Unit 4: Energy Flow

ATP, Photosynthesis, and Cellular Respiration

Energy – What is it? The ability to do work Energy can not be created or destroyed

– Energy is TRANSFORMED Forms of energy

– Light, electric, chemical Chemical energy is stored in the

electrons of chemical bonds

Biochemical Energy Cells store and release energy using the

chemical ATP– Adenosine triphosphate

ATP is the “energy currency” of the cell– MANY cellular processes use ATP

Cells release energy by breaking a phosphate bond

Photosynthesis Plants convert light energy into chemical

energy Energy is stored in the bonds of

carbohydrates

Light and Pigments Light travels in waves Colors have different wavelengths

“White” light is a mixture of all colors in the visible spectrum

Red – longest wavelength, lowest energy

Light and Pigments Plant pigments absorb sunlight Chlorophyll – green pigment needed for

photosynthesis– Reflects green light– Absorbs other light

Photosynthesis Overview Reactants: CO2, H2O, (light energy) Products: O2, C6H12O6 (glucose) Two reactions

– Light-dependent reaction– Calvin Cycle (light-independent reaction)

Electron Carriers Light energy “excites” electrons in

chlorophyll High energy electrons need special

carriers– ie: NADP+ and NAD+

Light-Dependent Rxn Chlorophyll absorbs light, and electrons

become energized Water splits to produce H+ and O2

Electron loses energy to form ATP– ATP goes to Calvin Cycle

H+ and NADP forms NADPH– Carries energy to

Calvin Cycle

(Light Independent Rxn)

Light Reaction – Electron Transport

CO2 is added to a 5 carbon sugar

Energy from NADPH & ATP are used to carry out reactions

Light-Independent Rxn(Calvin Cycle)

Produces sugar (glucose)

Photosynthesis Overview

Chloroplast Structure

– Light rxn

Stroma – open space – Calvin cycle

Thylakoid sacs contain chlorophyll Granum – stacks of thylakoids

Light Reaction

Calvin Cycle

ATP Revisited

How do living things use ATP for energy?

Where does ATP come from?

Biochemical Energy Cells store and release energy using ATP

– Adenosine triphosphate ATP is the “energy currency” of the cell

Cells release energy by breaking a phosphate bond

Overview of Cellular Respiration

Cellular Respiration

Energy from glucose is released – In the presence of O2

– Energy is stored in ATP

– CO2 is a byproduct

6O2 + C6H12O6 6CO2 + 6H2O + ATP

oxygen + glucose carbon dioxide + water + ATP

Overview of Cellular Respiration 3 Stages

– Glycolysis

– Krebs Cycle

– Electron Transport Chain

Glycolysis In the cytoplasm Glucose breaks into 2 molecules of pyruvic

acid (3C) Uses 2 ATP, produces 4 ATP

– Net gain of 2 ATP

2 NADH produced Pyruvic acid is used

for respiration OR fermentation

Krebs Cycle In the mitochondria Pyruvic acid breaks down Series of 9 rxns which

produce:– CO2

– FADH2 and NADH

– 2 ATP

FADH2 and NADH go on to the ETC to….– MAKE MORE ATP!!!!

Electron Transport Chain

Occurs in mitochondria Uses high energy

electrons from FADH2 and NADH to make ATP

O2 accepts the final electron forming H2O

The Totals

Electron carriers which go on the electron transport chain to generate ATP!

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Fermentation Releases energy from food in the

absence of O2

2 Types– Alcoholic – produces ethanol and CO2

• Yeast, bacteria

– Lactic Acid – produces lactic acid• Muscle cells, bacteria