pH Flashcards

1
Q

Why is maintaining pH in body fluids crucial for animals?

A

Abnormal H+ concentrations can influence protein function, change molecular conformation, and have serious functional consequences.

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2
Q

How does pH vary with temperature in animals?

A

Neutral pH is higher at low temperatures and lower at high temperatures.

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3
Q

What is the alphastat hypothesis?

A

It suggests that changes in pH with temperature help maintain a constant state of electrical charge on protein molecules.

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4
Q

What are the main consequences of fluctuations in H+ concentration?

A

They include altered enzyme activity, disturbed K+ levels, and changes in excitability of nerve and muscle cells

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5
Q

How do respiratory disturbances affect pH balance in animals?

A

High CO2 levels lead to respiratory acidosis, lowering pH due to increased H2CO3 in body fluids.

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6
Q

What is environmental acidosis, and how does it affect marine life?

A

Environmental acidosis is the increase in H+ concentration in oceans, weakening shells and coral skeletons and affecting growth and survival.

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7
Q

How do marine animals like corals respond to increased acidity?

A

Coral growth declines, and diversity drops in areas with increased acidity, as seen near volcanic CO2 seeps.

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8
Q

What is the effect of ocean acidification on bivalve molluscs?

A

Acidic conditions slow larval growth and shell development, negatively impacting populations.

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9
Q

How do echinoderms like sea urchins respond to pH changes?

A

Slight pH decreases can block their egg metabolism, affecting development and fitness.

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10
Q

What is the effect of pH changes on fish like walleye pollock?

A

Increased acidity causes them to use more energy for bicarbonate buffering, potentially harming growth.

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11
Q

What are the three lines of defense against changes in H+ concentration?

A

Chemical buffer systems, respiratory mechanisms, and excretory mechanisms.

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12
Q

What are the four buffer systems in vertebrates?

A

The four buffer systems are CO2-HCO3− buffer system, peptide and protein buffer system, hemoglobin buffer system, and phosphate buffer system.

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13
Q

Why is the CO2-HCO3− buffer system effective in the extracellular fluid (ECF)?

A

It is effective because HCO3− is abundant in the ECF, and both HCO3− and CO2 are closely regulated by the kidneys and respiratory system.

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14
Q

What is the role of hemoglobin (Hb) as a buffer?

A

Hemoglobin buffers H+ generated from CO2 in transit between tissues and the lungs or gills, binding H+ at systemic capillaries and releasing it at respiratory organs to form CO2.

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15
Q

How does the phosphate buffer system function in the intracellular fluid (ICF)?

A

It consists of Na2HPO4 and NaH2PO4, which donate or accept H+ to buffer pH changes, primarily in the ICF and urine.

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16
Q

How do respiratory mechanisms regulate pH?

A

By altering ventilation to control CO2 exchange in the lungs or gills, which in turn affects H2CO3 levels in body fluids.

  • increase of ventilation typically results in an increase of pH
  • why?
  • it Leads to decrease of CO2 level
17
Q

What happens when arterial pH decreases in air-breathing vertebrates?

A

The respiratory center in the brain stem is stimulated to increase ventilation, reducing CO2 and H2CO3 in the body fluids.

18
Q

How do fish primarily handle acid loads?

A

Fish primarily handle acid loads through membrane transporters rather than changes in ventilation.

19
Q

What is the role of excretory organs in pH regulation?

A

Excretory organs remove H+ from the body and reabsorb HCO3−, contributing to long-term pH balance.

20
Q

What mechanisms do fish gills use for H+ excretion?

A

Fish gills use H+-ATPase, V-ATPase, and Na+/H+ antiport for H+ excretion.

21
Q

How do mammalian kidneys regulate pH?

A

Mammalian kidneys regulate pH by adjusting H+ excretion, HCO3− reabsorption, and ammonia (NH3) secretion.

22
Q

What is the function of Type A intercalated cells in the kidneys?

A

They secrete H+ into the tubular lumen via H+/K+-ATPase and H+-ATPase pumps, contributing to acid-base balance.

23
Q

How is renal HCO3− reabsorption linked to H+ secretion?

A

Secreted H+ combines with filtered HCO3− to form H2CO3, which breaks down into CO2 and H2O, allowing CO2 to be reabsorbed and form new HCO3−.

24
Q

What are the primary transport mechanisms in the proximal tubule?

A

The primary transport mechanisms include primary active transport via H+-ATPase pumps and secondary active transport via Na+/H+ antiporters.

25
Q

How does the Na+/H+ antiporter function in the proximal tubule?

A

The Na+/H+ antiporter exchanges Na+ ions from the filtrate with H+ ions from the tubule cells, contributing to H+ secretion and Na+ reabsorption.

26
Q

What role does H+-ATPase play in the proximal tubule?

A

H+-ATPase actively transports H+ ions into the tubular lumen, aiding in acid-base balance by secreting H+.

27
Q

How is bicarbonate (HCO3−) reabsorbed in the proximal tubule?

A

H+ ions secreted into the lumen combine with filtered HCO3− to form H2CO3, which then breaks down into CO2 and H2O. CO2 diffuses back into the tubule cells, where it is converted back to HCO3− and reabsorbed.

28
Q

What enzyme is involved in the reabsorption of bicarbonate in the proximal tubule?

A

Carbonic anhydrase, specifically isoform IV in the lumen and isoform II inside the tubule cells, catalyzes the conversion of H2CO3 to CO2 and H2O.

29
Q

What types of transporters are found in the distal tubule?

A

The distal tubule contains transporters such as H+/K+-ATPase and H+-ATPase pumps in Type A intercalated cells.

30
Q

What is the function of Type A intercalated cells in the distal tubule?

A

Type A intercalated cells actively secrete H+ into the tubular lumen via H+/K+-ATPase and H+-ATPase pumps, helping to regulate acid-base balance.

31
Q

How does H+/K+-ATPase function in the distal tubule?

A

H+/K+-ATPase exchanges H+ ions from the tubule cells with K+ ions from the tubular lumen, facilitating H+ secretion and K+ reabsorption.

32
Q

How does the H+-ATPase pump work in the distal tubule?

A

The H+-ATPase pump actively transports H+ ions into the tubular lumen, contributing to the acidification of urine and maintaining systemic pH balance.

33
Q

How is bicarbonate reabsorbed in the distal tubule?

A

In the distal tubule, secreted H+ combines with filtered HCO3− to form H2CO3, which is then converted to CO2 and H2O. CO2 diffuses into the tubule cells, where it is converted back to HCO3− and reabsorbed.

34
Q

What role does carbonic anhydrase play in the distal tubule?

A

Carbonic anhydrase facilitates the conversion of H2CO3 to CO2 and H2O in the tubular lumen and the conversion of CO2 back to HCO3− in the tubule cells.

35
Q

What are the main differences in transport mechanisms between the proximal and distal tubules?

A

The proximal tubule primarily uses Na+/H+ antiporters and H+-ATPase for H+ secretion and HCO3− reabsorption, while the distal tubule relies on H+/K+-ATPase and H+-ATPase pumps in Type A intercalated cells for these processes.

36
Q

Why is the regulation of H+ secretion important in both the proximal and distal tubules?

A

Regulation of H+ secretion is crucial for maintaining acid-base balance, preventing acidosis or alkalosis, and ensuring proper reabsorption of bicarbonate.

37
Q

How do transporters in the proximal and distal tubules contribute to overall kidney function?

A

These transporters play key roles in acid-base homeostasis, electrolyte balance, and the excretion of metabolic waste products, supporting the kidney’s role in maintaining systemic homeostasis.