GB Week 2

Chromatography

separation technique used to identify various components of mixtures based on the differences in their structure and/or composition.

Pigments

are substances that absorb visible light. Different pigments absorb light of different wavelengths

Photoexcitation

is the production of an excited state of a quantum system by photon absorption

Chloroplasts

are found only in plants and photosynthetic algae. (Humans and other animals do not have chloroplasts.) The chloroplast's job is to carry out a process called photosynthesis.

STRUCTURAL COMPONENTS OF CHLOROPLAST

Chloroplast

disc-shaped organelles found in the cytosol of a cell. They have outer and inner membranes with an intermembrane space between them

Chloroplast

If you passed through the two layers of membrane and reached the space in the center, you’d find that it contained membrane discs known as thylakoids, arranged in interconnected stacks called grana (singular, granum).

membrane of a thylakoid disc

contains light-harvesting complexes that include chlorophyll

thylakoid space or lumen

the space inside a disc

stroma

the fluid surrounding the thylakoids

Light

Light, as it encounters an object, is either reflected, transmitted, or absorbed.

Visible Light Wavelength (380-750nm)

the segment in the entire range of electromagnetic spectrum that is most important to life on earth. It is detected as various colors by the human eye

Pigments

are the means by which plants capture sun’s energy to be used in photosynthesis.

4 main categories of Plant Pigments

chlorophylls, anthocyanins, carotenoids, and betalains.

Anthocyanins

particularly found in fruits such as grapes, purple grapes, black berries, strawberries, and raspberries.

Carotenoids

are Plant pigments that are responsible for their yellow, bright red, and orange color are carotenoids that play a key role in plant health. Different vegetables and fruits in which carotenoids are present: yams, carrots, sweet potatoes, watermelon, papaya, cantaloupe, spinach, mangos, kale, tomatoes, oranges, bell peppers,

Xanthophyll

molecules known as hydrocarbons and found in orange and yellow fruits and vegetables, for example, pumpkin, cantaloupe, sweet potatoes, apricots and carrots.

CHLOROPHYLL

the greenish pigment found in the thylakoid membrane inside the chloroplast of a plant cell.

CHLOROPHYLL

absorbs blue and red light while it transmits and reflects green light. This is why leaves appear green.

CHLOROPHYLL

It directly participates in converting solar energy to chemical energy.

Head and Tail

Structure of chlorophyll

Head

a flat hydrophilic head called porphyrin ring. It has a magnesium atom at its center. Different chlorophylls differ on the side groups attached to the porphyrin.

Tail

a lipid-soluble hydrocarbon tail.

HOW DOES PHOTOEXCITATION OF CHLOROPHYLL HAPPEN?

PHOTOSYSTEM

is an aggregate of pigments and proteins in the thylakoid membrane responsible for the absorption of photons and the transfer of energy and electrons.

LIGHT-HARVESTING COMPLEX

is also called the ‘antenna’ complex and is consisted of several different pigments (chlorophyll a, chlorophyll b, and carotenoids) bounded with proteins

LIGHT-HARVESTING COMPLEX

When a pigment molecule absorbs a photon, energy is passed on from one pigment molecule to another pigment molecule until the energy reaches the reaction center.

REACTION-CENTER COMPLEX

is composed of a pair of chlorophyll a and a primary electron acceptor.

THERE ARE TWO TYPES OF PHOTOSYSTEM:

PHOTOSYSTEM II & PHOTOSYSTEM I

PHOTOSYSTEM II

was discovered later after the discovery of Photosystem I, but functions first in the light reaction of photosynthesis.

PHOTOSYSTEM II

The chlorophyll a in the reaction-center of Photosystem II effectively absorbs light with a wavelength of 680nm and thus called P680.

PHOTOSYSTEM I

was discovered first

PHOTOSYSTEM I

Its reaction-center has a chlorophyll a called P700 because it is effective in absorbing light with a wavelength of 700nm.