BIO 183 Unit 3 Study Guide 1

What is the overall chemical equation for cellular respiration?

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ~36 ATP

Where in the cell does glycolysis occur? What is the starting molecule?

Glycolysis occurs in the cytoplasm and the starting molecule is glucose.

What are the three main components of cellular respiration?

Glycolysis, Citric Acid Cycle, and the Electron Transport Chain/oxidative phosphorylation.

What are the overall products of glycolysis?

• 2 pyruvate + H2O

• 2 NADH + 2H+

• 2 ATP

• Glycolysis begins with 1 molecule of glucose and ends with 2 molecules of pyruvate

 What are the net products of glycolysis from a single molecule of glucose?

2 ATP, 2 NADH, and 2 pyruvate per molecule of glucose

Explain the difference between oxidation and reduction in a redox reaction. You can use  the acronyms OIL and RIG to help you.

Oxidation: the loss of electrons from a substance (Mnemonic: OIL - Oxidation Is Loss).

Reduction: the gain of electrons by a substance (RIG - Reduction Is Gain).

What is NAD, NAD+, and NADH? How do molecules like NAD function as electron  carriers in cellular respiration?

NAD+= oxidized form (electron acceptor)

NADH = reduced form (has gained electrons)

Function:

NAD+ picks up high energy electrons during glycolysis and becomes NADH. NADH then carries those electrons to the electron transport chain, where they help produce ATP  

What is the energy investment required for the initial phase of glycolysis? What is the  payoff phase?

• Energy investment phase: uses 2 ATP to phosphorylate glucose (early steps)

• Payoff phase: produces 4 ATP and 2 NADH through the reduction of NAD+ to NADH

Net gain = 2 ATP

What is ATP? Know the molecular structure of ATP and what makes it a high energy  molecule (highly reactive)

ATP (adenosine triphosphate) = cell’s main energy molecule

Structure: adenine + ribose + 3 phosphate groups

Why high energy?

• The bonds between phosphate groups are unstable and repel each other 

• Breaking these bonds releases energy  

Know what ATP hydrolysis is (what is involved?)

• Breaking ATP → ADP + Pi (inorganic phosphate)

• Releases energy used for cellular work

What is energy coupling and how does ATP play a role? Be able to provide an example.

Energy coupling: using energy from one reaction to power another

• Role of ATP: ATP hydrolysis releases energy that drives endergonic reactions

• Example: ATP helps power active transport across membranes  

Be able to summarize the overall changes from a glucose molecule into two 3-carbon molecules  in Phase 1 of glycolysis (think about stability: glucose, to glucose-6-phosphate, to fructose-6- phosphate, to fructose-1,6-bisphosphate then to G3P). Why are molecules phosphorylated in  steps 1 and 3? Why rearrange glucose to a fructose ring?

• Two phosphorylation reactions occur, which require ATP

• Another enzyme splits fructose-1, 6-bisphosphate into two 3-carbon molecules, Glyceraldehyde 3 Phosphate, or G3P

• These two molecules of G3P are processed in tandem through phase 2 of glycolysis

Be able to summarize the changes to pyruvate in Phase 2 (payoff phase). For example, what is  the final product of glycolysis, and how many of these molecules are produced per glucose  molecule? What inputs and outputs are in phase 2 of glycolysis?

• Generates both ATP and NADH

• The two 3-carbon intermediates (3GP) are converted into two molecules of pyruvate

• The final net result is 2 ATP (4 produced, 2 used) and 2 NADH per molecule of glucose and 2 molecules of pyruvate

Know details about how glycolysis is regulated in the cell under different energy conditions.  How does an enzyme like PFK play a role? In the case of high ATP availability in the cell, how is  PFK regulated? Use the term that describes this type of enzyme regulation.  

• ATP demand and levels: high cellular ATP levels can inhibit enzymes like PFK (phosphofructokinase), decreasing the rate of glycolysis.

• Aerobic conditions: Pyruvate will be moved to mitochondria for the CAC, ETC + chemiosmosis, which  produces much more ATP than glycolysis. Glycolysis rate decrease

• Anaerobic conditions: Glycolysis is the only source of ATP for the cell, so the rate dramatically increases

Which cell types have especially high rates of glycolysis? Why do red blood cells have high rates  of glycolysis?

Active muscle cells perform glycolysis 100x faster than oxidative phosphorylation for energy needs, even in the presence of oxygen. Red blood cells don’t have mitochondria! Therefore they rely on only glycolysis for ATP.