L10

Question 1

How are prokaryotic and Eukaryotic cells fuelled?

Answer 1

To fuel they need a carbon source, a means of capturing energy from chemical reactions or light to produce usable energy.

Question 2

What macromolecules require the most energy to be made most to least

Answer 2

Protein, RNA, phospholipid, DNA, lipopolysaccharide, murein, glycogen

Question 3

What are heterotrophs?

Answer 3

Cells that get their carbon source from organic sources

Question 4

What are autotrophs?

Answer 4

Cells that use carbon dioxide as a carbon source

Question 5

What are chemoheterotrophs?

Answer 5

Energy source and carbon source from organic sources. Consume organic building blocks that they are unable to make themselves. Most of their energy is from organic molecules such as sugars. Very common among eukaryotes.

Question 6

What are photoheterotrophs?

Answer 6

Capture light energy to convert to chemical energy in cells, get carbon from organic sources. Examples include non-sulphur bacteria, green non-sulphur bacteria.

Question 7

What are chemoautotrophs?

Answer 7

Break down inorganic molecules to supply energy for the cell. Use CO2 as carbon source. E.g. prokaryotes that break down H2S and ammonia. Live in extreme enviros

Question 8

What are photoautotrophs?

Answer 8

Capture light energy, use CO2 as carbon source. E.g. Cyanobacteria. Use similar compounds to those of plants to trap light energy.

Question 9

How is energy stored in cells?

Answer 9

ATP, energy carrying molecule used in cells as it can release energy very quickly

Question 10

How does ATP store energy?

Answer 10

Capacity to harvest, store, and use energy is a universal feature of all cells. Energy is conserved intracellulaeyky in the energy rich phosphate bond of ATP.

Question 11

How is ATP generated?

Answer 11

Through the addition of phosphate to ADP. When electrons are lost from a donor (oxidation) in a reaction involving chemical substrates (a) or light (b) the energy released is harvested to phosphorylate ADP and generate ATP. This is because electrons exist at different energy levels and movement from one energy level to a lower energy level releases energy

Question 12

What happens in oxidation phosphorylation (chemotrophs)?

Answer 12

Electron moves from a high energy level in a chemical molecule (electron donor) to a lower energy level in another molecule (electron acceptor)

Question 13

What happens in photophosphorylation (phototrophs)?

Answer 13

Light is used to excite photosynthetic pigments to move the electron to a higher energy state. This excited state is unstable, and the electron is transferred a lower energy level in another molecule (electron acceptor)

Question 14

What is reduction?

Answer 14

When a substrate gains electrons (positive charge reduced)

Question 15

What is oxidation?

Answer 15

When a substrate loses electrons

Question 16

What is reducing power?

Answer 16

The potential of a substance to reduce another substance, that can be either by loss or gain of electrons or by addition or removal of hydrogen

Question 17

How is hydrogen transferred?

Answer 17

Electrons in an organic redox reaction often are transferred in the form of a hydride ion - a proton and two electrons. Referred to as hydrogenation and dehydrogenation

Question 18

What is dehydrogenation?

Answer 18

When a substrate loses electrons and protons simultaneously and they are transferred to an H-acceptance molecule e.g. NAD

Question 19

How is reducing power used?

Answer 19

NADH+ can be oxidised to NAD+. By extracting the electrons (oxidising) of NADH+ and transporting these electrons sequentially through several membrane proteins (ETC). A proton gradient is generated across the cell membrane, which is used to generate energy.

Question 20

What is Gibbs free energy?

Answer 20

Amount of usable energy released or consumed in a reaction

Question 21

What is joules?

Answer 21

A measure or mechanical work that can be performed with that energy

Question 22

What is the equation for work (energy calculations)?

Answer 22

Work = mass x velocity/time x displacement

Question 23

What does it mean if delta G is positive?

Answer 23

If the reaction consumes energy (endergonic reaction) - formation of molecules is endergonic.

Question 24

What does it mean if delta G is negative?

Answer 24

If the reaction released energy, (exergonic reaction) - the breakdown of molecules is exergonic

Question 25

How much energy is needed to make reducing power?

Answer 25

Only those exergonic reactions that release at least 219 kj/mol can be used to generate reducing power (NADH+)

Question 26

What is reducing power used for?

Answer 26

The cell can use NADH+ to phosphorylate ADP and generate ATP. ADP to ATP, requires 31KJ ; about 7 ATPs can be generated with one NADH+

Question 27

What is a bomb calorimeter?

Answer 27

A lab instrument to measure the amount of a samples combustion heat or heat power when excess oxygen combustion occurs, used to work out the amount of energy stored in food by heating the food until it burns. The excess heat released by the reaction is directly proportional to the amount of energy contained in the food.

Question 28

How can ATP be generated?

Answer 28

Aerobic oxidation - oxidation of glucose and oxidation of fatty acids

Question 29

What is oxidation of glucose?

Answer 29

When glucose is metabolised to CO2 and H2O and ATP is generated. Contains 4 steps

Question 30

Oxidation of glucose - step 1 - glycolysis

Answer 30

Metabolic pathway that converts glucose into pyruvic acid. During glycolysis, one glucose is converted into two pyruvate. Early in the glycolytic pathway, 2 ATP molecules consumed. In the payoff phase energy is produced. 10 water soluble cytosolic enzymes catalyse the reactions of the glycolytic pathway.

Question 31

Oxidation of glucose - pyruvate oxidation and citric acid cycle - step 2

Answer 31

Pyruvate is transported from the cytosol across the mitochondrial membranes to the matrix. Pyruvate reacts with coenzyme A, forming CO2 and acetyl CoA. The acetyl of acetyl CoA is oxidised to CO2 via a set of 9 reactions, these reactions operate in a cycle that is called the citric acid cycle. For each acetyl group entering the cycle as acetyl CoA, two molecules of CO2 are produced. In prokaryotes pyruvate oxidation and the citric acid cycle occurs in the cytosol.

Question 32

What is generated in the citric acid cycle?

Answer 32

3 molecules of NADH, 1 ATP/GTP, 1 molecule of FADH2. Reaction 1 includes a two carbon acetyl residue from acetyl CoA condenses with the four carbon molecule oxaloacetate to form the 6 carbon molecule citrate.

Question 33

Oxidation of glucose - electron transport and PMF - step 3 where are eukaryotes and prokaryotes?

Answer 33

Eukaryotes localised in the internal membrane of the mitochondria and the chloroplasts. Prokaryotes electron transport chains are associated with the cell.

Question 34

Oxidation of glucose - electron transport and PMF - step 3 what happens?

Answer 34

Transporters in the inner mitochondrial membrane allow the uptake of electrons from cytosolic NADH. Most of the free energy released during the oxidation of glucose to CO2 is retained in the coenzymes NADH and FADH2 generated during glycolysis and the citric acid cycle.

Question 35

What happens in electron transport?

Answer 35

Cytosolic NADH+ and FADH2 generated during glycolysis and the citric cycle is oxidised to NAD+ and FAD+. Electrons are transferred from NADH+ AND FADH2 though a series of electron carriers in the inner membrane of the mitochondria (eukaryotes) or the plasma membrane (prokaryotes). Step by step transfer of electrons via the electron transport chain allows the free energy in NADH+ and FADH2 to be released in small increments and stored as the PMF.

Question 36

What is the PMF?

Answer 36

Occurs when the cell membrane becomes energised due to electron transport reactions by the electron carriers embedded in it. Protons are pumped at several sites during ET from NADH to O2. Protons from the mitochondrial matrix are pumped across the inner mitochondrial membrane of the plasma membrane creating a proton conc gradient across the membrane

Question 37

What is ATP synthase?

Answer 37

An enzyme complex that uses PMF to generate ATP from ADP (oxidative phosphorylation)

Question 38

Where is ATP synthase in prokaryotes, mitochondria, chloroplast?

Answer 38

Prokaryotes - plasma membrane Mitochondrion - inner membrane Chloroplast - thylakoid membrane

Question 39

What does ATP synthase consist of?

Answer 39

Membrane protein consisting of two subunits F0 and F1. Catalyses ATP synthesis on the cytosolic face of the membrane - ATP is always formed on the cytosol.

Question 40

What is F0 and F1 in ATP synthase?

Answer 40

F0 is Hydrophobic, embedded in the membrane. Has a cavity that takes in the protons - lower portion rotates in response to ions moving down the concentration gradient across the membrane. F1 is exposed to the cytosol, rotation of lower component of F0 activates F1 that binds and phosphorylate ADP into ATP H+ EXOPLASMIC greater than H+ CYTOSOLIC

Question 41

Oxidation of fatty acids - TAGs are hydrolysed - step 1

Answer 41

Fatty acids are stored as triacylglycerols (TAG), primarily as lipid droplets in eukaryotes or as free TAG in the cytoplasm of prokaryotic cells. Triacylglycerols (TAG) are hydrolysed in the cytosol to free fatty acids and glycerol

Question 42

Oxidation of fatty acids - formation of fatty acyl-CoA - step 2

Answer 42

Occurs in cytosol, fatty acid + HSCoA + ATP -> fatty acyl CoA + AMP + PPi

Question 43

Oxidation of fatty acids - transportation of fatty acyl-CoAs (carnitine transporter) - step 3

Answer 43

Fatty acyl-CoAs are transported into mitochondria and/or peroxisomes in eukaryotes, stay in the cytosol in prokaryotes

Question 44

Oxidation of fatty acids - oxidation of fatty acyl-CoAs - step 4

Answer 44

Fatty acyl-CoAs can be oxidised by a) mitochondrial oxidation or b) peroxisomal oxidation. Convert fatty acyl CoA molecule to acetyl CoA and a shorter fatty acyl CoA occurs in a sequence of four enzyme catalysed reactions.

Question 45

Oxidation of fatty acids - oxidation of fatty acyl-CoAs - step 4 - what happens in mitochondrial and peroxisomal oxidation

Answer 45

In both : one FAD molecule is reduced to FADH2, one NAD+ molecule is reduced to NADH. The cycle is repeated on the shortened fatty acyl CoA until this is completely converted to acetyl CoA. In mitochondria Acetyl-CoA enters the citric acid cycle. In peroxisomes oxidation of fatty acids yields no ATP.

Question 46

Oxidation of fatty acids - ETC and PMF - step 5

Answer 46

Electrons from FADH2 and NADH+ are used in the ETC generating the proton motive force and resulting in synthesis of additional ATP