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BB10005 COPY > Mitochondria and chloroplasts > Flashcards

Mitochondria and chloroplasts Flashcards

1
Q

What are some of the key structural features of a mitochondrion?

A
  1. Two membranes- inner and outer
  2. Outer membrane has large porin like molecules and TOM complexes
  3. The inner membrane is highly folded to create a high surface area contains the electron transport chain and ATP synthase
  4. the intracellular space is called the matrix and contains enzymes of citric acid cycle
  5. folds are called cristae.
  6. Low proton concentration in matrix compared to inner membrane
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2
Q

What are some of the key structures of chloroplasts?

A
  1. Outer and inner membrane with intermembrane space in between.
  2. The stroma is the intracellular fluid
  3. a granum is a stack of thylakoids- Photosynthetic pigments and ATP synthase in thylakoid
  4. Proton gradient across thylakoid membrane so protons pumped into thylakoid membrane
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3
Q

What is the primary function of both mitochrondria and chloroplasts?

A

Synthesising ATP.

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4
Q

What do catabolic reactions do in cells?

A

Release energy that is needed to drive anabolic reactions.

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5
Q

What are anabolic reactions of cells important for in cells?

A

Growth and repair processes.

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6
Q

What is ATP made up of?

A

Three phosphate groups, ribose and adenine.

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7
Q

How do cells obtain most of their energy?

A
  1. Cells obtain most of energy from membrane bound mechanisms
  2. ATP synthase is found in the mitochondrial inner membrane, the chloroplast thylakoid membrane and the inner membrane of eubacteria
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8
Q

What is ATP synthase and how does it work?

A
  1. It is a membrane protein complex that uses the stored energy of a proton gradient across a membrane to produce ATP from ADP and Pi.
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9
Q

What is F-type ATPase made up of?

A
  1. An F0 which is integral and an F1 which is peripheral.
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10
Q

What is ATPase?

A
  1. An enzyme that catalyses the formation of ATP from ADP and Pi.
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11
Q

What is the structure of ATP synthase?

A
  1. Large lollipop head is attached through a stalk to the transmembrane carrier for protons
  2. As protons pass through the carrier it is thought that the stalk spins inducing the head to produce ATP
  3. The F0 part of the ATP synthase is embedded in the membrane.
  4. The F1 part is peripherally associated with the membrane.
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12
Q

Which part of the structure is F1 and which is F0?

A

F1 is the lollipop head and F0 is the stalk embedded.

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13
Q

What is the basic mechanism in which ATP is produced from ATP synthase?

A
  1. As protons pass through the carrier, the stalk spins which induces the head to produce ATP.
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14
Q

How is energy created from protons moving through the ATP synthase?

A
  1. As protons pass through the F0 portion from one side of the membrane to the other a stalk rotates.
  2. This causes conformational changes in F1 that facilitate the production of ATP.
  3. Energy is converted from one form to another.
  4. A proton gradient is stored energy: As protons flow across the membrane the stored energy is converted to mechanical energy (movement of the stalk).
  5. The movement of the stalk is used to mechanically deform (conformational energy) the F1 subunits.
  6. This conformational energy is then converted into chemical bond energy (ADP+P converted to ATP).
  7. Gamma subunit is in the centre and is asymmetrical so as it rotates it causes conformation changes in different subunits
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15
Q

What is the stored energy, in the form of a proton gradient, made up of?

A
  1. Difference in voltage across the membrane (the membrane potential)
  2. the difference in proton concentration (remember pH is a measure of proton concentration).
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16
Q

How many molecules of ATP can ATP synthase produce a second?

A

100.

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17
Q

How many protons are needed to synthesise one molecule of ATP?

A

3.

18
Q

Where is ATP synthase found in the mitochrondria?

A

The inner membrane/ plasma membrane

19
Q

Where is ATP synthase found in chloroplasts?

A

In the thylakoid membrane.

20
Q

Where is ATP synthesised in the mitochrondria?

A

The matrix/cytoplasm.

21
Q

WHere is ATP synthesised in the chloroplast?

A

THe stroma.

22
Q

Where is ATP synthase found in bacteria

A

Sits in inner membrane of bacteria

23
Q

WHere is ATP synthesised in bacteria?

A
  1. Cytoplasm
24
Q

How is the proton gradient across the mitochondrial membrane generated

A
  1. High energy electrons are passed along an electron transport chain – picks up protons and then releases it further down into
  2. These electron transfers release large amounts of energy which is used to pump H+ across the membrane creating an electrochemical proton gradient
  3. An electron can bind and release a proton at each step in the chain
  4. B picks up a proton when it accepts an electron from A and releases it on the other side of the membrane when the electron is passed on to C
  5. Proton binds and there is a conformational change and when electron is passed on the proton loses affinity for protein
25
Q

Where do the electrons for the electron transport chain in mitochondria come from

A
  1. Oxidation of food molecules in citric acid cycle
  2. NAD+ is reduced to NADH at same time- Passes on its electrons to membrane components of electron transport chain
  3. Electrons transfers coupled to proton pumping
26
Q

What are the names of the membrane components of the electron transport chain

A
  1. NADH dehydrogenase
  2. cytochrome b-c1
  3. cytochrome oxidase complex
27
Q

Describe what the mobile electron carriers do

A
  1. Ubiquinone carries electrons from the NADH dehydrogenase to the cytochrome b-c1 complex
  2. Cytochrome c carries electrons from the cytochrome b-c1 complex to the cytochrome oxidase complex
  3. Electrons transferred to oxygen in cytochrome oxidase and form water
  4. Proton pumping is coupled with these electron transport
28
Q

What is the chemiosmotic coupling in mitochondria

A
  1. The linkage of electron transport, proton pumping and ATP synthesis
  2. In mitochondria this process is known as oxidative phosphorylation
29
Q

How do electrons move along the electron transport chain

A
  1. By a series of oxidation, reduction reactions

2. As one reactant is oxidised (loses electrons) another is reduced (gains electrons)

30
Q

Describe how the electron transfer potential changes as you go along the electron transport chain

A
  1. Reducing agents ranked according to electron transfer potential
  2. NADH has high electron transfer potential (-ve value)
  3. H2O has low electron transfer potential (+ve value)
  4. As you go along electron transport chain- have higher and higher affinity for electrons so electrons move along
31
Q

What is the equation for free energy change as an electron moves

A
  1. Standard redox potential E’0 (measured in Volts)

2. DG0’ = -nFDE’0

32
Q

Name the four electron carrying groups and their cofactors

A
  1. NADH dehydrogenase: Flavin nucleotides, Fe-S
  2. Cytochrome bc1 complex: Heme, Fe-S
  3. Cytochrome c: Heme
  4. Cytochrome oxidase complex: Heme, CuA, CuB
33
Q

Describe what the input and output for the citric acid cycle is

A
  1. 2 carbons in (acetyl CoA)
  2. 2 carbons released (as CO2)
  3. Each turn of the cycle produces 3 NADH, 1 GTP and 1 FADH2
34
Q

What is found in the matrix of the mitochondria

A
  1. Enzymes of citric acid cycle

2. mitochondrial DNA

35
Q

What is found in the inner membrane of the mitochondria

A
  1. Electron transfer proteins
  2. ATP synthase
  3. Transport proteins.
36
Q

What is found in the outer membrane of the mitochondria

A
  1. Has large pores
  2. lipid synthesis
  3. conversion of lipid substrates into forms that can be metabolised in the matrix
37
Q

What is found in the intermembrane space

A
  1. Several enzymes that use ATP passing out of the matrix to phosphorylate other nucleotides
38
Q

How much ATP is generated in the complete glucose oxidation

A

1.30 ATP generated in complete glucose oxidation

39
Q

Why is some ATP lost

A
  1. NADH generated in glycolysis cannot feed electrons directly into the ETC.
  2. Transporting these NADH into mitochondria requires energy so the net ATP yield is lower from these NADH molecules.
40
Q

Give a summary of glucose oxidation

A
  1. In the complete oxidation of glucose the majority of the ATP is generated by ATP-synthase.
  2. The exceptions are the 2 ATP from glycolysis and the 2 GTP (GTP and ATP are equivalent in terms of having high energy phosphate bonds) from citric acid cycle.
  3. NADH and FADH2 feed high energy electrons into electron transport chain (ETC).
  4. The energy from the electrons is used to pump protons generating the proton gradient.
  5. Proton gradient powers the ATP synthase.

BB10005 COPY (23 decks)

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