Part 1 Flashcards
Photosynthesis (+ equation)
Uses light energy to convert carbon dioxide into glucose.
6CO2 + 6H20 → C6H12O6 + 6O
Function of Photosynthesis
Supplies all usable chemical energy for life on Earth
Almost all organisms rely on photosynthesis for carbon – the building block for all organic compounds
Supplies required oxygen and chemical energy as glucose
uses CO2 – from air, enters plants via leaf
uses H20 – from soil, enters plants via roots
Glucose’s Jobs/ Uses
Energy Source: plants break down glucose in cellular respiration-> make ATP
Used to build structures: ie. Plant cell wall needs cellulose (a starch – long chains of glucose)
ATP
The carrier of energy from glucose
When a cell needs energy, it can release it by breaking the bond between the second and third phosphate groups in ATP.
Chlorophyll and Chloroplasts
Light energy from the sun must be captured for photosynthesis to occur.
Sunlight is “white” light—actually a mixture of different wavelengths.
Photosynthetic organisms capture energy from sunlight with pigments—principally with chlorophyll.
*pigments give things color!
Pigments
In addition to water, carbon dioxide, and light energy, photosynthesis requires Pigments
Chlorophyll is the primary light-absorbing pigment in autotrophs
Chlorophyll is found inside chloroplasts
Light
visible light – looks white
It contains all colors – also called wavelengths ROYGBIV
Light energy/wavelengths from the sun will power photosynthesis
*except Green light – not absorbed-> reflected
(this is why plants look green)
Photosynthesis occurs in a Chloroplast:
Membrane bound organelle (with its own DNA)
Green color – from Chlorophyll – a pigment (that reflects green light)
Plants contain two types of Chlorophyll:
Chlorophyll a – absorbs blue/violet light, and some red light
Chlorophyll b – absorbs blue and orange light
Light Reaction
First Step in Photosynthesis
Sunlight –> a form of electromagnetic radiation, moves in waves,
Electromagnetic waves
– very long (low energy) to very short (high energy)
Length of wave determines color and energy:
Longer wavelength – lower energy
Light and Pigments
Energy From The Sun Enters Earth’s Biosphere As Photons
Photon = Light Energy Unit
Light Contains A Mixture Of Wavelengths
Different Wavelengths Have Different Colors
Different pigments absorb different wavelengths of light
Photons of light “excite” electrons in the plant’s pigments
Excited electrons carry the absorbed energy
Excited electrons move to HIGHER energy levels
Structure of the Chloroplast
Double membrane organelle
Outer membrane smooth
Inner membrane forms stacks of connected sacs called thylakoids
Thylakoid stack is called the granum (grana-plural)
Gel-like material around grana called stroma
Function of the Stroma
Light-Independent reactions occur here (also called the Calvin Cycle) - the stroma is the site for the second step of photosynthesis
