Lec 15: Energy Generation in Mitochondria and Chloroplasts

Question 1

Which of these represents the fate of a portion of the O2 produced by photosynthesis in chloroplasts?

Answer 1

It is consumed by oxidative phosphorylation in mitochondria

Question 2

What is true of the evolution of electron transport systems?

Answer 2

They are evolutionarily ancient, and likely provided energy for the earliest cells on earth

Question 3

The first living cells on earth are suspected to have generated ATP by what process?

Answer 3

Fermentation: organic molecules are broken down to generate energy without the involvement of oxygen. (Which didn’t enter the atmosphere in large amounts until about a billion years after photosynthetic cells evolved)

Question 4

Chemiosmotic coupling

Answer 4

How mitochondria, chloroplasts, and prokaryotes generate energy. It uses a membrane-based mechanism which involved using an electrochemical proton gradient to drive the synthesis of ATP.

Question 5

Where is the electron transport chain?

Answer 5

On the inner mitochondrial membrane

Question 6

Answer 6

Normally only small non-polar molecules can go through the lipid bilayer. In this case, the person would need to make more NADH (consuming more food) to generate the same amount of ATP).

Question 7

Products of cell respiration in mitochondria

Answer 7

Question 8

How NADH turns into NAD+

Answer 8

Question 9

Overview of the citric acid cycle/big picture, where it happens

Answer 9

Question 10

What are the different activated carriers used for?

Answer 10

NADH is mostly used for making ATP, the others are used more for catalyzing reactions

Question 11

Oxidative Phosphorylation

Answer 11

A chemiosmotic process that converts oxidation energy (loss of electrons from a molecule) into ATP

Question 12

In detail, what are the steps the hydrogen pumps?

Answer 12

Know:
- it’s on the inner mitochondrial membrane
- NADH dehydrogenase is the first
- ubiquinone carries the electron to cytochrome C reductase, so cytochrome C gets the electron
- the cytochrome C passes it to cytochrome c oxidase complex, which passes it to oxygen, to make water.

Question 13

What does it mean to be an electrochemical gradient?

Answer 13

Question 14

Answer 14

Pi: is the phosphate

First case: It would make ATP (the rhodopsin pumps H+ out, creating a gradient, which the ATP synthase needs to make ATP)

Second case: nothing happens, no gradient is created.

Question 15

How does ATP synthase physically work?

Answer 15

Hydrogen ions flow down a channel and cause ATP synthase to revolve, creating a mechanical motor. This causes the ATP synthase to make ATP. It could run in reverse if the ATP concentration is high, and the proton gradient is low.

Question 16

What steps generate the most ATP?

Answer 16

NADH from the citric acid cycle.

Question 17

How is the energy provided to pump H out of the cell, against the gradient?

Answer 17

Question 18

Overview of chloroplasts/photosynthesis

Answer 18

Question 19

Noncyclic photophosphorylation

Where do the energy, electrons, and reactants come from at each step?

What are the products of each reaction?

Answer 19

High energy electrons come from excitation from sunlight as opposed to from NADH

Question 20

Details of carbon fixation

Answer 20

3 CO2 means three carbons in
glyceraldehyde -phosphate means 3 carbons out

Question 21

What do mitochondria and chloroplasts have in common?

Answer 21

They both may have evolved from bacteria that were engulfed.

They both contain their own DNA, and can only synthesize a few proteins. They rely on the rest being transported in.

Question 22

Comparing the electron transport chain in chloroplasts and mitochondria

Answer 22

Question 23

In eukaryotes, which organelle performs oxidative phosphorylation?

Answer 23

mitochondria. oxidative phosphorylation means that it oxidizes something (NADH) and phosphorylates something else (ATP)

Question 24

Answer 24

Question 25

Answer 25

Question 26

How many ATP can be made from glucose under aerobic conditions? Anareobic?

Answer 26

Aerobic: 30
Anaerobic: 2

Question 27

Which activated carrier contains a high-energy bond whose hydrolysis releases a large amount of free energy?

Answer 27

ATP

Question 28

In mitochondria, what is the final electron acceptor in the electron-transport chain?

Answer 28

Oxygen (O2)

Question 29

What is true of NADH?

Answer 29

It has a weak affinity for electrons, and a negative redox potential

Question 30

Most of the energy for the synthesis of ATP comes from which molecules?

Answer 30

NADH produced by the citric acid cycle

Question 31

As the human population grows, it becomes increasingly important to maximize crop yields. Therefore, scientists are searching for more efficient ways for plants to convert CO2 into biomass. One approach is to genetically modify plant enzymes involved in photosynthesis to increase their efficiency. Which plant enzyme, responsible for carbon fixation, is a major focus of research?

Answer 31

Rubisco

Question 32

What represents the fate of a portion of the O2 produced by photosynthesis in chloroplasts?

Answer 32

It is consumed by oxidative phosphorylation in mitochondria

Question 33

What is true of the evolution of the electron-transport systems?

Answer 33

They are evolutionarily ancient, and likely provided energy for the earliest cells on Earth

Question 34

The first living cells on Earth are suspected to have generated ATP by what process?

Answer 34

fermentation

Question 35

In animal cells, how is most ATP produced?

Answer 35

mitochondria produce most of the ATP using energy derived from the oxidation of sugars and fatty acids

Question 36

Besides driving ATP synthesis, what does the proton gradient do?

Answer 36

it drives the active transport of selected metabolites into and out of the mitochondrial matrix

Question 37

antenna complex

Answer 37

in chloroplasts and photosynthetic bacteria, the part of the membrane-bound system that captures energy from sunlight; contains an array of proteins that bind hundreds of chlorophyll molecules and other photosensitive pigments

Question 38

Carbon fixation

Answer 38

Process by which green plants and other photosynthetic organisms incorporate carbon atoms from atmospheric carbon dioxide into sugars. This is the second stage of photosynthesis

Question 39

cell respiration

Answer 39

process by which cells harvest the energy stored in food molecules, usually accompanied by the uptake of O2 and the release of CO2

Question 40

chlorophyll

Answer 40

light-absorbing green pigment that plays a central part in photosynthesis

Question 41

cytochrome

Answer 41

a family of membrane-bound, colored, heme containing proteins that transfer electrons during cell respiration and photosynthesis

Question 42

cytochrome c oxidase

Answer 42

protein complex that serves as the final electron carrier in the respiratory chain; removes electrons from cytochrome c and passes them to O2 to produce H2O

Question 43

photosystem

Answer 43

large multiprotein complex containing chlorophyll that captures light energy and converts it into chemical-bond energy; consists of a set of antenna complexes and a reaction center

Question 44

quinone

Answer 44

small lipid-soluble mobile electron carrier that functions in the respiratory and photosynthetic electron-transport chains

Question 45

reaction center

Answer 45

in photosythetic membranes, a protein complex that contains a special pair of chlorophyll molecules. It performs the photochemical reactions that convert the energy of photons (light) into high-energy electrons for transport down the photosynthetic electron transport chain.

Question 46

redox pair

Answer 46

two molecules that can be interconverted by the gain or loss of an electron; for example NADH and NAD+

Question 47

redox potential

Answer 47

a measure of the tendency of a given redox pair to donate or accept electrons

Question 48

redox reaction

Answer 48

a reaction in which electrons are transferred from one chemical species to another. An oxidation-reduction reaction

Question 49

respiratory enzyme complex

Answer 49

set of proteins in the inner mitochondrial membrane that facilitates the transfer of high-energy electrons from NADH to oxygen while pumping protons into the intermembrane space

Question 50

stroma

Answer 50

in a chloroplast, the large interior space that contains the enzymes needed to incorporate CO2 into sugars during the carbon-fixation stage of photosynthesis; equivalent to the matrix of a mitochondrion

Question 51

thylakoid

Answer 51

in a chloroplast, the flattened disc-like sac whose membranes contain the proteins and pigments that convert light energy into chemical bond energy during photosynthesis

Question 52

photosystem II

Answer 52

note: comes first

It’s reaction center passes electrons to a mobile electron carrier called plastoquinone. It then transfers the high-energy electron to a proton pump called cytochrome b6-f complex. This is the only place where there is active proton pumping in the chloroplast electron-transport chain.

This proton gradient is used to make ATP.

Question 53

photosystem I

Answer 53

note: comes second

captures it’s high energy electron and gives it to ferredoxin, which brings the electrons to an enzyme that makes NADPH from NADP+

Question 54

where does the oxygen that is produced by photosynthesis come from?

Answer 54

Question 55

electron energy flow in photosynthesis

Answer 55

Question 56

stages of photosynthesis

Answer 56

stage 1: electron transport chain in the thylakoid membrane harnesses the energy of electron transport to pump protons into the thylakoid space. The high energy electrons are not donated to O2 at the end, they are donated to NADPH, which is then used for biosynthetic pathways.

stage 2: ATP and NADH produced by the photosynthetic electron-transfer reactions of stage 1 drive the manufacture of sugars from CO2. This happens in the chloroplast stroma. Results in glyceraldehyde 3-phosphate

Question 57

Where do the electrons in photosynthesis come from?

Answer 57

In photosystem II, when the mobile electron carrier plastoquinone removes an electron from a reaction center, it leaves behind a positively charged chlorophyll pair. Same thing when photosystem I gives an electron to ferredoxin.

In photosystem II, this electron comes from splitting water into O2, H+, and an electron.

In photosystem I, it comes from the end of photosystem II.