CELL RESPRIATION CHAPTER 9. 9–1CHEMICAL PATHWAYS Chemical Energy and Food Calorie – amount of energy needed to raise1 gram of water 1 0 Celcius. Cells.

CELL RESPRIATIONCHAPTER 9

9–1 CHEMICAL PATHWAYS

Chemical Energy and Food

Calorie – amount of energy needed to raise1 gram of

water 10 Celcius.

Cells release energy from glucose gotten from food.

Process begins with glycolysis (splitting of a glucose molecule).

If oxygen is present (aerobic), it leads to Kreb’s Cycle & Electron

Transport Chain.

If oxygen is not present (anaerobic), it leads to fermentation.

Glucose

Glycolysis Krebs cycle

Electrontransport

Fermentation (without oxygen)

Alcohol or lactic acid

CHEMICAL PATHWAYS

OVERVIEW OF CELLULAR RESPIRATION

Cellular respiration (Rs) – process that releases energy by

breaking down food molecules in the presence of oxygen.

6O2 + C6H12O6 6CO2 + 6H2O + Energy ( 36ATP)

In words:6 oxygen + glucose yields 6 carbon dixoide + 6 waters +

36 ATP

3 stages of cell respiration

Glycolysis

Kreb’s Cycle

Electron Transport Chain

GlucoseGlycolysis

Cytoplasm

Pyruvic acid

Electrons carried in NADH

Krebs Cycle

Electrons carried in NADH

and FADH2

Electron Transport Chain

Mitochondrion

Figure 9–2 – pg. 222 Cellular Respiration: an Overview – Cell respiration is a process that releases energy by breaking down food molecules in the presence of oxygen. Glycolysis takes place in the

cytoplasm. Krebs cycle and electron transport chain take place inside the mitochondria.

Mitochondrion

GLYCOLYSIS1st step in Rs

Process in which one molecule of glucose is broken in half

to produce two molecules of pyruvic acid and 2 ATP

molecules.

At the end, 4 ATP are made, however, 2 ATP are used in the

beginning.

Net ATP production during glycolysis is 2 (4-2 = 2)

WHAT DOES GLYCOLYSIS BREAK DOWN?GLUCOSE

Glucose

To the electron transport chain

2 Pyruvic acid

Figure 9–3 Glycolysis – pg. 223 – Glycolysis is the first stage in cellular respiration. During glycolysis, glucose is broken down

into 2 molecules of pyruvic acid.

FERMENTATIONNo oxygen after glycolysis, fermantation takes

place (anaerobic)

Fermentation releases energy from food molecules when there is no oxygen available.

Two types of fermentation Alcoholic Lactic Acid

ALCOHOLIC FERMENTATION

Performed by yeast Produces carbon dioxide and ethyl alcohol as

waste products.

Carbon dioxide causes bread to rise

LACTIC ACID FERMENTATION

Pyruvic acid is converted to lactic acid

Happens when mucles are used during rapid exercise.

Not enough oxygen available and the body can’t produce

the ATP needed.

Buildup of lactic acid creates the painful burning sensation

during hard exercise.

Reason muscles feel sore after intense activity.

Glucose Pyruvic acidLactic acid

Figure 9–4 – pg. 225 Lactic Acid Fermentation – Lactic acid fermentation converts glucose into lactic acid. The first part of the equation is glycolysis.

The second part shows the conversion of pyruvic acid to lactic acid.

9–2 The Krebs Cycle and Electron Transport

Introduction

End of glycolysis, 90% of energy from glucose is unused.

Oxygen – most powerful electron acceptor – required for the remaining steps of cell respiration.

Energy-releasing reactions in the cell require oxygen and this is the reason we “breathe” or “respire”

KREBS CYCLE

Oxygen is available, glycolysis is followed by

Krebs Cycle.

Named after Hans Krebs an English biochemist.

During Krebs Cycle, pyruvic acid (from

glycolysis) is broken down into carbon dioxide.

KREB’S CONT’DBegins when pyruvic acid enters the mitochondria

Citric acid is broken down and CO2 is released.

Electrons are transferred to energy carriers (usually proteins)

Each turn of the Krebs Cycle produces 1 ATP molecule.

Krebs turns twice during respiration, producing 2 ATP overall.

CO2 released during Krebs is the source of all the CO2 organisms breath out.

WHY IS THE KREBS, CYCLE ALSO KNOW AS THE CITRIC ACID

CYCLE?

CITRIC ACID IS BROKEN DOWN INTO CO2

Citric Acid Production

Figure 9–6 The Krebs Cycle – pg. 227 – During the Krebs cycle, pyruvic acid from glycolysis is used too make CO2, NADH, ATP AND

FADH2

Mitochondrion

ELECTRON TRANSPORT3rd step in cell respiration

Uses high energy electrons from the Krebs cycle to create ATP

from ADP.

Electrons are passed along an electron transport chain.

Passed from 1 carrier protein to the next.

Located on the interior membrane (cristae) of the mitochondria.

At the end the electrons (H+) combine with O to form water.

Waste products of cell respiration.

Figure 9–7 Electron Transport Chain – pg. 228 – The electron transport chain uses high-energy electrons from the

Krebs cycle to convert ADP into ATP.

Electron TransportHydrogen Ion Movement

ATP Production

ATP synthase

Channel

Inner Membrane

Matrix

Intermembrane Space

Mitochondrion

THE TOTALSGlycolysis produces 2 ATP.

Kreb’s Cycle produces 2 ATP

Electron Transfer Chain produces 32 ATP

Grand Total of Cell Respiration = 36 ATP

See Fig. 9.8- page 229.

COMPARING PHOTOSYNTHESIS AND CELLULAR RESPIRATION

Photosynthesis (PS) & Cell Respiration (RS) are opposite chemical reactions

They are the reverse of each other

PS removes CO2 from the atmosphere

RS puts it back

PS releases O2 and RS uses O2 to release energy (ATP) from food.

Products of Ps are the reactants of RS.

Products of RS are the reactants for Ps.

Cell respiration takes place in all eukaryotes and some prokaryotes.

Photosynthesis takes place only in plants, algae and some bacteria.

See Fig. 9-10, page. 232.

Flowchart – Steps of Cellular Respiration

Glucose(C6H1206)

+Oxygen

(02)

Glycolysis KrebsCycle

ElectronTransport

Chain

Carbon Dioxide

(CO2)+

Water(H2O)

Cellular Respiration