Chapter 6 - Cellular Respiration

Question 1

cellular respiration

Answer 1

the process by which cells create usable energy in the form of ATP from a series of
biochemical reactions, involving the breakdown of glucose

Question 2

glucose

Answer 2

a simple 6-carbon sugar molecule with the formula C6H12O6

Question 3

ATP 

Answer 3

adenosine triphosphate, a high energy molecule that, when broken down, provides energy for cellular processes

Question 4

aerobic cellular respiration

Answer 4

cellular respiration that occurs in the presence of oxygen. Involves three stages, during which glucose and O2 are converted into ATP, CO2, and water

Question 5

anaerobic fermentation

Answer 5

a metabolic pathway that occurs in the absence of oxygen. Involves glycolysis, followed by further reactions that convert pyruvate into lactic acid in animals, or ethanol and CO2 in yeast

Question 6

glycolysis 

Answer 6

the first stage of aerobic cellular respiration in which glucose is converted to two pyruvate molecules
C6H12O6 + 2ADP & Pi + 2NAD(+) + 2H(+) = 2 pyruvate + 2ATP + 2NADH

Question 7

Krebs cycle

Answer 7

the second stage of aerobic cellular respiration, where multiple reactions occur to create ATP, NADH, FADH2, and the waste product CO2. Also known as the citric acid cycle or TCA cycle
2 acetyl-CoA + 2ADP & Pi + 6NAD(+) + 2FAD + 10H(+) = 4CO2 + 2ATP + 6NADH + 2FADH2

Question 8

electron transport chain

Answer 8

the third stage of aerobic cellular respiration, in which a series of protein complexes embedded in the inner membrane of a mitochondrion harness the stored energy in NADH and FADH2 to generate large amounts of ATP
6O2 +12H(+) + 26 or 28ADP & Pi + 10NADH + 2FADH2 = 6H2O + 26 or 28ATP + 10NAD(+) + 2FAD 14H(+)

Question 9

mitochondrion (pl. mitochondria)

Answer 9

a double-membrane-bound organelle that is the site of the second and third stages of aerobic cellular respiration

Question 10

cytosol

Answer 10

the aqueous fluid that surrounds a cell’s organelles inside the plasma membrane

Question 11

mitochondrial matrix

Answer 11

the space inside the inner membrane of a mitochondrion. The site of the Krebs cycle

Question 12

crista (pl. cristae) 

Answer 12

the folds of the inner membrane of a mitochondrion. The site of the electron transport chain

Question 13

pyruvate

Answer 13

a three-carbon molecule that can be formed from the breakdown of glucose via glycolysis

Question 14

nicotinamide adenine
dinucleotide (NAD)

Answer 14

a coenzyme that acts as a proton (H+) and electron carrier in cellular respiration. NAD can cycle between its NAD+ and NADH forms, depending on the reaction it takes part in

Question 15

flavin adenine dinucleotide (FAD)

Answer 15

a coenzyme that acts as a proton (H+) and electron carrier in cellular respiration. FAD can cycle between its FAD and FADH2 forms, depending on the reaction it takes part in

Question 16

coenzyme A

Answer 16

a large organic non-protein molecule that plays a key role in the modification of pyruvate to allow it to enter the Krebs cycle. Also known as CoA

Question 17

acetyl-CoA

Answer 17

the product of the link reaction where pyruvate is conjugated to coenzyme A, creating the primary input into the Krebs cycle

Question 18

ATP synthase 

Answer 18

an enzyme in the inner mitochondrial membrane that uses the concentration gradient of H+ to synthesise ATP from ADP and Pi

Question 19

catalyse

Answer 19

to increase the rate of a reaction

Question 20

yeast 

Answer 20

unicellular eukaryotic organisms from the kingdom Fungi

Question 21

lactic acid fermentation

Answer 21

the process of anaerobic fermentation in animals, where pyruvate produced via glycolysis is converted to lactic acid

Question 22

lactic acid

Answer 22

a 3-carbon molecule that is the product of anaerobic fermentation in animals. Also known as lactate

Question 23

ethanol

Answer 23

a 2-carbon alcohol molecule that is produced along with carbon dioxide during anaerobic fermentation in yeast, bacteria, and plants

Question 24

ethanol fermentation 

Answer 24

the process of anaerobic fermentation in yeasts, where pyruvate produced via glycolysis is converted to ethanol and carbon dioxide. Also known as alcohol fermentation

Question 25

optimal

Answer 25

the point at which for a given condition (e.g. temperature), the maximum function of an enzyme occurs. Also known as optimum

Question 26

denature

Answer 26

the disruption of a molecule’s structure by an external factor such as heat

Question 27

pH

Answer 27

a scale used to measure the acidity or basicity of an aqueous solution

Question 28

saturation point

Answer 28

the point at which a substance
(e.g. an enzyme) cannot receive more of another substance (e.g. a substrate)

Question 29

enzyme inhibitor

Answer 29

a molecule that binds to and prevents an enzyme from functioning

Question 30

competitive inhibitor

Answer 30

a molecule that hinders an enzyme by blocking the active site and preventing the substrate from binding

Question 31

non-competitive inhibitor 

Answer 31

a molecule that hinders an enzyme by binding to an allosteric site and changing the shape of the active site to prevent the substrate from binding

Question 32

allosteric site

Answer 32

a region on an enzyme that is not the active site

Question 33

reversible inhibition

Answer 33

enzyme inhibition that involves weaker bonds that can be overcome

Question 34

irreversible inhibition

Answer 34

enzyme inhibition that involves stronger bonds that cannot be broken

Question 35

end-product inhibition 

Answer 35

a form of inhibition where the final product in a series of reactions inhibits an enzyme in an earlier reaction in the sequence

Question 36

fossil fuel

Answer 36

fuel that formed over tens of millions of years from the remains of dead organic material. Fossil fuels are considered non-renewable

Question 37

non-renewable

Answer 37

refers to a resource that is replenished at a slower rate than it is being used, meaning that it will eventually run out

Question 38

biofuel

Answer 38

fuel created from organic material known as biomass

Question 39

biomass

Answer 39

organic material, including plants, animal by-products, and biological waste material. Biomass can be sourced from many industries, including farming, forestry, and food manufacturing

Question 40

renewable

Answer 40

refers to a resource that can typically be replenished at the same (or faster) rate than it is being used, meaning it is unlikely to run out

Question 41

carbon neutral

Answer 41

a state in which there is no net release of carbon dioxide into the atmosphere, meaning that there is a balance between the amount of CO2 that is emitted during combustion of a fuel and how much was originally
absorbed during the formation process of that fuel

Question 42

fermentation 

Answer 42

the anaerobic chemical breakdown of high-energy organic molecules, typically via the action of enzymes. For many plants, fermentation involves the conversion of glucose to ethanol and carbon dioxide

Question 43

bioethanol 

Answer 43

a type of biofuel that is produced via the anaerobic fermentation of plants such as sugarcane or corn

Question 44

hydrolysis 

Answer 44

a chemical reaction in which water is used to break down the chemical bonds of a substance

Question 45

food vs fuel debate

Answer 45

a central concern of large-scale biofuel manufacturing that questions the validity of using arable farmland to produce fuel, rather than food

Question 46

first-generation biofuels 

Answer 46

biofuels produced from edible food crops such as corn or sugarcane. These compete directly with agricultural land

Question 47

second-generation biofuels 

Answer 47

biofuels produced from non-edible crops such as agricultural and forestry residues and municipal waste. These typically compete less with agricultural land

Question 48

The process of creating bioethanol:

Answer 48

Deconstruction - The biomass is treated to help break it down to a point that increases its surface area enough to make the fermentation process more efficient. This is done by breaking down the cell wall and cellulose, and can occur via a range of different methods, including biological approaches such as enzyme breakdown, chemical approaches such as exposure to acids, physical approaches such as mashing and grinding, and/or physiochemical approaches such as heating.

Digestion by enzymes - The broken down biomass is then exposed to enzymes (such as amylase) which break down the starch and cellulose and convert them into glucose and other sugars. This breaking down of polysaccharides is aided by the presence of water in a process known as hydrolysis.

Ethanol fermentation - Yeast is used to facilitate the anaerobic fermentation of the sugars produced in step 2. Here, a large amount of ethanol is produced as a product of this fermentation. The ethanol diffuses out of the yeast cells and is harnessed for biofuel.

Purification and dehydration The ethanol is distilled via the removal of water, converting it into a usable form called biofuel. The biofuel is then purified and is ready to be used as liquid fuel.