Lecture 6 Flashcards
Define Cellular respiration. What is the overall highly simplified reaction for cellular respiration?
What are the three primary sets of reactions involved?
Cellular respiration is the catabolic disassembly of organic molecules resulting in ATP production. The simplified reaction: glucose + 6 O2 —> 6CO2 + 6 H2O + ATP
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.
Aerobic and anaerobic cellular respiration. Aerobic cellular respiration is generally more efficient and produces more energy and can only be used in an oxygenated environment. Aerobic cellular respiration is definitely preferred under us conditions because of the high yield of ATP per glucose. Anaerobic cellular respiration is best used in an environment without oxygen or cellular organelles.
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?
Glycolysis. Cellular glucose cannot be released from a cell once it is taken up because it becomes “locked” by charged phosphate. This first step does occur regardless of the presence of oxygen.
From where is the phosphate needed for glucose activation derived?
The phosphate needed for glucose activation is derived from the two ATP input at the beginning of glycolysis that breaks down into ADP plus phosphate.
What does glycolysis literally mean? What are the products of this reaction?
Glycolysis literally means “sugar” “splitting”. The products are a 2 pyruvate, 2 NADH + H+, and 4 ATP.
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).
2 Pyruvic acids have 4 less hydrogens than the original glucose; where do these hydrogens end
up?
These hydrogens go to the coenzymes FAD and NAD.
Why must NADH be oxidized into NAD+? In this oxidation reaction, what molecule is reduced?
What is the reduced form of the molecule called?
NADH must be oxidized to NAD+ to donate the hydrogen to pyruvic acid and reduce pyruvic acid into lactic acid.
What are the two strategies for oxidizing NADH?
You can either oxidize an NADH aerobically or anaerobically depending on the amount of oxygen present in the system. Aerobically oxidation occurs within the mitochondria. Anaerobically oxidation occurs in the cytoplasm.
Why is Lactic Acid produced in the absence of oxygen? Why do cells prefer NOT to utilize
anaerobic respiration (Lactic Acid Fermentation)?
Lactic acid is a byproduct of pyruvate from glycolysis and allows for the cellular respiration process to continue with a small yield of ATP. Cells prefer not to utilize anaerobic respiration because of the low ATP yield. Aerobic respiration has a significantly higher yield per glucose.
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?
Lactic acid is removed from the muscle via the Cori cycle. In the cori cycle, blood carries lactic acid from the muscle to the liver, and then the liver converts, the lactic acid back into glucose-6-phosphate.
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?
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?
Some symptoms could be fatigue, lethargy, generalized weakness due to these coenzymes having a significant role in ATP (energy) production. It also could lead to digestive issues like diarrhea, skin lesions, and mouth sores.
Why is Lactic Acid NOT produced in the presence of oxygen? Where does the oxidation of the reduced
coenzymes occur?
Lactic acid does not produce in the presence of oxygen because when oxygen is available, cells primarily use aerobic respiration, which fully breaks down glucose through the electron transport chain, and instead of converting Peru in intergalactic acid, it enters the mitochondria to generate significantly more ATP. Lactic acid is only produced when the cell needs to regenerate NAD plus through a different pathway because oxygen levels are low.
What are the products of glycolysis? Which are shuttled (transported) into the mitochondria? Once in the mitochondria, how is pyruvate assisted into the Krebs Cycle? (hint: what organic “helper” can assist the enzymatic breakdown of the carbon skeleton? What are the products of this incorporation of pyruvate into the mitochondrion (what are the products of the translocation reactions?)
The products of glycolysis are 2 ATP, 2 NADH + H+, and 2 pyruvate. Two electrons are transported into the mitochondria. Peiro is assisted into the Krebs cycle by being converted down into acetyl CoA. The products of the translocation reactions are 2 CO2, 3 NADH + H+, 1 FADH2, and 1 ATP per Acetyl CoA.
What two sets of chemical reactions occur within the mitochondria in the process of ATP production? Which one uses substrate level phosphorylation and which one uses oxidative phosphorylation?
Krebs cycle and ETC/oxidative phosphorylation. Krebs cycle uses substrate level phosphorylation, and ETC uses oxidative phosphorylation.
