Ch. 4: Cellular Respiration

Question 1

First law of thermodynamics

Answer 1

total amt. of energy in the universe remains constant –> energy is neither created nor destroyed, only converted to kinetic/ potential energy

Question 2

Second law of thermodynamics

Answer 2

some energy is “lost” (unable to do work) in the form of heat when energy changes state
entropy is constantly increasing

Question 3

Gibbs free energy/ Exergonic/ Endergonic

Answer 3

energy in a system that is available for conversions, change is ΔG
-ΔG means net loss of free energy (rxn gives off energy) and rxn is exergonic
+ΔG means net gain in free energy (energy added for rxn to occur) and rxn is endergonic –> most metabolic rxns

Question 4

Why can’t photosynthesis occur spontaneously?

Answer 4

it is an endergonic rxn so energy in amt. of at least ΔG must be provided (sunlight)

Question 5

Activation energy

Answer 5

energy needed for rxn to occur, reactants pass intermediate state. only if this energy is provided will an exergonic rxn occur spontaneously
catalyst speeds up chem. rxn by lowering activation energy

Question 6

How do metabolic rxns get their energy?

Answer 6

ATP is hydrolyzed to ADP

Question 7

2 processes that provide free energy (allow cells to maintain order, minimize entropy and remain alive)

Answer 7

Photosynthesis: energy from sun –> carbs
Respiration: extracting energy from those carbs

Question 8

Phosphorylation

Answer 8

adding energy and an inorganic phosphate to ADP to make ATP

Ex. substrate level, oxydative

Question 9

Substrate level phosphorylation

Answer 9

phosphate group and its energy transferred to ADP to form ATP. the substrate molecule donates high energy phosphate group
Ex. glycolysis

Question 10

Oxidative phosphorylation

Answer 10

process of producing ATP from NADH and FADH2 in ETC
phosphate group added to ADP to form ATP but energy of bond doesn’t come w/ phosphate. instead, e- give up energy to make ATP during ETC
last step in aerobic respiration

Question 11

Cellular respiration

Answer 11

ATP is generated from energy-rich glucose for energy

C6H12O6+6O2–>6CO2+6H20

Question 12

Aerobic respiration steps

Answer 12

happens when oxygen is available

1. Glycolysis
2. Krebs Cycle (Citric Acid Cycle)
3. Oxidative Phosphorylation

Question 13

Anaerobic respiration types

Answer 13

1. Alcohol fermentation

2. Lactic acid fermentation

Question 14

Glycolysis

Answer 14

decomposition of glucose to pyruvate

1. 2 ATP added
2. 2 NADH produced
3. 4 ATP produced by substrate level phosphorylation
4. 2 pyruvate formed
   summary: takes 1 glucose and turns it into 2 pyruvate, 2 NADH, and a net of 2 ATP (actually 4 ATP but use 2). occurs in cytosol

Question 15

NADH

Answer 15

coenzyme
energy rich molecule
e- carrier when NAD+ combines w/ 2 energy rich electrons and H+ (obtained from intermediate molecule during glucose breakdown)

Question 16

Krebs cycle

Answer 16

processing of pyruvate after glycolysis

1. In cytosol, pyruvate + CoA –> acetyl CoA; 1 NADH and 1 CO2 produced
2. Krebs Cycle: acetyl CoA + OAA (oxaloacetate) –> citrate; 7 intermediate products: 3 NADH and 1 FADH2, 1 ATP, 2 CO2 released (CO2 made in Krebs is what animals exhale)

Question 17

Electron Transport Chain (ETC)

Answer 17

part of oxidative phosphorylation
e- from NADH and FADH2 pass along ETC consisting of proteins that pass e- from one carrier to the next like cytochromes. along each step of chain, e- give up energy used to phosphorylate ADP to ATP (NADH 3 ATP, FADH2 2 ATP). last e- acceptor is oxygen which accepts 2 e- and combines w/ 2H+ to form water

Question 18

Cytochrome c

Answer 18

a carrier protein in the ETC which includes nonprotein parts like iron
present in lots organisms so this protein often compared among species to assess genetic relatedness

Question 19

Where does the Krebs Cycle and Oxidative Phosphorylation take place?

Answer 19

Mitochondria

Question 20

Outer membrane of Mitochondria

Answer 20

like plasma membrane, consists of double layer of phospholipids

Question 21

Intermembrane space of Mitochondria

Answer 21

narrow area between inner and outer membranes

H+ ions (protons) accumulate here

Question 22

Inner membrane of Mitochondria

Answer 22

double phospholipid bilayer w/ cristae
oxidative phosphorylation occurs here (ETC of protein complexes removes e- from NADH and FADH2 and transports H+ ions from matrix to intermembrane space)
ATP synthase found here: phosphorylation of ADP –> ATP

Question 23

Mitochondrial Matrix

Answer 23

fluid material that fills the area inside the inner membrane

Krebs Cycle and conversion of pyruvate to acetyl CoA occurs here

Question 24

Chemiosmosis (general)

Answer 24

mechanism of ATP generation that occurs when energy is stored in the form of a proton concentration gradient across a membrane

Question 25

Chemiosmosis in Mitochondria

Answer 25

1. Krebs Cycle produces NADH and FADH2 in the matrix (CO2 is made and substrate-level phosphorylation occurs to produce ATP)
2. Electrons are removed from NADH and FADH2 (e- move along ETC)
3. H+ ions are transported from the matrix to the intermembrane space
4. A pH and electrical gradient across the inner membrane is created (potential energy reserve)
5. ATP synthase generates ATP (protons move in direction of their concentration gradient, and ATP synthase turns ADP into ATP)

Question 26

Theoretical vs. Actual amount of ATP created by aerobic respiration

Answer 26

36 theoretical, actual around 30

Question 27

Anaerobic Respiration

Answer 27

goal is to replenish NAD+ so glycolysis can happen; occurs in cytosol alongside glycolysis
if oxygen not present, no e- acceptor exists to accept at end of ETC… NADH accumulates bc NAD+ –> NADH but Krebs and glycolysis both stop bc need NAD+ to accept e- so no ATP produced … DEATH
ex. alcoholic fermentation and lactic acid fermentation

Question 28

Alcohol Fermentation

Answer 28

goal to replenish NAD+ for glycolysis
occurs in plants, fungi (yeast) and bacteria
Pyruvate –> acetylaldehyde –> ethanol
for each pyruvate, 1 CO2 (carbonation in beer) and 1 acetylaldehyde are produced; for each acetylaldehyde, 1 ethanol (alcohol in beer) and 1 NAD+ are made using energy from NADH
result: 2 ATP from glycolysis

Question 29

Lactic Acid Fermentation

Answer 29

pyruvate –> lactate (lactic acid)
in this process, NADH gives up its e- to form NAD+ which can now be used in glycolisis
most lactate is transported to liver, where it is converted back to glucose when more ATP is available