Photosynthesis Day 1

PHOTOSYNTHESIS

Life’s ultimate reaction

Multiple Choice

When a candle burns, energy is released in the form of

• carbon dioxide and water

• the chemical substance ATP

• light and heat

• electricity and motion

Chemical Energy

In living cells chemical energy is usually
stored and released by the compound
Adenosine Triphosphate (ATP)

Energy is also stored using Adenosine
Diphosphate (ADP). Cells have more
ADP at any given time than ATP

Glucose is another molecule that contains
90x more energy than ATP. Both ATP and
ADP can be generated from it

Chemical Energy

Heterotrophs-Obtain food by
eating other living organisms

Autotrophs-Make their own food
through photosynthesis

Categorize

Options (16)

Grass

Tree

Algae

Sunflower

Moss

Seaweed

Phytoplankton

Cactus

Lion

Human

Dog

Cat

Bird

Fish

Frog

Snake

Organize the following into the appropriate category

Autotrophs

Heterotrophs

Open Ended

One of the earliest clues as to how photosynthesis works came from a simple study of plant growth. When a tiny seed grows into a massive tree, where does all its extra mass come from? More than 300 years ago a Flemish physician named Jan van Helmont decided to find out. He planted a young willow tree, with a mass of just 2 kilograms, in a pot with 90 kilograms of dry soil. He watered the plant as needed and allowed it to grow in bright sunlight. Five years later, he carefully removed the tree from the pot and weighed it. It had a mass of 77 kilograms.

Where did the extra 75 kilograms come from?

Why should we care about
photosynthesis?

Photosynthesis

The definition: A process in which light energy, water and

carbon dioxide are used to create glucose for energy.

Photo= light
Synthesis= to make

All of life stems from this reaction!

Photosynthesis

The Chemical Equation

6 CO2 6 H2O C6H12O6 6 O2

light energy

Carbon dioxide + Water

Name: ______________________________________ Date: _____________________ #______

glucose+ oxygen

Photosynthesis

◼ Photosynthesis takes place in the

chloroplasts. Only the cells of the
leaf have chloroplasts.

◼ In eukaryotic cells, the

chloroplasts contain specialized
light-absorbing pigments.

Chloroplast

Pigments

◼ Chlorophyll A (green) is the most

important photosynthetic pigment.

◼ Other pigments, called antenna or

accessory pigments, are also present in

the leaf.

▪ Chlorophyll B (also green)

▪ Carotenoids (orange / red)

▪ Xanthophylls (yellow / brown)

Chlorophyll is the main pigment- it reflects

green.

Pigments- Photosystems

The pigments are embedded in the

membranes of the chloroplast in
groups called photosystems.

PHOTOSYSTEM II

PHOTOSYSTEM I

*Note* Photosystem I was discovered
before Photosystem II, which explains why the order is switched.

Chlorophyll

400

500

600

700

Chlorophyll absorbs most of the energy
for the plant.

There are two categories of chlorophyll:
chlorophyll a and chlorophyll b.

Recall the electromagnetic spectrum.
The wavelength of visible light ranges
from 400 nm to ~750 nm.

Hotspot

Looking at the line for CHLOROPHYLL A, select the two highest absorbance peaks.

Open Ended

What are the approximate wavelengths for both of these peaks from chlorophyll a and what color is associated with both of them?

Hotspot

Looking at the line for CHLOROPHYLL B, select the two highest absorbance peaks.

Open Ended

What are the approximate wavelengths for both of these peaks from chlorophyll b and what color is associated with both of them?

Draw

Circle the area where the least absorbance occurs for chlorophyll a.

Draw

Circle the area where the least absorbance occurs for chlorophyll b.

Chlorophyll

400

500

600

700

​Green light is the least absorbed color of light so it is reflected back to us.

This is why leaves appear green.