Photosynthesis Overview

Photosynthesis Cell Respiration Oxygen and

Glucose

CO2 and

Water

Location: Chloroplast

Only in plants Location: Mitochondria

Plants and animals

Plant Anatomy

• Roots

– Anchor plant to the ground

– Absorb water and minerals from soil (by osmosis)

– Store food for plant (glucose made in photosynthesis is stored as starch)

• Stems – Transport water and minerals from the roots up

to the leaves (xylem)

– Transport food (glucose) made in the leaves down to roots for storage (phloem)

• Leaves – Photosynthesis, accomplished by the

cooperation of many different cell types.

Upper epidermis

Chloroplast

Spongy

mesophyll cell

Guard

cell Stoma

Phloem cells (glucose down)

(opening)

Photosynthesis = Process of converting sun energy into glucose energy

Chlorophyll 6 CO2 + 6 H2O + E ---------------> C6H12O6 + 6 O2 (light)

Reactants Products

Gas

diffuses

into leaf

through

stomata

Travels

from

roots to

leaves

via xylem

E captured

by chlorophyll

(inside

chloroplast)

Life’s

primary

food

molecule

Gas

diffuses

out into

air (by-

product)

Factors Affecting Photosynthesis

• Temperature (68° to 95° F)

• Amount of sunlight

• Amount of water

• Amount of CO2

• Room to grow, time, nutrients

Chloroplast

• Plastid that contains chlorophyll and undergoes photosynthesis

Chloroplast

Grana

Thylakoid

Palisade Cells

Leaf Organ

Chloroplast

Stroma

Thylakoid

membrane

contains

chlorophyll

Phospholipid

bilayer

One Chloroplast

Information about Light: The Visible Spectrum

Red Orange Yellow Green Blue Indigo Violet

Low

Energ

y H

igh E

nerg

y

Why are leaves green?

Why is the sky blue?

• Green is green because it reflects green light and absorbs the energy of all other colors

• Absorbed light – stored energy in carbohydrates produced by photosynthesis

• Reflected light – color you see

(doesn’t give plant energy)

Chloroplast

Light

Reflected

light

Absorbed

light

Transmitted

light

Granum

Pigment Molecule that absorbs light energy from the sun; give leaves their color

Chlorophyll a

Chlorophyll b

Carotenoids

Wavelength of light (nm)

Absorption spectra

Ab

so

rpti

on

of

lig

ht

by

ch

loro

pla

st

pig

men

ts

400 500 600 700

• In plants, chlorophyll a and b are the main pigments.

• Found in chloroplasts

• Pigments absorbs energy from visible light spectrum, mostly violet/blue & orange/ red light (reflects green)

LE 10-8a

White

light

Refracting

prism

Chlorophyll

solution

Photoelectric

tube

Galvanometer

The high transmittance

(low absorption)

reading indicates that

chlorophyll absorbs

very little green light.

Green

light

Slit moves to

pass light

of selected

wavelength

0 100

LE 10-8b

White

light

Refracting

prism

Chlorophyll

solution

Photoelectric

tube

The low transmittance

(high absorption)

reading indicates that

chlorophyll absorbs

most blue light.

Blue

light

Slit moves to

pass light

of selected

wavelength

0 100

CH3

CHO

in chlorophyll a

in chlorophyll b

Porphyrin ring:

light-absorbing

“head” of

molecule; note

magnesium atom

at center

Hydrocarbon tail:

interacts with

hydrophobic

regions of proteins inside

thylakoid membranes of

chloroplasts; H atoms not

shown

Accessory Pigments

• Absorb light that chlorophyll can’t

• Allow plants to use more energy from light than could be trapped by chlorophyll alone

Examples: Carotenoids (appears orange, yellow, red

because it reflects these colors)

Xanthophyll I and II (appears yellow because it reflects this colors)

**Remember** More light absorbed = more energy for photosynthesis

Chlorophyll a

Chlorophyll b

Carotenoids

Wavelength of light (nm)

Absorption spectra

Ab

so

rpti

on

of

lig

ht

by

ch

loro

pla

st

pig

men

ts

400 500 600 700