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Miller and Levine Biology: Chapter 8-Photosynthesis

Mr. Maffin's edited version
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Photosynthesis
Conversion of light energy from the sun into chemical energy.
pigment
A colored chemical compound that absorbs light
chlorophyll
A green pigment found in the chloroplasts of plants, algae, and some bacteria
thylakoid
A flattened membrane sac inside the chloroplast, used to convert light energy into chemical energy.
photosystem
A cluster of pigments embedded into a thylakoid membrane.
stroma
The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.
NADP+
carrier molecule that transfers high-energy electrons from the electron transport chain (photo sys I, II) to become NADPH
light-dependent reactions
reactions of photosynthesis that use energy from light to produce ATP and NADPH
ATP synthase
Large protein that uses energy from H+ ions to bind ADP and a phosphate group together to produce ATP
Calvin Cycle

(Or light independent reactions)
reactions of photosynthesis in which energy from ATP and NADPH is used to build high-energy compounds such as sugars from CO2 from the atomosphere
Where does the energy from food originally come from?
The Sun
What is a difference between autotrophs and heterotrophs?
Autotrophs make their own food while heterotrophs do not
Examples of Autotrophs
Plants - organisms that transform light energy to useable compounds
Examples of Heterotrophs
Animals - organisms that consume useable compounds for energy
What is one of the principal chemical compounds that cells use to store energy?
ATP - adenosinetriphosphate
When a cell has energy available, how can it store small amounts of that energy?
They can add a phosphate group to an ADP to make ATP, also adding electrons and a Hydrogen ion to NADP+ to make NADPH.
How is ATP different from ADP?
ATP has 3 phosphate groups while ADP has 2.
List the parts of an ATP molecule
Adenine, Ribose, and 3 Phosphate groups
When is the energy stored in ATP released?
When the second and third molecules of the three phosphates are broken apart. (bond is broken)
What are the characteristics of ATP that makes it exceptionally useful to all types of cells?
It has enough energy to power a variety of cellular activity
Ways cells use ATP (5 ways)
1) Provides energy for motor proteins that moves organelles throughout the cell
2) Carries out active transport
3) Synthesize proteins
4) Responses to chemical signals at the cell surface
5) Can be used to produce light
Where do cells get their energy from ATP?
Through recycling ADP back into ATP. It does so by adding a phosphate group back to ADP
What happens in photosynthesis?
Plants use sunlight to convert water and carbon dioxide into high energy carbohydrates and oxygen
What is the equation for photosynthesis
6CO2 + 6H20 ->(light) C6H12O6 + 6O2

Carbon dioxide + water (light) sugars + oxygen
Reactants of Photosynthesis
Carbon Dioxide + water
Products of Photosynthesis
Sugars (primarily glucose) + oxygen
In addition to water and carbon dioxide, what do plants need to preform photosynthesis?
light and chlorophyll
Light absorbing molecules that gather the sun's energy; found in plants
Pigments
Chlorophyll
Principal pigments in plants, chlorophyll a, chlorophyll b
What is another pigment which can be used to power photosynthesis other than chlorophyll?
Carotenoids
Why are plants green?
Pigments reflect electromagnetic wavelenghts which is interpreted as green
What colors do pigments absorb very well?
Blue-violet rays and red rays
What happens when chlorophyll absorbs light?
much of the energy is transferred directly to electrons in the chlorophyll molecule, this raises the energy of the electrons, which makes photosynthesis work
saclike photosynthetic membranes that are located in chloroplasts that aid in photosynthesis are called ____
Thylakoids
What is a granum?
stack of thylakoids
region outside the thylakoid membranes in the chloroplasts is called ____
stroma
what are the 2 stages of photosynthesis?
1) Light Dependent Reactions
2) Light Independent Reactions or Calvin Cycle
Reactant of light dependent cycle
H20 Water
Product of light dependent cycle
O2 Oxygen
When sunlight excites electrons in chlorophyll, how do the electrons change?
They gain energy.
What is a carrier molecule?
They transport high-energy electrons from chlorophyll to other molecules.
How does NADP+ become NADPH?
They accept and hold two energy electrons along with an H+ ion.
What does NADPH do?
they carry high-energy electrons produced by light absorption in chlorophyll to chemical reactions elsewhere in the cell. These high-energy- electrons are used to help build a variety of molecules the cell needs, including carbohydrates like glucose
What happens in the light- dependent reactions?
Light is converted through many energy transformations into the chemical energy carriers of ATP and NADPH
Where do the light-dependent reactions take place?
Inside the chloroplast within the thylakoid membrane
Step 1 of LDR: What happens in the Photosystem II in light dependent reaction?
Light absorbed by photosystem II is used to break up water molecules into energized electrons (e-), hydrogen ions (H+), and oxygen
Step 2 of LDR: What happens in the electron transport chain?
Low energy electrons from photosystem II move through the electron transport chain to photosystem I
Step 3 of LDR: What happens in photosystem I?
Electrons released by photosystem II are re-energized in photosystem I to become high energy electrons again. Enzymes in the membrane uses these electrons to form NADPH. NADPH is used to make sugar in the Calvin cycle (Light independent reactions).
What causes the increase of hydrogen ions in the thylakoid membrane?
An enzyme breaks hydrogen (H+) from water. Then electrical energy (e-) in the thylakoid membrane powers a proton pump to move H+ into the thylakoid space. This creates an increase of potential energy in the thylakoid space
Step 4 of LDR: What is the Hydrogen Ion movement?
The inside of the thylakoid membrane fills up wiht positively charged hydrogen ions. This action makes the outside of the thylakoid membrane negatively charged and the inside positively charged.
Step 5 of LDR: How does the ATP Synthase produce ATP?
As H+ passes through the ATP synthase, their energy is used to convert ADP into ATP
What is the Calvin Cycle?
A process where ATP and NADPH from the light- independent reactions are transformed into high energy sugars and other compounds.
Why can the Calvin Cycle be known as light- independent reactions?
They do not need light to occur
Where does the Calvin Cycle take place?
In the stroma of chloroplasts
Step 1 of CC : Co2 enters the cycle
6 carbon dioxide molecules are combined with six 5 carbon molecules to produce twelve 3 carbon molecules
Step 2 of CC: energy input
Energy from ATP and high energy electrons from NADPH are used to convert the twelve 3 carbon molecules into higher energy forms
Step 3 of CC: 6 carbon sugar produced
Two 3 carbon molecules are removed from the cycle to produce sugars, lipids, amino acids, and other compounds
Step 4 of CC: 5 carbon molecules regenerated
The 10 remaining 3 carbon molecules are converted back into six 5 carbon molecules, which are used in the cycle.
Reactants of Calvin Cycle
6 carbon dioxide molecules
Products of Calvin Cycle
sugars, lipids, amino acids, and other compounds
Factors that affect the rate of which photosynthesis occurs (3 ways)
1) Shortage of Water- can slow or stop photosynthesis
2) Temperature- 0 degrees C - 35 degrees C ideal temp, above or below, damages enzymes, decreases rate or may stop if too below
3) Light Intensity- Increasing the intensity of light increases the rate of photosynthesis, decreasing light slower rate
Difference between Light-Dependent Cycle and Light-Independent Cycle (2 ways)
1) LIC does not use light, LDC does
2) LDR makes ATP and NADPH, LIC uses said atp and nadph into high energy sugars
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