lecture 12

Question 1

What is cellular respiration and how does it provide energy for our cells?

Answer 1

Cellular respiration is the process by which our cells convert the food we eat into usable energy. It is like the cells’ way of breathing and extracting energy from food. During cellular respiration, oxygen is used to break down the food molecules we consume, releasing energy that is stored in a molecule called ATP. This energy-rich ATP is then utilized by our cells to carry out various functions and activities in our bodies.

Question 2

How do we obtain energy from the food we consume?

Answer 2

We obtain energy by performing the process of oxidation on food. During this process, the food molecules are broken down, releasing energy that our bodies can use for various functions and activities.

Question 3

Does every oxidation reaction result in the production of energy?

Answer 3

No, not all oxidation reactions lead to the generation of energy. Energy release can vary depending on the specific reaction and the substances involved.

Question 4

what does the following mean A:B oxidoreductase

Answer 4

remember, always the first one is DONOR, the second one is the acceptor

Question 5

what does the following mean A:B oxidoreductase

Answer 5

remember, always the first one is DONOR, the second one is the acceptor

Question 6

what is oxidizing agent?

Answer 6

gaining electrons

So when we say that a substance is an “oxidizing agent” it means that it has the ability to accept electrons and reduce, which can be seen as “gaining” electrons.

Question 7

what is reducing agent?

Answer 7

loses electrons

Question 8

usually oxidation is accompanied by hydrogen transfer, what does that mean?

Answer 8

During oxidation, hydrogen transfer refers to the movement of hydrogen atoms from one molecule to another. It often involves the loss of hydrogen atoms from a substance undergoing oxidation. This process is important for the transfer of energy and the formation of new molecules during chemical reactions.

Question 9

What are the most common hydrogen donors in electron transfer reactions?

Answer 9

The most common hydrogen donors are coenzymes like NAD (nicotinamide adenine dinucleotide) and FAD (flavin adenine dinucleotide), as well as SH (sulfhydryl) groups.

Question 10

Is electron transfer usually associated with hydrogen transfer?

Answer 10

Yes, electron transfer is commonly accompanied by hydrogen transfer.

Question 11

Are NAD and FAD considered coenzymes?

Answer 11

Yes, NAD (nicotinamide adenine dinucleotide) and FAD (flavin adenine dinucleotide) are classified as coenzymes.

Question 12

Is it correct to say that electron transfer reactions often involve SH or coenzymes NAD and FAD as hydrogen donors?

Answer 12

Yes, it is correct to say that SH (sulfhydryl) groups and coenzymes NAD and FAD commonly act as hydrogen donors in electron transfer reactions.

Question 13

Is electron transfer usually associated with hydrogen transfer?

Answer 13

Yes, electron transfer is commonly accompanied by hydrogen transfer.

Question 14

will all oxidation reactions produce energy

Answer 14

no

Question 15

oxidoreductases

Answer 15

is the enzyme class responsible for catalyzing oxidation reactions

Question 16

give me examples of enzymes in the enzyme class oxidoreductases

Answer 16

dehydrogenases, oxidases, oxygenases, peroxidases, all of them catalyze oxidation-reduction reactions and produce energy in the body.

Question 17

What are the cofactors commonly used by dehydrogenases?

Answer 17

Dehydrogenases commonly use NAD (nicotinamide adenine dinucleotide) and FAD (flavin adenine dinucleotide) as cofactors.

Question 18

What is the role of dehydrogenase in biochemical reactions?

Answer 18

Dehydrogenase enzymes are responsible for removing hydrogen atoms from molecules, leading to their oxidation.

Question 19

What happens when alcohol is oxidized by dehydrogenases?

Answer 19

When alcohol is oxidized, it is converted into an aldehyde.

Question 20

What is the end product when an aldehyde is further oxidized?

Answer 20

The aldehyde is converted into a carboxylic acid.

Question 21

How does NAD participate in these oxidation reactions?

Answer 21

NAD acts as a coenzyme and is converted to its reduced form, NADH, by accepting the hydrogen atoms released during oxidation.

Question 22

What is the difference between NAD and NADP?

Answer 22

NAD (nicotinamide adenine dinucleotide) is the oxidized form, while NADP (nicotinamide adenine dinucleotide phosphate) has a hydroxyl group esterified with phosphate.

Question 23

What is the role of FADH2 in cellular reactions?

Answer 23

FADH2 acts as an electron carrier and is a reduced form of FAD (flavin adenine dinucleotide).

Question 24

What is the difference between anabolism and catabolism?

Answer 24

Anabolism refers to the processes that require energy and build complex molecules, while catabolism involves the breakdown of molecules to release energy.

Question 25

What is the role of ATP in cellular metabolism?

Answer 25

ATP (adenosine triphosphate) functions as a source of energy in cells. It is often generated through the oxidation of food molecules, and its breakdown provides energy for various cellular processes.

Question 26

What are the two ways in which ATP can be generated?

Answer 26

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

Question 27

Where does substrate-level phosphorylation occur and what is its main energy source?

Answer 27

Substrate-level phosphorylation occurs in both the cytosol and mitochondria. It is the primary energy source in the cytosol and is important for red blood cells and oxygen-dependent muscles.

Question 28

Where is the primary site of ATP production in cells?

Answer 28

The mitochondria, often referred to as the powerhouse of the cell, is the primary site where most of the ATP is generated.

Question 29

What happens when ATP is hydrolyzed?

Answer 29

ATP is hydrolyzed into ADP (adenosine diphosphate) and inorganic phosphate (Pi), releasing energy in the process.

Question 30

What is the role of Creatine Kinase in ATP homeostasis in muscles?

Answer 30

Creatine Kinase has an important job in muscles to keep ATP levels balanced by helping convert creatine phosphate (phosphocreatine) to ADP (adenosine diphosphate) during both rest and exercise, and vice versa.

Creatine Kinase helps convert creatine phosphate (phosphocreatine) to ADP (adenosine diphosphate) and vice versa. Think of creatine phosphate as a molecule that stores energy, similar to a rechargeable battery. When our muscles are at rest or need a boost of energy during exercise, Creatine Kinase takes a creatine phosphate molecule and converts it into ADP, which is like using up some of the stored energy. This conversion releases the stored energy, which can be used to produce ATP (adenosine triphosphate), the primary source of energy for muscle function.

Now, during periods of rest or when our muscles need to replenish energy, Creatine Kinase performs the reverse process. It takes ADP and converts it back into creatine phosphate, effectively recharging the “battery” and storing energy for later use.

So, in summary, Creatine Kinase helps in the conversion between creatine phosphate and ADP, allowing our muscles to store and release energy as needed, Creatine Kinase makes sure that muscles always have the energy they need to work properly.

Question 31

Describe the equilibrium reaction catalyzed by Creatine Kinase during muscle activity.

Answer 31

During muscle activity, our muscles need energy to perform various tasks. Creatine kinase is an enzyme that plays an important role in the transfer of high-energy phosphate groups in our muscles.

Creatine kinase helps balance two reactions. In one reaction, creatine and ATP are formed from creatine phosphate and ADP. This stores energy in the form of ATP. In the second reaction, creatine and ATP are broken down to creatine phosphate and ADP, which releases the stored energy from ATP and replenishes the creatine phosphate.

Equilibrium in this context means that these two reactions are balanced so that there is a continuous transfer of high-energy phosphate groups in our muscles. This ensures that our muscles always have access to ATP, which acts as fuel for muscle contractions.

Creatine kinase acts as a “ferry” by transporting phosphate groups between different molecules in our muscles. It helps to maintain a stable energy supply in the muscles during physical activity.

So, creatine kinase is important to ensure that our muscles have enough energy to perform their functions during muscle activity.

Question 32

What is the difference between anaerobic and aerobic mechanisms in ATP production?

Answer 32

Anaerobic mechanisms are used for short, intense activities like weightlifting or jumping and do not need oxygen. Aerobic mechanisms, on the other hand, require oxygen and are used for activities like swimming or cycling that last for a longer time.

Question 33

How does the activation of Creatine Kinase impact energy metabolism?

Answer 33

Activation of Creatine Kinase leads to the conversion of creatine phosphate and ADP into creatine and ATP. This triggers the release of energy, supporting cellular functions and contributing to aerobic metabolism during activities that require ATP.

Question 34

What is the role of Adenylate Kinase in cellular energy metabolism?

Answer 34

Adenylate Kinase is a special molecule that helps keep a good balance of energy building blocks (nucleotides) called AMP, ADP, and ATP inside our cells. It helps these building blocks change into each other, which is important for transferring energy and controlling how our cells work.

Question 35

Explain the interchange facilitated by Adenylate Kinase among AMP, ADP, and ATP.

Answer 35

Adenylate Kinase is like a helper in our cells that can move a special part called a phosphate group between different energy molecules. It can take a phosphate from one molecule called ADP and give it to another molecule called ATP, making it more energetic. It can also do the same thing between two other molecules called AMP and ADP. This helps the cell recycle and share its energy, so it can be used in different parts of the cell where it’s needed.

Question 36

In which type of metabolism is ATP generated, and how is it subsequently used?

Answer 36

ATP is primarily generated during catabolism, the process of breaking down molecules to release energy. The energy stored in ATP is subsequently utilized for various cellular processes, including anabolism (building complex molecules), muscle contraction, and active transport, among others.

Question 37

What is the main process that occurs in oxidative phosphorylation?

Answer 37

Oxidative phosphorylation is the process that takes place in the inner membrane of the mitochondria and is responsible for the production of ATP.

Question 38

How is the mitochondrion structured?

Answer 38

The mitochondrion has multiple layers, including the outer membrane, inner membrane, and matrix. The inner membrane contains respiratory electron carriers, ATP synthase, and other transporters, while the matrix contains enzymes involved in various metabolic pathways.

Question 39

What is the difference between cristae and cristernae in the mitochondria?

Answer 39

The term “cristae” refers to the multiple folds found in the inner membrane of the mitochondria, whereas “cristernae” refers to a single fold or ridge. The cristae provide an increased surface area for chemical reactions within the mitochondria.

Question 40

What is the function of the mitochondrial matrix?

Answer 40

The mitochondrial matrix is similar to the cytosol of the cell and contains various enzymes involved in metabolic pathways such as the citric acid cycle, fatty acid beta oxidation, and amino acid oxidation. It also contains DNA, ribosomes, and essential molecules like ATP, ADP, Pi, and ions such as Mg2+, Ca2+, and K+.

Question 41

What takes place in the intracistral space of the mitochondria?

Answer 41

The intracistral space refers to the space between the inner boundary and the cistral membrane within the mitochondria. This space is involved in various processes related to oxidative phosphorylation, including the movement of protons (H+) and the generation of a proton gradient.

proton gradient = this means that there is a difference in the concentration of protons between the intracistral space and another part of the mitochondria.

Question 42

How does the permeability of the outer membrane differ from that of the inner membrane of the mitochondria?

Answer 42

The outer membrane of the mitochondria is more permeable to small molecules and ions, allowing them to freely pass through. In contrast, the inner membrane is impermeable to small molecules and ions, including H+, due to the presence of specific membrane transporters.

Question 43

What is the role of mitochondria in ATP production?

Answer 43

Mitochondria play an important role in ATP production through oxidative phosphorylation. The inner membrane of the mitochondria contains proteins involved in creating ATP, including respiratory electron carriers, ATP synthase, and other components of the electron transport chain.

Question 44

How do mitochondria adapt to the energy needs of the cell?

Answer 44

Mitochondria are highly dynamic organelles, and their amount, size, and location can change depending on the energy demands of the cell. This allows mitochondria to adjust their function and ATP production to meet the specific energy requirements of the cell.

Question 45

What is the chemiosmotic theory in mitochondria?

Answer 45

The chemiosmotic theory describes the process of ATP synthesis in mitochondria through the flow of electrons and the generation of an electrochemical potential.

Question 46

How do reduced substrates contribute to the chemiosmotic theory?

Answer 46

In the chemiosmotic theory, reduced substrates are substances that carry electrons. When these reduced substrates donate electrons, it starts a chain reaction called the electron transport chain. This chain reaction is a series of chemical reactions involving the transfer of electrons, which ultimately leads to the generation of ATP, the cell’s energy source.

Question 47

What is the role of electron carriers in the chemiosmotic theory?

Answer 47

In the chemiosmotic theory, when electrons flow through the electron transport chain, it creates a difference in electric charge and concentration of ions across the inner mitochondrial membrane. This difference, known as an electrochemical potential, acts like a stored energy source, which can be used to produce ATP through the process of ATP synthesis.

Question 48

How is the energy from electron flow stored in the chemiosmotic theory?

Answer 48

In the chemiosmotic theory, when electrons flow through the electron transport chain, it creates a difference in electric charge and concentration of ions across the inner mitochondrial membrane. This difference, known as an electrochemical potential, acts like a stored energy source, which can be used to produce ATP through the process of ATP synthesis.

Question 49

What is the function of ATP synthase in the chemiosmotic theory?

Answer 49

ATP synthase, located in the inner mitochondrial membrane, utilizes the electrochemical potential to catalyze the synthesis of ATP from ADP and inorganic phosphate (Pi).

Question 50

Why is the direct reaction between ADP and a high-energy phosphate carrier considered highly thermodynamically unfavorable?

Answer 50

The direct reaction between ADP and a high-energy phosphate carrier is thermodynamically unfavorable because it requires a significant input of energy to form ATP, but also because the deltaG value is positive.

Question 51

How is ADP phosphorylated in the chemiosmotic theory?

Answer 51

In simple terms, in the chemiosmotic theory, ADP is transformed into ATP by adding a phosphate group using the energy generated when protons move across a gradient. This process helps create energy-rich molecules for the cell to use.

Question 52

Is the phosphorylation of ADP a result of a direct reaction between ADP and a high-energy phosphate carrier?

Answer 52

No, the phosphorylation of ADP in the chemiosmotic theory does not occur through a direct reaction between ADP and a high-energy phosphate carrier. It relies on the energy derived from the flow of protons to drive ATP synthesis.

Question 53

How is the energy needed to phosphorylate ADP provided in the chemiosmotic theory?

Answer 53

the process of converting ADP to ATP requires energy that is obtained from the movement of protons (charged particles) along a special pathway. This movement of protons generates an electrical and chemical difference, known as the electrochemical gradient, which provides the necessary energy for the formation of ATP, a molecule that stores and supplies energy to our cells.

Question 54

What is the role of electron transport in the chemiosmotic theory?

Answer 54

the chemiosmotic theory states that during electron transport, energy is released and used to move protons against their natural flow, creating an imbalance of protons. This imbalance, known as a proton gradient, is like a stored energy source that is used to convert ADP into ATP, the molecule that carries energy for our cells to use.

Question 55

What is the function of a specific protein in the membrane?

Answer 55

A particular protein in the membrane couples the “downhill” flow of protons with the phosphorylation of ADP. In simpler terms, it uses the energy from the movement of protons to convert ADP into ATP, which is the energy currency of the cell.

Question 56

What role do proteins play in the inner membrane?

Answer 56

Proteins in the inner membrane are responsible for connecting the “downhill” flow of electrons in the electron transport chain (ETC) with the “uphill” flow of protons across the membrane. They act as bridges between these two processes.

Question 57

Why is a membrane required for chemiosmotic energy coupling?

Answer 57

A membrane is required because it helps create a difference in proton concentration - proton gradient, which is important for making ATP. This membrane acts as a barrier that controls the movement of particles.

Question 58

How do reducing cofactors contribute to proton gradient formation?

Answer 58

Reducing cofactors are molecules that can carry and transfer electrons during the cell’s energy production process. They help remove electrons from nutrients and transfer them to the electron transport chain. There, energy is released from these electrons and used to create a proton gradient across the mitochondrial membrane. This gradient is important for producing ATP, which is the body’s main source of energy. In other words, reducing cofactors contribute to generating the energy-rich environment needed to produce ATP.

Question 59

What does the electron transport chain (ETC) complexes consist of?

Answer 59

The ETC complexes are composed of a series of electron carriers. Each complex contains multiple redox centers, which include FMN, FAD, cytochromes a, b, c, and iron-sulfur clusters. These components play a role in transferring electrons during the chain.

Question 60

What are the functions of FMN and FAD?

Answer 60

FMN and FAD are oxidoreductases and dehydrogenases. They serve as cofactors and electron carriers. FMN has only one nucleotide, while FAD has two nucleotides. Both molecules act as electron funnels, accepting two electrons from unstable carriers with single electrons and donating one electron at a time, as they can only accept single electrons.

Question 61

What are cytochromes a, b, and c?

Answer 61

Cytochromes a, b, and c are redox multi-center components. They are one-electron carriers and contain iron-containing porphyrin ring derivatives. The main difference between them lies in the variations in ring additions. Examples of these components include heme A, heme B, and heme C.

Question 62

What is an iron-sulfur cluster?

Answer 62

An iron-sulfur cluster is a redox multi-center that contains both iron and sulfur atoms. It serves as a one-electron carrier. The cluster is formed by the aggregation or coming together of two things, specifically iron and sulfur atoms. These clusters play a role in the redox reactions within the electron transport chain.

Question 63

What is Coenzyme Q or Ubiquinone?

Answer 63

Coenzyme Q or Ubiquinone is a lipid-soluble compound with conjugated dicarbonyl groups that readily accepts electrons. When it accepts two electrons, it also picks up two protons, resulting in the formation of an alcohol called ubiquinol.

In this context, “conjugated dicarbonyl groups” refers to specific chemical structures within the Coenzyme Q or Ubiquinone molecule. These structures consist of two carbonyl (C=O) groups that are connected or conjugated to each other.

Question 64

How does ubiquinol participate in electron transfer?

Answer 64

Ubiquinol, the reduced form of ubiquinone, can freely move within the membrane and carry electrons with protons from one side of the membrane to the other. It acts as a carrier, transferring electrons and protons during the energy transfer process.

Question 65

What is the NADH: ubiquinone oxidoreductase complex (complex 1)?

Answer 65

Complex 1, also called the NADH: ubiquinone oxidoreductase complex, is a large structure made up of many smaller parts in our cells. It is one of the biggest assemblies found in our bodies, in mammalian cells. It is made up of more than 40 different building blocks called polypeptide chains. These chains are produced by genes found in both the nucleus and the mitochondria.

Question 66

How does complex 1 transfer electrons?

Answer 66

Within complex 1, NADH binds in the matrix and non-covalently bound flavin mononucleotide (FMN) accepts two electrons from NADH. Several iron-sulfur centers then pass on one electron at a time towards the ubiquinone binding site. This transfer results in the conversion of ubiquinone (Q) to ubiquinol (QH2), which represents a gain of electrons (reduction).

Question 67

What is the relationship between NADH and NAD+?

Answer 67

NADH is the reduced form of NAD+ (nicotinamide adenine dinucleotide). During the electron transfer process, NADH donates electrons to the electron transport chain, becoming oxidized to NAD+. So, NAD+ represents the oxidized form of NADH.

Question 68

What is the role of Complex 1 in the electron transport chain?

Answer 68

Complex 1, also known as the NADH:ubiquinone oxidoreductase complex, plays a crucial role in the electron transport chain. It transfers two electrons from NADH to ubiquinone and simultaneously pumps H+ ions (protons) from the mitochondrial matrix to the intermembrane space.

Question 69

How does Complex 2, or the succinate dehydrogenase complex, contribute to cellular processes?

Answer 69

Complex 2 has a dual role. Firstly, it participates in the citric acid cycle by converting succinate to fumarate. Secondly, it is involved in the electron transport chain by accepting two electrons from succinate and passing them on through iron-sulfur centers to ubiquinone, which becomes reduced (QH2). Unlike Complex 1, Complex 2 does not transport protons across the mitochondrial membrane.

Question 70

What is the function of Complex 3, or the ubiquinone cytochrome c oxidoreductase complex?

Answer 70

Complex 3 transfers electrons from QH2 (reduced form of ubiquinone) to reduce cytochrome c. It contains components such as iron-sulfur clusters, cytochrome b, and cytochrome c. The transfer of electrons from QH2 to cytochrome c is accompanied by the translocation of protons across the mitochondrial membrane. The exact number of translocated protons may vary depending on the specific conditions. The movement of electrons within the complex is facilitated by a process called the Q-cycle.

Question 71

How does Complex 1 act as a proton pump?

Answer 71

Complex 1 transfers electrons from NADH to ubiquinone while simultaneously moving H+ ions (protons) from the mitochondrial matrix to the intermembrane space. This proton movement contributes to the establishment of a proton gradient across the membrane, which is essential for ATP synthesis.

Question 72

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

Answer 72

Ubiquinone, also known as Coenzyme Q, serves as an electron carrier in the electron transport chain. It accepts electrons from Complexes 1 and 2 and transfers them to Complex 3. Ubiquinone undergoes reduction and oxidation reactions as it shuttles electrons, playing a crucial role in the overall energy transfer process.

Question 73

What is the Q-cycle and where does it occur in the electron transport chain?

Answer 73

The Q-cycle is a process that occurs in Complex 3 of the electron transport chain. It describes how four protons are translocated across the mitochondrial membrane for every two electrons that react with cytochrome c.

Question 74

Where do the additional protons in the Q-cycle come from?

Answer 74

Two of the additional protons in the Q-cycle come from the reduced form of ubiquinone (QH2), while the other two are obtained from the matrix.

Question 75

How does the Q-cycle contribute to ATP production?

Answer 75

The Q-cycle, by translocating protons across the mitochondrial membrane, helps establish a proton gradient. This gradient is essential for ATP synthesis, as the flow of protons through ATP synthase generates ATP.

Question 76

What is the significance of Complex 4 (cytochrome oxidase) in the electron transport chain?

Answer 76

Complex 4 is responsible for the final step of electron transfer to oxygen in the electron transport chain. It consists of multiple subunits, including heme groups (heme a and heme a3) and copper ions. It plays a vital role in efficient oxygen utilization and ATP production.

Question 77

How do Complex 2 and Complex 4 affect ATP production in the electron transport chain?

Answer 77

The transfer of electrons and protons from Complex 2 (succinate dehydrogenase) to Complex 4 (cytochrome c oxidase) contributes to ATP production. More protons transferred through the complexes result in the generation of more ATP, while fewer protons lead to a decrease in ATP production

Question 78

What are the components involved in Complex 4 (cytochrome oxidase)?

Answer 78

Complex 4, or cytochrome oxidase, consists of multiple subunits, typically 13 in mammalian cells. It includes heme groups (heme a and heme a3) responsible for electron transfer and copper ions (CuA and CuB) that facilitate electron transfer to oxygen.