AP Biology

Cellular Respiration Harvesting Chemical Energy

ATP

AP Biology

What’s the point?

The point is to make

ATP!

ATP

AP Biology

Chemical Energy: Food is to a cell (plant or animal), what gas is to a car.

AP Biology

Which Smiley Face has the most potential energy? Kinetic energy?

AP Biology

An overview of Cellular Respiration

2 ATP

34 ATP

AP Biology

B. Aerobically; efficient. Occurs in the mitochondria. ( used in Kreb’s & ETC)

AP Biology

Aerobic or anaerobic pathways? How do you know?

AP Biology

AP Biology

Where in a chemical bond is the potential energy? A) protons

B) neutrons C) electrons

*most biological redox rxns. have to do w/ the loss or gain of Hydrogen atoms and their electrons (e-); Potential Energy! *redox rxns. are always coupled; that is, when one molecule is oxidized, the other is reduced. “hand & glove”

AP Biology

*Liberated H atoms are transferred to other molecules by coenzymes " electron shuttle busses" 2 coenzymes commonly used by the cell: * NAD+ … derived from vitamin B niacin * FAD2+ ....derived from B2 riboflavin

AP Biology

H atom from chemical bonds. Have much Potential energy to

do WORK!

Oxidation - Reduction Rxn.

Remember:

AP Biology

Redox Football

Electron (H atom)

Which molecule is oxidized? Which is Reduced?

Where does the potential energy carried by NADH end up?

AP Biology

Where does the potential energy carried by NADH end up?

AP Biology

Energy Extraction Pathways

AP Biology

Coenzymes (vitamins) - are electron shuttle busses -

they lose & gain H(e-) atoms which are stripped from bonds of food molecules.

AP Biology

AP Biology

Conversions of the Metabolic Pathways- all foods have the

same fate…. The metabolic Mill!

proteins carbos fats

AP Biology

  Energy is stored in organic molecules   carbohydrates, fats, proteins

  Heterotrophs eat these organic molecules → food   digest organic molecules to get…

  raw materials for synthesis   fuels for energy

  controlled release of energy   “burning” fuels in a series of

step-by-step enzyme-controlled reactions

Harvesting stored energy:

AP Biology

AP Biology

 Glucose is the model  catabolism of glucose to produce ATP

fuel (carbohydrates)

COMBUSTION = making a lot of heat energy by burning fuels in one step

C6H12O6 6O2 ATP 6H2O 6CO2 → + + +

glucose + oxygen → energy + water + carbon dioxide

resp

iratio

n

+ heat

CO2 + H2O + heat

RESPIRATION = making ATP (& some heat) by burning fuels in many small steps

CO2 + H2O + ATP (+ heat)

ATP glucose

O2

O2

enzymes ATP

Harvesting stored energy:

AP Biology

How do we harvest energy from fuels?  Digest large molecules into smaller ones

 break bonds & move electrons from one molecule to another   as electrons move they “carry energy” with them   that energy is stored in another bond,

released as heat or harvested to make ATP

e-

+ + e-

+ – loses e- gains e- oxidized reduced

oxidation reduction

redox

e-

AP Biology

How do we move electrons in biology?  Moving electrons in living systems

 electrons cannot move alone in cells   electrons move as part of H atom  move H = move electrons

p e

+

H

+ H

+ – loses e- gains e- oxidized reduced

oxidation reduction

C6H12O6 6O2 6CO2 6H2O ATP → + + + oxidation

reduction H e-

AP Biology

Coupling oxidation & reduction:   REDOX reactions in respiration

  release energy as breakdown organic molecules   break C-C bonds   strip off electrons from C-H bonds by removing H atoms

 C6H12O6 → CO2 = the fuel has been oxidized   electrons attracted to more electronegative atoms

  in biology, the most electronegative atom?  O2 → H2O = oxygen has been reduced

  couple REDOX reactions & use the released energy to synthesize ATP

C6H12O6 6O2 6CO2 6H2O ATP → + + + oxidation

reduction

O2

AP Biology

Oxidation & reduction:  Oxidation

 adding O   removing H   loss of electrons   releases energy  exergonic

 Reduction   removing O  adding H  gain of electrons  stores energy  endergonic

C6H12O6 6O2 6CO2 6H2O ATP → + + + oxidation

reduction

AP Biology

Moving electrons in respiration:   Electron carriers move electrons by

shuttling H atoms around   NAD+ → NADH (reduced)   FAD+2 → FADH2 (reduced)

reducing power!

+ H reduction

oxidation

P O–

O–

O –O

P O–

O–

O –O

C C

O

NH2 N+

H

adenine

ribose sugar

phosphates

NAD+ nicotinamide Vitamin B3 niacin

P O–

O–

O –O

P O–

O–

O –O

C C

O

NH2 N+

H NADH

carries electrons as a reduced molecule

H

like $$ in the bank

AP Biology

NAD+ as an electron shuttle bus: NAD+

2 e− + 2 H+

2[H] (from food)

Nicotinamide (oxidized form)

Reduction of NAD+

2 e− + H+

NADH

Nicotinamide (reduced form)

Oxidation of NADH H+

H+

Dehydrogenase

H+

H+ H+

H+

H+ H+ H+ H+

H+

ATP

To mitochondrial

membranes (Proton Motive

Force)

AP Biology

  Electron carriers move electrons by shuttling H atoms around   NAD+ → NADH (reduced); Count the e- + proton(H+) = 1 H atom

✔

✔

✔

AP Biology

Overview of cellular respiration:   4 metabolic stages

 Anaerobic respiration 1. Glycolysis

 respiration without O2   in cytosol

 Aerobic respiration  respiration using O2

  in mitochondria 2. Pyruvate oxidation 3. Krebs cycle 4. Oxidative phosphorylation & ETC

C6H12O6 6O2 ATP 6H2O 6CO2 → + + + (+ heat)

Substrate-level Phosphorylation

Substrate-level Phosphorylation

Oxidative Phosphorylation

~90% of ATP

AP Biology

An overview of cellular respiration:

Electrons via NADH

Electrons via NADH and FADH2

ATP ATP ATP

CYTOSOL MITOCHONDRION

Substrate-level Substrate-level Oxidative (Powered by redox)

GLYCOLYSIS PYRUVATE OXIDATION CITRIC

ACID CYCLE

OXIDATIVE PHOSPHORYLATION

(Electron transport and chemiosmosis)

Acetyl CoA Glucose Pyruvate

Oxidative phosphorylation accounts for almost 90% of the ATP generated by cellular respiration!

AP Biology

  A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation.

Enzyme Enzyme

Substrate

Product

ATP

ADP

P

Substrate-level Phosphorylation

Substrate-level Phosphorylation

AP Biology

Example: Substrate-level phosphorylation during Glycolysis

GLYCOLYSIS: Energy Payoff Phase

Glycer- aldehyde

3-phosphate (G3P)

Triose phosphate

dehydrogenase

6 1,3-Bisphospho- glycerate

3-Phospho- glycerate

2-Phospho- glycerate

Phosphoenol- pyruvate (PEP)

Pyruvate

Phospho- glycerokinase

Phospho- glyceromutase

Enolase Pyruvate kinase

2 NAD+

7 8 9 10

2 NADH + 2 H+

2

2

2 2

2 2 2 2

2

2 2 H2O ATP ATP ADP ADP

Which step #(s) is ATP made by Substrate-level phosphorylation?

AP Biology

What’s the point?

The point is to make

ATP!

ATP

AP Biology

 ATP synthase enzyme  H+ flows through it

  conformational changes

  bond Pi to ADP to make ATP

 set up a H+ gradient   allow the H+ to flow

down concentration gradient through ATP synthase

 ADP + Pi → ATP H+

H+ H+

H+

H+ H+ H+ H+

H+

ATP ADP P +

But… How is the proton (H+) gradient formed?

And how do we do that?

AP Biology 2006-2007 H+

H+ H+

H+

H+ H+ H+ H+

H+

ATP

Got to wait until the sequel!

Got the Energy? Ask Questions!

ADP P +