Lectures 15&16 - Mitochondria and Chloroplasts

Question 1

What does the folding give the mitochondria

Answer 1

High SA

Question 2

What are the parts of a mitochondria

Answer 2

Matrix
Cristae
Inner Membrane
IMS
Outer membrane

Question 3

What are the parts of a chloroplast

Answer 3

Outer membrane
Inner Membrane
Thylakoid membranes (contains lumen)
Granum (stacks of thylakoids)
IMS
Stroma (space between inner and thylakoid membranes)

Question 4

What is the main function of mitochondria and chloroplasts

Answer 4

ATP synthesis

Question 5

What is the function of ATP produced in the mitochondria

Answer 5

Energy source for other cellular processes as a result of oxidation of foodstuffs

Question 6

What is the function of ATP produced in the chloroplasts

Answer 6

Used in Calvin cycle in the fixation of CO2 into sugar

Question 7

What is ATP used for

Answer 7

Anabolic reactions of cells responsible for growth and repair processes
Catabolic reactions release energy needed to drive anabolic reactions
Must be an efficient linking or coupling of energy yielding to energy requiring processes
ATP is most commonly used as this energy intermediate
Energy currency of the cell
Transfers the energy captured during cellular respiration to the cellular sites that use energy

Question 8

Where is ATP synthase found

Answer 8

mitochondrial inner membrane, the chloroplast thylakoid membrane and the inner membrane of eubacteria

Question 9

Describe the structure and function of ATP synthase

Answer 9

Large lollipop head is attached through a stalk to the transmembrane carrier for protons
As protons pass through the carrier it is thought that the stalk spins inducing the head to produce ATP

(F0 portion allows protons to flow through, turning stalk - F1 subunit then converts ADP +Pi to ATP)
(slide 9)

Question 10

A proton gradient is a form of stored energy. What are its two components

Answer 10

Difference in voltage across a membrane (membrane potential
Difference in proton concentration

Question 11

What is the maths behind ATP synthase

Answer 11

Can produce around 100 molecules of ATP/second
Around 3 protons are needed to synthesise 1 molecule of ATP
Can be reversed, ie use the hydrolysis of ATP to pump protons

Question 12

Conformational changes in ATP synthase

Answer 12

Slide 12

Question 13

Where is the ATP synthesised in the chloroplasts

Answer 13

Stroma

Question 14

Where is the ATP synthesised in Mitochondria

Answer 14

Matrix

Question 15

How is the proton gradient across the mitochondrial membrane generated

Answer 15

ETC
High energy electrons are passed along an electron transport chain
These electron transfers release large amounts of energy which is used to pump H+ across the membrane creating an electrochemical proton gradient

Question 16

Describe the structure of the proton pumping completes in the mitochondria

Answer 16

NADH dehydrogenase
Cytochrome bc1 complex
Cytochrome oxidase complex

Fats and Carbohydrates enter citric acid cycle, losing 2e-

2e- create an ETC with NADH donating protons, through the 3 complexes then H+ binds with oxygen to form water

Question 17

What does NAD stand for

Answer 17

Nicotinamide adenine Dinucleotide

Question 18

What are some mobile electron carriers and their functions

Answer 18

Move electrons between respiratory chain complexes

Ubiquinone carries electrons from the NADH dehydrogenase to the cytochrome b-c1 complex
Cytochrome c carries electrons from the cytochrome b-c1 complex to the cytochrome oxidase complex

Question 19

What is chemiosmotic coupling

Answer 19

The linkage of electron transport, proton pumping and ATP synthesis
In mitochondria this process is known as oxidative phosphorylation

Question 20

How are reducing agents ranked

Answer 20

Reducing agents ranked according to electron transfer potential
NADH has high electron transfer potential (-ve value)
H2O has low electron transfer potential (+ve value)

Standard redox potential E’0 (measured in Volts)
DG0’ = -nFDE’0

G (Free energy)
E (Redox potential
N+= no of electrons
F= Faraday constant

Question 21

What happens to the redox potential (electron affinity) along the mitochondrial electron transport chain

Answer 21

Increases

Question 22

What are the metal sensors in electron carrying groups

Answer 22

NADH dehydrogenase: Flavin nucleotides, Fe-S

Cytochrome bc1 complex: Heme, Fe-S

Cytochrome c: Heme

Cytochrome oxidase complex: Heme, CuA, CuB