Biology - Chapter 4 Cellular Respiration

general cellular respiration equation

C₆H₁₂O₆ + O₂ → 6CO₂ + 6H₂O + ENERGY

3 overall goals in cellular respiration

• break bonds between 6 carbon atoms of glucose

• moves electrons from hydrogen atoms to oxygen

• traps as much of the free energy released as possible, in the 2 processes above in the form of ATP

what happens to the 6 carbon atoms in glucose when the bonds are broken in cellular respiration?

they are released as CO₂

what causes electrons to move from hydrogen atoms to oxygen?

because oxygen is the second most electronegative element on the periodic table

what happens when electrons are moved from hydrogen atoms to oxygen?

the hydrogen ions and oxygen then react and form the 6 water molecules

where does cellular respiration take place?

partly in the cytosol and mostly in the mitochondria

how many stages does cellular respiration occur in?

4

list the stages of cellular respiration

1. glycolysis

2. pyruvate oxidation

3. the Krebs cycle

4. electron transport and chemoismosis

how many steps does glycolysis have?

10

how many steps does pyruvate oxidation have?

1

how many steps does the Krebs cycle have?

8

how many steps does electron transport and chemiosmosis have?

it’s a multi-step process (not specified)

where does glycolysis take place in the mitochondria?

the cytoplasm/cytosol

where does pyruvate oxidation take place in the mitochondria?

the mitochondrial matrix

where does the Krebs cycle take place in the mitochondria?

the mitochondrial matrix

where does electron transport and chemiosmosis take place in the mitochondria?

the inner mitochondrial membrane

what do energy carriers do?

they carry or ‘shuttle’ high energy electrons

common energy carriers

• NAD⁺

• NADP⁺

• FAD

• NAD⁺+ 2 e^- ↔ NADH + H⁺

• NADP⁺+ 2 e^- ↔ NADPH + H⁺

• FAD + 2 e^- ↔ FADH₂
  

left to right:

right to left:

left to right: reduction

right to left: oxidation

glycolysis

the most fundamental of all the metabolic pathways

in which organisms does glycolysis occur?

occurs, in some form, in the cells of all organisms - eukaryotes and prokaryotes

can glycolysis occur in bacteria?

yes because glycolysis takes place in the cytoplasm, not the mitochondria

does glycolysis need oxygen

no

glycolysis word equation

glucose (6-C sugar) + 2 ATP → 2 Pyruvate (each 3-C sugar) + 4 ATP + 2 NADH

a molecule of glucose requires __ ATP to break up into __ 3-C pyruvate molecules

2, 2

glycolysis yields __ ATP and __ NADH

4, 2

what is the ATP net gain in glycolysis

2 ATP’s

• it requires 2 and yields 4, therefore the net gain is 2 ATP

what does glycolysis pass onto stage 2 of cellular respiration?

2 pyruvate molecules, 2 ATP, and 2 NADH carriers

after glycolysis

the 2 pyruvate molecules move through the cytosol/cytoplasm of the cells into the mitochondria

what pyruvate needs to help it pass through the mitochondrial matrix

a transport protein

first step of pyruvate oxidation

a carbon dioxide molecule is removed from pyruvate in a process called decarboxylation

second step of pyruvate oxidation

the decarboxylated pyruvate is then oxidized (loses electrons). the NAD⁺ is reduced (gains electrons) to form NADH + H⁺

third step of pyruvate oxidation

the decarboxylated, oxidized molecule then moves on to bind with coenzyme A (CoA) to form Acetyl CoA.

pyruvate oxidation equation

Pyruvate + NAD⁺+ CoA → Acetyl CoA + NADH + CO₂ + H⁺

what happens in pyruvate oxidation is ______ because there are __ pyruvates coming from glycolysis

doubled, 2

decarboxylation

a process in which a carbon dioxide molecule is removed from pyruvate (also the first step of pyruvate oxidation)

what happens in step 2 of pyruvate oxidation?

the decarboxylated pyruvate is then oxidized (loses electrons). the NAD⁺ is reduced (gains electrons) to form NADH + H⁺

how is Acetyl CoA formed? (also step 3 of pyruvate oxidation)

the decarboxylated, oxidized molecule then moves onto bind with coenzyme A (CoA) to form Acetyl CoA

overall pyruvate oxidation equation

Pyruvate + NAD⁺ + CoA → Acetyl CoA + NADH + CO₂ + H⁺

inventory after stage 1 (glycolysis) and stage 2 (pyruvate oxidation)

• 2 Acetyl CoA (from pyruvate oxidation)

• 4 NADH (2 from glycolysis and 2 from pyruvate oxidation)

• 2 ATP (from glycolysis)

who discovered the Krebs’ cycle?

Sir Hans Krebs at the University of Sheffield, 1937

what does the Krebs’ cycle begin and end with?

a 4 carbon compound called oxaloacetate

what forms from the combination of the 2-carbon acetyl group from the acetyl CoA and the oxaloacetate?

citrate

what is released as a waste product in the Krebs cycle?

CO₂

what energy carriers are produced in the Krebs cycle?

NADH and FADH₂

the Krebs cycle turns _____ for every original glucose molecule

twice. (because for every glucose molecule, there are 2 Acetyl-CoA

by the end of the Krebs cycle

the original glucose molecule is all used up (the carbons and oxygens are released as CO₂ and the Hydrogens are in the energy carriers

inventory of molecules after the Krebs cycle

• 4 ATP total

  • 2 from glycolysis

  • 2 from Krebs cycle

• 10 NADH total

  • 2 from glycolysis

  • 2 from pyruvate oxidation

  • 6 from Krebs cycle

• 2 FADH₂ total

  • from Krebs cycle

how many energy carriers from stages 1-3?

12

which is better - a fast or slow release of energy?

slow because it is more efficient. a fast release of energy is mostly lost as heat

where does the electron transport chain occur

inner mitochondrial matrix

what is the final electron acceptor

oxygen

the transfer of electrons from the energy carriers to oxygen forces ______ into the ________________

H⁺ ions, intermembrane space

what happens when the H⁺ ions build up?

they will be forced into the matrix

what forces H⁺ ions into the matrix?

by a special enzyme called ATP synthase

the action of H⁺ ions passing through ATP synthase drives the production of ___

ATP

the ETC is made up of __ __________

4 complexes

complex I consists of

NADH dehydrogenase

complex II consists of

succinate dehydrogenase

complex III consists of

cytochrome complex

complex IV consists of

cytochrome oxidase

as the energy carriers are _________, the lost _______ are shuttled along the chain. at the same time, ________ (protons) are pumped into the ______________ _______

oxidised, electrons, H⁺ ions, intermembrane space

after the H⁺ ions are pumped into the intermembrane space, there is now a _____ concentration of H⁺ ions in the intermembrane space compared to the ______

high, matix

what causes H⁺ ions get through the membrane?

ATP synthase

as the protons pass through the ATP synthase, the energy from the proton concentration gradient _________ ___

synthesizes ATP

the driving force behind ETC is

oxygen because it is extremely electronegative and pulls electrons towards itself

_________ is the final electron acceptor

oxygen

why do living organisms require oxygen

so that it can be transported to every mitochondria in every cell in our body to act as the final electron acceptor and pull electrons along the ETC. the oxygen bonds with the hydrogen to form water, which we breathe out

the energy from H⁺ flow can be lost due to

uncoupling proteins

eg. in hibernating animals, the ETC and ATP synthesis can be ‘uncoupled’.

this means that the energy released during ETC as not converted into ATP but instead is released as thermal energy

how efficient is aerobic respiration at extracting energy from glucose

the theoretical yield of energy gained from one molecule of glucose is 39%.

*the other 60% is lost as heat

a constant supply of ATP is important for all cells but difficult in certain types of cells where there are…

periods of both intense activity and inactivity (such as the brain and muscle cells)

creatine phosphate

a high energy molecule

creatine + ATP →

creatine phosphate + ADP

creatine phosphate + ADP →

creatine + ATP

do all organisms require a constant supply of oxygen?

no, there are some exceptions that can survive in an oxygen free environment

how many general anaerobic processes

2

name the 2 general anaerobic processes

fermentation and anaerobic respiration

alcohol fermentation

carried out by yeast

fermentation uses ___________________ as the final electron acceptor

an organic molecule

does fermentation uses the ETC

no it does not use the ETC

anaerobic respiration

• many prokaryotes have a type of cellular respiration electron transport chain on internal membranes derived from their plasma membrane

  • even though they do not have mitochondria

  • where oxygen is not available (deep underground or in marsh sediments), they use other, inorganic electron acceptors such as SO₄^2—, NO₃^—, and Fe³⁺

can fats and proteins enter the cellular respiration pathway at all?

yes, during certain points

what enters the cellular respiration pathway during glycolysis?

carbs, some amino acids, glycerol

what enters the cellular respiration pathway during pyruvate oxidation?

some amino acids

what enters the cellular respiration pathway during the citric acid cycle?

fatty acids, some amino acids

what enters the cellular respiration pathway during oxidative phosphorylation?

nothing