Cellular Respiration . - PowerPoint Presentation

Slide1

Cellular Respiration

.

What is Cellular Respiration???

A Famous scientist once said “Cellular Respiration is in my opinion, the most important biochemical reaction in Heterotrophic systems”

Me (Just now)

Cellular Respiration

is the mechanism in which we derive energy from what we eat.

All

Heterotrophs

use cellular respiration to obtain energy.

Most

Autotrophs

use photosynthesis to obtain energy.

Cellular respiration is the

inverse

of photosynthesis.

Photosynthesis vs. Cellular Respiration

Photosynthesis

Cellular Respiration

Cellular Respiration

The process of Cellular Respiration occurs in 3-4 steps.

1)

Glycolysis

2) Krebs Cycle

3)

Eletron

Transport Chain

1) Glycolysis

Gluc

- comes from the Greek word meaning Sweet.

Cose

-

we put at the end of words to signify Sugars.

Lyses

- means to break down. This process occurs in the cell’s Cytoplasm.

Glycolysis- is the process in which one molecule of glucose (a 6 carbon compound) is broken in half, producing two molecules of pyruvic acid (a 3-carbon compound) , 2 ATPs and 2 NADH bi products.

This is an

Anaerobic Process

(no oxygen required) this means

glycolysis

can provide energy to the cell when oxygen is not available.

Even though

glycolysis

is an energy-releasing process,

the cell needs to put in a little energy to get things going.

At the pathway's beginning, 2 molecules of ATP are used up.

Although the cell puts 2 ATP molecules to get

glycolysis

going,

when

glycolysis

is complete, 4 ATP molecules have been produced. This gives the cell a net gain of 2 ATP molecules.

Catalyzed reactions produce NADH. NADH holds the electrons until they can be transferred to other molecules. By doing this, NAD

+

helps to pass energy from glucose to other pathways in the cell.

Problems with Glycolysis

Although the energy production from

glycolysis

is small,

2 Net ATP’s

are formed (used 2 ATP’s and generated 4) and

2 NADH

, the process is so fast that cells can produce thousands of ATP molecules in just a few milliseconds. However, when a cell generates large amounts of ATP from glycolysis, it runs into a problem. In just a few seconds, all of the cell's available NAD+ molecules are filled up with electrons. Without NAD

+, the cell cannot keep glycolysis going, and ATP production stops.

2) Kreb’s

Cycle

The Krebs cycle is named after Hans Krebs, the British biochemist who demonstrated its existence in 1937.

To extract the rest of the energy stored in electrons from

glycolysis

, the cell turns to one of the world's most powerful electron acceptors ---

Oxygen!!!

Oxygen is required for the final steps of cellular respiration. Because the pathways of cellular respiration require oxygen, they are said to be aerobic.This process occurs in the matrix of mitochondria

.

Kreb’s

Cycle preparation

Pyruvic

Acid Oxidation

As we remember from

glycolysis

glucose was

lysed

to make 2

pyruvic

acid molecules.

Each

pyruvic

acid molecules is oxidized meaning 1 carbon is taken away.

This makes a 2 carbon molecules called Acetyl

CoA

. This process also reduces NAD+ to NADH

All of this is

catalysed

by

Enzymes

!! Proteins that bring things together in the right way so they can react.

At the end of

pyruvic

acid oxidation

1 NADH

is Produced

Once Acetyl

CoA

and NADH are produced the

Kreb’s

Cycle can begin!

Remember before

Kreb’s

cycle

pyruvate

is oxidized and forms 2 carbon Acetyl

CoA

and produces

1 NADH.

Next Acetyl

CoA

merges with a

4 carbon molecule

to form 6 carbon Citric Acid.

2

Carbon molecule +

4

carbon molecule

= 6 carbon

Citric Acid

.

1 carbon is sliced off and

1

NAD+ is reduced to

NADH

.

Now we are left with a 5 carbon molecule and again a carbon molecule is sliced off.

During this process

1 ATP

and

1 NADH

are produced.

Tada!!! We are back to a

4 Carbon Molecule :D

1 FADH

and

1 NADH

are produced and the Krebs Cycle starts all over again.

Le’s add them up!

1 NADH

From

Pyruvate

Oxidation

3 NADH

1 ATP

1 FADH

2

From Krebs

(x 2 for each

Pyruvic

acid)

FADH

and

NADH

are converted to

ATP

later in the

Electron Transport Chain

What is happening to the Carbon???

It becomes CO

2

when it attaches to oxygen then they leave your system as you exhale. Every time the Krebs cycle runs you generate 3 molecules of CO

2

for each

pyruvate

.

Electron Transport Chain

The Krebs cycle generates high-energy compounds (10NADH and 2 FADH

2 )

that are passed to. The electrons are then passed from those carriers to the

Electron Transport Chain

.

The electron transport chain-

uses the high-energy electrons from the Krebs cycle to convert

ADP into ATP.In Eukaryotes, the electron transport chain is composed of a series of

carrier proteins

located in the

inner membrane

of the

Mitochondrion

.

In prokaryotes, the same chain are in

the Cell M

embrane.

On average the ETC produces 3 molecules of ATP from each molecule of NADH

(30 ATP) and 1 molecule of ATP from each FADH

(2 ATP) produced in the

Kreb’s Cycle.

Every time a pair of

high-energy electrons moves

down the electron transport chain, the energy is used to

move H

+

ions across the membrane

. These ions then rush back across the membrane,

producing enough force to spin the ATP

synthase

and generate enormous amounts of ATP

.

So lets count...

2 ATP

2 NADH

From

Glycolysis

+

2 NADH

From Oxidation of

Pyruvate

+

6 NADH

2 ATP

2 FADH

From Krebs

Electron Transport System (

Converts NADH and FADH to ATP)

10 NADH

x 3 =

30 ATPs

2 FADH

x 2 =

4 ATPs

4 ATP

________________________38 ATPs Total!!!