PHOTOSYNTHESISHonors Biology, Arizona College Prep - Erie

Mrs. GlassmeyerTextbook Reference: 6.1-6.2, The Living World 7th edition

Learning Goals

Unit Learning Goal: You can compare/contrast all components of photosynthesis & cellular respiration in terms of energy, organic and inorganic molecules as well as accurately diagram all the processes as part of the flow of energy and matter through all levels of organization in an ecosystem.

Presentation Learning Goal(s):

1. You can identify organic & inorganic molecules of the process of photosynthesis and write out the equation using proper chemical notation.

2. You can compare the light dependent and light independent reactions of photosynthesis using scientific vocabulary.

3. You can link pigments and the structure of the chloroplast to the process of photosynthesis.

4. You can describe the process of photosynthesis as a part of the biochemical pathway that facilitates the flow of energy and matter through all levels of organization in an ecosystem.

Reflection Time: Learning Goal Scale

4 - You can compare/contrast all components of photosynthesis & cellular respiration in terms of energy, organic and inorganic molecules as well as accurately diagram all the processes as part of the flow of energy and matter through all levels of organization in an ecosystem.

3 - You can compare/contrast some components of photosynthesis & cellular respiration in terms of energy, organic and inorganic molecules as well as diagram most of the processes as part of the flow of energy and matter through all levels of organization in an ecosystem.

2 - You can explain some of the learning goal on your own but may need some help to complete the entire learning goal.

1 - You can answer questions about the learning goal but cannot give specifics using your own words.

Fig. 6.1 Journey into a leaf

Fig. 6.1 Journey into a leaf

What is photosynthesis?

Photosynthesis is the process by which cells harvest light energy and convert it to chemical energy stored in the chemical bonds of sugars (glucose).

• Glucose is a monosaccharide used to power the process of cellular respiration, which produces the Adenosine Triphosphate (ATP) that cells use as their dominant source of energy.

Where does it take place?

Plasma membranes of some bacteria

Cells of algae

Leaves of plants

NOW…

What is the equation for Photosynthesis? Knowing what we know, let’s see if we can figure it out and balance it. BUT…Before we start…A brief Chemical Equation Review…

Review: Chemical Reactions

An example…

A chemical equation has a specific structure. Those molecules considered reactants are on the left side of the equation. Those molecules considered products are on the right side of the equation. An arrow is used to indicate that the reactants react together to form or yield the products.

Were we right?

6CO2 + 6H20 + light energy C6H12O6 + 6O2

Reactants

• 6 molecules of Carbon dioxide

• 6 molecules of Water

• light energy

Products

• 1 molecule Glucose (which is a monosaccharide)

• 6 molecules of Oxygen

What is the structure of the chloroplast?

Thylakoid- structural unit of photosynthesis. Flattened sacs containing photosynthetic pigments

Grana – pancake-like stacks of thylakoids

Stroma – Area between the thylakoids and grana

Thylakoid Stroma

Grana

How does the water and CO2 get into the plant?

• Xylem

• A structure in the stem of a plant that moves water from the roots to

the leaves.

• Stomata

• Openings on the leaf that allow gases to move in and out.

• Surrounded by guard cells that can open and close as necessary.

What are the stages of Photosynthesis?

1. Capturing energy from

sunlight. Produces oxygen.

2. Light energy converted to

chemical energy. Using energy to

make ATP and NADPH

3. Uses chemical energy to form

organic compounds. ATP and

NADPH are used to power the

synthesis of carbohydrates from

CO2

Light-dependent

reactions

Light-independent

reactions

The Calvin cycle

6 CO2

carbon

dioxide

+ 12 H2O

water

+ Light energy C6H12O6

glucose

+ 6 O2

oxygen

+ 6 H2O

water

Where do the stages take place?

Significance of Light Reaction

In Photosystem II:

• Oxygen is produced from the breakdown of water

• During electron transport, H+ ions accumulate inside

thylakoid – this drives ATP production (Chemiosmosis)

In Photosystem I:

• Electrons combine with a proton to make the energy

carrier NADPH.

Light Independent Reaction (Calvin Cycle)

• Here CO2 is converted into carbohydrates

• Light independent (doesn’t need light)

• Can happen in the day or night

• Occurs in the stroma of the chloroplast

What Pigments are in the Chloroplast?

Pigments – compounds that absorb light energy

Significant pigments involved in photosynthesis

• Chlorophyll a• Only chlorophyll a is directly involved in light reaction of

photosynthesis

• Chlorophyll b• helps to capture light energy

• accessory pigment – helps organism capture more energy

• Carotenoids • accessory pigment – helps organism capture more energy

• Produce – yellow, orange, red, brown colors

• Mostly seen in flowers and fruits

• Also seen during fall when chlorophyll breaks down

Colors of Visible Light

Absorption Spectrum of pigments

Check Yourself!

1. What is a pigment?

2. Why is it advantageous for a plant to have multiple

pigments?

3. What would you prefer to wear in the summer- a black

t-shirt or a white t-shirt (if you had to pick one) and

Why?

What factors affect the rate of photosynthesis?

• Affected by plant’s environment

• Light intensity-

• as light , photosynthesis until light saturation point.

• Carbon Dioxide

CO2 , photosynthesis

• Temperature

• Chemical reactions general with temperature

• If it gets to hot the enzymes can denature and the reaction

What 3 Factors Affect the Rate of

Photosynthesis?

Photosynthesis and plant environment includes:

Light intensity – more light intensity, more electrons in

the chlorophyll molecules of both photosystems to

become excited.

CO2’s influence, increased levels of CO2 stimulate

photosynthesis until a plateau is reached.

0

10

20

30

40

50

60

70

80

90

Light Intensity

Rate

of

Ph

oto

syn

thesis

What 3 Factors Affect the Rate of

Photosynthesis?

Temperature – raising temperature accelerates

the chemical reaction, but it peaks at a certain

temperature. The enzymes that catalyze the reactions become unstable

and ineffective, stomata begins to close limiting water loss

and CO2 entry into the leaves.

0

10

20

30

40

50

60

Temperature

Ra

te o

f

Ph

oto

sy

nth

es

is

What 3 Factors Affect the Rate of

Photosynthesis?

Photosynthesis and plant environment includes:

Light intensity – more light intensity, more electrons in

the chlorophyll molecules of both photosystems to

become excited.

CO2’s influence, increased levels of CO2 stimulate

photosynthesis until a plateau is reached.

0

10

20

30

40

50

60

70

80

90

Light Intensity

Rate

of

Ph

oto

syn

thesis

Review: Link to ecosystems

• Autotrophs- an organism that uses energy to

synthesize organic molecules (sugar) from

inorganic substances (ex. Light)

• Can make its own food

• Includes-plants, some bacteria, and algae

• Heterotrophs – must obtain energy from source

other than self

• Includes animals (humans), fungi, some protista

The ecological Biochemical pathway

Photosynthesis

Cellular

Respiration

Autotrophs &

HeterotrophsAutotrophs

Light

Sugars and oxygen

Carbon dioxide and water

Biochemical Pathway – series of reactions that are linked,

the products of one reaction are consumed in the next

reaction.

Autotroph – an organism that uses energy to

synthesize organic molecules from inorganic

substances.

• Organisms that obtain their energy by making their

own food, like plants.

• Some autotrophs convert water (H20 + CO2) & carbon

dioxide from the environment into energy rich

substances such as sugars and starches

• Examples: Sugars, starches

What is an autotroph?

What Is a Heterotroph?

• An organism that obtains organic food molecules by

eating other organisms or their by-products.

• Organisms that must take in food to meet their

energy needs.

• Examples include: all animals and fungi.

•Also many unicellular organisms.

•A few plant species.

Special Adaptations

• Most plants are C3 plants

• C4 plants • Found in hot dry weather

• They have stomata closed during the hottest part of the day to save up CO2 and water

• Corn, sugar cane, and crabgrass

• CAM• Also found in hot day climates

• Keep stoma open and night and closed during the day to save extreme amounts of water

• Cactus and pineapple

Check Yourself Again!

1. Why is photosynthesis and cellular respiration

considered a biochemical pathway?

2. Why are plants green?

3. What part of photosynthesis makes sugars

(light reactions, electron transport chain or the

Calvin cycle)?

4. What is required from the light reactions in

order to fuel the Calvin cycle?

Reflection Time: Learning Goals

Presentation Learning Goal(s):

1. You can identify organic & inorganic molecules of the process of photosynthesis and write out the equation using proper chemical notation.

2. You can compare the light dependent and light independent reactions of photosynthesis using scientific vocabulary.

3. You can link pigments and the structure of the chloroplast to the process of photosynthesis.

4. You can describe the process of photosynthesis as a part of the biochemical pathway that facilitates the flow of energy and matter through all levels of organization in an ecosystem.

Ticket Out the Door: Rate yourself on one of the learning goals and summarize what you know. Make sure to write out the number of the learning goal.

Reflection Time: Unit LG Scale

4 - You can compare/contrast all components of photosynthesis & cellular respiration in terms of energy, organic and inorganic molecules as well as accurately diagram all the processes as part of the flow of energy and matter through all levels of organization in an ecosystem.

3 - You can compare/contrast some components of photosynthesis & cellular respiration in terms of energy, organic and inorganic molecules as well as diagram most of the processes as part of the flow of energy and matter through all levels of organization in an ecosystem.

2 - You can explain some of the learning goal on your own but may need some help to complete the entire learning goal.

1 - You can answer questions about the learning goal but cannot give specifics using your own words.