Chapter 9: Cellular RespirationFergusonRevised Spring 2014 to match text wksts 9.1 and 9.2

Chemical Energy and FoodWe eat because food provides our bodies

with energy.Calorie = amount of energy needed to raise 1

gram of water 1 degree Celsius. Cells don’t actually “burn” calories from

molecules like glucose.Instead, they gradually release the energy.

There are 1000 calories in 1 Calorie (notice the difference in the capital C) on our food labels the Calories are given.

Cellular respiration ; the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen, begins with a chemical pathway called glycolysis.

Although we know that glucose has 90 times more energy than the ATP molecule (from chapter 8) The first step of cellular respiration, glycolysis only releases a small amount of that energy.

Overview of Cellular Respiration

Process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.

6O2 + C6H12O6 6CO2+ 6H2O + Energy

How does this compare to Photosynthesis??

Overview of Cellular RespirationThere are 3 main stages:

◦Glycolysis◦Krebs Cycle◦Electron Transport Chain

Each stage captures some chemical energy in the cell, and uses it to produce ATP.

Glycolysis takes place in the cytoplasm while the Kreb’s cycle and electron transport occur in the mitochondria.

The different stages are important so that our cells get as much energy as possible through the process of cellular respiration.

If there was only one step in the pathway the problem would be. . .All of the energy from glucose would be released at once, and most of that energy would be lost in the form of light and heat, instead of being stored in ATP molecules

GlycolysisProcess in which one molecule of glucose is

broken in half, producing two molecules of pyruvic acid.

Occurs in the cytoplasm.The cell starts glycolysis by using the energy

from 2 ATP molecules to produce 4 ATP molecules.

What is the net gain of ATP?

GlycolysisUses the electron carrier NAD+ ,

which becomes NADH. Can produce thousands of ATP in

secondsDoes NOT require oxygen.

(Anaerobic)

The function of NAD+ in glycolysisThe electron carrier, NAD+ holds

a pair of high energy electrons (as NADH) until they can be transferred.

In this way it helps pass the energy from glucose to other cell pathways.

This helps to produce thousands of ATP molecules in the cell.

Can problems arise in this step?

If cells were to generate large amounts of ATP just from glycolysis, then within a few seconds all the NAD+ electron carriers would be filled up with electrons, and the process would stop until they could be moved to a different pathway.

FermentationA process that releases energy from

food molecules in the absence of oxygen.

Both types of fermentation regenerate NAD+ that can be used in Glycolysis.

Fermentation changes NADH back to NAD+ by passing the high energy electrons back to the pyruvic acid.

2 types of fermentationAlcoholic FermentationUsed by yeasts and other microorganisms

◦ Pyruvic Acid + NADH alcohol + CO2 + NAD+

When yeast is baked the small amt of alcohol produced

evaporates in the oven at high temp.

Lactic Acid Fermentation – muscle cells, and the bacteria used in dairy products.◦Pyruvic Acid + NADH lactic acid +

NAD+

Instead of Fermentation…At the end of Glycolysis, about

90% of the energy in glucose is still unused, locked away in the bonds of pyruvic acid.

To release the remaining energy, cells must use oxygen.

The next 2 steps of cellular respiration are said to be aerobic.

During rapid exercise your muscle cells produce ATP by lactic acid fermentaion

When you need a quick sprint, your muscle cells run out of stored oxygen quickly, and may not have time to go through the entire cellular respiration process so to get a quick energy boost the ATP is used.

At the end of glycolysis 90% of the chemical energy in glucose is still unused.

Because the final stages of cellular respiration require oxygen they are considered to be aerobic.

The Krebs CyclePyruvic acid is broken down

into carbon dioxide in a series of energy-extracting reactions.

Begins when a molecule of pyruvic acid enters the mitochondria.

After many reactions, the pyruvic acid becomes CO2, NADH is formed, ATP is formed, and another electron carrier, FADH2 is formed.

The Krebs CycleCO2 is released when

we exhale.ATP is used to power

the cell’s activities.In the presence of

oxygen, the electron carriers NADH and FADH2 are used to create even greater amounts of ATP.

Electron Transport ChainUses high-energy electrons

from the Krebs cycle to convert ADP to ATP.

The chain is composed of a series of proteins throughout the membranes of the mitrochondria.

These proteins pump H+ ions through the membrane, which powers ATP Synthase to convert ADP to ATP.

Electron Transport Chain

The TotalsGlycolysis alone can only produce 2 net ATP.In the presence of oxygen, Cellular Respiration

can produce 36 molecules of ATP.

Energy and ExerciseQuick Energy

◦When athletes only need energy for a quick burst (~90 seconds), they resort to the energy from Glycolysis and Lactic Acid Fermentation.

Long-Term Energy◦When athletes need energy for an

extended period of time, cellular respiration is the only way to provide continuous energy.

Comparing Photosynthesis and Cellular Respiration

Photosynthesis Cellular Respiration

Function Energy capture Energy release

Location Chloroplasts Mitochondria

Reactants CO2 and H2O C6H12O6 and O2

Products C6H12O6 and O2 CO2 and H2O

Equation 6CO2 + 6 H2O + energy C6H12O6 + 6O2 6O2 + C6H12O6 6CO2+ 6H2O + Energy

Make your own concept map: Using the following terms, create a concept map that

describes the process of cellular respiration.

2 ATP2 ATP36 ATP6 NADH2 FADHElectron transport chainMitochondrionCytoplasmFermentationGlycolysisGlucosePyruvateLactic acidKreb's Cycle

Book ReviewAnswer the following questions

on page 237:◦1-10◦12, 13, 14, 19, 20, 22.