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 ORGANISMSGREEN ORGANISMS

Charged molecules behave like magnets.

ATP (Adenosine Triphosphate)

ATP

has phosphate groupsphosphate 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

6CO2 + 6H2O C6H12O6 + 6O2

Carbon Dioxide + Water = Glucose + Oxygen

process that uses the sun’s energy to make simple sugars

represented by the chemical equation:

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 light-dependent 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 photolysisphotolysis 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-3-phosphate)

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. OxygenOxygen 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

1. www.swe.org/iac/images/NewMagnet.jpg2. biology.clc.uc.edu/graphics/bio104/atp.jpg3. lh4.ggpht.com/.../mkLl88rnJbg/

IMG_0735.JPG4. earthobservatory.nasa.gov/Laboratory/ICE/

Imag...5. bifsniff.com/wp-content/files/2007/04/the-

inc...6. static.howstuffworks.com/gif/batteries-5.jpg

References

7. extremefoamart.com/thumb/cartoon_man_in_the_m...

8. www.biology.iupui.edu/.../ch9chloroplast.jpg9. micro.magnet.fsu.edu/.../chloroplastsfigure1.jpg10. kvhs.nbed.nb.ca/gallant/biology/thylakoid.jpg11. student.ccbcmd.edu/.../images/chemios_il.jpg12. fig.cox.miami.edu/.../c7.10.17.chemiosmosis.jpg13. 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-...