Photosynthesis: Key Concepts and Structures in Plant Biology

life depends on

sugar produced by the ability of photosynthetic organisms to harvest energy of the sun -> covering it to glucose

what is photosynthesis

process of converting carbon dioxide water and the energy of sunlight into chemical energy stored in the bonds of glucose and oxygen

chemical formula of photosynthesis

6CO2 + 6H2O + light energy------> C6H12O6 + 6O2

photosynthesis occurs in

plants, algae and certain types of bacteria takes place in the chloroplasts of plants

leaves and chloroplasts are specifically adapted for it

why are leaves and chloroplasts are specifically adapted for photosynthesis

typically only a few cells thick -> both upper and lower surfaces fo leaves have a layer of transparent epidermis cells covered by a wax which is hydrophobic reducing evaporation of water from the leaf

stoma in leafs

adjustable pores in the epidermis that allows in or admits co2

when do you think pores are opened/closed

stoma(pores) open close in response to environmental conditions and plants needs and they open to allow carbon dioxide to enter for photosynthesis and close to preserve water

mesophyll cells

few layers of cells inside lead which contains majority of leafs chloroplasts

-> also where photosynthesis occurs

vascular bundles

(veins) supply water and nutrients to mesophyll cells and carry sugar produced by photosynthesis to other parts of the plant

stoma

semi fluid medium where sugar is produced

thykaloids

disk shaped interconnected membrane sacs

grana

thykaloids stacked atop each other

Photosynthesis consists

of light d and I reactions

light dependent

occurs in thylkaloid membranes, captures sunlight energy and converts some of it into transport molecules like ATP and NADPH

light independent

occurs in the storm and use chemical energy of carrier molecules to produce glucose and other organic molecules

light functions

light emits energy into electromagnetic spectrum, s/l wavelengths and h/l energy

photons

individual packets of energy light is composed of

photons correspond:

photon energy corresponds to wavelength

when light hits a leaf, 3 things happen:

1. light and energy is absorbed (can drive biological processes)

2. light and energy is reflected (gives an object color

3. light and energy is transmitted(gives an obj color)

chloroplast captures light in the

thykaloid membrane, absorbs violet, blue/red light, but reflects green

accessory pigments contained in thykaloids

capturing light energy and transferring it to chlorophyll

carotenoids

Accessory pigments that broaden the spectrum of colors that can drive photosynthesis. absorbs blue/green light

phycocyanin

accessory pigment , absorbs green/yellow reflects blue

photosystems

a light harvesting complex and it's associated electron transport system found in thykaloid membrane

-light dependent reactions occur in clusters of molecules

each thylakoid contains thousands of copies of 2 kinds of photosystems

1. PSI

2. PSII

each system consists of 2 major parts

1. light harvesting complex

2. electron transport system

light harvesting complex

these complexes absorb light and pass energy to a specific chlorophyll molecule reactant center

contains about 300 chlorophyll and accessory pigment molecules

reactant center chlorophyll

located next to electron transport system

electron transport system

a series of electron carrier molecule embedded in thykaloid membrane

Clarifying the "2 photons" idea

Each photosystem absorbs photons independently.

PSII absorbs photons to excite electrons for ATP production.

PSI absorbs photons to excite electrons again for NADPH production.

So light energy is used twice to fully energize the electrons.

Step-by-Step Connection

. Light-harvesting complex absorbs energy

Chlorophyll molecules in the light-harvesting (antenna) complex absorb photons.

This energy is passed from chlorophyll to chlorophyll (energy transfer, not electrons).

The energy eventually reaches the reaction center chlorophyll.