the big intro

The Big Intro

• This is all about the relationship between two chemical processes found in living cells

• Autotrophs make nutrient molecules, and

• Both Autotrophs and Heterotrophs use these nutrient molecules for their energy needs. This is cellular respiration and comes later.

Photosynthesis

Photosynthesis in Overview

• Process by which plants and other autotrophs store the energy of sunlight into sugars.

• Requires sunlight, water, and carbon dioxide.• Overall equation:

6 CO2 + 6 H20 C6H12O6 + 6 O2

• Occurs in the leaves of plants in organelles called chloroplasts.

Leaf Structure• Most photosynthesis occurs in the palisade layer.• Gas exchange of CO2 and O2 occurs at openings called

stomata surrounded by guard cells on the lower leaf surface.

Palisade

Spongy

Chloroplast Structure• Inner membrane

called the thylakoid membrane.

• Thickened regions called thylakoids. A stack of thylakoids is called a granum. (Plural – grana)

• Stroma is a liquid surrounding the thylakoids.

Pigments

• Chlorophyll A is the most important photosynthetic pigment.

• Other pigments called antenna or accessory pigments are also present in the leaf.– Chlorophyll B– Carotenoids (orange / red)– Xanthophylls (yellow / brown)

• These pigments are embedded in the membranes of the chloroplast in groups called photosystems.

Photosynthesis: The Chemical Process

• Occurs in two main phases.– Light reactions– Dark reactions (aka – the Calvin Cycle)

• Light reactions are the “photo” part of photosynthesis. Light is absorbed by pigments.

• Dark reactions are the “synthesis” part of photosynthesis. Trapped energy from the sun is converted to the chemical energy of sugars.

Light Reactions

• Light-dependent reactions occur on the thylakoid membranes.– Light and water are required for this

process.– Energy storage molecules are formed.

(ATP and NADPH)– Oxygen gas is made as a waste product.

Dark Reactions

• Dark reactions (light-independent) occur in the stroma.– Carbon dioxide is “fixed” into the

sugar glucose.– ATP and NADPH molecules

created during the light reactions power the production of this glucose.

Photosynthesis

Let’s take a closer look

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How Plants Make Sugars

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Pay attention; this is the lesson!

In this interactive lesson you will learn how plants take carbon from the air to make glucose

Have you ever thought about where plants get the energy to grow?

Is it from the soil?Is it from the rain?

Or is it from the sun?

Let’s get started with navigation basics first

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Navigation – from here on out you:

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Click on this Home Icon to go to the Main Menu.

Click this Left Arrow Icon to go forward one slide.

Lesson Menu

Lessons to learn:

1. ATP – The Energy Currency

2. Chloroplasts

3. Photosynthesis – Light Dependent Reactions

4. Photosynthesis – Light Independent Reactions

Assessment

Have you ever used a rechargeable battery?

Well, every living thing uses the same molecule for the short-term storage of energy. It is called ATP. The function of this molecule

can be compared to a rechargeable battery.

What does this word currency mean?

Let’s look to the web for a definition – click here ?

This molecule is called the energy currency of ALL living things!

LESSON 1

http://dictionary.reference.com/search?q=currency

So by calling ATP the energy currency of all cellswe mean that different parts of cells exchange

this molecule when energy is needed and consumed.

Since all living organisms use this same ATP molecule, an analogy to this would be going anywhere in the world and being able to

buy goods with dollars, quarters, and nickels and other U.S. currency.

So how is this molecule like a re-chargeable battery?

Let’s find out!

This is a graphic representation of ATP

Notice the three main parts of ATP:1. Adenine – a nitrogenous base2. Ribose – a sugar3. 3 Phosphate molecules

Go back and look at the ATP graphic again.It also has a bond labeled a high-energy bond.

Do you remember what this implies?

Energy is stored in the bonds of molecules.

ATP is unstable.

(click on your answer)

That’s right!Energy is stored in the bonds of molecules.

Remember from our unit on Biochemistry that wheneverchemical bonds are formed or broken energy is exchanged.

When bonds are broken energy is releasedand generally, energy is needed to form bonds.

What about the re-chargeable battery analogy?

3 phosphates attached to the adenosine molecule representsa fully charged battery, with a maximum number

of energy–rich chemical bonds.

The adenosine molecule itself is the fully charged battery.

(click on your answer)

See if you can deduce the correct answer.

Excellent!When 3 Phosphates are attached to adenosine

this energy currency is at its highest denomination,like a fully charged battery.

This molecule is again called adenosine triphosphate or ATP.

The fewer phosphates, the less energy these molecules havebecause they have fewer bonds from which to release energy.

Adenosine diphosphate(Half-charged battery)

Adenosine monophosphate(dead battery)

This concludes lesson 1.

Photosynthesisis

The absorption of light energy from the sun by specialized organelles.

That use this energy to power chemical reactions that

use water and “fix” carbon dioxide from the atmosphere

into energy storage molecules called glucose.

LESSON 2

It is the occurrence of two successive seriesof chemical reactions called:

1. Light dependent reactions2. Light independent reactions

What was the specialized organelle we studied in the cells unit where photosynthesis occurs?

Vacuole

Chloroplast

Good job!

Chloroplasts are the specialized organelle in plants and some algae where photosynthesis occurs.

This view would be through a cross-section of the leaf

The light dependent reactions (subject of lesson 3)occur in the thylakoid membrane .

The light independent reactions (subject of lesson 4)occur in the stroma.

The thylakoids (as seen in the graphic) are arranged like a stack of coins called a granum, with

the side of the granum oriented towards the sunfor maximum light exposure.

This concludes lesson 2.

LESSON 3

As stated in lesson 2 photosynthesis involves water, CO2,light energy and sugars, but let’s get more specific.

Let’s look at the chemical and word formulas for photosynthesis.

6CO2 + 6H20 sunlight C6H12O6 + 6O2

Carbon dioxide + water sunlight glucose + oxygen

Next is a concept map of the whole process.

Photosynthesis

includes

of

occur inoccurs in uses

to produce to produce

uses

Lightdependentreactions

Thylakoidmembranes Stroma NADPHATPLight

Energy

ATP NADPH O2 Chloroplasts Glucose

Lightindependent

reactions

Concept Map

Here’s a graphic representation of the twoseries of reactions.

The light-dependent reactions are comprised oftwo sets of reactions called photosystems.

Photosynthesis begins with Photosystem IIbecause it was the first set of reactions discovered.

The light dependent reactions capturethe energy of the sun.

Photosystem II

Begins with absorption of energy (photon) by a chlorophyll molecule (Chl).

The chlorophyll molecule is raised to an excited state.

The electron lost by the chlorophyll is replaced by the enzymatic splitting of water

This electron is passed down a chain of molecules called the electron transport chain or redox chain.

Energy from this transfer of electrons is used to produce ATP, leaving the electron in a low energystate to be recharged by Photosystem I

The low energy electron from photosystem IIreplaces one that in photosystem I that has become energized and left the chlorophyll Molecule in photosystem II.

Energy from this excited electron is exchangedacross different molecules (called carriers) ultimately being used to convert NADP+ to NADPH.

NADPH stores this electrical energy for use in the light independent reactions.

The Light Dependent Reactions(Overview)

Where did the light dependent reactionstake place again?

In the stroma

In the thylakoid membranes

Correct!

This completes lesson 3

LESSON 4

Let’s Review

The two series of chemical reactions that comprisePhotosynthesis are called?

Photosystem I and Photosystem II

Light dependent and Light independent

Correct!

The two series of chemical reactions that comprisephotosynthesis are called the:

Light dependent reactions – they require light and therefore occur in the thylakoid membrane

Light independent reactions – these don’t require light and occur in the stroma

Light Independent Reactions(also called Calvin Cycle, after man who discovered them)

Are a cyclical set of reactions that use the CO2 from the atmosphere to make the high energy sugar glucose

Take a look at the overview of photosynthesis again

Here’s an overview of the Calvin Cycle.Next we’ll break it down in stages.

Acronyms we’ll use

RuBP - ribulose biphosphate

PGA - phosphoglycerate

PGAP - diphosphoglycerate

PGAL - phosphoglyceraldehyde

The quantities listed are for the production of one glucosemolecule which is produced from six turns of the cycle

The cycle starts when (3) 5-carbon molecules(from the previous cycle) of RuBP combine with(3) CO2.molecules from the atmosphere.

This combination of molecules forms six moleculesof the 3-carbon compound PGA.

The energy and phosphates from six ATP’s is taken to convert the 6 PGA’s to 6 PGAP’s

Where did these ATP’s come from?

The Light dependent reactions

The mitochondria

You are right!

In this next step the energy from 6 NADPH’sis used to remove the phosphate moleculesforming 6 PGAL’s

Where did these NADHP’s come from?

The cytoplasm

The Light dependent reactions

You are correct!

At this point (after three turns of the cycle)one of these PGAL’s leaves the cycle.

Six turns of the cycle produces 2 of these PGAL molecules which combineto form a glucose molecules.

The remaining 5 PGAL molecules are converted to (3) 5-carbon intermediates, then back to 3RuBP molecules to start the cycle again.

This completes lesson 4

ASSESSMENTQuestion 1 of 5

The energy currency of all cells in all organisms is

Adenosine diphosphate

Adenosine triphosphate

Adenosine monophosphate

Correct

Continue on to Question 2


The two series of chemical reactions that comprisephotosynthesis are called

Photosystem I and photosystem II

Cellular Respiration

Light dependent and light independent

Correct



The light independent (also called dark reactions) occur in the)

stroma

thylakoid membrane

cytoplasm

Correct



The three parts of ATP are

adenine, thylakoids, stroma

stroma, grana, chlorophyll

adenine, ribose, phosphate

Correct



What are products of the light dependent reactions?

oxygen gas

ATP

NADPH

All of the above

Correct

You have now completed the test.

Return to Title Slide

Move on to RespirationMove on to Respiration

Incorrect

Go back and select the correct answer.

Cellular Respiration

• Now let’s see what all the excitement is about in the release of energy in cells

RespirationRespiration

• Respiration the process by which food molecules are broken down– Food molecules are 6-carbons sugars – You take in food which is digested and

broken down into 6-carbon sugars– Plants can’t “eat” so they make 6-

carbon sugars with photosynthesis– Mitochondria then transform the “food

energy” into chemical energy


• A 6-carbon sugar contains an enormous amount of energy (for a cell)

• Mitochondria “make change” energetically ($100 bill to 20 $5 bills - easier to spend)

• Take the energy in a complex sugar and convert it into more conveniently-sized packages of adenosine triphosphate


C6H12O6 + 6O2 → 6CO2 + 6H2O + energyCarbondioxide

WaterCarbohydrate Oxygen


• Aerobic respiration: processes that require oxygen in order to take place

• Anaerobic respiration: processes that do not require oxygen

Aerobic RespirationAerobic Respiration

• Step 1: Glycolysis

• Step 2: Breakdown of pyruvic acid

• Step 3: Citric acid cycle

• Step 4: Electron transport chain


MATRIX:Breakdown ofpyruvic acid, Citric acid cycle

INNER MEMBRANE:Electron transportchain

Outer membrane

CYTOPLASM:Glycolysis

Step 1: GlycolysisStep 1: Glycolysis

• Occurs in cytoplasm

• Does not require oxygen

• Involves splitting a glucose (6-carbon sugar) into 2 3-carbon molecules: pyruvic acid


• Also produces H+ ions and energizes electrons which are captured by NAD+, forming NADH + H+


• Uses up 2 ATP

• Produces 4 ATP

• Net yield = 2 ATP


Glucose


Glucose

2 ATP 2 ADP


Glucose

2 ATP 2 ADP

P

P

2 PGAL


Glucose

2 ATP 2 ADP

P

P

2 PGAL

4ADP + 4 Pi

2 NAD+ 2NADH + 2H+

4ATP


Glucose

2 ATP 2 ADP

P

P

2 PGAL

4ADP + 4 Pi

2 NAD+ 2NADH + 2H+

4ATP

2 Pyruvicacid


Step 1: Glycolysis




Step 2: Breakdown of Step 2: Breakdown of Pyruvic AcidPyruvic Acid

• Occurs when pyruvic acid (from glycolysis) enters the mitochondrial matrix

• Requires oxygen– If there is no oxygen present pyruvic

acid enters fermentation


• Involves breaking CO2 off pyruvic acid

• Remaining portion of pyruvic acid combines with coenzyme A to form acetyl-CoA


• Also produces H+ and energizes electrons which are captured by NAD+, to form NADH + H+


To citricacid cycle

Mitochondrialmembrane

“Exhaled”


Step 1: GlycolysisStep 2: Breakdown of pyruvic acid



Step 3: Citric Acid CycleStep 3: Citric Acid Cycle

• Occurs in mitochondrial matrix

• Acetyl-CoA is transformed into citric acid through a series of reactions


• More ATP and CO2 are produced

• More H+ are produced and electrons are energized

• NAD+ and FAD capture them to form NADH + H+ and FADH


CITRICACID

CYCLE

4C

5C

6C – Citric acid


Step 1: GlycolysisStep 2: Breakdown of pyruvic acidStep 3: Citric acid cycle


Step 4: Electron Transport Step 4: Electron Transport ChainChain

• Happens on inner membrane of mitochondria

• Occurs only if oxygen is present– Oxygen is final electron acceptor– If no oxygen is present reaction stops


• Electrons come from NADH and FADH molecules which gathered them during glycolysis and CTA

• Energy from electrons is used to add Pi to ADP, forming ATP

• At the end of the chain, oxygen accepts the electrons and combines with 2 H+ ions to form water


• Step 1: Glycolysis





Glycolysis 2 ATP

Citric acid cycle 2

Electron transport chain **32

ATP

ATP**Makes ATP from electrons carried to it from the first 3 steps


Makes 36 ATP

Anaerobic RespirationAnaerobic Respiration

• Pyruvic acid molecules are still formed through glycolysis

• Broken down differently:– No ATP is produced after glycolysis– NAD+ is regenerated so glycolysis can

continue

Anaerobic RespirationAnaerobic Respiration

• 2 types:– Lactic acid fermentation– Alcoholic fermentation

Lactic Acid FermentationLactic Acid Fermentation

• Lactic acid is end product

• Occurs when muscles require energy at a faster rate than it can be supplied through aerobic respiration

• Causes burning sensation in muscles

Lactic Acid FermentationLactic Acid Fermentation

Glycolysis

Alcoholic FermentationAlcoholic Fermentation

• Ethyl alcohol and CO2 are end products

• Occurs in organisms that live in environments lacking oxygen

• Source of bubbles in beer and champagne and causes baking bread to rise

Alcoholic FermentationAlcoholic Fermentation

Glycolysis

2 Ethanol

2 CO2

the big intro

Documents

energy of sunlight

light reactionsdark

energy storage molecules

energy needs

energy currency2

trapped energy

chemical energy of sugars

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