as they move through the gel.
What is photorespiration?
A wasteful pathway that competes with the Calvin cycle that occurs when the stomata close to prevent water loss and so carbon dioxide can’t get in. Oxygen combines with rubisco instead of carbon dioxide.
What molecules is the source of electrons in photosynthesis?
H2O
Which region of the chloroplast does photolysis occur?
Thylakoid membrane
What are the correct products of the light dependent reaction that are needed for the light reaction?
Reduced NADP, ATP
Define the term light compensation point:
The light intensity at which the rate of photosynthesis is equal to the rate of respiration.
