week 12 - lecture 12

Question 1

How do human beings obtain energy?

Answer 1

Human beings obtain energy by performing the oxidation of food molecules.

Question 2

What is the role of oxidoreductases in biochemistry?

Answer 2

Oxidoreductases are enzymes responsible for catalyzing oxidation-reduction reactions and facilitating energy production in the body. Oxidoreductases are special enzymes that help with important reactions in our bodies. They make sure that certain substances get changed in a way that helps produce the energy our body needs to function properly. So, they play a vital role in making energy for our body.

Question 3

Can you provide examples of oxidoreductase enzymes?

Answer 3

Examples of oxidoreductase enzymes include dehydrogenases, oxidases, oxygenases, and peroxidases.

Question 4

How do dehydrogenases contribute to oxidation?

Answer 4

Dehydrogenases remove hydrogen atoms from molecules, leading to oxidation. For example, they convert alcohol to aldehyde and aldehyde to carboxylic acid.

Question 5

What is the function of NAD and FAD in biochemistry?

Answer 5

NAD (nicotinamide adenine dinucleotide) and FAD (flavin adenine dinucleotide) act as electron carriers, undergoing transformations between their oxidized and reduced forms to participate in redox reactions.

Question 6

What is the difference between anabolism and catabolism?

Answer 6

Anabolism refers to energy-requiring processes involved in building complex molecules, while catabolism involves the breakdown of complex molecules to release energy.

Question 7

What is the role of ATP in metabolism?

Answer 7

ATP (adenosine triphosphate) functions as an energy carrier in metabolism, providing the necessary energy for cellular activities.

Question 8

How is ATP generated in the body?

Answer 8

ATP can be generated through substrate-level phosphorylation and oxidative phosphorylation.

Question 9

What is the significance of substrate-level phosphorylation?

Answer 9

Substrate-level phosphorylation occurs in the cytosol and mitochondria and is a primary energy source for red blood cells and muscles with high oxygen demand.

Question 10

What is the function of creatine kinase in muscles?

Answer 10

Creatine kinase maintains ATP homeostasis in muscles by facilitating the interconversion of phosphocreatine and ATP based on energy demands.

Question 11

What is the difference between anaerobic and aerobic metabolism?

Answer 11

Anaerobic metabolism occurs without oxygen and is short-lasting, while aerobic metabolism relies on oxygen and occurs over a more extended period.

Question 12

What is the role of adenylate kinase?

Answer 12

Adenylate kinase facilitates the conversion between AMP, ADP, and ATP molecules.

Question 13

How does adenylate kinase function in catabolism?

Answer 13

Adenylate kinase allows two ADP molecules to be converted into ATP through catabolism.

Question 14

What happens to ATP during ATP consumption?

Answer 14

ATP is converted back into two ADP molecules through ATP consumption.

Question 15

What are the different parts of mitochondria?

Answer 15

Mitochondria consist of the outer membrane, inner membrane, cristae (folds), and matrix (fluid inside).

Question 16

How are the outer and inner membranes different?

Answer 16

The outer membrane is more permeable than the inner membrane.

Question 17

What are some components found in the inner membrane?

Answer 17

The inner membrane contains respiratory electron carriers, ADP-ATP translocase, ATP synthase, and other membrane transporters.

Question 18

What is present in the mitochondria matrix?

Answer 18

The matrix contains enzymes involved in metabolic pathways, such as pyruvate dehydrogenase complex, citric acid cycle enzymes, fatty acid beta-oxidation enzymes, and amino acid oxidation enzymes.

Question 19

Where does oxidative phosphorylation occur?

Answer 19

Oxidative phosphorylation takes place in the inner membrane of mitochondria.

Question 20

How is ATP synthesized in oxidative phosphorylation?

Answer 20

ATP synthase uses the energy stored in the electrochemical potential created by the transfer of electrons through the electron transport chain to synthesize ATP.

Question 21

What is the chemiosmotic theory?

Answer 21

The chemiosmotic theory explains how ATP synthesis occurs in mitochondria by utilizing the proton gradient generated during electron transport.

Question 22

How is the energy for ATP synthesis provided?

Answer 22

The energy needed for ATP synthesis is derived from the flow of protons down the electrochemical gradient.

Question 23

What is the electron transport chain?

Answer 23

The electron transport chain is a series of electron carrier complexes involved in the transfer of electrons during oxidative phosphorylation.

Question 24

What are some components of the electron transport chain?

Answer 24

The electron transport chain includes FMN, FAD, cytochromes (a, b, c), iron-sulfur clusters, and coenzyme Q (ubiquinone).

Question 25

What is the role of NADH in the electron transport chain?

Answer 25

NADH donates electrons to complex I, initiating the flow of electrons in the electron transport chain.

Question 26

What is complex I?

Answer 26

Complex I, also known as NADH-ubiquinone oxidoreductase, is a large assembly of polypeptide chains that accepts electrons from NADH.

Question 27

What happens to NADH during the process?

Answer 27

NADH is oxidized to NAD+ as it donates electrons to complex I.

Question 28

How does Complex I function as a proton pump?

Answer 28

Complex I transfers 2 electrons from NADH to ubiquinone while simultaneously moving H+ from the matrix to the intermembrane space.

Question 29

What is the role of the succinate dehydrogenase complex (Complex II) in the electron transport chain?

Answer 29

The succinate dehydrogenase complex accepts 2 electrons from succinate and passes them to ubiquinone, but it does not transport protons. It also has a dual role in the citric acid cycle, converting succinate to fumarate.

Question 30

What is the function of Complex III (Ubiquinone Cytochrome c Oxidoreductase Complex) in the electron transport chain?

Answer 30

Complex III utilizes 2 electrons from QH2 to reduce 2 molecules of cytochrome c. Additionally, it contains iron-sulfur clusters, cytochrome b, and cytochrome c. The translocation of 4 protons to the intermembrane space occurs through the clearance of electrons from reduced quinones via the Q-cycle.

Question 31

Describe the role of Complex IV (Cytochrome Oxidase) in the electron transport chain.

Answer 31

Complex IV transfers 4 electrons from cytochrome c to oxygen. It is a membrane protein with heme groups (a and a3) and copper ions.

Question 32

How does the electron transport chain contribute to ATP synthesis?

Answer 32

The electron transport chain, composed of Complexes I, II, III, and IV, transfers electrons and generates a proton motive force. This proton motive force is then utilized by the ATP synthase complex to produce ATP.

Question 33

What is the significance of the proton motive force in ATP synthesis?

Answer 33

The proton motive force, created by the electron transport chain, provides the energy required for ATP synthesis by the ATP synthase complex. It drives the conversion of ADP to ATP.

Question 34

What are the functional units of the mitochondrial ATP synthase complex?

Answer 34

The mitochondrial ATP synthase complex consists of two functional units: F1 and F0. F1 is a soluble complex in the matrix that catalyzes the hydrolysis of ATP, while F0 is an integral membrane complex that transports protons from the intermembrane space to the matrix.

Question 35

How is ATP synthesized by the mitochondrial ATP synthase complex?

Answer 35

The synthesis of ATP by the mitochondrial ATP synthase complex involves the rotation of the F0 subunit, caused by proton translocation. This rotation leads to conformational changes in the three αβ dimer units of F1, promoting the condensation of ADP and Pi into ATP.

Question 36

What factors regulate oxidative phosphorylation?

Answer 36

Substrate availability, specifically NADH and ADP/Pi levels, primarily regulate oxidative phosphorylation. Additionally, the inhibitor of F1 (IF1) prevents ATP hydrolysis during low oxygen conditions and acts only at low pH.

Question 37

How are electrons from NADH in the cytosol fed into the mitochondria?

Answer 37

Electrons from NADH in the cytosol enter the mitochondria through two methods: the malate-aspartate shuffle and the glycerol-3-phosphate shuffle.

Question 38

How can oxidative phosphorylation and electron transport be uncoupled?

Answer 38

Oxidative phosphorylation and electron transport can be uncoupled if the proton gradient across the membrane is disturbed. This uncoupling can occur through the use of chemical substances or proteins called uncouplers. Uncouplers disrupt the coupling between electron transport and ATP synthesis, allowing ATP synthesis to be uncoupled from electron transport. This can result in the generation of heat instead of the production of ATP. An example of an uncoupling protein is UCP1, which is present in the intermembrane space and generates heat in brown adipose tissue.

Question 39

Where is the process of uncoupling observed?

Answer 39

Uncoupling is observed in brown adipose tissue, which is a type of fat tissue. Within this tissue, uncoupling occurs through the action of uncoupling protein 1 (UCP1), which is located in the intermembrane space. The uncoupling process leads to the generation of heat in the mitochondrial matrix.

Question 40

What is the relationship between electron transport and ATP synthesis?

Answer 40

ATP synthesis requires electron transport to generate the necessary proton motive force. However, electron transport itself does not require ATP synthesis. The two processes can be coupled, with electron transport generating the proton motive force, which is then utilized by ATP synthase to synthesize ATP.

Question 41

How does the oxidation of glucose (or other fuels) affect ATP production?

Answer 41

The net production of ATP from the oxidation of glucose (or other fuels) can vary. In eukaryotic systems, NADH generated in the cytosol cannot directly enter the electron transport chain at Complex I due to organellar segregation. Instead, two methods, namely the malate-aspartate shuffle and the glycerol-3-phosphate shuffle, are used to transport electrons from NADH in the cytosol into the mitochondria for further oxidation and ATP production.

Question 42

What is the role of substrate availability in the regulation of oxidative phosphorylation?

Answer 42

Substrate availability, specifically the levels of NADH and ADP/Pi, plays a crucial role in the regulation of oxidative phosphorylation. NADH and ADP/Pi levels impact the rate of electron transport and ATP synthesis, ensuring that ATP production matches the energy demands of the cell. Additionally, the inhibitor of F1 (IF1) prevents ATP hydrolysis during low oxygen conditions, contributing to the regulation of oxidative phosphorylation.

Question 43

What is oxidative stress?

Answer 43

Oxidative stress refers to an imbalance between the production of reactive oxygen species (ROS) and the body’s ability to detoxify them, resulting in potential damage to cells and tissues.

Question 44

What lifestyle factors can contribute to oxidative stress?

Answer 44

Lifestyle factors such as smoking, alcohol consumption, and an inappropriate diet can contribute to oxidative stress.

Question 45

What are free radicals and how are they related to oxidative stress?

Answer 45

Free radicals are molecules or parts of molecules that have unpaired electrons. They are considered one category of reactive oxygen species (ROS). An excess of free radicals in the body’s cells can lead to oxidative stress.

Question 46

How does the electron transport chain (ETC) contribute to the generation of superoxide?

Answer 46

Approximately 1-3% of electrons leak out of the electron transport chain (ETC), leading to the release of superoxide, which is a primary reactive oxygen species (ROS). Complex I and Complex III within the ETC are responsible for the production of ROS in the mitochondrial matrix and intermembrane space.

Question 47

What are the other sources of superoxide apart from the electron transport chain?

Answer 47

Other sources of superoxide include NADPH oxidases (membrane-bound enzymes), the endoplasmic reticulum (during protein folding), xanthine oxidase (involved in purine metabolism), and cytochrome P450 enzymes.

Question 48

What are cytochrome oxidases and what role do they play in the electron transport chain?

Answer 48

Cytochrome oxidases are metalloproteins (containing elements such as Fe, Co, Mo) and are the main enzymes involved in the electron transport chain (ETC). They facilitate electron transfer and are represented by examples such as Heme C and Heme A.

Question 49

What is the difference between oxidases and oxygenases?

Answer 49

Oxidases transfer electrons to molecular oxygen, while oxygenases transfer atomic oxygen to substrates for their oxidation. Oxygenases are involved in the oxidation of substrates by transferring oxygen atoms from molecular oxygen, often seen in cytochrome P450 systems.