Biology 48 - Human Physiology Lecture 5 Cellular Respiration ...

Biology 48 - Human Physiology
Lecture 5
Cellular Respiration
Cellular Respiration
Catabolic disassembly of organic molecules resulting in;
•
•
•
Multiple step process:
1. Glycolysis
2. Krebs Cycle
3. Electron Transport Chain & Oxidative Phosphorylation
Phosphorylation
Simplified Reaction:
2 Strategies
Glucose = O2→
1. Aerobic Respiration:
ATP production utilizing :
2. Anaerobic Respiration:
ATP production in absence of :
GLYCOLYSIS:
Glyco: “sweet” (sugar) ; Lysis: Splitting
1 st step in BOTH
• Initiates :
Overall process:
C 6H 12O 6 → 2 (C 3H 4O 3)

Steps in Glycolysis:
1. Glucose “Activation”
Glucose → 2 (Pyruvate) or Pyruvic Acid
Activated Cellular Glucose: “Locked” within cell by :
Phosphate obtained from :
Result:Fructose1,6 Diphosphate
Glycolysis: Requires INITIAL energy investment of :
of :
2. Production of :
C6H12O6+ 2ATP→ 2 (C3H4O3) + 4ATP
For every glucose molecule:
3. Production of :
4 ATP produced
- 2 ATP invested
C 6H 12O 6 + 2ATP→ 2 (C 3H 4O 3) + 4ATP
C 6H 12O 6 → 2 ( C 3H 4O 3 )
4 missing hydrogen atoms ?
C = 6 C (3x2) =
H = 12 H (4x2) =
O = 6 O (3x2) =
Question: What happened to the electrons ? What molecules might be holding them ?

Answer:
• Glycolysis: Results in:
• NAD is
Loss of
Loss of
Each picks up :
or
2NAD + + 2H 2→ 2NADH+ H +
Products : 2 Pyruvic acid (Pyruvic Acid)
2 NADH + H +
4 ATP
Question: What molecules must be present in order for glycolysis to continue?
Answer:
1. Glucose: “Stored Energy”
Supplied from :
2. 2 ATP: “Activation”
Supplied from :
Use 2 ATPs for:
3. NAD + : “Electron carrier”
NAD + NOT a product of :
NADH + H + is :
Oxidized back into :
Ready to accept :
NADH+ H + : Oxidation : 2 Strategies
1. Aerobically: Cellular Oxygen Present
• Oxidation occurs w/in :
2. Anaerobically: Cellular Oxygen Limited
• Oxidization occurs w/in :
Anaerobic Respiration: “Fermentation”
“Fermentation”

• NADH + H + :
Donates Hydrogens to :
Reduces Pyruvic Acid into :
• Products: Anaerobic Respiration
2 ATP molecules (NET)
2 Lactic Acid (reduced)molecules
(reduced)molecules
2 NAD + (Oxidized)
NAD oxidized &
Substrate Level Phosphorylation
ATP production results from using bond energy in :
• Negative Effects of Anaerobic Respiration
1.
2.
Decreases intracellular:
Resting Skeletal Muscle pH = 7.0
Exercising Muscle pH = 6.4
• Interferes w/ Ca 2+ release & muscle contraction
• Inhibits muscle :
Muscle Weakness & Fatigue
Muscle pain
Lactic Acid Removal: Normal Daily occurrence
occurrence
• Lactic Acid inter-converted back into:
Occurs within :
Blood carries :
• Liver produces: “Reverse Glycolysis Enzymes”
Glycolysis Enzymes”
• Glucose 6-Phosphate fates:
Conversion into:
a. Liver Glycogen :

. “Free” :
Blood glucose: Available to :
Only the liver can de-phosphorylate & release :
• CORI CYCLE : 2-way traffic between :
Blood Glucose:
a. Utilized immediately:
b. Stored:
Study Questions :
1. Define Cellular respiration. What is the overall highly simplified reaction for cellular respiration?
What are the three primary sets of reactions involved?
2. What are the two main strategies for energy utilization (hint one converts energy more efficiently
than the other) Each strategy is advantageous under specific physiological circumstances; explain
when you think each might be an advantage? One of the two process is definitely preferred under
most conditions, explain why.
3. What is the first step involved in cellular respiration of glucose by cells? Can cellular glucose be
released from a cell once it is taken up? Why or why not? Does this initial step occur regardless of
the presence of oxygen?
4. From where is the phosphate needed for glucose activation derived?
5. What does glycolysis literally mean? What are the products of this reaction?
6. Diagram the overall reaction of Glycolysis (do not include all of the intermediate steps – just the
components going into the reactions and the products coming out).
7. 2 Pyruvic acids have 4 less hydrogens than the original glucose; where do these hydrogens end
up?
8. Why must NADH be oxidized into NAD+? In this oxidation reaction, what molecule is reduced?
What is the reduced form of the molecule called?
9. What are the two strategies for oxidizing NADH?
10. Why is Lactic Acid produced in the absence of oxygen? Why do cells prefer NOT to utilize
anaerobic respiration (Lactic Acid Fermentation)?
11. How is the lactic acid removed from the muscle cells? Why can’t the skeletal muscle cells simply
reconvert the lactic acid into glucose 6-phosphate themselves?
12. Why is it important for cells to : 1) immediately phosphorylate glucose as it enters the cells &2)
Why must glucose be stored as a macromolecule / polymer (glycogen)? What is the only organ
which synthesizes the enzymes capable of catalyzing reverse glycolysis? Why is this important?
13. Niacin (VitB3) and Riboflavin(vitB2) are essential vitamins partially because of their role as
coenzymes (NAD and FAD). With this in mind, what do you think are some of the symptoms related
to Vit. B2 & 3 deficiencies?