Introduction to Cell Biology and Genetics - Ch. 8

Photosynthesis

Transforms the energy of sunlight into chemical energy stored in organic molecules.

Organisms acquire organic compounds by one of two major nutritional modes:
Heterotrophic
Autotrophic

This is an example of Autotrophic.

Summarized w/ the following equation:

6 CO₂ + 12 H₂O + Light Energy —> C₆H₁₂O₆ + 6 O₂ + 6 H₂O

Autotrophs

“Self-feeders”; they make organic molecules entirely from non-living materials.


They are the producers of the biosphere; the ultimate source of organic compounds for all non-________ organisms.

Photosynthesis also occurs in algae and some protists and prokaryotes.

Heterotrophs

“Other feeders”; they live on compounds produced by other organisms.

Some are decomposers; they consume the remains or wastes of other organisms.

Chloroplasts

The location of Photosynthesis.

Structurally like and likely evolved from photosynthetic bacteria.

Mesophyll

The interior tissues of the leaf.

Leaves are the major sites of photosynthesis.

Water travels to the leaves and sugar is exported out through veins.

Stroma

Chloroplasts have a double membrane surrounding a dense fluid called the ______.

NOT to be confused with the Stromata, which are microscopic pores where CO₂ and O₂ enter and leave the cell respectively.

Thylakoids

Composed of sacs and suspended within the stroma.

Some form stacks called grana.

Make up the “coin stacks” of Chloroplasts.

Chlorophyll

A pigment that resides in the Thylakoid membranes; gives leaves their green color.

Absorbs the light energy that drives the synthesis of organic molecules.

Light Reaction

First stage of Photosynthesis.

Converts solar energy into chemical energy.

H₂O is split to provide electrons and protons (H⁺)

O₂ is released as a by-product.

The electron receptor NADP^₊ is reduced to NADPH.

ATP is generated by adding a phosphate group to ADP in a process called photophosphorylation.

The Calvin Cycle

Second stage of Photosynthesis.

Produces sugar from CO₂ using NADPH and ATP produced during the light reactions.

CO₂ is incorporated into organic molecules during carbon fixation and then reduced to form sugars.

ATP and NADPH provide chemical energy to power the _____ cycle.

Chlorophyll-a

The primary photosynthetic pigment.

The absorption spectrum suggests that violet-blue and red light work best for photosynthesis.

Appears olive green.

Chlorophyll-b

An accessory pigment.

An accessory pigment broadens the spectrum used for photosynthesis.

Appears blue green under visible light.

Carotenoids

Another type of accessory pigment.

Various shades of yellow and orange.

May broaden the spectrum used for photosynthesis.

Photoprotection is their main function.

They absorb excessive light that would be harmful to Chlorophyll-a and the cell.