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MCAT Biology > Cellular Metabolism > Flashcards

Cellular Metabolism Flashcards

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1
Q

Function of coenzyme Q10

A

Found in inner mitochondrial Membrane and helps make ATP. Also counters harmful effects of free radicals

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2
Q

Cycle Names of Aerobic Cellular Metabolism: 4 steps

A
  1. Glycolysis
  2. Pyruvate Decarboxylation
  3. Krebs cycle
  4. Electron Transport Chain
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3
Q

Autotrophs

A

Organisms that are capable of using the sun’s energy to create organic molecules (glucose) that can store energy in their bonds. Example: plant

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4
Q

Photosynthesis

A

anabolic process by plants

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5
Q

Heterotrophs

A

Organisms that derive their energy by breaking down organic molecules made by plants and harness the power that is held in the bonds of these molecules. Example: humans (catabolic process)

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6
Q

Glucose formula

A

C6H12O6

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7
Q

Formation of Glucose by autotrophs (Endothermic Process)

A

Breaking of C-O bonds in CO2 and O-H bonds in H2O. Atoms are rearranged into glucose and energy is stored in chemical bonds

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8
Q

Photosynthesis Formula

A

6 CO2 + 6 H2O + ENERGY –> C6H12O6 + 6 O2

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9
Q

Cellular Respiration Formula

A

C6H12O6 + 6 O2 –> 6 CO2 + 6 H2O + ENERGY

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10
Q

3 Energy Carriers

A
  1. ATP
  2. NAD+
  3. FAD

These molecules act as high-energy electron shuttles between cytoplasm and mitochondria.

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11
Q

Adenosine triphosphate (ATP) Function

A

Primary energy currency of cell. Rapid formation and degradation allow for energy to be stored and released as needed.

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12
Q

ATP Structure

A
  1. Nitrogenous base adenine
  2. sugar ribose (2’ has OH)
  3. three phosphate groups (Energy stored here)
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13
Q

NAD+ & FAD functions

A
  • coenzymes capable of accepting high-energy electrons during glucose oxidation.
  • electrons come in the form of hydride ions.
  • They pass thru the electron transport chains and allow ATP to be generated from their stored energy.
  • They are first Reduced during glycolysis and Kreb’s cycle (NADH and FADH2) (gain electrons
  • They are then Oxidized during Electron transport chain (Back to NAD+ and FAD)
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14
Q

Energy in ATP is liberated through 2 processes

A
  1. Glycolysis

2. Cellular Respiration

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15
Q

Glycolysis- definition

A

Series of reactions that break glucose into 2 smaller organic molecules

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16
Q

Location of Glycolysis

A

Cytoplasm.

Occurs WITH or WITHOUT oxygen

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17
Q

Inputs of glycolysis (reactants)

A
  1. Glucose
  2. 2 ATP
  3. 2 NAD+
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18
Q

Outputs of glycolysis (product)

A
  1. Two Pyruvates
  2. 4 ATP
  3. 2 NADH
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19
Q

Net Reaction for glycolysis

A

Glucose + 2 ADP + 2 Pi + 2NAD+ –> 2 Pyruvate + 2ATP + 2 NADH + 2 H+ + 2H2O

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20
Q

Total ATP production

A

Glycolysis makes 4 ATP molecules, but the process uses 2 ATP molecules so the net production is 2 ATP molecules.

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21
Q

Substrate-level Phosphorylation

A

The direct generation of ATP from ADP and Pi

22
Q

Fate of pyruvate based on character of cell environment:

A
  1. Aerobic Organisms ( Use of O2)- undergoes further oxidation
  2. Anaerobic Organisms (Oxygen free)- undergoes process of fermentation.
23
Q

Obligate/facultative aerobes/ anaerobes

A

Obligates- require that designated environment

Facultative- prefer an environment over the other but can survive in either.

24
Q

Fermentation

A
  • oxygen free process.
  • Reduces pyruvate to either ethanol or lactic acid.
  • Oxidizes NADH to NAD+
  • Term “fermentation” included glycolysis plus reduction of pyruvate.
25
Q

Alcohol Fermentation

A
  • Occurs in yeast and some bacteria
  • FIRST-Pyruvate (3C) is decarboxylated to acetaldehyde (2C).
  • SECOND- Acetaldehyde (2C) is reduced by NADH to ethanol (2C). Generating NAD+
26
Q

Lactic Acid Fermintation

A
  • Occurs in some fungi and bacteria, and humans in times of O2 scarcity
  • Pyruvate (3C) is reduced to lactic acid (3C)
  • NADH is oxidized into NAD+
  • Lactic Acid decreases the local pH.
27
Q

Cori Cycle

A
  • Conversion of Lactic acid back to pyruvate in order for cellular respiration to continue
  • Oxygen debt: amount of oxygen needed to do this.
28
Q

3 Key phases of Cellular Respiration

A
  1. Pyruvate decarboxylation
  2. Citric Acid cycle ( Kreb’s cycle)
  3. Electron Transport Chain
29
Q

Pyruvate Decarboxylation

A
  • Step doesn’t need O2 but it only occurs when cell commits to aerobic respiration.
  • Pyruvate is transported from cytoplasm into mitochondrial matrix.
  • Each Pyruvate loses a CO2
  • Remaining acetyl (2 C) binds to coenzyme A . FORMING acetyl-CoA
  • For each pyruvate an NAD+ is reduced to NADH
30
Q

Results of pyruvate decarboxylation

A

2 acetyl-coA (2 C)
2 CO2
2 NADH

31
Q

Citric Acid Cycle

A
  • First acetyl-CoA (2 C) combines with oxaloacetate (4 C) forming Citrate (6 C).
  • Each cycle releases 2 CO2
  • Doesn’t directly generate much energy, only 1 ATP per cycle.
  • But can generate high-energy electrons, 3 NADH and 1 FADH2 per cycle
32
Q

Total Product of Krebs Cycle

A
  • 6 NADH
  • 2 FADH2
  • 2 ATP (from GTP)
33
Q

Electron Transport Chain

A
  • Here we use oxidative phosphorylation to use the energy from the reduced NADH and FADH2
34
Q

Oxidative Phosphorylation

A
  • process by which electrons from NADH and FADH2 are passed along an assembly line of carriers that release free energy with each transfer.
  • That free energy is put into ATP production.
  • Carriers are enzymes known as cytochromes
35
Q

Cytochromes

A
  • enzymes used as carriers of electron in electron transport chain.
  • each contain a central iron atom that undergo reversible redox reactions as electrons bind and release.
  • Because iron can be present in more than one oxidation state, it’s a likely candidate to participate in redox reactions.
36
Q

3 Complexes of Cytochromes

A
  • NADH dehydrogenase (complex I)
  • b-c1 complex (Complex III)
  • Cytochrome oxidase (complex IV)
37
Q

Process of Electron Transfer

A
  • First: NADH gives electron directly to Flavin mononucleotide (FMN- part of complex I).
  • Electrons are then passed to carrier Q (ubiquinone- a hydrophobic molecule, NOT an enzyme)
  • Carrier Q passes electrons to complex III, which are then donated to complex IV.
  • Oxygen then takes the electrons from complex IV-protein cytochrome a3 along with 2 protons and makes water.
    • NOTE- if oxygen is in debt, electrons cannot be picked up from cytochrome a3.
38
Q

Amount of ATP produced from each NADH

A

3 ATP molecules from each NADH.

EXCEPT 2 ATP molecules from NADH produced in cytoplasm.

39
Q

Amount of ATP produced from each FADH2

A

2 ATP molecules are generated, because electrons are given to complex II, Succinate-Q-oxidoreductase, So electrons travel a shorter distance to get to oxygen and so less energy is extracted from them.

40
Q

Cyanide

A

Poison that blocks the final transfer of electrons to O2.

41
Q

Dinitrophenol (DNP)

A

Poison that destroys the mitochondriaon’s ability to generate a useful proton gradient that is necessary for effective ATP generation.

42
Q

Proton Gradient

A

-necessary in inner mitochondrial membrance and links the oxidation of NADH and FADH2 to ADP phosphorylation.

43
Q

Proton-Motive Force

A
  • Created by the carriers giving up electrons causing free protons to pass and accumulate into the mitochondrial matrix.
  • ETC then pumps these ions out of the matrix and into the intermediate space at each protein complex.
  • This causes the intermembrane to be positive and acidic.
  • so electrochemical gradient drives H+ passively back across the inner membrane into the mitchondrial matrix.
44
Q

ATP synthases

A

Enzyme complexes are used for H+ ions to pass back into the matrix and the energy released allows for phosphorylation of ADP back to ATP.

45
Q

ATP production per Glucose Molecule

A 
Glycolysis:(8 ATP)
  -2 ATP Used
  -4 ATP made (substrate)
  -2 NADH--> 4 ATP (oxidative)
Pyruvate decarboxylation 
  - 2NADH--> 6 ATP (oxidative)
Cirtric Acid Cycle
  -6 NADH --> 18 ATP (oxidative)
  -2 FADH2--> 4 ATP (oxidative)
  - 2 GTP --> 2 ATP (substrate)

Total of 36 ATP

46
Q

Alternate Energy Sources (3)

A

Carbohydrates
Fats
Protein

47
Q

Carbohydrates

A

Sugar polymers are broken down during digestion and stored in the liver for later use in a form known as glycogen.

48
Q

Fats

A
  • Stored in adipose tissue as triglycerides.
  • for long term storage, the fatty acids are esterified and it become glycerol.
  • Glycerol can be converted to PGAL (intermediate in glycolysis) but real energy of fats is stored in the fatty acids.
49
Q

Proteins

A

Used only when carbohydrates are insufficient.

Amine moiety is removed resulting in an acid that can be converted into acetyl-CoA or intermediates of TCA cycle.

50
Q

Beta-oxidation

A

Fatty acid is first activated in cytoplasm in a process requiring 2 ATP, then transported to mitochondria matrix and undergoes rounds of generating acetyl-coA.(total of 24 rounds) generated 24 NADH and 24 FADH2, close to a 100 ATP production

51
Q

Transaminases

A

Removes the amine moiety from amino acids resulting in molecules known as alpha-keto acids, that are able to convert into acetyl-CoA

MCAT Biology (5 decks)

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