Transcript Chapter 9 Biology - s3.amazonaws.com

Energy in a Cell-Chapter
9 Biology
By: Mr. Herndon
2nd Quarter BIOLOGY
Kelton ISD
All organisms need energy.
 Energy from the sun is the major source and is
trapped by green organisms.
 This energy is used in cell processes like: active
transport, mobility (cilia and flagella), cell division,
protein production, etc.
GREEN ORGANISMS
Charged molecules behave like magnets.
ATP (Adenosine Triphosphate)
ATP
 has phosphate groups and these are
charged molecules
 is the energy-rich molecule that is primarily
used in cellular and other biological
processes
 holds energy between the 2nd and 3rd
phosphate groups.
 ATP>ADP>AMP
ATP
 is similar to
rechargeable batteries
wherein energy can be
stored again after use.
(by adding another
phosphate to ADP)
 ATP : battery
 protein : electronic device
List Three cellular activities that
require energy?
How does ATP store energy?
How can ADP be “recycled” to
form ATP again?
How do proteins in your cells
access the energy stored in ATP?
PHOTOSYNTHESIS
 process that uses the sun’s energy to make
simple sugars
 represented by the chemical equation:
6CO2 + 6H2O
C6H12O6 + 6O2
Carbon Dioxide + Water = Glucose + Oxygen
PHOTOSYNTHESIS
 converts simple sugars into complex
carbohydrates that store energy. (ex: starch)
 Since dependent on sunlight, it must have a
means of continuing even at night when
sunlight is not available.
 has 2 phases: light-dependent reactions
light-independent reactions
Two Phases
 Light-dependent reactions- convert light
energy into chemical energy. Relies heavily
on the sunlight to run process
 The molecules of ATP produced in the lightdependent reactions are used to fuel the next
phase
 Light-independent reactions- produce simple
sugars. Does not require light.
 It is also called the Calvin cycle.
PHOTOSYNTHESIS
 occurs in the chloroplast, specifically in the thylakoid
membranes.
Thylakoid Membranes
 have light-absorbing pigments (most common of
which is chlorophyll)
 Wavelength for green light is reflected (not absorbed),
thus, leaves are green.
Photosystems
 refer to the cluster of
pigments in the
thylakoid membranes
Light-Dependent Reactions
1. Sunlight strikes chlorophyll in a
photosystem.
2. This light energy “excites”/energizes
electrons.
3. Electrons are passed from chlorophyll to an
electron transport chain embedded in the
thylakoid membrane.
“Lost” or “spilled” energy is used for
 forming ATP from ADP
 pumping hydrogen ions into the thylakoid (a gradient is
formed, therefore…)
Light-Dependent Reactions
4. Electrons get re-energized in a second
photosystem.
5. At the end of another ETC, electrons are
carried to the stroma for later use.
6. NADP+ (an electron carrier) becomes
NADPH+ as it transfers the electrons to the
stroma. NADP+ can combine with 2 electrons
and a H+.
Electrons may run out…
 This is solved by photolysis which also occurs in the
first photosystem.
 Light breaks down H2O into ½ O2, 2 H+, and 2
electrons.
Light-Independent Reactions
 series of reactions that use CO2 to form
sugars (called “carbon fixation”)
 take place in the stroma
 also produces PGAL
(phosphoglyceraldehyde), a molecule that is
essential during cellular respiration
* PGAL a.k.a. G3P (glyceraldehyde-3phosphate)
The Calvin-Benson Cycle
PHOTOSYNTHESIS (simplified)
Cellular Respiration
 involves breakdown of food molecules by
mitochondria to produce ATP
 has 3 stages: glycolysis, the citric acid cycle,
and the electron transport chain
 Glycolysis is an anaerobic process, does not
require oxygen.
 The citric acid cycle and the electron
transport chain are both aerobic.
Glycolysis
 also refer to page 232
Glycolysis
 Glyco (sweet/sugar/glucose) + lysis (to split)
 Glucose (6-carbon compound) is split into 2
molecules of pyruvic acid (3-carbon
compound), occurs in the cytoplasm.
 not very efficient in terms of energy
production as it produces only 4 molecules of
ATP after starting the process with 2 ATP
molecules (net gain of 2 ATP molecules)
Glycolysis
 uses NAD as its electron carriers; each
molecule can carry 2 electrons
 PGAL from the Calvin cycle may also enter
this chemical process.
 If O2 is present, the pyruvic acid transfers to
the mitochondria to begin the aerobic
reactions.
*Refer to page 232 for the diagram.
The Citric Acid Cycle
 a.k.a. Krebs cycle
 uses the electron carriers NAD+ and FAD
 Each electron carrier transfers 2 electrons to
the inner membrane of the mitochondrion.
(Remember, the mitochondrion has an inner
and outer membrane.)
The Citric Acid Cycle
 every turn of the cycle produces:
The Citric Acid Cycle
 Refer to page 233 for the diagram.
Electron Transport Chain
ATP Production during Aerobic Respiration by Oxidative Phosphorylation
involving an Electron Transport System and Chemiosmosis
The Electron Transport Chain
 occurs in the inner membrane of the
mitochondrion
 very similar to the ETC in the thylakoid
 H+ ions are pumped continuously, making the
inner membrane positively charged.
 Oxygen is the final electron acceptor at the
end of the chain.
Why oxygen is important as the final
electron acceptor…
 It reacts with 4H+ ions and 4 electrons to form
2 H2O molecules.
 Proteins in the ETC cannot accept electrons
unless they are passed on to oxygen.
 If these proteins cannot accept electrons,
the entire chain is blocked, and ATP
production stops.
 ETC adds 32 ATP molecules to the 4 from
glycolysis and Krebs cycle.
Total ATP Production
Cellular Respiration (simplified)
Fermentation
 provides ATP supply in the absence of O2
 2 major types: lactic acid fermentation &
alcoholic fermentation
 happens after glycolysis
* NADH and FADH2 cannot continue accepting
electrons if O2 is unavailable. Therefore…
Lactic Acid Fermentation
 FAD cannot be replaced by the cell; however,
NAD can be replaced through lactic acid
fermentation.
 2 molecules of pyruvic acid produced in
glycolysis use NADH to form 2 molecules of
lactic acid. THIS RELEASES NAD TO BE
USED IN GLYCOLYSIS AND FORM 2 ATP
MOLECULES.
 Lactic acid is brought to the liver and converts
it into pyruvic acid.
Alcoholic Fermentation
 used by yeast cells and some bacteria
 produces CO2 and ethyl alcohol
 also produces 2 ATP molecules
* Refer to page 235 for the comparison of
fermentaion to cellular respiration.
References
www.swe.org/iac/images/NewMagnet.jpg
biology.clc.uc.edu/graphics/bio104/atp.jpg
lh4.ggpht.com/.../mkLl88rnJbg/IMG_0735.J
PG
4. earthobservatory.nasa.gov/Laboratory/ICE/I
mag...
5. bifsniff.com/wp-content/files/2007/04/theinc...
6. static.howstuffworks.com/gif/batteries-5.jpg
1.
2.
3.
References
7. extremefoamart.com/thumb/cartoon_man_in_the_m...
8. www.biology.iupui.edu/.../ch9chloroplast.jpg
9. micro.magnet.fsu.edu/.../chloroplastsfigure1.jpg
10. kvhs.nbed.nb.ca/gallant/biology/thylakoid.jpg
11. student.ccbcmd.edu/.../images/chemios_il.jpg
12. fig.cox.miami.edu/.../c7.10.17.chemiosmosis.jpg
13. student.ccbcmd.edu/.../images/u4fg46.jpg
References
14. fig.cox.miami.edu/.../c9x6cell-respiration.jpg
15. fig.cox.miami.edu/.../150/makeatp/sumgly.jpg
16. staff.jccc.net/PDECELL/cellresp/simpleover.gif
17. media-2.web.britannica.com/eb-media/43/21043-...