Chapter 8Energy in a Cell

What you will Learn

You will learn what ATP is.

You will explain how ATP provides energy for the cell.You will describe how chloroplasts trap the sun’s energy to make ATP and complex carbohydrates.You will compare ATP production in mitochondria and chloroplasts.

ATP in a MoleculeCell Energy; essential to life

▪Work and need for energy▸All living organisms must be able to produce

energy from the environment.▸Store energy for future use.▸Use energy in a controlled manner.

▪Processes that require energy▸Active transport, cell division, muscles contracting,

etc..

Energy source in cells

ATPadenosine triphosphate▪ATP is composed of an adenosine

molecule with 3 phosphate groups attatched▸Phosphate groups are charged molecules.

Forming and Breaking Down ATP

▪The charged phosphate groups act likepositive poles of two magnets.▸Hard to attrack two with the same charges, takes a

lot of energy (ADP, adenosine diphosphate).▸Tremendous amount of energy to attrack the third

phosphate group.–The thrid one wants to get away and when it does the bond

is broken releasing a great amount of energy.

▸The energy from the ATP becomes available and the resulting molecule is ADP which can attrack another phosphate group to make ATP and the whole cycle starts over.

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Tapping the energy stored in

ATP▪When energy is released, cells must have

a way to capture the energy or it is wasted.▪Celluar proteins have a specific site where

ATP can bind.▪When the third phosphate group s bond is

broken, the cell can capture the energy released and use the energy.

Figure 9.3Page 229

Uses of the Cell Energy

▪Making new Molecules.▪Cell Reproduction.▪Maintaining homeostasis.▪Kidney functions▪Exercising.

PHOTOSYNTHESIS

Trapping the Sun’s Energy

▪Process plant’s use to trap the sun’s energy and build carbohydrates, glucose, that store energy.

▪Two phases:▸light-dependent reactions▸light-independent reactions

Light-Dependent Reactions

▪Light-dependent reactions converts light energy into chemical energy, ATP.

▪Reactions take place in the thylakoid discs inside the chloroplasts.▸The pigment chlorophyll (a and b) absorb most

color wavelengths except green. Green is reflected back making the leaf green in color.

Please turn to page 233 of your books

Figure 9.6 page 233

Light-Independent Reactions

The Calvin Cycle

▪Series of reactions that use carbon dioxide to form carbohydrates.

▪Does not require light.▪Takes place in the chloroplasts.

▪Only one molecule of CO2 is made each time through the cycle, it takes six times to make one glucose.

Please turn to page 235

Page 235 The Calvin Cycle

Getting Energy to Make ATPCellular Respiration

▪Three stages of Cellualar respiration:

–Glycolysis (anaerobic)–Citric Acid Cycle (aerobic)–Electron Chain Transport (aerobic)

FermentationLactic acid and Alcoholic

▪Anaerobic energy process▪Two ATP are formed▪Lactic Acid is animals▪Alcoholic in yeasts and plants

Figure 9.12 page 241

Comparing Photosynthesis and Cellular Respiration

Turn to page 243