Bio Exam Study Part Four

Front 1

ATP synthase:

Back 1

he protein complex in the presence of which chemiosmosis is accomplished

Front 2

charge differential (voltage):

Back 2

created by the movement of protons across the inner mitrochondrial membrane (by the electron transport chain), it is the difference in proton concentration (i.e. “charge”) across the membrane

Front 3

chemiosmosis:

Back 3

the process in which excess protons from the intermembrane space flow back into the mitochondrial matrix and ADP is phosphorylated to make ATP.

Front 4

electron transport chain:

Back 4

collectively refers to a set of membrane-bound enzymes which provide the energy to do work by moving positively charged hydrogen atoms

Front 5

FAD, FADH2

Back 5

like NAD+/NADH, these are electron carriers

Front 6

homeotherm:

Back 6

warm-blooded" animals which use the “waste” product of cellular respiration, heat, to maintain a constant body temperature.

Front 7

Krebs cycle:

Back 7

part of cellular respiration in which electrons are removed from acetyl CoA and reduce more NAD+ and FAD.

Front 8

mitochondrial matrix:

Back 8

the part of the mitochondrion enclosed within the inner membrane, which houses the enzymes and substrates for the Krebs cycle

Front 9

mitochondrion:

Back 9

contains the membrane-bound enzymes which comprise the electron transport chain.

Front 10

oxidative phosphorylation:

Back 10

the generation of ATP from chemiosmosis

Front 11

terminal electron acceptor:

Back 11

the last electron acceptor in the electron transport chain. This acceptor must be extremely electronegative; oxygen often is the terminal electron acceptor in the ETC.

Front 12

In a few words, describe what happens during glycolysis. How much energy in the form of ATP and NADH is produced and what product goes on to the final steps of cellular respiration?

Back 12

At the end of glycolysis, there is a net production of two molecules of ATP and two molecules of NADH. The ATP is produced via substrate-level phosphorylation; in this reaction, a phosphate group on an organic molecule is transferred directly (along with high-energy electrons) onto a molecule of ADP. Pyruvate is the end product which goes on to the final steps of cellular respiration.

Front 13

The processes discussed in this section all take place in the mitochondria of a cell. Draw this organelle and label the different areas. Where do all the different steps of cellular respiration occur in relation to this mitochondrion?

Back 13

The processes discussed in this section all take place in the mitochondria of a cell. Draw this organelle and label the different areas. Where do all the different steps of cellular respiration occur in relation to this mitochondrion?

Front 14

How much energy does each new molecule of ATP gain at the end of glycolysis? How much does NADH gain?

Back 14

At the end of glycolysis, there is an effective transfer of 20 kcals of energy to ATP (about 10 kcals each) and about 80 kcals of energy to NADH (about 40 kcal each).

Front 15

How much energy is gained by glycolysis alone? How much energy can be harvested from glucose? At the end of glycolysis, how much energy would then remain in each pyruvate molecule?

Back 15

At the end of glycolysis, 100 kcals of energy is gained. However, the complete oxidation of glucose results in the release of 686 kcals of energy; therefore, there is a good deal of energy still remaining in pyruvate (about 584 kcals!).

Front 16

Where is pyruvate transferred to? What is the final form that pyruvate is converted into? What is the name of the cycle to which this final product is subjected?

Back 16

In eukaryotes, pyruvate is transported across the mitochondrial membrane and then converted to acetyl CoA (with the production of NADH and carbon dioxide). The Krebs cycle uses acetyl CoA to couple more energy.

Front 17

What are the net energetic products and number of reduced electron carriers of one round of the Krebs cycle? For one molecule of glucose, how many rounds of the Krebs cycle will occur?

Back 17

1 ATP, 3 NADH, and 1 FADH2

Because each molecule of glucose produces two pyruvate molecules, the Krebs cycle occurs twice for each molecule of glucose.

Front 18

Acetyl CoA enters a series of enzymatic reactions during the Krebs cycle. Why do you think that this set of reactions is known as a cycle?

Back 18

This pathway is termed a "cycle" (and diagrammed as a circle) because the end product becomes the first product after reacting with acetyl CoA.

Front 19

What happens during the Krebs cycle to the acetyl CoA?

Back 19

During the Krebs cycle, there is complete oxidation of acetyl CoA. At the end of the cycle, CoA is converted into CoA—SH.

Front 20

What electron carriers are used during this cycle? What do they reduce to?

Back 20

NAD+ à NADH

FAD à FADH2

Front 21

What happens to the NADH and FADH2 molecules that are formed?

Back 21

The high energy electrons contained within these molecules will passed down to the electron transport chain, the final step of cellular respiration.

Front 22

What is the (not energetically useful) byproduct released during the Krebs cycle?

Back 22

Carbon dioxide.

Front 23

What are the main reactants of the Krebs cycle?

Back 23

Acetyl CoA, NAD+, FAD, ADP, and inorganic phosphate

Front 24

What are all of the main products?

Back 24

Carbon dioxide, NADH, FADH2, and ATP

Front 25

Aside from the ATP produced directly, where is a majority of the energy stored after the Krebs cycle?

Back 25

Because only one additional ATP molecule (per molecule of pyruvate) is produced by substrate-level phosphorylation in the Krebs cycle, the majority of the energy is tied up in NADH and FADH2.

Front 26

Where will these energetically useful products of the Krebs cycle be used? What will they be converted into?

Back 26

The high-energy electrons within NADH and FADH2 will be passed to a set of membrane-bound enzymes in the mitochondrion that are collectively referred to as the electron transport chain. They will be converted into useful energy.

Front 27

Briefly, how is ATP synthesized from the two electron transporters?

Back 27

The electron transporters will move electrons so that the electrons provide the energy to move positively charged hydrogen atoms (H+), also known as protons. The movement of protons across the inner mitrochondrial membrane (by the electron transport chain) creates a charge differential (i.e., voltage) that will be used to synthesize ATP.

Front 28

What type of molecules make up the electron transport chain? Why are the electronegativities of molecules within the electron transport chain important, and how do the electronegativities create a chain?

Back 28

The ETC is composed of a number of molecules (mostly proteins) that are located in the inner membrane of the mitochondrion. Each membrane protein has a particular electronegativity (affinity for electrons). The more electronegative the molecule, the more energy required to keep the electron away from it. In this way, a slightly electronegative membrane protein will pull electrons away from reduced electron carriers. In the presence of an even more electronegative molecule, these electrons will be oxidized from the first membrane protein, and so on, thus creating a chain.

Front 29

What is usually the final electron acceptor in the chain? What is special about this molecule? How does using this final electron acceptor create a maximal amount of free energy?

Back 29

Oxygen is usually the final electron acceptor in the ETC, due to its very high electronegativity. When oxygen acts as the terminal electron acceptor, there is a maximal amount of free energy released and hence, more protons can be transported (which means that a greater charge buildup occurs across the inner mitochondria membrane).

Front 30

What happens to this final acceptor? How is it disposed?

Back 30

Oxygen is reduced by electrons, then picks up hydrogen ions to form water. Water is disposed of as a waste product

Front 31

Specifically, how is energy made available in the ETC?

Back 31

An electron from one protein is transferred to another in the chain, so that each step has a negative ΔG. Therefore, with each oxidation/reduction reaction in every step of the ETC, energy is made available to do work. That work involves the movement of protons. This creates a charge differential (voltage) across the inner membrane; it is this stored energy that is actually used to synthesize ATP.

Front 32

What work is this energy used for? What does it set up?

Back 32

is energy is used for chemiosmosis of ATP. During the movement of electrons through the electron transport chain, protons accumulate on the inside of the inner mitochondrial membrane. As electrons move from one member of the electron transport chain to the next, protons are transported from one side of the membrane to the other, resulting in a buildup of protons in the intermembrane space. This sets up a voltage gradient which is later used for phosphorylation of ATP.

Front 33

What does the ETC create across the mitochondrial membrane? How does this synthesize ATP?

Back 33

The ETC creates a voltage gradient, i.e. a different concentration of protons, across the mitochondrial membrane. As these excess protons from the intermembrane space flow back into the mitochondrial matrix (the part of the mitochondrion enclosed within the inner membrane, which houses the enzymes and substrates for the Krebs cycle), ADP is phosphorylated to make ATP (chemiosmosis). Chemiosmosis is accomplished in the presence of the protein complex ATP synthase, which is also located in the inner mitochondrial membrane.

Front 34

How does the movement of protons fuel the phosphorylation of ADP? How is the energy converted? What enzyme is involved?

Back 34

Transfer of electrons provides the energy to move protons across the inner mitochondrial membrane. This buildup of protons creates a charge differential (voltage), and this stored energy is then used to provide energy to the ATP synthase (the important enzyme) complex to affect the production of ATP.

Front 35

25.) Review substrate level phosphorylation. How is it different then the way ATP is generated in the mitochondria by the ETC?

Back 35

In substrate level phosphorylation, a phosphorylated molecule transfers a phosphate group to ADP. This can only occur in the presence of a specific enzyme (which differs according to the particular substrate that is donating the phosphate). On the other hand, the generation of ATP from chemiosmosis is referred to as oxidative phosphorylation, because it is oxygen's oxidative property that allows a large amount of free energy to be made available for ATP synthesis. Much more energy can be generated using oxidative phosphorylation than in substrate level phosphorylation.

Front 36

What is an estimated yield of ATP per molecule glucose? How might energy be lost during cellular respiration?

Back 36

The estimated maximum net yield of one molecule of glucose is 38 ATP. Much of the energy bound in a molecule of glucose is actually lost as heat during metabolism.

Front 37

If an organism relied only on glycolysis and fermentation, what would be the net amount of ATP generated? Compare this to glycolysis with respiration. Can you think of some examples in which human bodies rely on glycolysis and fermentation instead of glycolysis and respiration?

Back 37

Fermentation and cellular respiration are anaerobic and aerobic alternatives, respectively, for producing ATP by harvesting the chemical energy from food. Both pathways use glycolysis, which produces a net 2 ATP by substrate phosphorylation. Without oxygen, the energy stored in pyruvate is unavailable to the cell, but with oxygen, pyruvate can be further broken down to yield many more ATP. Glycolysis + respiration yields about 38 ATP, whereas glycolysis + fermentation only yields about 2 ATP.

Human muscle cells can switch from glycolysis + respiration to glycloysis + fermentation, when we exercise and there’s not enough oxygen “to go around.” The lactate that is produced as a byproduct of the lactic acid fermentation in muscle cells can cause muscle fatigue and pain, but is eventually carried to the liver.

Front 38

alcohol fermentation:

Back 38

pyruvate gives off carbon dioxide and is converted to ethyl alcohol (ethanol) in a two-step process

Front 39

cellular respiration:

Back 39

a catabolic pathway comprised of a series of steps that convert the chemical energy in glucose into the energy contained in ATP

Front 40

electronegativity:

Back 40

the affinity for electrons

Front 41

fermentation:

Back 41

he process by which glucose is partially broken down and NAD+ is regenerated

Front 42

glycolysis

Back 42

a ten-step process which involves the initial breakdown of glucose to pyruvate (or pyruvic acid), water, and reduced electron carriers (in this case, NADH), and from which ATP is produced.

Front 43

lactic acid fermentation:

Back 43

process by which pyruvate is converted to lactate (lactic acid)

Front 44

NAD+:

Back 44

nicotinamide adenine dinucleotide in its oxidized form

Front 45

NADH:

Back 45

nicotinamide adenine dinucleotide in its reduced form

Front 46

oxidation:

Back 46

a loss of electrons

Front 47

oxidized:

Back 47

describes a molecule that loses an electron

Front 48

pyruvate:

Back 48

one of the products of the initial breakdown of glucose

Front 49

redox :

Back 49

short for the chemical process known as "reduction-oxidation,” and refers to the transfer of electrons that occurs during many chemical reactions.

Front 50

reduced:

Back 50

describes a molecule that gains an electron and thus has a "reduction" in its positive charge