Photosynthesis Lecture

​Photosynthesis

​How do plants harness light energy to manufacture food?

Plant Anatomy

Flower: Attracts pollinators
to help with pollination.
Leaves: Absorb sunlight to
produce glucose(sugar) for food.
Stem: Holds the leaves up and
transports materials.
Roots: Plant support, absorbs
water and minerals.

Match

Match the following

• Stem

• Leaves

• Root

• Flower

• Photosynthesis

Holds up plant, transports materials

Where sunlight is absorbed

Absorbs water/minerals, anchors plant

Attracts pollinators, pollination site

Plants creating food from light

• Holds up plant, transports materials

• Where sunlight is absorbed

• Absorbs water/minerals, anchors plant

• Attracts pollinators, pollination site

• Plants creating food from light

​External Structure

​One structural difference among plants is the manner by which their leaves are arranged on the stem. You can classify them according to phyllotaxy or leaf arrangement.

​Blade: The broad, flat part. Provides a large area to capture sunlight.
Petiole: The stem part. Supports the blade and
turns it towards the sun.

​Photosynthesis

​Leaves allow a plant to produce food using a chemical reaction called photosynthesis.

​Photosynthesis

Plants take in:
Water + Carbon Dioxide + Sunlight
To produce:
Glucose (sugar) + Oxygen

Labelling

Label the inputs (what goes in) and outputs (what comes out) of photosynthesis.

Drag labels to their correct position on the image

Sunlight

Carbon Dioxide

Water

Oxygen

Glucose (sugar)

​Internal Structure

​A leaf has three major parts:
1. Epidermis: Upper and lower surface layers of cells (derm means skin)
2. Vein: Made of vascular tissues
3. Mesophyll: The middle layer of cells
-Think "M" for "Middle"

​Epidermis

-Is a protective layer of cells covering the entire surface of the leaf.

-Coated with water proof material called cutin.

-Contains pores called stomata.

​Stomata

​The stomata (singlular: stoma) are
for the exchange of gas and the loss of water in the form of vapor through a process called transpiration.

​Stoma

​The opening where plants exchange gases.

​Stomata

Leaves have tiny holes on the bottom. Stomata allow gases to enter and exit the leaf.

​Stomata

Carbon Dioxide (CO2) enters.
Oxygen (O2) and Water vapor (H20) exits.

Multiple Choice

What enters the leaf through the stomata?

• Carbon Dioxide

• Water Vapor and Oxygen

• Glucose

• Sunlight

Multiple Choice

What exits the leaf through the stomata?

• Carbon Dioxide

• Water Vapor and Oxygen

• Glucose

• Sunlight

​Stomata

Stomata can be opened or closed.

Stomata are surrounded by sausage-shaped guard cells that control its opening/closing.

When guard cells swell with water, the stomata opens.
When the guard cells lose water, the stomata closes.

Think of guard cells as guarding
something precious: water! Plants do
not want to lose too much water through transpiration, so they control when the stomata open.

Multiple Choice

What opens and closes the stomata?

• Hinge Cells

• Sausage Cells

• Guard Cells

• Soldier Cells

Leaf Vein

​The vein of a leaf is made of
vascular tissues.
1. Upper Xylem: for transport of water
2. Lower phloem: for the transport of food in the form of sucrose (sugar
made from glucose).

Xylem and Phloem are tubes that move materials throughout the plant.

Xylem carries water and minerals. It moves water and nutrients up from the roots.

Xylem is a dead tissue when it reaches maturity.

Phloem carries nutrients & sucrose (sugar). It moves sucrose and nutrients through the plant in all directions. Phloem is a living tissue.

How to Remember

​-Phloem and food both have
the "F" sound. (living tissue)
-Xylem is for when the plant is excessively thirsty! (dead tissue)

Match

Match the following

• Phloem carries...

• Xylem carries...

• xylem is made of ______ tissue

• phloem is made of ______ tissue

nutrients and sucrose

water & minerals

dead

living

• nutrients and sucrose

• water & minerals

• dead

• living

Autotrophic Process: Plants
and plant-like organisms make their energy (glucose) from sunlight.
It is stored as carbohydrates in their bodies.

Why is photosynthesis important?

​-Makes organic molecules (glucose) out of inorganic materials (carbon dioxide and water)
-It begins all food chains/webs. Thus all life is supported by this process.
-It also makes oxygen gas! (We need it to breathe)

-Plants use photosynthesis to turn
water and carbon dioxide into glucose,
which is a type of sugar.
-Plants use glucose as food for energy and as a building block for growing.
-Autotrophs make glucose and heterotrophs are consumers of it.

Carbon dioxide + water + sunlight >>>> glucose + oxygen

Photosynthesis occurs largely
in the mesophyll.
The mesophyll may form a distinct upper palisade and lower spongy regions.

Chlorophyll pigments are in
structures called chloroplasts.
This is where plants capture light energy!

A single disk in the chloroplast
is called a thylakoid.

Disks called grana (singular: granum) contain the pigment chlorophyll.

The liquid portion of a
chloroplast is the stroma.

Chloroplasts are found in cells
of leaves. Cells containing chloroplasts are in the palisade layer.

The bottom, spongy layer is
where gas exchange happens.
Stomata are on the bottom layer.

Chloroplasts make the oxygen
too!

Leaves are green because they
contain the pigment chlorophyll.
Leaves have a large surface area to absorb as much light as possible.