Membrane Proteins Overview

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Questions and Answers

What happens to enzyme activity in neutral solutions?

  • Enzyme activity becomes erratic with significant fluctuations.
  • Enzyme activity remains unchanged despite variations in pH. (correct)
  • Enzyme activity can only decrease at very low or high pH levels.
  • Enzyme activity decreases significantly regardless of other factors.

How does temperature affect enzyme reactions outside their optimal range?

  • Temperature extremes can slow down reaction rates significantly. (correct)
  • Enzymes function best at any temperature, adjusting to conditions.
  • Cold temperatures always lead to denaturation of enzymes.
  • Higher temperatures enhance enzyme activity indefinitely.

What structural change in enzymes can lead to loss of function?

  • Addition of cofactors that stabilize the enzyme structure.
  • Denaturation of the enzyme's three-dimensional shape. (correct)
  • Modification of the enzyme's primary sequence.
  • Increasing the substrate concentration to excessive levels.

What is the effect of substrate concentration on the initial rate of reaction?

<p>A plateau is reached when all enzymes are saturated with substrate. (D)</p> Signup and view all the answers

How is the enzyme active site's shape affected by pH changes?

<p>Alterations in pH can change the active site's shape and decrease function. (D)</p> Signup and view all the answers

What is the main physiological process most affected in sickle cell disease?

<p>Hemoglobin structure (A)</p> Signup and view all the answers

What describes the state of free enzyme availability in a saturation scenario?

<p>All enzymes are either in a complex with substrate or leftover as free. (C)</p> Signup and view all the answers

Which amino acid is replaced in sickle cell disease due to a point mutation?

<p>Glutamic acid (D)</p> Signup and view all the answers

What typically happens to enzymes at high temperatures?

<p>They change shape and eventually denature. (C)</p> Signup and view all the answers

What specific genetic alteration causes sickle cell disease?

<p>Single base-pair substitution (D)</p> Signup and view all the answers

Which of these results from the abnormal protein formation in sickle cell disease?

<p>Formation of rigid red blood cells (D)</p> Signup and view all the answers

Which of the following correctly describes enzyme behavior at low pH?

<p>Enzymes may undergo structural changes that affect activity. (D)</p> Signup and view all the answers

In sickle cell disease, which molecule would likely demonstrate abnormal behavior in response to stress?

<p>Hemoglobin S (B)</p> Signup and view all the answers

What could be concluded from an arterial blood gas showing a pH of 7.39, PaCO2 of 27 mmHg, and HCO3 of 19 mmol/L?

<p>Partially compensated metabolic acidosis (A)</p> Signup and view all the answers

How is the mutation in sickle cell disease commonly characterized?

<p>Cytosine to thymine substitution (C)</p> Signup and view all the answers

In the context of the given pCO2 value of 68 mmHg, what pathology does this suggest?

<p>Acute respiratory acidosis (D)</p> Signup and view all the answers

What does an HCO3 level of 28 mmol/L indicate in the context of acid-base balance?

<p>Metabolic alkalosis (B)</p> Signup and view all the answers

What major symptom arises from the morphological changes in red blood cells in sickle cell disease?

<p>Increased hemolysis (C)</p> Signup and view all the answers

Which of the following describes the relationship between sickle cell disease and specific genetic polymorphisms?

<p>Identical mutations and identical phenotype (D)</p> Signup and view all the answers

How would a PaO2 of 65 mmHg be interpreted in an arterial blood gas analysis?

<p>Mild hypoxemia (A)</p> Signup and view all the answers

For a patient whose NGT is draining coffee ground secretions post-abdominal surgery, what is the likely concern?

<p>Metabolic acidosis due to gastrointestinal loss (C)</p> Signup and view all the answers

Which of the following parameters is primarily involved in diagnosing respiratory acidosis?

<p>Decreased pH and elevated PaCO2 (B)</p> Signup and view all the answers

What does a pH level of 7.3 indicate in terms of acid-base status?

<p>Metabolic acidosis (C)</p> Signup and view all the answers

When assessing a patient with a pH of 7.45, what can be inferred regarding their acid-base status?

<p>Fully compensated respiratory alkalosis (A)</p> Signup and view all the answers

What is the interpretation of a pH of 7.57 in terms of acid-base balance?

<p>Alkalosis (B)</p> Signup and view all the answers

Given a PaO2 of 85 mmHg, how would the oxygenation status of the patient be classified?

<p>Mild Hypoxemia (D)</p> Signup and view all the answers

What does a HCO3 value of 30 mmol/L suggest about the patient's acid-base status?

<p>Metabolic alkalosis (A)</p> Signup and view all the answers

If the arterial blood gas shows pCO2 of 37 mmHg, what does this imply about the respiratory status?

<p>Normal respiratory function (A)</p> Signup and view all the answers

What can be inferred from the values Na+ 140 mmol/L and Cl- 100 mmol/L?

<p>Normal serum electrolyte levels (B)</p> Signup and view all the answers

If a patient has a pH of 7.38 and a PaCO2 of 41 mmHg, what could be the acid-base disturbance?

<p>Respiratory acidosis (A)</p> Signup and view all the answers

Which equation represents the bicarbonate buffer system accurately?

<p>pH = pKa + log([HCO3-]/[0.03×PCO2]) (B)</p> Signup and view all the answers

Which condition is characterized by a pH less than 7.35?

<p>Metabolic acidosis (D)</p> Signup and view all the answers

Which type of amino acids are primarily found in the intra-membrane domain of transmembrane proteins?

<p>Hydrophobic amino acids (B)</p> Signup and view all the answers

Which of the following amino acids is likely to be found in the extracellular domain of plasma membrane proteins?

<p>Lysine (C)</p> Signup and view all the answers

What feature distinguishes polar molecules from non-polar molecules?

<p>Asymmetrical charge distribution (D)</p> Signup and view all the answers

Among the following bonds, which is known to be the least polar?

<p>C-H (C)</p> Signup and view all the answers

Which amino acids are typically found in the cytosolic domain of membrane proteins?

<p>Glutamic acid and aspartic acid (B)</p> Signup and view all the answers

What is a characteristic of hydrophobic amino acids in relation to the lipid bilayer?

<p>They cluster together within the hydrophobic core (B)</p> Signup and view all the answers

In the context of hydrogen bonding, which type of bond would exhibit the highest polarity?

<p>O-H (D)</p> Signup and view all the answers

What factor contributes most to the polarity of a covalent bond?

<p>The electronegativity difference between atoms (B)</p> Signup and view all the answers

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Study Notes

Membrane Proteins

  • Membrane proteins have three domains: extracellular, intra-membrane, and cytosolic.
  • The intra-membrane domain consists of hydrophobic amino acid sequences within the lipid bilayer.
  • Extracellular and intracellular domains contain hydrophilic amino acids.

Polar Covalent Bonds

  • The most polar covalent bonds involve H-O, N-H, O-H, or F-H due to high electronegativity differences.
  • A polar covalent bond exhibits a bond dipole, influencing molecular interactions.

Sickle Cell Disease

  • Sickle cell disease (SCD) is caused by a single base-pair mutation in the β-globin gene.
  • This mutation replaces glutamic acid with valine in the β-globin chain, leading to abnormal hemoglobin formation.
  • Sickle cell anemia is one of the most common genetic disorders linked to hemoglobin.

Enzyme Activity and pH

  • Enzyme activity is influenced by pH; deviations from optimal pH can change enzyme shape and function.
  • Hot temperatures can denature enzymes, leading to irreversible changes in the active site.

Initial Reaction Rates

  • There is a positive correlation between substrate concentration and the initial reaction rate until saturation occurs.
  • Past a certain point, all enzyme active sites are occupied, decreasing the availability of free enzymes.

Arterial Blood Gas Interpretation

  • Normal pH range is 7.35 – 7.45; values outside this indicate acidosis or alkalosis.
  • pCO2 levels determine respiratory status; elevated values suggest respiratory acidosis.
  • HCO3 values help assess metabolic status; levels outside the normal range indicate metabolic acidosis or alkalosis.

Patient Case Studies

  • A case with irritability and diarrhea in an infant resulted in ABG results displaying partially compensated metabolic acidosis.
  • A patient with coffee-ground drainage post-surgery had ABG results indicating uncompensated metabolic alkalosis.

Oxygenation Status

  • Oxygenation levels can be assessed through PaO2 measurements, indicating hypoxaemia at varying severities.

ABG Measurements

  • ABG results showing pH, PaO2, HCO3, and PaCO2 provide insight into the acid-base status of the patient.
  • Bicarbonate buffering systems play a crucial role in maintaining acid-base balance, described by the equation: pH = pKa + log([HCO3-]/[0.03×PCO2]).

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