8.2 Cell Respiration

Question 1

Link reaction: reaction

Answer 1

Pyruvate -> Acetyl CoA (+ NADH, CO₂)

Question 2

Give an example of a catabolic pathway.

Answer 2

Cellular respiration

Question 3

Functions of outer membrane (mitochondria)?

Answer 3

Separates the content of the mitochondrion from the rest of the cell; contains appropriate transport proteins for shuttling pyruvate into mitochondria

Question 4

Steps of glycolysis (simple).

Answer 4

• Phosphorylation - Lysis - Oxidation - ATP formation

Question 5

Functions of inner membrane (mitochondria)?

Answer 5

Contains the carriers for the electron transport chain and ATP synthase for chemiosmosis; folded into cristae to increase surface area for electron transport chain

Question 6

Give an example of an anabolic pathway.

Answer 6

Photosynthesis

Question 7

First step of glycolysis.

Answer 7

Phosphorylation: Two molecules of ATP are used to begin glycolysis. The phosphates from the ATPs are added to form fructose 1,6-bisphosphate.

Question 8

What is chemiosmosis?

Answer 8

* The hydrogen carriers donate electrons via oxidation to electron carriers on the inner membrane (cristae)

* The electrons lose energy as they are passed along an electron transport chain

* This energy is utilized to pump protons (H⁺ ions) into the intermembrane space

* The build-up of protons creates a proton motive force (electrochemical gradient)

* The protons return to the matrix via a transmembrane enzyme (ATP synthase)

Question 9

Krebs cycle: Reaction

Answer 9

Acetyl CoA -> CO₂ (x2), ATP, NADH (x3), FADH₂

Question 10

What is oxidative phosphorylation?

Answer 10

* In chemiosmosis, protons diffuse through ATP synthase to generate ATP

* In order to maintain the electrochemical gradient, de-energized electrons must be removed from the transport chain

* Oxygen is the final electron acceptor and binds with free protons in the matric to form water (this maintains the H⁺ gradient)

* As protons were produced by oxidative processes, this method of ATP synthesis is called oxidative phosphorylation.

Question 11

What is the link reaction?

Answer 11

The link reaction functions to connect the anaerobic process of glycolysis to the aerobic activities of the mitochondria.

* Pyruvate (from glycolysis) is transported from cytosol to mitochondrial matrix

* Pyruvate is decarboxylated (CO₂ is produced) to form an acetyl compound that is then attached to coenzyme A (form acetyl CoA)

* Pyruvate is also oxidized to produce on reduced hydrogen carrier (NADH + H⁺)

Question 12

End result of glycolysis.

Answer 12

Four ATPs, two NADPs, two pyruvates molecules (an ionized form of pyruvic acid)

Question 13

Oxidation vs. reduction

Answer 13

Oxidation: * Loss of electrons * Gain of oxygen * Loss of hydrogen * Results in many C-O bonds * Results in a compound with lower potential energy Reduction: * Gain of electrons * Loss of oxygen * Gain of hydrogen * Results in many C-H bonds * Results in a compound with higher potential energy

Question 14

What is the electron transport chain?

Answer 14

The electron transport chain utilizes chemiosmosis to synthesize ATP via oxidative phosphorylation.

Question 15

What is the Krebs cycle?

Answer 15

The Krebs cycle describes a series of oxidation reactions that occur within the mitochondrial matric. (6C -> 5C -> 4C -> 4C).

* Acetyl CoA (link reaction) combines with a 4C compound to form a 6C compound

* Via oxidation/decarboxylation reactions, the original 4C compound is reformed

* These reactions result in the formation of carbon dioxide (x2), ATP (x1) and multiple hydrogen carriers (x3 NADH and x1 FADH₂)

Question 16

Functions of intermembrane space (mitochondria)?

Answer 16

Proton accumulation (maximize gradient)

Question 17

Where does the Krebs cycle occur?

Answer 17

Mitochondrial matrix

Question 18

Oxidation and reduction =

Answer 18

Redox reactions

Question 19

What is phosphorylation and what does it do?

Answer 19

Phosphorylation is the chemical addition of a phosphoryl group to an organic molecule. It creates a less stable molecule.

Question 20

Third step of glycolysis.

Answer 20

Oxidation and ATP formation: When the two G3P molecules are formed, they enter an oxidation phase involving ATP formation and the production of the reduced coenzyme NAD. Each G3P undergoes oxidation to form a reduced molecule of NAD+, which is NADH. During the formation of NADH, released energy is used to add inorganic phosphate to the remaining 3-carbon compound which results in a compound with two phosphate groups. Enzymes then remove the phosphate groups so that they can be added to ADP to produce ATP.

Question 21

Functions of cristae (mitochondria)?

Answer 21

Increases the surface area for oxidative phosphorylation

Question 22

Where does the link reaction take place?

Answer 22

Mitochondrial matrix

Question 23

Cellular respiration equation

Answer 23

C6H12O6 + 6O2 -> 6CO2 + 6H2O + energy

Question 24

What do catabolic pathways result in?

Answer 24

The breakdown of complex molecules into smaller ones

Question 25

Summary of glycolysis

Answer 25

* Two ATPs are used to start the process * Four ATPs are produced; a net gain of two ATPs * Two molecules of NADH are produced. The pathway involves substrate-level phosphorylation, lysis, oxidation, and ATP formation * The pathway occurs in the cytoplasm

Question 26

How many ATPs are produced in cellular respiration?

Answer 26

36 ATP

Question 27

Second step of glycolysis.

Answer 27

Lysis: The less stable 6-carbon phosphorylated fructose is split into two 3-carbon sugars called glyceraldehyde-3-phosphate (G3P).

Question 28

Cellular respiration involves the…

Answer 28

oxidation and reduction of electron carriers. They occur together because one compound’s loss is another compound’s gain.

Question 29

Where does glycolysis occur?

Answer 29

Cytoplasm/cytosol

Question 30

Mitochondria diagram

Answer 30

Question 31

What do anabolic pathways result in?

Answer 31

The synthesis of complex molecules from smaller ones

Question 32

Where does the electron transport chain take place?

Answer 32

In the fold of the inner membrane of the mitochondria (the cristae)

Question 33

Functions of matrix (mitochondria)?

Answer 33

Contains the enzymes necessary for the link reaction and the Krebs cycle

Question 34

What is glycolysis?

Answer 34

= ‘sugar splitting’. It uses no oxygen and occurs in the cytosol and proceeds efficiently in both aerobic and anaerobic environments and occurs in both prokaryotic and eukaryotic cells.