WHAT IS ENERGY?WHERE DO WE GET IT?

CELLULAR ENERGYKEY CONCEPT: ATP IS THE

USABLE SOURCE OF ENERGY IN ALL CELLS.

• Energy is the ability to do work.

• Thermodynamics is the study of the flow and transformation of energy

• All living things need energy.

HOW ORGANISMS OBTAIN ENERGY

• The main source of energy in living things is glucose, (sugar).

• How do living things get glucose?

• Autotrophs: ____________________

• Heterotrophs: ___________________

HOW ORGANISMS OBTAIN ENERGY

• Metabolism: all of the chemical reactions in a cell

• Photosynthesis: light energy from the sun is converted to chemical energy for use in the cell

• Cellular respiration: organic molecules (like sugars, proteins, lipids) are broken down to release energy for use in the cell

• Glucose is only storage for energy in cells.

• What molecule do cells actually use to power cellular processes?

ATP

• The energy unit of a cell is ATP:

• Adenosine

• Tri

• Phosphate

• When the last phosphate bond is broken, energy is released.

• This energy fuels a cell’s reactions.

ADP

• When ATP is broken down, the molecule becomes

• Adenosine

• Di

• Phosphate

• Energy has to be added from an outside source to reform ATP.

SOURCES OF ENERGY

• Sugar, or glucose, is broken down to turn ADP into ATP.

• Other molecules can provide this energy as well.

• Sugar is either eaten or produced in photosynthesis.

PHOTOSYNTHESISPROCESS THAT PRODUCES SUGARS THAT STORE CHEMICAL ENERGY

PHOTOSYNTHETIC ORGANISMS = PRODUCERS

• Photosynthesis captures energy from the sunlight and uses that energy to make sugars that store chemical energy

PHOTOSYNTHESIS CONVERTS SOLAR ENERGY INTO CHEMICAL ENERGY.

6 H2O + 6 CO2 6 O2 + C6H1 2O6

Plants use the energy from sunlight to convert

carbon dioxide and water into sugar and oxygen

Reactants Productslight

PHOTOSYNTHESIS OCCURS IN 2 PHASES

1.Light-dependent reactions

2.Light-independent reactions, AKA Calvin Cycle

PHASE 1:• Light Reactions

• Absorption of sunlight is the first step

• Chlorophyll, a molecule in chloroplasts, absorbs sunlight

• Chlorophyll is found in the thylakoid membranes of the chloroplasts

• Light dependent reactions occur in the thylakoids

chloroplast

leaf cell

leaf

PHOTOSYNTHESIS IN PLANTS OCCURS IN CHLOROPLASTS.

Stroma

Granum

Thylakoid

Contains

chlorophyll

Stack of

thylakoids

Fluid outside

the thylakoid

1. LIGHT-DEPENDENT REACTIONS

1. Light strikes a chlorophyll molecule in the thylakoid membrane, exciting electrons

2. That energy also causes a water molecule to split, releasing an electron

3. Oxygen from water is released as waste

Thylakoid

1. LIGHT-DEPENDENT REACTIONS

• Water and energy from light are used to produce ATP and NADPH.• ATP and NADPH molecules transfer energy.

• These reactions also produce oxygen gas.

Chloroplast

Light

O2

Light-Dependent Reactions

NADPHATP

Chloroplast

H20

2. LIGHT-INDEPENDENT REACTIONS

• The light-independent reactions are also called the Calvin cycle and occur in the stroma of the chloroplasts.

• The calvin cycle uses CO2

and the energy from the light-dependent reactions to build sugar.

Stroma

2. LIGHT-INDEPENDENT REACTIONS

• During the Calvin cycle, CO2 and the ATP and NADPHfrom the light-dependent reactions are used to build glucose.

• Glucose is a high-energy sugar that can be stored for a long time.

Light

O2Glucose

CO2

Light-Dependent Reactions

CalvinCycle

NADPH

ATP

ADP + P

NADP+

Chloroplast

H20

Photosynthesis Equation

H20

O2

Light-

dependent

ReactionsATP

NADPH

Calvin

Cycle

Glucose

CO2

6 H2O + 6 CO2

Reactants Productslight

6 O2 + C6H1 2O6

ATP AND NADPH

Light Energy

Chloroplast

CO2 + H2O Sugars + O2Go to

Section:

THE EQUATION FOR THE OVERALL PROCESS IS:6CO2 + 6H2O C6H12O6 + 6O2

• Glucose is not the only sugar that can be formed by photosynthesis.

• Other simple sugars (like fructose) can also be made.

• Plants and other photosynthetic organisms use the simple sugars for energy and to build more complex carbohydrates like starches and cellulose, which it needs for growth and development.

FACTORS AFFECTING PHOTOSYNTHESIS

• Water• Required for photosynthesis.

• Temperature• Enzymes can only function between 0oC and

35oC.

• Light intensity• Increasing the light intensity will increase the

rate of photosynthesis to a certain point

WHY ARE PLANTS GREEN?

• Sunlight is a spectrum of different colors of light.

• Chlorophyll absorbs red and blue light from the sun and reflects green light.

• Because light is a form of energy, any compound that absorbs light also absorbs the energy from that light.

CELLULAR RESPIRATIONTHE CHEMICAL BREAKDOWN OF GLUCOSE

ENERGY & FOOD

• Foods contain usable energy stored in organic compounds such as proteins, carbohydrates, and fats.

• After we eat, or plants go through photosynthesis, cells break down the complex organic compounds in our food into simpler molecules.

• Some of the energy released during this process is used to make ATP.

ATP• Cells use a molecule called ATP to store

energy.

• ATP= Adenosine Triphosphate

high energy

bondThe 3rd phosphate is attached by a

When that bond is broken,

energy is released for use by

the cell.

From food to energy…

Stored

Energy

Our bodies break down

the food we eat and plant

cells break down glucose

to make ATP.

Plant and animal cells

break ATP into ADP

when they need energy.

Released

Energy

From food to energy• How is ATP made?

• Cellular respiration makes ATP by

breaking down sugars.

• The process that releases energy by breaking

down food molecules in the presence of

oxygen is called cellular respiration.

Cellular respiration and breathing

• Cellular respiration and breathing are related, but not the same.

• Breathing in lungs

– Intake of O2

– Release of CO2

• Cellular respiration

– O2 diffuses into cells

• O2 used to burn food fuel to make ATP

– CO2 diffuses out of cells

Cellular Respiration

• BOTH plants & animals breakdown food

– For cells to obtain energy from the glucose, it

must be broken down.

– Cellular respiration releases energy from

glucose to make ATP.

• ATP is available energy for cells to use

• Reverse of photosynthesis!

– Instead of making glucose, it is broken down!

The Cellular Respiration Equation

KEY CONCEPT

The overall process of cellular respiration

converts sugar into ATP using oxygen.

Quick Review

• What is the photosynthesis equation?

• What is the cellular respiration equation?

Energy + 6CO2 + 6H2O C6H12O6 + 6O2

6O2 + C6H12O6 6CO2 + 6H2O + Energy

ATP= Adenosine Triphosphate

Quick Review

• How do cells store energy?

How does cellular respiration work?

• 6O2 + C6H12O6 6CO2 + 6H2O + Energy

• In the presence of oxygen, glucose is

broken down and energy is released to

make ATP.

• Three main steps of cellular respiration

1. Glycolysis

2. The Krebs cycle

3. The Electron Transport Chain

1. Glycolysis• Glycolysis is the breakdown of

one molecule of glucose into two

molecules of pyruvic acid.

1glucose 2 pyruvic acid

Glycolysis does NOT need any

oxygen.

Glycolysis occurs in the cytoplasm of

the cell.

1. Glycolysis

• Requires 2 ATPs to get started

• Produces 4 ATPs– Net gain of 2 ATP’s

2 Pyruvic acid

1. Glycolysis• Produces 2 NADH molecules

– NADH is an electron carrier.

– NADH holds high-energy electrons until they

can be transferred to other molecules.

To the electron

transport chain

Cellular Respiration Products

1. Glycolysis

• 2 ATP

• 2 NADH

Quick Review

• Where does glycolysis occur in the cell?

Glycolysis occurs in the cytoplasm of the cell• What is produced during glycolysis?

1 glucose 2 pyruvic acid

2. The Krebs cycle

• At the end of glycolysis, about 90% of

the energy in glucose is still unused.

– To get the rest of the energy, the cell

uses oxygen to break down pyruvic

acid into in CO2 during the Kreb’s

cycle.

2. The Krebs cycle• Pyruvic acid enters the mitochondria.

• The Krebs cycle is a series of reactions

that converts pyruvic acid into CO2

– Each turn of the Krebs cycle creates:

• 3 CO2

• 1 ATP

• 4 NADH

• 1 FADH2

Electron Carriers

2. The Krebs cycle

Citric Acid

ProductionMitochondrion

The products after 1 spin:3 CO2

1 ATP 4 NADH1 FADH2The Krebs cycle spins twice for each molecule of glucose!!!

The products from 1 glucose:6 CO2

2 ATP 8 NADH2 FADH2

Cellular Respiration Products

1. Glycolysis

• 2 ATP

• 2 NADH

2. The Krebs cycle

• 6 CO2

• 2 ATP

• 8 NADH

• 2 FADH2

Quick Review

• Where does the Kreb’s cycle occur in the

cell?

Pyruvic acid enters the mitochondria

How many times does the Kreb’s cycle

spin for each molecule of glucose?

The Krebs cycle spins twice for each molecule of glucose!!!

3. The Electron Transport Chain• Electron carriers drop off their electrons at the ETC.

– 2 NADH from glycolysis

– 8 NADH from Kreb’s Cycle

– 2 FADH2 from Kreb’s Cycle

• The ETC passes the electrons along a series of proteins until they reach an oxygen molecule at the end of the chain.

– Oxygen and hydrogen combine to produce H20

• The energy in the electrons is used to convert ADP into ATP.

– 32 ATP molecules are made in the ETC

Section 9-2

Electron Transport

Hydrogen Ion Movement

ATP Production

ATP synthase

Channel

Inner Membrane

Matrix

Intermembrane Space

Go to

Section:

Mitochondrion

3. The Electron Transport Chain

Cellular Respiration Products

1. Glycolysis

• 2 ATP

• 2 NADH

2. The Krebs cycle

• 6 CO2

• 2 ATP

• 8 NADH

• 2 FADH2

3. The Electron Transport Chain

• 32 ATP

ATP Totals:

2ATP

2ATP

+ 32 ATP

36 ATP

Quick Review

• Where does the ETC occur in the cell?

The mitochondria

Quick Review

• What are the three steps of cellular

respiration?

1. Glycolysis2. The Krebs cycle3. The Electron Transport Chain

• What stages need oxygen?

Cellular Respiration

(C6H1206)

+

(02)

(CO2)

+

(H2O)

Go to

Section:

2 NADH 8 NADH2 FADH2

6O2 + C6H12O6 6CO2 + 6H2O + 36 ATP

Cellular Respiration

Glucose

(C6H1206)

+

Oxygen

(02)

GlycolysisKrebs

Cycle

Electron

Transport

Chain

Carbon

Dioxide

(CO2)

+

Water

(H2O)

Go to

Section:

2 ATP 2 ATP 32 ATP

2 NADH 8 NADH2 FADH2

6O2 + C6H12O6 6CO2 + 6H2O + 36 ATP

Cellular Respiration and Oxygen

• Cellular respiration requires oxygen to

create ATP.

• What happens if there is no oxygen?

Fermentation

Types of Reactions

• There are two types of reactions that can

take place during the break down of glucose.

– Aerobic Respiration

• Cellular Respiration

• Requires oxygen

– Anaerobic Respiration

• Fermentation

• In the absence of oxygen

Aerobic Respiration:

GlycolysisKrebs CycleElectron Transport Chain

Anaerobic Respiration:

GlycolysisFermentation

How do we know which reaction

will occur?• The type of reaction that occurs depends on

– the organism.

– the type of cell.

– the availability of oxygen (O2).

The Availability of Oxygen

• When O2 is available, then the

organism/cell will use an AEROBIC

pathway.

– An “aerobic” reaction requires oxygen

• When O2 is not available, then the

organism/cell will use an ANAEROBIC

pathway.

– Anaerobic reactions do not require oxygen.

Aerobic or Anaerobic?

• In either case, the break down of glucose

always begins with glycolysis.

– The main purpose of glycolysis is to make

pyruvic acid.

• Pyruvic acid is essential for fermentation

(the anaerobic path) AND cellular

respiration (the aerobic path).

glucose pyruvic acid

Glycolysis glucose pyruvic acid

• Both fermentation and cellular respiration

begin with glycolysis.

– If O2 is available, the pyruvic acid enters the

mitochondria and begins the Krebs cycle.

– If O2 is not available, the pyruvic acid goes

through fermentation in the cytoplasm to

produce energy for the cell.

Aerobic or Anaerobic?

Glucose

Pyruvic Acid

1. Glycolysis

O2 No O2

Cellular Respiration Fermentation

Aerobic Aneorbic

2. The Krebs cycle

+

3. Electron Transport Chain

2. Alcoholic

or

2. Lactic Acid

Fermentation

• Fermentation can produce energy for the

cell without oxygen.

• There are two types of fermentation:

– Alcoholic fermentation

– Lactic Acid fermentation

Alcoholic Fermentation

• Alcoholic fermentation produces alcohol.

– Pyruvic acid from glycolysis is converted into

ethyl alcohol, CO2, and NAD.

• This occurs in some plants and

unicellular organisms.

Bread rises because of alcoholic fermentation!!!

Lactic Acid Fermentation

• Lactic acid fermentation produces lactic

acid.

– Pyruvic acid from glycolysis is converted into

lactic acid and NAD.

• This occurs in muscle cells.

– The build up of lactic acid causes muscles to

cramp.

Fermentation

• During fermentation, ATP is not produced.

– Fermentation allows glycolysis to continue.

• Glycolysis will produce 2 ATP from each

molecule of glucose.

Aerobic vs. Anaerobic

Aerobic

Anaerobic

How does the body produce ATP

during different stages of exercise?

• 200 m sprint

– ATP already stored in

cells can fuel a few

seconds of intense

activity

– Lactic acid

fermentation supplies

ATP up to about 90

seconds

– Oxygen is the only

way to get rid of lactic

acid

• Marathon– Exercise lasting longer

than 90 seconds, cell

respiration is the only way

to generate ATP

– Pacing!

– Stored carbohydrates in

body tissues can supply

energy for 15 minutes of

cell respiration.

– After that, the body starts to

break down other stored

molecules, like fats.