Cellular Respiration And Fermentation

Question 1

Energy flows into an ecosystem as sunlight and leaves as heat

Explain the cycle of energy from photosynthesis to respiration

Answer 1

Light is absorbed by plants and used for photosynthesis to occur in chloroplasts.
==Organic molecules plus oxygen are produced through photosynthesis== used in cellular respiration in mitochondria. ATP is realesed as heat energy == carbon dioxide and water are produced== photosynthesis occurs again

Question 2

What is fermentation?

Answer 2

A partial degradation of sugars that occurs without oxygen.

Question 3

What is AEROBIC RESPIRATION and under what conditions does it occur?

How is anaerobic respiration different from aerobic respiration?

Answer 3

Aerobic respiration consumes organic molecules and Oxygen and yields ATP

Anaerobic respiration occurs in the absence of Oxygen

Question 4

The transfer of electrons during chemical reactions releases energy stored in organic reactions. This released energy is ultimately used to synthesize ATP.

What are REDOX reactions?

Answer 4

Reactions where electrons are transferred between reactants during a chemical reaction
Oxidation– loss of electrons( increase in oxidation number)
Reduction– gain of electrons( decrease in oxidation number)

Question 5

Terminology of REDOX reactions 🙂🙂🙂

Answer 5

Electron donor– reducting agent

Electron acceptor– oxidizing agent

Question 6

In cellular respiration, glucose and other organic molecules are broken down in a series of steps
Electrons from organic compounds are usually first transferred to NAD+, a coenzyme (a substance that enhances the action/function of an enzyme)

What is an NAD+ and how does it function?

Answer 6

NAD+( as an electron acceptor) functions as an oxidizing agent during cellular respiration
Each NADH( the reduced form if NAD+) represents stored energy that is tapped to synthesize ATP

Question 7

NADH passes the electrons to the electron transport protein.

In contrast to an uncontrolled reaction, how does the ELECTRON TRANSPORT CHAIN occur?

Answer 7

The electron transport chain passes electrons in a series of controlled steps instead of one explosive reaction.

The energy yielded is used to regenerate ATP

Question 8

What are the 3 stages of cellular respiration?🚨

Answer 8

1. Glycolysis
2. The citric acid cycle
3. Oxidative phosphorylation

Question 9

The 3 stages of cellular respiration

What is glycolysis?

Answer 9

The breakdown of glucose into two molecules of pyruvate(a salt or an Ester of pyruvic acid)

Question 10

What is the citric acid cycle?

Answer 10

Completes the breakdown of glucose

Question 11

The 3 cycles of cellular respiration

Describe Oxidative Phosphorylation

Answer 11

Accounts for most of the ATP synthesis

Question 12

Among the 3 stages of cellular respiration, which stage accounts to almost 90% of ATP generated by cellular respiration?

Answer 12

OXIDATIVE PHOSPHORYLATION.

Question 13

For each molecule of Glucose degraded to CO2 and water 💦 by respiration, how many molecules of ATP does the cell make?

Turn that into a statement after answering this question

Answer 13

32

BREAKING DOWN 1 GLUCOSE MOLECULE, THE CELL PRODUCES 32 ATP MOLECULES

Question 14

What is glocolysis?

Answer 14

Glycolysis (splitting of sugar) breaks down glucose into 2 molecules of pyruvate.

Question 15

Glycolysis occurs in the cytoplasm and has 2 major phases

What are these phases?

Answer 15

Energy investment phase

Energy payoff phase

Fun fact: glycolysis always occurs whether Oxygen is present or not.

Question 16

How does glycolysis occur?

Into detail

Answer 16

Glucose, a six-carbon sugar is split into 2 three-carbon sugars. These sugars are then oxidized and their remaining atoms rearranged to form two molecules of pyruvate. (Pyruvate is the ionized form of pyruvic acid)

Question 17

Define SUBSTRATE-LEVEL PHOSPHORYLATION

Answer 17

A metabolism reaction that results in the production of ATP by the transfer of a phosphate group from a substrate directly to ADP

Most important::: it results in the production of ATP

Phosphate group added to ADP to produce ATP

Question 18

What is the net energy yield from glocolyisis per glucose molecule?

Answer 18

( 2 ATP + 2 NADH ) molecules

Question 19

The steps of glycolysis

Explain all the steps in the energy investment phase

Answer 19

1. With the help of hexokinase, a phosphate group is transferred from ATP to the sugar making the sugar more reactive.
2. Glucose 6-phosphate is converted to frucose 6-phosphate
3. Phosphofructokinase transfers a phosphate group to the other end of the sugar molecules investing the 2nd ATP molecule.
4. Aldolase cleaves/separates the 6 carbon sugars into 2 3-carbon sugars. Dihydroxyacetone phosphate and glyceraldehyde 3-phosphate are formed.
5. A reaction that never reaches equilibrium occurs betweens these 2 3-carbon sugars. Glyceraldehyde 3-phosphate is used in the next step as fast as it forms

Question 20

The steps of glycolysis

Describe and explain the energy payoff phase

Answer 20

1. Triose phosphate dehydrogenase catalyses two reaction. (@) NADH is formed by the oxidation of Glyceraldehyde 3-phosphaye) hence NAD+ gains electrons forming the NADH. The electrons come with the hydrogen atom( this is not dative covalent bond).
   (2) a phosphate group is attached to the oxidized substrate( 1,3-bisphosphoglycerate) forming a high-energy product.
2. Phosphoglyrlcerokinase transfers the phosphate group to ADP in an exergonic reaction.
3. Phosphoglyromutase locates the phosphate group of 3-phosphoglycerate forming 2-phosphoglycerate.
4. Enolase forms a double bond in the substrate by extracting a water molecule, yielding a phosphoenolpyruvate (PEP) a compound with a very high potential energy.
5. Pyruvate kinase transfers the phosphate group from PEP to ADP forming pyruvate.

Question 21

Glycolysis occurs in the cytosol while citric acid cycle occurs inside the mitochondria.

Citric acid cycle has 8 steps. Explain each of the steps.

Answer 21

1. Acetyl CoA adds on to its carbon chain the oxaloacetate producing citrate.
2. Citrate is converted to its isomer ISOCITRATE by the removal and addition of a water molecule.
3. Isocitrate is oxidized, reducing NAD+ to NADH and releasing a Carbon dioxide molecule. The resulting molecule is Ketoglutarate.
4. Another CO2 molecule is lost and NAD+ is reduced. Same process as in no.3. the remaining molecule is then attached to CoA by an unstable bond. The resulting compound is Succinyl CoA
5. CoA is displaced by a phosphate group which is transferred to GDP forming GTP(a molecule with similar functions to ATP). GTP can be used to produce ATP.[ If you’ve forget how…refer.] the resulting compound is succinate.
6. To Hydrogens are transferred from succinate to FAD forming FADH2. This is done by the oxidation of Succinate. The resulting compound is Fumarate.
7. Water molecule is added to Fumarate, rearranging the bonds in the substrate (Fumarate). The resulting compound is malate.
8. Malate is oxidized reducing NAD+ to NADH and regenerating Oxaloacetate.
   The process repeates when another Acetyl CoA enters the mitochondria.

OXALOACETATE IS CONSERVED THROUGHOUT THE PROCESS.

Question 22

Define the electron transport chain?

Answer 22

A collection of molecules embedded in the inner membrane of the mitochondrion in eukaryotic cells.

Question 23

What is the overall function of the electron transport chain?

Answer 23

To receive electrons from NADH and FADH2 and and move them through a series of REDOX reactions.

Question 24

What is the only member of the electron transport chain that is not a protein?

Answer 24

UBIQUINONE ( coenzyme Q or CoA)— a small hydrophobic molecule. This molecule is mobile within the membrane.

Question 25

Definition of Cytochrome.

Answer 25

Cytochrome— an iron containing protein that is a component of the electron transport chain in the mitochondria and chlorosplasts

Question 26

What are the sources of electrons from the electron transport chain. ???

Answer 26

FADH2

NADH

Question 27

Explain how the electron transport chain function in little details.

Answer 27

The 2 electron sources for the chain give electrons to the chain. There are 4 complexes of the electron transport chain.

Electrons are transferred from NADH to the first molecule in the chain. This molecule is a Flavoprotein. The Flavoprotein is then oxidized and passes electrons to an iron-sulfur protein. The iron sulfur protein Passes the electrons to a compound called Obiquinone. Thereafter electrons are passed to and between Cytochromes. The last Cytochrome, (Cyt a3)of the chain passes it’s electrons to oxygen (in O2). Each O picks up a pair of hydrogen ions(protons) this forming water.

Question 28

Does the electron transport chain make ATP directly?

Answer 28

The electron transport chain makes no ATP directly, instead it eases the fall of electrons from food to Oxygen, breaking a large free-energy drop into a series of smaller steps that release energy in manageable amounts, step by step.

Question 29

Definition of ATP synthase

Answer 29

A complex of several membrane proteins that functions in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen ion(proton) concentration gradient to make ATP.

It is found in the inner membrane of mitochondria bof eukaryotic cells and in the plasma membranes of prokaryotes.

Question 30

Basis function of ATP synthase?

Answer 30

To make ATP from (ADP and inorganic phosphate) p

Question 31

What is the power source of the ATP synthase?

Answer 31

A difference In the concentration of H+ (a pH difference) on the opposite sides of the inner membrane of the mitochondrion.

Question 32

Definition of chemiosmosis?

Answer 32

Energy coupling– occurs when the energy produced by one reaction or system is used to drive another reaction or system.

Chemiosmosis—> an energy coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP.
Under aerobic conditions, most ATP synthesis in cells occurs by chemiosmosis.

Question 33

Explain how the ATP synthase works in 5 steps.

Answer 33

1. H+ ions diffuse down/against their concentration level through a channel called a stator, which is anchored in the membrane.
2. H+ ions enter the binding sites within a rotor, changing the shape of each subunit so that the rotor spins within the membrane.
3. Each H+ makes one complete turn before leaving the rotor and passing through a Second channel in the stator into the mitochondrial matrix.
4. Spinning of the rotor causes the internal rod to also spin. This rod extends to a stationary catalytic knob.
5. Turning of the rod activated catalytic sits in the knob that produce ATP form ADP and a Phosphate group.

Question 34

Definition of oxidative phosphorylation.

Answer 34

The production of ATP using energy derived from the REDOX reactions of electron transport chain, the third major stage of cellular respiration.

Question 35

As the H+ ions are accepted from the mitochondrial matrix and deposited in the intermembrane space, the H+ gradient that results is referred to as a Proton-Motive Force.

Define the Proton-Motive force.

Answer 35

This is the potential energy stored in the form of a proton electrochemical gradient, generated by the pumping of hydrogen ions(H+) across a biological membrane during chemiosmosis.

Question 36

What is the general meaning of chemiosmosis?

Answer 36

An energy coupling mechanism that uses energy in the form of an H+ gradient across a membrane to drive cellular work. Look

Question 37

State the reasons we cannot state the specific amount of ATP produced, instead we state inexact numbers.

Answer 37

1. Phosphorylation and the REDOX reactions are not directly coupled to each other, so the ratio of the number of NADH molecules to the number of ATP molecules is not a whole number.
2. The amount of ATP produced slightly varies due to the type of shuttle used to transport electrons from the cytosol( after glycolysis) into the mitochondria.
   NADH is not permeable to the mitochondrial membrane.
   The electrons from NADH are transported with either NAD+ or FAD
   FAD produces 1.5 ATP
   NAD+, produces 2.5 ATP
3. The use of Proton-Motive force generated by the REDOX reactions of respiration to drive other kinds of work. Not all the proton motive force is used to produce ATP. If all of it was used, then we would produce 28 molecule of ATP

Question 38

What are the 3 factors affecting ATP yield

Know and describe them.

Answer 38

1. Removal/ a sense of oxygen– this shuts the whole electron transport chain and makes it stay in it’s reduced state. It therefore cannot maintain the H+ gradient across the membrane, thus the ATP synthase will stop function( as no H+ ions will be passing through it) hence stoping the yield of ATP
2. Addition of cyanide– similar to removal of oxygen, this shuts down the electron transport chain…
3. Uncoupling protein( use the proton gradient for some other tasks other than producing ATP). They disconnect the the electron transport chain from ATP synthesis.

Question 39

How much of energy does the complete oxidation of 1 mole of glucose produce?

Answer 39

Under standard conditions, it produces/ releases 686 kcal of energy.

Question 40

What is the efficiency of respiration?

Answer 40

34%
34% of the chemical energy in glucose is transferred to ATP during respiration.

The rest of the energy stored in glucose is released as heat.

Question 41

What are other 2 ways in which ATP can be produced without the use of Oxygen?

What is the difference between the two

Answer 41

Anaerobic respiration

Fermentation

The only difference is that anaerobic respiration uses the electron transport chain while fermentation doesn’t.

Question 42

What is the oxidizing agent of glycolysis?

Answer 42

NAD+

Question 43

Under aerobic condition, NAD+ is recycled from NADH by the transfer of electrons to the electron transport chain.

How is NAD+ recycled under anaerobic conditions?

Answer 43

Electrons are transferred from NADH to pyruvate, at the end product of glycolysis.

Question 44

Why are the 2 types of fermentation?

Answer 44

Alcohol fermentation– Glycolysis followed by the reduction of pyruvate to ethyl alcohol, regenerating NAD+ and releasing carbon dioxide.

Lactic acid fermentation– glycolysis is followed by the reduction of pyruvate to lactate, regenerating NAD+ with no release of carbon dioxide gas

Question 45

What are the major differences in cellular respiration and fermentation?

Answer 45

I’m fermentation, the final electron acceptor is an Organic molecule such as pyruvate( for lactic acid fermentation) or acetaldehyde (for alcohol fermentation). In cellular respiration by contrast, electrons carried by NADH are transferred to an electron transport chain, which regenerates the NAD+ required for glycolysis.

Another major difference is the amount of ATP produced. Fermentation produce 2 ATP molecules by SUBSTRATE-LEVEL PHOSPHORYLATION while respiration yields up to 32 molecules of ATP.

🚨 The reason for this is that in fermentation, in the absence of an electron try chain, the energy stored in pyruvate is unavailable. However in cellular respiration, pyruvate is completely oxidized inside the mitochondrion. Stepwise electro transport chain drives Oxidative Phosphorylation, yielding more(at least-not sure- )28 ATP molecules.

Question 46

Definition of Obligate anaerobe.

Answer 46

An organism that carries out only fermentation or anaerobic respiration. Such organisms cannot use oxygen and in fact may be poisoned by it.

Question 47

Definition of facultative anaerobe.

Answer 47

An organism that makes ATP by aerobic respiration in the presence of oxygen but that switches to anaerobic respiration or fermentation in the absence of oxygen.

Example is an yeast and many other bacteria.

Question 48

Definition of the beta oxidation.

Answer 48

A metabolic sequence that breaks fatty acids down into 2-carboj fragments that enter the citric acid cycle as Acetyl CoA.

Question 49

What is phosphofructokinase and how does it work?

Answer 49

Types of candies is an allosteric enzyme with receptor sites for specific inhibitors and activators. Inhibited by ATP and stimulated by AMP( adenosine monophosphate) which derives from ADP.
As ATP accumulated, the mission of the enzyme is to slow down glycolysis therefore it becomes active again as cellular work converts ATP to ADP faster than ATP is being regenerated.

If citrate consumption increases, meaning that its amount in the cell would have decreased, glycolysis accelerates to meet that demand to produce ATP.