Biology Chapter: Basic Cell Chemicals

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Questions and Answers

What is the principal fluid medium of the cell?

Water

What is the concentration of water in most cells, except for fat cells?

70% to 85%

What are the most important ions in the cell?

K+, Mg2+, PO43-, SO42-, HCO3-

What two types of proteins are found in cells?

Structural proteins and functional proteins Signup and view all the answers

What are two examples of structural proteins?

Intracellular filaments and extracellular proteins Signup and view all the answers

What are three examples of functional proteins?

Enzymes, hormones, and antibodies Signup and view all the answers

What two lipids are particularly important for cell function?

Phospholipids and cholesterol Signup and view all the answers

What is another name for triglycerides?

Neutral fat Signup and view all the answers

What is the primary function of triglycerides in fat cells?

Energy storage Signup and view all the answers

In human cells, what is the approximate percentage of carbohydrates?

About 1% of their total mass Signup and view all the answers

What is the form of carbohydrate that is stored in cells?

Glycogen Signup and view all the answers

What determines the different types of chemical bonding?

How the valence electrons are shared among the bonded atoms Signup and view all the answers

What are the two primary types of chemical bonding?

Covalent bonding Signup and view all the answers

When does pure covalent bonding occur?

When two nonmetal atoms of the same kind bind to each other Signup and view all the answers

What type of bonding occurs when two different nonmetal atoms are bonded or a nonmetal and a metal are bonded?

Polar covalent bonding Signup and view all the answers

What is the quantitative measure of a molecule's polarity called?

Dipole moment Signup and view all the answers

What happens to the valence electrons in ionic bonding?

They are completely transferred from one atom to the other atom Signup and view all the answers

When do ionic bonds occur?

Between metals and nonmetals when there is a large difference in electronegativity Signup and view all the answers

What is a hydrogen bond?

An attractive force between a hydrogen atom attached to an electronegative atom of one molecule and an electronegative atom of a different molecule Signup and view all the answers

What are the most common electronegative atoms involved in hydrogen bonding?

Oxygen, nitrogen, or fluorine Signup and view all the answers

According to the Bronsted-Lowry theory, what is an acid?

A proton (hydrogen ion) donor Signup and view all the answers

According to the Arrhenius theory, what do acids produce in solution?

Hydrogen ions Signup and view all the answers

What is the common way pH is expressed?

Negative log of the molar concentrations of hydrogen ions Signup and view all the answers

What is the pH of pure water?

7 Signup and view all the answers

What is the range of pH for acids?

Less than 7 Signup and view all the answers

How is pH measured using a pH meter?

Electrode measures H+ concentration Signup and view all the answers

What is the purpose of standardizing a pH meter?

To calibrate it before use Signup and view all the answers

What is the limitation of indicator dyes and test strips for pH measurement?

They are less precise Signup and view all the answers

Why are indicator dyes and test strips sometimes preferable for pH measurements?

They are good for field usage, measuring small volumes, or dealing with noxious samples Signup and view all the answers

How does pH affect solubility of substances?

pH affects the solubility of many substances Signup and view all the answers

How does pH affect the structure and function of proteins?

pH affects structure and function of proteins Signup and view all the answers

What is the pH range of blood plasma in healthy individuals?

7.35 to 7.45 Signup and view all the answers

What is the typical pH of gastric fluid?

2.0 Signup and view all the answers

What is the typical pH of pancreatic secretions?

8.0 Signup and view all the answers

What is the term for the amount of acid or base that can be added to a buffer without significantly changing its pH?

Buffer capacity Signup and view all the answers

What is the term for the range of pH values for which a buffer system is most effective?

Buffer range Signup and view all the answers

What are the three important buffer systems in the human body?

Protein buffer system, phosphate buffer system, and carbonic acid buffer system Signup and view all the answers

Why is histidine an important amino acid in the protein buffer system?

It acts as a weak base that can readily convert to its conjugate acid Signup and view all the answers

What is the approximate pKa of the conjugate acid of histidine?

6.0 Signup and view all the answers

Where do protein buffers occur in the body?

Both inside and outside cells Signup and view all the answers

Why is the phosphate buffer system less effective at maintaining a pH of 7?

The pKa of phosphoric acid is 2.1 Signup and view all the answers

What two forms of phosphate ions are involved in the phosphate buffer system?

H2PO4- and HPO42- Signup and view all the answers

What is the most important extracellular buffer?

The carbonic acid buffer system Signup and view all the answers

What are the primary buffering agents in blood plasma?

H2CO3 and bicarbonate ions Signup and view all the answers

Why is the carbonic acid buffer system less effective at maintaining blood pH than expected based on its pKa?

The pKa is only 6.1, below the plasma pH of 7.4 Signup and view all the answers

What is the consequence of very high concentrations of bicarbonate in blood plasma?

It can disrupt the osmotic balance between the plasma and intracellular fluids Signup and view all the answers

Why is the concentration of carbonic acid maintained at a very low level in blood plasma?

To avoid disrupting the osmotic balance Signup and view all the answers

What happens to blood pH when you breathe too fast?

The pH of blood plasma goes up Signup and view all the answers

How do proteins containing histidine can help maintain the pH of body fluids around 7?

They can act as effective buffers around a pH of 7 Signup and view all the answers

Study Notes

Basic Cell Chemicals

Cell chemistry is crucial for cellular functions
Water is the principal fluid medium in most cells (70% to 85%), except fat cells
Many cellular chemicals are dissolved in water; others are suspended
Chemical reactions occur between dissolved chemicals, or on suspended particles/membranes

Ions

Important cellular ions include K+, Mg2+, PO43-, SO42-, HCO3- and smaller quantities of Na+, Cl-, Ca2+
Extracellular and intracellular fluid ion concentrations differ
Ions are essential for cellular reactions and controlling mechanisms
Ions at cell membranes facilitate electrochemical impulse transmission in nerves and muscles

Proteins

Proteins are the most abundant substances after water, composing 10-20% cell mass
Two types:
- Structural proteins: intracellular filaments, extracellular proteins (collagen, elastin)
- Functional proteins: enzymes, hormones, antibodies

Lipids

Phospholipids and cholesterol (2% of total cell mass) are mainly insoluble in water
Form cell membranes and intracellular barriers
Some cells contain significant amounts of triglycerides (neutral fat)
Triglycerides, in fat cells, can comprise up to 95% of cell mass and serve as energy storage

Carbohydrates

Most human cells contain about 1% carbohydrates (up to 3% in muscle, occasionally 6% in liver)
Dissolved glucose is always present in the surrounding extracellular fluid
A small amount of carbohydrate is stored as glycogen (an insoluble glucose polymer)

Types of Bonding

Chemical bonding types are determined by how valence electrons are shared between atoms
Types of bonding: covalent and ionic

Covalent Bonds

Valence electrons are shared as pairs between bonded atoms
Pure covalent bonds occur between nonmetal atoms of the same kind
Polar covalent bonds involve nonmetal atoms of different kinds, or nonmetals and metals, exhibiting a mixture of covalent and ionic bonding

Polar Covalent Bonding

Involved in different nonmetal atoms or nonmetals and metals
A mixture of covalent and ionic bonding

Polar Molecules

Polar molecules have an overall dipole (can be represented by a dipole arrow pointing to the more electronegative end)
A molecule's polarity is quantified by its dipole moment

Ionic Bonding

Valence electrons are completely transferred from one atom to the other
Occurs between metals and nonmetals when there's a large difference in electronegativity

Hydrogen Bonds

Attractive force between a hydrogen atom attached to an electronegative atom in one molecule, and an electronegative atom of a different molecule
Usually, the electronegative atom is oxygen, nitrogen, or fluorine, carrying a partial negative charge

Acids and Bases

Brønsted-Lowry theory:
- Acid: proton (hydrogen ion) donor
- Base: proton (hydrogen ion) acceptor
Arrhenius theory:
- Acid: a substance producing hydrogen ions in solution
- Base: a substance producing hydroxide ions in solution
Neutralization occurs when hydrogen and hydroxide ions react to form water

pH

pH is the negative logarithm of hydrogen (actually hydronium) ion molar concentration
Pure water has pH 7
Acids have high [H+] and low pH
Bases have low [H+] and high pH

pH Measurement

pH meter: measures H+ concentration; must be standardized before use
Indicator dyes/test strips: Less precise, suitable for field usage, small volume, or noxious samples

pH in Biology

pH influences many substances' solubility
Affects protein structure and function
Many cells/organisms survive within a specific pH range; blood pH 7.35–7.45 is crucial for optimal functioning

Buffer Solutions

Buffer solutions resist pH changes when strong acid or base is added
Consist of a weak acid and its conjugate base
Example: acetic acid and sodium acetate, ammonium chloride and ammonia
pH of a buffer solution is approximately equal to the pKa of the weak acid

Buffering Action

Le Chatelier's Principle: shift in equilibrium in response to changes
If acid is added, the reaction shifts to the left, increasing [HA] and decreasing [A-]
If base is added, the reaction shifts to the right, decreasing [HA] and increasing [A-]
Buffer capacity: amount of acid/base a buffer can absorb without significant pH change
Buffer range: pH values where the buffer solution is most effective (usually ±1 pH unit of pKa)

Important Buffers in the Human Body

Protein buffer system:
- Proteins are constructed from amino acids
- Histidine, a weak base, readily transitions to its conjugate acid
- Protein with histidine can be effective buffers around pH 7
Phosphate buffer system:
- Phosphate ions (H2PO4⁻ and HPO4²⁻) form effective buffers near pH 7.2
Carbonic acid buffer system:
- H₂CO₃ and bicarbonate ions act as primary buffers in blood plasma, maintaining a pH of 7.4

Tutorial Questions (provided)

These questions are about the phosphate buffer system.
The questions are focused on the contents of the slides. Understanding the material is important!

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Description

Explore the fundamental chemicals that compose cells, including the roles of water, ions, proteins, and lipids. This quiz will test your understanding of the chemical components vital for cellular functions and reactions. Get ready to delve into the intricacies of cell chemistry!