Cellular Respiration

**Food provides life with the chemical building blocks need to

grow and reproduce.**

CalorieThe amount of

energy needed to raise the

temperature of 1 gram of water 1oC.

On food labels, “Calorie” is a

kilocalorie of 1000 calories.

Glycolysis

Begins process of respiration and releases a small amount of energy

that leads to 2 other processes that release A LOT of energy.

It is the beginning process of our food “burning” to release energy.

What is Cellular Respiration?

The process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.

There Are 3 Steps: Glycolysis, Kreb’s Cycle, Electron Transport

Equation

6 O2 + C6H12O6 6 CO2 + 6 H2O + ATP

Glycolysis

It is a process in which one molecule of glucose is

broken in half, producing two molecules of pyruvic

acid and a 3 – carbon sugar.

ATP & Glycolysis

The process releases energy, but needs a boost to get

started.

It takes 2 ATP’s to start glycolysis.

4 ATP’s are produced at the end.

NET ATP after glycolysis = __________

NADH ProductionOne of the reactions of

glycolysis removes four high energy electrons and passes

them to NAD+.

NADH then holds those electrons with their energy.

Energy Output of Glycolysis

The process is so fast, it can produce thousands of ATP in milliseconds.

Glycolysis doesn’t require oxygen, so it can supply chemical energy

to cells when oxygen is not available.

PROBLEM:

All the NAD+ becomes filled up with electrons and cells run out.

Steps of Glycolysis

Step 1

Two phosphates are added to glucose to

with an ATP investment of 2

molecules.

Step 2

The 2 phosphate sugar molecule is then split to form 2, 3 carbon

molecules.

Step 3

The two phosphate, 3 carbon molecules are then converted to 2

pyruvate (pyruvic acid). As this occurs electrons are transferred to NAD+ to form NADH. ATP is also

formed.

Result

Two Pyruvates (with a lot of stored energy left)

A net of 2 ATP’s

Kreb’s Cycle

After glycolysis, 90% of of the chemical energy from glucose is still left.

For the Kreb’s Cycle, oxygen is necessary.

The pyruvic acid will be further broken down into CO2 in a series of energy extracting steps.

Step 1 (Citric Acid Production)

The pyruvic acid enters the mitochondria and loses a CO2 molecule.

The 2 carbons left attach to coenzyme A to from Acetyl CoA.

The Acetyl CoA is actually what enters the Krebs Cycle.

Step 1 -cont-

The 2 C acetyl CoA then joins with a 4 carbon molecule to make Citric Acid.

Step 2

The citric acid is broken down, releasing more CO2.

One ATP is produced. ⌘

3 NADH and 1 FADH is converted to FADH2

There is now a 4 carbon molecule left.

The Krebs Cycle must occur 2 times in order to break down both of the pyruvic aicds that were created

during glycolysis.

NADH & FADH2

Both these molecules are electron carriers that trap most of the energy from the Krebs cycle.

Electron TransportOccurs in inner Membrane of Mitochondria

First StepThe electrons from the original glucose

molecule are moved to an electron transport chain using NADH.

(Electrons move to carriers that they have a stronger attraction for.)

Step 1 – cont. –

These transfers along the chain release energy. This energy is used to pump H+ ions into the

inner membrane of the mitochondria.

The electrons in the chain are “pulled” toward oxygen and once there the oxygen, electrons

and hydrogen combine to form water.

Step 2Those H+ ions then rush

back out of the membrane through ATP

synthases.This energy is used to then to convert ADP to

ATP. Up to 36 ATP’s can be made from one glucose

molecule.

Total ATP’s Produced 36 ATP Molecules For 1 Glucose

Molecule