Sunlight is a form of energy used in photosynthesis, consisting of a mixture of different colors of the visible light. The light-absorbing pigment in leaves is found within the thylakoids whose structure is saclike. Stacks of thylakoids form grana and the fluid that surrounds these thylakoids is called the stroma.
The outer membrane of chloroplast is semi-permeable, allowing small ions to pass through diffusion while restricting movement of large proteins. The inner membrane synthesizes lipids and carotenoids.
The green pigment that is found in the thylakoids and which aids in the absorption of light energy is chlorophyll. Accessory pigments can absorb light energy at different wavelengths, and then pass the energy to chlorophyll. An example of accessory pigment is the carotenoid which is either yellow or orange, which helps broaden the spectrum range of chlorophyll maximizing the process of photosynthesis.
Adaptation: A large surface area for photosynthetic pigments, electron carriers, and ATP synthase enzymes which synthesize ATP, and photosynthetic pigment arranged in photosystems that allow maximum absorption of light energy.
Photosynthesis takes place in two stages; the light stage and the dark stage. The light reactions require light to occur and begin by absorbing light in the chloroplast. Energy obtained from sunlight is used to break water molecules into hydrogen and oxygen which are to be used in the next stage. The dark reactions do not require sunlight but rely on energy stored from the light reactions.
Revision
Terms in this set (7)
Original
What does a chloroplast consist of?
Grana (stacks of thylakoid membrane) (granum singular)
joined by lamella
Contained in thick fluid stroma
Describe the function of a chloroplast?
Chlorophyll in chloroplasts absorbs light energy from the sun for use in photosynthesis to convert carbon dioxide and water into glucose (carbohydrate) and oxygen
How would you calculate the maximum length of a chloroplast as seen by an electron microscope with a magnification of x 30 000?
Actual = image/magnification
Actual = (image in mm x 1000)/ 30 000
= 1.8 micrometres
Name the process in which cells become adapted for different functions?
Specialisation
What surrounds a palisade cell?
Cellulose cell wall
The real length of a cell is 20 micrometers. By how many times has it been magnified?
Measure in mm
Multiply by 1000
Divide this image value (mm x 1000)
by 20 micrometres
Explain one way in which the palisade cell is adapted for photosynthesis?
Many chloroplasts containing chlorophyll to trap light for use in converting carbon dioxide and water into glucose and oxygen.
(large vacuole which pushes chloroplasts to the edge creating a short diffusion distance)
(Thin/permeable cell wall for absorption of CO₂)
Double membrane function
Controls movement in and out of the chloroplasts.
Thylakoids function
They are folds of the inner membrane, which form a system of branching membrane. This provides a large surface area for absorption.
Grana function
Piles of flat, compact circular thylakoid membranes containing chlorophyll.
Chlorophyll function
Photosynthetic pigments that absorb light energy.
Stroma fucntion
Watery matrix in which membranes are suspended.
Starch grains/liquid droplets/ribosomes function
Suspended in stroma (energy storage and protein synthesis).
Thylakoid Membrane Adaptation
They provide a large surface area for the attachment of chlorophyll, electron carriers and enzymes that carry out the light dependent reaction.
Grana Adaptation
A network of proteins in the grana hold the chlorophyll in a very precise manner that allows maximum absorption of light.
Granal Membrane Adaptation
They have enzymes attached to them, which help manufacture ATP.
Chloroplast Adaptation
They contain DNA and ribosomes so they can quickly and easily synthesise some of the proteins required for the Light Dependent Reaction.
