Cellular Respiration……

• Nearly all the cells in our body break down sugars to provide the energy to make ATP

• Most cells of most organisms obtain energy aerobically using oxygen– The aerobic processing of energy from sugar is called

cellular respiration– Cellular respiration yields CO2, H2O, and a large

amount of ATP

CELLULAR RESPIRATION

Introduction

• Aerobic respiration requires O2 vs. Anaerobic respiration which doesn’t use O2

• Some cells only use anaerobic respiration • Some cells use aerobic respiration• Some cells usually use aerobic but may resort to

anaerobic respiration if necessary

Differences in how cells break down glucose - aerobic vs. anaerobic respiration

Structure of the Mitochondrion

The process of cellular respiration takes place in the mitochondria of eukaryote cells

In Our Body:• Breathing and cellular respiration are closely

related.• Breathing supplies oxygen to our cells for cellular

respiration and removes carbon dioxide from our cells which is a waste product of cellular respiration

O2CO2

BREATHINGLungs

CO2 O2

BloodstreamMuscle cells carrying out

CELLULAR RESPIRATION

Figure 6.1

Sugar + O2 ATP + CO2 + H2O

• Cellular respiration breaks down glucose molecules and stores their energy in ATP (adenosine triphosphate: ADENOSINE –P—P--P)

– The process uses O2 and releases CO2 and H2O

Figure 6.2A

Glucose Oxygen gas Carbon dioxide

Water Energy

Chemical equation for cellular respiration

• Cellular respiration oxidizes sugar and produces ATP in three main stages– Glycolysis occurs in the cytoplasm – The Krebs cycle and – The electron transport chain occur in the

mitochondria

Respiration occurs in three main stages

STAGES OF CELLULAR RESPIRATION AND FERMENTATION

Important Molecules Involved

NAD+

FAD++Electron and hydrogen ion carrier molecules

NAD+ carries 2 electrons and one hydrogen ion/ molecule

FAD++ carries 4 electrons and two hydrogen ions/ molecule

Glycolysis – In cytoplasm6 carbon sugar (1 molecule)

3 carbon molecule ( 2 molecules)

ATP needed to break molecule apart

NAD+ collects electrons and hydrogen and forms ATP

Kreb Cycle – matrix of mitochondrion

A multi-step process involving many enzymes that uses oxygen to break down the pyruvic acid molecules to CO2, captures energy as ATP, and collects energized electrons and hydrogen to send to cristae membranes of mitochondrion

ELT & Chemiosmosis – cristae of mitochondrion

Chemiosmosis involves the pumping of protons through special channels in the membranes of mitochondria from the inner to the outer compartment. The pumping establishes a proton gradient that flows through ATP synthase to make 32-34 ATP

• For each glucose molecule that enters cellular respiration, chemiosmosis produces 36 - 38 ATP molecules

The 3 stages of aerobic cellular respiration

KREBSCYCLE

Electron shuttleacrossmembranes

Cytoplasmic fluid

GLYCOLYSIS

Glucose2

Pyruvicacid

2AcetylCoA

KREBSCYCLE

ELECTRONTRANSPORT CHAIN

AND CHEMIOSMOSIS

Mitochondrion

by substrate-levelphosphorylation

used for shuttling electronsfrom NADH made in glycolysis

by substrate-levelphosphorylation

by chemiosmoticphosphorylation

Maximum per glucose:Figure 6.14

• Polysaccharides can be broken down to monosaccharides and then converted to glucose for glycolysis

• Proteins can be digested to amino acids, which are chemically altered and then used in the Krebs cycle

• Fats are broken up and fed into glycolysis and the Krebs cycle

Animal Cells use many kinds of organic molecules as fuel for cellular respiration

• Under anaerobic conditions (no oxygen), many kinds of cells can use glycolysis alone to produce small amounts of ATP – But a cell must have a way of replenishing or

regenerating NAD+ (NADH NAD+)

Fermentation is an anaerobic alternative to aerobic respiration

• In alcoholic fermentation, pyruvic acid (pyruvate) is converted to CO2 and ethanol

Figure 6.15A

– This recycles NAD+ to keep glycolysis working

GLYCOLYSIS

2 Pyruvicacid

released

2 EthanolGlucose

Figure 6.15C

XO

Alcoholic Fermentation

• In lactic acid fermentation, pyruvic acid (pyruvate) is converted to lactic acid (lactate)– As in alcoholic fermentation, NAD+ is recycled

• Lactic acid fermentation is used to make cheese and yogurt

GLYCOLYSIS

2 Pyruvicacid

2 Lactic acidGlucose

Figure 6.15B

Lactic Acid Fermentation

• In addition to energy, cells need raw materials for growth and repair– Some are obtained directly from food– Others are made from intermediates in glycolysis

and the Krebs cycle

• Biosynthesis (making cell parts and organic compounds) uses ATP

Food molecules provide raw materials for biosynthesis

• All organisms have the ability to harvest energy from organic molecules– Plants, but not animals,

can also make these molecules from inorganic sources by the process of photosynthesis

The fuel for respiration ultimately comes from photosynthesis

Figure 6.18