Cellular Respiration

Cauthers 2007

Energy

What are some types of energy we use everyday?

Living things require chemical energy stored within their food to function.

Cellular Respiration

Cells break down food into energy *some as heat *some as chemical energy

Occurs in multiple steps called a biochemical pathway

Each step is regulated by enzymes and involves the transfer of electrons

Energy

Energy derived from food is not given off in a great burst…how come?

Our cells would die!!!

Small packets of energy are stored in high energy bonds of ATP

Bond, Phosphate Bond

ATP = adenosine triphosphate -stores chemical energy

ATP is made of:

1) 1 Adenine2) 1 Ribose3) 3 Phosphates

Let’s look at ATP!!!

Phosphorylation: ATP transfers a phosphate group (releases energy) it becomes ADP (adenosine diphosphate)

ADP

Phosphorylation

ADP structure

ATP doesn’t grow on trees does it?

The main source of energy is GLUCOSE!!!

Energy transfer…

Electrons carry energyEnergy is transferred to carriers

If an atom is oxidized, it loses energy

If an atom is reduced, it gains energy

Electron Carriers…

Two types in cellular respiration:

NAD+ and FAD

Each of these can accept a pair of electrons and H atoms…

Respiration Types

Aerobic respiration requires O2

Anaerobic resp. does not require O2

Aerobic resp. produces much more energy

Who does what?

Only the unicellular organisms (bacteria mostly) rely solely on anaerobic resp.

Everything else can do both anaerobic and aerobic resp.

Glycolysis

*First step of all respiration*Takes place in the cytoplasm*Does not require oxygen

*Glycolysis= splitting of glucose Lysis - to split Glyco- refers to glucose

*Requires energy from ATP

Glycolysis

2 ATP molecules split glucose4 ATP molecules are created when pyruvic acid is formed.

How much net ATP is made through glycolysis?

2 NET ATP

Glycolysis Graphic

PGAL

Pyruvic Acid

Glucose2ATP 2ADP

PGAL

2ADP

2ATP

2ADP

2ATP

Anaerobic Respiration

ATP is only made during glycolysis.

Therefore how much ATP do anaerobic organisms make?

2ATP

Fermentation…

*2 types:

1) Lactic acid fermentation

2) Alcoholic fermentation

*Any reaction that occurs after glycolysis in an anaerobic organism

Lactic Acid Fermentation

Pyruvic acid is converted to lactic acid.

Any athletes who have felt muscle burn after a strenuous workout are feeling lactic acid buildup.

Alcoholic Fermentation

Some organisms (yeast) have enzymes that break pyruvic acid into ethyl alcohol and carbon dioxide.

Alcoholic fermentation is important in the process of… breadmaking!!!!

(CO2 makes bread rise)

Alcohol again…

Alcoholic fermentation also gives rise to alcohol…

Glucose Source Beverage

Barley Beer

Potato Vodka

Grapes Wine

Rice Sake

Aerobic Respiration

How much ATP was produced from glycolysis in anaerobic respiration?

2 ATP

Aerobic respiration continued…

In order for pyruvic acid to be broken down, yielding further energy, 2 things are required:

1) Oxygen (O2)

2) Mitochondria

Breaking pyruvic acid…*Pyruvic acid enters the mitochondrion*Broken into a 2 carbon molecule*Forms acetyl CoA*Enters the Krebs Cycle

Each molecule of pyruvic acid yields 1 CO2 and 1 NADH

Pyruvic Acid

NAD+

NADH CO2

CoA

Interesting tidbits…For every turn of the Kreb’s cycle, only 1 ATP is produced!!!CO2 is given off

Where does the rest of the ATP come from?

Electron Transport Chain

Energy stored in NADH and FADH2 is released in steps

Electrons passed from carrier to carrier, until O2 accepts the last 2 electrons.

Ahhh, big words…

As e- pass energy passes

Some of that energy is used to convert ADP to ATP (by means of a H+ pump)

The last step…

*O2 is the final electron acceptor*Combines with 4 H, to form…

WATER!!!

2 NET ATP from glycolysis2 ATP from the Kreb’s32 from the ETC 36 ATP gained!!!

Net Reactions of aerobic:

C6H12O6 + 6 H2O + 6 O2

6 CO2+ 12 H2O + 36 ATP

Aerobic Pathway

Aerobic Pathway

Recap:

Why aerobic respiration instead of anaerobic?

Aerobic respiration yields 18 times more energy!!! (36:2)

What if we don’t have oxygen?

Aerobic respiration can’t occur without it.

Without oxygen, the Kreb’s cycle will stop, leaving a buildup of pyruvic acid…

The fate of pyruvic acid.

Without oxygen, what are 2 things that could happen to pyruvic acid?

Alcoholic or lactic fermentation!

What happens to us?

Lactic acid fermentation!

Oxygen Debt

Anytime your muscles get starved for oxygen, and lactic acid fermentation begins, you experience oxygen debt.

Oxygen debt is the amount of oxygen your body requires to get rid of lactic acid.

Atkins Heaven

Glucose is the main source of energy for ATP, but proteins and fats may be used as well.

Fat produces twice as much energy as glucose does, but you must be twice as active to burn a gram of fat…

Proteins may be used as an energy source as well, though there is much controversy as to whether this is good for the body or not…and it is terribly inefficient.

Ramifications? Kidney problems

Man vs. Machine

Another interesting tidbit:

Roughly 45% of the available energy of a glucose molecule is stored as ATP following aerobic respiration.

In comparison only 20% of the energy of gasoline is used by cars.