2.8 And 8.2 Cellular Respiration

Question 1

What is cellular respiration and what chain and cyclic reactions does it involve and where do these reactions happen?

Answer 1

Cell respiration is the controlled release of energy from organic compounds to produce ATP.

1. Glycolysis.
2. Oxidation of pyruvate a.k.a. the link reaction is an intermediate reaction.
3. Krebs cycle or citric acid cycle.
4. Electron transport chain and chemiosmosis.

Question 2

What is the overall reaction for cellular respiration? Must be a chemical equation.

Answer 2

C6H12O6 + 6O2 —> 6CO2 + 6H2O + ATP

Question 3

What does aerobic cellular respiration require? How much ATP does it make? And what reactions does it involve?

Answer 3

It requires oxygen generates 36 ATP and involves all chain and cyclic reactions

Question 4

What reaction does anaerobic cellular respiration involve? How many ATP does it make?

Answer 4

Involves glycolysis plus an additional pathway that differs depending on the type of organism. Generates two ATP.

Question 5

List the types of respiration, the substrates, the final waste products per, the net ATP produced.

Answer 5

1. Aerobic- substrates are glucose and oxygen. Waste products are carbon dioxide and water. Net ATP is 36.
2. Anaerobic in animals and bacteria- substrate is glucose. Final waste product is lactic acid or lactate. Net ATP is two.
3. Anaerobic in yeasts- substrates are glucose. Finally products are ethanol and carbon dioxide. Net ATP is two.

Question 6

What are some applications of anaerobic respiration in yeasts and in humans

Answer 6

Yeasts produce ethanol, allowing for production of wines, beers and ciders. Also produces carbon dioxide, allowing for baked goods to rise.

Humans use anaerobic respiration when there isn’t enough oxygen, this produces lactic acid buildup

Question 7

What cellular processes require ATP and how does energy become available from it?

Answer 7

Adenosine triphosphate is needed for processes like active transport and proteins synthesis, as well as cell respiration. The ATP is made in the process of cell respiration. When ATP is hydrolyzed energy becomes available.
ATP —> ADP (adenosine diphosphate) + Pi (inorganic phosphate molecule).

When the inorganic phosphate is attached to another molecule, it is called phosphorylation (makes molecules, less stable and more likely to react), and it occurs during active transport where ATP forces the protein to undergo shape change. As well as tRNA enzymes that need it to activate.

Question 8

How are respirometer is used to calculate the rate of respiration

Answer 8

Organisms placed in a close chamber, will remove oxygen and add carbon dioxide. A strong alkali is used to remove carbon dioxide while the volume of air in the chamber decreases as oxygen is used. The constant temperature is maintained. Coloured water in a tube connected to the chamber, shows how water level changes as volume of air decreases. Allows us to calculate the volume of oxygen used in the rate of respiration when oxygen volumes are calculated at specific intervals.

Question 9

What are the ethical considerations when using invertebrates in respirometer experiments?

Answer 9

• Is research important enough to justify it
• Our other mechanisms are organisms possible
• Organisms cannot suffer pain or harm
• May require use of anaesthetics or painkillers to reduce pain and suffering
• No wild organisms can be used unless they can be returned to their natural habitat to continue their natural lives

Question 10

What two main processes does cellular respiration require? Hint: reaction requiring transfer of electrons.

Answer 10

Redox reactions, which are the enzyme control the transfer of electrons from one compound to another. Oxidation is losing electrons. Reduction is gaining electrons.

Question 11

Briefly describe what glycolysis is where it occurs what type of respiration it is the overall reaction and the end products

Answer 11

• sugar splitting
• Occurs in the cytoplasm
• Anaerobic
• (6-C) glucose + 2ATP —> 2(3-C) pyruvate + 4 ATP + 2NADH
• net gain of 2 ATP, 2 NADH, 2 pyruvate

Question 12

Cell respiration involves oxidation and reduction of electron carriers. Describe one electron carrier.

Answer 12

NAD = nicotinamide adenine dinucleotide is two nucleotides together, one adenine, one nicotinamide. It comes in the form of NAD+ as an electron acceptor, so it gets reduced. Except two electrons, and one proton to become NADH and carries electrons to the final step in cellular respiration.

Question 13

What happens following glycolysis if oxygen is not present

Answer 13

Pyruvate is converted in the cytoplasm to either
a) lactate or lactic acid
b) ethanol + CO2
No further yield of ATP

Question 14

Following glycolysis, what happens if oxygen is present

Answer 14

Pyruvate is transported to the mitochondrial matrix, and is broken down to generate a large yield of ATP

Question 15

How is the structure of a mitochondrion adapted to the function it performs

Answer 15

The mitochondrion is eucaryotic organelle where aerobic reactions of cellular respiration occur. It has a double membrane structure that provide compartments and services for maximum energy production.

Question 16

Describe the parts and functions of the mitochondria

Answer 16

1. Inner membrane- separates matrix from inter-membrane space what is the location for enzymes of electron transport chain
2. Outer membrane- separates mitochondrial contents from cytoplasm.
3. Cristae- provide large surface area for oxidative phosphorylation.
4. Matrix- contain enzymes for Krebs cycle.
5. Ribosomes- synthesis of mitochondria proteins.
6. Inter-membrane space- narrow space for the rapid build up of hydrogen ion concentration

Question 17

How is electron tomography used to produce images of mitochondria?

Answer 17

It generates 3-D images of active mitochondria, thick slices used multiple images, taken specimen, rotated, computer program builds 3-D image

Question 18

Describe the oxidation of pyruvate, or the link reaction, where it occurs, its overall reaction, products, and the general process

Answer 18

It occurs in the mitochondrial matrix and the overall reaction:
(3-C) pyruvate—> CO2 + NADH+ (2-C) acetyl co-A
Pyruvate is:
-oxidized and H+ and e- are removed and given to NAD+
- decarboxylated C is removed in the form of CO2
- attached to coenzyme A to make acetylene Co-A
Generates 1 NADH per pyruvate (2 per glucose)

Question 19

Describe the Krebs cycle, its main reactions, where it occurs and its products as well as its formulas

Answer 19

A.k.a. citric acid cycle occurs in mitochondrial matrix, and it begins and ends with the same molecule hence cycle. Overall reactions:
1. (2-C) Acetyl CoA + (4-C) oxaloacetate
—> (6-C) citrate
2. (6-C) citrate —> (4-C) oxaloacetate + 2CO2 + ATP + 3NADH + FADH2

Acetyl CoA and oxaloacetate combined form citrate, which breaks down back into oxaloacetate, or generating it to repeat the cycle. Citrate, and the next compound in the cycle or decarboxylated and oxidized and their electrons go to NADH and FADH2.
Products
-one ATP per Acetyl CoA (2 per glucose)
- 3 NADH per Acetyl coA (6 per glucose)
- 1 FADH2 per Acetyl CoA (2 per glucose)

Question 20

What is another example of an electron carrier and cell respiration?

Answer 20

FAD = flavin adenine dinucleotide
It is an electron acceptor and gets reduced. Except two electrons, and two protons to become FADH2. It carries electrons to the final step in cellular respiration.

Question 21

What is the electron transport chain? What is it made of and how does it work briefly?

Answer 21

There’s a collection of proteins in the inner mitochondrial membrane. Energy released by oxidation reactions is carried to the cristae of the mitochondria by reduced NAD and FAD. NADH and FADH2 in the mitochondrial matrix, transfer their electrons to proteins where the electrons are passed from one protein to the next in a chain series of redox reactions. The last electron acceptor in the chain is oxygen.

Question 22

How is the transfer of electrons between carriers in the ETC in the membrane of the cristae coupled to proton pumping?

Answer 22

Energy from passing electrons through the proteins is used to pump, hydrogen ions from matrix into inter-membrane. Space generating a proton gradient. The narrow inter-membrane space allows the concentration gradient to build quickly.

Question 23

What is the final electron acceptor and what is its role in the hydrogen gradient?

Answer 23

Oxygen
4e- + O2 + 4H+ —> 2 H2O
oxygen, combines with some of the hydrogen in the matrix to form water, further increasing the proton gradient between the matrix and the inter-membrane space.

Question 24

Describe the process of chemiosmosis and the differences between NADH and FADH2 at this stage

Answer 24

H+ flows back into the matrix through ATP synthase, which is an enzyme embedded in the membrane, and that makes ATP via oxidative phosphorylation (oxidative since oxygen is the final electron acceptor and producing ATP indirectly via redox reactions in the ETC)

3 ATP for ever NADH that drops off its electrons and 2 ATP for every FADH2. FADH2 skips the first protein in the chain so it makes less ATP than NADH.

Question 25

How did chemiosmotic theory lead to a paradigm shift?

Answer 25

Peter Mitchell published his explanation in 1961 for chemiosmosis, which was contrary to prevailing theory. His cannot be falsified and was excepted 17 years later when he won a Nobel prize.

Question 26

State the stage, location, ATP formed, ATP used, electron carriers produced, ATP formed per oxidized carrier, and total ATP formed after chemiosmosis per glucose molecule

Answer 26

Glycolysis: cytoplasm- 4 ATP- 2 ATP - 2 NADH - 3 ATP - 6 ATP total

Transport of NADH from glycolysis into mitochondria:
Outer membrane- 0 ATP - 2 ATP - 0 EC - 0 ATP - 0 ATP

Link rxn:
Matrix - 0 ATP - 0 ATP - 2 NADH - 3 ATP - 6 total ATP

Krebs: matrix - 2 ATP - 0 ATP - 6 NADH and 2 FADH2 - 3 per NADH and 2 per FADH2 - 22 ATP total

ETC: inner membrane - (all 0)

Chemiosmosis- intermembrane space - 34 ATP formed -0-0-0-0

ATP formed total= 40
ATP used = 4
Net ATP yield = 36