Cellular Respiration

Biology Biology Science DepartmentScience DepartmentDeerfield High SchoolDeerfield High School

Cellular RespirationCellular Respiration

pp. 174-178


Cellular Respiration

Cellular respiration is the process by which glucose (C6H12O6) is broken down to release energy for making ATP, another form of chemical energy.


Cellular Respiration – Equation

C6H12O6 + 6 O2 6 H2O + 6 CO2 + 36 ATP

foodfood(glucose, a carbohydrate)(glucose, a carbohydrate)

oxygenoxygen waterwater carboncarbondioxidedioxide


BioTheme: Interdependence!

Photosynthesis:

6 H2O + 6 CO2 + energy (sun) → C6H12O6 + 6 O2

Cellular Respiration:

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


The BIG Question is…

Do only animals respire?

Or do plants respire too?

Only plants perform photosynthesis Plants AND animals perform cellular

respiration!

(Can you explain why??)


Cellular Respiration Overview

Three Stages:1. Glycolysis (occurs in both aerobic and

anaerobic)

2. Krebs Cycle3. Electron Transport Chain

The Main form of Energy produced = ATP


Significant ATP Production

Aerobic cellular respiration releases energy SLOWLY, using oxygen to convert ONE molecule of glucose to 36 ATP!


GlucoseGlycolysis

Cytoplasm

Pyruvic acid

Electrons carried in NADH

Krebs Cycle

Electrons carried in

NADH and FADH2 Electron

Transport Chain

Mitochondrion

Cellular Respiration: An Overview

Mitochondrion


Glycolysis

Glyco = Glucose lysis = Breakdown Occurs in the cytoplasm of the cell Molecules of GLUCOSE are broken

down into 2 molecules of Pyruvic Acid. Cell must use (invest) 2 ATP Products:– 2 pyruvic acid– 2 ATP– 2 NADH


Glycolysis

GlucosePyruvic Acid

Pyruvic Acid

To the Electron Transport Chain


Site of Cell Respiration The mitochondria is the

organelle where the final stages of cellular respiration occurs.– Krebs Cycle– Electron Transport

Chain


Krebs Cycle

Aerobic Process = Only if oxygen is present Occurs in the MATRIX of the mitochondria Pyruvic Acid from Glycolysis enters to form– 2 ATP– 6 NADH– 2 FADH2

– CO2 (which is released when we exhale!!)

AKA Citric Acid Cycle


Krebs Cycle


Electron Transport Chain

Energy carrier molecules produced during Glycolysis and the Kreb’s Cycle enter the ETC

– NADH– FADH2

Occurs in the folds of the Inner Membrane of the Mitochondria (Cristae)

The electrons are passed down a chain of proteins until they reach the final electron acceptor…..oxygen!– So this step is aerobic (requires oxygen)

The ETC produces 32 ATP and H2O


Cellular Respiration Flowchart

Glucose(C6H1206)

+Oxygen

(02)

GlycolysisKrebsCycle

ElectronTransport

Chain

Carbon Dioxide(CO2)

+Water(H2O)


Cellular Respiration (anaerobic)

What happens when cells don’t have enough oxygen? Some organisms live in an oxygen-free environment.

How do they get their energy?The Kreb’s Cycle and Electron Transport

Chain can’t function!!

These are anaerobic conditions!!


Minimal ATP Production

In the absence of oxygen, anaerobic respiration only releases 2 ATP for each molecule of glucose broken down.


Cellular Respiration (anaerobic)

Anaerobic respiration is also called fermentation, or the process by which energy is released from glucose when oxygen is NOT available.

This process allows organisms to continue to produce energy until oxygen is available.

However, this process only releases 2 ATP per molecule of glucose.


Fermentation

Releases less energy than aerobic respiration

Occurs in the Cytoplasm– just like glycolysis

Fermentation– A series of reactions that convert NADH

(from glycolysis) back into NAD allowing glycolysis to keep producing a small amount of ATP


Alcoholic Fermentation

Anaerobic way of converting energy for yeast and other microorganisms

Glucose broken down to produce alcohol, CO2 and energy (ATP)

C6H12O6 + pyruvic acid ethanol + CO2 + 2 ATP

EX: baking bread with yeast (dough rises) fermenting wine & beer


Lactic Acid Fermentation

Anaerobic way of converting energy in animal cells and some microorganisms

Glucose broken down to produce lactic acid, CO2 and energy (ATP)

C6H12O6 + pyruvic acid lactic acid + 2 ATP

EX: muscle cells during strenuous exercise fermenting cheese, yogurt, sour cream


Lactic Acid Fermentation

– Occurs in bacteria (unicellular organisms)– This is how cheese, yogurt, and pickles are

made.

– Occurs in muscles during rapid exercise–When your body runs out of oxygen your muscle

cells must produce some ATP using fermentation and glycolysis

– Lactic Acid build-up causes muscle soreness or burning after intense activity.

Pyruvic Acid + NADH lactic acid + NAD+


Strenuous Exercise

Lactic acid is produced by your muscle cells during rapid exercise when the body cannot supply enough O2 to tissues.

Without enough O2, the body is NOT able to produce all of the ATP that is required.

The buildup of lactic acid can cause painful burning in your muscles


Fermentation Summary

Glycolysis: Glucose 2 Pyruvic Acid Fermentation: 2 Pyruvic Acid ? or ?


Chemical Pathways

Glucose

Glycolysis Krebs cycle

Electrontransport

Fermentation (without oxygen)

Alcohol or Lactic Acid


Comparing ATP Production

First, your body breaks down glucose through aerobic respiration to produce 36 ATP per glucose molecule; however, this is a slow process.

When muscle cells cannot get enough O2 they break down glucose through lactic acid fermentation to produce 2 ATP per glucose…

Therefore, AEROBIC RESPIRATION is much more efficient in terms of ATP production – 36 ATP compared to 2 ATP!


Aerobic Training

Ex: long runs, biking, swimming

Can increase the size and number of mitochondria in muscle cells

Can increase the delivery of O2 to muscles by improving the heart and lungs


Anaerobic Training

Ex: sprints, strides, quick bursts of energy

Increase the glycogen levels in the muscles

Increase body’s tolerance to lactic acid

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Cellular Respiration