6. Energy of life

Question 1

How is ATP used for coupled reactions?

Answer 1

Some of the free energy that is released by exergonic reactions is captured in the formation of ATP from adenosine diphosphate (ADP) and inorganic phosphate. The ATP can then be hydrolysed at other sites in the cell to release free energy too drive endergonic creations.

Question 2

What are some examples of activities in the cell that require energy from the hydrolysis of ATP?

Answer 2

• Active transport across a membrane
• Condensation reactions that use enzymes to form polymers
• Modifications of cell singling proteins by protein kinases
• Motor proteins that move vesicles along microtubules

Question 3

What are some differences between cellular respiration and fermentation?

Answer 3

• cellular respiration is complete oxidation
• Waste products water and carbon dioxide
• Net energy trapped 32ATP
• Fermentation is incomplete oxidation
• Waste products are organic compound and carbon dioxide
• Net energy trapped is 2 ATP

Question 4

How does the glucose catabolism pathway use atp?

Answer 4

It extras the energy stored int eh covalent bonds of glucose and stores it instead in ATP molecules via the phosphorylation reaction:

ADP + pi + free energy –> ATP

Question 5

What is glycolysis?

Answer 5

Glucose is converted to two molecules of the 3C product pyruvate through a series of chemical rearrangements and a small amount of energy is captured in usable forms.
-Anaerobic

Question 6

What does cellular respiration entail?

Answer 6

• Uses o2 from the environment.
• Each pyruvate molecule is complete converted into three molecules of CO2 via citric acid cycle and electron transport chain.

Question 7

How does redox apply to the metabolism of glucose?

Answer 7

Glucose is the reductant (electron donor) and O2 is the oxidant (electron acceptor)

Question 8

What two forms does NAD+ exist in?

Answer 8

NAD+ is the oxidised form and NADH is the reduced form

Question 9

Where does glycolysis take place?

Answer 9

Cytosol

Question 10

What are the parts of the mitochondria?

Answer 10

🔹 cristae, each mitochondria has highly folded inner membrane
🔹 matrix is the fluid filled material containing DNA and ribosome

Question 11

What is the process of glycolysis?

Answer 11

🔹 one molecule of glucose, a C6 molecule is broken down into two C3 compound, pyruvate
🔹 the electrons from hydrogen atoms in glucose are collected by acceptor molecules such as NAD+ and when acceptor molecules are carrying hydrogen they are loaded, NADH
🔹 produces two ATP molecules per glucose

Question 12

How does pyruvate oxidation link glycolysis and the citric acid cycle?

Answer 12

• Pyruvate transported into the mitochondrial matrix

- Pyruvate is oxidised into a 2C acetate molecule and CO2

Question 13

What are the inputs and outputs of the citric acid cycle?

Answer 13

-The inputs to the citric acid cycle are acetate (in the form of acetyl CoA), water, GDP, and the oxidized electron carriers NAD+ and FAD.
• The outputs are carbon dioxide, reduced electron carriers (NADH and FADH2), and a small amount of GTP

Question 14

Where does Krebs cycle occur?

Answer 14

Matrix of the mitochondria

Question 15

What’s the process of Krebs cycle?

Answer 15

🔹 pyruvate (3C) produced in glycolysis passes into mitochondrion where it’s broken down into two carbon fragments to form intermediate acetyl coenzyme A
🔹 co2 is released and H+ are gathered by acceptor molecule to produce NADH.
🔹 as the cycle proceeds acceptor molecules NAD+ and FAD become loaded with H+ and electrons to form NADH and FADH2.

Question 16

What is the yield of Krebs cycle?

Answer 16

🔹 each pyruvate molecule, 3 Co2 molecules are released and for 2 pyruvate molecule, 6 Co2 produced
🔹 2 ATP molecules are produced from two pyruvate molecules
🔹 for each glucose molecule 6 carbon dioxide molecules are produced and the Krebs cycle must complete 2 circuits to break down two pyruvate molecules

Question 17

What are the two processes of oxidative phosphorylation which form ATP?

Answer 17

1. Electron transport. The electrons from NADH and FADH2 pass through a series of electron carriers which results in the active transport of protons out of the mitochondrial matrix and across the inner mitochondrial membrane, creating a proton concentration gradient.
2. Chemiosmosis where the protons diffuse back into the mitochondrial matrix through ATP synthase (channel protein)

Question 18

Where does electron transport chain occur?

Answer 18

In the cristae of the mitochondria

Question 19

What happens in the electron transport chain?

Answer 19

🔹 loaded acceptor molecules (NADH and FADH2) produced during glycolysis and Krebs cycle transfer electrons from one cytochrome to another and then finally to oxygen, which combines with hydrogen to form water.
🔹 electron transport releases energy which drives production of32 ATP

Question 20

Inputs and output of aerobic respiration

Answer 20

🔹 glycolysis INPUT: glucose, 2 NAD+, ADP + Pi
OUTPUT: 2 pyruvate, 2 NADH, 2ATP
🔹 Krebs cycle INPUT: 2 pyruvate, 8 NAD, 2 FAD2-, ADP + Pi
OUTPUT: 6CO2, 8NADH, 2FADH2, 2ATP
🔹 Electron transport chain INPUTS: 6O2, 2FADH2, 10NADH, ADP + Pi
OUTPUT: 6H2O, 2FAD, 10NAD+, 32ATP

Question 21

What are the two roles of the protein complex ATP synthase?

Answer 21

• Acts as a channel allowing H+ to diffuse back into the matrix
• Uses energy of that diffusion to make ATP from ADP and Pi

Question 22

Where does fermentation occur?

Answer 22

In the cytosol

Question 23

What are some ways the metabolism of glucose pathway is regulated?

Answer 23

All 3 steps are subject to allosteric regulation of key enzymes involved.
-A high concentration of the final product can inhibit the action of an enzyme that catalyzes an earlier reaction, and an excess of the product of one pathway can activate an enzyme in another pathway, speeding up its reactions and diverting raw materials away from synthesis of the first product