PHOTOSYNTHESIS

Photosynthesis

photosynthesis- the process of using light energy from the sun to convert carbon dioxide and water into glucose or carbohydrates

chemical formula: 6 CO2 + 6 H2O + energy C6H12O6 + 6 O2

carbon dioxide + water + energy glucose + oxygen

Autotrophs

performed by autotrophs or plants

autotrophs- organisms that are capable of making their own food, glucose

Conditions Necessary For Photosynthesis

sunlight- only the red and blue wavelengths of white light are involved in photosynthesis

chlorophyll- a green pigment in plants that traps energy from the sun

water- supplies the hydrogen atoms (ions) needed to make glucose

carbon dioxide- supplies the carbon and oxygen atoms needed to make glucose

Photosynthesis

All organisms use energy to carry out functions for life.

All energy is obtained directly or indirectly from the sun.

Some organisms can trap energy from light and store it within organic compounds called photosynthesis.

Importance of Photosynthesis

provides food for plants and animals in the form of carbohydrates or sugar or glucose

uses oxygen as a waste product which is released into the atmosphere

changes the energy from the sun into a usable form for living organisms

provides the structural components in the cell walls of plants which is cellulose

Chloroplasts

photosynthesis takes place inside the chloroplast

chloroplast has a double membrane with the inner membrane having many folds

the folds of the inner membrane fuse to together to form thylakoids

thylakoids- disk-shaped structures that contain chlorophyll; resemble coins

Chloroplast- continued

neatly stacked thylakoids are called grana a gel-like solution surrounds the grana and

completely fills the inner membrane called the stroma

Chlorophyll a absorbs more red light and less blue light than Chlorophyll b

only Chlorophyll a is directly involved in the light reactions of photosynthesis

Process of Photosynthesis

Stage 1- Light Dependent Reactions

Stage 2 – Light Energy Converted to Chemical Energy

Stage 3 – Calvin Cycle

Stage 1: Light Dependent Reaction takes place inside the thylakoids energy is captured by chlorophyll from sun light water is split into hydrogen ions, oxygen ions, and

electrons hydrogen ions are used to make glucose energy released from electrons are used to make

ATP molecules which are high energy molecules oxygen is released from the chloroplast into the

atmosphere energy is also stored in NADP+ which is an electron

acceptor; once joined with an electron it becomes NADPH

Stage 2: Conversion of Energy

light energy is converted to chemical energy

energy is stored in the form of ATP and NADPH molecules

ATP- high energy molecules

NADPH- electron acceptors

Stage 3: Calvin Cycle

occurs inside the stroma

carbon dioxide and hydrogen combine to form glucose

energy stored in ATP and NADPH are used

to form glucose

Stage 1: Light Dependent Reaction

requires sunlight and takes place in the thylakoids

the energy absorbed by the electrons of Chlorophyll a (photosynthesis II or I) causes these electrons to enter a higher energy level or “energized”

energized electrons leave Chlorophyll a (photosystem II) which makes Chlorophyll a oxidized and must undergo reduction to add back electrons

Stage 1: Light Dependent Reaction

energized electrons combine with molecules called the primary electron acceptors

primary electron acceptors- capture these loose electrons

primary electron acceptors guide the electrons to the electron transport chain

electron transport chain- transfers the high energy electrons from one molecule to the next in the series

this energy is used to make ATP molecules

Stage 1: Light Dependent Reaction

an enzyme inside the thylakoid splits a water molecule into hydrogen ions (H+ or protons), oxygen gas, and electrons

electrons released when the water molecule splits in the thylakoid replaces the electrons lost from the Chlorophyll a in photosystem II combine with Chlorophyll a in photosystem I

electrons in both photosystems must be replenished in order for photosynthesis to occur

oxygen is released into the atmosphere

Stage 2: Energy ConversionFirst Path

ATP molecules are made by joining a phosphate group to ADP or two phosphate groups to AMP

ATP or adenosine triphosphate- a high energy compound that supplies energy for all chemical reactions within a living organism

ADP or adenosine diphosphate- results when ATP loses a phosphate group to release energy

AMP or adenosine monophosphate- results when ADP loses a phosphate group to provide energy

Stage 2: Energy Conversion

electrons + ADP + 1 phosphate group = ATP

electrons + AMP + 2 phosphate groups = ATP

Stage 2: Energy ConversionSecond Path

energized electros in Chlorophyll a (photosystem I) are accepted by the primary electron acceptors

again these electron acceptors direct the energized electrons to a different electron chain transport

electrons combine with a hydrogen ion and NADP+ to form NADPH

Stage 2: Energy ConversionSecond Path

NADP+ - an organic compound that accepts electrons

NADPH- an energy storing compound that will be used in the Calvin Cycle

hydrogen is bonded to NADPH to be used in making glucose in Calvin Cycle

Stage 3: Calvin Cycle (Dark Reaction)

energy is supplied by ATP and NADPH which were made in the light reaction

simple inorganic compounds of carbon dioxide are used to make a complex organic compound called glucose or carbohydrates

carbon fixation- carbon atoms from carbon dioxide are bonded into organic compounds

takes place in the stroma of the chloroplasts carbon dioxide combines with a five-carbon

compound called RuBP(ribulose bisphosphate) to form a six-carbon compound

Stage 3: Calvin Cycle

carbon dioxide joins with RuBP to form a six-carbon compound that splits into 2 three-carbon compounds called PGA (phosphoglyceric acid or 3-phosphoglycerate)

PGA is converted into another three-carbon compound called PGAL (phosphoglyceraldehyde)

PGA + phosphate group + hydrogen = PGAL (ATP) (NADPH)

Stage 3: Calvin Cycle

products of the Calvin Cycle are PGAL, phosphate group, ADP, and NADP+

most PGAL is changed back into RuBP

some PGAL is converted into amino acids, lipids, and carbohydrates

Rate of Photosynthesis

light intensity- increase light intensity, increases photosynthesis for a limited time, then levels off

carbon dioxide- increase carbon dioxide, increases photosynthesis for a limited time, then levels off

temperature- increase temperature, increases photosynthesis

chlorophyll- increase the amount of chlorophyll, increase photosynthesis

END

Note Quiz

Note Quiz

1. What are the products of the Calvin Cycle?2. What are the two wavelengths of light that

are used in photosynthesis?3. What is the role of chlorophyll in

photosynthesis?4. What is the compound that carbon dioxide

will combine in the Calvin Cycle?5. What are the products of the Light

Dependent Reaction?

6. What does water supply in the process of photosynthesis?

7. What are the energy sources used in the Calvin Cycle or Dark Reaction?

8. What is PGAL?

9. How is PGA formed?

10. What does carbon dioxide contribute to photosynthesis?