Introduction to Photosynthesis
Heterotrophs

Heterotrophs: Organisms that can not make
their own food

Obtain food by eating other living things
2
Autotrophs

Autotrophs: Organisms that can make their
own food
Photosynthesis


Process by which plants use energy from sunlight to
produce their food
Carbon dioxide + water

6CO2 + 6H2O
sunlight
sunlight
Glucose + oxygen
C6H12O6 + 6O2
Location of Photosynthesis

Photosynthesis occurs in the chloroplasts

Absorbs light in photosynthesis
Chloroplast
Strom
Outer Membranea
Inner Membrane
Thylakoid

Has a double membrane (inner and outer membranes)

System of flattened sacs called thylakoids


Stack of thylakoids
granum (plural grana)
Stroma: Gel like material around the grana
Granum
Sunlight

Sunlight appears as white light, but it is
actually a mixture of different wavelengths.

See wavelengths as different colors (red-violet)
Pigments

Plants gather the sun’s energy with lightabsorbing molecules called pigments.

Located in thylakoid membranes

Different pigments absorb different wavelengths
of light.

Chlorophyll is the primary light absorbing
pigment.
Chlorophyll

2 main types of chlorophyll- chlorophyll a and chlorophyll b

Absorbs light in the blue-violet and red regions, but not
in the green region.

Leaves reflect green light, which is why plants look
green.
Carotenoids

Red, orange, and yellow pigments called carotenoids are also found
in the thylakoids.


Act as accessory pigments: absorb additional wavelengths of
light energy that is transferred to chlorophyll a
In the fall, as the amount of chlorophyll declines, accessory
pigments become more visible.
Interaction Reflection pg.28

Explain why it is beneficial for plants to
contain more than 1 type of pigment.
Paper Chromatography

Chromatography: “color writing” a process that separates
a mixture into its individual components


The pigments in a leaf can be separated
Uses a solvent to carry and separate the pigments

Capillary action (movement upward against gravity)
allows the solvent and pigments to move up the filter
paper

The pigments are separated at different rates
depending on :1) solubility in the solvent and 2)
attraction to the filter paper
Solvent
Paper Chromatography- Ink Separation
Spinach Lab
1.
Cut filter paper with a point at the end. Draw faint pencil line. Attach paper clip
to cork (ALREADY DONE FOR YOU), and strip of paper to paper clip (see set
up diagram).
2.
Tear spinach leaves into small pieces. Place in mortar with a little sand, and 5ml
of ethyl alcohol (ETHANOL). Grind with pestle.
3.
Use glass rod to transfer drops of pigment extract to center of pencil line. Let dry.
Repeat about 20 times.
4.
Pour 5ml of chromatography solvent into test tube (ALREADY DONE FOR
YOU). The tip of filter paper should just touch the surface of the solvent. Once
solvent reaches the top, take paper out to dry for about a minute. PLACE CORK
BACK INTO TEST TUBE AFTER TAKING OUT FILTER PAPER TO
DRY!!
5.
Observe bands of pigments. DRAW YOUR RESULTS (BAND OF COLORS)
ON THE DIGRAM OF THE SET UP. Measure the distance of each band in
centimeters.