Respiration

Question 1

Why do organisms need to respire

Answer 1

Produces ATP
AT against concentration gradient
Metabolic reactions
Muscle contraction

Question 2

Describe the structure of a mitochondrion

Answer 2

Surrounded by double membrane
Folded inner membrane forms Cristae, sire of electron transport chai.
Fluid matrix: contains mitochondrial DNA, respiratory enzymes, lipids and proteins

Question 3

Name the 4 main stages in aerobic respiration and where they occur

Answer 3

Glycolysis: cytoplasm
Link reaction: mitochondrial matrix
Krebs cycle: mitochondrial matrix
Oxidative phosphorylation: via electron transfer chain: membrane of Cristae

Question 4

Outline the stages of glycolysis

Answer 4

Glucose is phosphorylated to hexose bisphosphate by 2 ATP
Hexose bisphosphate splits into 2TP
2 x TP is oxidised to 2 x pyruvate
Net gain: 2 reduced NAD and 2 ATP

Question 5

How does pyruvate from glycolysis enter the mitochondria

Answer 5

Active transport

Question 6

What happens during the link reaction

Answer 6

Oxidation of pyruvate(3C) to acetate(2C): decarboxylation and 2 H atoms (used to reduce 1 x NAD)
Acetate combines with coenzyme A to form acetyl coenzyme A

Question 7

What is the summary equation for the the link reaction

Answer 7

Acetyl Co A+reduced NAD+co2

Question 8

What happens in the Krebs cycle

Answer 8

Series of redox and enzyme controlled reactions that produces:
ATP by substrate level phosphorylation
Reduced coenzymes
CO2 from decarboxylation
Acetyl coA (2c) reacts with oxaloacetate (4c).
Cycle regenerates oxaloaceteate

Question 9

Outline the stages of the Krebs cycle

Answer 9

Acetyl coA delivers an acetyl group in the cycle. 2C acetyl group combines with 4 carbon oxaloacetate to form 6c citrate
6c undergo dehydrogenation giving off reduced NAD and decarboxylation = c. 5 carbon compound formed
Undergoes further dehydrogenation and decarboxylation, regen 4c

Question 10

What is the electron transport chain

Answer 10

Series of carrier proteins embedded in membrane of the Cristae mitochondrial of mitochondria
Produces ATP through oxidative phosphorylation via chemiosmosis

Question 11

What happens in the ETC

Answer 11

Electrons released from reduced NAD and Fad undergo successive redox reactions
Oxygen acts as final electron acceptor

Question 12

How does chemiosmosis produce ATP during aerobic respiration

Answer 12

ETC helps with the active transport of H+ ions from mitochondrial matrix into inter membrane space
H+ ions move down concentration gradient into matrix via channel protein ATP synthase
ATP synthase catalyses ADP+ pi-> ATP

Question 13

Describe the process of phosphorylation and dehydrogenation

Answer 13

Removal of hydrogen atoms to form two pyruvate molecules

Adding a phospahte to glucose = hexose bisphosphate

Question 14

Explain how NAD acts as a coenzyme in glycolysis

Answer 14

NAD coenzymes accept the removed hydrogens = 2 reduced NAD

Question 15

Describe the process of dehydrogenation and phosphorylation

Answer 15

Removal of hydrogen from triose phopshate molecules to form pyruvate and reduction of NAD/ formation of reduced NAD
P- addition of phosphate group to a glucose molecule forming hexose bisphospahte

Question 16

Explain how NAD act as a coenzyme in glycolysis

Answer 16

NAD accepts hydrogen and is reduced during the formation of pyruvate, supplies hydrogen to enzyme involved in later stage of respiration

Question 17

Explain the meaning of substrate level phosphorylation

Answer 17

Addition of phosphate group to ADP for the formation of ATP

Question 18

Outline the importance of dehydrogenation and phosphorylation in glycolysis

Answer 18

Dehydrogenation - hydrogen removed in breakdown of glucose, required at a layer stage
Phosphorylation- addition of phosphate groups destabilise large molecule

Question 19

Explain why the removal of carbon dioxide in the link reaction is called oxidative

Answer 19

Hydrogen is also removed, removal of hydrogen oxidises pyruvate

Question 20

Name one organic compound and one inorganic compound produced in the link reaction

Answer 20

Acetyl group and carbon dioxide

Question 21

Suggest why glycolysis occurs in the cytoplasm but not in the mitochondrial matrix

Answer 21

Enzymes required are in the cytoplasm
Glucose molecule too large to move into mitochondrion
No transport proteins for pyruvate

Question 22

Compare the structures of ATP and NAD

Answer 22

ATP- three phosphate groups, one ribose, one nitrogenous base
NAD - 2 phosphate groups, 2 ribose, two nitrogenous bases

Question 23

Explain why ATP can be considered a co enzyme

Answer 23

It links reaction

Energy is releases as a result of the activity of one enzyme and used by another enzyme

Question 24

Suggest why the Krebs cycle is termed aerobic

Answer 24

Hydrogen needs to be removed for cycle to continue, hydrogen removes using NAD/FAD and reduced
Oxygen required for electron transport

Question 25

Explain why hydrogen have to be actively pumped across the membrane from the matrix and return to the matrix but diffusion through ATP synthase

Answer 25

Actively pumped to increase concentration gradient, energy required as moving from low to high concentration

Question 26

Explain why the electrons released from reduced FAD lead to the synthesis of less ATP than the electrons released from reduced NAD

Answer 26

Reduced NAD releases electrons to carriers at the START of the ETC
Reduced FAD releases electrons to carriers AFTER the start of the etc
FAD electrons transported a shorter distance so fewer protons are actively transported

Question 27

Describe why alcoholic fermentation can be described as having more in common with aerobic respiration than with fermentation E

Answer 27

ETC present in some types of anaerobic respiration , aerobic respiration include presence of ETC, no ETC present in lactate fermentation

Question 28

Explain why the build up of lactic acid eventually stops muscle contraction when we experience fatigue

Answer 28

Increase in lactic acid -> decrease in pH
muscle contraction depend on enzymes, decreasing pH denatures protein
No longer functional

Question 29

Outline the benefits to RBC and cardiac muscle of different types of respiration they undertake

Answer 29

RBC adapted to carry oxygen, lack of mitochondria means more space for haemoglobin, increased oxygen transport

Question 30

Outline the respiratory pathway of a triglyceride

Answer 30

Triglyceride is broken down into fatty acids and glycerol, fatty acids undergo beta oxidation forming acetyl groups, acetyl groups are taken into Krebs cycle by coenzyme A, glycerol is converted to pyruvate which undergoes oxidative phosphorylation

Question 31

Describe the difference between a respirometer and a spirometer

Answer 31

Both measures oxygen uptake/carbon dioxide releases, so rate of respiration, respirometer is modified spirometer usually for smaller organism