Reviewdefine the following terms in your notesheet

Autotroph Heterotroph ATP Biochemical Pathway Photosynthesis (w/ equation) Cellular Respiration Mitochondria & Cristae Oxidation Rxn Reduction Rxn Chemiosmosis

Ch.7 How Cells Harvest Energy

OCC BIO-161

Dave Werner

Can you write the chemical equations for Photosynthesis & Cellular Respiration

Can you describe their relationship?

Video Clip – Overview of Cellular Resp

Overview of Cellular Respiration

Remember: PHOTOSYNTHESIS EQUATION: 6CO2 +  6H2O + LIGHT ENERGY  =  C6H12O6  + 6O2

CELLULAR RESPIRATION EQUATION:         C6H12O6 + 6O2  =  6CO2   +   6H2O +  

ENERGY RELEASED (ATP)

Cellular Respiration takes place in TWO STAGES. STAGE 1 - Cellular Respiration BEGINS with a Biochemical

Pathway called GLYCOLYSIS, that takes place in the Cells Cytosol YIELDS a relatively Small amount of ATP and does not require

oxygen. STAGE 2 - OXIDATIVE RESPIRATION, follows Glycolysis. 

Oxidative Respiration takes place within the Mitochondria.  This is far more effective than Glycolysis at recovering energy from

food molecules. OXIDATIVE RESPIRATION IS THE METHOD BY WHICH PLANT

AND ANIMAL CELLS GET THE MAJORITY OF THEIR ENERGY.

TWO TYPES OF CELLULAR RESPIRATION B/C they operated in the Absence of Oxygen,

the FERMENTATION PATHWAYS are said to be ANAEROBIC PATHWAYS.

If OXYGEN is PRESENT, the products of Glycolysis ENTER the PATHWAYS of AEROBIC RESPIRATION.

Aerobic Respiration produces a much Larger Amount of ATP, UP TO 20 TIMES MORE ATP PRODUCED.

GLYCOLYSIS – Video Clip 1. Both types of PATHWAYS BEGIN with

Glycolysis. 2. Glycolysis is a pathway in which One Six-

Carbon Molecule of GLUCOSE is Oxidized to Produce 2 Three-Carbon Molecules of PYRUVIC ACID OR PYRUVATE.

3. The word "GLYCOLYSIS" means "The Splitting of Glucose". 

4. SOME OF ITS ENERGY IS RELEASED. 5. Occurs in CYTOSOL OF THE CELL.

GLYCOLYSIS 6. Whether or not O2 is present, Glycolysis SPLITS (BY

OXIDATION) GLUCOSE INTO 3-CARBON MOLECULES OF PGAL.  PGAL IS THEN CONVERTED TO 3-CARBON PYRUVIC ACID.

7. Glucose is a Stable molecule that DOES NOT Break down Easily.

8. For a Molecule of Glucose to undergo Glycolysis, a Cell must First "SPEND" ATP to energize the Glucose Molecule.  The ATP provides the Activation Energy needed to begin Glycolysis.

GLYCOLYSIS Cont’d 9. Although ATP (ENERGY) is used to begin

Glycolysis, the reactions that make up the process eventually produce A NET GAIN OF TWO ATP MOLECULES.

10. Glycolysis is followed BY THE BREAK DOWN OF PYRUVIC ACID.

Glycolysis: FOUR MAIN STEPS STEP 1 - TWO Phosphates are attached to Glucose, forming

a NEW Six-Carbon Compound.  The Phosphate Groups come From 2 ATP, which are Converted to ADP.

    STEP 2 - The Six-Carbon Compound formed in Step 1 is SPLIT into TWO Three-Carbon Molecules of PGAL.

    STEP 3 - The TWO PGAL Molecules are Oxidized, and each Receives a Phosphate Group Forming Two NEW Three-Carbon Compounds.  The Phosphate Groups are provided by Two molecules of NAD+ forming NADH.

Steps cont. STEP 4 - The Phosphate Groups added in Step 1 and Step 3

are Removed from the Three-Carbon Compounds.  This reaction produces Two molecules of Pyruvic Acid.  Each Phosphate Group is combines with a molecule of ADP to make a molecule of ATP.  Because a total of Four Phosphate Groups were Added, FOUR MOLECULES OF ATP ARE PRODUCED.

TWO ATP Molecules were used in Step 1, but FOUR are Produced in Step 4.  Therefore, Glycolysis has a NET YIELD of TWO ATP Molecules for every Molecule of Glucose that is converted into Pyruvic Acid.  What happens to the Pyruvic Acid depends on the Type of Cell and on whether Oxygen is present.

AEROBIC RESPIRATION In most cells, the Pyruvic Acid (P.A.) that is

produced in glycolysis does not undergo fermentation.  Instead, if O2 is available, P.A. enters the pathway of Aerobic Respiration, or Cellular Respiration that requires O2. 

Remember - Aerobic Resp. produces nearly 20 times as much ATP than glycolysis alone.

Aerobic Respiration has TWO Major STAGES

THE KREBS CYCLE – Video Clip ELECTRON TRANSPORT CHAIN (ETC)

OVERVIEW OF AEROBIC RESPIRATION BREAK DOWN OF P.A. IN PRESENCE OF O2 =

AEROBIC RESP. AEROBIC RESP. TAKES PLACE INSIDE CELL'S

MITOCHONDRIA ("POWER HOUSE"). DURING AEROBIC RESP., ATP IS PRODUCED IN TWO

PATHWAYS KNOWN AS THE KREBS CYCLE & ETC. THE SERIES OF OXIDATION Rxns THAT MAKE UP

THE 2nd PHASE OF AEROBIC RESP. = KREBS CYCLE.

THE KREBS CYCLE IS A BIOCHEMICAL PATHWAY THAT BREAKS DOWN acetyl CoA, producing  ATP, H, AND CO2

OVERVIEW OF AEROBIC RESPIRATION

In Prokaryotes the rxns of Krebs cycle take place in Cytosol of the Cell.

In EUKARYOTIC CELLS, these rxns take place in the MITOCHONDRIA

OVERVIEW OF AEROBIC RESPIRATION The P.A. that is produced in glycolysis Diffuses

across the Double Membrane of a Mitochondrion & enters the MITOCHONDRIAL MATRIX (Space Inside the Inner Membrane of a Mitochondrion).

When P.A. enters the Mitochondrial Matrix, it Reacts with a molecule called COENZYME A to form ACETYL COENZYME A, abbreviated acetyl CoA.

CO2, NADH, and H+ are produced in this rxn.

OVERVIEW OF AEROBIC RESPIRATION DURING PROCESS FROM GLYCOLYSIS

THROUGH KREBS CYCLE, 1 GLUCOSE MOLECULE YIELDS 4 ATP, 10 NADH AND 2 FADH2

THE ENERGETIC e- IN THE MOLECULES OF NADH & FADH2 THAT ARE FORMED DURING THE KREBS CYCLE ARE USED TO MAKE ATP IN A SERIES OF RXNS = ETC.

MOST of the ATP Produced during Aerobic Respiration is MADE BY the ETC

THE KREBS CYCLE The Krebs cycle is a biochemical pathway

that breaks down Acetyl CoA, producing CO2, H+, NADH, FADH2, and ATP.

The rxns that make up the cycle were identified by Hans Krebs (1900-1980), a German-British biochemist.

The Krebs cycle has 5 Main Steps (All occur in the mitochondria) STEP 1 - A 2-Carbon Molecule of Acetyl CoA

Combines with a 4-Carbon Compound, OXALOACETIC ACID (AHKS-uh-loh-SEET-ik), to Produce a 6-Carbon Compound CITRIC ACID.

STEP 2 -  Citric Acid Releases a CO2 Molecule and a H+ to Form a 5-Carbon Compound.  By LOSING a H+ with its Electron, Citric Acid is OXIDIZED.  The H+ is transferred to NAD+, REDUCING it to NADH.

Kreb Cycle cont. STEP 3 - The 5-Carbon Compound Releases a CO2

Molecule and a H+, forming a 4-Carbon Compound.  NAD+ is reduced to NADH.  A Molecule of ATP is also Synthesized from ADP.

STEP 4 -  The 4-Carbon Compound Releases a H+ to form another 4-Carbon Compound.  The H+ is used to Reduce FAD (Flavin Adenine Dinucleotide) to FADH2, a Molecule similar to NAD+ that Accepts Electron during Redox Reactions.

STEP 5 - The 4-Carbon Compound Releases a H+ to REGENERATE OXALOACETIC ACID, which keeps the Krebs cycle operating.  The H+ Reduces NAD+ to NADH.

More info In Glycolysis one Glucose Molecule produces 2 Pyruvic Acid

Molecules, which can then form 2 Molecules of Acetyl CoA. 1 Glucose Molecule causes 2 Turns of the Krebs cycle. The 2 Turns produce 6 NADH, 2 FADH2, 2 ATP, and 4 CO2

Molecules. The CO2 is a WASTE PRODUCT that Diffuses out of the

cells & is given off by the organism. The BULK of the Energy released by the Oxidation of

Glucose still has NOT been transferred to ATP.  Only 4 Molecules of ATP - 2 from Glycolysis and 2 From the Krebs cycle

ELECTRON TRANSPORT CHAIN

Video Clip NADH and the 2 FADH2 Molecules from the

Krebs cycle DRIVE the Next Stage of Aerobic Respiration - The ETC.

That is Where MOST of the Energy Transfer from Glucose to ATP Actually Occurs.

ELECTRON TRANSPORT CHAIN In EUKARYOTIC CELLS

the Electron Transport chain LINES the INNER MEMBRANE of the Mitochondrion, the inner membrane has many long  folds called CRISTAE.

In Prokaryotes, the Electron Transport Chain LINES the CELL MEMBRANE

ELECTRON TRANSPORT CHAINfig.7.13

ATP is produced by the ETC when NADH & FADH2 RELEASES H+, REGENERATING NAD+ and FAD, which return to the Krebs Cycle to be reused. 

The e- in the H+ from NADH and FADH2 are at a High Energy Level.

These High Energy e- are PASSED Along a Series of Molecules. As the move from Molecule to Molecule, the e- LOSE some of their Energy

ELECTRON TRANSPORT CHAIN The Energy they LOSE is used to PUMP Protons of the H+

from the Mitochondrial Matrix to the other side of the Inner Mitochondrial Membrane.

The Pumping builds up a High Concentration (A Concentration Gradient) of Protons in the space Between the INNER and OUTER Mitochondrial Membranes.

The Concentration Gradient of Protons Drives the Synthesis of ATP by Chemiosmosis.

ATP Synthase (enzyme) molecules are located in the Inner Mitochondrial Membrane.  The ATP Synthase MAKES ATP from ADP as Protons move down their Concentration Gradient into the Mitochondrial Matrix.

ENERGY YIELD Through Aerobic Respiration a Maximum Yield

of 38 ATP Molecules can be PRODUCED.  (Figure 7-9)

    A.  2 - Glycolysis     B.  2 - Krebs cycle     C.  34 - Electron Transport Chain

The actual number of ATP Molecules generated through Aerobic Respiration varies from Cell to Cell.

Most Eukaryotic Cells Produce only about 36 ATP Molecules per Glucose Molecule.

Anaerobic Pathways 1. In the Absence of Oxygen, Some Cells can

Convert Pyruvic Acid into other compounds through Additional Biochemical Pathways that also Occur in the Cytosol.

2. The Combination of Glycolysis PLUS these Additional Pathways are known as FERMENTATION.

3. THE CHEMICAL REACTIONS THAT RELEASE ENERGY FROM FOOD MOLECULES IN THE ABSENCE OF OXYGEN ARE ALSO CALLED ANAEROBIC RESPIRATION.

LACTIC ACID FERMENTATION AND ALCOHOLIC FERMENTATION During the processes of Fermentation NO ADDITIONAL

ATP IS SYNTHESIZED. LACTIC ACID FERMENTATION IS THE PROCESS THAT

PYRUVIC ACID IS CONVERTED TO LACTIC ACID. Lactic Acid involves the Transfer of TWO Hydrogen atoms

from NADH and H+ to Pyruvic Acid.  In the process, NADH is Oxidized to form NAD+ which is needed to Keep Glycolysis Operating.

Lactic Acid Fermentation by Microorganisms plays an Essential role in the manufacture of Food Products such as YOGURT and CHEESE.

LACTIC ACID FERMENTATION AND ALCOHOLIC FERMENTATION CERTAIN ANIMAL CELLS, INCLUDING OUR MUSCLE

CELLS CONVERT PYRUVIC ACID TO LACTIC ACID. DURING EXERCISE, BREATHING CANNOT PROVIDE

YOUR BODY WITH ALL THE OXYGEN IT NEEDS FOR AEROBIC RESPIRATION.  WHEN MUSCLES RUN OUT OF OXYGEN, THE CELLS SWITCH TO LACTIC ACID FERMENTATION.

This process provides your muscles with the energy then need during exercise.

The side effects of Lactic Acid Fermentation is Muscle Fatigue, Pain, Cramps, and you feel Soreness.

ALCOHOLIC FERMENTATION CONVERTS PYRUVIC ACID TO CARBON DIOXIDE AND ETHANOL (ETHYL ALCOHOL Bakers use Alcoholic Fermentation of YEAST to make Bread. As Yeast Ferments the Carbohydrates in dough, CO2 is produced and trapped in the dough, causing it to

rise. When the dough is baked the Yeast Cells Die, & the Alcohol Evaporates, You cannot get drunk from

eating bread! Alcoholic Fermentation is used to make wine, beer, and the ethanol added to gasoline to make gasohol. The fact that alcohol is used to power a car indicated the amount of Energy that remains in the Alcohol

Molecules.

Alternative Energy Sources in the Body In humans & other mammals, the entrance of

glucose/organic compounds into an energy-releasing pathway depends on the kinds & portions of carbs, fats, & proteins in the diet.

Ex: Glucose at mealtime is transported to the blood, which tells the pancreas to create insulin in order to help cells take up glucose faster. Less activity = Glycogen as storage Hormones control whether to use free glucose as energy

source or store it.

More Examples Energy from Fats

Body stores most fats as triglycerides, accumulate in fat cells of adipose tissue.

Used as alternate energy when blood glucose levels fall. Too much glucose ends up as fat.

Energy from Proteins Body splits proteins into amino acids, which are used by

cells to make more proteins or nitrogen-containing compounds.

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