5.2 Respiration

Question 1

What is the equation for aerobic respiration?

Answer 1

Glucose and oxygen —> carbon dioxide and water

Question 2

Does how organisms acquire the reactants for respiration differ?

Answer 2

Yes

Humans and animals can inspire/expire
Fish use gills and lamella
Insects use spiracles

Question 3

What are the stages of respiration?

Answer 3

Glycolysis
Link reaction
Krebs cycle
Electron transport chain

Question 4

Where does glycolysis take place?

Answer 4

In the cytoplasm of the cell

Question 5

Describe glycolysis?

Answer 5

Glucose (6 carbons) is turned into phosphorylate glucose using 2Pi from 2ATP molecules also forming 2ADP
This splits into two identical chains
From the phosphorylated glucose TP(3C) is formed via oxidation and using NAD into NADH GP(3C) is formed
Using 2ADP + 2Pi into 2ATP pyruvate(3C) is formed
Which enters the mitochondria via active transport

Question 6

What are the overall products of glycolysis?

Answer 6

Pyruvate x2
ATP x2 (net)
NADH x2

Question 7

Where does the link reaction take place?

Answer 7

In the matrix of the mitochondria

Question 8

Describe the link reaction?

Answer 8

The whole reaction takes place twice in 2 identical chains
Pyruvate(3C) undergoes oxidative decarboxylation using NAD to NADH (reduction) whilst CO2 is released to form
Acetate(2C)
Acetyl coenzyme A is formed by adding CoA

Question 9

What are the products of the link reaction?

Answer 9

Acetyl Coenzyme A x2
CO2 x2
NADH x2

Question 10

Where does the Krebs cycle take place?

Answer 10

In the matrix of the mitochondria

Question 11

What is the Krebs cycle also called?

Answer 11

Citric acid cycle

Question 12

Describe the Krebs cycle?

Answer 12

A 4C acceptor molecule the acetyl coenzyme A adds acetate to the cycle (CoA goes back to the link reaction)
A 6C intermediate formed goes under oxidative decarboxylation using NAD - NADH (reduction) whilst CO2 is released
A 5C intermediate formed goes under oxidative decarboxylation using NAD - NADH (reduction) and ADP + Pi to form ATP whilst CO2 is released
A 4C intermediate uses NAD-NADH and FAD-FADH to turn back into the 4C acceptor molecule

Question 13

How many Krebs cycles take place per glucose molecule?

Answer 13

2 Krebs cycles per 1 glucose molecule

Question 14

What are the products formed in the Krebs cycle?

Answer 14

NADH x3
FADH x1
ATP x1
CoA x1
CO2 x2

Question 15

Where does the electron transport chain take place?

Answer 15

In/on cristae

Question 16

Describe the electron transport chain?

Answer 16

In the matrix NADH and FADH is oxidised to NAD and FAD giving electrons to a transmembrane protein (both also losing H+)
The electrons go through the transmembrane proteins and undergo redox reactions which releases energy used to transport H+ ions through the proteins
The H+ ion move back through a channel protein via facilitated diffusion which activates ATP synthase for ADP + Pi -> ATP
O2 is the terminal acceptor, removing H+ forming water to maintain to H+ conc gradient

Question 17

What products are formed in the electron transport chain?

Answer 17

NAD x1
FAD x1
ATP x34
H2O (a lot)

Question 18

How many ATP’s are made from 1 glucose molecule in total?

Answer 18

38 molecules of ATP

Question 19

What can be used as alternative respiratory substrates?

Answer 19

Glycerol (from hydrolysed triglycerides)

A deaminated amino acid

Question 20

Describe anaerobic respiration in animals?

Answer 20

Pyruvate + reduced NAD -> lactate + NAD

Question 21

Describe anaerobic respiration in plants and microorganisms?

Answer 21

Pyruvate + reduced NAD -> ethanol + CO2 + NAD

Question 23

Why does NAD need to be formed in anaerobic respiration?

Answer 23

To keep glycolysis going as 2 ATP molecules can still be produced even if the other three steps don’t work