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Photosynthesis • Why don’t bushes or other trees usually grow underneath large trees?

Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

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Page 1: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

Photosynthesis

• Why don’t bushes or other trees usually grow underneath large trees?

Page 2: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

Lesson Objectives• Identify the kind of energy that powers life.• State why living things need energy.• Evaluate the importance of autotrophs for providing energy

to all life.• Describe how autotrophs and heterotrophs obtain energy.• Define chemosynthesis.• Compare and contrast glucose and ATP.• Outline how living things make and use food.• Outline the stages of photosynthesis.• Describe the chloroplast and its role in photosynthesis.• Identify the steps of the light reactions and the Calvin

cycle.

Page 3: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

Terminology Review

• What is energy?

_________________________________

• What is the ultimate source of all energy?

_________________________________

The ability to do work.

Sunlight

Page 4: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

Kinds of energy which power life• What forms can energy come in?

__________________________________

• Where is energy stored? __________________________________

• How is this energy released? __________________________________

Light, heat, chemical, nuclear, magnetic, and electrical

In chemical bonds

By breaking the chemical bonds

Page 5: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

How Do Organisms Get Energy? Autotrophs vs. Heterotrophs

Living organisms obtain chemical energy in one of two ways.

They make it themselves OR They consume those who can make it themselves

Page 6: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

CAN MAKE IT THEMSELVES Autotrophs—Photosynthesize

• Plants, algae, and some bacteria

• Producers, begin food chains which feed all life– Store chemical energy in carbohydrate food

molecules• Organic molecules made through photosynthesis

store chemical energy (food)

Page 7: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

Photosynthesis

• Provides over 99 percent of the energy supply for life on earth– Uses solar energy to convert water and

carbon dioxide into oxygen and glucose

Page 8: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

CONSUMERSHeterotrophs• Animals, fungi, and many protists and

bacteria

• Consumers, cannot make their own food– Obtain energy through food consumption

• Autrotrophs or other Heterotrophs

– Highly diverse organisms

Page 9: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

Chemosynthesis

• Other autotrophs: mostly bacteria in dark or low-oxygen environments – produce food using the chemical energy

stored in inorganic molecules such as hydrogen sulfide, ammonia, or methane.

Tubeworms deep in the Gulf of Mexico get their energy from chemosynthetic bacteria living within their tissues. No digestive systems needed!

Page 10: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

Food to Energy Molecules: Glucose and ATP

• Two of the most important energy-carrying molecules

• Glucose: simple carbohydrate; energy-rich product of photosynthesis; chemical formula C6H12O6

– “deliverable” form of energy; carried in blood through capillaries and taken up by trillions of cells

– nearly universal food for life.

• ATP: store smaller quantities of energy; product of first stage of photosynthesis and used during second stage to make glucose

– provides cells with energy for cellular processes

– “useable” form of energy for your cells

Page 11: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

Why Organisms Need Both Glucose and ATP

• Glucose more chemical energy in a smaller ‘‘package” than a molecule of ATP– more stable than ATP; better for storing and transporting

energy– BUT too powerful for cells to use.

• ATP right amount of energy to power life processes within cells– like a rechargeable battery

• energy released when broken down into ADP and phosphate

• “worn-out battery” ADP recharged using new energy to attach a new phosphate; rebuilds ATP.

Page 12: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

ATP and ADP

• ATP: adenosine triphosphate; principle chemical compound in which living things store energy.

Adenine: nitrogen-containing compoundRibose: a 5-carbon sugar3 phosphate groups

Page 13: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

• ADP: adenine diphosphate; structural similar to ATP but with one important difference: ADP has only two phosphate groups. ADP is converted to ATP when available energy is used to add a phosphate group to it.

ADP

two phosphates

Adenine: nitrogen-containing compoundRibose: a 5-carbon sugar2 phosphate groups

Page 14: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

Releasing Energy from ATP

• Energy stored in ATP is released when it is converted to ADP and a phosphate group.

O

Adding or subtracting a 3rd phosphate group allows the cell to store and release energy as it is needed

Page 15: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

Using Biochemical Energy• How the cells use ATP:

– To conduct active transport; like the sodium-potassium pump

• It moves sodium ions (Na+) out of the cell and potassium ions (K+) into the cell

• A single ATP molecule provides the energy to move three sodium ions and two potassium ions in different directions

– Powers movement within the cell• Moves cell organelles along microtubules by motor proteins

that use energy from ATP to generate force

http://student.ccbcmd.edu/~gkaiser/biotutuorials/eustruct/sppump.html

Page 16: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

Photosynthesis: The Most Important Chemical Reaction for Life on Earth

• Necessary conditions include: – enzymes - proteins to speed up chemical

reactions – chlorophyll - a pigment which absorbs light – chloroplasts – which contain chlorophyll,

accessory pigments, and enzymes in patterns which maximize photosynthesis

Page 17: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

Stages of Photosynthesis• Two stages:

– light reactions uses water; changes light energy into chemical energy

• releases oxygen as a waste product.

– Calvin cycle uses chemical energy in ATP and NADPH to make glucose

Page 18: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

Chloroplasts: Theaters for Photosynthesis

• Chloroplast contain:– neat stacks called grana (singular, granum).

• consist of sac-like membranes, known as thylakoid membranes

– Thylakoid membranes• contain photosystems

– groups of molecules that include chlorophyll

• light reactions occur in thylakoid membranes.

– stroma • space outside the thylakoid membranes

• reactions of the Calvin cycle occur here

Page 19: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

Chloroplasts Function• Work with enzymes and two basic

molecules: pigments and electron carriers

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• Electron carrier molecules are usually arranged in electron transport chains (ETCs).

Page 21: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

Photosynthesis Stage I: The Light ReactionsChloroplasts Capture Sunlight’s Energy

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Light-Dependent Reactions

• Require LIGHT• Use light energy to produce

– Oxygen gas– Convert ADP to energy carrying ATP– Convert NADP+ to energy carrying NADPH

Page 23: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?
Page 24: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

Photosynthesis Stage II: The Calvin CycleMaking Food “From Thin Air”

• Three major steps:– Carbon fixation– Reduction– Regeneration

http://www.science.smith.edu/departments/Biology/Bio231/calvin.html

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Why is Carbon Dioxide “Fixed”• Life on Earth is carbon-based

– needed in building blocks of biological molecules– ultimate source of carbon is carbon dioxide

• Animals and most other heterotrophs cannot take in CO2 directly

• Only autotrophs can build low energy inorganic CO2 into high-energy organic molecules like glucose

Page 26: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

Three Pathways for Carbon Fixation—Calvin Cycle

1. C-3 pathwaya. Most common b. 6-C molecule splits into two 3-C molecules

2. C-4 pathway a. creates a 4-C molecule 3. CAM (Crassulacean Acid Metabolism) a. cacti and succulents b. Fix carbon dioxide at night

Dry air, hot temperatures, bright sunlight lead to below two pathways:

Page 27: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

Factors Affecting Photosynthesis

• Shortages of water slow process down; can stop it– Plants that live in dry areas have a waxy coating on

their leaves that reduces water loss

• Temperature also can slow or stop it– Enzymes used by plants for photosynthesis function

best between 0°C and 35°C (32°F to 95°F)

• Intensity of light – More light = greater rate of photosynthesis until

maximum reached• Maximum rate varies from plant to plant

Page 28: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

Let’s Review• Where does photosynthesis occur?

_________________• What are the saclike photosynthetic membranes

in the chloroplast called? _________________• The thylakoids are arranged in stacks called

__________.• What is found inside the grana?

______________________________________• What are photosystems?

______________________________________• What do photosystems do?

______________________________________

In the chloroplasts

thylakoids

grana

Clusters of chlorophyll and other pigments

Proteins found in the grana

They capture the energy of sunlight

Page 29: Photosynthesis Why don’t bushes or other trees usually grow underneath large trees?

• How many stages does photosynthesis have? ______

• What are they? ____________________________________________________________________

• Where do the light-dependent reactions take place? __________________________________

• Where do the light-independent reactions take place? __________________________________

2

Light reactions

Light-independent reactions (Calvin cycle)

Thylakoid membrane

Stroma; region outside of the thylakoid membrane