Chapter 7

Question 1

what is the basic formula for cellular respiration

Answer 1

c6h1206 + 6O2 –> 6 Co2 + 6 H20

Question 2

is cellular respiration exergonic or endergonic? Catabolic or anabolic?

Answer 2

cellular respiration is a catabolic; exergonic reaction meaning that there is more energy in the reactants than in the products

Question 3

what constitutes as a loss of energy or as a gain of energy in regards to adenosine triphosphate alone?

Answer 3

if adp gains an inorganic phosphate to make atp that makes it gained energy and is therefore an endergonic reaction; if atp loses an inorganic phosphate to make adp and an inorganic phosphate making that an exergonic reaction

Question 4

why do cells need atp? why not use energy directly from glucose?

Answer 4

atp is the energy currency of the cell; glucose releases too much energy in the form of heat and barely stores any where as atp only releases a small amount of energy in the form of heat making atp the more efficient form of energy

Question 5

what is atp composed of

Answer 5

3 phosphate group, nitrogenous base adenine, and 5-carbon ribose

Question 6

what are the four stages of respiration and where do they take place

Answer 6

1) Glycolysis (Cytoplasm)
2) Pyruvate oxidation (in mitochondria - inner membrane space)
3) Krebs cycle/TCA/citric acid cycle/tricarboxylic acid - mitochondrial matrix
4) Electron transport chain - inner mitochondrial matrix

Question 7

based on the location of the krebs cycle what is the exception within the cycle

Answer 7

during the krebs cycle, despite its location being in the mitochondrial matrix, FADH2/FAD is found on the memrane in the etc in the second complex and so is succinate dehydrogenase (the enzyme used to reduce FAD into FADH2)

Question 8

what are the two main phases of glycolysis

Answer 8

the first five phases are known as the investment phase and the last five steps are known as the payoff phase; this is because during the investment phase we are “investing” two molecules of atp to phosphorylate molecules glucose and fructose 1-6 biphosphate in steps one and three and in the steps 7 and 10, pyruvate and phosphoglycerate become phosphorylated to produce atp

Question 9

how much atp and Nadh get produced as a resultof glycolysis

Answer 9

glycolysis alone technically produces 4 atp molecules but because of the fact that two need to be used in steps 1 and 3, glycolysis produces a net total of 2 atp molecules. In step 6, 1-3biphosphoglycerate gets oxidized with the help of the enzyme dehydrogenase and loses an H proton to give to NAD which gets reduced to NADH

Question 10

what are the most frequent enzymes used in glycolysis

Answer 10

Kinase which is involved in the transfer of a phosphate group, Isomerase which is involved in the catalyzation of of rearranging molecules, and dehydrogenase which is involved in the removal of a hydrogen proton from a substrate

Question 11

what are the cofactors used in gylcolysis

Answer 11

Mg2+ in most of the steps but in the last step Mg2+ and K

Question 12

EXTRA FOR MCAT** what are the differences in the delta g values and what do they mean

Answer 12

if the delta g value is negative that means that there is more energy on the product side, if the delta g value is positive then there is more energy on the reactant side

Question 13

what happens in glycolysis

Answer 13

a molecule of glucose gets broken down into two pyruvate molecules

Question 14

where does glycolysis occur

Answer 14

glycolysis occurs in the cytoplasm

Question 15

what is being oxidized and reduced in glycolysis

Answer 15

Nadh is being reduced and 1-3 biphosphoglycerate is being oxidized

Question 16

what is pyruvate oxidation

Answer 16

the molecules of pyruvate generated combine with CoA to produce acetyl coA

Question 17

what is being reduced and what is being oxidized during pyruvate oxidation

Answer 17

Nad is getting reduced and pyruvate is getting oxidized

Question 18

what is produced as a result of pyruvate oxidation

Answer 18

2 Nadh and 2 Co2 molecules

Question 19

how are two molecules of co2 produced

Answer 19

pyruvate undergoes decarboxylated

Question 20

what is decarboxylation

Answer 20

decarboxylation is the removal of a carboxyl group from a molecule to generate a molecule of co2

Question 21

where does pyruvate oxidation occur

Answer 21

in the mitochondria/inner membrane space

Question 22

what happens to the acetyl coA made during pyruvate oxidation

Answer 22

Acetyl CoA enters the Krebs cycle as a 2 carbon molecule and combines with the 4 carbon molecule oxaloacetate to create the 6 carbon molecule citrate. During this step another molecule of CoA-SH is released to go back to the inner memebrane space where pryuvate oxidation occur. Citrate then enters the citric acid cycle.

Question 23

where does Nadh find the get the h molecule to get reduced from during pyruvate oxidation

Answer 23

in order for acetyl coA to actually form, CoA which has a sulfur and hydrogen group attached to it need to combine with pryuvate; therefore the H group attached to coA is given to Nad to create NADH

Question 24

identify the products of the citric acid cycle

Answer 24

3 Nadh molecules, 2 co2 molecules, 1 fadh molecule, and 1 atp molecule but because the cycle turns twice, 6 Nadh molecule, 4 Co2 molecules, 2 Fadh2 molecules, and 2 Atp molecules

Question 25

how and why was there a production of 2 co2 molecules in the citric acid cycle

Answer 25

2 co2 molecules are produced with the help of the enzyme dehydrogenase which helps to catalyze the removal of a carbozyl group from an enzyme to produce co2. This co2 is used to regenerate oxaloacetate which will then pick up another acetyl coA enzyme to then start the cycle all over again

Question 26

how is atp made in the krebs cycle

Answer 26

atp is made with the help of succinyl coa synthetase which creates a gtp molecule out of gdp and pi which then breaks apart into gdp and pi and that pi combines with adp to form atp

Question 27

how many enzymes of dehydrogenase are in the krebs cycle

Answer 27

4

Question 28

how many times does oxidative decarboxylation occur

Answer 28

twice

Question 29

what happens to the NADHs generated throughout cellular respiration

Answer 29

they have been carrying electrons throughout the process and enter the inner mitochondrial matrix where NADH dehydrogenase catalyzes the removal of H and some electrons. Those electrons are given to complex 1 and so are the h protons from NADH. The h protons begin to get pumped into the intermembrane space where there are more H protons (up the concentration gradient- active transport). Then, the electron carrier ubiquinon comes and carries electrons from the first complex to the the third complex which is the known as the bc1 complex or coenzyme q. Electrons are then given to cytochrome c which then passes them to Cytomchrome oxidase where the electrons will flow out of the complex and meet up with 1/2 O2 + 2H and 2E to form water.

Question 30

What happens to the FADH2 from the krebs cycle

Answer 30

Because fadh2’s location was technically on the membrane, succinate help to link the citric acid cycle and the ETC, FADH2 gets oxidized and becomes FAD and its electrons get picked up by ubiquinon which then go to complex 3 and then to four.

Question 31

what happens to the H protons in the intermembrane space

Answer 31

they enter atp synthase to generate ATP molecules through the process of chemiosmosis

Question 32

define chemiosmosis

Answer 32

is the movement of ions across a semipermeable membrane, down their electrochemical gradient.

Question 33

what happens if there is no oxygen

Answer 33

in human, we enter lactic acid fermentation where NADH gets oxidized back to NAD and reused during glycolysis until oxygen is present again in which lactic acid will be converted to pyruvate again and the actual aerobic process will begin. In yeast, the same goes except pyruvate makes acetelaldehyde and that undergoes decarboxylation to make ethanol. The co2 released causes bread to rise. NADH gets oxidized and goes back into glycolysis. In humans, lactic acid has an alcohol group which can be toxic in large quantities.

Question 34

how many molecules of ATP are produced during cellular respiration

Answer 34

36