Respiration💥

Question 1

What is respiration?

Answer 1

The process by which the energy in food molecules is made available for an organism to do biological work - make ATP

Question 2

What is ATP?

Answer 2

• Form of chemical energy that is used to fuel endergonic biological activities
• Universal energy source
• Covalent bond between last phosphate is unstable, so is removed during an exergonic hydrolysis reaction

Question 3

What is energy needed for?

Answer 3

• Active transport
• Endocytosis/exocytosis
• Cell division
• DNA replication
• Synthesis of large molecules
• Movement (e.g. cilia)

Question 4

Structure of ATP

Answer 4

• 3 phosphate groups held together by covalent bonds
• Ribose sugar
• Adenine nitrogenous base
• Phosphorylated nucleotide

Question 5

Steps of glycolysis (simple)

Answer 5

• 6C glucose
• 6C glucose diphosphate
• 2x 3C triose phosphate (glyceraldehyde 3-phosphate)
• 2x 3C pyruvate

Question 6

Glycolysis (detailed)

Answer 6

•6C glucose:
-Phosphorylation reaction
-2ATP->2ADP
•6C glucose-diphosphate:
-More polar (less chance to diffuse out of the cell)
-More unstable (less activation energy needed for enzymes)
-Splits…
•x2 3C TP (glyceraldehyde 3-phosphate):
-Dehydrogenation reaction (exergonic) removes 2H (from each) which reduce NAD (carrier)
-Energy released from dehydrogenation is used to synthesise 2 ATP molecules (from each) by substrate-level phosphorylation
•x2 3C pyruvate

Question 7

How much ATP is used in glycolysis?

Answer 7

2 ATP

Question 8

How many ATP molecules are gained during glycolysis?

Answer 8

4 ATP

Question 9

What is the net gain of ATP from glycolysis?

Answer 9

2 ATP

Question 10

How many NAD carriers are reduced during glycolysis?

Answer 10

2 NADred

Question 11

Where does glycolysis occur?

Answer 11

Cytoplasm

Question 12

Does glycolysis require oxygen?

Answer 12

No

Question 13

What is NAD?

Answer 13

A coenzyme that acts as a hydrogen carrier

Question 14

What is a dehydrogenation reaction?

Answer 14

• Involves removal of pairs of hydrogen atoms from a molecule
• Catalysed by a dehydrogenase enzyme

Question 15

What is substrate-level phosphorylation?

Answer 15

Synthesis of ATP using energy released from the breakdown of a high-energy substrate molecule

Question 16

What is phosphorylation?

Answer 16

The addition of a phosphate group (Pi)

Question 17

Why is NAD regarded as a coenzyme?

Answer 17

It assists dehydrogenases

Question 18

Link reaction (simple)

Answer 18

• x2 pyruvate (3C)

* Acetyl-CoA (2C)

Question 19

Link reaction detailed

Answer 19

• Pyruvate enters mitochondrial matrix by active transport
• Oxidative decarboxylation
• Dehydrogenation reduces NAD
• Forms acetate
• Acetate combines with coenzyme-A to form acetyl coenzyme-A

Question 20

Where does the link reaction occur?

Answer 20

Mitochondrial matrix - pyruvate is transported by protein

Question 21

Where does the Krebs cycle occur?

Answer 21

Mitochondrial matrix

-Requires O2

Question 22

What is the Krebs cycle?

Answer 22

• Involves a series of decarboxylation and dehydrogenation reaction
• CO2, ATP, NADred, FADred
• 2 cycles per glucose molecule

Question 23

How can the Krebs cycle be continuous?

Answer 23

• Carriers are regenerated

* If more acetyl-CoA is available, the cycle can start again

Question 24

Krebs cycle process (simple)

Answer 24

•4C + 2C (acetyl-CoA)
-CoA is removed
•6C
-dehydrogenation removes 2H (NADred)
-decarboxylation 
•5C
-decarboxylation of CO2
-substrate-level phosphorylation of ATP
-dehydrogenation removes 2H (NADred)
•4C
-dehydrogenation removes 2H (FADred)
•4C
-dehydrogenation removes 2H (NADred)
•4C (oxaloacetate)

Question 25

How much NADred is produced from the Krebs cycle per one glucose molecule?

Answer 25

6 NADred | These go on to form 18 ATPs

Question 26

How much FADred is produced from the Krebs cycle per one glucose molecule?

Answer 26

2 FADred | These go on to form 4 ATPs

Question 27

How much ATP is directly made from the Krebs cycle per one glucose molecule?

Answer 27

2 ATPs

Question 28

How much CO2 is produced from the Krebs cycle per one glucose molecule?

Answer 28

4 CO2

Question 29

What is the main purpose of the Krebs cycle?

Answer 29

* To feed electrons into the next stage of aerobic respiration * Electrons come from reduced NAD and FAD molecules which carry hydrogen atoms

Question 30

What are cytochromes?

Answer 30

* Iron-containing pigmented molecules * Embedded in inner membranes of mitochondria where they form an ETS * Each redox reaction in the ETS releases energy which can be used to synthesise ATP

Question 31

What is oxidative phosphorylation?

Answer 31

Oxygen dependent synthesis of ATP within mitochondria using energy released from redox reactions

Question 32

What is chemiosmosis?

Answer 32

* Energy from electrons during redox reactions is used to pump H+ protons from the matrix into the inter-membrane space * H+ accumulate so that steep conc & electrochemical gradient are established across the inner membrane * H+ diffuse back into matrix via stalked particles which consists of a chemiosmotic channel protein attached to ATPsynthase * Flow of protons through ATPsythase provides energy to produce ATP from ADP and Pi

Question 33

Why are stalked particles required for chemiosmosis?

Answer 33

* Inner membrane is impermeable to protons | * Has ATPsynthase which produces ATP

Question 34

How much ATP is made from one NADred entering the chain?

Answer 34

3 ATP molecules | -3 proton pumps involved

Question 35

How much ATP is made from one FADred entering the chain?

Answer 35

2 ATP molecules | -2 proton pumps involved

Question 36

What is the terminal electron acceptor?

Answer 36

•Oxygen | -combines protons (H+) and electrons (e-) and is reduced to H2O

Question 37

Why is oxygen important in aerobic respiration?

Answer 37

•It is the terminal electron acceptor in the ETC -accepts H+ and e- and is reduced to H20 •Drives the ECT •Allows NAD and FAD to return to the Krebs cycle

Question 38

How can cyanide affect aerobic respiration?

Answer 38

•Respiratory inhibitor •Non-competitive inhibitor of cytochrome oxidase -an enzyme associated with the final proton pump in the ETC •When cyanide attaches to the enzyme, the ETC cannot function and oxidative phosphorylation cannot occur -ATP is not produced

Question 39

Where does each stage of respiration take place?

Answer 39

* Glycolysis - cytoplasm * Link reaction - mitochondrial matrix * Krebs cycle - mitochondrial matrix * ETC - inner mitochondrial membrane/cristae

Question 40

What is produced at each stage of respiration?

Answer 40

* Glycolysis - pyruvate, ATP, NADH2 * Link reaction - Acetyl Co-A, NADH2, CO2 * Krebs cycle - CO2, ATP, NADH2, FADH2 * ETC - NAD, FAD, ATP, H2O

Question 41

Where is ATP produced and how much?

Answer 41

``` •Glycolysis -2 ATP •Krebs cycle -2 ATP •ETC -34 ATP ```

Question 42

Where in the cell does anaerobic respiration occur?

Answer 42

In the cytoplasm

Question 43

How does anaerobic respiration occur?

Answer 43

•NADred and FADred are not oxidised -become limiting factors -dehydrogenation reactions of Krebs cycle and Link reaction cannot occur •Glycolysis continues as the pyruvate enters a different pathway and is reduced -oxidising NADred to NAD

Question 44

What is the pyruvate converted into in animals?

Answer 44

Lactate (3C)

Question 45

What is the pyruvate converted into in plants and fungi?

Answer 45

Ethanol (2C)

Question 46

Respiratory quotient (RQ)

Answer 46

RQ = Volume of CO2 produced/ Volume of O2 taken in

Question 47

What is the RQ of glucose?

Answer 47

1.0

Question 48

What is the RQ of a fatty acid?

Answer 48

0.7

Question 49

What is the RQ of protein?

Answer 49

0.9

Question 50

What is the RQ of anaerobic respiration?

Answer 50

>1

Question 51

Compare the breakdown of glucose in aerobic and anaerobic respiration

Answer 51

•Aerobic respiration -complete breakdown to CO2 and H2O •Anaerobic respiration -incomplete breakdown of glucose

Question 52

Compare ATP production of aerobic and anaerobic respiration

Answer 52

•Aerobic respiration -38 ATP •Anaerobic respiration -2 ATP

Question 53

Compare efficiency of aerobic and anaerobic respiration

Answer 53

``` •Aerobic respiration -40% efficient •Anaerobic respiration -2% efficient -energy remains locked up in lactate/ethanol ```

Question 54

Why do lipids release lots of energy? (Alternative respiratory substrates)

Answer 54

•Longer fatty acids have more H - more NAD reduced - more ATP

Question 55

How can lipids be used in respiration? (Alternative respiratory substrates)

Answer 55

•Glycerol is converted into 3C -enters Glycolysis •Long-chain fatty acid molecules are split into 2C acetate fragments -enter Krebs cycle as acetyl CoA

Question 56

How can proteins be used in respiration? (Alternative respiratory substrates)

Answer 56

•High protein diet -excess amino acids are metabolised in the liver •If a person is starving, tissue protein is hydrolysed into amino acids •Amino acids are deaminated, forming ammonia and a keto-acid -keto-acids enter glycolysis and Krebs cycle

Question 57

Explain the advantages of collecting results from the whole class

Answer 57

* A statistical test can be used to increase confidence | * Increase reproducibility

Question 58

Where is the most acidic region of the mitochondria and why?

Answer 58

* Intermembrane space | * H+ ions

Question 59

Function of DNA in respiration

Answer 59

Allows coding for polypeptides

Question 60

Function of ribosomes in respiration

Answer 60

Protein synthesis to produce ATP

Question 61

Suggest a suitable tissue to examine mitochondrial function and explain why

Answer 61

* Muscle tissue * Abundance of mitochondria * Easy to extract

Question 62

Why does aerobic respiration yield fewer molecules of ATP than the theoretical maximum?

Answer 62

* Some is used to actively transport pyruvate into the mitochondria for Link Reaction * Some used to actively transport H+ from reduced NAD formed in glycolysis, into the mitochondria * Not all NADH2 is used to feed the ETC * Not all H+ is used to generate ATP through ATP synthase