Photosynthesis

Chapter 8

THE SUN: MAIN SOURCE OF ENERGY FOR LIFE ON EARTH

Food Chain

THE FOOD WEB

Almost all plants are photosynthetic autotrophs, as are some bacteria and protists

Autotrophs generate their own food or organic matter through photosynthesis

Sunlight energy is transformed to energy stored in the form of chemical bonds

(a) Mosses, ferns, andflowering plants

(b) Kelp

(c) Euglena (d) Cyanobacteria

THE BASICS OF PHOTOSYNTHESIS

Heterotrophs

Organisms that are not able to make their own food and have to eat other organs to obtain energy.

Ex. Toad, fish

Autotrophs or heterotrophs?

Humans Blue-green algae Paramecium Euglena Yeast Pine tree Moss Mushroom crocodile

Light Energy Harvested by Plants & Other Photosynthetic Autotrophs

6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2

Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water

AN OVERVIEW OF PHOTOSYNTHESIS

Carbondioxide

Water Glucose OxygengasPHOTOSYNTHESIS

What is photosynthesis in general terms?

The conversion of CO2 and water into glucose.

The glucose is used as an energy source for plants.

The “carbon skeletons” of glucose can also be modified and made into other molecules by the plant.

What is the formula for photosynthesis?

6 carbon dioxide + 6 water glucose + 6 oxygen gas

Usually you see the words over and under the arrow indicate necessary components that are not changed or used up by the reaction.

Different wavelengths of visible light are seen by the human eye as different colors.

WHYWHY ARE ARE PLA PLANTS NTS GREGREEN?EN?

Gammarays

X-rays UV Infrared Micro-waves

Radiowaves

Visible light

Wavelength (nm)

WHWHY ARY ARE PE PLANLANTS GTS GREREEN?EN?

It's not that easy bein' green Having to spend each day the color of the leaves When I think it could be nicer being red or yellow or gold Or something much more colorful like that…

Kermit the Frog

Electromagnetic Spectrum and Visible Light

Gammarays X-rays UV

Infrared & Microwaves Radio waves

Visible light

Wavelength (nm)

Sunlight minus absorbed Sunlight minus absorbed wavelengths or colors wavelengths or colors equals the apparent color equals the apparent color of an object.of an object.

The feathers of male cardinals are loaded with carotenoid pigments. These pigments absorb some wavelengths of light and reflect others.

Reflected light

Why are plants green?

Reflected lig

ht

Transmitted light

Where in a cell is photosynthesis performed?

chloroplasts in eukaryotes cytoplasm of prokaryotes

WHYWHY ARE ARE PLA PLANTS NTS GREGREEN? EN?

Plant Cells have Green Chloroplasts

photosynthetic pigments (i.e., chlorophylls, carotenoids).

Chloroplasts absorb light energy and convert it to chemical energy

LightReflected

light

Absorbedlight

Transmittedlight

Chloroplast

THE COLOR OF LIGHT SEEN IS THE COLOR NOT ABSORBED

In most plants, photosynthesis occurs primarily in the leaves, in the chloroplasts

A chloroplast contains: stroma, a fluid grana, stacks of thylakoids

The thylakoids contain chlorophyll Chlorophyll is the green pigment that captures light

for photosynthesis

Photosynthesis occurs in chloroplasts

The location and structure of chloroplasts

LEAF CROSS SECTION MESOPHYLL CELL

LEAF

Chloroplast

Mesophyll

CHLOROPLAST Intermembrane space

Outermembrane

Innermembrane

ThylakoidcompartmentThylakoidStroma

Granum

StromaGrana

When is photosynthesis performed?

Whenever the organism is exposed to light.

How many stages are there in photosynthesis? What are their names?

Two Stages: Light Dependent Reactions Light Independent Reactions AKA the Light and Dark Reactions

The Calvin cycle makes sugar from carbon dioxide ATP generated by the light

reactions provides the energy for sugar synthesis

The NADPH produced by the light reactions provides the electrons for the reduction of carbon dioxide to glucose

LightChloroplast

Lightreactions

Calvincycle

NADP

ADP+ P

The light reactions convert solar energy to chemical energy Produce ATP & NADPH

AN OVERVIEW OF PHOTOSYNTHESIS

The O2 liberated by photosynthesis is made from the oxygen in water (H+ and e-)

Plants produce OPlants produce O22 gas by splitting H gas by splitting H22OO

Light Dependent Reactions

Take in water and produce Oxygen and lots of electrons in the form of NADPH and energy in ATP

Occurs in the Thylakoid membrane of the chloroplast

Light Independent Reactions

AKA Dark reactions or Calvin cycle Takes in Carbon Dioxide and ATP and

electrons in the Form of NADPH Makes Glucose Occurs in the stroma the fluid like portion of

the chloroplast.

Review: Photosynthesis uses light energy to make food molecules

Light

Chloroplast

Photosystem IIElectron transport

chains Photosystem I

CALVIN CYCLE Stroma

Electrons

LIGHT REACTIONS CALVIN CYCLE

Cellular respiration

Cellulose

Starch

Other organic compounds

A summary of the chemical processes of photosynthesis

How do the reactants of photosynthesis get to the chloroplast?

CO2 diffuses into leaf and chloroplast from air.

H2O is carried to the leaf by the xylem. H2O enters plants through the roots. Water enters chloroplast by osmosis.

Light is absorbed by the photosystems found in the chloroplasts in any GREEN part of a plant.

How do the products of photosynthesis leave the chloroplast or leaf and where do

they go? Glucose is moved out of the cell by facilitated

diffusion and is dissolved in the liquid carried in the phloem. The sugar solution is carried to the non-photosynthesizing parts of plants.

O2 exits the leaves by diffusion through open stomata. Some is used by the plant for cellular respiration.

Water in the form of water vapor can diffuse out of leaf through open stomata. (evaporation through stomata = transpiration)

includes

of

occur inoccurs in uses

to produce to produce

uses

Concept Map

Photosynthesis

includes

of

occur inoccurs in uses

to produce to produce

uses

Lightdependentreactions

Thylakoidmembranes Stroma NADPHATPLight

Energy

ATP NADPH O2 Chloroplasts Glucose

Lightindependent

reactions

Concept Map