Bellringer-April 21, 2014

FILL IN THE LETTERS

Overview of Cellular Respiration

H. BiologyMs. Kim

Energy Flows into ecosystems as sunlight and leaves as heat

Light energy

ECOSYSTEM

CO2 + H2O

Photosynthesisin chloroplasts

Cellular respirationin mitochondria

Organicmolecules + O2

ATP

powers most cellular work

Heatenergy http://wps.aw.com/bc_campbell_biology_7/

Carbon Cycle

Reminder….Anabolic pathways (“A” for add together)

Build molecules from simpler ones (ex: photosynthesis)

Consume energy (endergonic)Catabolic pathways (“C” for cut in parts)

Break down complex molecules into simpler compounds (ex: cell respiration)

Release energy (exergonic)

Cellular respiration

Most efficient catabolic pathwayConsumes O2 and organic

molecules (ex: glucose)Yields ATP To keep working cells

must regenerate ATP

Catabolic pathways yield energy by oxidizing organic fuels

The breakdown of organic molecules is exergonic

One catabolic process, fermentationIs a partial degradation of sugars that occurs

without oxygen

Another example is cellular respiration

Cellular respiration

Occurs in mitochondria similar to combustion of gas in an engine after

O2 is mixed with hydrocarbon fuel.Food = fuel for respiration. The exhaust =CO2 and H2O.

The overall process is:organic compounds + O2 CO2 + H2O + energy

(ATP + heat)Carbohydrates, fats, and proteins can all be used as

the fuel, but most useful is glucose.

Mitochondria

Intermembrane Space

• Powerhouse of the cell!• The organelle responsible for cellular respiration

• The Krebs Cycle and ETC take place here ATP is produced here!

• It is a double membrane with the inner membrane highly folded (to increase the surface area and make the mitochondria more efficient).

Mitochondrion Structure

Mitochondrion Structure• Outer membrane – similar to plasma

membrane; contains integral proteins• Inner membrane- NOT permeable to ions

(needs help to cross); there is a membrane potential across the inner membrane; contains ATP synthase

• Cristae – large surface area due to folding• Matrix - gel-like in middle or lumen; many

contains enzymes for cellular respiration

RECALL…Redox ReactionsCatabolic pathways yield energy

Due to the transfer of electronsRedox reactions

Transfer e-’s from one reactant to another by oxidation and reductionIn oxidation

Substance loses e-s (it’s oxidized)In reduction

Substance receives e-s (it’s reduced)

Examples of redox reactions

Na + Cl Na+ + Cl–

becomes oxidized(loses electron)

becomes reduced(gains electron)

Xe- + Y X + Ye-

**energy must be added to remove e-X = e- donor = reducing agent and reduces Y.

Y = e- recipient = oxidizing agent and oxidizes X.

Oxidation of Organic Fuel Molecules During Cellular Respiration

• During cellular respiration– Glucose is oxidized – oxygen is reduced– E-’s lose potential energy energy is released

C6H12O6 + 6O2 6CO2 + 6H2O + Energybecomes oxidized

becomes reduced

http://student.ccbcmd.edu/~gkaiser/biotutorials/cellresp/ets_flash.html

Electrons are not transferred directly to oxygen but are passed first to a coenzyme called NAD+ or FAD

NAD+

HO

OO O–

OO O–

O

O

O

P

P

CH2

CH2

HO OHH

HHO OH

HO

H

H

N+

C NH2

HN

H

NH2

N

N

Nicotinamide(oxidized form)

NH2+ 2[H](from food)

Dehydrogenase

Reduction of NAD+

Oxidation of NADH

2 e– + 2 H+

2 e– + H+

NADH

OH H

N

C +

Nicotinamide(reduced form)

N

Figure 9.4

NAD+ and FAD= e- acceptor and oxidating agent

2 H 1/2 O2

(from food via NADH)

2 H+ + 2 e–

2 H+

2 e–

H2O

1/2 O2

Controlled release of energy

for synthesis of

ATP ATP

ATP

ATP

Electron transport chain

Free

ene

rgy,

G

(b) Cellular respiration

+

Electron Flow =food NADH/FADH2 ETC oxygen

Cellular Respiration – Background info• Equation – C6H12O6 + 6O2 → 6CO2 + 6 H2O + 36 or 38 ATP

-When food is broken down, energy is released gradually and stored in ATP.

-Respiration is done by BOTH plants and animals

The Stages of Cellular Respiration

• Respiration is a cumulative process of 3 metabolic stages

1. Glycolysis2. Kreb’s Cycle (The citric acid cycle)

3. Electron Transport Chain (Oxidative phosphorylation)

The 3 StagesGlycolysis

Breaks down glucose into 2 molecules of pyruvateMakes NADH

Kreb’s Cycle (Citric acid cycle)Completes the breakdown of glucoseMakes NADH and FADH2

Electron Transport Chain (Oxidative phosphorylation)Driven by the electron transport chainGenerates ATP

General overview – Cellular Respiration1.Glycolysis:• In the cytosol• Anaerobic• Turns glucose to 2 pyruvate net gain of 2 ATP and 2 NADH

2. Krebs:• In the mitochondrial matrix • Makes little ATP, NADH, and FADH2 (electron taxis) • Passes e- to ETC

3. ETC → uses chemiosmosis to make LOTS of ATP

Exit Slip-April 21, 2014• Draw a cycle of the ecosystem between

photosynthesis and cellular respiration. • Include the following: photosynthesis, carbon

dioxide, light energy, heat energy, oxygen, glucose, water, and ATP.