Lesson 6Understanding Plant Physiology

Next Generation Science/Common Core Standards Addressed!

HS‐LS1‐3. Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis. [Clarification Statement: Examples of investigations could include heart rate response to exercise, stomate response to moisture and temperature, and root development in response to water levels.] [Assessment Boundary: Assessment does not include the cellular processes involved in the feedback mechanism.]

HS‐LS1‐5. Use a model to illustrate how photosynthesis transforms light energy into stored chemical energy. [Clarification Statement: Emphasis is on illustrating inputs and outputs of matter and the transfer and transformation of energy in photosynthesis by plants and other photosynthesizing organisms. Examples of models could include diagrams, chemical equations, and conceptual models.] [Assessment Boundary: Assessment does not include specific biochemical steps.]

Bell Work

Describe cellular respiration.

When these things are combined, what is produced as a result?

What are the ingredients needed for photosynthesis to take place?

Why are photosynthesis and Respiration important to humans?

Here is a glass of water. How can I add carbon dioxide to it?

Vocabulary

Cellular respiration

Chlorophyll

Chloroplast

Mitochondria

Photosynthesis

Transpiration

How Does Photosynthesis Work?

Photosynthesis is the process by which a plant turns the light energy from the sun into chemical energy in the form of sugar (glucose)

It is a complex series of chemical reactions that happens within the plant cells

It is the original source of all important fuels including oil, coal, wood, and natural gas

It is also the source of all foods

Most cells that carry on photosynthesis have organelles called chloroplastsThey contain a pigment known as

chlorophyllChlorophylls are usually green

because they absorb the red and blue wavelengths of light and reflect the green wavelengths

The pigment is responsible for trapping the sunlight for photosynthesis to occur

In photosynthesis, carbon dioxide and water are the raw materials

They are used to form glucose and oxygen

The formula for photosynthesis is:

6 CO2 + 12 H2O C6H12O6 + 6 H2O + 6 O2

Carbon dioxide Water Glucose Water Oxygen

Photosynthesis continuedNotice that water is both a raw material and a

productThis is because there are two steps involved in

photosynthesis: the light and dark reactionsAny excess water is removed through the stomata

of the leaves by a process called transpirationIn the light reaction, light energy is converted

to chemical energy and water is split into hydrogen and oxygen atoms

In the dark reaction, carbohydrates are formed from carbon dioxide and hydrogen atoms

Both processes occur within the chloroplast

Structure of a Chloroplast

A chloroplast contains stacks of membranes called grana which store the chlorophyll

Surrounding the grana are regions called stroma

The light reaction takes place in the grana while the dark reaction occurs in the stroma

Chloroplast

Factors that Affect Photosynthesis

Photosynthesis is affected by six factors: 1. Light quality – the best type of light should provide

wavelengths in the blue and red range; This range is what works best with chlorophyll

2. Light intensity – some plants need more light, others less; generally, the brighter the light, the more efficient the photosynthesis

3. Light duration – the longer the day, the more photosynthesis takes place; Some plants need more light and some less

4. Carbon dioxide concentration – usually an increase in the amount of carbon dioxide in the atmosphere can double the rate of photosynthesis

5. Temperature – the higher the temperatures the more photosynthesis occurs; Of course excessive temperatures will decrease the rate too

6. Water availability – plants lacking water will close their stomata and decrease photosynthetic activity

How Does Respiration Work?

In many ways, cellular respiration is the opposite of photosynthesis:Comparison of

Photosynthesis & Respiration

Photosynthesis Respiration

Produces food Uses food for energy

Occurs in cells that contain chloroplasts

Occurs in all cells

Oxygen released Oxygen used

Water used Water produced

Carbon dioxide used

Carbon dioxide produced

Occurs in sunlight Occurs in dark & light

In respiration, plants start with glucose which is broken down in the presence of oxygenWater and carbon dioxide are

released along with all the energy within the bonds

This is the formula for respiration:

C6H12O6 + 6 H2O + 6 O2 6 CO2 + 12 H2O Glucose Water Oxygen Carbon dioxide Water

Factors Affecting Respiration

Respiration occurs in structures called mitochondria and are affected by five factors:1. Temperature – as

temperature increases, so does the respiration rate

2. Oxygen concentration – low concentrations of oxygen will decrease the respiration rate

Mitochondrion

3. Soil Conditions – compacted or waterlogged soils exclude air, and therefore oxygen; Respiration is inhibited under these conditions

4. Light – in low light, photosynthesis is reduced and therefore the rate of respiration is reduced because of a decrease in available glucose

5. Growth rate & metabolic activity – when plants reach their full development, the rate of photosynthesis and respiration have reached their maximum; Age and availability of glucose affect respiration

How Are Photosynthesis & Respiration Important to Humans?

Photosynthesis and respiration are two of the most important chemical reactions to human beingsAll of our food and nutrition comes either directly of

indirectly from photosynthesis

All of our heat and electricity comes either directly or indirectly from by-products of photosynthesis in plants

All of the oxygen we breathe comes from the photosynthesis reactions

Transpiration puts thousands of tons of water into the air, cooling our environment and encouraging rainfall.

Summary

What is photosynthesis?What are the two raw materials needed for

photosynthesis? What are the products?Where in a cell does photosynthesis take

place?Can humans produce food?Why or why

not?Where do the light and dark reactions

occur in a chloroplast?What is respiration?

Summary Continued

What are the raw materials needed for respiration? What are the products?

Where in a cell does respiration occur?How is respiration the opposite of

photosynthesis?Why are these two processes necessary

for humans?What factors affect the rate of

photosynthesis and respiration?

The End!