Download Bio 112 Chap 7 How Cells Harvest Energy

Chapter 7: Respiration
I.
II.
III.
IV.
I.
Summary of how organic molecules are used for energy
a. Anaerobic
b. Aerobic
Aerobic respiration
a. Glycolysis
b. Oxidation of pyruvate
c. Kreb’s Cycle
d. Electron Transport Chain
Anerobic fermentation
a. Alcohol
b. Lactic acid
Alternative sources of energy (other than carbohydrates)
Summary of Energy Pathways
Organisms get energy from the sun
1) photoautotrophs (directly)
2) heterotrophs (indirectly)
All types of organisms breakdown nutrients to make ATP
If aerobic (using oxygen), then called aerobic respiration (needs oxygen and makes carbon dioxide)
If anaerobic (no oxygen for life), then called fermentation. Some bacteria can do this. Also eukaryotes, like
your muscles when they run out of oxygen.
Similarities between aerobic and anaerobic:
Can begin with glucose
Both use glycolysis: Breakdown of 6-carbon glucose to make two 3-carbon pyruvate
Glycolysis occurs in the cytoplasm
Differences between aerobic and anaerobic:
Aerobic needs oxygen
Aerobic makes many more ATPs (very efficient)
Aerobic requires mitochondria
II.
Aerobic respiration
Over-all reaction: Glucose + 6O2  6CO2 + 6H2O + Energy
Aerobic respiration: overall is just breaking down the glucose molecules and harvesting electrons along the
way that are used to make ATP
FIRST REMEMBER! REDOX reactions (paired reactions where electron(s) are transferred between reactants)
Adding electrons: reduction
Removing electrons: oxidation
Must use electron carriers: NAD+ and FAD+ (These are both coenzymes needed by the enzymes of aerobic
respiration)
1) Each binds to 2 electrons
2) Become (NADH + H +) and FADH2
4 Steps of Aerobic respiration
1)
2)
3)
4)
glycolysis
oxidation of pyruvate
Kreb’s cycle
Electron transport chain
Glycolysis
1) In cytoplasm
2) Glucose + 2 ATP + 2NAD+  2 pyruvates + 4ATP + 2NADH + 2H+
3) Over-all: makes 2 ATPs via substrate phosphorylation and stores 4 electrons for energy
Oxidation of pyruvate
1) In mitochondria matrix
2) 2 pyruvates + 2CoA + 2NAD+  2AcetylCoA + 2CO2 + 2NADH + 2H+
3) Over-all: store energy in 4 electrons. NO ATP! The CO2 diffuses out of the cell.
Kreb’s Cycle
1) In mitochondrial matrix
2) 2 AcetylCoa  6NADH + 2FADH2 + 4CO2 + 2ATP
3) Over-all: store energy in 10 electrons and 2ATPs. The CO2 diffuses out of the cell.
Electron transport chain
1) On inner mitochondrial membrane
2) NADH + FADH2 + O2  H2O + 32ATP
3) Passing of electrons works the H+ pump that makes concentration gradient (proton motive force)
4) H+ pushes through an ATP synthase down it’s gradient
5) Energy to build ATP comes from moving H+
III.
Anaerobic fermentation
Glycolysis occurs in the cytoplasm and makes 2 ATPS and pyruvate
1) Alcohol fermentation: In anaerobic organisms, pyruvate is broken down to alcohol and CO2
We use yeast to do this in making wine and bread
2) Lactate fermentation: In other organisms, pyruvate is broken down to lactic acid (lactate) instead.
This happens in your muscles. Other organisms are used purposefully to make yogurt and pickles.
IV.
How your body responds to nutrient intake
What happens to carbohydrates:
• Glucose is ingested
• It passes across the stomach lining into the blood
• Insulin is released from the pancreas and cells take in glucose
• Aerobic respiration creates lots of ATP
• When enough ATP, glucose is made into glycogen for storage
• If too much glucose overwhelms these pathways, acetyl CoA is made into fats instead
• If not enough glucose (times between meals), pancreas release glucagon that tells glycogen to
release glucose into the blood.
What happens to fats:
• Fats can be used when low blood glucose and no glycogen available
• Triacylglycerides release fatty acids from fat cells (adipose cells) into blood stream
• Fatty acids are broken down into Acetyl CoA and move through Kreb’s Cycle
• (You get more ATP per fatty acid than you do from each glucose molecule)
What happens to proteins:
• When you eat proteins, they are broken down into amino acids.
• Amino acids are absorbed into cells and used to make new proteins.
• If you eat too much protein, the amino acids are further broken down and put into the Kreb’s
cycle.
• This creates a lot of ammonia (NH3)