4.6 - Mitochondria and respiration

Question 1

role of mitochondria (2)

Answer 1

1. oxidative phosphorylation
2. heme biosynthesis

Question 2

endosymbiotic mitochondria origin theory (2)

Answer 2

1. ancestral eukaryote engulfed bacteria that utilises oxidative phosphorylation
2. symbiotic relationship provided energy required for eukaryotic and multicellular evolution

Question 3

oxygen (2)

Answer 3

1. critical for aerobic life
2. dangerous - free radicals damage proteins/nucleic acids (mitochondria 2x membrane keeps reactions seperate)

Question 4

mitochondria role in apoptosis

Answer 4

responsible for apoptosis, contents of mitochondria released into cytoplasm (very reactive and contains enzymes)

Question 5

step by step mitochondria origin theory

Answer 5

gradually over process of evolution more and more complicated structures within cell started to form organelles

Question 6

how is mitochondrial DNA inherited

Answer 6

only through maternal line (mitochondria in sperm do not enter the egg/destroyed if they do)

Question 7

role of mitochondrial DNA

Answer 7

codes for its own traits

Question 8

syndrome associated with mitochondrial DNA

Answer 8

kearns-sayre syndrome:
rare human disorder caused by decreased ability of cells to get energy from food

Question 9

similarities between mitochondria and bacteria (2)

Answer 9

1. use oxygen to break down food (aerobic bacteria) - same biochemical process
2. contain membrane proteins that are of bacterial origin (porins)

Question 10

porins

Answer 10

membrane proteins imbedded in outer mitochondrial membrane, involved in regulation of membrane permeability

Question 11

what do all mitochondrial genomes have

Answer 11

approximately the same 2% of bacterial genes

Question 12

what bacteria are chloroplasts most closely related to?

Answer 12

cyanobacteria

Question 13

mitochondrion division

Answer 13

mitochondrial fission (similar to binary fission)

Question 14

bacteria and mitochondria chromosomal similarity

Answer 14

both have their own circular chromosome with potential for multiple copies in one mitochondria

Question 15

evidence against step by step mitochondrial origin theory

Answer 15

no known species with transitional mitochondria/chloroplasts

Question 16

how can mitochondrial DNA be used in mapping migration of humans? (2)

Answer 16

1. mitochondria contain 37 genes only ever inherited down maternal line
2. fast mutation rate (10x faster than nuclear DNA)
   - helped provide evidence for “out of Africa” model of human evolution

Question 17

protein import into mitochondria

Answer 17

anything under 5kDa (small) can enter mitochondria via porin channels

Question 18

protein import into mitochondria (2)

Answer 18

1. nuclear encoded proteins must be unfolded to cross mitochondria double membrane
2. signal sequence on precursor protein recognised by sequence of receptors and transporters on both membranes (later cleaved off in matrix)
   - only a fraction of mitochondrial proteins made using mtDNA

Question 19

chaperone proteins

Answer 19

number of proteins that help with protein import into mitochondria (require some energy)

Question 20

where are mitochondria located? (2)

Answer 20

near sites of high ATP utilisation such as:
1. sperm tail
2. close to contractile apparatus in cardiac muscle

Question 21

why are mitochondria located near sites of high ATP utilisation?

Answer 21

enables supply of ATP by oxidative phosphorylation to energy hungry tissues

Question 22

stages of respiration (3)

Answer 22

1. glycolysis
2. citric acid cycle
3. electron transport chain

Question 23

glycolysis

Answer 23

occurs in cytosol (liquid component of cytoplasm): breakdown of glucose into pyruvate

Question 24

citric acid cycle

Answer 24

occurs in mitochondrial matrix: pyruvate further broken down producing electron carriers NADH, FADH2

Question 25

electron transport chain

Answer 25

occurs in inner mitochondrial membrane: uses electron carriers to produce ATP through oxidative phosphorylation

Question 26

how are electron transport mechanisms used in mitochondria and chloroplast (2)

Answer 26

1. mitochondria - proton gradient used to generate ATP from oxidative phosphorylation
2. chloroplast - energy from sunlight used to make ATP (via proton gradient)

Question 27

what % potential energy of glucose does oxidative phosphorylation allow to be converted into useful chemical energy (ATP)

Answer 27

50%

Question 28

oxidative phosphorylation

Answer 28

energy released by oxidation of NADH to NAD+ harnessed through energy conversion processes to drive the phosphorylation of ADP -> ATP
(smaller amount of ATP similarly generated from oxidation of FADH2 -> FAD)

Question 29

link reaction

Answer 29

pyruvate enters mitochondria and is converted to acetylCoA

Question 30

why do mitochondria have 4 separate compartments?

Answer 30

• each compartment contains a unique set of proteins:
  1. enabling it to fulfil its distinct function
  2. keeping reactions separate
  3. allowing generation of chemical gradients across membranes

Question 31

generation of ATP in mitochondria by chemiosmosis

Answer 31

protons ejected into inter-membrane space by electron transport chain establish proton gradient used to synthesise ATP via ATP synthase (imbedded in inner mitochondrial membrane)

Question 32

cristae

Answer 32

numerous infolds in inner membrane maximising surface area

Question 33

chemiosmosis

Answer 33

membrane bound mechanism of utilising both concentration gradient and electromotive force of pumping protons outside membrane to generate ATP

Question 34

proton gradient driven transport? (2)

Answer 34

1. pyruvate and Pi moved into matrix along with protons as the protons move down their electrochemical gradient
2. ADP pumped into matrix and ATP pumped out by antiport process - uses voltage gradient across membrane to drive the exchange
   - outer mitochondrial membrane freely permeable to components due to porins
   (proton flow across membrane also drives bacterial flagella rotation)

Question 35

ATP synthase (2)

Answer 35

1. acts like motor to convert energy of protons flowing down electrochemical gradient to chemical bound energy (ATP)
2. also capable of reverse reaction (hydrolysing ATP to ADP to pump protons against concentration gradient)

Question 36

evolution of ATP synthesis (3)

Answer 36

1. evolution of ATPase that pumped protons out of cell using energy of ATP hydrolysis (to reduce acidity)
2. evolution of a different proton pump (driven by electron transport chain)
3. linked 2 systems together to generate primitive ATP synthase (used protons pumped by electron transport chain to synthesise ATP)
   - early bacterium with final system had selective advantage

Question 37

deep sea archaea chemiosmosis

Answer 37

methanococcus:
use the H2 gas bubbles from deep sea vents as source of reducing power to generate energy via chemiosmotic coupling