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Questions and Answers
What is the bond distance between the hydrogen and oxygen atoms in water?
What is the bond distance between the hydrogen and oxygen atoms in water?
What is the angle formed by the three atoms in a water molecule?
What is the angle formed by the three atoms in a water molecule?
Which atoms are bonded in a water (H2O) molecule?
Which atoms are bonded in a water (H2O) molecule?
Which statement accurately describes the structure of water?
Which statement accurately describes the structure of water?
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What defines the bond structure of a water molecule?
What defines the bond structure of a water molecule?
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What does the symbol K represent in the equilibrium expression?
What does the symbol K represent in the equilibrium expression?
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At what point in a titration curve is the pH equal to the pK?
At what point in a titration curve is the pH equal to the pK?
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What happens to the protonated forms at pH values above the pK?
What happens to the protonated forms at pH values above the pK?
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How does the strength of an acid relate to its pK value?
How does the strength of an acid relate to its pK value?
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What is indicated by the equilibrium constant expression K?
What is indicated by the equilibrium constant expression K?
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What occurs with weak acids in a basic solution?
What occurs with weak acids in a basic solution?
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How do weak bases behave in a basic solution?
How do weak bases behave in a basic solution?
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What is the result of a weak acid ionizing in a basic solution?
What is the result of a weak acid ionizing in a basic solution?
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What ions are produced when weak acids ionize?
What ions are produced when weak acids ionize?
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In what manner do weak bases behave compared to strong bases in basic solutions?
In what manner do weak bases behave compared to strong bases in basic solutions?
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What happens to the pH of a solution without a buffering mechanism when acids or alkalis are added?
What happens to the pH of a solution without a buffering mechanism when acids or alkalis are added?
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Which statement correctly describes the role of a buffering mechanism in a solution?
Which statement correctly describes the role of a buffering mechanism in a solution?
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What effect does adding acids or alkalis have on a solution that lacks a buffering mechanism?
What effect does adding acids or alkalis have on a solution that lacks a buffering mechanism?
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Why is a buffering mechanism important in chemical solutions?
Why is a buffering mechanism important in chemical solutions?
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What is the potential consequence of not having a buffering mechanism in a biological system?
What is the potential consequence of not having a buffering mechanism in a biological system?
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In a strongly basic solution, what happens to the weak acid?
In a strongly basic solution, what happens to the weak acid?
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What is the behavior of weak acids in strongly acidic solutions?
What is the behavior of weak acids in strongly acidic solutions?
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Which statement is true regarding weak acids in varying pH environments?
Which statement is true regarding weak acids in varying pH environments?
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What is the consequence of a strongly basic solution on weak acids?
What is the consequence of a strongly basic solution on weak acids?
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In which condition can weak acids not exist in a unionized form?
In which condition can weak acids not exist in a unionized form?
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At what pH does H3PO4 dissociate into H2PO4 and H+?
At what pH does H3PO4 dissociate into H2PO4 and H+?
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What is the species formed when H2PO4 dissociates at a pH of 7.2?
What is the species formed when H2PO4 dissociates at a pH of 7.2?
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Which form of phosphate exists at a pH of 12.7?
Which form of phosphate exists at a pH of 12.7?
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Which of the following statements is true regarding phosphate at cytoplasmic pH?
Which of the following statements is true regarding phosphate at cytoplasmic pH?
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What charge does the species HPO4²¯ carry?
What charge does the species HPO4²¯ carry?
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Study Notes
Course Information
- Course: Biochemistry 1
- Department/Semester: Fourth Semester
- Semester: Autumn 2024 – 2025
- Lecture: First Lecture
- Instructor: Ouida T. Khujli Abbas
Biomedical Importance of Water
- Water is the primary component of living organisms.
- Water's dipolar structure allows it to dissolve various organic and inorganic molecules through hydrogen bonding.
- Water is involved in many metabolic reactions, acting as a reactant or product.
- Water has a slight tendency to dissociate into hydroxide ions and protons.
- Bicarbonate and other buffers maintain the pH of extracellular fluid between 7.35 and 7.45.
- Acidosis (blood pH < 7.35) is caused by conditions like diabetic ketosis and lactic acidosis.
- Alkalosis (blood pH > 7.45) can result from vomiting acidic gastric contents.
Water as a Biological Solvent
- Water molecules form dipoles due to the electronegative oxygen atom pulling electrons away from hydrogen nuclei.
- This creates a partial positive charge on hydrogen and a partial negative charge on oxygen.
- Water's strong dipole and high dielectric constant enable it to dissolve numerous charged compounds (salts).
- Water molecules form hydrogen bonds with each other and with other molecules.
- This self-association of water molecules influences its physical properties (viscosity, surface tension, and boiling point).
- Hydrogen bonding allows water to dissolve many organic substances.
Water Molecules and Hydrogen Bonds
- Water molecules contain both hydrogen bonding donors and acceptors.
- Hydrogen bonding leads to the self-association of water molecules into ordered arrays.
- Hydrogen bonding significantly impacts water's physical properties.
Physiochemical Properties of Water
- Water is colorless, odorless, and tasteless.
Structure of Water Molecules
- Water molecules consist of two hydrogen atoms bonded to an oxygen atom.
- The O–H bond distance is 0.958 Å, and the angle between the three atoms is 104.5°.
- Water molecules form hydrogen bonds.
- Oxygen has partial negative charge and hydrogen has partial positive charge.
Energy of Hydrogen Bonds
- Energy of a hydrogen bond is approximately -20 kJ/mol.
- Energy of covalent bond is approximately 460 kJ/mol.
- Ice is a crystalline structure of hydrogen-bonded water molecules.
- Water molecules in ice are tetrahedrally surrounded by their nearest neighbors.
Liquid Water Density and Ice Structure
- Liquid water density is approximately 1.00 g/mL.
- Ice density is approximately 0.92 g/mL.
Structure of Liquid Water
- Liquid water structure is irregular.
- Networks of water molecules continually break and reform every 2x10-11 seconds.
Self-Ionization of Water
- Water dissociates into H+ and OH− ions.
- [H+][OH−] = 10−14 mol2/L2 at 25°C.
pH
- pH measures the hydrogen ion concentration.
- pH below 7 is acidic, above 7 is alkaline.
- Neutral pH is 7.
Acids and Bases
- Acids release protons (H+) and gain a negative charge (anion).
- Bases accept protons and gain a positive charge (cation).
Ionization of Amino Acids
- Amino acids possess both acidic (-COOH) and basic (-NH2) groups.
- Depending on the pH, amino acids can exist in various charged forms.
- The pH at which an amino acid has no net charge is called the isoelectric point (pI).
Buffers
- Buffer solutions resist changes in pH upon the addition of acids or bases.
- A weak acid and its salt (conjugate base) can act as a buffer.
- Buffers are crucial for maintaining stable pH in biological systems.
Biological Buffers
- Phosphate, bicarbonate are used as buffers in cells.
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Description
Explore the crucial role of water in biochemical processes in this quiz for Biochemistry 1. Understand how water acts as a solvent and its significance in metabolic reactions. This quiz will also cover the impact of pH levels on biological functions.
