Phys 41 Flashcards

In peripheral tissues, CO₂ binds directly to amino groups on hemoglobin. What compound is formed?

A. Carboxyhemoglobin
B. Carbaminohemoglobin
C. Methemoglobin
D. Oxyhemoglobin

Why is CO₂ readily released from hemoglobin in the lungs?

A. Oxygenation decreases hemoglobin CO₂ affinity
B. Deoxygenation decreases hemoglobin CO₂ affinity
C. Acidosis increases hemoglobin CO₂ binding
D. Bicarbonate permanently binds hemoglobin

Why does O₂ diffuse from alveoli into pulmonary capillary blood?

A. Blood PO₂ exceeds alveolar PO₂
B. Alveolar PO₂ exceeds blood PO₂
C. Alveolar PCO₂ exceeds blood PCO₂
D. Hemoglobin actively transports oxygen

Pulmonary capillary blood enters the lungs with a PO₂ of 40 mmHg. Alveolar PO₂ is 100 mmHg. What happens next?

A. O₂ diffuses into alveoli
B. CO₂ diffuses into blood
C. O₂ diffuses into blood
D. Oxygen diffusion immediately stops

Under normal conditions, oxygen is carried to the tissues almost entirely by _______

Compared with O₂, how rapidly can CO₂ diffuse across the respiratory membrane?

A. About 5 times faster
B. About 10 times faster
C. About 20 times faster
D. About 40 times faster

Why does pulmonary O₂ diffusing capacity increase during exercise?

A. Alveolar walls become thinner
B. More pulmonary capillaries are recruited
C. Oxygen becomes more soluble
D. Hemoglobin concentration rapidly increases

Exercise improves O₂ diffusion partly by improving which relationship, especially in the upper lungs?

A. Pleural pressure gradient
B. Plasma oncotic pressure
C. Airway resistance gradient
D. Ventilation-perfusion matching

If the blood flow through a particular tissue is increased, greater quantities of O2 are transported into the tissue and the tissue PO2 becomes _______.

Why do venous RBCs contain more chloride than arterial RBCs?

A. Chloride replaces exiting bicarbonate
B. Chloride binds directly to CO₂
C. Chloride buffers hydrogen ions
D. Chloride increases oxygen affinity

In systemic tissues, which ion movement defines the chloride shift?

A. Chloride exits, bicarbonate enters
B. Chloride enters, bicarbonate exits
C. Sodium enters, chloride exits
D. Potassium exits, bicarbonate enters

Why is the respiratory quotient lower during fat metabolism?

A. Less oxygen is consumed
B. More bicarbonate is retained
C. More oxygen is used per CO₂
D. Less ATP is produced

The carbonic acid formed when CO2 enters the blood in the peripheral tissues _______ the blood pH

When a person is using exclusively carbohydrates for body metabolism, R rises to ______

Why does O₂ diffuse from systemic capillaries into surrounding tissues?

A. Tissue PO₂ exceeds capillary PO₂
B. Capillary PO₂ exceeds tissue PO₂
C. Tissue PCO₂ exceeds capillary PCO₂
D. Capillary PCO₂ exceeds tissue PCO₂

Cellular metabolism causes intracellular PCO₂ to rise. What happens next?

A. CO₂ diffuses into tissue capillaries
B. CO₂ diffuses into surrounding cells
C. O₂ diffuses into venous blood
D. O₂ remains inside capillaries

Which direction does oxygen normally move in systemic tissues?

A. Cells to capillary blood
B. Alveoli to tissue cells
C. Capillary blood to cells
D. Cells to lymphatic vessels

Which statement best explains tissue gas exchange?

A. Both gases move into cells
B. Both gases move into blood
C. O₂ enters cells, CO₂ enters blood
D. CO₂ enters cells, O₂ enters blood

The ________ coefficient is the percentage of blood oxygen that leaves the blood and enters the tissues as blood passes through the capillaries

If tissue cells increase their oxygen consumption, what happens to interstitial PO₂?

A. It rises
B. It falls
C. It remains unchanged
D. It equals arterial PO₂

Why does increased cellular metabolism promote more O₂ diffusion from blood into tissues?

A. Tissue PO₂ rises
B. Capillary PO₂ falls below tissue
C. Tissue PO₂ falls further
D. Hemoglobin stops binding oxygen

Which statement best defines pulmonary shunt flow?

A. Blood bypasses alveolar gas exchange
B. Air bypasses pulmonary capillaries
C. Blood remains inside alveoli
D. Oxygen bypasses hemoglobin binding

Normal physiologic shunting partly occurs because bronchial venous blood:

A. Drains only into right atrium
B. Never enters systemic circulation
C. Becomes fully oxygenated first
D. Mixes with oxygenated pulmonary blood

During strenuous exercise, the body may require up to 20 times the normal amount of O₂. Despite increased cardiac output shortening pulmonary capillary transit time, arterial blood remains nearly fully oxygenated. What best explains this?

A. Pulmonary blood flow decreases
B. O₂ diffusion has large safety factor
C. Hemoglobin affinity greatly increases
D. Alveolar ventilation becomes unnecessary

At rest, pulmonary capillary blood remains near the alveoli about three times longer than necessary for complete O₂ saturation. What is the main significance of this reserve?

A. Prevents CO₂ from entering blood
B. Allows oxygenation during faster blood flow
C. Maintains low pulmonary capillary PO₂
D. Limits oxygen delivery during exercise

During exercise, increased cardiac output may reduce pulmonary capillary transit time by approximately one-half. Why is this usually not a problem in a healthy person?

A. O₂ saturation normally requires entire transit
B. O₂ diffusion stops after exercise begins
C. Exercise decreases tissue oxygen requirements
D. Blood normally oxygenates well before exit

Which two factors determine the total amount of O₂ available to tissues?

A. Blood O₂ and blood flow
B. Blood CO₂ and ventilation
C. Hemoglobin and airway resistance
D. Ventilation and diffusion distance

Which enzyme rapidly catalyzes the reaction of CO₂ and H₂O to form carbonic acid?

A. Carbonic anhydrase
B. Catalase
C. Carbonic reductase
D. Cytochrome oxidase

Carbonic anhydrase is found in especially high concentrations in which cells?

A. Platelets
B. Neutrophils
C. Red blood cells
D. Hepatocytes

What can cause a shift to the left of the O2-Hb Dissociation curve?

Increase in ______

Why does blood PO₂ fall from about 104 mmHg to 95 mmHg before entering the left ventricle?

A. Bronchial venous blood mixes in
B. Pulmonary ventilation suddenly decreases
C. Hemoglobin releases oxygen in veins
D. Carbonic acid consumes dissolved oxygen

Which blood contributes to the normal venous admixture lowering pulmonary venous PO₂?

A. Coronary arterial blood
B. Bronchial venous blood
C. Pulmonary arterial blood
D. Systemic arterial blood

Why does carbonic acid formation not severely decrease blood pH under normal conditions?

A. Bicarbonate binds all CO₂
B. Hemoglobin buffers most protons
C. Chloride destroys carbonic acid
D. Oxygen neutralizes free protons

Describe the effects of increased or decreased metabolic rate on tissue PCO2:

↑ metabolic rate --> _____ tissue PCO2
↓ metabolic rate --> _____ tissue PCO2

Describe the effects of increased or decreased blood flow on tissue PCO2:

↓ in BF --> _____ tissue PCO2
↑ in BF --> _____ tissue PCO2

What effect does increased tissue metabolism have on interstitial PO₂?

A. Increases interstitial PO₂
B. Decreases interstitial PO₂
C. Prevents oxygen diffusion
D. Raises capillary PO₂

What effect does increased tissue blood flow have on interstitial PO₂?

A. Decreases interstitial PO₂
B. Increases interstitial PO₂
C. Eliminates interstitial oxygen
D. Has no effect

In the pulmonary capillaries, oxygen binds to hemoglobin. This makes hemoglobin more acidic and decreases its tendency to bind CO₂ as carbaminohemoglobin. What is the resulting effect?

A. CO₂ is released from hemoglobin
B. CO₂ binds hemoglobin more strongly
C. Bicarbonate remains trapped in RBCs
D. Carbonic acid formation is prevented

In the lungs, oxygenation of hemoglobin causes H⁺ ions to be released. These H⁺ ions combine with bicarbonate to form carbonic acid, which then dissociates into water and another substance that can diffuse into the alveoli. What is produced?

A. Oxygen
B. Carbon dioxide
C. Chloride
D. Carbaminohemoglobin

In most cells, what is the main limiting factor for the rate of metabolic reactions?

A. Oxygen concentration
B. ADP concentration
C. Carbon dioxide concentration
D. Hemoglobin concentration

Why is oxygen usually not the limiting factor for intracellular metabolism?

A. Cells require very little PO₂
B. Oxygen is produced intracellularly
C. Hemoglobin enters most cells
D. ADP directly generates oxygen

How is most oxygen transported in the blood?

A. Dissolved freely in plasma
B. Bound chemically to hemoglobin
C. Converted into bicarbonate
D. Bound primarily to albumin

Approximately what percentage of blood oxygen is carried bound to hemoglobin?

A. 3%
B. 25%
C. 70%
D. 97%

Approximately what percentage of blood oxygen is transported in dissolved form?

A. 3%
B. 10%
C. 30%
D. 97%

In the lungs, a high PO₂ favors which interaction between oxygen and hemoglobin?

A. Oxygen binds hemoglobin
B. Oxygen leaves hemoglobin
C. Hemoglobin releases BPG
D. Hemoglobin binds carbon dioxide

In metabolically active tissues, a relatively low PO₂ favors which process?

A. Oxygen release from hemoglobin
B. Oxygen binding to hemoglobin
C. BPG release from tissues
D. Carbon dioxide binding oxygen

During chronic hypoxia, increased BPG shifts the oxygen-hemoglobin dissociation curve rightward. What is the major benefit?

A. Increased oxygen loading in tissues
B. Decreased oxygen delivery to tissues
C. Increased oxygen unloading in tissues
D. Decreased hemoglobin oxygen dissociation

Increased BPG is especially important as an adaptation to:

A. Hyperoxia
B. Hypoxia
C. Hypercapnia
D. Respiratory alkalosis

In a pathologic state, cells become located unusually far from nearby capillaries. Oxygen diffusion becomes too slow to maintain adequate intracellular PO₂. What best describes this situation?

A. Blood flow-limited metabolism
B. Oxygen diffusion-limited metabolism
C. ADP-independent metabolism
D. Carbon dioxide-limited metabolism

During oxygen diffusion-limited metabolism, intracellular PO₂ falls below the level required to maintain normal cellular reactions. What no longer primarily determines oxygen use?

A. Intracellular ADP formation
B. Capillary carbon dioxide level
C. Plasma bicarbonate concentration
D. Hemoglobin carbon dioxide binding

Oxygen diffusion-limited metabolism is most likely to occur under which circumstance?

A. Normal resting physiology
B. Routine aerobic exercise
C. Certain pathologic states
D. Normal postprandial metabolism

Compared with oxygen, how readily does carbon dioxide diffuse through tissues?

A. About twice as rapidly
B. About five times rapidly
C. About twenty times rapidly
D. About fifty times rapidly

Why does CO₂ require a smaller partial-pressure gradient than O₂ for effective diffusion?

A. CO₂ diffuses much more rapidly
B. CO₂ binds hemoglobin more strongly
C. CO₂ has higher capillary pressure
D. CO₂ requires active transport

After bicarbonate is formed inside an RBC, what normally happens to it?

A. Remains trapped inside RBC
B. Diffuses into the plasma
C. Binds directly to hemoglobin
D. Converts immediately into oxygen

Bicarbonate exits the RBC in exchange for which ion?

A. Sodium
B. Potassium
C. Chloride
D. Calcium

Which membrane protein allows bicarbonate and chloride to move in opposite directions across the RBC membrane?

A. Sodium-potassium ATPase
B. Bicarbonate-chloride carrier
C. Calcium ATPase
D. Glucose transporter

What 4 factors cause a shift to the right of the O2-Hb Dissociation curve?

Shift to the right (decreased saturation):

_____ pH (increased _____ ions)

_____ CO2

_____ temperature

_____ 2,3-BPG

During exercise, which two changes promote increased O₂ release from hemoglobin to active tissues?

A. Increased CO₂/H⁺ and temperature
B. Decreased CO₂ and temperature
C. Increased pH and bicarbonate
D. Decreased H⁺ and metabolism

Exercising muscle produces more CO₂ and metabolic acids, increasing H⁺ concentration. What effect does this have on hemoglobin?

A. Increases O₂ affinity
B. Promotes O₂ unloading
C. Prevents CO₂ formation
D. Promotes O₂ storage

Increased tissue temperature during exercise has what effect on oxygen delivery?

A. Promotes O₂ release from hemoglobin
B. Increases hemoglobin O₂ affinity
C. Prevents oxygen diffusion
D. Decreases tissue oxygen use

Which statement best describes the Haldane effect?

A. CO₂ binding promotes O₂ release
B. Bicarbonate binding promotes CO₂ retention
C. H⁺ binding promotes O₂ loading
D. O₂ binding promotes CO₂ release

The Bohr effect describes:

A. O₂ causing CO₂ release
B. CO₂ promoting O₂ release
C. O₂ increasing bicarbonate formation
D. CO₂ increasing O₂ binding

A cell develops a higher intracellular ADP concentration during increased metabolic activity. What happens to oxygen usage?

A. Oxygen usage increases
B. Oxygen usage decreases
C. Oxygen usage stops
D. Oxygen usage remains constant

A decrease in intracellular ADP concentration is associated with:

A. Greater oxygen usage
B. Lower oxygen usage
C. Greater CO₂ diffusion
D. Increased hemoglobin concentration

How does chloride concentration in venous RBCs compare with arterial RBCs?

A. Lower in venous RBCs
B. Higher in venous RBCs
C. Equal in both
D. Absent in arterial RBCs

Why do venous RBCs contain more chloride than arterial RBCs?

A. Chloride increases hemoglobin oxygen affinity
B. Chloride binds directly to oxygen
C. Chloride converts CO₂ into carbonic acid
D. Chloride exchanges for exiting bicarbonate

A patient is given a carbonic anhydrase inhibitor, reducing conversion of CO₂ into bicarbonate inside RBCs. What effect is expected on tissue PCO₂?

A. Tissue PCO₂ decreases markedly
B. Tissue PCO₂ rises substantially
C. Tissue PCO₂ remains unchanged
D. Tissue PCO₂ falls below arterial levels

Why does inhibition of carbonic anhydrase increase tissue PCO₂?

A. CO₂ transport as bicarbonate decreases
B. Hemoglobin binds more oxygen
C. CO₂ diffusion becomes much faster
D. Bicarbonate production greatly increases

Increased tissue metabolism raises both CO₂ and H⁺ concentrations. What happens to the oxygen-hemoglobin dissociation curve?

A. Shifts left
B. Shifts right
C. Becomes vertical
D. Remains unchanged

The rightward shift caused by increased CO₂ and H⁺ is known as which phenomenon?

A. Haldane effect
B. Bohr effect
C. Chloride shift
D. Shunt effect

Which list correctly identifies the three major forms of CO₂ transport in blood?

A. Dissolved, bicarbonate, carbaminohemoglobin
B. Bicarbonate, oxyhemoglobin, methemoglobin
C. Dissolved, chloride, carbonic acid
D. Carbaminohemoglobin, oxygen, chloride

What is the major form of CO₂ transport in blood?

A. Dissolved CO₂
B. Bicarbonate
C. Carbaminohemoglobin
D. Carbonic acid

Approximately what percentage of CO₂ is transported as bicarbonate?

A. 7%
B. 20%
C. 50%
D. 70%

Approximately what percentage of CO₂ is transported bound to hemoglobin as carbaminohemoglobin?

A. 7%
B. 20%
C. 50%
D. 70%

Carbon monoxide causes severe tissue hypoxia primarily because it:

A. Destroys circulating hemoglobin
B. Competes strongly with O₂ for hemoglobin
C. Greatly decreases dissolved oxygen pressure
D. Prevents pulmonary CO₂ diffusion

Why may carbon monoxide poisoning fail to trigger a strong respiratory response to hypoxia?

A. Blood PO₂ may remain normal
B. Blood PCO₂ becomes extremely low
C. Carbon monoxide blocks chemoreceptors directly
D. Hemoglobin releases excessive oxygen