Cellular Respiration

Advanced Biology Cellular Respiration

Energy Flow

Light energy

ECOSYSTEM



Energy flows into an ecosystem as sunlight and leaves as heat

Photosynthesis in chloroplasts CO2 + H2O

Organic molecules

Cellular respiration in mitochondria

ATP powers most cellular work

Heat energy

+ O2

Cellular Respiration 

In cellular respiration the mitochondria break down (reduce) glucose releasing its stored energy and producing CO2 and H2O as wastes



The energy is then stored in ATP molecules

C6H12O6 + 6O2

Oxygen Monosacchari produced by de produced plants during by plants photosynthes is

6CO2 + 6H2O + Energy

Waste CO2 is used by plants to make more sugars

Stored in ATP

6.1

Redox Reactions  Redox

reactions

– Transfer electrons from one reactant to another by oxidation and reduction  In

oxidation

– A substance loses electrons, or is oxidized  In

reduction

– A substance gains electrons, or is reduced 6.2

Redox Reactions  Examples

of redox reactions: becomes oxidized (loses electron)

#1

Na

+

Cl

Na+

+

Cl–

becomes reduced (gains electron)

becomes oxidized

#2

C6H12O6 + 6O2

6CO2 + 6H2O + Energy becomes reduced

6.2

Cellular Respiration

NAD+ H







Cellular respiration oxidizes glucose in a series of steps NAD+ accepts electrons from the oxidation of glucose NADH is the reduced form of NAD+

NH2

C

CH2

O O P

O

O

N+ Nicotinamide (oxidized form)

–

O

H H O P O– HO OH CH2HO O N H N O H HO

6.3

O

H OH

NH2 N N

H

Electron Transport Chains From food via NADH

6.4

Uncontrolled Reaction

Cellular Respiration

Making ATP  Oxidative

phosphorylation – ATP is

made as the result of an electron transport chain

 Substrate-level

phosphorylation – ATP

is made directly when an enzyme transfers a P (phosphate) to ADP

6.5

Review  What

particles store the energy in glucose?  What molecule carries electrons?  What molecule gains and stores the energy from the electrons?

The Cell Nucleus

Endoplasmic Reticulum Mitochondria

Golgi Apparatus Cytoplasm Cell Membrane

3 Phases of Cellular Respiration  Glycolysis

– Breaks down glucose into two molecules of pyruvate  The

citric acid cycle

– Completes the breakdown of glucose  Oxidative

phosphorylation

– Is driven by the electron transport chain – Generates ATP 6.6

3 Phases of Cellular Respiration Electrons carried via NADH

Electrons carried via NADH and FADH2

Citric acid cycle

Glycolysis Glucose

Pyruvate

Oxidative phosphorylation: electron transport and chemiosmosis

Mitochondrion

ATP

6.6

ATP

ATP

Glycolysis  Occurs

in the cytoplasm of the cell

 Means

“splitting of sugar”

 Breaks

down glucose into pyruvate

1 6-Carbon glucose

6.7

2 3-Carbon sugar pyruvates

2 3-Carbon

Investment and Payoff 

ATP is required as activation energy to begin the reactions of glucolysis



ATP is then produced in the payoff phase along with 2NADH

6.8

Glycolysis – In Detail #1 – Two ATP are added to glucose to produce fructose 1,6bisphosphate

#2 – Fructose 1,6bisphosphate is split into two molecules of Glyceraldehyde 3Phosphate

#3 – The two G3P’s are further oxidized producing 4 ATP (2 Net) and 2 NADH

#4 – G3P has now been completely oxidized to pyruvate

6.9



Before the citric acid cycle can begin pyruvate must first be converted to acetyl CoA CYTOSOL MITOCHONDRION Pyruvate

NAD+

O– C

O

C

O

NADH

+ H+

2

1

3

Acetyl CoA S

CoA

C

O

CH3

CH3 CO2

Coenzyme A

Transport protein

3C 6.10

2C CO2

NADH

The Citric Acid Cycle 

Products from one acetyl CoA – – – –

= ATP

3 NADH 1 ATP 2 1 FADH 2 2 CO

6.11

Review  How

many carbons are left from 1 glucose at the beginning of the citric acid cycle?

Electron Transport 



Electron slide



NADH and FADH 2 provide electrons for the chain The electrons transfer is exergonic because they lose energy at each step Where does this energy go? 6.12

Electron Transport  



Electrons from NADH and FADH are passed to oxygen, forming water Electron transfer causes protein complexes to pump H+ from the mitochondrial matrix to the intermembrane space The resulting H+ gradient – – –

Stores energy Drives chemiosmosis in ATP synthase Is referred to as a proton-motive force

6.12/6.13

The Yield Electron shuttles span membrane

CYTOSOL



MITOCHONDRION

2 NADH or

2 FADH There are three main processes in this2 metabolic enterprise 2 NADH

2 NADH

Glycolysis Glucose

2 Pyruvate

2 Acetyl CoA

+ 2 ATP

Citric acid cycle

+ 2 ATP

by substrate-level phosphorylation

Maximum per glucose:

6.14

6 NADH

by substrate-level phosphorylation

About 36 or 38 ATP

2 FADH2

Oxidative phosphorylation: electron transport and chemiosmosis

+ about 32 or 34 ATP by oxidative phosphorylation, depending on which shuttle transports electrons from NADH in cytosol

Making ATP without Oxygen  Cellular

respiration

– Relies on oxygen to produce ATP using the electron transport chain  Fermentation

– Allows cells to produce ATP in the absence of oxygen

6.15



Fermentation or Respiration?

Pyruvate is a key juncture in Glucose catabolism CYTOSOL

Pyruvate

anaerobic

No O2 present Fermentation

Alcohol Fermentatio n

MITOCHONDRION

Ethanol

Acetyl CoA

or

lactate

Lactic Acid Fermentatio n

O2 present Cellular respiration

Citric acid cycle

aerobic

P1

2 ADP + 2 Glucose

2 ATP

O– C O C O

Glycolysis

Lactic acid fermentation



CH3 2 Pyruvate

2 NAD H H C OH CH3 2 Ethanol

+

2 NADH

– Pyruvate is reduced, using NADH, to form lactate as a waste product

2 CO2 H C O CH3

Glucose



P1

2 ADP + 2

2 Acetaldehyde

2 ATP

Glycolysis

O–

Alcohol fermentation – Pyruvate is converted to ethanol in two steps, one of which releases CO2

6.16

C O 2 NAD+

O C O H

C

OH

CH3 2 Lactate

2 NADH

C O CH3

2 Pyruvate

Proteins

Carbohydrates

Amino acids

Sugars

Fats



Glycolysis and the citric acid cycle connect to many other metabolic pathways



These pathways funnel electrons from many kinds of organic molecules into cellular respiration



Organisms use these organic molecules to build 6.17 other substances or

Glycerol Fatty acids

Glycolysis Glucose

Glyceraldehyde-3- P NH3

Pyruvate Acetyl CoA

Citric acid cycle

Oxidative phosphorylation