6th lesson

BIOLOGY

UNIVERSITY OF FOOD INDUSTRY- HOCHIMINH CITY

1

THE FOOD WEB

• trap radiant energy from sunlight and convert it into the energy of chemical bonds in large molecules, such as carbohydrates,

• estimated 99.9% of life on Earth relies on

photosynthesis for its energy needs

7.1 Photosynthesis and Life

7.2 An Overview of Photosynthesis

Sunlight minus absorbed

wavelengths or colors equals

the apparent color of an

object.

The feathers of male cardinals are

loaded with carotenoid pigments.

These pigments absorb some

wavelengths of light and reflect

others.

Why are plants green?

Transmitted light

WHY ARE PLANTS GREEN?

Plant Cells

have Green

Chloroplasts

The thylakoid

membrane of the

chloroplast is

impregnated with

photosynthetic

pigments (i.e.,

chlorophylls,

carotenoids).

• Chlorophyll: An important molecule in the process of harvesting sunlight,

• light energy is transformed to chemical-bond energy in the form of ATP,

7.2 An Overview of Photosynthesis

• Light-capturing events,

• Light-dependent reactions,

• Light-independent reactions

3 distinct events in the photosynthesis

• Chlorophyll consists of chlorophyll a and chlorophyll b,

• Chlorophyll capture light energy and become excited,

Light-Capturing Events:

• Chloroplasts contain several pigments

Chloroplast Pigments

– Chlorophyll a – Chlorophyll b – Carotenoids

Figure 7.7

Chlorophyll a & b

•Chl a has a methyl

group

•Chl b has a carbonyl

group

Porphyrin ring

delocalized e-

Phytol tail

Light-Dependent Reactions:

Water-splitting

photosystemNADPH-producing

photosystem

ATP

mill

• Two types of photosystems cooperate in the light reactions

• The O2 liberated by photosynthesis is made from the oxygen in water (H+

and e-)

Plants produce O2 gas by splitting H2O

Light-Independent Reactions

C3-C4 and CAM photosynthesis

7.4 Other Aspects of Plant Metabolism

7.5 Interrelationships BetweenAutotrophs and Heterotrophs

Be ready for next lesson!