8.2 Cellular Respiration HL

Question 1

oxidation and reduction

Answer 1

• oxidation: losing hydrogen atoms and electrons
• reduction: gaining hydrogen atoms and electrons

Question 2

electron carrier

Answer 2

substances that can take up electrons and give them up when required
- used to stagger the breakdown of energy so the released energy is not all lost as heat.

Question 3

name of the electron carrier molecule used in cellular respiration

Answer 3

• NAD+ (most common) -> NADH+H when reduced
• FAD+ (less common), FADH2 when reduced

Question 4

phosphorylation

Answer 4

addition of phosphate molecule to an organic molecule

Question 5

consequence of a molecule being phosphorylated

Answer 5

• molecules are more unstable and therefore more likely to react

Question 6

glycolysis reaction

Answer 6

1) ATP phosphorylates glucose twice, requires investment of two ATP molecules (exergonic reaction)
2) phosphorylated glucose (now Fructose-6-bisphosphate) is broken into two molecules of glycerate-3-phosphate (G3P)
3) each G3P has inorganic group (Pi) added. simultaneously, NAD+ is reduced by gaining H & 2e- to become NADH. in a series of remaining reactions, each molecule is converted into pyruvate, generating total of 4 ATP (2 net) through substrate specific phosphorylation

Question 7

glycosis reaction formula

Answer 7

Question 8

decarboxylation

Answer 8

removal of carbon dioxide molecule

Question 9

reactant and products of the link reaction

Answer 9

reactant: pyruvate, NAD+, CoA
product: Acetyl CoA, CO2, NADH

Question 10

events of the Krebs cycle

Answer 10

1) Acetyl CoA (2C) joins with oxaloacetate (4C) to form citrate (6C). occurs as an oxidation reaction & enzyme CoA is released
2) citrate is converted to isocitrate (isomer of citrate)
3) isocitrate (6C) is oxidized to alpha-ketoglutarate (5C) which results in decarboxylation & release of CO2. reduction of NAD+ occurs, forming one NADH molecule
4) alpha-ketoglutarate is oxidized to form 4C molecule which binds to CoA, forming succinyl CoA. through reduction, 2nd molecule of NADH is produced. decarboxylation produces 2nd molecule of CO2
5) succinyl CoA is converted to succinate (4C). one GPT (ATP) molecule is phosphorylated
6) succinate is converted into fumarate (4C) using an enzyme. FAD is reduced to a molecule of FADH2
7) fumarate is converted to malate (4C) through enzyme fumarase
8) malate converted into oxaloacetate. 3rd molecule of NADH is produced through reduction of NAD+. cycle then repeats for 2 full cycles (one per Acetyl CoA) for each molecule of glucose

Question 11

[STATE] sentences regarding glycolysis

Answer 11

• glycolysis occurs in both anaerobic and aerobic respiration
• glycolysis is an example of a metabolic pathway

Question 12

[STATE] sentences regarding Krebs cycle & transfer of electrons

Answer 12

• NADH and FADH2 are electron carriers formed during the Krebs cycle
• NAD+ is reduced to become NADH in the link reaction and Krebs cycle
• FAD is reduced to become FADH2 in the Krebs cycle
• NADH and FADH2 carry electrons to the electron transport chain on the mitochondrial inner membrane
• at the electron transport chain, FADH2 and NADH give electrons to electron carrier proteins
• movement of electrons through electron carrier proteins in the electron transport chain is used to pump protons (H+) across the inner mitochondrial membrane into the intermembrane space

Question 13

oxidative phosphorylation

Answer 13

where energy originally released from the oxidation of glucose is used to produce ATP from ADP and Pi

Question 14

chemiosmosis

Answer 14

use of energy held within proton gradient (created by transport of electrons by electron transport chain) to produce ATP

Question 15

[STATE] sentences regarding oxygen & hydrogen gradient

Answer 15

• oxygen is the final electron acceptor in aerobic cellular respiration
• formation of water in matrix at the end of electron transport chain helps maintain the hydrogen gradient between intermembrane space and matrix

Question 16

how mitochondria structure could evolve through natural selection

Answer 16

• if mitochondrial structure varied, those organisms with the mitochondria that produced ATP most efficiently would have the advantage -> they would have an increased chance of survival and would tend to produce more offspring -> these offspring would inherit the type of mitochondria that produce ATP more efficiently -> if this trend continued, the structure of mitochondria would gradually evolve to become more and more efficient

Question 17

evidence that suggests mitochondria were once free living prokaryotes

Answer 17

• 70s ribosomes
• double membrane
• naked circular DNA
• binary fission

Question 18

[STATE] sentence regarding electron tomography

Answer 18

• electron tomography enables scientists to view the dynamic nature of mitochondrial membranes

Question 19

[STATE] sentence regarding decarboxylation

Answer 19

• decarboxylation of glucose occurs in the linking reaction and Krebs cycle of aerobic respiration

Question 20

diagram of mitochondria

Answer 20

Question 21

function of the following mitochondrial structures: outer membrane, inner membrane, cristae, intermembrane space, matrix, ribosome and mtDNA

Answer 21

outer membrane:
- boundary of mitochondrion
- creates compartment within cell
- specialized for reactions & processes of aerobic respiration

inner membrane:
- contains electron transport chains & ATP synthase for oxidative phosphorylation

cristae:
- provides more surface area for oxidative phosphorylation

intermembrane space:
- has small volume so that high proton concentration can be generated rapidly

matrix:
- contains enzymes for the link reaction and Krebs cycle.
- where 70s ribosomes and naked circular DNA are present

ribosome:
- makes proteins needed for cellular respiration

mtDNA:
- contains genetic information, circular & naked

Question 22

[STATE] sentence regarding chemiosmotic theory

Answer 22

• Peter Mitchell’s proposal of the chemiosmotic hypothesis in 1961 led to a major shift in our understanding of cellular processes