popeye knew what he was doing! photosynthesis & cellular respiration today’s reference: sec...

Popeye knew what he was doing!

Photosynthesis & Cellular Respiration

Today’s reference:

Sec 5.3

Methane

What do these things have in common?All these products are the result of cellular respiration! There are actually 3 different types of respiration – let’s take a look!



Cellular Respiration – What we Know:

•Cells convert the energy stored in glucose to ATP.

•The process of cellular respiration oxidizes glucose to form CO2 and H2O, and the released energy is stored as ATP.

•ATP is then used as an energy source for most cell processes (muscle contraction, active transport, etc.).

C6H12O6(aq)+ 6O2(g) 6H2O(l) + 6CO2(g) + Energy



Cellular Respiration – What we don’t know:

• The three types of respiration are as follows:

1. Aerobic respiration

• Occurs in the presence of oxygen, and the most common form in plants and animals because it yields the most energy.

2. Anaerobic respiration

• Occurs without oxygen, and is seen in some types of bacteria.

3. Fermentation

• A much less efficient form of anaerobic respiration that occurs in fatigued muscle cells and yeast involved in bread and wine making.

Overview



The three types of respiration:

• The differences between the types of respiration are:

1. The final end product.

2. The amount of ATP produced.

• The similarity between the types of respiration is:

1. They all begin with the same process – glycolysis.

Let’s focus on the details of aerobic respiration, beginning with glycolysis.

Later, we will see how fermentation and anaerobic respiration differ.



Aerobic Respiration – Overview

• There are four main stages in aerobic cellular respiration:

1. Glycolysis – Oxidation of glucose into pyruvate that occurs in the cytoplasm of the cell.

2. Kreb’s cycle preparation – Pyruvate is used to form acetyl-CoA in the matrix of the mitochondria.

3. Kreb’s cycle – Energy is stored in reducing power of NADH and FADH2 within the matrix of the mitochondria.

4. Electron Transport Chain – Large amount of ATP is produced using the ETC embedded in the inner membrane of the mitochondria.



Backtrack: Structure of the Mitochondria

•Outer membrane surrounds mitochondria.

•Inner membrane is highly folded and is location of ETC.

•Cristae is the term used for the long tube-like folds of the inner membrane.

•Matrix is the gel-like interior surrounded by the inner membrane.



Stage One – Glycolysis (in CYTOPLASM):

• Glucose is broken down and eventually forms two molecules of pyruvate.

• During the steps it takes to do this, 2 ATP molecules and 2 NADH molecules are formed.

Glucose

IntermediatesIntermediates

Pyruvate Pyruvate2 ATP

2 ADP + 2P

2 NADH

2 NAD+

Glucose + 2ADP + 2P + 2NAD+



Stage Two – Preparing for Kreb’s Cycle:

• Pyruvate enters matrix of mitochondria.

• Pyruvate loses a carbon atom and binds with coenzyme A (CoA) to form acetyl CoA.

• Carbon dioxide is produced as a byproduct.

Pyruvate CoA CO2Acetyl CoA

NADHNAD+

2Pyruvate + 2CoA + 2NAD+

+ +



Stage Three – Kreb’s Cycle (In Matrix):

•Oxidation of carbon molecules forms ATP, NADH, and FADH. CO2 is a by-product.

•The net result using 2 acetyl-CoA molecules is as follows:

2 acetyl CoA 4 CO2

2 ATP6 NADH2 FADH2

Question: The cellular respiration equation says 6 carbon dioxide molecules are produced, but only four are shown from the Kreb’s cycle. Where do the other 2 come from?


Photosynthesis & Cellular RespirationStage Four – ETC (Inner Membrane):

•The NADH and FADH2 produced in steps 2 and 3 now enter the ETC found in the inner membrane.

•The 2 NADH produced in step 1 is also shuttled in, but at the cost of 2 ATP molecules.

•The NADH and FADH2 donate their electrons to the ETC to generate ATP in a process similar to the ETC in chloroplasts.(know how this works, but don’t worry about labeling cytochromes)

•For every NADH that enters the ETC, 3 ATP are formed.•For every FADH2 that enters the ETC, 2 ATP are formed.•Note that oxygen is the final electron acceptor, producing H20!

http://www.mcgrawhill.ca/school/applets/abbio/ch05/electrontrans_electron.swf



Cellular Respiration – Where did it all come from:

•Let’s take a look again at the four stages and where they occur.

•Let’s take a look at what stage of aerobic respiration these reactants and products are involved (use your notes!)C6H12O6(aq)+ 6O2(g) 6H2O(g) + 6CO2(g) + Energy

So what happens to all the oxygen we breathe in?



Can You Do the Math?:

•Remember that: 1 NADH = 3 ATP and 1 FADH2 = 2 ATP

How many ATP molecules do you think are formed in the four stages of aerobic respiration? Don’t forget 2 ATP molecules are used to shuttle NADH from the cytoplasm to the mitochondria!

Glycolysis 2 ATP

2 NADH 6 ATP

SHUTTLE -2 ATP

Pyruvate Acetyl CoA 2 NADH 6 ATP

Kreb’s Cycle 6 NADH 18 ATP

2 FADH2 4 ATP

36 ATPC6H12O6(aq)+ 6O2(g) 6H2O(g) + 6CO2(g) + 36 ATP



Anaerobic respiration

• Occurs without oxygen, and is seen in some types of prokaryotes (species in the Bacteria & Archea domains).

• These prokaryotes live in anoxic environments (marshy swaps, your colon).

• The main difference in anaerobic respiration is that oxygen is not the final electron acceptor at the end of the ETC. It is usually an inorganic chemical such sulfate or carbon dioxide.

• Common byproducts are methane, nitrogen, or sulfur.

• Take a look at the effects of anaerobic bacteria….

Blackened areas of the beached remains of a grey whale show hydrogen sulfide build up produced by anaerobic bacteria in the colon.



Fermentation

• Occurs without oxygen, and is seen in some types of bacteria, yeast, and fatigued muscle cells.

• Fermentation occurs only in the cytoplasm (no ETC involved). After glycolysis, 1 or 2 reactions occur to reduce pyruvate to another compound.

• Fermentation is less effective than other forms of respiration, because the only ATP generated comes from glycolysis.

• Two common byproducts are lactate (lactic acid), as is seen in our muscle cells, and ethanol, as is seen in brewer’s yeast. (Take a look at figures 5.21 and 5.22 on pages 190-191 in your textbook for pathways).

Lab Time!

Alcohol Fermentation

Lactic Acid Build up



Partner Project – Metabolic Toxins

•In the 1930’s, dinitrophenol (DNP) was used as a diet pill.

•DNP affects chemiosmosis by disrupting the hydrogen ion concentration gradient, thus interfering with ATP production.

•Since the mitochondria is not producing enough ATP, the body would rapidly oxidize (metabolize) carbohydrates and fats, leading to rapid weight loss.

• Low ATP production, however, also lead to very poor health and even death.

• DNP was pulled from the shelves as a diet pill.



Partner Project – Metabolic Toxins

•In the 1930’s, dinitrophenol (DNP) was used as a diet pill.

•DNP affects chemiosmosis by disrupting the hydrogen ion concentration gradient, thus interfering with ATP production.

•Since the mitochondria is not producing enough ATP, the body would rapidly oxidize (metabolize) carbohydrates and fats, leading to rapid weight loss.

• Low ATP production, however, also lead to very poor health and even death.

• DNP was pulled from the shelves as a diet pill.

HOWEVER

Some bodybuilders, at great risk to their health, will still use DNP prior to competitions.

Why is this unsafe? Are there other metabolic toxins, and do they do the same thing?



An uncoupler is a lipid-soluble weak acid that carries hydrogen ions across the inner membrane without use of ATP synthase. Thus, the movement of H ions is not generating the energy to create ATP.

popeye knew what he was doing! photosynthesis & cellular respiration today’s reference: sec...

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