Cellular Respiration (Chapter 9). Energy source Autotrophs: Producers Plants, algae and some...

Cellular Respiration (Chapter 9)

Energy source Autotrophs: Producers Plants, algae and some bacteria Make own organic molecules Heterotrophs: Consumers

Energy All activities an organism performs

requires energy

Cellular respiration

C6H12O6 + 6 O2

---> 6 CO2 + 6 H2O + ATP

Cellular respiration

Cellular Respiration Catabolic Enzymes break down substances Harvest energy from C-H bonds Or other chemical bonds

Organic compounds + oxygen ⇨ Carbon Dioxide + water +

energy

Cellular respiration Aerobic respiration Chemical energy is harvested Presence of oxygen Anaerobic respiration Process occurs without oxygen Fermentation

Anaerobic Glucose to lactate (muscle cells) Glucose to alcohol (yeast cells) Does not yield as much energy

Cellular Respiration Exergonic -686kcal/mole (-2,870kJ/mole) Redox reaction Glucose is oxidized, oxygen is reduced Energy stored in glucose makes ATP 38 ATP generated ATP stores energy for use in cellular

functions

Redox reaction

becomes oxidized

becomes reduced

Vocabulary NAD/NADH FAD ETC Phosphorylation Chemiosmosis ATP Synthase

NAD & NADH NAD: Nicotinamide adenine dinucleotide NAD+ oxidized form NADH reduced form NAD+ traps electrons from glucose Function as energy carrier

NAD & NADH Dehydrogenase (enzyme) Removes a pair of hydrogen atoms

from glucose Transfers one proton and 2

electrons to NAD+

H-C-OH + NAD+ ⇨ -C=O + NADH + H+

Used to make ATP

NAD+

2 e− + 2 H+

2[H](from food)

Nicotinamide(oxidized form)

Reduction of NAD+

2 e− + H+

NADH

Nicotinamide(reduced form)

Oxidation of NADHH+

H+

Dehydrogenase

FAD Flavin adenine dinucleotide Transfers electrons

Electron transport chain Located inner membrane of

mitochondria Plasma membrane (prokaryotes) Series of molecules (mostly

proteins)

Electron transport chain Electrons fall to oxygen In a series of energy releasing

steps High potential energy to low Energy released generates ATP

Electron transport chain

Fre

e en

erg

y, G

Controlledrelease ofenergy for

synthesis ofATP

2 H+ + 2 e–

2 H + 1/2 O2

(from food via NADH)

ATP

ATP

ATP

1/2 O22 H+

2 e–E

lectron

transp

ort

chain

H2O

Phosphorylation Addition of a phosphate group to a

molecule ATP is formed by a

phosphorylation reaction 1. Substrate-level phosphorylation 2. Oxidative phosphorylation

Substrate phosphorylation Enzyme transfers

a phosphate from a organic substrate molecule

ADP to make ATP Direct formation Glycolysis and

Krebs cycle

Oxidation phosphorylation Energy from

electron transport chain

Synthesis ATP Adds an

inorganic phosphate to ADP

Chemiosmosis Energy-coupling mechanism Energy stored in hydrogen ion

gradient across membrane Makes ATP from ADP

H+

2

H+

ADP + P i ATP

Chemiosmosis

ATPsynthase

ATP Synthase Enzyme helps make ATP Located in membrane Changes ADP to ATP Uses energy from a proton

gradient across membrane

INTERMEMBRANESPACE

RotorH+ Stator

Internal rod

Catalyticknob

ADP+P i

MITOCHONDRIALMATRIX

ATP

The Reactions (Cell Respiration)

Glycolysis Krebs cycle (citric acid cycle) Electron transport chain (oxidative

phosphorylation)

Cellular respiration

Glycolysis Happens in cytoplasm Starts with glucose Yields: 2 pyruvate (3 carbons) molecules 4 ATP (net of 2 ATP) & 2 NADH 10 enzyme catalyzed reactions to

complete

Glycolysis Every living organism can carry

out glycolysis Occur in aerobic & anaerobic Does not require oxygen Oxygen present the Krebs cycle

will begin

Glycolysis Part one (priming) First 5 reactions are endergonic 2 ATP molecules attach 2

phosphate groups to the glucose Produces a 6 carbon molecule

with 2 high energy phosphates attached

Glycolysis Part two (cleavage reactions) 6 carbon molecule is split into 2 3-carbon molecules each with a

phosphate (G3P)

Glycolysis Part three (energy harvesting

reactions) In two reactions 2- G3P molecules

are changed to pyruvate 4 ATP molecules are made (net of

2) An energy rich hydrogen is

harvested as NADH (2NADH)

GLYCOLYSIS: Energy Investment Phase

Glucose

GLYCOLYSIS: Energy Investment Phase

Glucose6-phosphate

ATP

ADPGlucose

Hexokinase

1

GLYCOLYSIS: Energy Investment Phase

Glucose6-phosphate

ATP

ADPGlucose

Hexokinase Phosphogluco-isomerase

Fructose6-phosphate

12

GLYCOLYSIS: Energy Investment Phase

3

Fructose6-phosphate

ATP

ADP

Fructose1,6-bisphosphate

Phospho-fructokinase

GLYCOLYSIS: Energy Investment Phase

34

5

Fructose6-phosphate

ATP

ADP

Glyceraldehyde3-phosphate (G3P)

Fructose1,6-bisphosphate

Dihydroxyacetonephosphate (DHAP)

Phospho-fructokinase

Aldolase

Isomerase

GLYCOLYSIS: Energy Investment Phase

ADP

Glucose6-phosphate

Fructose6-phosphate

ATP ATP

ADP

Glyceraldehyde3-phosphate (G3P)

Fructose1,6-bisphosphate

Dihydroxyacetonephosphate (DHAP)

Glucose

Hexokinase Phosphogluco-isomerase

Phospho-fructokinase

Aldolase

Isomerase

12

5

43

GLYCOLYSIS: Energy Payoff Phase

4

Glyceraldehyde3-phosphate (G3P)

Dihydroxyacetonephosphate (DHAP)

Aldolase

Isomerase

5 6

Triosephosphate

dehydrogenase

2 NAD+ 2 H+

NADH

2

2

2

2

1,3-Bisphospho-glycerate

GLYCOLYSIS: Energy Payoff Phase

4

Glyceraldehyde3-phosphate (G3P)

Dihydroxyacetonephosphate (DHAP)

Aldolase

Isomerase

5 67

Triosephosphate

dehydrogenase

2 NAD+ 2 H+

NADH

2

2

2

2

2 ADP

1,3-Bisphospho-glycerate

3-Phospho-glycerate

Phospho-glycerokinase

2

2

ATP

8 9

Phospho-glyceromutase

3-Phospho-glycerate

2-Phospho-glycerate

2 2 2

Enolase

Phosphoenol-pyruvate (PEP)

2 H2O

GLYCOLYSIS: Energy Payoff Phase

Figure 9.9bb-3

8 9 10

Phospho-glyceromutase

3-Phospho-glycerate

2-Phospho-glycerate

2 2 2

Enolase

Phosphoenol-pyruvate (PEP)

Pyruvate

Pyruvatekinase

2

2 ATPADP

2 H2O 2

GLYCOLYSIS: Energy Payoff Phase

GLYCOLYSIS: Energy Payoff Phase

Glycer-aldehyde

3-phosphate(G3P)

Triosephosphate

dehydrogenase

6 1,3-Bisphospho-glycerate

3-Phospho-glycerate

2-Phospho-glycerate

Phosphoenol-pyruvate (PEP)

Pyruvate

Phospho-glycerokinase

Phospho-glyceromutase

Enolase Pyruvatekinase

2 NAD+

7 89

10

2 NADH

+ 2 H+

2

2

2

2

2 2 22

2

22 H2OATP ATPADPADP

Electron shuttlesspan membrane

+ 2 ATP

2 NADHor

2 FADH2

GLYCOLYSIS

Glucose 2Pyruvate

2 NADH

Glycolysis Glucose

converted to pyruvate.

First half uses 2 ATP

Forms 2 separate G3P (glyceraldehyde 3-phosphate)

Glycolysis Second half

generates 4 ATP, 2 NADH & 2 pyruvate

Net results are 2 ATP, 2 NADH and 2 pyruvate

Takes place in the cytoplasm

Oxidation of pyruvate Pyruvate is changed into acetyl-

CoA First carboxyl group is removed Leaves as carbon dioxide 2 carbon molecule called acetate

remains

Oxidation of pyruvate Pyruvate dehydrogenase Multienzyme complex Combines acetate (acetyl group)

with a coenzyme called coenzyme A.

Product is acetyl-CoA Plus one NADH

Oxidation of pyruvate Pyruvate dehydrogenase Largest known enzyme 60 subunits Process occurs within mitochondria Acetyl-CoA is end product of the

break down of fats and proteins too

Fig. 9-10

CYTOSOL MITOCHONDRION

NAD+ NADH + H+

2

1 3

Pyruvate

Transport protein

CO2Coenzyme A

Acetyl CoA