Respiration- Unit 3.3

Question 1

What is the word equation for aerobic respiration?

Answer 1

Glucose + oxygen –> Carbon dioxide +water + energy

Question 2

What is the word equation for anaerobic respiration in animals?

Answer 2

Glucose –> lactic acid + energy

Question 3

What is the word equation for anaerobic respiration in yeast? (fermentation)

Answer 3

Sugar –> alcohol + carbon dioxide + energy

Question 4

What are the 4 stages of aerobic respiration?

Answer 4

-Glycolysis
-Link reaction
-Krebs cycle
-Oxidative phosphorylation (ETC)

Question 5

Explain what glycolysis is: (7)

Answer 5

(lysing glucose)
-First stage in aerobic respiration & only stage in anaerobic.
-Occurs in cytoplasm of cell.
-Starts with phosphorylating 6C glucose into 6C hexose phosphate, then into 2 molecules of 3C triose phosphate.
-This is then oxidised (hydrogen removed from each) and transferred to NAD+.
-This forms 2 reduced NAD (NADH + H+)
-This converts the triose phosphate into 2 pyruvate (3C)
-YIELDS 4 ATP (enough energy was released to synthesise this)

Question 6

For glycolysis, how much ATP is used & produced per one molecule of glucose? What about NADH? (reduced NAD)

Answer 6

-4 ATP directly produced via substrate level phosphorylation (ADP –> ATP)
-2 ATP used to phosphorylate glucose
-SO NET GAIN OF 2 (4-2)
- 2 NADH produced
2 MOLECULES OF PYRUVATE THEN ENTER LINK REACTION

Question 7

Explain the link reaction: (3)

Answer 7

-Links glycolysis & krebs cycle together.
-Only uses 1 pyruvate so occurs twice (& krebs)
-Converts pyruvate into Acetyl Coenzyme A

Question 8

How is pyruvate converted into Acetyl Coenzyme A in the link reaction?

Answer 8

-3C pyruvate diffuses from cytoplasm to mitochondiral matrix.
-Pyruvate decarboxylated (CO2 removed)
-Pyruvate dehydrogenated (H+ removed)
-This hydrogen is accepted by NAD to form NADH (reduced)
-Remaining 2 carbon molecules combine with Coenzyme A, forming 2 molecules of ACETYL coenzyme A.
-NO ATP PRODUCED.

Question 9

What does reducing NAD mean?

Answer 9

It gains an electron, making NADH

Question 10

In the link reaction, how many molecules are produced/used?

Answer 10

-2 molecules of Acetyl coenzyme A produced & used in krebs cycle
-2 CO2 molecules released as WASTE product of respiration
-2 molecules of NADH formed & go to ETC

Question 11

Explain the krebs cycle:

Answer 11

-Occurs in mitochondrial matrix.
-Happens once per pyruvate but occurs twice per glucose.
-Acetyl CoA (2C) enters krebs cycle from link reaction.
-It combines with a 4C molecule, forming a 6C molecule.
-Acetyl CoA regenerated.
-6C is decarboxylated & dehydrogenated.
-CO2 released as waste & H picked up by NAD and FAD
-4C is regenerated to combine with more Acetyl CoA.

Question 12

What are NAD and FAD?

Answer 12

Hydrogen acceptors

Question 13

PER GLUCOSE MOLECULE, state the number of molecules produced in the krebs cycle: (4)

Answer 13

6 NADH
2 FADH
2 ATP
4 CO2
(half for per Acetyl CoA)

Question 14

Explain the ETC: (oxidative phophorylation) (9)

Answer 14

-Occurs in inner membrane of mitochondria
-Oxygen required
-H atoms released from NADH & FADH and are oxidised to NAD & FAD.
-H splits into protons & electrons
-E move along the chain, losing energy at each level (3) which is used to pump protons between inner and outer membrane.
-ATPsynthase allows ADP to convert into ATP
-Protons and electrons recombine to make hydrogen, which combines with oxygen, making water at end of chain.
-Oxygen is final hydrogen acceptor.
-Happens at 3 points of chain

Question 15

How many ATP can one NADH make?

Answer 15

3

Question 16

How many ATP can one FADH make?

Answer 16

2

Question 17

What is pyruvate converted into in anaerobic respiration in animals?

Answer 17

Lactic acid (NADH cannot be regenerated so link reaction cannot take place)