Ch 3: Cellular Respiration

Question 1

Energy in a cell

Answer 1

ATP loses a phosphate and turns into ADP. This creates lots of energy.

Question 2

Metabolism (def)

Answer 2

All chemical reactions taking place in an organism.

Question 3

Metabolic Pathway (def)

Answer 3

Particular sequence of connected reactions

Question 4

Enzyme (def)

Answer 4

A protein that facilitates a specific chemical reaction

Question 5

ATP (def)

Answer 5

• Adenosine triphosphate
• High energy molecule used to provide energy in cells
• 3 phosphates

Question 6

ADP (def)

Answer 6

• Adenosine Diphosphate
• Lower energy form of ATP
• 2 phosphates

Question 7

High-Energy molecules

(carrying high-energy electrons)

Answer 7

• NADH
• FADH₂
• NADPH

Question 8

Lower-Energy forms of the previous molecules

(without high energy electrons)

Answer 8

• NAD⁺
• FAD⁺
• NADP⁺

^​​

Question 9

Cellular respiration (def)

Answer 9

Set of metabolic pathways

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP&heat)

The whole point of it is to generate ATP for the cells

Question 10

Cellular respiration in Prokaryotic Cells

Where does it happen?

Answer 10

1. Citric acid cycle and glycolysis happen in the cytosol
2. Oxydative phosphorylation occurs in the plasma membrane

Question 11

Cellular respiration in Eukaryotic Cells

Where does it happen?

Answer 11

1. Glycolysis happens in the cytosol
2. The rest of the processes happen in the mitochondria:

• Citric acid cycle happens in the matrix of the mitochondrion
• Oxydative phosphorylation occurs in the inner membrane of the mitochondrion

Question 12

Glycolysis

Answer 12

• A metabolic pathway that breaks down glucose into two molecules of pyruvate
• Energy released is used to change ADP to ATP and NAD ⁺ to NADH
• Probably one of the first energy-releasing metabolic pathways to evolve
• All cells conduct glycolysis in the cytosol
• Involves 10 steps (chemical reactions), each with its own enzyme

Question 13

Citric Acid Cycle

AKA Krebs Cycle or Tricarboxilic Acid Cycle

Answer 13

• A CYCLICAL metabolic pathway
• Breaks down pyruvate into 3 CO2
• Energy released is used to change ADP to ATP, NAD⁺ to NADH and FAD⁺ to FADH₂
• Pyruvate is changed through 3 reactions before entering this cycle, but for simplicity, we will include these 3 in the Citric Acid Cycle
• Involves 11 chemical reactions, each with its own enzyme

Question 14

Oxidative Phosphorylation

Answer 14

• AKA the electron transport chain - Chemiosmotic ATP Synthesis
• A chain of molecules uses energy from NADH and FADH to generate a H⁺ gradient (gradient in the concentration of H⁺ ions)
• The H⁺ gradient is used to change ADP to ATP
• High energy electrons from NADH enter the chain at the beginning. Those from FADH₂ have less energy and enter the chain farther along.
• Involves 10 electron carriers (9 of which are proteins), plus ATP synthase.

Question 15

How many phosphate molecules will be created by NADH and FADH₂?

Answer 15

1. Glycolysis

1 Glucose - 2ATP → 2NADH + 4ATP + 2 Pyruvate

Net profit: 2NADH and 2 ATP

1. Citric Acid Cycle

1 pyruvate → 4NADH + 1FADH + 1ATP

2 pyruvate → 8NADH + 2FADH + 2ATP

1. Oxydative Phosphorelation

Question 16

Fermentation

Answer 16

• A metabolic pathway that changes pyruvate
• Energy required is supplied by the conversion of NADH to NAD ⁺
• By generating NAD⁺ , it allows glycolysis to continue in the absence of oxygen.
• Much less efficient than cellular respiration, only used in the absence of oxygen