CELLULAR RESPIRATION

Chapter 9Chemical Pathways

Honors Biology

BASIC NEED FOR ENERGY

Energy in Food:What is the difference between a: calorie(lower case c) and Calorie (upper

case C)?- A calorie is the amount of energy needed to raise the temperature of 1 gram of water by 1 degree C.

- A Calorie is a kilocalorie, or 1000 calories

For example, 1 gram of glucose releases 3811 calories, on a food label 3.8 Calories

BASIC NEED FOR ENERGYEnergy in Food: The reason we eat is to get energy We get carbohydrates from our food

which are broken into GlucoseOrganisms cannot use glucose directly, it

must be broken down into smaller units…… ATP This process in living things begins with glycolysis.

If oxygen is present, glycolysis is followed by the Krebs Cycle and electron transport chain – This is called Cellular Respiration

AN OVERVIEW:CELLULAR RESPIRATION

The equation for cellular respiration is exactly the opposite of photosynthesis.

Equation: 6O2 + C6H12O6 6CO2 + 6H2O and energy

BREAKING DOWN ENERGY SLOWLY:

Glucose needs to be broken down in small steps so that energy is not wasted.

FIRST STEP: GLYCOLYSIS

Definition: The process of breaking the glucose in half to form 2 molecules of pyruvate, a 3 carbon chain.

Uses 2 ATP to start reaction Produces 4 ATP and 2 NADH Occurs in the Cytosol (not

mitochondria)

What is the first step of Cellular respiration? Glycolysis

Where does it occur? Cytosol

What goes into glycolysis? Glucose

What comes out of glycolysis? 2 pyruvate, 2 ATP, and 2 NADH

GLYCOLYSIS Does not require oxygen Very Fast – thousands of ATP

produced in milliseconds Stops when it runs out of

NAD+ (electron carrier) If oxygen is available:

Cellular respiration starts If oxygen is NOT available, to

make more NAD+, your body goes through fermentation.

This way ATP can be made even without Oxygen.

WHY USE ATP IN GLYCOLYSIS IF YOU WANT ATP?

You have to use a little energy to make even more energy.

Like a bank, you put money in to earn interest.

Net ATP gained per glucose molecule=2Animation

Pyruvate molecules

Glucose

FERMENTATION Fermentation is releasing energy in the

absence of oxygen. It is an ANAEROBIC process.

Ultimately it allows NADH to be converted to NAD+, allowing glycolysis to continue.

There are two main types of fermentation Alcoholic Fermentation Lactic Acid Fermentation

ALCOHLIC FERMENTATION

ALCOHOLIC FERMENTATION Alcoholic fermentation is found in

Yeasts, and a few other microorganisms. The equation is:Pyruvic acid + NADH alcohol + CO2 +

NAD+

Note: Carbon Dioxide is also produced, so when yeast conducts fermentation, there is the release of carbon dioxide as well as alcohol.

ALCOHOLIC FERMENTATION

Alcoholic fermentation diagram

ALCOHLIC FERMENTATION

LACTIC ACID FERMENTATION

LACTIC ACID FERMENTATION Pyruvic acid from glycolysis can be converted to lactic

acid.

This conversion regenerates NAD+ for glycolysis to continue

The equation is:Pyruvic acid + NADH lactic acid + NAD+

Lactic acid fermentation is used by muscles when they run out of oxygen, ultimately causing soreness.

Lactic acid is also created by unicellular organisms in the production of cheese, pickles, kimchi and other foods.

LACTIC ACID FERMENTATION

Lactic Acid fermentation diagram

Pyruvate

KREBS CYCLE AND ELECTRON TRANSPORT After glycolysis, 90% of chemical energy

originally in glucose still remains locked in pyruvic acid

O2 is one of the most powerful electron acceptors and will help release the rest of the 90%

If O2 is available to the cell, pyruvic acid heads to Krebs Cycle after glycolysis

Krebs Cycle breaks pyruvic acid into CO2

KREBS CYCLE Where does it occur: Mitochondria It requires oxygen – it is AEROBIC It is also known as the Citric Acid Cycle

KREBS CYCLE1. Pyruvic acid enters mitochondria2. 1 carbon becomes part of CO2

and NAD+ becomes NADH3. The other 2 carbons join

coenzyme A to form acetyl-CoA4. Acetyl-CoA adds to a 4-carbon

molecule producing citric acid

Animation

KREBS CYCLE5. The citric acid is broken down to

a 5-carbon then 4- carbon molecule

6. 2 CO2 molecules are released

7. Electrons join NAD+ and FAD to become NADH and FADH2

8. 1 ATP made

So far, from 1 glucoseGlycolysis produced: 2 NADH and 2 ATPKrebs Cycle produced: 8 NADH and 2 FADH2 and 2 ATP

Animation

KREBS CYCLE

Think: Does the CO2 that we breathe out come from the O2 we breathe in?

KREBS CYCLE

KREBS CYCLEWhat happens to the Krebs cycle products?

Carbon Dioxide is released to the atmosphere

ATP is used for cellular activities

NADH and FADH2 are used in the electron transport chain (next step) to produce large amounts of ATP

ELECTRON TRANSPORT CHAIN Uses the high energy electrons

from the Krebs cycle to convert ADP into ATP

ELECTRON TRANSPORT CHAIN Where does it occur: Inner

membrane of the Mitochondria It requires oxygen – it is AEROBIC

ELECTRON TRANSPORT CHAIN1. NADH and FADH transfer

electrons to carrier proteins2. The electrons help transport H+

across membrane 3. Electrons move down the chain,

allowing more H+ to move across4. At the end of the chain, O2

accepts electrons and left over H+, creating water, H2O

Animation

ELECTRON TRANSPORT CHAIN

ELECTRON TRANSPORT CHAIN5. The H+ builds on the outside

of the membrane 6. The H+ moves through ATP

synthase, spinning the protein7. Each rotation charges an ADP,

attaches a phosphate, and creates ATP

Animation

CELLULAR RESPIRATION TOTALS

So far, from 1 glucoseGlycolysis: 2 ATP

Krebs Cycle: 2 ATP

Electron Transport: 32 ATP

Totals: 36 ATP from 1 glucose molecule

This is 38% efficiencyThe rest of the energy is released as heat

ENERGY USE BY HUMANSCells contains small amounts of ready ATP- About 5 seconds worth

After that, your body uses lactic acid formation- This lasts for about 90 seconds- You breathe hard to get rid of the lactic acid buildup

For exercise longer than 90 seconds, cellular respiration is used- This is a slow method to generate ATP- Glycogen (a form of carbohydrate) is used for the first 15-20

minutes of cellular respiration- After that other molecules, such as fats, are broken down