Download Cells and Energy

CELLS AND ENERGY
Chapter 4
Preview Vocabulary

Metabolic processes take one of two directions:

They synthesize/anabolize (build up material and store
energy).
or



They hydrolyze/catabolize (break material down and
release energy).
Chemosynthesis and photosynthesis are synthesizing
processes that capture the energy needed for life and
store it in sugars.
Cellular respiration and fermentation are catabolic
processes that break down sugars and deliver energy
to sustain life.
AKS Standards
8d - explain the role of cell organelles in maintaining homeostasis
and cell reproduction for both prokaryotic and eukaryotic cells;
8l - analyze and explain the storage and release of energy through
the process of photosynthesis and respiration (GPS);
10a - relate the complexity and organization of organisms to their
ability for obtaining, transforming, transporting, releasing and
eliminating the matter and energy used to sustain the organism
(GPS)
The chemical energy used for most cell
processes is carried by ATP.






ATP stands for Adenosine
Triphosphate
ATP is a molecule made up of
adenosine and three negatively
charged phosphate groups.
The energy carried by ATP is released
when a phosphate group is removed
from the molecule.
The bonds holding the 3rd group in
ATP is unstable and very easily
broken.
When the 3rd phosphate is removed,
energy is released and ATP becomes
ADP, or adenosine diphosphate.
ADP is a lower-energy molecule.
The ATP Cycle

The breakdown of ATP to ADP and the production
of ATP from ATP can be represented by a cycle.
 ADP releases energy.
 ADP  ATP requires energy.
 ATP
Types of Phosphorylation



To make ATP, you must PHOSPHORYLATE and ADP
molecule.
This means that you must add a PHOSPHATE (P) to ADP
to make ATP.
Phosphorylation can occur in THREE WAYS:
1.
2.
3.
Substrate Level Phosphorylation: directly transferring a
phosphate group to ADP using an enzyme…as seen in
glycolysis and the Krebs cycle.
Oxidative Phosphorylation: using the power of a
concentration gradient where oxygen is the terminal
electron acceptor to phosphorylate ADP into ATP...as seen
in the electron transport chain of the mitochondria.
Photophosphorylation: using the power of sunlight to
phosphorylate ADP into ATP….as seen in the
photosynthesis light reactions.
Types of Phosphorylation
SUBSTRATE LEVEL PHOSPHORYLATION
OXIDATIVE PHOSPHORYLATION
PHOTOPHOSPHORYLATION
Ways of Obtaining Energy


Heterotrophs: obtain energy by breaking down carbon
compounds (food) in the presence or absence of oxygen.
Animals, fungi, and some protistans are heterotrophs.





Carbohydrates: 4 energy calories per mg
Lipids: 9 energy calories per mg
Protein: 4 energy calories per mg
Autotrophs: use chemical energy to build their own food
molecules.
Plants and most algae photosynthesize, many bacteria
chemosynthesize.


Photosynthesis: converts light energy into carbon compounds.
Chemosynthesis: converts chemical energy into carbon compounds.
AKS Standards
8d - explain the role of cell organelles in
maintaining homeostasis and cell reproduction
for both prokaryotic and eukaryotic cells;
8l - analyze and explain the storage and release
of energy through the process of photosynthesis
and respiration (GPS);
10a - relate the complexity and organization of
organisms to their ability for obtaining,
transforming,
transporting,
releasing
and
eliminating the matter and energy used to
sustain the organism (GPS)
Photosynthetic organisms are producers.


Photosynthesis is the process whereby
light energy is converted to chemical
energy and carbon is fixed into
organic compounds.
In the presence of light, plants
transform carbon dioxide and water
into carbohydrates and release
oxygen.



6 CO2 + 6 H2O + light → C6H12O6 + 6 O2
carbon dioxide + water + light → sugar +
oxygen
Plants then use the sugars to produce
complex carbohydrates such as
starches.
COMMON MISCONCEPTION
Plants DO NOT get energy from photosynthesis. Rather, they use light energy to build sugars.
They then use the sugars to build ATP via cellular respiration (just like animals).
Photosynthesis in plants occurs in
chloroplasts.


Chloroplasts are membrane-bound organelles
found in the leaves photosynthetic organisms.
Chlorophyll is the green pigment molecule in
chloroplasts that is directly involved in
photosynthesis.
Thylakoids: have membranes that
contain chlorophyll (where light is
absorbed).
Grana: stacks of thylakoid.
Stroma: fluid surrounding thylakoids
where Calvin cycle occurs.
The reactions of photosynthesis occur in
two main stages.
http://www.mhhe.com/biosci/bio_animations/02_MH_Photosynthesis_Web/
1.
Light-Dependent Reactions:




2.
Capture energy from sunlight and use this energy to produce ATP and
NADPH.
ATP and NADPH are the energy required to power the Calvin cycle.
Occur within and across the thylakoid membranes.
This is the “photo” phase – uses light.
Light-Independent Reactions:




Also called the dark reactions or the Calvin cycle.
Use the ATP and NADPH produced by the light reactions to build simple
sugars.
Occurs in the stroma of the chloroplast.
This is the “synthesis” phase – builds sugars.
Light Reactions:
-carried out by molecules in thylakoid
membranes
-convert light E to chemical E of ATP and NADPH
-split H2O and release O2 to the atmosphere
Calvin Cycle (Dark) Reactions:
-take place in stroma
-use ATP and NADPH produced in light
reactions to convert CO2 into simple sugars
-return ADP, inorganic phosphate, and
NADP+ to the light reactions
Overview of Light-Dependent Reactions
http://www.sumanasinc.com/webcontent/animations/content/harvestinglight.html
Overview of Light-Independent Reactions
http://highered.mheducation.com/sites/0070960526/student_view0/chapter5/animation_quiz_1.html
AKS Standards
8d - explain the role of cell organelles in maintaining homeostasis
and cell reproduction for both prokaryotic and eukaryotic cells;
8l - analyze and explain the storage and release of energy through
the process of photosynthesis and respiration (GPS);
10a - relate the complexity and organization of organisms to their
ability for obtaining, transforming, transporting, releasing and
eliminating the matter and energy used to sustain the organism
(GPS)
Cellular respiration makes ATP by
breaking down sugars.



Animals eat other organisms
for food, but food is not a
direct source of energy for
cells.
Instead, all organisms break
down molecules from food to
produce ATP.
Because it occurs in the
presence of oxygen, cellular
respiration is known as
aerobic respiration.
COMMON MISCONCEPTION
Animals are NOT the only organisms that use cellular respiration. All living organisms use some
type of respiration (aerobic or anaerobic) to produce ATP…this includes bacteria, protistans,
fungi, plants, and animals!!!
OVERVIEW OF CELLULAR RESPIRATION
The chemical formula for cellular respiration is:



6O2 + C6H12O6 → 6 CO2 + 6 H2O + Energy
oxygen + glucose → carbon dioxide + water + ATP
The reactants of cellular respiration are:


oxygen (O2) & glucose (C6H12O6)
The products of cellular respiration are:


carbon dioxide (CO2) and water (H2O)
The 4 main stages of cellular respiration are:

1.
2.
3.
4.
Glycolysis
Intermediate Step
Krebs Cycle (Citric Acid Cycle)
Electron Transport / Oxidative Phosphorylation
Cellular respiration occurs in mitochondria.


Mitochondria are membrane-bound organelles
found in the cells of organisms that perform cellular
respiration.
Mitochondria have a double membrane that serves
to compartmentalize the reactions of cellular
respiration.
Christae: folds created by convoluted inner membrane,
increases the surface area for the electron transport chain.
Matrix: aqueous solution in the center of mitochondria
where chemical reactions of Krebs cycle occur.
Inner-Membrane Space: area where a hydrogen ion
gradient is established using energy from electron
transport chain – gradient powers the production of ATP
from ADP and Pi.
The Players for Cellular Respiration









Mitochondria – site of cellular respiration in cells.
Glucose – energy source broken down to release ATP.
NADH & FADH2 – coenzymes that shuttle electrons from
Glycolysis & The Krebs Cycle to the Electron Transport Chain.
Glycolysis – begins the breakdown of glucose into two
molecules of pyruvate.
Intermediate Step – converts pyruvate from glycolysis into
Acetyl CoA for entry into Krebs cycle
Krebs Cycle – completes the breakdown of glucose.
CO2 – waste product of cellular respiration.
O2 – required for aerobic respiration.
Electron Transport Chain – establishes a concentration
gradient of hydrogen across the inner membrane – gradient
powers production of ATP.
Cellular respiration occurs in four main stages.
http://www.sumanasinc.com/webcontent/animations/content/cellularrespiration.html
http://www.mhhe.com/biosci/bio_animations/MH01_CellularRespiration_Web/index.html
Glycolysis
1.



Takes place in cytoplasm of cell just outside the mitochondria.
Begins the breakdown of glucose into 2 molecules of pyruvate.
Produces 2 ATP, 2 NADH, and 2 pyruvate
Intermediate Step
2.



Takes place just inside the mitochondria.
Converts pyruvate from glycolysis into acetyl CoA, which can enter the Krebs cycle.
Produces 2 NADH and 2 acetyl CoA; releases carbon-dioxide waste
Krebs (Citric Acid) Cycle
3.



Takes place in the matrix of the mitochondria.
Completes the breakdown of glucose.
Produces 2 ATP, 6 NADH, and 2 FADH2, releases carbon dioxide waste
Electron Transport
4.



Occurs across the inner membrane of the mitochondria.
Uses electrons donated from NADH and FADH2 to establish a hydrogen ion gradient across
the inner membrane which is used to power the production of ATP.
Produces approximately 34 ATP
Glycolysis occurs
in the cytoplasm.
Intermediate step
occurs just inside
the mitochondria.
Krebs cycle occurs
in the matrix of
the mitochondria.
Electron transport occurs
across the inner membrane
of the mitochondria –
concentration gradient
occurs in inner-membrane
space.
Overview of Glycolysis
http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter25/animation__how_glycolysis_works.html
Intermediate Step Converts Pyruvate into
Acetyl CoA
Overview of Krebs (Citric Acid) Cycle
http://highered.mheducation.com/sites/0072507470/student_view0/chapter25/animation__how_the_krebs_
cycle_works__quiz_1_.html
Overview of Electron Transport Chain
http://highered.mheducation.com/sites/0072507470/student_view0/chapter25/animation__electron_transp
ort_system_and_atp_synthesis__quiz_2_.html
Cellular respiration and photosynthesis
are like mirror images.
AKS Standards
8d - explain the role of cell organelles in maintaining homeostasis
and cell reproduction for both prokaryotic and eukaryotic cells;
8l - analyze and explain the storage and release of energy through
the process of photosynthesis and respiration (GPS);
10a - relate the complexity and organization of organisms to their
ability for obtaining, transforming, transporting, releasing and
eliminating the matter and energy used to sustain the organism
(GPS)
Respiration in the Absence of Oxygen (Anaerobic
Respiration)

When oxygen is NOT present,
glycolysis is followed by a
different pathway called
fermentation.



The 2 main types of fermentation
are:



Fermentation releases energy from food molecules
in the absence of oxygen
Because fermentation does not require oxygen, it is
said to be anaerobic.
alcoholic fermentation
lactic acid fermentation
Aside from the original 2 ATP’s
made during glycolysis, the only
energy produced is that which is
in the bonds of:


ethyl alcohol -- C2H6O
lactic acid – C3H5O3
As you can see, the role
of fermentation is
simply to provide
glycolysis with a steady
supply of NAD+.
By itself, fermentation
does NOT produce ATP.
Instead, it allows
glycolysis to continue to
produce ATP in the
absence of oxygen.
Fermentation and its products are important in
several ways.
Fermentation and Aerobic Respiration
Compared



Both processes use glycolysis to break down
glucose and other organic fuels into pyruvate.
The processes have different final electron
acceptors: an organic molecule (such as pyruvate or
acetaldehyde) in fermentation and O2 in cellular
respiration.
Cellular respiration produces 38 ATP per glucose
molecule; fermentation produces 2 ATP per glucose
molecule.