Chapter 7-Energy from Food

Life on Earth is solar-powered.

Photosynthetic organisms convert the energy of sunlight into chemical energy in foods.

Classification of OrganismsAutotrophs (self-feeders)=Producers.

– Start with inorganic molecules and make organic molecules.

– Process of Photosynthesis: reactants products.

6CO2 + 6H2O + energy C6H12O6 + 6O2.

– Plants, algae,seaweed, and photosynthetic bacteria.

Heterotrophs (other eaters)=Consumers.Obtain food by eating producers or other

consumers.

Cellular Respiratation

Producers and consumers-plants and animals.

Chemical process- oxygen converts chemical energy in food into chemical energy of ATP

Reactants Products

C6H12O6 + 6O2 6CO2 + 6H2O + energy (38 ATP)ATP main energy source for work.

Chemical Recycling

Water, carbon dioxide (CO2), oxygen, and glucose are continually recycled.

                                                    

                                                

Concept 7.2- Energy

Definition of energy-2 basic forms-

– Kinetic energy- energy in motion– Potential energy- stored energy– Example- climbing stairs. – Class examples-– Energy is not created or destroyed.– Energy is converted from one form to another.

Water slide analogy-.– What happens to the energy as we come

to a stop?– What is thermal energy?– A type of kinetic energy in which there

is random movement of molecules.– Heat is thermal energy that is transferred

from a warmer object to a cooler one.– The thermal energy that occurs when we

exercise cannot be retrieved. To do more work we need more energy provided by the foods we eat.

Chemical Energy -a form of potential energy found stored in foods.

                                                           

                                                             

Putting Chemical Energy to Work

Organic molecules in food are high in chemical energy

Glucose reacts with oxygen in cellular respiration.

The “exhaust” is water and carbon dioxide.Cells are more efficient than autos. 40% of

energy from food is used for work.The other 60% is lost as heat (thermal energy)Calorie= amount of energy to raise the

temperature of 1 gram of water by 10 C.A calorie is too small- We use kcal=1,000 cal.

ATP provides energy for the cell

Key- Chemical energy in food has to be converted to energy stored in ATP.

ATP Adenosine triphosphate.Adenosine= 5 carbon sugar ribose +

nitrogen containing compound adenine.Triphosphate= tail of 3 phosphate groups.

                                         

                                                                                                                                  

How ATP Packs Energy

The phosphate groups are the source of energy.Each phosphate group is negatively charged and

since like charges repel, this contributes to the potential energy stored in ATP.

Spring comparison.A chemical reaction breaks one of the phosphate

bonds and potential energy is released.The result is ADP= Adenosine diphosphate.

Types of Cellular Work

The Phosphate group is transferred to another molecule by specific enzymes.

The molecule that accepts the phosphate group changes, driving the work.

3 types of work-– Chemical work- building molecules

– Transport Work- moving solutes across membranes

– Mechanical Work- muscle contractions.

ATP Cycle is Continuous

Work consumes ATP.ADP and phosphate

regenerate ATP.The source of this

energy is the organic molecules in the food we eat.

Very fast reaction.

                                                    

                                      

Cellular RespirationAn aerobic process- Oxygen is needed Cellular respiration’s main function to generate

ATPs Cellular respiration transfers hydrogen and

carbon atoms from glucose to oxygen forming CO2 and H2O.

“Falling electrons”-released from C-H bonds fall towards oxygen ( an electron grabber), releasing energy.

Electron Transport Chains- a series of transfers in which electrons are passed from one electron carrier to the next releasing energy to make ATP.

3 stages of Cellular Respiration

Stage 1- Glycolysis- “splitting of sugar.”– occurs in the cytoplasm of the cell.– Oxygen is not used in this step- Anaerobic.– 6 C glucose molecule is broken down into two

3C pyruvic acid molecules.– Results in 2 ATPs being produced.– Glycolysis transparency- figure 7-17 pg. 149.

Glycolysis:

                                                                                                               

                                                            

Stage 2- Krebs Cycle.– Occurs in the cell’s mitochondria.– Each Pyruvic acid (from glycolysis) is broken

down into a 2C molecule called Acetyl CoA.– Each AcetylCoA enters the Krebs cycle and

produces 1 ATP.– Since there are two Pyruvic acid molecules

this results in 2 ATPs per glucose molecule.– Krebs Cycle transparency- figure 7-18 pg.150.

Krebs Cycle

                                                                                                             

                                                              

Stage 3- Electron Transport Chain.– Occurs in inner membrane of mitochondria.– 2 parts.

• Electron transport chain.– Electrons are pulled to oxygen at the end

of the chain.• ATP production.

– Energy released during each transfer provides for ATP to be formed from ADP and Phosphate.

– Results in 34 ATPs per glucose molecule.

Electron Transport Chain.A staircase, releasing energy at each step.

                                                          

                                                  

Electron Transport Chain

                                                                                                              

                                                             

Result of Cellular Respiration

To generate ATP for cellular work.One glucose molecule yields 38 ATP.

– Glycolysis= 2 ATP.– Krebs Cycle= 2 ATP.– Electron Transport Chain= 34 ATP.

Most ATP production requires oxygen.We cannot survive long without oxygen!!!

Fermentation- Anaerobic

Makes ATP when oxygen is not available.Makes ATP from glycolysis.Yield of 2 ATP.Fermentation regenerates enough ATP for short

bursts of activity.– Ex. A sprint (not a marathon).

Fermentation in muscle cells produces lactic acid – a waste product resulting in fatigue.

Since oxygen is consumed to convert lactic acid back to pyruvic acid, we have increased breathing after exercise.

Fermentation in Microorganisms

Yeast ferment sugar producing alcohol.– This is alcoholic fermentation.– Beer, wine, champagne.– Baker’s yeast- CO2- makes bread rise.

Fungi and bacteria produce lactic acid in fermentation.– Milk is transformed into yogurt and cheese.– Cabbage is transformed into sauerkraut.