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Biology of Cells and Organisms (sem 1) > Cellular Respiration > Flashcards

Cellular Respiration Flashcards

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1
Q

What is energy?

A

The capacity to do work

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2
Q

What is potential energy?
What is kinetic energy?
What are their respective symbols?

A

Potential: stored energy (Ep)
Kinetic: expressed as movement (Ek)

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3
Q

What happens to unused leftover energy?

A

Dissipated as heat

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4
Q

What is metabolism?

A

The sum of all chemical reactions occurring in cells

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5
Q

What do organisms convert chemical energy of fuel molecules into?

A

Organisms convert chemical energy of fuel molecules into useable energy in the form of adenosine triphosphate (ATP).

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6
Q

Name the process involving the breakdown of carbohydrates.

A

Glycolysis

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7
Q

Name the process involving the breakdown of lipids.

A

Beta-oxidation

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8
Q

Is glycolysis or beta-oxidation preferred by cells? Why or why not?

A

Glucose breaks down quickly and glycolysis therefore is faster and the preferred process in cells. Lipid breakdown and therefore beta-oxidation is much slower.

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9
Q

What is an ATP molecule composed of?

Where is the energy of an ATP molecule specifically stored?

A

It is composed of adenosine, consisting of the nitrogenous base adenine and the sugar ribose, and 3 phosphate groups.

High energy covalent bonds exist between the phosphate groups.

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10
Q

What is an exergonic and endergonic reaction?

A

Exergonic: release of energy
Endergonic: absorption of energy

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11
Q

What is ATP derived from and how does this occur?

Explain the purpose of reversing this process also.

A
  • derived from ADP+Pi
  • energy released from an exergonic reaction is sued to phosphorylate ADP (add one phosphate Pi group) to form ATP
  • when a cell requires energy for an endergonic reaction, the phosphate group is broken off ATP and the lost energy from this bond is used to drive an endergonic reaction in the cell.
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12
Q

What are enzymes?

A

Enzymes are biological catalysts that lower the activation energy in reactants (substrates), thereby speeding up reactions.

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13
Q

How do enzymes affect substrates?

A

Once blinded to a substrate, an enzyme changes the substrate’s conformation so that the amount of energy required to break down/fuse substrates is LOWERED.

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14
Q

What is substrate channeling? What type of pathway is formed?

A

Enzymes for particular pathways are often physically linked, forming substrate channelling. This forms electron transport pathways.

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15
Q

Name the type of transfer reactions involved with electron transport pathways.

A

Oxidation-reduction reactions
(Oxidation: loss of electrons)
(Reduction: gain of electrons)

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16
Q

Energy in cells are generally derived from the breakdown of compounds such as…?

A

Glucose (carbohydrates) or lipids

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17
Q

The products of what reactions act as substrates for cellular respiration?

A

The products of glycolysis and beta oxidation act as substrates for cellular respiration.

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18
Q

Give a brief summary of cellular respiration.

A
  • first, oxidation of fuel molecules occurs which is where electrons are removed from C-C and C-H bonds.
  • the electrons extracted from these bonds are then accepted by the co-enzymes NAD+ and FAD
  • which are then passed down electron transport chains to the final electron acceptor, driving proton pumps that are coupled to the synthesis of ATP
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19
Q

Where does glycolysis occur in the cell?

A

Occurs in the cytoplasm of the cell (OUTSIDE mitochondria)

20
Q

Where is glucose derived from?

A

Polysaccharides such as starch (plants) and glycogen (animals) are broken down by catalysed hydrolysis into glucose.

21
Q

Does glycolysis only occur in prokaryotic and/or eukaryotic cells?

A

Glycolysis occurs in both.

22
Q

Explain the stages of glycolysis and emphasise where energy is consumed and produced.

A
  • 2 molecules of ATP are used to phosphorylate glucose (6C) in order to form a 6 carbon sugar diphosphate (2 phosphate groups attached). Here, energy is CONSUMED. This 6 C sugar diphosphate is then split into two 3C sugar phosphate molecules.
  • the oxidation of both 3C sugar phosphate molecules into two pyruvate molecules drives ATP synthesis, producing 4 ATP molecules with a net energy gain of 2 ATP in total. Here, energy is PRODUCED.
  • in addition, 4 electrons and 2 H+ atoms are transferred to 2 NAD+ electron acceptors, producing 2 NADH molecules in total.
23
Q

What are the final products of glycolysis?

A
  • net gain of 2 ATP
  • 2 NADH molecules produced
  • 2 pyruvate (3C) molecules produced
24
Q

What happens to the pyruvate molecules at the end of glycolysis when:

  • oxygen is absent?
  • oxygen is present?
A

If oxygen is absent, fermentation occurs. Here the pyruvate molecules are converted into either lactic acid (bacteria, animals) or ethanol (yeast, plants) in order to recycle NADH.

If oxygen is present, the 2 pyruvate molecules enter the matrix (innermost compartment) of the mitochondrion and are converted into acetyl co-enzyme A (2C) in preparation for the Krebs cycle.

25
Q

What is beta-oxidation?

A

Beta-oxidation occurs instead of glycolysis when lipids are the starting compound instead of glucose/carbohydrates.

26
Q

Explain the steps of beta-oxidation.

A
  • before beta oxidation occurs, lipids are hydrolysed into free fatty acids and glycerol. It is these fatty acids that are used as the substrate for beta-oxidation.
  • once the fatty acid arrives at the mitochrondrial matrix, the chains of fatty acids are broken 2 carbons at a time.
  • the energy lost from these broken C-C bonds is conserved in C-H bond in acetyl coA
  • FADH2 is first produced then NADH
27
Q

What are the products of beta-oxidation?

A
  • acetyl coenzyme A

- FADH2 and NADH

28
Q

What is the substrate used in the Krebs cycle?

A

Acetyl coenzyme A

29
Q

Explain the steps of the Krebs cycle.

A
  • Acetyl CoA (2C) combines with a 4C molecule (oxaloacetate) to form the product citrate (6C).
  • Two carbons are stripped off as CO2 and the resultant 4C molecule (oxaloacetate) continues the cycle again.
  • 1 ATP is formed per cycle but the main products are NADH AND FADH2, which now contain the energy liberated when the carbons were removed.
30
Q

What are the products of the Krebs cycle per acetyl coA? How would you calculate these amounts per glucose molecule?

A
  • 3 NADH and 1 FADH2
  • 1 ATP
  • 2 CO2

Multiply by two to calculate amounts per glucose because two acetyl CoA molecules are produced per glucose

31
Q

Where does the Krebs cycle occur?

A

It occurs in the mitochrondrial matrix.

32
Q

Where does the Electron transport chain occur?

A

It occurs in the inner membrane of the mitochondrion.

33
Q

Explain the steps of the electron transport chain.

A
  1. NADH is oxidised to form NAD+ at the NADH dehydrogenase complex (embedded in the matrix). This complex expels H+ ions into the inner mitochondrial membrane, decreasing its pH.
  2. FADH2 is also oxidised to form FAD at the first cytochrome protein complex. Its removed electrons, along with those removed from NADH, are passed through several cytochrome electron-carrier protein complexes. Coupled with this transfer of electrons is the translocation of H+ protons from the matrix to the outer side of the inner mitochondrial membrane.
  3. The final cytochrome protein complex, cytochrome c oxidase, reduces one O2 molecule (coming from the cytosol) to two H2O molecules. Oxygen is therefore the final electron acceptor with water forming as the end product.
  4. The proton concentration gradient created by proton pumps provides enough energy for the phosphorylation of ADP and therefore ATP synthesis to occur. This reaction is catalysed by a protein complex called ATP synthase. Here, protons are able to move back down the concentration gradient (from inner membrane to matrix) thereby powering ATP synthesis (32-34 ATP) catalysed by ATP synthase.
  5. ADP enters the mitochrondrial matrix from the cytosol, and ATP exits from the matrix into the cytosol using an ATP/ADP transporter embedded in the inner mitochondrial membrane.
34
Q

Where are the electrons released in glycolysis and the citric acid cycle temporarily stored in?

A

The reduced electron carriers NADH and FADH2

35
Q

Why is the energy produced during the oxidation reactions of the electron transport chain variable?

A

Because some of the energy produced is used for other purposes in the mitochondria.

36
Q

What is fermentation?

A

2 pyruvate molecules at end of glycolysis are converted into either lactate by animals and bacteria, or ethanol by yeast and plants.

NADH produced from glycolysis is also recycled into NAD+ during fermentation.

37
Q

What is a byproduct of ethanol fermentation (yeast and plants)?

A

CO2

38
Q

Why is stirring a home brew of yeast an issue?

A

Stirring it oxygenates the home brew, therefore ethanol will no longer be produced and instead the yeast will revert to the Krebs Cycle and ETC, producing water.

39
Q

What type of system would the body of a short sprint runner use and why?

A
  • phosphagen system
  • cellular ATP reserves are only good for about 3 seconds, whereas cellular creating phosphate (stored in muscle cells) can be quickly converted into ATP to aid muscle contraction. This is good for 10 seconds, therefore more efficient for short sprint runners
40
Q

What happens when creatine phosphate stored in muscle cells is exhausted?

A
  • glycolysis kicks in
  • Krebs and ETC are too slow, and blood supply can’t maintain efficient enough oxygen levels
  • glycolysis is good for about 90 seconds (400m longer races)
41
Q

What is gasping after strenuous exercise necessary for?

A

To pay “oxygen debt”

42
Q

Why do some athletes “hit the wall” at the 2 hour (32km) stage?

A

Glycogen supplies are exhausted at this point and glycolysis is unable to proceed.

43
Q

Describe the similarities between mitochondria and chloroplasts.

A
  • both possess double membrane enclosing the organelles
  • both possess circular DNA which codes for certain enzymes required for the respective chemical reactions that take place
  • both said to have evolved from endosymbiosis (ancestral eukaryote consumed aerobic bacteria and photosynthetic bacteria)
  • both have the enzyme ATP synthase and therefore produce ATP
  • both have electron transport chains (embedded in the inner mitochondrial membrane and the thylakoid membrane)
44
Q

What molecules are exchanged between mitochondria and chloroplasts and how does this exchange occur?

A
  • oxygen produced in the light dependent reaction of photosynthesis is used as the final electron acceptor in the electron transport chain in cellular respiration
  • water produced in electron transport chain in cellular respiration is used as electron donor molecule in light dependent photosynthesis
  • CO2 produced in Krebs cycle is used in the Calvin cycle of photosynthesis
  • glucose produced at the end of the Calvin cycle of photosynthesis is converted into pyruvate which is converted into acetyl coA in the Krebs cycle of cellular respiration
45
Q

Describe the differences between mitochondria and chloroplasts.

A

Electron transport chains: final electron acceptor in mitochondria is oxygen, whereas the final e acceptor in chloroplasts is NADP.

Source of electrons: mitochondria derives electrons form glucose, whereas root source of electrons in chloroplasts is from the breakdown of water at photosystem II.

Types of electron acceptors: NADH AND FADH2 in mitochondria, NADPH only in chloroplasts.

ATP synthase is orientated differently: in mitochondria, ATP synthase releases protons from inner membrane to matrix, whereas in chloroplasts ATP synthase releases protons from thylakoid lumen into stroma

Biology of Cells and Organisms (sem 1) (17 decks)

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