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(Biology 211) Cellular Biology > Chapter 7 - Cellular Respiratjon > Flashcards

Chapter 7 - Cellular Respiratjon Flashcards

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1
Q

Difference between oxidation and reduction reactions?

A

Oxidation reactions lose electrons and reduction reactions gain electrons

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2
Q

Oxidation reactions decrease what type of energy from molecules?

A

Potential energy

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3
Q

Electrons being shifted between molecules in the cytoplasm are usually a part of what type of atom?

A

Hydrogen atom

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4
Q

What is the principle electron carrier molecule? What is it derived from and what forms does it take?

A

It is derived from vitamin B3, and Niacin, it’s called nicotinamide adenosine dinucleotide (NAD+), its reduced form is NADH after accepting 2 electrons, and a proton (H atom) and NAD+ being the oxidized form

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5
Q

NAD+ acts as what type of agent in REDOX reactions? How does it do it?

A

An oxidizing agent, it takes the electron and gets reduced to NADH

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6
Q

What is NADPH, and FAD+. How are they related to NADH?

A

They both act in similar ways but FAD+ is in the citric acid cycle, while NADPH plays a role in plants

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7
Q

What happens when ATP is broken down?

A

It becomes ADP and the terminal phosphate group (gamma) is removed and energy is released

-released energy is in form of a phosphate that binds to another molecule activating it (coupling)

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8
Q

What is the addition of a phosphate group and release of one called?

A

Phosphorylation (required input of energy) is addition of a phosphate group while if it gets released it’s called dephosphorylation (released energy)

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9
Q

Why are phosphate bonds unstable? For example in ATP?

A

Because phosphate groups are negatively charged and repel one another

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10
Q

When ATP is hydrolyzed what are the products?

A

ADP + inorganic phosphate (Pi) + free energy

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11
Q

In substrate phosphorylation when a Phosphate is removed from a reactant what happens?

A

The free energy of the reaction is used to add the third phosphate to an ADP making ATP

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12
Q

Most of generated ATP through glucose catabolism is from what?

A

Chemiosmosis

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13
Q

Where does chemiosmosis take place in eukaryotic cells and prokaryotic cells?

A

In eukaryotic cells it’s in the mitochondria, for prokaryotic cells it’s the inside of the plasma membrane

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14
Q

In photosynthesis how is chemiosmosis used?

A

To harvest light energy

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15
Q

What else is chemiosmosis called?

A

Oxidative phosphorylation - because oxygen is necessary for the process to work

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16
Q

What is the first step or group of steps in the catabolism of glucose for energy?

A

Glycolysis

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17
Q

Where does glycolysis take place in cells?

A

The cytoplasm

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18
Q

What are the 2 ways that glucose enters cells?

A

1) active transport against a concentration gradient

2) facultative diffusion through a group of proteins called GLUT proteins

In both insulin is needed in these processeses

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19
Q

What is the starting product of glycolysis and end product of it?

A

Starts with one 6-Carbon glucose molecule and ends with 2 3-Carbon pyruvate molecules

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20
Q

Glycolysis has 2 main stages in which the steps fall into, what are they?

A

First half is the energy requiring steps where the glucose is split into 2 3-Carbon substrates

Then the second half is energy releasing steps where energy is extracted in the form of ATP and NADH

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21
Q

Briefly describe the starting molecules and substrates along with the enzymes in every reaction of glycolysis in order

A

1) glucose is phosphorylated using an ATP molecules forming glucose-6-phosphate (enzyme is Hexokinase)

2) preparatory step for the splitting of sugar to two three carbon molecules (enzyme phosphoglucoseisomerase) substrate is now fructose 6-phosphate

3) a second ATP molecule adds energy to the substrate (this is done by phosphofructokinase) is now fructose 1, 6-biphosphate

4) fructose biphosphate aldose cleaves the molecule into 2 3-carbon sugars (dihydroxyacetone phosphate and glyceraldehyde 3-phosphate) molecules are isomers of each other

5) since only the glyceraldehyde 3-phosphate can move on in glycolysis, dihydroxyacetone phosphate is rearranged by triose phosphate isomerase into glyceraldehyde 3-phosphate

-(Now in energy releasing steps)-

6) Glyceraldehyde-3-phosphates are oxidized producing 2 high energy NADHs done by enzyme glyceraldehyde 3-phosphate dehydrogenase (NAD+ MUST be available for this step to proceed, dependent on oxygen being available) are now two 1,3-Biphosphoglycerate

7) phosphoglycerate kinase then converts it into 3-phosphoglycerate and 2 ATPs are produced (1 from each molecule)

8) isomeration of the substrates occurs placing the phosphate group on the middle carbon, it is now 2-phosphoglycerate (done by phosphoglycerate mutase)

9) the enzyme enolase catalyzes the dehydration reaction releasing 2 H2O(1 per molecule) and is now phosphoenolpyruvate

10) pyruvate kinase converts the molecule into pyruvate (2 3-carbon sugars) 2 ATPs are produced (1 from each molecule)

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22
Q

What is the net balance of molecules from glycolysis?

A

-2 ATP (4 produced but 2 were used in first half of glycolysis, so a net of 2)

-2 NADH

-2 pyruvate molecules

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23
Q

If oxygen is present what happens to the pyruvate molecules?

A

They continue to be catalyzed via aerobic respiration

-if no oxygen is present they become lactate

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24
Q

What is the rate limiting enzyme for glucose metabolism seen in the first half of gylcolysis

A

Phosphofructokinase, it is allosterically activated by high levels of ADP

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25
Q

What enzyme is responsible for the rate limiting step near the end of glycolysis?

A

Pyruvate kinase

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26
Q

Once glucose forms glucose-6-phosphate what can no longer happen?

A

It now cannot cross back out of the cell, it is a more reactive form of glucose aswell.

27
Q

If oxygen is available pyruvate now enters where from the cytoplasm?

A

The mitochondria (site of cellular respiration)

28
Q

Pyruvate is converted into what before it enters the citric acid cycle, in other words describe what happens in the “bridge step”

A

Pyruvate is converted to an acetyl group and then transferred to a carrier compound called coenzyme A (derived from vitamin B5), this results in a compound called acetyl CoA and can now continue to the citric acid cycle

29
Q

What happens chemically while pyruvate is broken down into acetyl CoA?

A

First a carboxyl group is removed from pyruvate releasing CO2 (first single carbon released from the original glucose) this occurs twice per glucose.

The resulting acetyl groups electrons are picked up by an NAD+ forming NADH

The acetylene group is transferred to coenzyme A forming acetyl CoA

30
Q

In presence of oxygen acetyl CoA delivers its 2-Carbon acetyl group to a 4-Carbon molecule in the citric acid cycle inside the mitochondrial matrix forming what?

A

A 6-carbon molecule called Citrate

31
Q

The citric acid cycle removes the rest of the single carbon atoms in the form of what molecule?

A

CO2

32
Q

In the breakdown of pyruvate to acetyl CoA what else is made per glucose?

A

2 CO2, 2 NADH, and 2 Acetyl CoA per glucose (1 per pyruvate)

33
Q

What is the net gain of molecules in the citric acid cycle? (Per glucose)

A

Per glucose 4 CO2, 6 NADH, 2 FADH2, and 2 ATPs are made (per acetyl CoA, it is half of the molecules listed)

34
Q

describe the substrates and enzymes in every step of the citric acid cycle along with what happens chemically

A

1) first acetyl CoA (2C) reacts with oxaloacetate (4C) forming the 6-Carbon molecule citric acid (Citrate) done through the enzyme citrate synthase. The acetyl CoA along with a sulfhydryl group is released and recycled (availability of ATP controls this step, increase of ATP results in decrease of rate of reaction)

2) isocitrate is produced aided by the enzyme aconitase

3) isocitrate is oxidized releasing CO2, the two electrons are used to reduce NAD+ to NADH, in end it produces a now 5-Carbon molecule Alpha-ketoglutarate, catalyzed by isocitrate dehydrogenase

4) alpha-ketoglutarate is oxidized and decarboxylated producing a CO2, and two electrons which reduce NAD+ to NADH, results in a 4-Carbon molecule called succinyl CoA catalyzed by the enzyme alpha-ketoglutarate dehydrogenase

5) made into succinate by succinyl-CoA synthetase, energy from this reaction is used to make ADP into ATP, in some cells like liver it is a guanine phosphate (GDP) that is converted into a GTP

6) made into fumarate from succinate dehydrogenase, it also reduced an FAD to a FADH2, and FADH2 goes to the ETC attached to inner mitochondrial membrane

7) malate is produced by enzyme fumarase, H2O is added to the substrate

8) malate is oxidized into oxaloacetate by enzyme malate dehydrogenase producing 2 electrons which reduce NAD+ to NADH

-oxaloacetate then proceeds to restart cycle by reacting with acetyl CoA

35
Q

How many turns does the citric acid cycle go for each glucose?

A

2

36
Q

every NADH and FADH2 that is made goes where?

A

The electron transport chain

37
Q

Most of ATP is generated where?

A

In the electron transport chain or more specifically chemisomsosis

38
Q

The ETC is a series of electron carriers that undergo redox reaction causing hydrogen ions to do what?

A

Diffuse out of the intermembrane space and into the matrix powering ATP synthese

39
Q

What does ATP synthase?

A

Phosphorylates ADP to make ATP

40
Q

The ETC at the endpoint results in oxygen and the resulting hydrogen ions, together they produce…

A

Metabolic water

41
Q

What happens in protein complex 1 in the ETC?

A

NADH enters the ETC, here it’s called NADH dehydrogenase and pumps 4 H+ from the inner membrane space into the matrix

42
Q

The Q and Complex 2 of ETC does what?

A

Receive FADH2, which bypasses complex 1 thus it pumps fewer hydrogen ions into the matrix

43
Q

What happens in complex 3 of ETC?

A

It pumps hydrogen ions across the membrane into the matrix and then passes electrons to cytochrome c

44
Q

What happens in complex 4 of ETC? Be specific, what contents does it have? What gradient is involved?

A

The cytochromes of this complex contain iron and copper atoms and are able to hold oxygen tightly until it is completely reduced by electrons from the chain, the reduced oxygen picks up 2 hydrogens from the surrounding medium to make water, further enhancing the hydrogen ion concentration gradient (low in the matrix and high in the intermembrane space)

45
Q

Chemiosmosis is powered by…

A

A concentration gradient (of hydrogens) as well as an electrochemical gradient

46
Q

Hydrogen ions can not pass freely through the inner mitochondrial membrane so how do they get through?

A

By a large integral membrane protein complex that is an enzyme called ATP synthase resulting in an ATP

47
Q

NADH entering the mitochondria costs energy in certain tissues where? And what does it cost specifically?

A

It costs ATP, reducing the net amount. Seen in tissues like muscle and brain

48
Q

What percent of energy contained in glucose is extracted in glucose metabolism? Where does the remaining percent go?

A

34% is extracted as energy, the rest is released as heat (entropy).

49
Q

In the end what is the net amount of ATP made per glucose molecule? Where does each ATP molecule come from? Show the equation

A

30 ATP come from 10 NADH molecules (3 each), 4 ATP comes from 2 FADH2 (2 each), then 2 net ATPs are made directly in glycolysis and the citric acid cycle (remember 4 are made in glycolysis but 2 are used as-well) this results in a net of 38 ATP. BUT in skeletal muscle and brain cells it is -2 due to NADH. So 36 ATP in these cells which are most cells in the human body.

50
Q

In order for reuse in glycolysis NADH must be…

A

Oxidize into NAD+

51
Q

Those that use organic molecules to generate NAD from NADH instead of oxygen present is called…

A

Fermentation, overall the processes are called anaerobic cellular respiration

52
Q

What do methanogens do for oxidizing NADH?

A

This type of archea used methane to oxidize NADH

53
Q

Some bacteria use what compound to regenerate NAD from NADH?

A

Hydrogen sulfide

54
Q

When is lactate produced?

A

When pyruvate is converted to lactate in order to regenerate NAD+ for glycolysis to continue (in oxygen debt environments)

55
Q

When can lactate be converted back into pyruvate? And where?

A

It goes to the liver where it can be converted into pyruvate when oxygen is present again

56
Q

Alcohol fermentation is carried out by what? What is the product?

A

Yeast, and it makes ethanol

57
Q

What are the steps in alcohol fermentation?

A

A carboxyl group is first removed from pyruvate as a CO2 producing acetaldehyde then the oxidation of NADH to NAD+ by alcohol dehydrogenase reduces acetaldehyde into ethanol

58
Q

Some bacteria are facultative aerobic and some are obligate anaerobes meaning what?

A

Facultative anaerobes can alternate between anaerobic and aerobic metabolism while obligate anaerobes die in the presence of oxygen and rely on anaerobic metabolism

59
Q

What happens when blood sugar levels drop?

A

Glycogen is hydrolyzed into glucose-1-phosphate which is converted to glucose-6-phosphate and can then enter glycolysis

60
Q

Where is fructose converted into glucose?

A

In the liver by a process called gluconeogenesis

61
Q

All amino acids that enter the pathway of glucose catabolism need what to happen chemically? What happens to the byproduct of this reaction?

A

They need to have their amino group removed (deamination) which is then converted into ammonia (toxic). The liver then synthesizes urea from 2 ammonia molecules and a CO2 molecule which leaves the body as urine

62
Q

Cholesterol synthesis starts with what groups? Closely related to the Krebs cycle

A

Acetyl groups

63
Q

What needs to happen to glycerol to enter glycolysis?

A

It needs to be phosphorylayed

64
Q

What happens in beta oxidation and how does it get to the citric acid cycle?

A

Beta oxidation catabolizes fatty acids taking place in the matrix of the mitochondria, these fatty acids are made into 2-Carbon units of acetyl which form acetyl CoA and enters the citric acid cycle

(Biology 211) Cellular Biology (12 decks)

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