Unit 3: Cellular Energetics Part 1

I.

Obtaining energy

How are organisms classified?

By the way they get energy.

What are the two types of energy gaining classifications?

Autotrophs and heterotrophs

What is an autotroph?

An organism that must use energy from the sun or chemicals to make organic compounds.

What is an heterotroph?

Animals that must get enrgy from food

II.

Photosynthesis Overview

What process do most autotrophs use and what is the purpose of the process?

Photosynthesis ; they use photosynthesis to convert light energy from the sun into chemical energy in the form of organic compounds, mostly glucose

What are the two types of parts that photosynthesis can be divided into ?

Light dependent reactions and Light Independent reactions

What is another name for Light Independent reactions?

The Calvin cycle

What are light dependent reactions?

Light energy(absorbed from the sun) s converted into chemical, which is temporarily stored in ATP and the energy carrier molecule NADPH.

III.

Capturing Light Energy

What does the first stage of photosynthesis include/require

The light reactions / sunlight

Where does the absorption of light in a plant occur?

In the chloroplasts

What are the chloroplasts surrounded by?

A pair of membranes

What does the inner membrane of the pair of membranes that surround chloroplasts contain?

Flattened sacs called thylakoids

What surrounds the stacks of thylakoid?

A solution called stroma (a liquid similar to cytoplasm

IV.

Light and Pigments

Although light from the sun appears white, what is the light actually made out of?

A variety of colors called the visible spectrum

How can these colors be seperated / where do these colors range?

By a prism / range from red to violet

What is a pigment?

A compound that absorbs certain wavelengths of light leaving only the others to be reflected back.

V.

Chloroplast Pigments

What do the membranes of thylakoids contain?

Pigments, most of which are chloropylls

What are the two most common types of chlorophylls?

Chlorophyll A and Chlorophyll B

What type of light does Chlorophyll A absorb more of?

Red light

What type of light does Chlorophyll B absorb more of?

Blue light

What do neither Chlorophylls absorb much of

Green light

VI.

Converting Light Energy to Chemical Energy

What must happen when pigments capture light?

The (light) energy must be converted into chemical energy (ATP and NADPH)

What are clustered within proteins?

Hundreds of pigments

What are these hundreds of pigments called?

Photosystems

What are the two types of photosystems?

photosystem I and photosystem II

VII.

Steps of Light Reactions

Step 1:

Light energy forces electrons to enter a higher energy level in the two chlorophyll A molecules of photosystem A

What these electrons said to be?

"excited"

What does this mean they can do?

That they can leave the chlorophyll A molecules

Step 2:

A molecule in the membrane of the thylakoid called the primary electron acceptor takes the elctrons fom the chlorophyll A molecules.

Step 3:

The primary electron acceptor gives electrons to another molecule in the thylakoid membrane which gives them to another, and another, and so on

What are these molecules called?

An electron transport chain (ETC)

What happens to electrons each time they are passed from molecule to molecule?

The lose some energy which is used to move protons (H+) into the thylakoid

Step 4:

The electrons finally go to replace the electrons that are leaving another group of pigments in photosystem I. These electrons also move from molecule to molecule in another ETC

Step 5:

This chain brings electrons to the side of the thylakoid closest to the stroma where they combine with NADP+ and a proton to make NADPH

VIII..

Replacing Electrons

What would happen to stop the photosystems if electrons were not replaced?

They would stop

What helps to replace the electrons that left photosystem II?

An enzyme beside photosystem II that splits water molecules into electrons, protons, and oxygen

Where are the protons pushed?

They are pushed into the thylakoid and the oxygen is released from the plant

IX.

Making ATP in Light Reactions

What is the whole purpose of the light reactions?

To push protons from the stroma to the inside of the thylakoid

When do the protons get pushed into the thylakoid?

Each time electrons pass from one molecule to the next

What happens to these protons?

They become highly concentrated inside of the thylakoid and want to leave

What is the enzyme that lets protons escape and uses the energy from them to put together ATP molecules and where is it located?

ATP synthase; in the membrane

X.

The Calvin Cycle

What is the Calvin Cycle (what does it do)?

The second set of reactions in photosynthesis that uses energy from ATP and NADPH during the light reactions to produce organic molecules in the form of sugars (stage 2 of photosynthesis)

XI.

Carbon Fixation

What in the Calvin Cycle produces a 3 carbon sugar?

A series of enzyme-assisted reactions

What happens to CO2 in this process?

CO2 is bonded or "fixed" into organic compounds

What is this process called?

Carbon fixation

Where does the Calvin Cycle occur?

In the stroma of the chloroplasts