PBL 4: Jim Christopolous -Oxygen

Question 1

Describe the flow of air into the lungs from Nasal/Oral cavity to Alveoli

Answer 1

Nasal/Oral Cavity → Pharynx → Larynx → Trachea → L/R Main Bronchus → Lobar Bronchi → Segmental Bronchi → Bronchioles → several divisions → Terminal Bronchioles → Respiratory Bronchioles → Alveolar Ducts → Alveolar Sacs → Alveoli

Question 2

Type I Alveolar Cells

Answer 2

Simple Squamous Epithelia

Gas Exchange

Question 3

Type II Alveolar Cells

Answer 3

Cuboidal Epithelia

Secrete Surfactant

Question 4

How does gas exchange occur?

Answer 4

Simple passive diffusion down partial pressure gradients

Question 5

What are the partial pressure gradients for PO₂ and PCO₂ throughout the body.

Answer 5

Question 6

What 4 factors affect alveolar gas exchange?

Answer 6

1. Partial pressure difference (High altitude)
2. Thickness of membrane (Pulmonary Edema, fibrosis, pneumonia)
3. Surface area (breath more deepy, emphysema)
4. Ventilation-perfusion ratio

Question 7

How is oxygen transported in the blood?

Answer 7

1. 5% Dissolved in plasma
2. 5% bound to Hb

Question 8

How is CO₂ transported in the blood?

Answer 8

7% dissolved in the plasma

23% as HbCO₂

80% as HCO₂^-

Question 9

What partial pressure differences drive the transportation of oxygen from blood to cells

Answer 9

Arterial Blood PO2 (100 mmHg)→ Interstitial Fluid (40mmHg) → Cells (23 mmHg)

Question 10

Venous blood PO₂

Answer 10

40mmHg

Question 11

What are the partial pressure differences that drive the transportation of CO₂ from the tissues to the blood

Answer 11

Cell (47mmHg)→ Intertitial Fluid (46mmHg) → Arterial blood (40mHg)

Question 12

Venous blood PCO₂

Answer 12

46mmHg

Question 13

What % of Hb is saturated with oxygen in the arterial blood and venous blood

Answer 13

Arterial Blood: ~96%

Venous blood: ~64%

Question 14

How does CO poisoning affect the Oxygen-haemoglobin dissociation curve?

Answer 14

1. Increases Hb affinity for Oxygen (shifts curve to the left)
2. Decreases oxygen delivery for a given PO₂

Question 15

What factors cause a right shift in the Oxygen-Haemoglobin dissociation curve?

Answer 15

Right shift = reduced Hb affinity for O

CADET, face right!

Carbon Dioxide

Acid

DPG

Excercise

Temperature

+ Any physiologicla state where tissues need more oxygen

Question 16

How does binding of CO to Hb reduce its O₂ carrying capacity?

Answer 16

1. CO competes with oxygen for the same binding sites on Hb (200-240 times higher affinity)
2. Causes a conformational change that increases Hb affinity for O₂ therefore more tighly held (curve shifts left)

Question 17

Which four structures detect information that stimulates the respiratory center in the medulla?

Answer 17

1. Peripheral Chemoreceptors: aortic and carotid bodies (CO2, O2, H+)
2. Central Chemoreceptors in medulla (H+ derived from CO2)
3. Stretch receptors in smooth muscle (prevent overinflation)
4. Cortex: Voluntary control, before exercise, emotion

Question 18

What 3 signals prompt the medullary respiratory center to increase ventilation?

Answer 18

1. Decreased arterial PO2
2. Increased arterial PCO2
3. H+ concentration

Question 19

What is the main regulator of ventilation?

Answer 19

CO2 generated H+ in the brain

Question 20

How does increased arterial PCO2 stimulate the medullary respiratory centers?

Answer 20

1. Increased PCO2 decreases CSF pH
2. Central chemoreceptors in medulla respond to H+ in CSF (70% of response)
3. Afferent impulses sent to medullary respiratory centers
4. Increased arterial PCO2
5. Peripheral chemoreceptors (30% of response) respond
6. Afferent impulses sent to medullary respiratory centers

Question 21

What is the medullary respiratory center response to afferent impulses from the central and peripheral chemoreceptors following an increase in arterial PCO2?

Answer 21

Efferent impulses sent to respiratory muscles → Increased ventilation (more CO2 exhaled) → Arterial PCO2 and pH return to normal

Question 22

Outline the ATP yield from GTP, NADH, FADG and the complete breakdown of 1 molecule of glucose in the presence of oxygen.

Answer 22

GTP = 1 ATP

NADH = 2.5 ATP

FADH = 1.5 ATP

Glucose = 32 ATP

Question 23

Glucose is oxidised in the glycolitic pathway to yield what products?

Answer 23

1. 2 ATP
2. 2 NADH
3. Pyruvate

Question 24

What are the consequences of reduced availability of O2 to bind to cytochrome oxidase on the capacity of the cell to synthesis ATP?

Answer 24

1. ETC shut down -can’t combine H+ and O2 at cytochrome c oxidase (Complex IV)
2. Increases concentration of NADH and reduced NAD+ in mitochondria
3. Decreased NAD+ shuts down TCA as NAD no longer available to accept electrons
4. Pyruvate accumulation due to decreased TCA
5. Pyruvate converted to lactate to generate small amounts of ATP and regenerate NAD
6. Ongoing hydrolysis of ATP releasing H+ and production of Lactate = Lactic acidosis

Question 25

Name the 6 main components of the ETC

Answer 25

1. NADH dehydrogenase (Complex I) 2. Succinate dehydrogenase 3. Coenzyme Q (Complex II) 4. Cytochrome C 5. Cytochrome oxidase (Complex IV) 6. ATP Synthase

Question 26

What effect does cyanide have on the ETC?

Answer 26

Cyanide binds to cytochrome c oxidase, preventing O2 combination with H+. This causes an increase in O2 levels without production of ATP

Question 27

What effect does DNP have on the ETC?

Answer 27

Dinitrophenol is an ETC uncoupler. It is a lipophilic weak acid that vinds the H+ in the intramembrane space, moving across the membrane and dissociating. This process dissolves the H+ gradient causing unregulated usage of NADH and FADH2

Question 28

How is the energy released during the transportation of electrons through the ETC used to establish a proton gradient across the mitochondrial membrane? How is this used to generate ATP?

Answer 28

Electrons are passed sequentially from complex to complex, gradualling decreasing in energy. At each step, this change in energy is used to pump protons across the membrane against their concentration gradient. Hydrogen flows through ATP synthase, down its concentration gradient, providing energy for ADP and Pi to be combined to form ATP

Question 29

How is the rate of flux through the ETC controlled by availability of ADP?

Answer 29

1. Flux of Hydrogen across membrane and thus ATP synthesis highly coupled with ADP concentration 2. ADP/ATP concentrations in dynamic equilibrium 3. Increased ADP through Increased ATP hydrolysis promotes increased ATP synthesis 4. Decreased ADP through decreased hydrolysis of ATP results in decreased synthesis of ADP 5. Thus the rate of ATP synthesis is highlly matched to the leve lof ADP

Question 30

Outline effects and reaponse of the cell when an uncoupling agent uncouples electron transport and ATP synthesis

Answer 30

1. No ATP production 2. NAD+ recycled, cell tries to increase ATP synthesis by ramping up the activity of glycolysis and TCA 3. ADP continually rises as ATP is hydrolyxed 4. Increased substrate usage, increased ADP levels fail to result in increased ATP synthesis 5. The ADP/ATP levels are no longer 'coupled'

Question 31

What are the partial pressure of O2 and CO2 throughouth the body?

Answer 31

Question 32

Draw the electron transport chain

Answer 32

Question 33

Draw the Hb dissociation curve

Answer 33

Question 34

Draw the TCA Cycle

Answer 34

Question 35

Mnemonic for TCA compounds

Answer 35

Can I Keep Selling Sex For Money, Officer? Citrate Isocitrate a-Ketoglutarate Succinyl CoA Succinate Fumerate Malate Oxaloacetate