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Energy In A Cell
Photosynthesis
Cellular
Respiration
The Need for Energy
• 1. All cells use energy for life processes.
• 2. Where do cells get energy? Food
• 3. What is the original energy source for
most organisms? Sun
– Autotrophs-make their own food from the
sun’s energy. Ex: Plants
– Heterotrophs-organisms unable to make their
own food; they depend on other organisms for
a source of food. Ex: animals, fungi
Autotroph
Sun
Heterotroph
II. Thermodynamics
A. The study of energy (heat dynamics).
B. There are two thermodynamic laws that govern
all the activities of our universe.
1. First law of thermodynamics:
a. energy cannot be created or
destroyed
b. It can be converted to various forms
c. Generally, biological energy is lost to the
biosphere in the form of heat.
• 2. Second law of thermodynamics:
• a. Disorder in the universe is continuously increasing.
• b. Any process involving the use of energy looses some
energy to heat (friction) and is no longer available for
work.
• c. Energy becomes "disorganized." The term for this
disorganization is entropy.
• 1. Entropy in the universe is continually increasing.
• 2. Eventually all energy will be random and useless-several billion years in the future.
• 3. Because of the second law, no process requiring
energy is ever 100% efficient.
• i. Cellular energy is about 55% efficient.
• ii. The gasoline engine is about 17% efficient.
• iii. Perpetual motion machines are impossible.
C. The use of energy is either exergonic or
endergonic.
1. Exergonic--energy releasing.
2. Endergonic--energy consuming.
• Energy for Life Processes
– There are 2 stages in the passage of energy from
the sun to the cells:
• Stage 1: Photosynthesis
» The process of plants
taking CO2 from the
atmosphere along with
water from the soil to
produce O2 gas and
glucose
» This process converts
sunlight into chemical
energy.
Energy for Life Process Cont.
• Stage 2 Cellular Respiration
– The process of taking oxygen gas from the atmosphere and
glucose from food molecules to produce CO2, H2O, and energy in
the form ATP.
– **This process occurs in the mitochondria and the cytoplasm of
cells.**
– This process does not occur in prokaryotes, since they do not
have mitochondria.
Cellular
Respiration takes
in food to give us
energy!! This
player really
needed ENERGY!
State Test Question
• Many cell processes cannot directly
use the energy from food. Which
organelles covert food energy to a
form that can be used by the cell?
a)
b)
c)
d)
Endoplasmic reticulum
Golgi body
Ribosomes
Mitochondria
Energy For Life Processes Cont.
– Most organisms depend on cellular respiration
and photosynthesis to provide energy directly
or indirectly.
– The alternation of photosynthesis and cellular
respiration results in the continuous recycling
of CO2 and O2.
• ATP (Adenosine Triphosphate)- Stores Energy
– ATP is found in all living things, and it is able to
absorb energy and release it when needed by a cell.
– There are 3 parts of the ATP molecule:
1. Adenine-a nitrogen containing molecule
2. Ribose-a 5-carbon sugar
3. 3 phosphate groups
*The adenine combines with ribose to form adenosine.*
State Test Question
Energy from food sources drives the
production of ATP. Why is this molecule
essential in all living cells?
a) It is the main energy source for most
cellular processes.
b) It is the basis of DNA.
c) It is a structural component found in cell
walls.
d) It is required for osmosis and diffusion.
– Some related terms:
• AMP (Adenosine Monophosphate)- identical to ATP
except it has 1 phosphate group.
• ADP (Adenosine Diphosphate)- identical to ATP
except it has 2 phosphate groups
• ATP (Adenosine Triphosphate)- The bond holding
together the last 2 phosphates is a high-energy
bond. When the bond is broken, a tremendous
amount of energy is released for use by the cell.
After the bond is broken, the remaining molecule
holds only two phosphate groups. It is now called
ADP. ADP can absorb energy, use this energy to add
another phosphate, and become ATP again. ATP
allows the cell to use its energy a little at a time.
BOOM!
A – P ~ P~P
A–P~P~P
High Energy Bond
ATP
*Energy is stored in high
energy bonds
Note: When a bond is broken,
energy is released. When cells
break down food molecules, some
of the energy in the molecules is
released as heat. Much of the
remaining energy is stored
temporarily in molecules of ATP.
A – P ~ + Energy
ADP + Energy
• D. To keep on working, the cell must regenerate its
supply of ATP--an endergonic process known as
phosphorylation.
• E. The oxygen bonds are easily broken by water
(hydrolysis).
• F. The reaction is endergonic--energy is required.
Most ATP is manufactured in the mitochondria.
• G. ATP is formed from ADP when radiant energy is
trapped by chloroplasts or when nutrients are oxidized.
This energy intake is necessary for all life--plant or
animal.
• H. The ATP molecule is ephemeral--the energy is
expended almost as soon as it is created.
• I. To put the process in perspective, every second--in
every cell--about 10 million molecules of ATP are
created and expended.
State Test Question
ATP is continuously regenerated from
ADP when energy released by cellular
respiration is used in an endergonic
reaction.
Energy stored in food is released when—
• chemical bonds are broken.
• atomic nuclei are split.
• elements combine.
• electrons are produced.
State Test Question
a)
b)
c)
d)
ATP is called the energy currency for
cells because it—
is a constantly renewing source of
energy.
is the ultimate source of energy on Earth.
is the exchange molecule for energy
transfers.
provides energy for exergonic reactions.
State Test Question
a)
b)
c)
d)
The process of breaking down ATP to
ADP is termed—
fermentation.
an exergonic reaction.
an endergonic reaction.
a synthesis reaction.
State Test Question
a)
b)
c)
d)
Energy for most cellular processes is
obtained by breaking a bond between
which two components of ATP?
Phosphate and nitrogen
Phosphate and carbon
Phosphate and adenosine
Phosphate and phosphate
State Test Question
a)
b)
c)
d)
Which of the following is needed to
transfer and release energy?
Calcium
Phosphate
Nitrate
Potassium
State Test Question
a)
b)
c)
d)
Energy stored in food is released
when—
chemical bonds are broken.
atomic nuclei are split.
elements combine.
electrons are produced.
• Photosynthesis: Photosynthesis provides
energy for almost all life.
– Equation:
• 6CO2 + 6H2O+ sunlight
C6H12O6 + 6O2
– Photosynthesis Occurs in 2 Phases:
• Phase 1 is the light reaction
• Phase 2 is the dark reaction (The Calvin Cycle)
• Phase 1. The light reaction:
– Stage 1: Energy is captured from sunlight.
• Pigment molecules in the thylakoids of chloroplasts absorb light
energy, energy transferred to electrons in the chlorophyll
• Stage 2: Light energy is converted to chemical energy
• Excited electrons that leave chlorophyll molecules are used to
produce new molecules that temporarily store chemical energy,
including ATP. AN excited electron jumps to a nearby molecule in
the thylakoid membrane
• Then the electron is passed through a series of molecules along the
thylakoid membrane like a ball being passed down a line of people.
The series of molecules through which excited electrons are passed
along a thylakoid membrane are called electron transport chains.
• While one electron transport chain provides energy used to make
ATP, a second electron transport chain provides energy used to
make NADPH
State Test Question
The light-dependent reactions of
photosynthesis use the Sun’s
energy to produce—
a) glucose.
b) chemical energy.
c) carbon dioxide.
d) water.
• The light reaction (Stage 1 and 2) produces the
O2 gas and the energy ATP+NADPH for the
Dark reaction-Calvin cycle.
State Test Question
In the light-dependent phase of
photosynthesis, energy from the Sun is
used to drive the production of which of
the following molecules?
a) Proteins
b) Carbohydrates
c) ATP
d) ADP
State Test Question
The process of photosynthesis produces
sugar, water and—
a) hydrogen gas.
b) nitrogen dioxide gas.
c) carbon dioxide gas.
d) oxygen gas.
State Test Question
The glucose produced during
photosynthesis is an example of a—
a) lipid.
b) monosaccharide.
c) protein.
d) nucleic acid.
State Test Quesiton
When excess sugar is produced in a plant,
the plant will—
a) release the sugar into the soil.
b) convert the sugar into minerals.
c) store the sugar by forming larger
molecules.
d) burn the leaves of the plant as it releases
energy.
State Test Question
Because most plants are able to undergo
photosynthesis, they do NOT—
a) require carbon dioxide.
b) store energy for later use.
c) undergo cellular respiration.
d) depend on other organisms for energy.
State Test Question
Photosynthesis begins when sunlight
causes chlorophyll molecules to—
a) produce sugars.
b) absorb carbon dioxide.
c) emit oxygen.
d) emit electrons.
State Test Question
In photosynthesis, light energy from the
Sun is stored in the bonds of—
a) lipids.
b) carbohydrates.
c) proteins.
d) enzymes.
State Test Qustion
What are the raw materials for
photosynthesis?
a) CO2 and H2O
b) H2O and O2
c) C6H12O6 and O2
d) C6H12O6 and H2O
• Phase 2: The Dark Reaction: Calvin Cycle
– CO2 enters the leaf through hundreds of small
pores.
– A three-carbon sugars is used to make organic
compounds-including carbohydrates such as
sucrose and starch in which energy is stored for
later use. So, this excess
sugar is stored for use later.
– ***The dark reaction-Calvin
cycle produces the organic
compound C6H12O6-glucose
State Test Question
What are the main products of
photosynthesis?
a) Glucose and oxygen
b) Glucose and water
c) Carbon dioxide and water
d) Water and ATP
State Test Question
During photosynthesis, energy from the
sun is trapped in—
a) chemical bonds.
b) the nuclei of atoms.
c) enzymes.
d) Golgi bodies.
Cellular Respiration
– The process of taking O2 gas from the atmosphere
and glucose from food molecules to produce CO2,
H2O and energy in the form of ATP. Cellular
Respiration produces ATP. Food molecule are
broken down to release the energy in their bonds.
Glucose is the energy source for cellular
respiration. Respiration occurs in the cytoplasm;
glycolysis) in the mitochondria (Citric Acid
Cycle/ Krebs’ Cycle.)
Takes in
Oxygen
Takes in Glucose
from food
molecules
Gives off
Carbon
Dioxide
Gives off
water
Releases
energy in
the from of
ATP
Cellular Respiration
• Metabolic process that require oxygen are
called aerobic.
• Metabolic process that do NOT require oxygen
are called anaerobic meaning “without air”.
• A. Equation: C6H12O6 + 6O2 6CO2 + 6H2O + ATP
Cellular Respiration
Aerobic respiration =
oxygen
Sore muscles = anaerobic
respiration
State Test Question
Most organisms exhibit aerobic respiration
which requires—
a) oxygen.
b) carbon.
c) nitrogen.
d) hydrogen.
State Test Question
In which of the following places would you
most likely find anaerobic organisms?
a) Freshwater streams or rivers
b) The intestinal tract of animals
c) Warm, humid habitats
d) Cold, dry habitats
• Cellular Respiration (Aerobic Respiration with
Oxygen) Occurs in 2 phases:
– Phase 1 is Glycolysis (Anaerobic)
– Phase 2 is the Citric Acid Cyle/Kreb’s Cycle
(Aerobic)
• Phase I: Anaerobic
• Named: Glycolysis means the splitting of
glucose
– Oxygen is NOT directly involved in this step
– Occurs in the cytoplasm of cells
– The process of breaking down glucose begins with
glycolysis, producing 2 molecules of ATP for each molecule
of glucose broken down.
– Glycolysis breaks down 1 glucose into 2 pyruvic acid.
– Produces 2 ATPs
• At the end of glycolysis if O2 is NOT present,
anaerobic respiration (without oxygen) takes place.
• At the end of glycolysis if O2 is present aerobic
respiration (with oxygen) takes place (Citric Acid
Cycle)
• Phase II: Aerobic
– Citric Acid Cycle (Kreb’s Cycle)
• Completes the breakdown of glucose
• Occurs in the mitochondria of cells
• In this reaction, pyruvic acid is changed to acetic
acid. Then acetic acid forms citric acid.
– Results: Carbon dioxide is released
2 ATP are produced
State Test Question
Which organelle performs cellular
respiration?
a) Lysosome
b) Ribosome
c) Chromosome
d) Mitochondria
– 2. Electron Transport Chain
– This process is considered aerobic (with oxygen),
because oxygen is the final electron acceptor in the
chain
– This reaction accepts electrons and hydrogen ions which are
passed along, and energy is released.
• Results: Oxygen is the final electron acceptor.
34 ATP are produced
• At the end of the cellular respiration, glycolysis has
produced 2 ATPs
• The citric acid cycle has produced 2 ATPs
• The electron transport chain has produced 34 ATPs
• For aerobic respiration, a total of 36 ATPs
• Cellular Respiration makes a total of 38 ATPs
Electron
Electron
Electron
State Test Question
•
a)
b)
c)
d)
Both plant and animal cells have the
ability to—
make glucose.
move.
reproduce.
release oxygen.
• Anaerobic respiration (without oxygen): Anaerobic
respiration occurs when oxygen is NOT present. This
process is called fermentation, and is used by
organisms to produce energy without oxygen. Yeast
cells undergo alcoholic fermentation when oxygen is
not present. Animals produce lactic acid when
oxygen is not available; this is called lactic acid
fermentation This process occurs in our muscles
cells during strenuous activity. The body cannot
supply enough oxygen to the muscle cells to keep up
with ATP production. When lactic acid forms and
builds up fatigue sets in.
Anaerobic
respiration
(Alcoholic
fermentation)
Lactic Acid
Fermentation
(Sore
Muscles)
There are 2 types of fermentation:
•
Alcoholic Fermentation
–
–
–
•
Occurs in yeast cells
This process is important to the baking
and wine industry
Products are alcohol (ethanol) and CO2
Lactic Acid Fermentation
-
-
Occurs in some unicellular and organisms and
human muscle cells.
This process is used to produce energy in muscle cells when no oxygen
is available.
Lactic acid build-up causes muscle
soreness
State Test Question
The energy from food that is used to
produce ATP from ADP is—
a) released via photosynthesis.
b) stored as radiation energy.
c) released in the Calvin cycle.
d) stored in the bonds of glucose.
State Test Question
As respiration begins, glucose is broken
down into pyruvic acid and two
molecules of ATP are formed. What will
happen next in yeast cells if NO oxygen
is available?
a) Krebs cycle
b) Photosynthesis
c) Alcoholic fermentation
d) Lactic acid fermentation
State Test Question
Which of the following BEST describes the
purpose of cellular respiration?
a) The production ATP in animals cells
b) The release of energy from glucose
molecules inside the cell
c) The diffusion of oxygen into and out of
cells
d) The production of amino acids
State Test Question
Which step in aerobic cellular respiration
produces the most ATP?
• Glycolysis
• Fermentation
• Krebs cycle
• Electron transport chain
State Test Question
The aerobic process in cellular respiration
uses the products of glycolysis in a
series of enzyme-catalyzed reactions in
the mitochondria to release CO2. This
process is called—
a) photosynthesis.
b) the Calvin cycle.
c) the Krebs cycle.
d) fermentation.
Comparison of Photosynthesis and Cellular
Respiration
• Photosynthesis
– 1. CO2 and H2O are
materials used
– 2. Takes place in cells
that contain
chlorophyll.
– 3. Photosynthesis
builds sugars
– 4. Glucose
and oxygen
are products
– 5. Produces
2 ATP’s
• Cellular Respiration
– 1, CO2 and H2O are
end products
– 2. Takes place in all
living cells
– 3. Breaks down
sugars
– 4. Glucose and
Oxygen are materials
used
– 5. Produces 38
ATP’s
• ****The end products of aerobic
respiration are the starting materials of
photosynthesis
C6H12O6 + O2
CO2 + H2O + ATP
Cellular Respiration
Light Energy
CO2 + H2O
C6H12O6 + O2
Photosynthesis
State Test Question
In which of these processes does the Sun’s
energy play a direct role?
a) Entropy
b) Glucose synthesis
c) Anaerobic respiration
d) Cellular respiration
State Test Question
Which of the following statements is false?
a) Cellular respiration is a metabolic process that
releases energy that is stored in the bonds of
glucose in the form of ATP.
b) Photosynthesis is a two-part reaction that uses
the Sun’s energy to produce glucose from
carbon dioxide and water.
c) ATP acts as the energy currency of cells by
giving up two phosphate molecules in an
electron transfer.
State Test Question
Which process supplies the energy needed
to produce ATP in the Cell?
a) Cellular respiration
b) Diffusion
c) Protein synthesis
d) Osmosis
State Test Question
Which of the reactions would result in the
Greatest release of energy?
a) 2H2O→ 2H2 + O2
b) ADP + phosphate → ATP
c) ATP → ADP + phosphate
d) 6CO2 + 6H2O → C6H12O6 + 6O2