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Chapter 4 Energy and Life:

• 4.1 What is energy?

• 4.2 Energy flow

• 4.3 Sunlight is used to produce sugars

• 4.4 Photosynthesis has 2 linked stages

• 4.5 Light reactions: a closer look

• 4.6 Calvin cycle: a closer look

• 4.7 Cellular respiration overview

• 4.8 Cellular respiration: a closer look

• 4.9 Fermentation

• 4.10 Cellular respiration as a hub of metabolism

© 2017 Pearson Education, Inc.

4.1 Opening Questions: What is ENERGY?

• How do you make it through your day?

• How does a plant eat?

• What powers a car?

Chapter Table of Contents© 2017 Pearson Education, Inc.

4.1 Living things use energy to power life.

• All living things

need energy to

survive.

• But how do we

define energy?

Energy is defined

as the capacity to

do work.


4.1 Energy is converted from one form to

another.

• Does the slider at

the top of the slide

contain energy?

Potential energy is

the energy an object

has due to its

location or structure.


4.1 Energy is converted from one form to

another.

• What happens

when the slider

goes down the

slide?

Kinetic energy is the

energy of motion.


4.1 Potential energy is stored in the bonds

that hold atoms together into molecules.

• In cells, ATP is a common energy currency

molecule.

• Breaking a bond in ATP releases energy

that can be used to drive other processes.


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4.1 Conservation of energy

• Energy can be converted but cannot be

created or destroyed.

Chemical energy in lizard’s

food is stored and later

converted to kinetic energy

Solar energy

warms the lizard

Heat energy

dissipates


4.1 Heat is a by-product of energy

conversion.

• After doing 100

jumping jacks,

would you feel

warm or cold?

At each conversion

some energy is lost to

living things in the form

of heat.


4.1 Living things must work to counter

entropy.

• With each energy conversion heat is released, so the disorder in a system increases.

• Entropy is the amount of disorder in a

system.

Why don’t living systems, like ecosystems or

organisms, fall into complete disorder?


4.2 Opening Questions: What is the source

of ENERGY for nearly all life?

• How do plants and

animals get energy?

• What do plants and

animals have in

common in terms of

energy acquisition?

• How do plants and

animals differ?


4.2 Opening Questions: A thought

experiment

What would happen if the sun went out?

– How long could humans survive?

– Explain your ideas in a story.


4.2 Energy FLOWS through ecosystems.

• Solar energy is inputted daily.

• Energy therefore flows through living

systems.

Life on

Earth is

powered

by the sun.


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4.2 Producers and consumers:

Producers can absorb the sun’s energy

and convert it to chemical energy. They

can make their own food!


4.2 Producers capture solar energy and

convert it to chemical energy (sugars).

Energy is stored

in the bonds of

sugar molecule.

CO2 + H2O SUGAR + O2

Chemical

Energy

Solar

Energyconverted to

This is the process of PHOTOSYNTHESIS.

Overall inputs and output of photosynthesis


4.2 Sugar production is the goal of

photosynthesis.

• Photosynthesis takes

place inside the cells of

plants and algae in

organelles called

chloroplasts.

• Plants and algae

produce oxygen gas

(O2) as a by-product.

Interesting Fact: The Earth’s atmosphere was low

in O2 prior to the evolution of photosynthesis.


4.2 Producers and consumers:

Consumers obtain energy by eating producers.


4.2 Both producers and consumers must

use cellular respiration.

• Photosynthesis converts solar energy into

chemical energy.

• However, both producers and consumers

are only able to release chemical energy

through the process of cellular

respiration.


4.2 Cellular respiration allows plants and

animals to power life.

• The potential energy in

the chemical bonds of

sugar is converted to

chemical energy.

• The kinetic energy can

now be used for work.

What kind of work

might a plant or animal

need to do?


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4.3 Opening Question: Why is the grass

green?

• Why do most of the

plants we see everyday

look green to us?


4.3 Where does photosynthesis take place?

• Most photosynthesis

reactions occur

inside plant cell

organelles called

chloroplasts.

Photosynthesis is the process that provides

food to nearly all life on Earth!


4.3 Photosynthesis: a visual overview

Photosynthesis

Product: C6H12O6

By-product: O2


Photosynthesis Inputs:

H2O from ground and

CO2 from the air

4.3 The chloroplast: a closer look

• Inside the

chloroplast there is

an extensive

framework of

membranes.

• These facilitate the

reactions of

photosynthesis.


4.3 So why are plants green?

• Chlorophyll is the

primary pigment

(light-absorbing

molecule) in

chloroplasts.

Light in the blue/violet and orange/red ranges is

absorbed.

Light in the green/yellow range is reflected.


4.3 Plants look green because chlorophyll

reflects green light.

• The leaves of many deciduous trees change color in the fall.

Can you think of

an explanation?


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4.4 Opening Question: Where does the

mass of a plant come from?

• Tiny acorns grow

into huge oak trees.

• Where does all the

mass of the adult

tree come from?


4.4 Photosynthesis: overall reaction

6CO2 + 6H2O C6H12O6 + 6O2

The chemical inputs/output for

photosynthesis are:


4.4 Photosynthesis occurs in two linked

stages.

1. The light reactions capture sunlight and

store it in high-energy molecules.

2. The Calvin cycle uses those high-

energy molecules to produce sugar.

Photosynthesis captures the energy in sunlight

and stores it in the form of sugar molecules.


4.4 Stage 1: The LIGHT REACTIONS:

capturing energy

• Energy from sunlight

is absorbed by

chlorophyll.

• H2O is split,

producing O2.

• High-energy

molecules of ATP

and NADPH are

produced.

Takes place in the thylakoid


4.4 Light reactions and Calvin cycle are

linked by energy and electron shuttles.

LIGHT

REACTIONS CALVIN

CYCLE

NADPH

NADP+

NADPH is a molecule that shuttles electrons.

ATP is a molecule that shuttles energy.

ATP

ADP


4.4 Stage 2: The Calvin cycle: making sugar

• High-energy

products from light

reactions and CO2

are used to make

sugar (C6H12O6).

Calvin cycle takes place in the STROMA.

Where does the plant

get CO2?


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4.4 Review Question: Where does the mass

of a plant come from?

Revise your

answer using the

chemical equation

for photosynthesis.


4.5 Opening Question: Where does the O2

produced in photosynthesis come from?

• Take a deep breath and thank a plant.


4.5 Photosynthesis proceeds in two stages:

overview

1. Light reactions

– Convert light energy to chemical energy

2. Calvin cycle

– Uses high-energy molecules (ATP, NADH)

to produce sugars

Inside a leaf both

stages of

photosynthesis

are occurring.


4.5 A closer look at the light reactions:

capturing sunlight as chemical energy

• The light reactions occur in the thykaloid

membranes of the chloroplast.

Pigment molecules

capture the energy

from sunlight.

#1 pigment

molecule is

chlorophyll.



major players and products

Light System Players:

• Sunlight

• Water

– Splitting of H2O

supplies electrons

• Chlorophyll

• ATP and ADP

molecules

• NAPDH and NAPD

molecules

Light System Products:

• Energy

– Held in ATP

• Electrons

– Shuttled in NADH

• O2 as a by-product

ATP and NAPDH move

to the Calvin cycle.




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4.5 What happens to the water molecule?

• Water (H2O) is used during the light

reaction as a source of electrons.

• What remains of the water molecule

(oxygen) is released and exits the leaf.


4.6 Opening Questions: Plants at work

• How are a carrot and

a piece of wood

alike?

• How are they

different?

• How did a plant

“make” a carrot or a

piece of wood?


4.6 A closer look at the Calvin cycle:

making sugars

• Calvin cycle uses high-energy molecules

from the light reactions to construct

sugars.

• The plant can use sugars in a variety of

ways.

Reminder: Photosynthesis is made up of two parts:

light reaction and Calvin cycle.


4.6 Inputs to the Calvin cycle:


4.6 Outputs from the Calvin cycle:

• A 3-carbon sugar (G3P) is the output from the Calvin cycle.

• Plants use G3P to generate glucose.

• Glucose can be used for energy right away, or it can be stored.


4.6 Plants are built of sugars!

• Plants store glucose in two ways.

• Both ways represent many glucose

molecules stitched together.

Starch Cellulose


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4.7 Opening Questions: Part 1

• Everybody stand up.

• Shake your hands above your head!

• Dance party!

Congratulations: You just

burned about 6 Calories.


4.7 Opening Questions: Hungry?

• What does burning Calories really mean?

• Why do we get hungry?

• Why do we need to breathe?


4.7 In CELLULAR RESPIRATION, oxygen is

used to harvest the energy stored in sugar.

• Cellular respiration

releases the

chemical energy

stored in sugars.

ALL organisms – both

producers and

consumers – use

cellular respiration!


4.7 Aerobic respiration:

• Aerobic respiration

requires oxygen (O2).

• It takes place inside

the mitochondria.


happens in both

producers and

consumers!


4.7 The ins and outs of aerobic respiration


4.7 The ins and outs of aerobic respiration

1. O2 travels from lungs to the

mitochondria.

2. Food travels from digestive system to

the mitochondria.

3. CO2 leaves the cell and is expelled

from the lungs.


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4.7 Three body systems play a role in

cellular respiration.


4.7 Energy stored in ATP

• Cellular respiration produces an energy-

carrying molecule called ATP.


4.7 Kilocalories (kcal)

• A Calorie is the

amount of

chemical energy

stored in food.

• A nutrition label is

really showing you

kilocalories (kcal),

or thousands of

Calories.


4.7 Kilocalories (kcal)

• A Calorie also can

describe the

amount of energy

burned.

• Weight gain/loss is

result of Calories in

versus out.

How long would you have to dance to

burn off a candy bar? An orange?


4.8 Opening Questions: Toxic Spy Tales

Could such a pill really exist?

How could a poison work so fast?

In old spy movies, a

captured undercover agent,

rather than risk spilling

secrets, would swallow a

hidden pill, which resulted in

instant death. Very dramatic!


4.8 Cellular respiration is how life gets

energy to power work.

• Cellular respiration uses O2 to “burn”

sugar (glucose).

• Energy is then used to generate ATP.

• By-products are CO2 and H2O.

Both plants and animals depend

on cellular respiration 24 hours a

day, every second, in every cell.


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4.8 Cellular respiration overview:


4.8 Cellular respiration: overall reaction

C6H12O6 + 6O2 6CO2 + 6H2O

How does the overall equation for cellular

respiration compare with photosynthesis?

The chemical inputs/output

for cellular respiration are:


4.8 Study tip:

The chemical inputs for cellular respiration and

photosynthesis are reciprocal!

Cellular respiration Chemical Energy ATP Energy

Photosynthesis Light Energy Chemical Energy


6CO2 + 6H2O C6H12O6 + 6O2

6CO2 + 6H2O C6H12O6 + 6O2

4.8 Cellular respiration has three stages.

1. Glycolysis

2. Citric acid cycle

3. Electron transport chain


4.8 Glycolysis:

• Takes place in

cytoplasm

• Splits glucose into

2 pyruvic acids

• Small amount of

ATP produced


4.8 Citric acid cycle:

• Takes place in the

mitochondrial fluid

• Uses O2

• Pyruvic acid

broken to CO2

• High-energy

electrons produced

• Small amount of

ATP produced


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4.8 Electron transport chain:

• Takes place in the inner membranes of

mitochondria

• High-energy electrons move through chain

• Electrons

combine with

O2 to form H2O

• Lots of ATP

produced!


4.8 Test your understanding: The toxic tale

of the spy movie

• What would happen to your ATP

production?

• How long could your cells survive?

The spy pills were

made of potassium

cyanide, which

interrupts the electron

transport chain.


4.9 Opening Questions: What makes your

beer carbonated?

• Where do the

bubbles come from

in beer?

• What about the

alcohol?

• Explain.


4.9 In fermentation, energy is harvested

from sugar without oxygen.


• Anaerobic respiration


4.9 Fermentation is anaerobic.

• Fermentation harvests

the energy from

glucose without O2.

• Only a small bit of ATP

is produced.O2

Fermentation produces much less

ATP than aerobic respiration!


4.9 Lactic acid fermentation in muscles

• When cells can’t get O2, lactic acid

fermentation is an “emergency” mode.

Why can’t muscle cells run for long on fermentation?


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4.9 Lactic acid fermentation by bacteria

• Unlike muscle cells, some

bacteria can survive on

fermentation.

• Humans have domesticated

many strains.

Why does yogurt

have a “tangy” taste?


4.9 Alcohol fermentation by yeast

• Yeast will ferment sugars

in anaerobic environments.

• This produces CO2 and

alcohol (ethanol).

CO2 is a gas!

So what happens when

CO2 is in a liquid?


4.10 Opening Question: Sugar rush

• If cellular respiration

“burns” sugars, can

we get energy from

other foods?


4.10 Cellular respiration is a central hub

of many of life’s metabolic processes.

• Many types of molecules can feed into

cellular respiration.

• In addition to sugar, we can process

– Fats

– Carbohydrates

– Proteins

This means we can generate ATP

from many different food inputs.


4.10 All food provides energy.


4.10 Energy use by living things.

• Your metabolism is the sum total of all the chemical reactions that occur in your body.

ATP produced by cellular respiration powers nearly all of life’s processes.


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